WorldWideScience

Sample records for bistable reflective cholesteric

  1. Flexible Bistable Cholesteric Reflective Displays

    Science.gov (United States)

    Yang, Deng-Ke

    2006-03-01

    Cholesteric liquid crystals (ChLCs) exhibit two stable states at zero field condition-the reflecting planar state and the nonreflecting focal conic state. ChLCs are an excellent candidate for inexpensive and rugged electronic books and papers. This paper will review the display cell structure,materials and drive schemes for flexible bistable cholesteric (Ch) reflective displays.

  2. Bistable cholesteric liquid crystal light shutter with multielectrode driving.

    Science.gov (United States)

    Li, Cheng-Chang; Tseng, Heng-Yi; Pai, Tsung-Wei; Wu, Yu-Ching; Hsu, Wen-Hao; Jau, Hung-Chang; Chen, Chun-Wei; Lin, Tsung-Hsien

    2014-08-01

    An electrically activated bistable light shutter that exploits polymer-stabilized cholesteric liquid crystal film was developed. Under double-sided three-terminal electrode driving, the device can be bistable and switched between focal conic and homeotropic textures with a uniform in-plane and vertical electrical field. The transparent state with a transmittance of 80% and the opaque/scattering state with a transmittance of 13% can be realized without any optical compensation film, and each can be simply switched to the other by applying a pulse voltage. Also, gray-scale selection can be performed by varying the applied voltage. The designed energy-saving bistable light shutter can be utilized to preserve privacy and control illumination and the flow of energy.

  3. Bistable Reflective Etalon (BRET)

    National Research Council Canada - National Science Library

    Shellenbarger, Zane

    2003-01-01

    This project designed, fabricated, and characterized normal-incidence etalon structures at 1550 nm wavelength operation for application, as bistable elements, to photonic analog-to-digital conversion...

  4. Cholesteric Liquid Crystal Based Reflex Color Reflective Displays

    Science.gov (United States)

    Khan, Asad

    2012-02-01

    Bistable color cholesteric liquid crystal displays are unique LCDs that exhibit high reflectivity, good contrast, extremely low power operation, and are amenable to versatile roll-to-roll manufacturing. The display technology, now branded as Reflex has been in commercialized products since 1996. It has been the subject of extensive research and development globally by a variety of parties in both academic and industrial settings. Today, the display technology is in volume production for applications such as dedicated eWriters (Boogie Board), full color electronic skins (eSkin), and displays for smart cards. The flexibility comes from polymerization induced phase separation using unique materials unparalleled in any other display technology. The blend of monomers, polymers, cross linkers, and other components along with nematic liquid crystals and chiral dopants is created and processed in such ways so as to enable highly efficient manufactrable displays using ultra thin plastic substrates -- often as thin as 50μm. Other significant aspects include full color by stacking or spatial separation, night vision capability, ultra high resolution, as well as active matrix capabilities. Of particular note is the stacking approach of Reflex based displays to show full color. This approach for reflective color displays is unique to this technology. Owing to high transparency in wavelength bands outside the selective reflection band, three primarily color layers can be stacked on top of each other and reflect without interfering with other layers. This highly surprising architecture enables the highest reflectivity of any other reflective electronic color display technology. The optics, architecture, electro-topics, and process techniques will be discussed. This presentation will focus on the physics of the core technology and color, it's evolution from rigid glass based displays to flexible displays, development of products from the paradigm shifting concepts to consumer

  5. Prize for Industrial Applications of Physics: Reflective Cholesteric Liquid Crystals - Innovations in Materials, Display Technology, and Commercialization

    Science.gov (United States)

    Khan, Asad

    Reflective Cholesteric Liquid Crystals have been the subject of much research, development, and commercialization - in display technology as well as other embodiments, such as sensors, privacy films, etc. The liquid Crystal Institute (LCI) at Kent State University (KSU) served as a hot bed of much of the research and development in this field in the early 1990's. From here, the reflective technology was licensed to Kent Displays (KDI) to further develop and commercialize. The 90's saw some development in flexible technologies, drive scheme, display design, as well as materials. The early part of the century took a turn with a strong effort in encapsulation based flexible display development. In 2006, KDI engineers and technologists started firming up ambitious plans for the world's first roll-to-roll manufacturing line for bistable cholesteric displays. In 2009, this became a reality! In early 2010, the first eWriter product was launched into the consumer market under the brand Boogie Board®. Within months, this became a success forcing the rapid development of the manufacturing process for the flexible displays. Today, the company has two manufacturing lines, 24 hour roll-to-roll production of flexible displays, millions of Boogie Board products in the global market place, and a growing OEM business in the Boogie Board technology. KDI continues to do basic research, development, and exploration in the bistable display field. It also has had to become an expert in the supply chain management of the unique raw materials needed for flexible display manufacturing, while still managing global operations with sales offices in several continents and a growing and diversified group of individuals. In this presentation, we will present the story, research, development, technology, and latest trends in bistable cholesteric liquid crystal materials with a particular emphasis on the eWriter technology and market.

  6. Blue Shifting Tuning of the Selective Reflection of Polymer Stabilized Cholesteric Liquid Crystals (Postprint)

    Science.gov (United States)

    2017-08-08

    crystal (MLC-2079, Merck). The polymer stabi- lizing network was formed within the samples by photoinitiated polymerization with 50–700 mW cm2 of 365...AFRL-RX-WP-JA-2017-0347 BLUE-SHIFTING TUNING OF THE SELECTIVE REFLECTION OF POLYMER STABILIZED CHOLESTERIC LIQUID CRYSTALS (POSTPRINT...BLUE-SHIFTING TUNING OF THE SELECTIVE REFLECTION OF POLYMER STABILIZED CHOLESTERIC LIQUID CRYSTALS (POSTPRINT) 5a. CONTRACT NUMBER FA8650-16-F

  7. Recent advances in flexible low power cholesteric LCDs

    Science.gov (United States)

    Khan, Asad; Shiyanovskaya, Irina; Montbach, Erica; Schneider, Tod; Nicholson, Forrest; Miller, Nick; Marhefka, Duane; Ernst, Todd; Doane, J. W.

    2006-05-01

    Bistable reflective cholesteric displays are a liquid crystal display technology developed to fill a market need for very low power displays. Their unique look, high reflectivity, bistability, and simple structure make them an ideal flat panel display choice for handheld or other portable devices where small lightweight batteries with long lifetimes are important. Applications ranging from low resolution large signs to ultra high resolution electronic books can utilize cholesteric displays to not only benefit from the numerous features, but also create enabling features that other flat panel display technologies cannot. Flexible displays are the focus of attention of numerous research groups and corporations worldwide. Cholesteric displays have been demonstrated to be highly amenable to flexible substrates. This paper will review recent advances in flexible cholesteric displays including both phase separation and emulsification approaches to encapsulation. Both approaches provide unique benefits to various aspects of manufacturability, processes, flexibility, and conformability.

  8. Black-on-white polymer-stabilized cholesteric formulations

    Science.gov (United States)

    West, John L.; Magyar, Gregory R.; Francl, James J.; Nixon, Christine M.

    1995-08-01

    Recent research by Doane, Yang, and Chien demonstrated the use of cholesteric liquid crystals in multiplexed, high resolution, reflective diplays. These materials utilize the bistability of the cholesteric planar and focal conic states for displays with a colored image on a black background. Many commercial applications of these materials, such as electronic books and newspapers, portable faxes and personal data assistants, require, or at least prefer, black-on- white images. We report on relatively high polymer content (equalsV 20% by weight) dispersions of cholesteric liquid crystals that produce a white, reflecting, planar state. The polymer network appears to form cholesteric domains with varying pitch lengths resulting in planar states that reflect in the red, green, and blue portions of the spectrum. Utilizing a black absorbing layer behind a display using these materials offers white images on a black background, or vice-versa.

  9. Low-power cholesteric LCDs and electronic books

    Science.gov (United States)

    Khan, Asad A.; Huang, Xiao-Yang; Doane, Joseph W.

    2004-09-01

    We discuss the state of the art of the bistable reflective cholesteric liquid crystal display technology. Numerous applications from low resolutions signs, to medium resolution instrumentation type displays, and high resolution electronic books are discussed. Different modes of the technology are discussed as being viable for the respective display applications. Special emphasis is paid to electronic book applications.

  10. High-reflective colorful films fabricated by all-solid multi-layer cholesteric structures

    Science.gov (United States)

    Li, Y.; Luo, D.

    2018-02-01

    We demonstrate all-solid-state film with high-reflectivity based on cholesteric template. The adhesive (NOA81) is both filler and an adhesive, which can be avoids interfacial losses. The reflected right- and left-circularly polarized light has been developed by roll-to-roll method, and the reflectance of the films is more than 78%. Here, the all-solid film was used in distribute feedback laser with dye-doped. In addition, this films also used in include flexible reflective display, color pixels in digital photographs, printing and colored cladding of variety of objects.

  11. Bistability By Self-Reflection In A Saturable Absorber

    Science.gov (United States)

    Roso-Franco, Luis

    1987-01-01

    Propagation of laser light through a saturable absorber is theoretically studied. Computed steady state solutions of the Maxwell equations describing the unidimensional propagation of a plane monochromatic wave without introducing the slowly-varying envelope approximation are presented showing how saturation effects can influence the absorption of the field. At a certain range of refractive index and extintion coefficients, computed solutions display a very susprising behaviour, and a self-reflected wave appears inside the absorber. This can be useful for a new kind of biestable device, similar to a standard bistable cavity but with the back mirror self-induced by the light.

  12. Observation of two regions of selective light reflection from a thin film of a cholesteric liquid crystal

    International Nuclear Information System (INIS)

    Alaverdyan, R B; Dadalyan, T K; Chilingaryan, Yurii S

    2013-01-01

    Two regions of selective light reflection (in the short- and long- wavelength parts of the visible spectrum) from a thin film of a cholesteric liquid crystal (CLC), consisting of the mixture of two CLCs with opposite chirality and a nematic liquid crystal, are experimentally found for the first time. The spectral position of the reflection regions and the separation between them varies depending on the CLC composition and the temperature. The long-wavelength region of reflection corresponds to the region of Bragg reflection from the CLC helix, while the short-wavelength region is probably due to the defects in the structure of the CLC film. (letters)

  13. Research progress of cholesteric liquid crystals with broadband reflection characteristics in application of intelligent optical modulation materials

    International Nuclear Information System (INIS)

    Zhang Lan-Ying; Gao Yan-Zi; Song Ping; Yuan Xiao; He Bao-Feng; Yang Huai; Wu Xiao-Juan; Chen Xing-Wu; Hu Wang; Guo Ren-Wei; Ding Hang-Jun; Xiao Jiu-Mei

    2016-01-01

    Cholesteric liquid crystals (CLCs) have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship. Nowadays, by the virtue of building the self-organized nanostructures with pitch gradient or non-uniform pitch distribution, extensive work has already been performed to obtain CLC films with a broad reflection band. Based on authors’ many years’ research experience, this critical review systematically summarizes the physical and optical background of the CLCs with broadband reflection characteristics, methods to obtain broadband reflection of CLCs, as well as the application in the field of intelligent optical modulation materials. Combined with the research status and the advantages in the field, the important basic and applied scientific problems in the research direction are also introduced. (topical review)

  14. Thermally controllable reflective characteristics from rupture and self-assembly of hydrogen bonds in cholesteric liquid crystals.

    Science.gov (United States)

    Hu, Wang; Cao, Hui; Song, Li; Zhao, Haiyan; Li, Sijin; Yang, Zhou; Yang, Huai

    2009-10-22

    A cholesteric liquid crystal (Ch-LC) composite, made of a series of cholesteryl esters, a nematic LC, and a hydrogen bond (H-bond) chiral dopant (HCD), was prepared and filled into a planar treated cell. When the cell was heated, the selective reflection of the cell exhibited an unusual blue shift. One of the reasonable mechanisms was that the helical twisting power (HTP) value of cholesteryl esters increased with an increasing temperature. The other one was that the H-bonds of HCD were ruptured when the temperature was above 60.0 degrees C and HCD was split into two kinds of new chiral dopants, which made the HTP value of the chiral dopants change a lot, thus changing the pitch length of the composite greatly. On the basis of this mechanism, a novel thermally controllable reflective color paper could be achieved.

  15. Bistable enhanced total reflection in Kretschmann configuration containing a saturable gain medium.

    Science.gov (United States)

    Zhou, Haichun; Guo, Jie; Xu, Kun; Li, Zhe; Tang, Junqi; Man, Shiqing

    2018-03-05

    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. Analogous results can also be obtained in an inhomogeneously broadened (inHB) gain medium, while the two switch thresholds and the width of optical bistability hysteresis in an inHB gain medium are significantly different from those in a HB gain medium.

  16. Wetting of cholesteric liquid crystals.

    Science.gov (United States)

    Silvestre, Nuno M; Figueirinhas Pereira, Maria Carolina; Bernardino, Nelson R; Telo da Gama, Margarida M

    2016-02-01

    We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted, the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal.

  17. UP-DOWN cortical dynamics reflect state transitions in a bistable network.

    Science.gov (United States)

    Jercog, Daniel; Roxin, Alex; Barthó, Peter; Luczak, Artur; Compte, Albert; de la Rocha, Jaime

    2017-08-04

    In the idling brain, neuronal circuits transition between periods of sustained firing (UP state) and quiescence (DOWN state), a pattern the mechanisms of which remain unclear. Here we analyzed spontaneous cortical population activity from anesthetized rats and found that UP and DOWN durations were highly variable and that population rates showed no significant decay during UP periods. We built a network rate model with excitatory (E) and inhibitory (I) populations exhibiting a novel bistable regime between a quiescent and an inhibition-stabilized state of arbitrarily low rate. Fluctuations triggered state transitions, while adaptation in E cells paradoxically caused a marginal decay of E-rate but a marked decay of I-rate in UP periods, a prediction that we validated experimentally. A spiking network implementation further predicted that DOWN-to-UP transitions must be caused by synchronous high-amplitude events. Our findings provide evidence of bistable cortical networks that exhibit non-rhythmic state transitions when the brain rests.

  18. Modeling texture transitions in cholesteric liquid crystal droplets

    Science.gov (United States)

    Selinger, Robin; Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Konya, Andrew

    2012-02-01

    Cholesteric liquid crystals can be switched reversibly between planar and focal-conic textures, a property enabling their application in bistable displays, liquid crystal writing tablets, e-books, and color switching ``e-skins.'' To explore voltage-pulse induced switching in cholesteric droplets, we perform simulation studies of director dynamics in three dimensions. Electrostatics calculations are solved at each time step using an iterative relaxation method. We demonstrate that as expected, a low amplitude pulse drives the transition from planar to focal conic, while a high amplitude pulse drives the transition from focal conic back to the planar state. We use the model to explore the effects of droplet shape, aspect ratio, and anchoring conditions, with the goal of minimizing both response time and energy consumption.

  19. UV durable colour pigment doped SmA liquid crystal composites for outdoor trans-reflective bi-stable displays

    Science.gov (United States)

    Xu, H.; Davey, A. B.; Crossland, W. A.; Chu, D. P.

    2012-10-01

    High brightness trans-reflective bi-stable displays based on smectic A (SmA) liquid crystals (LCs) can have nearly perfect transparency in the clear state and very high reflection in the scattered state. Because the LC material in use is stable under UV radiation, this kind of displays can stand for strong day-light and therefore be ideal for outdoor applications from e-books to public signage and advertisement. However, the colour application has been limited because the traditional colourants in use are conventional dyes which are lack of UV stability and that their colours are easily photo bleached. Here we present a colour SmA display demonstrator using pigments as colourant. Mixing pigments with SmA LCs and maintain the desirable optical switching performance is not straightforward. We show here how it can be done, including how to obtain fine sized pigment nano-particles, the effects of particle size and size distribution on the display performance. Our optimized pigments/SmA compositions can be driven by a low frequency waveform (~101Hz) to a scattered state to exhibit colour while by a high frequency waveform (~103Hz) to a cleared state showing no colour. Finally, we will present its excellent UV life-time (at least <7.2 years) in comparison with that of dye composition (~2.4 years). The complex interaction of pigment nano-particles with LC molecules and the resulting effects on the LC electro-optical performances are still to be fully understood. We hope this work will not only demonstrate a new and practical approach for outdoor reflective colour displays but also provide a new material system for fundamental liquid crystal colloid research work.

  20. Deuterium NMR, induced and intrinsic cholesteric lyomesophases

    International Nuclear Information System (INIS)

    Alcantara, M.R.

    1982-01-01

    Induced and intrinsic cholesteric lyotropic mesophases were studied. Induced cholesteric lyomesophases based on potassium laurate (KL) system, with small amounts of cholesterol added, were studied by deuterium NMR and by polarizing microscopy. Order profiles obtained from deuterium NMR of KL perdenderated chains in both induced cholesteric and normal mesophases were compared. The intrinsic cholesteric lyotropic mesophases were based on the amphiphile potassium N-lauroyl serinate (KLNS) in the resolved levo form. The study of the type I intrinsic cholesteric mesophase was made by optical microscopy under polarized light and the type II intrinsic cholesteric lyomesophase was characterized by deuterium NMR. The new texture was explained by the use of the theory of disclinations developed for thermotropic liquid crystals, specially for cholesteric type. (M.J.C.) [pt

  1. Magnetic Nanoparticle-Assisted Tunable Optical Patterns from Spherical Cholesteric Liquid Crystal Bragg Reflectors

    OpenAIRE

    Lin, Yali; Yang, Yujie; Shan, Yuwei; Gong, Lingli; Chen, Jingzhi; Li, Sensen; Chen, Lujian

    2017-01-01

    Cholesteric liquid crystals (CLCs) exhibit selective Bragg reflections of circularly polarized (CP) light owing to their spontaneous self-assembly abilities into periodic helical structures. Photonic cross-communication patterns could be generated toward potential security applications by spherical cholesteric liquid crystal (CLC) structures. To endow these optical patterns with tunability, we fabricated spherical CLC Bragg reflectors in the shape of microshells by glass-capillary microfluidi...

  2. Optical monitoring of gases with cholesteric liquid crystals.

    Science.gov (United States)

    Han, Yang; Pacheco, Katherine; Bastiaansen, Cees W M; Broer, Dirk J; Sijbesma, Rint P

    2010-03-10

    A new approach to optical monitors for gases is introduced using cholesteric liquid crystals doped with reactive chiral compounds. The approach is based on cholesteric pitch length changes caused by a change in helical twisting power (HTP) of the chiral dopants upon reaction with the analyte. The concept is demonstrated for monitoring carbon dioxide via reversible carbamate formation and for oxygen using the irreversible oxidation of a chiral dithiol to a disulfide. Monitoring of CO(2) was achieved by doping a commercial cholesteric liquid crystalline mixture (E7) with 1.6% mol of the 1:1 complex of an optically pure diamine with a TADDOL derivative. Upon exposure to carbon dioxide, the reflection band of a thin film of the mixture shifted from 637 to 495 nm as a consequence of dissociation of the complex after carbamate formation of the diamine. An O(2) monitor was obtained by doping E7 with a chiral binaphthyl dithiol derivative and a nonresponsive codopant. The reflection band of the oxygen monitor film changed from 542 to 600 nm, due to the conformational change accompanying oxidation of the dithiol to disulfide. These monitoring mechanisms hold promise for application in smart packaging, where carbon dioxide and oxygen are of special interest because of their roles in food preservation.

  3. Controlling chirality with helix inversion in cholesteric liquid crystals

    NARCIS (Netherlands)

    Katsonis, Nathalie Hélène; Lacaze, E.; Ferrarini, A.

    2012-01-01

    The helical organization of cholesteric liquid crystals is omnipresent in living matter. Achieving control over the structure of the cholesteric helix consequently holds great potential for developing stimuli-responsive materials matching the level of sophistication of biological systems. In

  4. Volume phase transitions of cholesteric liquid crystalline gels.

    Science.gov (United States)

    Matsuyama, Akihiko

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  5. Volume phase transitions of cholesteric liquid crystalline gels

    Energy Technology Data Exchange (ETDEWEB)

    Matsuyama, Akihiko, E-mail: matuyama@bio.kyutech.ac.jp [Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502 (Japan)

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  6. Bistable perception modeled as competing stochastic integrations at two levels.

    Science.gov (United States)

    Gigante, Guido; Mattia, Maurizio; Braun, Jochen; Del Giudice, Paolo

    2009-07-01

    We propose a novel explanation for bistable perception, namely, the collective dynamics of multiple neural populations that are individually meta-stable. Distributed representations of sensory input and of perceptual state build gradually through noise-driven transitions in these populations, until the competition between alternative representations is resolved by a threshold mechanism. The perpetual repetition of this collective race to threshold renders perception bistable. This collective dynamics - which is largely uncoupled from the time-scales that govern individual populations or neurons - explains many hitherto puzzling observations about bistable perception: the wide range of mean alternation rates exhibited by bistable phenomena, the consistent variability of successive dominance periods, and the stabilizing effect of past perceptual states. It also predicts a number of previously unsuspected relationships between observable quantities characterizing bistable perception. We conclude that bistable perception reflects the collective nature of neural decision making rather than properties of individual populations or neurons.

  7. Alternative generation of well-aligned uniform lying helix texture in a cholesteric liquid crystal cell

    Directory of Open Access Journals (Sweden)

    Chia-Hua Yu

    2017-10-01

    Full Text Available This work demonstrates a simple approach for obtaining a well-aligned uniform lying helix (ULH texture and a tri-bistable feature at ambient temperature in a typical 90°-twisted cell filled with a short-pitch cholesteric liquid crystal. This ULH texture is obtained at room temperature from initially field-induced helix-free homeotropic state by gradually decreasing the applied voltage. Depending on the way and rate of reducing the voltage, three stable states (i.e., Grandjean planar, focal conic, and ULH are generated and switching between any two of them is realized. Moreover, the electrical operation of the cell in the ULH state enables the tunability in phase retardation via the deformation of the ULH. The observations made in this work may be useful for applications such as tunable phase modulators and energy-efficient photonic devices.

  8. GABA shapes the dynamics of bistable perception.

    Science.gov (United States)

    van Loon, Anouk M; Knapen, Tomas; Scholte, H Steven; St John-Saaltink, Elexa; Donner, Tobias H; Lamme, Victor A F

    2013-05-06

    Sometimes, perception fluctuates spontaneously between two distinct interpretations of a constant sensory input. These bistable perceptual phenomena provide a unique window into the neural mechanisms that create the contents of conscious perception. Models of bistable perception posit that mutual inhibition between stimulus-selective neural populations in visual cortex plays a key role in these spontaneous perceptual fluctuations. However, a direct link between neural inhibition and bistable perception has not yet been established experimentally. Here, we link perceptual dynamics in three distinct bistable visual illusions (binocular rivalry, motion-induced blindness, and structure from motion) to measurements of gamma-aminobutyric acid (GABA) concentrations in human visual cortex (as measured with magnetic resonance spectroscopy) and to pharmacological stimulation of the GABAA receptor by means of lorazepam. As predicted by a model of neural interactions underlying bistability, both higher GABA concentrations in visual cortex and lorazepam administration induced slower perceptual dynamics, as reflected in a reduced number of perceptual switches and a lengthening of percept durations. Thus, we show that GABA, the main inhibitory neurotransmitter, shapes the dynamics of bistable perception. These results pave the way for future studies into the competitive neural interactions across the visual cortical hierarchy that elicit conscious perception. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Controlling the color of cholesteric liquid-crystalline films by photoirradiation of a chiroptical molecular switch used as dopant

    NARCIS (Netherlands)

    van Delden, RA; Huck, NPM; Feringa, BL; Delden, Richard A. van; Gelder, Marc B. van; Huck, Nina P.M.

    Using thin films of a cholesteric mixture of acrylates 2 and 3 doped with the chiroptical molecular switch (M)-trans-1, photo-control of the reflection color between red and green is possible. This doped liquid-crystal (LC) film can be used for photoinduced writing, color reading, and photoinduced

  10. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    International Nuclear Information System (INIS)

    Middha, Manju; Kumar, Rishi; Raina, K. K.

    2014-01-01

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence

  11. Density of photonic states in cholesteric liquid crystals

    Science.gov (United States)

    Dolganov, P. V.

    2015-04-01

    Density of photonic states ρ (ω ) , group vg, and phase vph velocity of light, and the dispersion relation between wave vector k , and frequency ω (k ) were determined in a cholesteric photonic crystal. A highly sensitive method (measurement of rotation of the plane of polarization of light) was used to determine ρ (ω ) in samples of different quality. In high-quality samples a drastic increase in ρ (ω ) near the boundaries of the stop band and oscillations related to Pendellösung beatings are observed. In low-quality samples photonic properties are strongly modified. The maximal value of ρ (ω ) is substantially smaller, and density of photonic states increases near the selective reflection band without oscillations in ρ (ω ) . Peculiarities of ρ (ω ) , vg, and ω (k ) are discussed. Comparison of the experimental results with theory was performed.

  12. Hybrid optoelectronic device with multiple bistable outputs

    Energy Technology Data Exchange (ETDEWEB)

    Costazo-Caso, Pablo A; Jin Yiye; Gelh, Michael; Granieri, Sergio; Siahmakoun, Azad, E-mail: pcostanzo@ing.unlp.edu.are, E-mail: granieri@rose-hulma.edu, E-mail: siahmako@rose-hulma.edu [Department of Physics and Optical Engineering, Rose-Hulman Institute of Technology, 5500 Wabash Avenue, Terre Haute, IN 47803 (United States)

    2011-01-01

    Optoelectronic circuits which exhibit optical and electrical bistability with hysteresis behavior are proposed and experimentally demonstrated. The systems are based on semiconductor optical amplifiers (SOA), bipolar junction transistors (BJT), PIN photodiodes (PD) and laser diodes externally modulated with integrated electro-absorption modulators (LD-EAM). The device operates based on two independent phenomena leading to both electrical bistability and optical bistability. The electrical bistability is due to the series connection of two p-i-n structures (SOA, BJT, PD or LD) in reverse bias. The optical bistability is consequence of the quantum confined Stark effect (QCSE) in the multi-quantum well (MQW) structure in the intrinsic region of the device. This effect produces the optical modulation of the transmitted light through the SOA (or reflected from the PD). Finally, because the optical transmission of the SOA (in reverse bias) and the reflected light from the PD are so small, a LD-EAM modulated by the voltage across these devices are employed to obtain a higher output optical power. Experiments show that the maximum switching frequency is in MHz range and the rise/fall times lower than 1 us. The temporal response is mainly limited by the electrical capacitance of the devices and the parasitic inductances of the connecting wires. The effects of these components can be reduced in current integration technologies.

  13. Rotational reorganization of doped cholesteric liquid crystalline films

    NARCIS (Netherlands)

    Eelkema, R.; M. Pollard, M.; Katsonis, N.; Vicario, J.; J. Broer, D.; Feringa, B.L.

    2006-01-01

    In this paper an unprecedented rotational reorganization of cholesteric liquid crystalline films is described. This rotational reorganization results from the conversion of a chiral molecular motor dopant to an isomer with a different helical twisting power, leading to a change in the cholesteric

  14. Optical monitoring of gases with cholesteric liquid crystals

    NARCIS (Netherlands)

    Han, Y.; Pacheco Morillo, K.B.; Bastiaansen, C.W.M.; Broer, D.J.; Sijbesma, R.P.

    2010-01-01

    A new approach to optical monitors for gases is introduced using cholesteric liquid crystals doped with reactive chiral compounds. The approach is based on cholesteric pitch length changes caused by a change in helical twisting power (HTP) of the chiral dopants upon reaction with the analyte. The

  15. Optical thermal sensor based on cholesteric film refilled with mixture of toluene and ethanol.

    Science.gov (United States)

    Li, Yong; Liu, Yanjun; Luo, Dan

    2017-10-16

    We demonstrate an optical thermal sensor based on cholesteric film refilled with mixture of toluene and ethanol. The thermal response mechanism is mainly based on the thermal expansion effect induce by toluene, where the ethanol is used for refractive index adjustment to determine the initial refection band position of cholesteric film. The ethanol-toluene mixture was used to adjust the color tunability with the temperature in relation with the habits of people (blue as cold, green as safe and red as hot). A broad temperature range of 86 °C and highly sensitivity of 1.79 nm/ °C are achieved in proposed thermal sensor, where the reflective color red-shifts from blue to red when environmental temperature increases from -6 °C to 80 °C. This battery-free thermal sensor possesses features including simple fabrication, low-cost, and broad temperature sensing range, showing potential application in scientific research and industry.

  16. Helical twisting in nemato-cholesteric systems based on cholesterol derivatives and photosensitive azoxy compounds

    Energy Technology Data Exchange (ETDEWEB)

    Serbina, M. I.; Kasian, N. A.; Lisetski, L. N., E-mail: lisetski@isma.kharkov.ua [NAS of Ukraine, Institute for Scintillation Materials, STC ' Institute for Single Crystals' (Ukraine)

    2013-01-15

    For cholesteric liquid crystal systems containing photosensitive nematic ZhK-440 and a mixture of cholesterol derivatives, changes in helical twisting induced by UV radiation were studied. The UV-induced shift of selective reflection maximum {lambda}{sub max} was shown to depend upon concentration of the nematic component. For low concentrations of ZhK-440, {lambda}{sub max} increases, which correlates with corresponding changes with increasing temperature. For higher concentrations, {lambda}{sub max} decreases, regardless of the temperature behavior of the system. A theoretical description of the available experimental data is proposed on the basis of development of molecular models of helical twisting, including an assumed possibility of ordered orientation of short molecular axes of cis-isomers formed as a result of UV irradiation, which is determined by the sense of the cholesteric helix already present in the system.

  17. Smart windows based on cholesteric liquid crystals (Conference Presentation)

    Science.gov (United States)

    Khandelwal, Hitesh; Debije, Michael G.; Schenning, Albert P. H. J.

    2017-02-01

    With increase in global warming, use of active cooling and heating devices are continuously increasing to maintain interior temperature of built environment, greenhouses and cars. To reduce the consumption of tremendous amount of energy on cooling and heating devices we need an improved control of transparent features (i.e. windows). In this respect, smart window which is capable for reflecting solar infrared energy without interfering with the visible light would be very attractive. Most of the technologies developed so far are to control the visible light. These technologies block visual contact to the outside world which cause negative effects on human health. An appealing method to selectively control infrared transmission is via utilizing the reflection properties of cholesteric liquid crystals. In our research, we have fabricated a smart window which is capable of reflecting different amount of solar infrared energy depending on the specific climate conditions. The reflection bandwidth can be tuned from 120 nm to 1100 nm in the infrared region without interfering with the visible solar radiations. Calculations reveal that between 8% and 45% of incident solar infrared light can be reflected with a single cell. Simulation studies predicted that more than 12% of the energy spent on heating, cooling and lighting in the built environment can be saved by using the fabricated smart window compared to standard double glazing window.

  18. About zone structure of a stack of a cholesteric liquid crystal and isotropic medium layers

    International Nuclear Information System (INIS)

    Gevorgyan, A H; Harutyunyan, E M; Matinyan, G K; Harutyunyan, M Z

    2014-01-01

    The optical properties of a stack of metamaterial-based cholesteric liquid crystal (CLC) layers and isotropic medium layers are investigated. CLCs with two types of chiral nihility are defined. The peculiarities of the reflection spectra of this system are investigated and it is shown that the reflection spectra of the stacks of CLC layers of these two types differ from each other. The influence of: the CLC sublayer thicknesses; incidence angle; local dielectric (magnetic) anisotropy of the CLC layers; refraction indices and thicknesses of the isotropic media layers on the reflection spectra and other optical characteristics of the system is investigated.

  19. New developments in flexible cholesteric liquid crystal displays

    Science.gov (United States)

    Schneider, Tod; Davis, Donald J.; Franklin, Sean; Venkataraman, Nithya; McDaniel, Diaz; Nicholson, Forrest; Montbach, Erica; Khan, Asad; Doane, J. William

    2007-02-01

    Flexible Cholesteric liquid crystal displays have been rapidly maturing into a strong contender in the flexible display market. Encapsulation of the Cholesteric liquid crystal permits the use of flexible plastic substrates and roll-to-roll production. Recent advances include ultra-thin displays, laser-cut segmented displays of variable geometry, and smart card applications. Exciting technologies such as simultaneous laser-edge sealing and singulation enable high volume production, excellent quality control and non-traditional display geometries and formats.

  20. Nonsingular walls in plane cholesteric layers

    International Nuclear Information System (INIS)

    Belyakov, V A; Osipov, M A; Stewart, I W

    2006-01-01

    The structure of a straight interface (wall) between regions with differing values of the pitch in planar cholesteric layers with finite strength of the surface anchoring is investigated theoretically. It is found that the shape and strength of the anchoring potential influences essentially the structure of the wall and a motionless wall between thermodynamically stable regions without a singularity in the director distribution in the layer can exist for sufficiently weak anchoring only. More specifically, for the existence of such a wall the dimensionless parameter S d = K 22 /Wd (where W is the depth of the anchoring potential, K 22 is the elastic twist modulus and d is the layer thickness) should exceed its critical value, which is dependent on the shape of the anchoring potential. General equations describing the director distribution in the wall are presented. Detailed analysis of these equations is carried out for the case of infinitely strong anchoring at one surface and finite anchoring strength at the second layer surface. It is shown that the wall width L is directly dependent upon the shape and strength of the anchoring potential and that its estimate ranges from d to (dL p ) 1/2 (where L p = K 22 /W is the penetration length), corresponding to different anchoring strengths and shape potentials. The dependence of the director distribution in the wall upon all three Frank elastic moduli is analytically found for some specific limiting cases of the model anchoring potentials. Motion of the wall is briefly investigated and the corresponding calculations performed under the assumption that the shape of a moving wall is the same as a motionless one. It is noted that experimental investigation of the walls in planar cholesteric layers can be used for the determination of the actual shape of surface anchoring potentials

  1. Magnetic Nanoparticle-Assisted Tunable Optical Patterns from Spherical Cholesteric Liquid Crystal Bragg Reflectors

    Directory of Open Access Journals (Sweden)

    Yali Lin

    2017-11-01

    Full Text Available Cholesteric liquid crystals (CLCs exhibit selective Bragg reflections of circularly polarized (CP light owing to their spontaneous self-assembly abilities into periodic helical structures. Photonic cross-communication patterns could be generated toward potential security applications by spherical cholesteric liquid crystal (CLC structures. To endow these optical patterns with tunability, we fabricated spherical CLC Bragg reflectors in the shape of microshells by glass-capillary microfluidics. Water-soluble magnetofluid with Fe3O4 nanoparticles incorporated in the inner aqueous core of CLC shells is responsible for the non-invasive transportable capability. With the aid of an external magnetic field, the reflection interactions between neighboring microshells and microdroplets were identified by varying the mutual distance in a group of magnetically transportable and unmovable spherical CLC structures. The temperature-dependent optical reflection patterns were investigated in close-packed hexagonal arrangements of seven CLC microdroplets and microshells with inverse helicity handedness. Moreover, we demonstrated that the magnetic field-assisted assembly of microshells array into geometric figures of uppercase English letters “L” and “C” was successfully achieved. We hope that these findings can provide good application prospects for security pattern designs.

  2. Magnetic Nanoparticle-Assisted Tunable Optical Patterns from Spherical Cholesteric Liquid Crystal Bragg Reflectors.

    Science.gov (United States)

    Lin, Yali; Yang, Yujie; Shan, Yuwei; Gong, Lingli; Chen, Jingzhi; Li, Sensen; Chen, Lujian

    2017-11-08

    Cholesteric liquid crystals (CLCs) exhibit selective Bragg reflections of circularly polarized (CP) light owing to their spontaneous self-assembly abilities into periodic helical structures. Photonic cross-communication patterns could be generated toward potential security applications by spherical cholesteric liquid crystal (CLC) structures. To endow these optical patterns with tunability, we fabricated spherical CLC Bragg reflectors in the shape of microshells by glass-capillary microfluidics. Water-soluble magnetofluid with Fe₃O₄ nanoparticles incorporated in the inner aqueous core of CLC shells is responsible for the non-invasive transportable capability. With the aid of an external magnetic field, the reflection interactions between neighboring microshells and microdroplets were identified by varying the mutual distance in a group of magnetically transportable and unmovable spherical CLC structures. The temperature-dependent optical reflection patterns were investigated in close-packed hexagonal arrangements of seven CLC microdroplets and microshells with inverse helicity handedness. Moreover, we demonstrated that the magnetic field-assisted assembly of microshells array into geometric figures of uppercase English letters "L" and "C" was successfully achieved. We hope that these findings can provide good application prospects for security pattern designs.

  3. What is refractive optical bistability

    International Nuclear Information System (INIS)

    Dzhehov, Tomislav

    1993-01-01

    The basic elements of the theory of refractive optical bistability, assuming mediums with linear absorption are given. Special attention is paid to bistable etalons of semiconductor materials an oxide glasses, since some of them are considered as promising components for optical bistability applications. The design optimization of such devices for minimum switching intensity is analyzed. Computer simulation of the transfer characteristic recording for two InSb etalons is presented. (author)

  4. A Redox-Active Bistable Molecular Switch Mounted inside a Metal-Organic Framework.

    Science.gov (United States)

    Chen, Qishui; Sun, Junling; Li, Peng; Hod, Idan; Moghadam, Peyman Z; Kean, Zachary S; Snurr, Randall Q; Hupp, Joseph T; Farha, Omar K; Stoddart, J Fraser

    2016-11-02

    We describe the incorporation of a bistable mechanically interlocked molecule (MIM) into a robust Zr-based metal-organic framework (MOF), NU-1000, by employing a post-synthetic functionalization protocol. On average, close to two bistable [2]catenanes can be incorporated per repeating unit of the hexagonal channels of NU-1000. The reversible redox-switching of the bistable [2]catenanes is retained inside the MOF, as evidenced by solid-state UV-vis-NIR reflectance spectroscopy and cyclic voltammetry. This research demonstrates that bistable MIMs are capable of exhibiting robust dynamics inside the nanopores of a MOF.

  5. The unsaturated bistable stochastic resonance system.

    Science.gov (United States)

    Zhao, Wenli; Wang, Juan; Wang, Linze

    2013-09-01

    We investigated the characteristics of the output saturation of the classical continuous bistable system (saturation bistable system) and its impact on stochastic resonance (SR). We further proposed a piecewise bistable SR system (unsaturated bistable system) and developed the expression of signal-to-noise ratio (SNR) using the adiabatic approximation theory. Compared with the saturation bistable system, the SNR is significantly improved in our unsaturated bistable SR system. The numerical simulation showed that the unsaturated bistable system performed better in extracting weak signals from strong background noise than the saturation bistable system.

  6. Controlling bistability by linear augmentation

    International Nuclear Information System (INIS)

    Sharma, Pooja Rani; Shrimali, Manish Dev; Prasad, Awadhesh; Feudel, Ulrike

    2013-01-01

    In many bistable oscillating systems only one of the attractors is desired to possessing certain system performance. We present a method to drive a bistable system to a desired target attractor by annihilating the other one. This shift from bistability to monostability is achieved by augmentation of the nonlinear oscillator with a linear control system. For a proper choice of the control function one of the attractors disappears at a critical coupling strength in an control-induced boundary crisis. This transition from bistability to monostability is demonstrated with two paradigmatic examples, the autonomous Chua oscillator and a neuronal system with a periodic input signal.

  7. Bistable Mechanisms for Space Applications.

    Science.gov (United States)

    Zirbel, Shannon A; Tolman, Kyler A; Trease, Brian P; Howell, Larry L

    2016-01-01

    Compliant bistable mechanisms are monolithic devices with two stable equilibrium positions separated by an unstable equilibrium position. They show promise in space applications as nonexplosive release mechanisms in deployment systems, thereby eliminating friction and improving the reliability and precision of those mechanical devices. This paper presents both analytical and numerical models that are used to predict bistable behavior and can be used to create bistable mechanisms in materials not previously feasible for compliant mechanisms. Materials compatible with space applications are evaluated for use as bistable mechanisms and prototypes are fabricated in three different materials. Pin-puller and cutter release mechanisms are proposed as potential space applications.

  8. Bistable microelectromechanical actuator

    Science.gov (United States)

    Fleming, James G.

    1999-01-01

    A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing.

  9. Optical bistability in a single-sided cavity coupled to a quantum channel

    Science.gov (United States)

    Payravi, M.; Solookinejad, Gh; Jabbari, M.; Nafar, M.; Ahmadi Sangachin, E.

    2018-06-01

    In this paper, we discuss the long wavelength optical reflection and bistable behavior of an InGaN/GaN quantum dot nanostructure coupled to a single-sided cavity. It is found that due to the presence of a strong coupling field, the reflection coefficient can be controlled at long wavelength, which is essential for adjusting the threshold of reflected optical bistability. Moreover, the phase shift features of the reflection pulse inside an electromagnetically induced transparency window are also discussed.

  10. Printable optical sensors based on H-bonded supramolecular cholesteric liquid crystal networks.

    Science.gov (United States)

    Herzer, Nicole; Guneysu, Hilal; Davies, Dylan J D; Yildirim, Derya; Vaccaro, Antonio R; Broer, Dirk J; Bastiaansen, Cees W M; Schenning, Albertus P H J

    2012-05-09

    A printable H-bonded cholesteric liquid crystal (CLC) polymer film has been fabricated that, after conversion to a hygroscopic polymer salt film, responds to temperature and humidity by changing its reflection color. Fast-responding humidity sensors have been made in which the reflection color changes between green and yellow depending on the relative humidity. The change in reflection band is a result of a change in helix pitch in the film due to absorption and desorption of water, resulting in swelling/deswelling of the film material. When the polymer salt was saturated with water, a red-reflecting film was obtained that can potentially act as a time/temperature integrator. Finally, the films were printed on a foil, showing the potential application of supramolecular CLC materials as low-cost, printable, battery-free optical sensors.

  11. Structural Transitions in Cholesteric Liquid Crystal Droplets

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A.; Rahimi, Mohammad; Roberts, Tyler F.; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L.; de Pablo, Juan J.

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.

  12. Distributed processing in bistable perception

    NARCIS (Netherlands)

    Knapen, T.H.J.

    2007-01-01

    A very incisive way of studying visual awareness and the mechanisms that underlie it, it to use bistable perception. In bistable perception, an observer's perceptual state alternates between one interpretation and its mutually exclusive counterpart while the stimulus remains the same. This gives us

  13. A helical naphthopyran dopant for photoresponsive cholesteric liquid crystals

    OpenAIRE

    Kim, Yuna; Frigoli, Michel; Vanthuyne, Nicolas; Tamaoki, Nobuyuki

    2017-01-01

    The first photoresponsive cholesteric liquid crystal comprising a photoisomerizable helical naphthopyran derivative dopant and a nematic liquid crystal is reported. An unprecedented helical twisting power switching ratio of over 90% allowed us to demonstrate multi-cycle rotational motion of micro-objects by UV light irradiation.

  14. Topological symmetry breakdown in cholesterics, nematics, and 3He

    International Nuclear Information System (INIS)

    Balachandran, A.P.; Lizzi, F.; Rodgers, V.G.J.

    1984-01-01

    Cholesterics, uniaxial and biaxial nematics, and the dipole-free A phase of superfluid 3 He are characterized by order parameters which are left invariant by suitable ''symmetry'' groups H. We show that in the presence of defects, the full group H may not be implementable on the states because of topological obstructions. Thus H is topologically broken in the presence of suitable defects

  15. Reversibly Bistable Flexible Electronics

    KAUST Repository

    Alfaraj, Nasir

    2015-05-01

    Introducing the notion of transformational silicon electronics has paved the way for integrating various applications with silicon-based, modern, high-performance electronic circuits that are mechanically flexible and optically semitransparent. While maintaining large-scale production and prototyping rapidity, this flexible and translucent scheme demonstrates the potential to transform conventionally stiff electronic devices into thin and foldable ones without compromising long-term performance and reliability. In this work, we report on the fabrication and characterization of reversibly bistable flexible electronic switches that utilize flexible n-channel metal-oxide-semiconductor field-effect transistors. The transistors are fabricated initially on rigid (100) silicon substrates before they are peeled off. They can be used to control flexible batches of light-emitting diodes, demonstrating both the relative ease of scaling at minimum cost and maximum reliability and the feasibility of integration. The peeled-off silicon fabric is about 25 µm thick. The fabricated devices are transferred to a reversibly bistable flexible platform through which, for example, a flexible smartphone can be wrapped around a user’s wrist and can also be set back to its original mechanical position. Buckling and cyclic bending of such host platforms brings a completely new dimension to the development of flexible electronics, especially rollable displays.

  16. Optimization of Bistable Viscoelastic Systems

    DEFF Research Database (Denmark)

    Jensen, Kristian Ejlebjærg; Szabo, Peter; Okkels, Fridolin

    2014-01-01

    driving pressure corresponding to the point of bistability, such that the effect is enhanced. The point of bistability is, however, not explicitly contained in the solution, so we opt for a heuristic approach based on the dissipation ratio between the asymmetric and unstable symmetric flow solutions. We...... find a design that significantly reduces the driving pressure required for bistability, and furthermore is in agreement with the approach followed by experimental researchers. Furthermore, by comparing the two asymmetric solutions, we succesfully apply the same approach to a problem with two fluids...

  17. Bistable amphoteric centers in semiconductors

    International Nuclear Information System (INIS)

    Nikitina, A. G.; Zuev, V. V.

    2008-01-01

    It is shown that, at thermodynamic equilibrium, the release of charge carriers from the localized states of bistable amphoteric centers into quasi-free states depends on the degree of compensation. This brings about different functional dependences of the concentration of free charge carriers on temperature. It is found that, in uncompensated semiconductors, the concentration of free charge carriers follows the same dependence in the case of bistable amphoteric centers and bistable amphoteric U - centers, although the distributions of charge carriers over the charge states and configurations are different for these types of centers. The results can be used for interpreting various experimental data insufficiently explained in the context of the traditional approach

  18. Confinement-induced liquid crystalline transitions in amyloid fibril cholesteric tactoids

    Science.gov (United States)

    Nyström, Gustav; Arcari, Mario; Mezzenga, Raffaele

    2018-04-01

    Chirality is ubiquitous in nature and plays crucial roles in biology, medicine, physics and materials science. Understanding and controlling chirality is therefore an important research challenge with broad implications. Unlike other chiral colloids, such as nanocellulose or filamentous viruses, amyloid fibrils form nematic phases but appear to miss their twisted form, the cholesteric or chiral nematic phases, despite a well-defined chirality at the single fibril level. Here we report the discovery of cholesteric phases in amyloids, using β-lactoglobulin fibrils shortened by shear stresses. The physical behaviour of these new cholesteric materials exhibits unprecedented structural complexity, with confinement-driven ordering transitions between at least three types of nematic and cholesteric tactoids. We use energy functional theory to rationalize these results and observe a chirality inversion from the left-handed amyloids to right-handed cholesteric droplets. These findings deepen our understanding of cholesteric phases, advancing their use in soft nanotechnology, nanomaterial templating and self-assembly.

  19. A Miniature Coupled Bistable Vibration Energy Harvester

    International Nuclear Information System (INIS)

    Zhu, D; Arthur, D C; Beeby, S P

    2014-01-01

    This paper reports the design and test of a miniature coupled bistable vibration energy harvester. Operation of a bistable structure largely depends on vibration amplitude rather than frequency, which makes it very promising for wideband vibration energy harvesting applications. A coupled bistable structure consists of a pair of mobile magnets that create two potential wells and thus the bistable phenomenon. It requires lower excitation to trigger bistable operation compared to conventional bistable structures. Based on previous research, this work focused on miniaturisation of the coupled bistable structure for energy harvesting application. The proposed bistable energy harvester is a combination of a Duffing's nonlinear structure and a linear assisting resonator. Experimental results show that the output spectrum of the miniature coupled bistable vibration energy harvester was the superposition of several spectra. It had a higher maximum output power and a much greater bandwidth compared to simply the Duffing's structure without the assisting resonator

  20. Bistability of Cavity Magnon Polaritons

    Science.gov (United States)

    Wang, Yi-Pu; Zhang, Guo-Qiang; Zhang, Dengke; Li, Tie-Fu; Hu, C.-M.; You, J. Q.

    2018-01-01

    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.g., clockwise and counter-clockwise hysteresis loops) in these two cases. The experimental results are well fitted and explained as being due to the Kerr nonlinearity with either a positive or negative coefficient. Moreover, when the magnetic field is tuned away from the anticrossing point of CMPs, we observe simultaneous bistability of both magnons and cavity photons by applying a drive field on the lower branch.

  1. Frontoparietal cortex mediates perceptual transitions in bistable perception.

    Science.gov (United States)

    Weilnhammer, Veith A; Ludwig, Karin; Hesselmann, Guido; Sterzer, Philipp

    2013-10-02

    During bistable vision, perception oscillates between two mutually exclusive percepts despite constant sensory input. Greater BOLD responses in frontoparietal cortex have been shown to be associated with endogenous perceptual transitions compared with "replay" transitions designed to closely match bistability in both perceptual quality and timing. It has remained controversial, however, whether this enhanced activity reflects causal influences of these regions on processing at the sensory level or, alternatively, an effect of stimulus differences that result in, for example, longer durations of perceptual transitions in bistable perception compared with replay conditions. Using a rotating Lissajous figure in an fMRI experiment on 15 human participants, we controlled for potential confounds of differences in transition duration and confirmed previous findings of greater activity in frontoparietal areas for transitions during bistable perception. In addition, we applied dynamic causal modeling to identify the neural model that best explains the observed BOLD signals in terms of effective connectivity. We found that enhanced activity for perceptual transitions is associated with a modulation of top-down connectivity from frontal to visual cortex, thus arguing for a crucial role of frontoparietal cortex in perceptual transitions during bistable perception.

  2. Temporal nonlocality in bistable perception

    Science.gov (United States)

    Atmanspacher, Harald; Filk, Thomas

    2012-12-01

    A novel conceptual framework for theoretical psychology is presented and illustrated for the example of bistable perception. A basic formal feature of this framework is the non-commutativity of operations acting on mental states. A corresponding model for the bistable perception of ambiguous stimuli, the Necker-Zeno model, is sketched and some empirical evidence for it so far is described. It is discussed how a temporal nonlocality of mental states, predicted by the model, can be understood and tested.

  3. Perceptual incongruence influences bistability and cortical activation

    NARCIS (Netherlands)

    Brouwer, G.J.; Tong, F.; Hagoort, P.; van Ee, R.

    2009-01-01

    We employed a parametric psychophysical design in combination with functional imaging to examine the influence of metric changes in perceptual incongruence on perceptual alternation rates and cortical responses. Subjects viewed a bistable stimulus defined by incongruent depth cues; bistability

  4. GABA shapes the dynamics of bistable perception

    NARCIS (Netherlands)

    van Loon, A.M.; Knapen, T.; Scholte, H.S.; St. John-Saaltink, E.; Donner, T.H.; Lamme, V.A.F.

    2013-01-01

    Sometimes, perception fluctuates spontaneously between two distinct interpretations of a constant sensory input. These bistable perceptual phenomena provide a unique window into the neural mechanisms that create the contents of conscious perception. Models of bistable perception posit that mutual

  5. The re-entrant cholesteric phase of DNA

    Science.gov (United States)

    Yevdokimov, Yu. M.; Skuridin, S. G.; Salyanov, V. I.; Semenov, S. V.; Shtykova, E. V.; Dadinova, L. A.; Kompanets, O. N.; Kats, E. I.

    2017-07-01

    The character of packing of double-stranded DNA molecules in particles of liquid-crystal dispersions formed as a result of the phase exclusion of DNA molecules from aqueous salt polyethylene glycol solutions has been estimated by comparing the circular dichroism (CD) spectra of these dispersions recorded at different osmotic pressures and temperatures. It is shown that the first cycle of heating of dispersion particles with hexagonally packed double-stranded DNA molecules leads to the occurrence of abnormal optical activity of these particles, which manifests itself in the form of a strong negative CD band, characteristic of DNA cholesterics. Moreover, subsequent cooling is accompanied by a further increase in the abnormal optical activity, which indicates the existence of the "hexagonal → cholesteric packing" phase transition, controlled by both the osmotic pressure of the solution and its temperature. The result obtained can be described in terms of "quasi-nematic" layers composed of orientationally ordered DNA molecules in the structure of dispersion particles. There are two possible ways of packing for these layers, which determine their hexagonal or cholesteric spatial structure. The second heating → cooling cycle confirms these results and is indicative of possible differences in the packing of double-stranded DNA molecules in the hexagonal phase, which depend on the osmotic pressure of the solution.

  6. The opto-thermal effect on encapsulated cholesteric liquid crystals

    Science.gov (United States)

    Liu, Yu-Sung; Lin, Hui-Chi; Yang, Kin-Min

    2017-12-01

    In this study, we implemented a micro-encapsulated CLC electronic paper that is optically addressed and electrically erasable. The mechanism that forms spot diameters on the CLC films is discussed and verified through various experimental parameters, including the thickness of CLCs and Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) (PEDOT:PSS), pump intensity, and pumping time. The opto-thermal effect, brought on by the PEDOT:PSS absorbing layer, causes the spot diameters on the cholesteric liquid crystal thin films to vary. According to our results, the spot diameter is larger for a sample with a thinner cholesteric liquid crystal layer with the same excitation conditions and same thickness of the PEDOT layer. The spot diameter is also larger for a sample with a thicker PEDOT under the same excitation conditions and same thickness of the cholesteric liquid crystal layer. We proposed a simple heat-conducting model to explain the experimental results, which qualitatively agree with this theoretical model.

  7. Optical bistability without the rotating wave approximation

    Energy Technology Data Exchange (ETDEWEB)

    Sharaby, Yasser A., E-mail: Yasser_Sharaby@hotmail.co [Physics Department, Faculty of Applied Sciences, Suez Canal University, Suez (Egypt); Joshi, Amitabh, E-mail: ajoshi@eiu.ed [Department of Physics, Eastern Illinois University, Charleston, IL 61920 (United States); Hassan, Shoukry S., E-mail: Shoukryhassan@hotmail.co [Mathematics Department, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain)

    2010-04-26

    Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.

  8. Optical bistability without the rotating wave approximation

    International Nuclear Information System (INIS)

    Sharaby, Yasser A.; Joshi, Amitabh; Hassan, Shoukry S.

    2010-01-01

    Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.

  9. A hierarchical stochastic model for bistable perception.

    Directory of Open Access Journals (Sweden)

    Stefan Albert

    2017-11-01

    Full Text Available Viewing of ambiguous stimuli can lead to bistable perception alternating between the possible percepts. During continuous presentation of ambiguous stimuli, percept changes occur as single events, whereas during intermittent presentation of ambiguous stimuli, percept changes occur at more or less regular intervals either as single events or bursts. Response patterns can be highly variable and have been reported to show systematic differences between patients with schizophrenia and healthy controls. Existing models of bistable perception often use detailed assumptions and large parameter sets which make parameter estimation challenging. Here we propose a parsimonious stochastic model that provides a link between empirical data analysis of the observed response patterns and detailed models of underlying neuronal processes. Firstly, we use a Hidden Markov Model (HMM for the times between percept changes, which assumes one single state in continuous presentation and a stable and an unstable state in intermittent presentation. The HMM captures the observed differences between patients with schizophrenia and healthy controls, but remains descriptive. Therefore, we secondly propose a hierarchical Brownian model (HBM, which produces similar response patterns but also provides a relation to potential underlying mechanisms. The main idea is that neuronal activity is described as an activity difference between two competing neuronal populations reflected in Brownian motions with drift. This differential activity generates switching between the two conflicting percepts and between stable and unstable states with similar mechanisms on different neuronal levels. With only a small number of parameters, the HBM can be fitted closely to a high variety of response patterns and captures group differences between healthy controls and patients with schizophrenia. At the same time, it provides a link to mechanistic models of bistable perception, linking the group

  10. A hierarchical stochastic model for bistable perception.

    Science.gov (United States)

    Albert, Stefan; Schmack, Katharina; Sterzer, Philipp; Schneider, Gaby

    2017-11-01

    Viewing of ambiguous stimuli can lead to bistable perception alternating between the possible percepts. During continuous presentation of ambiguous stimuli, percept changes occur as single events, whereas during intermittent presentation of ambiguous stimuli, percept changes occur at more or less regular intervals either as single events or bursts. Response patterns can be highly variable and have been reported to show systematic differences between patients with schizophrenia and healthy controls. Existing models of bistable perception often use detailed assumptions and large parameter sets which make parameter estimation challenging. Here we propose a parsimonious stochastic model that provides a link between empirical data analysis of the observed response patterns and detailed models of underlying neuronal processes. Firstly, we use a Hidden Markov Model (HMM) for the times between percept changes, which assumes one single state in continuous presentation and a stable and an unstable state in intermittent presentation. The HMM captures the observed differences between patients with schizophrenia and healthy controls, but remains descriptive. Therefore, we secondly propose a hierarchical Brownian model (HBM), which produces similar response patterns but also provides a relation to potential underlying mechanisms. The main idea is that neuronal activity is described as an activity difference between two competing neuronal populations reflected in Brownian motions with drift. This differential activity generates switching between the two conflicting percepts and between stable and unstable states with similar mechanisms on different neuronal levels. With only a small number of parameters, the HBM can be fitted closely to a high variety of response patterns and captures group differences between healthy controls and patients with schizophrenia. At the same time, it provides a link to mechanistic models of bistable perception, linking the group differences to

  11. Bistable microvalve and microcatheter system

    Science.gov (United States)

    Seward, Kirk Patrick

    2003-05-20

    A bistable microvalve of shape memory material is operatively connected to a microcatheter. The bistable microvalve includes a tip that can be closed off until it is in the desired position. Once it is in position it can opened and closed. The system uses heat and pressure to open and close the microvalve. The shape memory material will change stiffness and shape when heated above a transition temperature. The shape memory material is adapted to move from a first shape to a second shape, either open or closed, where it can perform a desired function.

  12. Optical bistability controlling light with light

    CERN Document Server

    Gibbs, Hyatt

    1985-01-01

    Optical Bistability: Controlling Light with Light focuses on optical bistability in nonlinear optical systems. Emphasis is on passive (non-laser) systems that exhibit reversible bistability with input intensity as the hysteresis variable, along with the physics and the potential applications of such systems for nonlinear optical signal processing. This book consists of seven chapters and begins with a historical overview of optical bistability in lasers and passive systems. The next chapter describes steady-state theories of optical bistability, including the Bonifacio-Lugiato model, as we

  13. Optical bistability of a thin film of resonant atoms in a phase-sensitive thermostate

    International Nuclear Information System (INIS)

    Basharov, A.M.

    1995-01-01

    It is shown theoretically that when a thin film of two-level atoms interacting with a resonant coherent electromagnetic wave is additionally illuminated with a squeezed field, a bistable transmission/reflection regime for coherent waves is obtained. This regime depends strongly on the phase difference between the coherent and the squeezed fields. New regimes, including a bistable regime, for the interaction of a coherent field with a film of resonant atoms are predicted based on this phenomenon. 14 refs., 5 figs

  14. Bi-stable optical actuator

    Science.gov (United States)

    Holdener, Fred R.; Boyd, Robert D.

    2000-01-01

    The present invention is a bi-stable optical actuator device that is depowered in both stable positions. A bearing is used to transfer motion and smoothly transition from one state to another. The optical actuator device may be maintained in a stable position either by gravity or a restraining device.

  15. Beam coupling in hybrid photorefractive inorganic-cholesteric liquid crystal cells: Impact of optical rotation

    International Nuclear Information System (INIS)

    Reshetnyak, V. Yu.; Pinkevych, I. P.; Sluckin, T. J.; Cook, G.; Evans, D. R.

    2014-01-01

    We develop a theoretical model to describe two-beam energy exchange in a hybrid photorefractive inorganic-cholesteric cell. A cholesteric layer is placed between two inorganic substrates. One of the substrates is photorefractive (Ce:SBN). Weak and strong light beams are incident on the hybrid cell. The interfering light beams induce a periodic space-charge field in the photorefractive window. This penetrates into the cholesteric liquid crystal (LC), inducing a diffraction grating written on the LC director. In the theory, the flexoelectric mechanism for electric field-director coupling is more important than the LC static dielectric anisotropy coupling. The LC optics is described in the Bragg regime. Each beam induces two circular polarized waves propagating in the cholesteric cell with different velocities. The model thus includes optical rotation in the cholesteric LC. The incident light beam wavelength can fall above, below, or inside the cholesteric gap. The theory calculates the energy gain of the weak beam, as a result of its interaction with the pump beam within the diffraction grating. Theoretical results for exponential gain coefficients are compared with experimental results for hybrid cells filled with cholesteric mixture BL038/CB15 at different concentrations of chiral agent CB15. Reconciliation between theory and experiment requires the inclusion of a phenomenological multiplier in the magnitude of the director grating. This multiplier is cubic in the space-charge field, and we provide a justification of the q-dependence of the multiplier. Within this paradigm, we are able to fit theory to experimental data for cholesteric mixtures with different spectral position of cholesteric gap relative to the wavelength of incident beams, subject to the use of some fitting parameters

  16. Time-dependent deformation of polymer network in polymer-stabilized cholesteric liquid crystals (Conference Presentation)

    Science.gov (United States)

    Lee, Kyung Min; Tondiglia, Vincent P.; Bunning, Timothy J.; White, Timothy J.

    2017-02-01

    Recently, we reported direct current (DC) field controllable electro-optic (EO) responses of negative dielectric anisotropy polymer stabilized cholesteric liquid crystals (PSCLCs). A potential mechanism is: Ions in the liquid crystal mixtures are trapped in/on the polymer network during the fast photopolymerization process, and the movement of ions by the application of the DC field distorts polymer network toward the negative electrode, inducing pitch variation through the cell thickness, i.e., pitch compression on the negative electrode side and pitch expansion on positive electrode side. As the DC voltage is directly applied to a target voltage, charged polymer network is deformed and the reflection band is tuned. Interestingly, the polymer network deforms further (red shift of reflection band) with time when constantly applied DC voltage, illustrating DC field induced time dependent deformation of polymer network (creep-like behavior). This time dependent reflection band changes in PSCLCs are investigated by varying the several factors, such as type and concentration of photoinitiators, liquid crystal monomer content, and curing condition (UV intensity and curing time). In addition, simple linear viscoelastic spring-dashpot models, such as 2-parameter Kelvin and 3-parameter linear models, are used to investigate the time-dependent viscoelastic behaviors of polymer networks in PSCLC.

  17. Bistability in a laser with injected signal

    International Nuclear Information System (INIS)

    Dorobantu, I.A.; Vlad, V.I.; Ursu, I.

    1987-04-01

    A unified description of bistability is given in free running lasers, optical bistable devices, ring lasers and lasers with an injected signal (LIS). A general review of laser instabilities is also presented in the frame of the theory of elementary catastrophes, emphasizing the apparence of higher order catastrophes in the case of a LIS suggesting thus a possibility to devise from first principles the whole hierarchy of laser instabilities. Experimental results on the bistability in the polarisation of LIS are also discussed. (authors)

  18. A broadband electromagnetic energy harvester with a coupled bistable structure

    International Nuclear Information System (INIS)

    Zhu, D; Beeby, S P

    2013-01-01

    This paper investigates a broadband electromagnetic energy harvester with a coupled bistable structure. Both analytical model and experimental results showed that the coupled bistable structure requires lower excitation force to trigger bistable operation than conventional bistable structures. A compact electromagnetic vibration energy harvester with a coupled bistable structure was implemented and tested. It was excited under white noise vibrations. Experimental results showed that the coupled bistable energy harvester can achieve bistable operation with lower excitation amplitude and generate more output power than both conventional bistable and linear energy harvesters under white noise excitation

  19. A bistable mechanism for directional sensing

    International Nuclear Information System (INIS)

    Beta, C; Amselem, G; Bodenschatz, E

    2008-01-01

    We present a generic mechanism for directional sensing in eukaryotic cells that is based on bistable dynamics. As the key feature of this modeling approach, the velocity of trigger waves in the bistable sensing system changes its sign across cells that are exposed to an external chemoattractant gradient. This is achieved by combining a two-component activator/inhibitor system with a bistable switch that induces an identical symmetry breaking for arbitrary gradient input signals. A simple kinetic example is designed to illustrate the dynamics of a bistable directional sensing mechanism in numerical simulations

  20. Bistable diverter valve in microfluidics

    Czech Academy of Sciences Publication Activity Database

    Tesař, Václav; Bandulasena, H.C.H.

    2011-01-01

    Roč. 50, č. 5 (2011), s. 1225-1233 ISSN 0723-4864 R&D Projects: GA ČR GA101/07/1499; GA AV ČR IAA200760705 Institutional research plan: CEZ:AV0Z20760514 Keywords : fluidics * bistable diverter valves * pressure-driven microfluidics Subject RIV: BK - Fluid Dynamics Impact factor: 1.735, year: 2011 http://www.springerlink.com/content/x4907p1908151522/

  1. Brain networks underlying bistable perception.

    Science.gov (United States)

    Baker, Daniel H; Karapanagiotidis, Theodoros; Coggan, David D; Wailes-Newson, Kirstie; Smallwood, Jonathan

    2015-10-01

    Bistable stimuli, such as the Necker Cube, demonstrate that experience can change in the absence of changes in the environment. Such phenomena can be used to assess stimulus-independent aspects of conscious experience. The current study used resting state functional magnetic resonance imaging (rs-fMRI) to index stimulus-independent changes in neural activity to understand the neural architecture that determines dominance durations during bistable perception (using binocular rivalry and Necker cube stimuli). Anterior regions of the Superior Parietal Lobule (SPL) exhibited robust connectivity with regions of primary sensorimotor cortex. The strength of this region's connectivity with the striatum predicted shorter dominance durations during binocular rivalry, whereas its connectivity to pre-motor cortex predicted longer dominance durations for the Necker Cube. Posterior regions of the SPL, on the other hand, were coupled to associative cortex in the temporal and frontal lobes. The posterior SPL's connectivity to the temporal lobe predicted longer dominance during binocular rivalry. In conjunction with prior work, these data suggest that the anterior SPL contributes to perceptual rivalry through the inhibition of incongruent bottom up information, whereas the posterior SPL influences rivalry by supporting the current interpretation of a bistable stimulus. Our data suggests that the functional connectivity of the SPL with regions of sensory, motor, and associative cortex allows it to regulate the interpretation of the environment that forms the focus of conscious attention at a specific moment in time. Copyright © 2015. Published by Elsevier Inc.

  2. The Independent and Shared Mechanisms of Intrinsic Brain Dynamics: Insights From Bistable Perception

    Directory of Open Access Journals (Sweden)

    Teng Cao

    2018-04-01

    Full Text Available In bistable perception, constant input leads to alternating perception. The dynamics of the changing perception reflects the intrinsic dynamic properties of the “unconscious inferential” process in the brain. Under the same condition, individuals differ in how fast they experience the perceptual alternation. In this study, testing many forms of bistable perception in a large number of observers, we investigated the key question of whether there is a general and common mechanism or multiple and independent mechanisms that control the dynamics of the inferential brain. Bistable phenomena tested include binocular rivalry, vase-face, Necker cube, moving plaid, motion induced blindness, biological motion, spinning dancer, rotating cylinder, Lissajous-figure, rolling wheel, and translating diamond. Switching dynamics for each bistable percept was measured in 100 observers. Results show that the switching rates of subsets of bistable percept are highly correlated. The clustering of dynamic properties of some bistable phenomena but not an overall general control of switching dynamics implies that the brain’s inferential processes are both shared and independent – faster in constructing 3D structure from motion does not mean faster in integrating components into an objects.

  3. Robust microfluidic encapsulation of cholesteric liquid crystals toward photonic ink capsules.

    Science.gov (United States)

    Lee, Sang Seok; Kim, Bomi; Kim, Su Kyung; Won, Jong Chan; Kim, Yun Ho; Kim, Shin-Hyun

    2015-01-27

    Robust photonic microcapsules are created by microfluidic encapsulation of cholesteric liquid crystals with a hydrogel membrane. The membrane encloses the cholesteric core without leakage in water and the core exhibits pronounced structural colors. The photonic ink capsules, which have a precisely controlled bandgap position and size, provide new opportunities in colorimetric micro-thermometers and optoelectric applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A novel bistable energy harvesting concept

    International Nuclear Information System (INIS)

    Scarselli, G; Nicassio, F; Pinto, F; Ciampa, F; Iervolino, O; Meo, M

    2016-01-01

    Bistable energy harvesting has become a major field of research due to some unique features for converting mechanical energy into electrical power. When properly loaded, bistable structures snap-through from one stable configuration to another, causing large strains and consequently power generation. Moreover, bistable structures can harvest energy across a broad-frequency bandwidth due to their nonlinear characteristics. Despite the fact that snap-through may be triggered regardless of the form or frequency of exciting vibration, the external force must reach a specific snap-through activation threshold value to trigger the transition from one stable state to another. This aspect is a limiting factor for realistic vibration energy harvesting application with bistable devices. This paper presents a novel power harvesting concept for bistable composites based on a ‘lever effect’ aimed at minimising the activation force to cause the snap through by choosing properly the bistable structures’ constraints. The concept was demonstrated with the help of numerical simulation and experimental testing. The results showed that the actuation force is one order of magnitude smaller (3%–6%) than the activation force of conventionally constrained bistable devices. In addition, it was shown that the output voltage was higher than the conventional configuration, leading to a significant increase in power generation. This novel concept could lead to a new generation of more efficient bistable energy harvesters for realistic vibration environments. (paper)

  5. Amplified Photon Upconversion by Photonic Shell of Cholesteric Liquid Crystals.

    Science.gov (United States)

    Kang, Ji-Hwan; Kim, Shin-Hyun; Fernandez-Nieves, Alberto; Reichmanis, Elsa

    2017-04-26

    As an effective platform to exploit triplet-triplet-annihilation-based photon upconversion (TTA-UC), microcapsules composed of a fluidic UC core and photonic shell are microfluidically prepared using a triple emulsion as the template. The photonic shell consists of cholesteric liquid crystals (CLCs) with a periodic helical structure, exhibiting a photonic band gap. Combined with planar anchoring at the boundaries, the shell serves as a resonance cavity for TTA-UC emission and enables spectral tuning of the UC under low-power-density excitation. The CLC shell can be stabilized by introducing a polymerizable mesogen in the LC host. Because of the microcapsule spherical symmetry, spontaneous emission of the delayed fluorescence is omnidirectionally amplified at the edge of the stop band. These results demonstrate the range of opportunities provided by TTA-UC systems for the future design of low-threshold photonic devices.

  6. Diversity and functional properties of bistable pigments.

    Science.gov (United States)

    Tsukamoto, Hisao; Terakita, Akihisa

    2010-11-01

    Rhodopsin and related opsin-based pigments, which are photosensitive membrane proteins, have been extensively studied using a wide variety of techniques, with rhodopsin being the most understood G protein-coupled receptor (GPCR). Animals use various opsin-based pigments for vision and a wide variety of non-visual functions. Many functionally varied pigments are roughly divided into two kinds, based on their photoreaction: bistable and monostable pigments. Bistable pigments are thermally stable before and after photo-activation, but monostable pigments are stable only before activation. Here, we review the diversity of bistable pigments and their molecular characteristics. We also discuss the mechanisms underlying different molecular characteristics of bistable and monostable pigments. In addition, the potential of bistable pigments as a GPCR model is proposed.

  7. Brain mechanisms for simple perception and bistable perception.

    Science.gov (United States)

    Wang, Megan; Arteaga, Daniel; He, Biyu J

    2013-08-27

    When faced with ambiguous sensory inputs, subjective perception alternates between the different interpretations in a stochastic manner. Such multistable perception phenomena have intrigued scientists and laymen alike for over a century. Despite rigorous investigations, the underlying mechanisms of multistable perception remain elusive. Recent studies using multivariate pattern analysis revealed that activity patterns in posterior visual areas correlate with fluctuating percepts. However, increasing evidence suggests that vision--and perception at large--is an active inferential process involving hierarchical brain systems. We applied searchlight multivariate pattern analysis to functional magnetic resonance imaging signals across the human brain to decode perceptual content during bistable perception and simple unambiguous perception. Although perceptually reflective activity patterns during simple perception localized predominantly to posterior visual regions, bistable perception involved additionally many higher-order frontoparietal and temporal regions. Moreover, compared with simple perception, both top-down and bottom-up influences were dramatically enhanced during bistable perception. We further studied the intermittent presentation of ambiguous images--a condition that is known to elicit perceptual memory. Compared with continuous presentation, intermittent presentation recruited even more higher-order regions and was accompanied by further strengthened top-down influences but relatively weakened bottom-up influences. Taken together, these results strongly support an active top-down inferential process in perception.

  8. Cholesteric Liquid Crystal Shells as Enabling Material for Information-Rich Design and Architecture.

    Science.gov (United States)

    Schwartz, Mathew; Lenzini, Gabriele; Geng, Yong; Rønne, Peter B; Ryan, Peter Y A; Lagerwall, Jan P F

    2018-05-14

    The responsive and dynamic character of liquid crystals (LCs), arising from their ability to self-organize into long-range ordered structures while maintaining fluidity, has given them a role as key enabling materials in the information technology that surrounds us today. Ongoing research hints at future LC-based technologies of entirely different types, for instance by taking advantage of the peculiar behavior of cholesteric liquid crystals (CLCs) subject to curvature. Spherical shells of CLC reflect light omnidirectionally with specific polarization and wavelength, tunable from the UV to the infrared (IR) range, with complex patterns arising when many of them are brought together. Here, these properties are analyzed and explained, and future application opportunities from an interdisciplinary standpoint are discussed. By incorporating arrangements of CLC shells in smart facades or vehicle coatings, or in objects of high value subject to counterfeiting, game-changing future uses might arise in fields spanning information security, design, and architecture. The focus here is on the challenges of a digitized and information-rich future society where humans increasingly rely on technology and share their space with autonomous vehicles, drones, and robots. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Generation of Light Scattering States in Cholesteric Liquid Crystals by Optically Controlled Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Timothy J. Bunning

    2013-03-01

    Full Text Available Circularly polarized light was previously employed to stimulate the reversible and reconfigurable writing of scattering states in cholesteric liquid crystal (CLC cells constructed with a photosensitive layer. Such dynamic photodriven responses have utility in remotely triggering changes in optical constructs responsive to optical stimulus and applications where complex spatial patterning is required. Writing of scattering regions required the handedness of incoming radiation to match the handedness of the CLC and the reflection bandwidth of the CLC to envelop the wavelength of the incoming radiation. In this paper, the mechanism of transforming the CLC into a light scattering state via the influence of light on the photosensitive alignment layer is detailed. Specifically, the effects of: (i the polarization state of light on the photosensitive alignment layer; (ii the exposure time; and (iii the incidence angle of radiation on domain formation are reported. The photogenerated light-scattering domains are shown to be similar in appearance between crossed polarizers to a defect structure that occurs at a CLC/air interface (i.e., a free CLC surface. This observation provides strong indication that exposure of the photosensitive alignment layer to the circularly polarized light of appropriate wavelength and handedness generates an out-of-plane orientation leading to a periodic distortion of the original planar structure.

  10. A broadband electromagnetic energy harvester with a coupled bistable structure

    OpenAIRE

    Zhu, Dibin; Beeby, Steve

    2013-01-01

    This paper investigates a broadband electromagnetic energy harvester with a coupled bistable structure. Both analytical model and experimental results showed that the coupled bistable structure requires lower excitation force to trigger bistable operation than conventional bistable structures. A compact electromagnetic vibration energy harvester with a coupled bistable structure was implemented and tested. It was excited under white noise vibrations. Experimental results showed that the coupl...

  11. Transcriptional delay stabilizes bistable gene networks.

    Science.gov (United States)

    Gupta, Chinmaya; López, José Manuel; Ott, William; Josić, Krešimir; Bennett, Matthew R

    2013-08-02

    Transcriptional delay can significantly impact the dynamics of gene networks. Here we examine how such delay affects bistable systems. We investigate several stochastic models of bistable gene networks and find that increasing delay dramatically increases the mean residence times near stable states. To explain this, we introduce a non-Markovian, analytically tractable reduced model. The model shows that stabilization is the consequence of an increased number of failed transitions between stable states. Each of the bistable systems that we simulate behaves in this manner.

  12. Intrinsic membrane properties causing a bistable behaviour of α-motoneurones

    DEFF Research Database (Denmark)

    Hounsgaard, J.; Hultborn, H.; Jespersen, B.

    1984-01-01

    injected depolarizing current pulse and is terminated by a short train of inhibitory synaptic potentials or a hyperpolarizing current pulse. It is concluded that maintained motor unit firing triggered by a brief train of impulses in Ia afferent reflects an intrinsic bistable behaviour of α-motoneurones....

  13. Possible hysteresis loops of resonatorless optical bistability

    International Nuclear Information System (INIS)

    Nguyen Ba An; Le Thi Cat Tuong.

    1990-05-01

    We qualitatively show that hysteresis loops of intrinsic optical bistability phenomena without any additional feedback may be of various shapes including those of a butterfly and a three-winged bow. (author). 15 refs, 4 figs

  14. Space charge effects and electronic bistability

    International Nuclear Information System (INIS)

    Ruffini, A.; Strumia, F.; Tommasi, O.

    1996-01-01

    The excitation of metastable states in an atomic beam apparatus by means of electron collision is a widespread technique. The authors have observed a large bistable behaviour in apparatus designed to provide an intense and collimated beam of metastable helium by excitation with orthogonally impinging electrons. This bistable behaviour largely affects the efficiency of the apparatus and is therefore worth of being carefully investigated. The apparatus has an electrode configuration equivalent to that of a tetrode valve with large intergrid distances. The bistability consists in a hysteresis cycle in the curve of the anode current vs. grid voltage. Experimental measurements, supported by a simple theoretical model and by numerical simulation, stress out the crucial role played by space charge effects for the onset of bistability. A comparison with previous observations of this phenomenon is given. Spontaneous current oscillations with various shapes have been recorded in one of the two curves of the hysteresis cycle

  15. Bistable fluidic valve is electrically switched

    Science.gov (United States)

    Fiet, O.; Salvinski, R. J.

    1970-01-01

    Bistable control valve is selectively switched by direct application of an electrical field to divert fluid from one output channel to another. Valve is inexpensive, has no moving parts, and operates on fluids which are relatively poor electrical conductors.

  16. Origami Mechanics: Bistability and Isometries

    Science.gov (United States)

    Adda-Bedia, Mokhtar; Lechenault, Frederic; Morphogenesis; multiscale phenomena Team

    2015-03-01

    Origami structures are usually seen as assemblies of rigid faces articulated around creases with hinge-like behaviour. Their deployment and degrees of freedom are purely kinematic, resulting only from the geometry of the crease network. However, in real folded structures, the base material can deform outside the creases. In such situations, face bending competes with crease actuation in a morphogenetic way. In order to rationalise this interplay, we investigate the mechanical behaviour of an infinite sheet on which one or more straight creases meet at a single vertex. We find that these structures generically exhibit bistability, in the sense that they can snap through from one metastable configuration to another. Furthermore, we uncover a new class of isometry of the plane, which corresponds to metastable states of a creased sheet for which the hoop stress vanishes, an instability mechanism that is also responsible for the wrinkling of thin plates.

  17. All-optical bistable logic control based on coupled Tamm plasmons.

    Science.gov (United States)

    Zhang, Wei Li; Jiang, Yao; Zhu, Ye Yu; Wang, Fen; Rao, Yun Jiang

    2013-10-15

    A method for realizing low-threshold all-optical bistable logic control is proposed based on Tamm plasmons (TPs), which are formed in an asymmetric dielectric Bragg reflector (DBR)-metal-DBR (ADMD) structure with a layer of Kerr medium embedded. The ADMD structure supports two TPs due to coupling of trapped modes at each metal-DBR interface, generating two dips in the structure's reflection spectrum. Thus, control (i.e., pump) and controlled (i.e., probe) light with wavelengths close to the two dips, respectively, can be imported. It is verified theoretically that, thanks to the enhanced Kerr nonlinearity related to excitation of high-quality TP, bistable switching at very low injection intensity can be initiated by strength or direction variation of the pump. Meanwhile, the probe changes correspondingly with the pump. Thus, all-optical bistable logic operation of the probe can be controlled by the pump.

  18. Simulation of light generation in cholesteric liquid crystals using kinetic equations: Time-independent solution

    Energy Technology Data Exchange (ETDEWEB)

    Shtykov, N. M., E-mail: nshtykov@mail.ru; Palto, S. P.; Umanskii, B. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2013-08-15

    We report on the results of calculating the conditions for light generation in cholesteric liquid crystals doped with fluorescent dyes using kinetic equations. Specific features of spectral properties of the chiral cholesteric medium as a photonic structure and spatially distributed type of the feedback in the active medium are taken into account. The expression is derived for the threshold pump radiation intensity as a function of the dye concentration and sample thickness. The importance of taking into account the distributed loss level in the active medium for calculating the optimal parameters of the medium and for matching the calculated values with the results of experiments is demonstrated.

  19. Tunable single photonic defect-mode in cholesteric liquid crystals with laser-induced local modifications of helix

    International Nuclear Information System (INIS)

    Yoshida, Hiroyuki; Lee, Chee Heng; Fujii, Akihiko; Ozaki, Masanori

    2006-01-01

    The authors demonstrate a tunable single photonic defect-mode in a single cholesteric liquid crystal material based on a structural defect introduced by local modification of the helix. An unpolymerized region of cholesteric liquid crystal acting as the defect was left between two polymerized regions via a two-photon excitation laser-lithography process. Upon polymerization, the cholesteric liquid crystal helix elongated and became thermally stable, and a single photonic defect mode was exhibited due to the contrast in the helix pitch at the defect. The defect mode showed tunability upon heating, and a 36 nm redshift was seen over a temperature range of 30 deg. C

  20. Bubbling and bistability in two parameter discrete systems

    Indian Academy of Sciences (India)

    The birth of X *. · is concurrent with the ... for bistability viz. a½, and the higher order bistability points a¾, etc. are marked. The quadrilateral marked as ... The characteristics of 2 parameter 1-d maps that exhibit bubbling/bistability related to their ...

  1. Visualizing Molecular Chirality in the Organic Chemistry Laboratory Using Cholesteric Liquid Crystals

    Science.gov (United States)

    Popova, Maia; Bretz, Stacey Lowery; Hartley, C. Scott

    2016-01-01

    Although stereochemistry is an important topic in second-year undergraduate organic chemistry, there are limited options for laboratory activities that allow direct visualization of macroscopic chiral phenomena. A novel, guided-inquiry experiment was developed that allows students to explore chirality in the context of cholesteric liquid crystals.…

  2. Alcohol-responsive, hydrogen-bonded, cholesteric liquid-crystal networks

    NARCIS (Netherlands)

    Chang, C.; Bastiaansen, C.W.M.; Broer, D.J.; Kuo, H.-L.

    2012-01-01

    Hydrogen-bridged, cholesteric liquid-crystal (CLC) polymer networks are adopted as an optical sensor material to distinguish between ethanol and methanol. Fast uptake of the alcohols is facilitated by an incorporated porosity created by breaking the hydrogen bridges and by a previously removed

  3. Perceptual incongruence influences bistability and cortical activation.

    Directory of Open Access Journals (Sweden)

    Gijs Joost Brouwer

    Full Text Available We employed a parametric psychophysical design in combination with functional imaging to examine the influence of metric changes in perceptual incongruence on perceptual alternation rates and cortical responses. Subjects viewed a bistable stimulus defined by incongruent depth cues; bistability resulted from incongruence between binocular disparity and monocular perspective cues that specify different slants (slant rivalry. Psychophysical results revealed that perceptual alternation rates were positively correlated with the degree of perceived incongruence. Functional imaging revealed systematic increases in activity that paralleled the psychophysical results within anterior intraparietal sulcus, prior to the onset of perceptual alternations. We suggest that this cortical activity predicts the frequency of subsequent alternations, implying a putative causal role for these areas in initiating bistable perception. In contrast, areas implicated in form and depth processing (LOC and V3A were sensitive to the degree of slant, but failed to show increases in activity when these cues were in conflict.

  4. Longitudinal magnetic bistability of electroplated wires

    International Nuclear Information System (INIS)

    Kurlyandskaya, G.V.; Garcia-Miquel, H.; Vazquez, M.; Svalov, A.V.; Vas'kovskiy, V.O.

    2002-01-01

    Fe 20 Ni 74 Co 6 and Fe 20 Ni 64 Co 16 1 μm thick magnetic tubes electroplated onto Cu 98 Be 2 conductive wire have been investigated in as-deposited state, after heat treatment under longitudinal magnetic field for 1 h at 330 deg. C, and after rf-sputtering deposition of the additional 2 μm Fe 19 Ni 81 layer. Heat treatments and an additional layer deposition modify the shape of hysteresis loops. Magnetically bistable behaviour, observed after the field annealing at a temperature of 330 deg. C, is studied as a function of the length of the samples. This is the first report by our knowledge on the bistable behaviour of the electroplated wires. The bistability of these wires is promising for applications such as tagging or pulse generator applications

  5. Cholesteric liquid crystals: the blue phase and the analogy with 3He-A

    International Nuclear Information System (INIS)

    Wright, D.C.

    1983-01-01

    Part I of this thesis presents a unified view of some of the theoretical progress on the blue phase of cholesteric liquid crystals. The elastic and bulk cholesteric energies are found to be separately minimized by different forms of the order parameter, and the problem of minimizing the full free energy can be viewed as a competition between these incompatible forms. Near the transition to the high temperature disordered phase, the bulk and elastic contributions may be comparable, and complicated, non-uniform structures can appear as compromise solutions to the minimization problem. These structures are interpreted as the blue phases. The two predominant models for the blue phase, which use either a director or second rank tensor order parameter, are seen in this picture as forms applicable in two limits, when the transition from the disordered phase is strongly and weakly first order, respectively. Both methods of constructing the order parameters, and the relation between them, is presented. Part II of this thesis concerns the problem of describing long wavelength distortions in cholesterics. A proposed analogy between cholesterics and superfluid 3 He-A, with the uniform twist in cholesterics corresponding to stable superflow in helium is considered. The difficulty with such a description lies in attempting to define variables which are well-defined in the distorted system and which vary slowly enough to justify a gradient expansion of the distortion energy. By requiring the variables in such a theory to be slowly varying, as in the superfluid case, only director configurations which are not stationary points of the free energy can be described. A solution is proposed which includes rapid variations of the director and corrects this description in such a way to satisfy the stationary conditions

  6. Balancing bistable perception during self-motion.

    Science.gov (United States)

    van Elk, Michiel; Blanke, Olaf

    2012-10-01

    In two experiments we investigated whether bistable visual perception is influenced by passive own body displacements due to vestibular stimulation. For this we passively rotated our participants around the vertical (yaw) axis while observing different rotating bistable stimuli (bodily or non-bodily) with different ambiguous motion directions. Based on previous work on multimodal effects on bistable perception, we hypothesized that vestibular stimulation should alter bistable perception and that the effects should differ for bodily versus non-bodily stimuli. In the first experiment, it was found that the rotation bias (i.e., the difference between the percentage of time that a CW or CCW rotation was perceived) was selectively modulated by vestibular stimulation: the perceived duration of the bodily stimuli was longer for the rotation direction congruent with the subject's own body rotation, whereas the opposite was true for the non-bodily stimulus (Necker cube). The results found in the second experiment extend the findings from the first experiment and show that these vestibular effects on bistable perception only occur when the axis of rotation of the bodily stimulus matches the axis of passive own body rotation. These findings indicate that the effect of vestibular stimulation on the rotation bias depends on the stimulus that is presented and the rotation axis of the stimulus. Although most studies on vestibular processing have traditionally focused on multisensory signal integration for posture, balance, and heading direction, the present data show that vestibular self-motion influences the perception of bistable bodily stimuli revealing the importance of vestibular mechanisms for visual consciousness.

  7. Bistable Microvalve For Use With Microcatheter System

    Science.gov (United States)

    Seward, Kirk Patrick

    2003-12-16

    A bistable microvalve of shape memory material is operatively connected to a microcatheter. The bistable microvalve includes a tip that can be closed off until it is in the desired position. Once it is in position it can be opened and closed. The system uses heat and pressure to open and close the microvalve. The shape memory material will change stiffness and shape when heated above a transition temperature. The shape memory material is adapted to move from a first shape to a second shape, either open or closed, where it can perform a desired function.

  8. Unidirectional Transition Waves in Bistable Lattices.

    Science.gov (United States)

    Nadkarni, Neel; Arrieta, Andres F; Chong, Christopher; Kochmann, Dennis M; Daraio, Chiara

    2016-06-17

    We present a model system for strongly nonlinear transition waves generated in a periodic lattice of bistable members connected by magnetic links. The asymmetry of the on-site energy wells created by the bistable members produces a mechanical diode that supports only unidirectional transition wave propagation with constant wave velocity. We theoretically justify the cause of the unidirectionality of the transition wave and confirm these predictions by experiments and simulations. We further identify how the wave velocity and profile are uniquely linked to the double-well energy landscape, which serves as a blueprint for transition wave control.

  9. Bistable Topological Insulator with Exciton-Polaritons

    Science.gov (United States)

    Kartashov, Yaroslav V.; Skryabin, Dmitry V.

    2017-12-01

    The functionality of many nonlinear and quantum optical devices relies on the effect of optical bistability. Using microcavity exciton-polaritons in a honeycomb arrangement of microcavity pillars, we report the resonance response and bistability of topological edge states. A balance between the pump, loss, and nonlinearity ensures a broad range of dynamical stability and controls the distribution of power between counterpropagating states on the opposite edges of the honeycomb lattice stripe. Tuning energy and polarization of the pump photons, while keeping their momentum constant, we demonstrate control of the propagation direction of the dominant edge state. Our results facilitate the development of practical applications of topological photonics.

  10. Bistable firing properties of soleus motor units in unrestrained rats

    DEFF Research Database (Denmark)

    EKEN, T.; KIEHN, O.

    1989-01-01

    of the motoneuron pool by stimulation of la afferents, or inhibition by stimulation of skin afferents. The shifts were not related to gross limb movements. This phenomenon is referred to as a bistable firing pattern. Bistable firing also occurred spontaneously during quiet standing. Typically the firing frequency...... was unchanged or only phasically influenced. These results demonstrate for the first time a bistable firing pattern during postural activity in the intact animal. The firing pattern closely resembles the bistable behaviour described in spinal motoneurons in reduced preparations, where it is due to the presence...... of a plateau potential. This suggests that the bistable firing is unexplained by plateau potentials also in the intact animal....

  11. Neuromechanistic Model of Auditory Bistability.

    Directory of Open Access Journals (Sweden)

    James Rankin

    2015-11-01

    Full Text Available Sequences of higher frequency A and lower frequency B tones repeating in an ABA- triplet pattern are widely used to study auditory streaming. One may experience either an integrated percept, a single ABA-ABA- stream, or a segregated percept, separate but simultaneous streams A-A-A-A- and -B---B--. During minutes-long presentations, subjects may report irregular alternations between these interpretations. We combine neuromechanistic modeling and psychoacoustic experiments to study these persistent alternations and to characterize the effects of manipulating stimulus parameters. Unlike many phenomenological models with abstract, percept-specific competition and fixed inputs, our network model comprises neuronal units with sensory feature dependent inputs that mimic the pulsatile-like A1 responses to tones in the ABA- triplets. It embodies a neuronal computation for percept competition thought to occur beyond primary auditory cortex (A1. Mutual inhibition, adaptation and noise are implemented. We include slow NDMA recurrent excitation for local temporal memory that enables linkage across sound gaps from one triplet to the next. Percepts in our model are identified in the firing patterns of the neuronal units. We predict with the model that manipulations of the frequency difference between tones A and B should affect the dominance durations of the stronger percept, the one dominant a larger fraction of time, more than those of the weaker percept-a property that has been previously established and generalized across several visual bistable paradigms. We confirm the qualitative prediction with our psychoacoustic experiments and use the behavioral data to further constrain and improve the model, achieving quantitative agreement between experimental and modeling results. Our work and model provide a platform that can be extended to consider other stimulus conditions, including the effects of context and volition.

  12. Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

    Science.gov (United States)

    Chizhevsky, V. N.

    2018-01-01

    For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

  13. Reflections

    Directory of Open Access Journals (Sweden)

    Joanne Embree

    2001-01-01

    Full Text Available Ideally, editorials are written one to two months before publication in the Journal. It was my turn to write this one. I had planned to write the first draft the evening after my clinic on Tuesday, September 11. It didn't get done that night or during the next week. Somehow, the topic that I had originally chosen just didn't seem that important anymore as I, along my friends and colleagues, reflected on the changes that the events of that day were likely to have on our lives.

  14. In-plane pitch control of cholesteric liquid crystals by formation of artificial domains via patterned photopolymerization.

    Science.gov (United States)

    Yoshida, Hiroyuki; Miura, Yusuke; Tokuoka, Kazuki; Suzuki, Satoshi; Fujii, Akihiko; Ozaki, Masanori

    2008-11-10

    A controlled helix pitch modulation in the in-plane direction of a planarly aligned cholesteric liquid crystal cell is demonstrated by using photopolymerizable cholesteric liquid crystals. By fabricating artificial domains with a closed volume via two-photon excitation laser-lithography, the degree of pitch modulation could be controlled by adjusting the surface area to volume ratio of the domain. A pitch modulation of over 60 nm was realized by designing the shape of the artificial domain.

  15. Energy landscape and dynamics of brain activity during human bistable perception.

    Science.gov (United States)

    Watanabe, Takamitsu; Masuda, Naoki; Megumi, Fukuda; Kanai, Ryota; Rees, Geraint

    2014-08-28

    Individual differences in the structure of parietal and prefrontal cortex predict the stability of bistable visual perception. However, the mechanisms linking such individual differences in brain structures to behaviour remain elusive. Here we demonstrate a systematic relationship between the dynamics of brain activity, cortical structure and behaviour underpinning bistable perception. Using fMRI in humans, we find that the activity dynamics during bistable perception are well described as fluctuating between three spatially distributed energy minimums: visual-area-dominant, frontal-area-dominant and intermediate states. Transitions between these energy minimums predicted behaviour, with participants whose brain activity tend to reflect the visual-area-dominant state exhibiting more stable perception and those whose activity transits to frontal-area-dominant states reporting more frequent perceptual switches. Critically, these brain activity dynamics are correlated with individual differences in grey matter volume of the corresponding brain areas. Thus, individual differences in the large-scale dynamics of brain activity link focal brain structure with bistable perception.

  16. Flexible Bistable Smectic-A Liquid Crystal Device Using Photolithography and Photoinduced Phase Separation

    Directory of Open Access Journals (Sweden)

    Yang Lu

    2012-01-01

    Full Text Available A flexible bistable smectic-A liquid crystal (SmA LC device using pixel-isolated mode was demonstrated, in which SmA LC molecules were isolated in pixels by vertical polymer wall and horizontal polymer layer. The above microstructure was achieved by using ultraviolet (UV photolithography and photoinduced phase separation. The polymer wall was fabricated by photolithography, and then the SmA LC was encapsulated in pixels between polymer wall through UV-induced phase separation, in which the polymer wall acts as supporting structure from mechanical pressure and maintains the cell gap from bending, and the polymer layer acts as adhesive for tight attachment of two substrates. The results demonstrated that all the intrinsic bistable properties of the SmA LC are preserved, and good electrooptical characteristics such as high contrast ratio and excellent stability of the bistable states were characterized. This kind of SmA bistable flexible display has high potential to be used as electronic paper, smart switchable reflective windows, and so forth.

  17. Metastable and bistable defects in silicon

    International Nuclear Information System (INIS)

    Mukashev, Bulat N; Abdullin, Kh A; Gorelkinskii, Yurii V

    2000-01-01

    Existing data on the properties and structure of metastable and bistable defects in silicon are analyzed. Primary radiation-induced defects (vacancies, self-interstitial atoms, and Frenkel pairs), complexes of oxygen, carbon, hydrogen, and other impurity atoms and defects with negative correlation energy are considered. (reviews of topical problems)

  18. Organic bistable light-emitting devices

    Science.gov (United States)

    Ma, Liping; Liu, Jie; Pyo, Seungmoon; Yang, Yang

    2002-01-01

    An organic bistable device, with a unique trilayer structure consisting of organic/metal/organic sandwiched between two outmost metal electrodes, has been invented. [Y. Yang, L. P. Ma, and J. Liu, U.S. Patent Pending, U.S. 01/17206 (2001)]. When the device is biased with voltages beyond a critical value (for example 3 V), the device suddenly switches from a high-impedance state to a low-impedance state, with a difference in injection current of more than 6 orders of magnitude. When the device is switched to the low-impedance state, it remains in that state even when the power is off. (This is called "nonvolatile" phenomenon in memory devices.) The high-impedance state can be recovered by applying a reverse bias; therefore, this bistable device is ideal for memory applications. In order to increase the data read-out rate of this type of memory device, a regular polymer light-emitting diode has been integrated with the organic bistable device, such that it can be read out optically. These features make the organic bistable light-emitting device a promising candidate for several applications, such as digital memories, opto-electronic books, and recordable papers.

  19. A CW Gunn diode bistable switching element.

    Science.gov (United States)

    Hurtado, M.; Rosenbaum, F. J.

    1972-01-01

    Experiments with a current-controlled bistable switching element using a CW Gunn diode are reported. Switching rates of the order of 10 MHz have been obtained. Switching is initiated by current pulses of short duration (5-10 ns). Rise times of the order of several nanoseconds could be obtained.

  20. A bistable model of cell polarity.

    Directory of Open Access Journals (Sweden)

    Matteo Semplice

    Full Text Available Ultrasensitivity, as described by Goldbeter and Koshland, has been considered for a long time as a way to realize bistable switches in biological systems. It is not as well recognized that when ultrasensitivity and reinforcing feedback loops are present in a spatially distributed system such as the cell plasmamembrane, they may induce bistability and spatial separation of the system into distinct signaling phases. Here we suggest that bistability of ultrasensitive signaling pathways in a diffusive environment provides a basic mechanism to realize cell membrane polarity. Cell membrane polarization is a fundamental process implicated in several basic biological phenomena, such as differentiation, proliferation, migration and morphogenesis of unicellular and multicellular organisms. We describe a simple, solvable model of cell membrane polarization based on the coupling of membrane diffusion with bistable enzymatic dynamics. The model can reproduce a broad range of symmetry-breaking events, such as those observed in eukaryotic directional sensing, the apico-basal polarization of epithelium cells, the polarization of budding and mating yeast, and the formation of Ras nanoclusters in several cell types.

  1. Triggered Snap-Through of Bistable Shells

    Science.gov (United States)

    Cai, Yijie; Huang, Shicheng; Trase, Ian; Hu, Nan; Chen, Zi

    Elastic bistable shells are common structures in nature and engineering, such as the lobes of the Venus flytrap or the surface of a toy jumping poppers. Despite their ubiquity, the parameters that control the bistability of such structures are not well understood. In this study, we explore how the geometrical features of radially symmetric elastic shells affect the shape and potential energy of a shell's stable states, and how to tune certain parameters in order to generate a snap-through transition from a convex semi-stable state to concave stable state. We fabricated a series of elastic shells with varying geometric parameters out of silicone rubber and measured the resulting potential energy in the semi-stable state. Finite element simulations were also conducted in order to determine the deformation and stress in the shells during snap-through. It was found that the energy of the semi-stable state is controlled by only two geometric parameters and a dimensionless ratio. We also noted two distinct transitions during snap-through, one between monostability and semi-bistability (the state a popper toy is in before it snaps-through and jumps), and a second transition between semi-bistability and true bistability. This work shows that it is possible to use a set of simple parameters to tailor the energy landscape of an elastic shell in order to generate complex trigger motions for their potential use in smart applications. Z.C. acknowledge support from Society in Science-Branco Weiss Fellowship, administered by ETH Zurich.

  2. Involvement of the visual change detection process in facilitating perceptual alternation in the bistable image.

    Science.gov (United States)

    Urakawa, Tomokazu; Bunya, Mao; Araki, Osamu

    2017-08-01

    A bistable image induces one of two perceptual alternatives. When the bistable visual image is continuously viewed, the percept of the image alternates from one possible percept to the other. Perceptual alternation was previously reported to be induced by an exogenous perturbation in the bistable image, and this perturbation was theoretically interpreted to cause neural noise, prompting a transition between two stable perceptual states. However, little is known experimentally about the visual processing of exogenously driven perceptual alternation. Based on the findings of a previous behavioral study (Urakawa et al. in Perception 45:474-482, 2016), the present study hypothesized that the automatic visual change detection process, which is relevant to the detection of a visual change in a sequence of visual events, has an enhancing effect on the induction of perceptual alternation, similar to neural noise. In order to clarify this issue, we developed a novel experimental paradigm in which visual mismatch negativity (vMMN), an electroencephalographic brain response that reflects visual change detection, was evoked while participants continuously viewed the bistable image. In terms of inter-individual differences in neural and behavioral data, we found that enhancements in the peak amplitude of vMMN1, early vMMN at a latency of approximately 150 ms, correlated with increases in the proportion of perceptual alternation across participants. Our results indicate the involvement of automatic visual change detection in the induction of perceptual alternation, similar to neural noise, thereby providing a deeper insight into the neural mechanisms underlying exogenously driven perceptual alternation in the bistable image.

  3. Structural Color Palettes of Core-Shell Photonic Ink Capsules Containing Cholesteric Liquid Crystals.

    Science.gov (United States)

    Lee, Sang Seok; Seo, Hyeon Jin; Kim, Yun Ho; Kim, Shin-Hyun

    2017-06-01

    Photonic microcapsules with onion-like topology are microfluidically designed to have cholesteric liquid crystals with opposite handedness in their core and shell. The microcapsules exhibit structural colors caused by dual photonic bandgaps, resulting in a rich variety of color on the optical palette. Moreover, the microcapsules can switch the colors from either core or shell depending on the selection of light-handedness. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Bistable scattering in graphene-coated dielectric nanowires.

    Science.gov (United States)

    Li, Rujiang; Wang, Huaping; Zheng, Bin; Dehdashti, Shahram; Li, Erping; Chen, Hongsheng

    2017-06-22

    In nonlinear plasmonics, the switching threshold of optical bistability is limited by the weak nonlinear responses from the conventional Kerr dielectric media. Considering the giant nonlinear susceptibility of graphene, here we develop a nonlinear scattering model under the mean field approximation and study the bistable scattering in graphene-coated dielectric nanowires based on the semi-analytical solutions. We find that the switching intensities of bistable scattering can be smaller than 1 MW cm -2 at the working frequency. To further decrease the switching intensities, we show that the most important factor that restricts the bistable scattering is the relaxation time of graphene. Our work not only reveals some general characteristics of graphene-based bistable scattering, but also provides a guidance to further applications of optical bistability in the high speed all-optical signal processing.

  5. Optical bistability and multistability in polaritonic materials doped with nanoparticles

    International Nuclear Information System (INIS)

    Wang, Zhiping; Yu, Benli

    2014-01-01

    We investigate the optical bistability and multistability in polaritonic materials doped with nanoparticles inside an optical ring cavity. It is found that the optical bistability and multistability can be easily controlled by adjusting the corresponding parameters of the system properly. The effect of the dipole–dipole interaction has also been included in the formulation, which leads to interesting phenomena. Our scheme opens up the possibility of controling the optical bistability and multistability in polaritonic materials doped with nanoparticles. (letter)

  6. Durable bistable auxetics made of rigid solids

    Science.gov (United States)

    Shang, Xiao; Liu, Lu; Rafsanjani, Ahmad; Pasini, Damiano

    2018-02-01

    Bistable Auxetic Metamaterials (BAMs) are a class of monolithic perforated periodic structures with negative Poisson's ratio. Under tension, a BAM can expand and reach a second state of equilibrium through a globally large shape transformation that is ensured by the flexibility of its elastomeric base material. However, if made from a rigid polymer, or metal, BAM ceases to function due to the inevitable rupture of its ligaments. The goal of this work is to extend the unique functionality of the original kirigami architecture of BAM to a rigid solid base material. We use experiments and numerical simulations to assess performance, bistability and durability of rigid BAMs at 10,000 cycles. Geometric maps are presented to elucidate the role of the main descriptors of BAM architecture. The proposed design enables the realization of BAM from a large palette of materials, including elastic-perfectly plastic materials and potentially brittle materials.

  7. Two Bistable Switches Govern M Phase Entry.

    Science.gov (United States)

    Mochida, Satoru; Rata, Scott; Hino, Hirotsugu; Nagai, Takeharu; Novák, Béla

    2016-12-19

    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]. Here, we surprisingly find that Cdk1 auto-activation is dispensable for irreversible, switch-like mitotic entry due to a second mechanism, whereby Cdk1:CycB inhibits its counteracting phosphatase (PP2A:B55). We show that the PP2A:B55-inhibiting Greatwall (Gwl)-endosulfine (ENSA) pathway is both necessary and sufficient for switch-like phosphorylations of mitotic substrates. Using purified components of the Gwl-ENSA pathway in a reconstituted system, we found a sharp Cdk1 threshold for phosphorylation of a luminescent mitotic substrate. The Cdk1 threshold to induce mitotic phosphorylation is distinctly higher than the Cdk1 threshold required to maintain these phosphorylations-evidence for bistability. A combination of mathematical modeling and biochemical reconstitution show that the bistable behavior of the Gwl-ENSA pathway emerges from its mutual antagonism with PP2A:B55. Our results demonstrate that two interlinked bistable mechanisms provide a robust solution for irreversible and switch-like mitotic entry. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Bistable (latching) solenoid actuated propellant isolation valve

    Science.gov (United States)

    Wichmann, H.; Deboi, H. H.

    1979-01-01

    The design, fabrication, assembly and test of a development configuration bistable (latching) solenoid actuated propellant isolation valve suitable for the control hydrazine and liquid fluorine to an 800 pound thrust rocket engine is described. The valve features a balanced poppet, utilizing metal bellows, a hard poppet/seat interface and a flexure support system for the internal moving components. This support system eliminates sliding surfaces, thereby rendering the valve free of self generated particles.

  9. Interlinked bistable mechanisms generate robust mitotic transitions.

    Science.gov (United States)

    Hutter, Lukas H; Rata, Scott; Hochegger, Helfrid; Novák, Béla

    2017-10-18

    The transitions between phases of the cell cycle have evolved to be robust and switch-like, which ensures temporal separation of DNA replication, sister chromatid separation, and cell division. Mathematical models describing the biochemical interaction networks of cell cycle regulators attribute these properties to underlying bistable switches, which inherently generate robust, switch-like, and irreversible transitions between states. We have recently presented new mathematical models for two control systems that regulate crucial transitions in the cell cycle: mitotic entry and exit, 1 and the mitotic checkpoint. 2 Each of the two control systems is characterized by two interlinked bistable switches. In the case of mitotic checkpoint control, these switches are mutually activating, whereas in the case of the mitotic entry/exit network, the switches are mutually inhibiting. In this Perspective we describe the qualitative features of these regulatory motifs and show that having two interlinked bistable mechanisms further enhances robustness and irreversibility. We speculate that these network motifs also underlie other cell cycle transitions and cellular transitions between distinct biochemical states.

  10. Dynamics of unidirectionally coupled bistable Henon maps

    International Nuclear Information System (INIS)

    Sausedo-Solorio, J.M.; Pisarchik, A.N.

    2011-01-01

    We study dynamics of two bistable Henon maps coupled in a master-slave configuration. In the case of coexistence of two periodic orbits, the slave map evolves into the master map state after transients, which duration determines synchronization time and obeys a -1/2 power law with respect to the coupling strength. This scaling law is almost independent of the map parameter. In the case of coexistence of chaotic and periodic attractors, very complex dynamics is observed, including the emergence of new attractors as the coupling strength is increased. The attractor of the master map always exists in the slave map independently of the coupling strength. For a high coupling strength, complete synchronization can be achieved only for the attractor similar to that of the master map. -- Highlights: → We study dynamics of two bistable Henon maps coupled in a master-slave configuration. → Synchronization time for periodic orbits obeys a -1/2 power law with respect to coupling. → For a high coupling strength, the slave map remains bistable. → Complete synchronization can be achieved only when both maps stay at the same attractor.

  11. Steady state statistical correlations predict bistability in reaction motifs.

    Science.gov (United States)

    Chakravarty, Suchana; Barik, Debashis

    2017-03-28

    Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop. We performed stochastic simulations of four feedback regulated models with intrinsic bistability and we show that for a bistable switch with variation of the signal dose, the steady state variance vs. covariance adopts a signatory cusp-shaped curve. Further, we find that the (n + 1)th order cross-cumulant vs. nth order cross-cumulant adopts a closed loop structure for at least n = 3. We also propose that our method is capable of identifying systems without intrinsic bistability even though the system may show bimodality in the marginal response distribution. The proposed method can be used to analyze single cell protein data measured at steady state from experiments such as flow cytometry.

  12. Bubbling and bistability in two parameter discrete systems

    OpenAIRE

    Ambika, G.; Sujatha, N. V.

    2000-01-01

    We present a graphical analysis of the mechanisms underlying the occurrences of bubbling sequences and bistability regions in the bifurcation scenario of a special class of one dimensional two parameter maps. The main result of the analysis is that whether it is bubbling or bistability is decided by the sign of the third derivative at the inflection point of the map function.

  13. Bistable polarization switching in a continuous wave ruby laser

    Science.gov (United States)

    Lawandy, N. M.; Afzal, R. Sohrab

    1988-01-01

    Bistability in the output power, polarization state, and mode volume of an argon-ion laser pumped single mode ruby laser at 6943 A has been observed. The laser operates in a radially confined mode which exhibits hysteresis and bistability only when the pump polarization is parallel to the c-axis.

  14. Bistable soliton states and switching in doubly inhomogeneously ...

    Indian Academy of Sciences (India)

    Dec. 2001 physics pp. 969–979. Bistable soliton states and switching in doubly inhomogeneously doped fiber couplers. AJIT KUMAR. Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India. Abstract. Switching between the bistable soliton states in a doubly and inhomogeneously doped.

  15. Multistability in Bistable Ferroelectric Materials toward Adaptive Applications

    NARCIS (Netherlands)

    Ghosh, Anirban; Koster, Gertjan; Rijnders, Augustinus J.H.M.

    2016-01-01

    Traditionally thermodynamically bistable ferroic materials are used for nonvolatile operations based on logic gates (e.g., in the form of field effect transistors). But, this inherent bistability in these class of materials limits their applicability for adaptive operations. Emulating biological

  16. Optical bistability using quantum interference in V-type atoms

    International Nuclear Information System (INIS)

    Anton, M A; Calderon, Oscar G

    2002-01-01

    The behaviour of a V-type three-level atomic system in a ring cavity driven by a coherent field is studied. We consider a V configuration under conditions such that interference between decay channels is important. We find that when quantum interference is taken into account, optical bistability can be realized with a considerable decrease in the threshold intensity and the cooperative parameter. On the other hand, we also include the finite bandwidth of the driving field and study its role in the optical bistable response. It is found that at certain linewidths of the driving field optical bistability is obtained even if the system satisfies the trapping condition and the threshold intensity can be controlled. Furthermore, a change from the optical bistability due to quantum interference to the usual bistable behaviour based on saturation occurs as the driving field linewidth increases

  17. Auditory event-related potentials associated with perceptual reversals of bistable pitch motion.

    Science.gov (United States)

    Davidson, Gray D; Pitts, Michael A

    2014-01-01

    Previous event-related potential (ERP) experiments have consistently identified two components associated with perceptual transitions of bistable visual stimuli, the "reversal negativity" (RN) and the "late positive complex" (LPC). The RN (~200 ms post-stimulus, bilateral occipital-parietal distribution) is thought to reflect transitions between neural representations that form the moment-to-moment contents of conscious perception, while the LPC (~400 ms, central-parietal) is considered an index of post-perceptual processing related to accessing and reporting one's percept. To explore the generality of these components across sensory modalities, the present experiment utilized a novel bistable auditory stimulus. Pairs of complex tones with ambiguous pitch relationships were presented sequentially while subjects reported whether they perceived the tone pairs as ascending or descending in pitch. ERPs elicited by the tones were compared according to whether perceived pitch motion changed direction or remained the same across successive trials. An auditory reversal negativity (aRN) component was evident at ~170 ms post-stimulus over bilateral fronto-central scalp locations. An auditory LPC component (aLPC) was evident at subsequent latencies (~350 ms, fronto-central distribution). These two components may be auditory analogs of the visual RN and LPC, suggesting functionally equivalent but anatomically distinct processes in auditory vs. visual bistable perception.

  18. On the bistable zone of milling processes.

    Science.gov (United States)

    Dombovari, Zoltan; Stepan, Gabor

    2015-09-28

    A modal-based model of milling machine tools subjected to time-periodic nonlinear cutting forces is introduced. The model describes the phenomenon of bistability for certain cutting parameters. In engineering, these parameter domains are referred to as unsafe zones, where steady-state milling may switch to chatter for certain perturbations. In mathematical terms, these are the parameter domains where the periodic solution of the corresponding nonlinear, time-periodic delay differential equation is linearly stable, but its domain of attraction is limited due to the existence of an unstable quasi-periodic solution emerging from a secondary Hopf bifurcation. A semi-numerical method is presented to identify the borders of these bistable zones by tracking the motion of the milling tool edges as they might leave the surface of the workpiece during the cutting operation. This requires the tracking of unstable quasi-periodic solutions and the checking of their grazing to a time-periodic switching surface in the infinite-dimensional phase space. As the parameters of the linear structural behaviour of the tool/machine tool system can be obtained by means of standard modal testing, the developed numerical algorithm provides efficient support for the design of milling processes with quick estimates of those parameter domains where chatter can still appear in spite of setting the parameters into linearly stable domains. © 2015 The Authors.

  19. Single coil bistable, bidirectional micromechanical actuator

    Science.gov (United States)

    Tabat, Ned; Guckel, Henry

    1998-09-15

    Micromechanical actuators capable of bidirectional and bistable operation can be formed on substrates using lithographic processing techniques. Bistable operation of the microactuator is obtained using a single coil and a magnetic core with a gap. A plunger having two magnetic heads is supported for back and forth linear movement with respect to the gap in the magnetic core, and is spring biased to a neutral position in which the two heads are on each side of the gap in the core. The single electrical coil is coupled to the core and is provided with electrical current to attract one of the heads toward the core by reluctance action to drive the plunger to a limit of travel in one direction. The current is then cut off and the plunger returns by spring action toward the gap, whereafter the current is reapplied to the coil to attract the other head of the plunger by reluctance action to drive the plunger to its other limit of travel. This process can be repeated at a time when switching of the actuator is required.

  20. Deployable structures using bistable reeled composites

    Science.gov (United States)

    Daton-Lovett, Andrew J.; Compton-Bishop, Quentin M.; Curry, Richard G.

    2000-06-01

    This paper describes an innovative, patented use of composite materials developed by RolaTube Technology Ltd. to make smart deployable structures. Bi-stable reeled composites (BRCs) can alternate between two stable forms; that of a strong, rigid structure and that of a compact coil of flat-wound material. Bi-stability arises as a result of the manipulation of Poisson's ratio and isotropy in the various layers of the material. BRCs are made of fiber- reinforced composite materials, most often with a thermoplastic matrix. A range of fibers and polymer matrices can be used according to the requirements of the operating environment. Samples of a BRC structure were constructed using layers of unidirectional, fiber-reinforced thermoplastic sheet with the layers at different angles. The whole assembly was then consolidated under conditions of elevated temperature and pressure. The properties of the BRC are described and the result of a series of experiments performed on the sample to determine the tensile strength of the BRC structure are reported. A full analysis using finite element methods is being undertaken in collaboration with the University of Cambridge, England. The first commercial use has been to fabricate boom and drive mechanisms for the remote inspection of industrial plant.

  1. Spontaneous Formation of left- and right-handed cholesterically ordered domains in an enantioppure chiral polyfluorene film

    NARCIS (Netherlands)

    Savoini, M.; Biagioni, P.; Meskers, S.C.J.; Duò, L.; Hecht, B.; Finazzi, M.

    2011-01-01

    Thermally annealed chiral polyfluorene films are studied by circular differential optical microscopy. We observe the presence of micrometer-sized domains displaying circular dichroism of opposite sign. Our findings suggest the spontaneous occurrence of left- and right-handed cholesterically ordered

  2. Hierarchical bounding structures for efficient virial computations: Towards a realistic molecular description of cholesterics

    Science.gov (United States)

    Tortora, Maxime M. C.; Doye, Jonathan P. K.

    2017-12-01

    We detail the application of bounding volume hierarchies to accelerate second-virial evaluations for arbitrary complex particles interacting through hard and soft finite-range potentials. This procedure, based on the construction of neighbour lists through the combined use of recursive atom-decomposition techniques and binary overlap search schemes, is shown to scale sub-logarithmically with particle resolution in the case of molecular systems with high aspect ratios. Its implementation within an efficient numerical and theoretical framework based on classical density functional theory enables us to investigate the cholesteric self-assembly of a wide range of experimentally relevant particle models. We illustrate the method through the determination of the cholesteric behavior of hard, structurally resolved twisted cuboids, and report quantitative evidence of the long-predicted phase handedness inversion with increasing particle thread angles near the phenomenological threshold value of 45°. Our results further highlight the complex relationship between microscopic structure and helical twisting power in such model systems, which may be attributed to subtle geometric variations of their chiral excluded-volume manifold.

  3. Optothermal Switching of Cholesteric Liquid Crystals: A Study of Azobenzene Derivatives and Laser Wavelengths

    Directory of Open Access Journals (Sweden)

    Tai-Chieh Huang

    2015-09-01

    Full Text Available The laser-initiated thermal (optothermal switching of cholesteric liquid crystals (CLCs is characterized by using different azobenzene (Azo derivatives and laser wavelengths. Under 405-nm laser irradiation, Azo-doped CLCs undergo phase transition from cholesteric to isotropic. No cis-to-trans photoisomerization occurs when the 405-nm laser irradiation is blocked because only a single laser is used. The fast response of Azo-doped CLCs under the on–off switching of the 405-nm laser occurs because of the optothermal effect of the system. The 660-nm laser, which cannot be used as irradiation to generate the trans–cis photoisomerization of Azo, is used in Anthraquinone (AQ-Azo-doped CLCs to examine the optothermal effect of doped Azo. The results show that the LC-like Azo derivative bearing two methyl groups ortho to the Azo moiety (A4 can greatly lower the clearing temperature and generate large amount of heat in AQ-A4-doped CLCs.

  4. Ca++ dependent bistability induced by serotonin in spinal motoneurons

    DEFF Research Database (Denmark)

    Hounsgaard, J.; Kiehn, O.

    1985-01-01

    The plateau potential, responsible for the bistable state of spinal motoneurons, recently described in the decerebrate cat, was suggested to depend on serotonin (Hounsgaard et al. 1984). In an in vitro preparation of the spinal cord of the turtle we now show that serotonin, applied directly...... to the bath, transforms the intrinsic response properties of motoneurons, uncovering a plateau potential and voltage sensitive bistability. The changes induced by serotonin were blocked by Mn++, while the plateau potential and the bistability remained after application of tetrodotoxin. We conclude...... that serotonin controls the expression of a Ca++ dependent plateau potential in motoneurons....

  5. Bistable responses in bacterial genetic networks: Designs and dynamical consequences

    Science.gov (United States)

    Tiwari, Abhinav; Ray, J. Christian J.; Narula, Jatin; Igoshin, Oleg A.

    2011-01-01

    A key property of living cells is their ability to react to stimuli with specific biochemical responses. These responses can be understood through the dynamics of underlying biochemical and genetic networks. Evolutionary design principles have been well studied in networks that display graded responses, with a continuous relationship between input signal and system output. Alternatively, biochemical networks can exhibit bistable responses so that over a range of signals the network possesses two stable steady states. In this review, we discuss several conceptual examples illustrating network designs that can result in a bistable response of the biochemical network. Next, we examine manifestations of these designs in bacterial master-regulatory genetic circuits. In particular, we discuss mechanisms and dynamic consequences of bistability in three circuits: two-component systems, sigma-factor networks, and a multistep phosphorelay. Analyzing these examples allows us to expand our knowledge of evolutionary design principles for networks with bistable responses. PMID:21385588

  6. Bistable luminescence of trivalent rare-earth ions in crystals

    International Nuclear Information System (INIS)

    Sole, Jose Garcia; Ramirez O, Maria de la; Rodenas, Airan; Jaque, Daniel; Bausa, Luisa; Bettinelli, Marco; Speghini, Adolfo; Cavalli, Enrico; Ivleva, Lioudmila

    2006-01-01

    In this work, we have examined three new bistable systems based on the luminescence of three different crystals activated with trivalent rare earth ions. We have focussed our attention on Yb 3+ ions activators, for which the most relevant results are obtained. The first crystal, Sr 0.6 Ba 0.4 Nb 2 O 6 , is a ferroelectric material with a relatively low phase transition temperature (∼370 K), which provides bistability in the luminescence of Yb 3+ ions due to the thermal hysteresis associated with phase transition. The second crystal, LiNbO 3 , provides an intrinsic bistability in the luminescence of Yb 3+ ions, which is driven by changes in the excitation intensity. In the third crystal, NdPO 4 , a new mechanism of excitation intensity driven bistability is obtained when activated with Yb 3+ ions, due to a interplay between the Nd 3+ ↔Yb 3+ energy transfer and back transfer processes

  7. Bifurcation of transition paths induced by coupled bistable systems.

    Science.gov (United States)

    Tian, Chengzhe; Mitarai, Namiko

    2016-06-07

    We discuss the transition paths in a coupled bistable system consisting of interacting multiple identical bistable motifs. We propose a simple model of coupled bistable gene circuits as an example and show that its transition paths are bifurcating. We then derive a criterion to predict the bifurcation of transition paths in a generalized coupled bistable system. We confirm the validity of the theory for the example system by numerical simulation. We also demonstrate in the example system that, if the steady states of individual gene circuits are not changed by the coupling, the bifurcation pattern is not dependent on the number of gene circuits. We further show that the transition rate exponentially decreases with the number of gene circuits when the transition path does not bifurcate, while a bifurcation facilitates the transition by lowering the quasi-potential energy barrier.

  8. Interaction of multiarmed spirals in bistable media.

    Science.gov (United States)

    He, Ya-feng; Ai, Bao-quan; Liu, Fu-cheng

    2013-05-01

    We study the interaction of both dense and sparse multiarmed spirals in bistable media modeled by equations of the FitzHugh-Nagumo type. A dense one-armed spiral is characterized by its fixed tip. For dense multiarmed spirals, when the initial distance between tips is less than a critical value, the arms collide, connect, and disconnect continuously as the spirals rotate. The continuous reconstruction between the front and the back drives the tips to corotate along a rough circle and to meander zigzaggedly. The rotation frequency of tip, the frequency of zigzagged displacement, the frequency of spiral, the oscillation frequency of media, and the number of arms satisfy certain relations as long as the control parameters of the model are fixed. When the initial distance between tips is larger than the critical value, the behaviors of individual arms within either dense or sparse multiarmed spirals are identical to that of corresponding one-armed spirals.

  9. Lattice stretching bistability and dynamic heterogeneity

    DEFF Research Database (Denmark)

    Christiansen, Peter Leth; Savin, A. V.; Zolotaryuk, A. V.

    2012-01-01

    A simple one-dimensional lattice model is suggested to describe the experimentally observed plateau in force-stretching diagrams for some macromolecules. This chain model involves the nearest-neighbor interaction of a Morse-like potential (required to have a saturation branch) and a harmonic second......-neighbor coupling. Under an external stretching applied to the chain ends, the intersite Morse-like potential results in the appearance of a double-well potential within each chain monomer, whereas the interaction between the second neighbors provides a homogeneous bistable (degenerate) ground state, at least...... stretched bonds with a double-well potential. This case allows us to explain the existence of a plateau in the force-extension diagram for DNA and α-helix protein. Finally, the soliton dynamics are studied in detail....

  10. A bistable electromagnetically actuated rotary gate microvalve

    International Nuclear Information System (INIS)

    Luharuka, Rajesh; Hesketh, Peter J

    2008-01-01

    Two types of rotary gate microvalves are developed for flow modulation in microfluidic systems. These microvalves have been tested for an open flow rate of up to 100 sccm and operate under a differential pressure of 6 psig with flow modulation of up to 100. The microvalve consists of a suspended gate that rotates in the plane of the chip to regulate flow through the orifice. The gate is suspended by a novel fully compliant in-plane rotary bistable micromechanism (IPRBM) that advantageously constrains the gate in all degrees of freedom except for in-plane rotational motion. Multiple inlet/outlet orifices provide flexibility of operating the microvalve in three different flow configurations. The rotary gate microvalve is switched with an external electromagnetic actuator. The suspended gate is made of a soft magnetic material and its electromagnetic actuation is based on the operating principle of a variable-reluctance stepper motor

  11. Cops or Robbers — a Bistable Society

    Science.gov (United States)

    Kułakowski, K.

    The norm game described by Axelrod in 1985 was recently treated with the master equation formalism. Here we discuss the equations, where (i) those who break the norm cannot punish and those who punish cannot break the norm, (ii) the tendency to punish is suppressed if the majority breaks the norm. The second mechanism is new. For some values of the parameters the solution shows the saddle-point bifurcation. Then, two stable solutions are possible, where the majority breaks the norm or the majority punishes. This means, that the norm breaking can be discontinuous, when measured in the social scale. The bistable character is reproduced also with new computer simulations on the Erdös-Rényi directed network.

  12. Asymmetric Effects on Escape Rates of Bistable System

    International Nuclear Information System (INIS)

    Wang Canjun; Mei Dongcheng; Dai Zucheng

    2011-01-01

    The asymmetric effects on the escape rates from the stable states x ± in the bistable system are analyzed. The results indicate that the multiplicative noise and the additive noise always enhance the particle escape from stable states x ± of bistable. However, the asymmetric parameter r enhances the particle escape from stable state x + , and holds back the particle escape from stable state x - . (general)

  13. Analytic descriptions of stochastic bistable systems under force ramp.

    Science.gov (United States)

    Friddle, Raymond W

    2016-05-01

    Solving the two-state master equation with time-dependent rates, the ubiquitous driven bistable system, is a long-standing problem that does not permit a complete solution for all driving rates. Here we show an accurate approximation to this problem by considering the system in the control parameter regime. The results are immediately applicable to a diverse range of bistable systems including single-molecule mechanics.

  14. Morphological appearances and photo-controllable coloration of dye-doped cholesteric liquid crystal/polymer coaxial microfibers fabricated by coaxial electrospinning technique.

    Science.gov (United States)

    Lin, Jia-De; Chen, Che-Pei; Chen, Lin-Jer; Chuang, Yu-Chou; Huang, Shuan-Yu; Lee, Chia-Rong

    2016-02-08

    This study systematically investigates the morphological appearance of azo-chiral dye-doped cholesteric liquid crystal (DDCLC)/polymer coaxial microfibers obtained through the coaxial electrospinning technique and examines, for the first time, their photocontrollable reflection characteristics. Experimental results show that the quasi-continuous electrospun microfibers can be successfully fabricated at a high polymer concentration of 17.5 wt% and an optimum ratio of 2 for the feeding rates of sheath to core materials at 25 °C and a high humidity of 50% ± 2% in the spinning chamber. Furthermore, the optical controllability of the reflective features for the electrospun fibers is studied in detail by changing the concentration of the azo-chiral dopant in the core material, the UV irradiation intensity, and the core diameter of the fibers. Relevant mechanisms are addressed to explain the optical-control behaviors of the DDCLC coaxial fibers. Considering the results, optically controllable DDCLC coaxial microfibers present potential applications in UV microsensors and wearable smart textiles or swabs.

  15. Does visual attention drive the dynamics of bistable perception?

    Science.gov (United States)

    Dieter, Kevin C; Brascamp, Jan; Tadin, Duje; Blake, Randolph

    2016-10-01

    How does attention interact with incoming sensory information to determine what we perceive? One domain in which this question has received serious consideration is that of bistable perception: a captivating class of phenomena that involves fluctuating visual experience in the face of physically unchanging sensory input. Here, some investigations have yielded support for the idea that attention alone determines what is seen, while others have implicated entirely attention-independent processes in driving alternations during bistable perception. We review the body of literature addressing this divide and conclude that in fact both sides are correct-depending on the form of bistable perception being considered. Converging evidence suggests that visual attention is required for alternations in the type of bistable perception called binocular rivalry, while alternations during other types of bistable perception appear to continue without requiring attention. We discuss some implications of this differential effect of attention for our understanding of the mechanisms underlying bistable perception, and examine how these mechanisms operate during our everyday visual experiences.

  16. A genetic bistable switch utilizing nonlinear protein degradation.

    Science.gov (United States)

    Huang, Daniel; Holtz, William J; Maharbiz, Michel M

    2012-07-09

    Bistability is a fundamental property in engineered and natural systems, conferring the ability to switch and retain states. Synthetic bistable switches in prokaryotes have mainly utilized transcriptional components in their construction. Using both transcriptional and enzymatic components, creating a hybrid system, allows for wider bistable parameter ranges in a circuit. In this paper, we demonstrate a tunable family of hybrid bistable switches in E. coli using both transcriptional components and an enzymatic component. The design contains two linked positive feedback loops. The first loop utilizes the lambda repressor, CI, and the second positive feedback loop incorporates the Lon protease found in Mesoplasma florum (mf-Lon). We experimentally tested for bistable behavior in exponential growth phase, and found that our hybrid bistable switch was able to retain its state in the absence of an input signal throughout 40 cycles of cell division. We also tested the transient behavior of our switch and found that switching speeds can be tuned by changing the expression rate of mf-Lon. To our knowledge, this work demonstrates the first use of dynamic expression of an orthogonal and heterologous protease to tune a nonlinear protein degradation circuit. The hybrid switch is potentially a more robust and tunable topology for use in prokaryotic systems.

  17. Genes contribute to the switching dynamics of bistable perception.

    Science.gov (United States)

    Shannon, Robert W; Patrick, Christopher J; Jiang, Yi; Bernat, Edward; He, Sheng

    2011-03-09

    Ordinarily, the visual system provides an unambiguous representation of the world. However, at times alternative plausible interpretations of a given stimulus arise, resulting in a dynamic perceptual alternation of the differing interpretations, commonly referred to as bistable or rivalrous perception. Recent research suggests that common neural mechanisms may be involved in the dynamics of very different types of bistable phenomena. Further, evidence has emerged that genetic factors may be involved in determining the rate of switch for at least one form of bistable perception, known as binocular rivalry. The current study evaluated whether genetic factors contribute to the switching dynamics for distinctly different variants of bistable perception in the same participant sample. Switching rates were recorded for MZ and DZ twin participants in two different bistable perception tasks, binocular rivalry and the Necker Cube. Strong concordance in switching rates across both tasks was evident for MZ but not DZ twins, indicating that genetic factors indeed contribute to the dynamics of multiple forms of bistable perception.

  18. Competitive excitation and osmotic-pressure-mediated control of lasing modes in cholesteric liquid crystal microshells

    Science.gov (United States)

    Lin, Ya-Li; Gong, Ling-Li; Che, Kai-Jun; Li, Sen-Sen; Chu, Cheng-Xu; Cai, Zhi-Ping; Yang, Chaoyong James; Chen, Lu-Jian

    2017-05-01

    We examined the end-pumped lasing behaviors of dye doped cholesteric liquid crystal (DDCLC) microshells which were fabricated by glass capillary microfluidics. Several kinds of mode resonances, including distributed feedback, Fabry-Pérot (FP), and whispering gallery (WG) modes, can be robustly constructed in each individual DDCLC microshell by varying the beam diameter, namely, tuning the DDCLC gain area. The FP and WG modes were further confirmed experimentally, and the corresponding lasing mechanisms are clearly revealed from the unique material characteristics of DDCLC and the geometrical structure of the microshell. Additionally, we demonstrated that the osmotic pressure can be used to shrink/expand the microshell, productively tuning the excitation of lasing modes in a controlled manner. We wish our findings can provide a new insight into the design of DDCLC microlasers with tunable optical properties.

  19. Active shape-morphing elastomeric colloids in short-pitch cholesteric liquid crystals.

    Science.gov (United States)

    Evans, Julian S; Sun, Yaoran; Senyuk, Bohdan; Keller, Patrick; Pergamenshchik, Victor M; Lee, Taewoo; Smalyukh, Ivan I

    2013-05-03

    Active elastomeric liquid crystal particles with initial cylindrical shapes are obtained by means of soft lithography and polymerization in a strong magnetic field. Gold nanocrystals infiltrated into these particles mediate energy transfer from laser light to heat, so that the inherent coupling between the temperature-dependent order and shape allows for dynamic morphing of these particles and well-controlled stable shapes. Continuous changes of particle shapes are followed by their spontaneous realignment and transformations of director structures in the surrounding cholesteric host, as well as locomotion in the case of a nonreciprocal shape morphing. These findings bridge the fields of liquid crystal solids and active colloids, may enable shape-controlled self-assembly of adaptive composites and light-driven micromachines, and can be understood by employing simple symmetry considerations along with electrostatic analogies.

  20. Increasing the lasing efficiency in cholesteric liquid-crystal photonic structures

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Shtykov, N M; Barnik, M I; Umanskii, B A [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2010-03-15

    Two types of lasing in cholesteric liquid crystals (LCs) in the range of luminescence of laser dye molecules have been investigated. The first type belongs to the Bragg modes at the photonic band edge, which propagate along the normal to the LC layer. The second type of lasing is related to the modes leaking into the substrate and propagating at small angles to the LC layer. It is shown that the Bragg lasing efficiency can be significantly increased under wide-aperture optical pumping. The method proposed for increasing the lasing efficiency is based on suppressing the excitation of leaky laser modes using partially absorbing thin films as the coatings for LC-orienting substrates. Both experimental results and the theoretical model of the effect using the numerical simulation data are discussed.

  1. Bistable energy harvesting enhancement with an auxiliary linear oscillator

    Science.gov (United States)

    Harne, R. L.; Thota, M.; Wang, K. W.

    2013-12-01

    Recent work has indicated that linear vibrational energy harvesters with an appended degree-of-freedom (DOF) may be advantageous for introducing new dynamic forms to extend the operational bandwidth. Given the additional interest in bistable harvester designs, which exhibit a propitious snap through effect from one stable state to the other, it is a logical extension to explore the influence of an added DOF to a bistable system. However, bistable snap through is not a resonant phenomenon, which tempers the presumption that the dynamics induced by an additional DOF on bistable designs would inherently be beneficial as for linear systems. This paper presents two analytical formulations to assess the fundamental and superharmonic steady-state dynamics of an excited bistable energy harvester to which is attached an auxiliary linear oscillator. From an energy harvesting perspective, the model predicts that the additional linear DOF uniformly amplifies the bistable harvester response magnitude and generated power for excitation frequencies less than the attachment’s resonance while improved power density spans a bandwidth below this frequency. Analyses predict bandwidths having co-existent responses composed of a unique proportion of fundamental and superharmonic dynamics. Experiments validate key analytical predictions and observe the ability for the coupled system to develop an advantageous multi-harmonic interwell response when the initial conditions are insufficient for continuous high-energy orbit at the excitation frequency. Overall, the addition of an auxiliary linear oscillator to a bistable harvester is found to be an effective means of enhancing the energy harvesting performance and robustness.

  2. Design methodology for all-optical bistable switches based on a plasmonic resonator sandwiched between dielectric waveguides

    International Nuclear Information System (INIS)

    Xiang, Yinxiao; Cai, Wei; Wang, Lei; Ying, Cuifeng; Zhang, Xinzheng; Xu, Jingjun

    2014-01-01

    We present a bistable device consisting of a Bragg grating resonator with a Kerr medium sandwiched between two dielectric slab waveguides. The resonator is situated in a nanometer-scaled metal–insulator–metal plasmonic waveguide. Due to the dimensional confinement from the dielectric waveguide to the nanoscaled plasmonic waveguide, electric fields are enhanced greatly, which will further reduce the threshold value. Moreover, a semi-analytic method, based on the impedance theory and the transfer matrix method, is developed to study the transmission and reflection spectra as well as the bistability loop of such a switch. Our method is fast and accurate, as confirmed by the finite-difference time-domain simulation. (invited paper)

  3. Bistable behaviour of biexciton population in a dense exciton-biexciton system in semiconductors

    International Nuclear Information System (INIS)

    Nguyen Ba An.

    1986-05-01

    The steady state bistable behaviour of biexciton population in a dense exciton-biexciton semiconductor is considered. The intrinsic optical feedback is provided by the recombination mechanism. The exciton-biexciton and biexciton-biexciton interactions play the role of non-linearity responsible for biexciton bistability to occur. The conditions leading to the effect of bistability are obtained and two-parameter phase transition diagrams are drawn for both intensity and frequency bistable phenomena. (author)

  4. Optical bistability induced by quantum coherence in a negative index atomic medium

    International Nuclear Information System (INIS)

    Zhang Hong-Jun; Sun Hui; Li Jin-Ping; Yin Bao-Yin; Guo Hong-Ju

    2013-01-01

    Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated. It is found that the optical bistability can appear in the negative refraction frequency band, while both the bistability and multi-stability can occur in the positive refraction frequency bands. Therefore, optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  5. Evaluation of bistable systems versus matched filters in detecting bipolar pulse signals

    OpenAIRE

    Duan, Fabing; Abbott, Derek; Gao, Qisheng

    2004-01-01

    This paper presents a thorough evaluation of a bistable system versus a matched filter in detecting bipolar pulse signals. The detectability of the bistable system can be optimized by adding noise, i.e. the stochastic resonance (SR) phenomenon. This SR effect is also demonstrated by approximate statistical detection theory of the bistable system and corresponding numerical simulations. Furthermore, the performance comparison results between the bistable system and the matched filter show that...

  6. Bistability and Biofilm Formation in Bacillus subtilis

    Science.gov (United States)

    Chai, Yunrong; Chu, Frances; Kolter, Roberto; Losick, Richard

    2008-01-01

    Summary Biofilms of Bacillus subtilis consist of long chains of cells that are held together in bundles by an extracellular matrix of exopolysaccharide and the protein TasA. The exopolysaccharide is produced by enzymes encoded by the epsA-O operon and the gene encoding TasA is located in the yqxM-sipW-tasA operon. Both operons are under the control of the repressor SinR. Derepression is mediated by the antirepressor SinI, which binds to SinR with a 1:1 stoichiometry. Paradoxically, in medium promoting derepression of the matrix operons, the overall concentration of SinR in the culture greatly exceeded that of SinI. We show that under biofilm-promoting conditions sinI, which is under the control of the response regulator Spo0A, was expressed only in a small subpopulation of cells, whereas sinR was expressed in almost all cells. Activation of Spo0A is known to be subject to a bistable switch, and we infer that SinI reaches levels sufficient to trigger matrix production only in the subpopulation of cells in which Spo0A is active. Additionally, evidence suggests that sinI is expressed at intermediate, but not low or high, levels of Spo0A activity, which may explain why certain nutritional conditions are more effective in promoting biofilm formation than others. PMID:18047568

  7. Bistability of mangrove forests and competition with freshwater plants

    Science.gov (United States)

    Jiang, Jiang; Fuller, Douglas O; Teh, Su Yean; Zhai, Lu; Koh, Hock Lye; DeAngelis, Donald L.; Sternberg, L.D.S.L.

    2015-01-01

    Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.

  8. Fundamental role of bistability in optimal homeostatic control

    Science.gov (United States)

    Wang, Guanyu

    2013-03-01

    Bistability is a fundamental phenomenon in nature and has a number of fine properties. However, these properties are consequences of bistability at the physiological level, which do not explain why it had to emerge during evolution. Using optimal homeostasis as the first principle and Pontryagin's Maximum Principle as the optimization approach, I find that bistability emerges as an indispensable control mechanism. Because the mathematical model is general and the result is independent of parameters, it is likely that most biological systems use bistability to control homeostasis. Glucose homeostasis represents a good example. It turns out that bistability is the only solution to a dilemma in glucose homeostasis: high insulin efficiency is required for rapid plasma glucose clearance, whereas an insulin sparing state is required to guarantee the brain's safety during fasting. This new perspective can illuminate studies on the twin epidemics of obesity and diabetes and the corresponding intervening strategies. For example, overnutrition and sedentary lifestyle may represent sudden environmental changes that cause the lose of optimality, which may contribute to the marked rise of obesity and diabetes in our generation.

  9. Dynamic control of a bistable wing under aerodynamic loading

    International Nuclear Information System (INIS)

    Bilgen, Onur; Arrieta, Andres F; Friswell, Michael I; Hagedorn, Peter

    2013-01-01

    The aerodynamic evaluation of a dynamic control technique applied to a bistable unsymmetrical cross-ply composite plate with surface bonded piezoelectric actuators is presented. The plate is clamped on one end to form a low-aspect-ratio wing. A previously proposed dynamic control method, utilizing bending resonance in different stable equilibrium positions, is used to induce snap-through between the two equilibrium states. Compared to quasi-static actuation, driving the bistable plate near resonance using surface bonded piezoelectric materials requires, theoretically, a lower peak excitation voltage to achieve snap-through. First, a set of extensive wind tunnel experiments are conducted on the passive bistable wing to understand the change in the dynamic behavior under various aerodynamic conditions. The passive wing demonstrated sufficient bending stiffness to sustain its shape under aerodynamic loading while preserving the desired bistable behavior. Next, by the use of the resonant control technique, the plate is turned into an effectively monostable structure, or alternatively, both stable equilibrium positions can be reached actively from the other stable equilibrium. Dynamic forward and reverse snap-through is demonstrated in the wind tunnel which shows both the effectiveness of the piezoelectric actuation as well as the load carrying capability of both states of the bistable wing. (paper)

  10. Oscillations in the bistable regime of neuronal networks.

    Science.gov (United States)

    Roxin, Alex; Compte, Albert

    2016-07-01

    Bistability between attracting fixed points in neuronal networks has been hypothesized to underlie persistent activity observed in several cortical areas during working memory tasks. In network models this kind of bistability arises due to strong recurrent excitation, sufficient to generate a state of high activity created in a saddle-node (SN) bifurcation. On the other hand, canonical network models of excitatory and inhibitory neurons (E-I networks) robustly produce oscillatory states via a Hopf (H) bifurcation due to the E-I loop. This mechanism for generating oscillations has been invoked to explain the emergence of brain rhythms in the β to γ bands. Although both bistability and oscillatory activity have been intensively studied in network models, there has not been much focus on the coincidence of the two. Here we show that when oscillations emerge in E-I networks in the bistable regime, their phenomenology can be explained to a large extent by considering coincident SN and H bifurcations, known as a codimension two Takens-Bogdanov bifurcation. In particular, we find that such oscillations are not composed of a stable limit cycle, but rather are due to noise-driven oscillatory fluctuations. Furthermore, oscillations in the bistable regime can, in principle, have arbitrarily low frequency.

  11. Non-resonant energy harvesting via an adaptive bistable potential

    International Nuclear Information System (INIS)

    Hosseinloo, Ashkan Haji; Turitsyn, Konstantin

    2016-01-01

    Narrow bandwidth and easy detuning, inefficiency in broadband and non-stationary excitations, and difficulties in matching a linear harvester’s resonance frequency to low-frequency excitations at small scales, have convinced researchers to investigate nonlinear, and in particular bistable, energy harvesters in recent years. However, bistable harvesters suffer from co-existing low and high energy orbits, and sensitivity to initial conditions, and have recently been proven inefficient when subjected to many real-world random and non-stationary excitations. Here, we propose a novel non-resonant buy-low-sell-high strategy that can significantly improve the harvester’s effectiveness at low frequencies in a much more robust fashion. This strategy could be realized by a passive adaptive bistable system. Simulation results confirm the high effectiveness of the adaptive bistable system following a buy-low-sell-high logic when subjected to harmonic and random non-stationary walking excitations compared to its conventional bistable and linear counterparts. (paper)

  12. Chaos in a new bistable rotating electromechanical system

    International Nuclear Information System (INIS)

    Tsapla Fotsa, R.; Woafo, P.

    2016-01-01

    Highlights: • A new electromechanical system with rotating arm and bistable potential energy is studied. • The bistability is generated by the interaction of three permanent magnets, one fixed at the end of the arm and two other fixed at equal distance relative to the central position of the arm. • It exhibits dissipative and Hamiltonian chaos. • Such a bistable electromechanical system can be used as the actuation part of chaotic sieves and mixers. - Abstract: A device consisting of an induction motor activating a rotating rigid arm is designed and comprises a bistable potential due to the presence of three permanent magnets. Its mathematical equations are established and the numerical results both in the absence and in the presence of magnets are compared. The generation of chaotic behavior is achieved using two different external excitations: sinewave and square wave. In the presence of magnets, the system presents periodic and dissipative chaotic dynamics. Approximating the global potential energy to a bistable quartic potential, the Melnikov method is used to derive the conditions for the appearance of Hamiltonian chaos. Such a device can be used for industrial and domestic applications for mixing and sieving activities.

  13. Numerical and experimental study of bistable plates for morphing structures

    Science.gov (United States)

    Nicassio, F.; Scarselli, G.; Avanzini, G.; Del Core, G.

    2017-04-01

    This study is concerned with the activation energy threshold of bistable composite plates in order to tailor a bistable system for specific aeronautical applications. The aim is to explore potential configurations of the bistable plates and their dynamic behavior for designing novel morphing structure suitable for aerodynamic surfaces and, as a possible further application, for power harvesters. Bistable laminates have two stable mechanical shapes that can withstand aerodynamic loads without additional constraint forces or locking mechanisms. This kind of structures, when properly loaded, snap-through from one stable configuration to another, causing large strains that can also be used for power harvesting scopes. The transition between the stable states of the composite laminate can be triggered, in principle, simply by aerodynamic loads (pilot, disturbance or passive inputs) without the need of servo-activated control systems. Both numerical simulations based on Finite Element models and experimental testing based on different activating forcing spectra are used to validate this concept. The results show that dynamic activation of bistable plates depend on different parameters that need to be carefully managed for their use as aircraft passive wing flaps.

  14. A bistable mechanism for chord extension morphing rotors

    Science.gov (United States)

    Johnson, Terrence; Frecker, Mary; Gandhi, Farhan

    2009-03-01

    Research efforts have shown that helicopter rotor blade morphing is an effective means to improve flight performance. Previous example of rotor blade morphing include using smart-materials for trailing deflection and rotor blade twist and tip twist, the development of a comfortable airfoil using compliant mechanisms, the use of a Gurney flap for air-flow deflection and centrifugal force actuated device to increase the span of the blade. In this paper we explore the use of a bistable mechanism for rotor morphing, specifically, blade chord extension using a bistable arc. Increasing the chord of the rotor blade is expected to generate more lift-load and improve helicopter performance. Bistable or "snap through" mechanisms have multiple stable equilibrium states and are a novel way to achieve large actuation output stroke. Bistable mechanisms do not require energy input to maintain a stable equilibrium state as both states do not require locking. In this work, we introduce a methodology for the design of bistable arcs for chord morphing using the finite element analysis and pseudo-rigid body model, to study the effect of different arc types, applied loads and rigidity on arc performance.

  15. Active thermal fine laser tuning in a broad spectral range and optical properties of cholesteric liquid crystal.

    Science.gov (United States)

    Jeong, Mi-Yun; Kwak, Keumcheol

    2016-11-20

    In this study, we achieved active fine laser tuning in a broad spectral range with dye-doped cholesteric liquid crystal wedge-type cells through temperature control. The spatial pitch gradient of each position of the wedge cell at room temperature was almost maintained after developing a temperature gradient. To achieve the maximum tuning range, the chiral dopant concentration, thickness, thickness gradient, and temperature gradient on the wedge cell should be matched properly. In order to understand the laser tuning mechanism for temperature change, we studied the temperature dependence of optical properties of the photonic bandgap of cholesteric liquid crystals. In our cholesteric liquid crystal samples, when temperature was increased, photonic bandgaps were shifted toward blue, while the width of the photonic bandgap was decreased, regardless of whether the helicity was left-handed or right-handed. This is mainly due to the combination of decreased refractive indices, higher molecular anisotropy of chiral molecules, and increased chiral molecular solubility. We envisage that this kind of study will prove useful in the development of practical active tunable CLC laser devices.

  16. The derivation of a bistable criterion for double V-beam mechanisms

    International Nuclear Information System (INIS)

    Wu, Cho-Chun; Chen, Rongshun; Lin, Meng-Ju

    2013-01-01

    This study presents the theoretical derivation of the discriminant D as a structural and material criterion for determining whether bistability can occur in micromechanically bistable mechanisms. When D < 0, the mechanism displays bistable behavior if an appropriate force is applied to push the bistable mechanism, whereas when D > 0, bistable behavior cannot occur. The proposed V-beam bistable mechanism was successfully fabricated with various beam lengths and tilted angles. The experiments conducted in this study validated the theoretical study of bistability. A comparison of the theoretical solutions and experimental results shows good agreement. Results further show that to design a bistable V-beam mechanism, the tilted angle should be larger for the same beam length, whereas the beam length should be longer for the same tilted angle. The developed discriminant D can be used to predict if a bistable mechanism can achieve bistable behavior based on structural sizes and material properties. Consequently, researchers can reduce trial-and-error experiments when designing a bistable mechanism. A V-beam with a larger tilted angle of up to 5° was successfully fabricated to act as a bistable mechanism, compared to a 3.5° tilted angle in existing studies. Consequently, the proposed method has the advantages of shorter beam lengths and smaller device areas. (paper)

  17. Bistable near field and bistable transmittance in 2D composite slab consisting of nonlocal core-Kerr shell inclusions.

    Science.gov (United States)

    Huang, Yang; Wu, Ya Min; Gao, Lei

    2017-01-23

    We carry out a theoretical study on optical bistability of near field intensity and transmittance in two-dimensional nonlinear composite slab. This kind of 2D composite is composed of nonlocal metal/Kerr-type dielectric core-shell inclusions randomly embedded in the host medium, and we derivate the nonlinear relation between the field intensity in the shell of inclusions and the incident field intensity with self-consistent mean field approximation. Numerical demonstration has been performed to show the viable parameter space for the bistable near field. We show that nonlocality can provide broader region in geometric parameter space for bistable near field as well as bistable transmittance of the nonlocal composite slab compared to local case. Furthermore, we investigate the bistable transmittance in wavelength spectrum, and find that besides the input intensity, the wavelength operation could as well make the transmittance jump from a high value to a low one. This kind of self-tunable nano-composite slab might have potential application in optical switching devices.

  18. Optical Bistability in Graded Core-Shell Granular Composites

    International Nuclear Information System (INIS)

    Wu Ya-Min; Chen Guo-Qing; Xue Si-Zhong; Zhu Zhuo-Wei; Ma Chao-Qun

    2012-01-01

    The intrinsic optical bistability (OB) of graded core-shell granular composites is investigated. The coated particles are made of cores with gradient dielectric function in c (r) = A(r/a) k and nonlinear shells. In view of the exponential distribution of the core dielectric constant, the potential functions of each region are obtained by solving the Maxwell equations, and the mathematical expressions of electric field in the shells and cores are determined. Numerical study reveals that the optical bistable threshold and the threshold width of the composite medium are dependent on the shell thickness, core dielectric exponent, and power function coefficient. The optical bistable width increases with the decreasing shell thickness and the power exponent and with the increasing power function coefficient

  19. Design of a bistable switch to control cellular uptake.

    Science.gov (United States)

    Oyarzún, Diego A; Chaves, Madalena

    2015-12-06

    Bistable switches are widely used in synthetic biology to trigger cellular functions in response to environmental signals. All bistable switches developed so far, however, control the expression of target genes without access to other layers of the cellular machinery. Here, we propose a bistable switch to control the rate at which cells take up a metabolite from the environment. An uptake switch provides a new interface to command metabolic activity from the extracellular space and has great potential as a building block in more complex circuits that coordinate pathway activity across cell cultures, allocate metabolic tasks among different strains or require cell-to-cell communication with metabolic signals. Inspired by uptake systems found in nature, we propose to couple metabolite import and utilization with a genetic circuit under feedback regulation. Using mathematical models and analysis, we determined the circuit architectures that produce bistability and obtained their design space for bistability in terms of experimentally tuneable parameters. We found an activation-repression architecture to be the most robust switch because it displays bistability for the largest range of design parameters and requires little fine-tuning of the promoters' response curves. Our analytic results are based on on-off approximations of promoter activity and are in excellent qualitative agreement with simulations of more realistic models. With further analysis and simulation, we established conditions to maximize the parameter design space and to produce bimodal phenotypes via hysteresis and cell-to-cell variability. Our results highlight how mathematical analysis can drive the discovery of new circuits for synthetic biology, as the proposed circuit has all the hallmarks of a toggle switch and stands as a promising design to control metabolic phenotypes across cell cultures. © 2015 The Author(s).

  20. Excitonic bistabilities, instabilities and chaos in laser-pumped semiconductor

    International Nuclear Information System (INIS)

    Nguyen Ba An; Nguyen Trung Dan; Hoang Xuan Nguyen

    1992-07-01

    The Hurwitz criteria are used for a stability analysis of the steady state excitonic optical bistability curves in a semiconductor pumped by an external laser resonant with the exciton level. Besides the middle branch of the bistability curves which is unstable in the sense of the linear stability theory, we have found other domains of instability in the upper and lower branches of the steady state curves. Numerical results show that a possible route to chaos in the photon-exciton system is period-doubling self-oscillation process. The influence of the presence of free carriers that coexist with the excitons is also discussed. (author). 16 refs, 6 figs

  1. Large-Scale Analysis of Network Bistability for Human Cancers

    Science.gov (United States)

    Shiraishi, Tetsuya; Matsuyama, Shinako; Kitano, Hiroaki

    2010-01-01

    Protein–protein interaction and gene regulatory networks are likely to be locked in a state corresponding to a disease by the behavior of one or more bistable circuits exhibiting switch-like behavior. Sets of genes could be over-expressed or repressed when anomalies due to disease appear, and the circuits responsible for this over- or under-expression might persist for as long as the disease state continues. This paper shows how a large-scale analysis of network bistability for various human cancers can identify genes that can potentially serve as drug targets or diagnosis biomarkers. PMID:20628618

  2. An Optically Driven Bistable Janus Rotor with Patterned Metal Coatings.

    Science.gov (United States)

    Zong, Yiwu; Liu, Jing; Liu, Rui; Guo, Honglian; Yang, Mingcheng; Li, Zhiyuan; Chen, Ke

    2015-11-24

    Bistable rotation is realized for a gold-coated Janus colloidal particle in an infrared optical trap. The metal coating on the Janus particles are patterned by sputtering gold on a monolayer of closely packed polystyrene particles. The Janus particle is observed to stably rotate in an optical trap. Both the direction and the rate of rotation can be experimentally controlled. Numerical calculations reveal that the bistable rotation is the result of spontaneous symmetry breaking induced by the uneven curvature of the coating patterns on the Janus sphere. Our results thus provide a simple method to construct large quantities of fully functional rotary motors for nano- or microdevices.

  3. Excitonic optical bistability in n-type doped semiconductors

    International Nuclear Information System (INIS)

    Nguyen Ba An; Le Thi Cat Tuong

    1991-07-01

    A resonant monochromatic pump laser generates coherent excitons in an n-type doped semiconductor. Both exciton-exciton and exciton-donor interactions come into play. The former interaction can give rise to the appearance of optical bistability which is heavily influenced by the latter one. When optical bistability occurs at a fixed laser frequency both its holding intensity and hysteresis loop size are shown to decrease with increasing donor concentration. Two possibilities are suggested for experimentally determining one of the two parameters of the system - the exciton-donor coupling constant and the donor concentration, if the other parameter is known beforehand. (author). 36 refs, 2 figs

  4. The Necker-Zeno model for bistable perception.

    Science.gov (United States)

    Atmanspacher, Harald; Filk, Thomas

    2013-10-01

    A novel conceptual framework for theoretical psychology is presented and illustrated for the example of bistable perception. A basic formal feature of this framework is the non-commutativity of operations acting on mental states. A corresponding model for the bistable perception of ambiguous stimuli, the Necker-Zeno model, is sketched and some empirical evidence for it so far is described. It is discussed how a temporal non-locality of mental states, predicted by the model, can be understood and tested. © 2013 Cognitive Science Society, Inc.

  5. THE DENSITY DISTRIBUTION IN TURBULENT BISTABLE FLOWS

    International Nuclear Information System (INIS)

    Gazol, Adriana; Kim, Jongsoo

    2013-01-01

    We numerically study the volume density probability distribution function (n-PDF) and the column density probability distribution function (Σ-PDF) resulting from thermally bistable turbulent flows. We analyze three-dimensional hydrodynamic models in periodic boxes of 100 pc by side, where turbulence is driven in the Fourier space at a wavenumber corresponding to 50 pc. At low densities (n ∼ –3 ), the n-PDF is well described by a lognormal distribution for an average local Mach number ranging from ∼0.2 to ∼5.5. As a consequence of the nonlinear development of thermal instability (TI), the logarithmic variance of the distribution of the diffuse gas increases with M faster than in the well-known isothermal case. The average local Mach number for the dense gas (n ∼> 7.1 cm –3 ) goes from ∼1.1 to ∼16.9 and the shape of the high-density zone of the n-PDF changes from a power law at low Mach numbers to a lognormal at high M values. In the latter case, the width of the distribution is smaller than in the isothermal case and grows slower with M. At high column densities, the Σ-PDF is well described by a lognormal for all of the Mach numbers we consider and, due to the presence of TI, the width of the distribution is systematically larger than in the isothermal case but follows a qualitatively similar behavior as M increases. Although a relationship between the width of the distribution and M can be found for each one of the cases mentioned above, these relations are different from those of the isothermal case.

  6. Electrical bistabilities and memory stabilities of nonvolatile bistable devices fabricated utilizing C60 molecules embedded in a polymethyl methacrylate layer

    International Nuclear Information System (INIS)

    Cho, Sung Hwan; Lee, Dong Ik; Jung, Jae Hun; Kim, Tae Whan

    2009-01-01

    Current-voltage (I-V) measurements on Al/fullerene (C 60 ) molecules embedded in polymethyl methacrylate/Al devices at 300 K showed a current bistability due to the existence of the C 60 molecules. The on/off ratio of the current bistability for the memory devices was as large as 10 3 . The retention time of the devices was above 2.5 x 10 4 s at room temperature, and cycling endurance tests on these devices indicated that the ON and OFF currents showed no degradation until 50 000 cycles. Carrier transport mechanisms for the nonvolatile bistable devices are described on the basis of the I-V experimental and fitting results.

  7. Alternans by non-monotonic conduction velocity restitution, bistability and memory

    International Nuclear Information System (INIS)

    Kim, Tae Yun; Hong, Jin Hee; Heo, Ryoun; Lee, Kyoung J

    2013-01-01

    Conduction velocity (CV) restitution is a key property that characterizes any medium supporting traveling waves. It reflects not only the dynamics of the individual constituents but also the coupling mechanism that mediates their interaction. Recent studies have suggested that cardiac tissues, which have a non-monotonic CV-restitution property, can support alternans, a period-2 oscillatory response of periodically paced cardiac tissue. This study finds that single-hump, non-monotonic, CV-restitution curves are a common feature of in vitro cultures of rat cardiac cells. We also find that the Fenton–Karma model, one of the well-established mathematical models of cardiac tissue, supports a very similar non-monotonic CV restitution in a physiologically relevant parameter regime. Surprisingly, the mathematical model as well as the cell cultures support bistability and show cardiac memory that tends to work against the generation of an alternans. Bistability was realized by adopting two different stimulation protocols, ‘S1S2’, which produces a period-1 wave train, and ‘alternans-pacing’, which favors a concordant alternans. Thus, we conclude that the single-hump non-monotonicity in the CV-restitution curve is not sufficient to guarantee a cardiac alternans, since cardiac memory interferes and the way the system is paced matters. (paper)

  8. Bistable flow spectral analysis. Repercussions on jet pumps

    International Nuclear Information System (INIS)

    Gavilan Moreno, C.J.

    2011-01-01

    Highlights: → The most important thing in this paper, is the spectral characterization of the bistable flow in a Nuclear Power Plant. → This paper goes deeper in the effect of the bistable flow over the jet pump and the induced vibrations. → The jet pump frequencies are very close to natural jet pump frequencies, in the 3rd and 6th mode. - Abstract: There have been many attempts at characterizing and predicting bistable flow in boiling water reactors (BWRs). Nevertheless, in most cases the results have only managed to develop models that analytically reproduce the phenomenon (). Modeling has been forensic in all cases, while the capacity of the model focus on determining the exclusion areas on the recirculation flow map. The bistability process is known by its effects given there is no clear definition of its causal process. In the 1980s, Hitachi technicians () managed to reproduce bistable flow in the laboratory by means of pipe geometry, similar to that which is found in recirculation loops. The result was that the low flow pattern is formed by the appearance of a quasi stationary, helicoidal vortex in the recirculation collector's branches. This vortex creates greater frictional losses than regions without vortices, at the same discharge pressure. Neither the behavior nor the dynamics of these vortices were characterized in this paper. The aim of this paper is to characterize these vortices in such a way as to enable them to provide their own frequencies and their later effect on the jet pumps. The methodology used in this study is similar to the one used previously when analyzing the bistable flow in tube arrays with cross flow (). The method employed makes use of the power spectral density function. What differs is the field of application. We will analyze a Loop B with a bistable flow and compare the high and low flow situations. The same analysis will also be carried out on the loop that has not developed the bistable flow (Loop A) at the same moments

  9. Two optical bistability domains in composites of metal nanoparticles with nonlinear dielectric core

    Energy Technology Data Exchange (ETDEWEB)

    Shewamare, Sisay, E-mail: sisayshewa20@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia); Mal' nev, V.N., E-mail: vadimnmalnev@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia)

    2012-12-15

    It is shown that the local field in metal spherical particles with a dielectric core in an external varying electric field has two maxima at two different frequencies. The second maximum becomes more important with an increment in the metal fraction. Due to the nonlinear dielectric function of the core, the composite of these inclusions may have two optically induced bistability domains at different frequencies. At rather high metal fraction, two bistability domains merge and form one entire bistability domain. The parameters of these domains are studied numerically. The paper focuses on the second bistability domain, which has not been discussed in the literature so far. This domain exists in a comparatively narrow frequency range and its onset fields are lower than those of the first bistability domain. The lowest bistability onset fields are obtained in the entire domain. This peculiarity of the optical induced bistability in the metal composite with small dielectric cores can be attractive for possible applications.

  10. Controllable optical bistability in a three-mode optomechanical system with atom-cavity-mirror couplings

    Science.gov (United States)

    Chen, Bin; Wang, Xiao-Fang; Yan, Jia-Kai; Zhu, Xiao-Fei; Jiang, Cheng

    2018-01-01

    We theoretically investigate the optical bistable behavior in a three-mode optomechanical system with atom-cavity-mirror couplings. The effects of the cavity-pump detuning and the pump power on the bistable behavior are discussed detailedly, the impacts of the atom-pump detuning and the atom-cavity coupling strength on the bistability of the system are also explored, and the influences of the cavity-resonator coupling strength and the cavity decay rate are also taken into consideration. The numerical results demonstrate that by tuning these parameters the bistable behavior of the system can be freely switched on or off, and the threshold of the pump power for the bistability as well as the bistable region width can also be effectively controlled. These results can find potential applications in optical bistable switch in the quantum information processing.

  11. Two optical bistability domains in composites of metal nanoparticles with nonlinear dielectric core

    International Nuclear Information System (INIS)

    Shewamare, Sisay; Mal'nev, V.N.

    2012-01-01

    It is shown that the local field in metal spherical particles with a dielectric core in an external varying electric field has two maxima at two different frequencies. The second maximum becomes more important with an increment in the metal fraction. Due to the nonlinear dielectric function of the core, the composite of these inclusions may have two optically induced bistability domains at different frequencies. At rather high metal fraction, two bistability domains merge and form one entire bistability domain. The parameters of these domains are studied numerically. The paper focuses on the second bistability domain, which has not been discussed in the literature so far. This domain exists in a comparatively narrow frequency range and its onset fields are lower than those of the first bistability domain. The lowest bistability onset fields are obtained in the entire domain. This peculiarity of the optical induced bistability in the metal composite with small dielectric cores can be attractive for possible applications.

  12. Upgrading the Performance of Cholesteric Liquid Crystal Lasers: Improvement Margins and Limitations

    Directory of Open Access Journals (Sweden)

    Josu Ortega

    2017-12-01

    Full Text Available The topic of cholesteric-liquid-crystal lasers is a rapidly expanding research area in the field of soft-matter photonics. The increasing interest in this field is due to the high versatility that these lasers may possibly present and the prospects of giving rise to new miniaturized devices. However, further improvements in their operation capabilities are still required for potential applications. In this paper, we critically analyze the main strategies proposed up to now to optimize their performance. We show theoretically and experimentally that possible innovations in the device structure cannot produce lasers with threshold energies below a certain limit. This limit is determined by the light scattering and absorption losses inside the liquid crystal. Even assuming the case of samples free of defects and perfectly non-absorbing, an intrinsic light scattering, typical of mesogens, still remains. Numerical estimates of the thresholds indicate that these lasers could hardly be driven by compact light sources such as current electroluminescent or light-emitting diodes. Since the improvement possibilities regarding cell architecture seem to be exhausted, the advance must come from the use of new dye molecules. These molecules should show enhanced emission cross-sections and be efficiently integrable within the mesogenic solvent. In addition, the fluorescent systems must present very small quantum yields to triplet states if continuous-wave lasing is sought. In this respect, quantum dots are an alternative to explore for further investigations.

  13. Dynamic cholesteric liquid crystal superstructures photoaligned by one-step polarization holography

    Science.gov (United States)

    Li, Sen-Sen; Shen, Yuan; Chang, Zhen-Ni; Li, Wen-Song; Xu, Yan-Chao; Fan, Xing-Yu; Chen, Lu-Jian

    2017-12-01

    A convenient approach to modulate the fingerprint textures of methyl red (MR) doped cholesteric liquid crystals by asymmetric photoalignment in the green-light waveband is presented, resulting in the generation of voltage-controllable helical superstructures. The interaction between the MR molecules and the incident light polarization determines the initial twisted planar geometry, providing a multivariant control over the stripe directions of fingerprint textures by applying a proper electric field. The key factors for precise manipulation of fingerprint stripes in a predictable and rewritable manner are analyzed theoretically and investigated experimentally, which involves the alignment asymmetry, the ratio of cell gap to natural pitch length, and the chirality of chiral dopant. Dynamic periodic fingerprint textures in shapes of dashed curve and dashed line are further demonstrated by utilizing a facile one-step polarization holography process using two beams with orthogonal circular and orthogonal linear polarizations, respectively. It is believed that the practical approach described in this study would enrich the research contents of self-assembled hierarchical superstructures using soft liquid crystal building blocks.

  14. Pattern formation in the bistable Gray-Scott model

    DEFF Research Database (Denmark)

    Mazin, W.; Rasmussen, K.E.; Mosekilde, Erik

    1996-01-01

    The paper presents a computer simulation study of a variety of far-from-equilibrium phenomena that can arise in a bistable chemical reaction-diffusion system which also displays Turing and Hopf instabilities. The Turing bifurcation curve and the wave number for the patterns of maximum linear grow...

  15. Dynamics of a bistable Miura-origami structure

    Science.gov (United States)

    Fang, Hongbin; Li, Suyi; Ji, Huimin; Wang, K. W.

    2017-05-01

    Origami-inspired structures and materials have shown extraordinary properties and performances originating from the intricate geometries of folding. However, current state of the art studies have mostly focused on static and quasistatic characteristics. This research performs a comprehensive experimental and analytical study on the dynamics of origami folding through investigating a stacked Miura-Ori (SMO) structure with intrinsic bistability. We fabricate and experimentally investigated a bistable SMO prototype with rigid facets and flexible crease lines. Under harmonic base excitation, the SMO exhibits both intrawell and interwell oscillations. Spectrum analyses reveal that the dominant nonlinearities of SMO are quadratic and cubic, which generate rich dynamics including subharmonic and chaotic oscillations. The identified nonlinearities indicate that a third-order polynomial can be employed to approximate the measured force-displacement relationship. Such an approximation is validated via numerical study by qualitatively reproducing the phenomena observed in the experiments. The dynamic characteristics of the bistable SMO resemble those of a Helmholtz-Duffing oscillator (HDO); this suggests the possibility of applying the established tools and insights of HDO to predict origami dynamics. We also show that the bistability of SMO can be programmed within a large design space via tailoring the crease stiffness and initial stress-free configurations. The results of this research offer a wealth of fundamental insights into the dynamics of origami folding, and provide a solid foundation for developing foldable and deployable structures and materials with embedded dynamic functionalities.

  16. Dynamics of a bistable Miura-origami structure.

    Science.gov (United States)

    Fang, Hongbin; Li, Suyi; Ji, Huimin; Wang, K W

    2017-05-01

    Origami-inspired structures and materials have shown extraordinary properties and performances originating from the intricate geometries of folding. However, current state of the art studies have mostly focused on static and quasistatic characteristics. This research performs a comprehensive experimental and analytical study on the dynamics of origami folding through investigating a stacked Miura-Ori (SMO) structure with intrinsic bistability. We fabricate and experimentally investigated a bistable SMO prototype with rigid facets and flexible crease lines. Under harmonic base excitation, the SMO exhibits both intrawell and interwell oscillations. Spectrum analyses reveal that the dominant nonlinearities of SMO are quadratic and cubic, which generate rich dynamics including subharmonic and chaotic oscillations. The identified nonlinearities indicate that a third-order polynomial can be employed to approximate the measured force-displacement relationship. Such an approximation is validated via numerical study by qualitatively reproducing the phenomena observed in the experiments. The dynamic characteristics of the bistable SMO resemble those of a Helmholtz-Duffing oscillator (HDO); this suggests the possibility of applying the established tools and insights of HDO to predict origami dynamics. We also show that the bistability of SMO can be programmed within a large design space via tailoring the crease stiffness and initial stress-free configurations. The results of this research offer a wealth of fundamental insights into the dynamics of origami folding, and provide a solid foundation for developing foldable and deployable structures and materials with embedded dynamic functionalities.

  17. Reversal Negativity and Bistable Stimuli: Attention, Awareness, or Something Else?

    Science.gov (United States)

    Intaite, Monika; Koivisto, Mika; Ruksenas, Osvaldas; Revonsuo, Antti

    2010-01-01

    Ambiguous (or bistable) figures are visual stimuli that have two mutually exclusive perceptual interpretations that spontaneously alternate with each other. Perceptual reversals, as compared with non-reversals, typically elicit a negative difference called reversal negativity (RN), peaking around 250 ms from stimulus onset. The cognitive…

  18. Kerr nonlinearity and plasmonic bistability in graphene nanoribbons

    DEFF Research Database (Denmark)

    Christensen, Thomas; Yan, Wei; Jauho, Antti-Pekka

    2015-01-01

    due to field enhancement, and the total nonlinearity is significantly affected by the field inhomogeneity of the plasmonic excitation. Finally, we discuss the emergence of a plasmonic bistability which exists for energies red-shifted relative to the linear resonance. Our results offer insights...

  19. Drag force actuated bistable microswitches for flow sensing

    NARCIS (Netherlands)

    Kuipers, W.J.; van Baar, J.J.J.; Dijkstra, Marcel; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; de Boer, J.H.; Krijnen, Gijsbertus J.M.

    2006-01-01

    This paper presents bistable microswitches with Au contacts with the aim to combine them with artificial hairs for flow sensing. The Au contacts are applied on both ends of a silicon nitride beam, suspended by a torsional bar at its center. The beam is provided with electrodes for electrostatic

  20. Bistable minimum energy structures (BiMES) for binary robotics

    International Nuclear Information System (INIS)

    Follador, M; Conn, A T; Rossiter, J

    2015-01-01

    Bistable minimum energy structures (BiMES) are devices derived from the union of the concepts of dielectric elastomer minimum energy structures and bistable systems. This article presents this novel approach to active, elastic and bistable structures. BiMES are based on dielectric elastomer actuators (DEAs), which act as antagonists and provide the actuation for switching between the two equilibrium positions. A central elastic beam is the backbone of the structure and is buckled into the minimum energy configurations by the action of the two DEAs. The theory and the model of the device are presented, and also its fabrication process. BiMES are considered as fundamental units for more complex structures, which are presented and fabricated as proof of concept. Two different ways of combining the multiple units are proposed: a parallel configuration, to make a simple gripper, and a serial configuration, to generate a binary device. The possibility of using the bistable system as a continuous bender actuator, by modulating the actuation voltage of the two DEAs, was also investigated. (paper)

  1. Phenomenological approach to bistable behavior of Josephson junctions

    International Nuclear Information System (INIS)

    Nishi, K.; Nara, S.; Hamanaka, K.

    1985-01-01

    The interaction of unbiased Josephson junction with external electromagnetic field in the presence of externally applied uniform magnetic field is theoretically examined by means of phenomenological treatment. It is proposed that an irradiated junction with suitably chosen parameters shows a bistable behavior of voltage across the junction as a function of the radiation intensity

  2. Light reflection by the cuticle of C. aurigans scarabs: a biological broadband reflector of left handed circularly polarized light

    Science.gov (United States)

    Libby, E.; Azofeifa, D. E.; Hernández-Jiménez, M.; Barboza-Aguilar, C.; Solís, A.; García-Aguilar, I.; Arce-Marenco, L.; Hernández, A.; Vargas, W. E.

    2014-08-01

    Measured reflection spectra from elytra of Chrysina aurigans scarabs are reported. They show a broad reflection band for wavelengths from 0.525 to 1.0 μm with a sequence of maxima and minima reflection values superimposed on a mean value of around 40% for the high reflection band. Different mechanisms contributing to the reflection spectra have been considered, with the dominant effect, reflection of left handed circularly polarized light, being produced by a laminated left handed twisted structure whose pitch changes with depth through the procuticle in a more complex way than that characterizing broad band circular polarizers based on cholesteric liquid crystals.

  3. Light reflection by the cuticle of C. aurigans scarabs: a biological broadband reflector of left handed circularly polarized light

    International Nuclear Information System (INIS)

    Libby, E; Azofeifa, D E; Hernández-Jiménez, M; García-Aguilar, I; Arce-Marenco, L; Hernández, A; Vargas, W E; Barboza-Aguilar, C; Solís, A

    2014-01-01

    Measured reflection spectra from elytra of Chrysina aurigans scarabs are reported. They show a broad reflection band for wavelengths from 0.525 to 1.0 μm with a sequence of maxima and minima reflection values superimposed on a mean value of around 40% for the high reflection band. Different mechanisms contributing to the reflection spectra have been considered, with the dominant effect, reflection of left handed circularly polarized light, being produced by a laminated left handed twisted structure whose pitch changes with depth through the procuticle in a more complex way than that characterizing broad band circular polarizers based on cholesteric liquid crystals. (fast track communication)

  4. Bistable dynamics of a levitated nanoparticle (Presentation Recording)

    Science.gov (United States)

    Ricci, Francesco; Spasenovic, M.; Rica, Raúl A.; Novotny, Lukas; Quidant, Romain

    2015-08-01

    Bistable systems are ubiquitous in nature. Classical examples in chemistry and biology include relaxation kinetics in chemical reactions [1] and stochastic resonance processes such as neuron firing [2,3]. Likewise, bistable systems play a key role in signal processing and information handling at the nanoscale, giving rise to intriguing applications such as optical switches [4], coherent signal amplification [5,6] and weak forces detection [5]. The interest and applicability of bistable systems are intimately connected with the complexity of their dynamics, typically due to the presence of a large number of parameters and nonlinearities. Appropriate modeling is therefore challenging. Alternatively, the possibility to experimentally recreate bistable systems in a clean and controlled way has recently become very appealing, but elusive and complicated. With this aim, we combined optical tweezers with a novel active feedback-cooling scheme to develop a well-defined opto-mechanical platform reaching unprecedented performances in terms of Q-factor, frequency stability and force sensitivity [7,8]. Our experimental system consists of a single nanoparticle levitated in high vacuum with optical tweezers, which behaves as a non-linear (Duffing) oscillator under appropriate conditions. Here, we prove it to be an ideal tool for a deep study of bistability. We demonstrate bistability of the nanoparticle by noise activated switching between two oscillation states, discussing our results in terms of a double-well potential model. We also show the flexibility of our system in shaping the potential at will, in order to meet the conditions prescribed by any bistable system that could therefore then be simulated with our setup. References [1] T. Amemiya, T. Ohmori, M. Nakaiwa, T. Yamamoto, and T. Yamaguchi, "Modeling of Nonlinear Chemical Reaction Systems and Two-Parameter Stochastic Resonance," J. Biol. Phys. 25 (1999) 73 [2] F. Moss, L. M. Ward, and W. G. Sannita, "Stochastic

  5. Switching waves dynamics in optical bistable cavity-free system at femtosecond laser pulse propagation in semiconductor under light diffraction

    Science.gov (United States)

    Trofimov, Vyacheslav A.; Egorenkov, Vladimir A.; Loginova, Maria M.

    2018-02-01

    We consider a propagation of laser pulse in a semiconductor under the conditions of an occurrence of optical bistability, which appears due to a nonlinear absorption of the semiconductor. As a result, the domains of high concentration of free charged particles (electrons and ionized donors) occur if an intensity of the incident optical pulse is greater than certain intensity. As it is well-known, that an optical beam must undergo a diffraction on (or reflection from) the domains boundaries. Usually, the beam diffraction along a coordinate of the optical pulse propagation does not take into account by using the slowly varying envelope approximation for the laser pulse interaction with optical bistable element. Therefore, a reflection of the beam from the domains with abrupt boundary does not take into account under computer simulation of the laser pulse propagation. However, the optical beams, reflected from nonhomogeneities caused by the domains of high concentration of free-charged particles, can essentially influence on a formation of switching waves in a semiconductor. We illustrate this statement by computer simulation results provided on the base of nonlinear Schrödinger equation and a set of PDEs, which describe an evolution of the semiconductor characteristics (concentrations of free-charged particles and potential of an electric field strength), and taking into account the longitudinal and transverse diffraction effects.

  6. Controlling the optical bistability and multistability in a two-level pumped-probe system

    International Nuclear Information System (INIS)

    Mahmoudi, Mohammad; Sahrai, Mostafa; Masoumeh Mousavi, Seyede

    2010-01-01

    We study the behavior of the optical bistability (OB) and multistability (OM) in a two-level pumped-probe atomic system by means of a unidirectional ring cavity. We show that the optical bistability in a two-level atomic system can be controlled by adjusting the intensity of the pump field and the detuning between two fields. We find that applying the pumping field decreases the threshold of the optical bistability.

  7. Bistability and self-oscillations effects in a polariton-laser semiconductor microcavity

    International Nuclear Information System (INIS)

    Cotta, E A; Matinaga, F M

    2007-01-01

    We report an experimental observation of polaritonic optical bistability of the laser emission in a planar semiconductor microcavity with a 100 0 A GaAs single quantum well in the strong-coupling regime. The bistability curves show crossings that indicate a competition between a Kerr-like effect induced by the polariton population and thermal effects. Associated with the bistability, laser-like emission occurs at the bare cavity mode

  8. Modeling bistable behaviors in morphing structures through finite element simulations.

    Science.gov (United States)

    Guo, Qiaohang; Zheng, Huang; Chen, Wenzhe; Chen, Zi

    2014-01-01

    Bistable structures, exemplified by the Venus flytrap and slap bracelets, can transit between different configurations upon certain external stimulation. Here we study, through three-dimensional finite element simulations, the bistable behaviors in elastic plates in the absence of terminate loads, but with pre-strains in one (or both) of the two composite layers. Both the scenarios with and without a given geometric mis-orientation angle are investigated, the results of which are consistent with recent theoretical and experimental studies. This work can open ample venues for programmable designs of plant/shell structures with large deformations, with applications in designing bio-inspired robotics for biomedical research and morphing/deployable structures in aerospace engineering.

  9. Coupling-induced oscillations in nonhomogeneous, overdamped, bistable systems

    International Nuclear Information System (INIS)

    Hernandez, Mayra; In, Visarath; Longhini, Patrick; Palacios, Antonio; Bulsara, Adi; Kho, Andy

    2008-01-01

    Coupling-induced oscillations in a homogeneous network of overdamped bistable systems have been previously studied both theoretically and experimentally for a system of N (odd) elements, unidirectionally coupled in a ring topology. In this work, we extend the analysis of this system to include a network of nonhomogeneous elements with respect to the parameter that controls the topology of the potential function and the bistability of each element. In particular, we quantify the effects of the nonhomogeneity on the onset of oscillations and the response of the network to external (assumed to be constant and very small) perturbations, using our (recently developed) coupled core fluxgate magnetometer as a representative system. The potential applications of this work include signal detection and characterization for a large class of sensor systems

  10. Coupling-induced oscillations in nonhomogeneous, overdamped, bistable systems

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, Mayra [Nonlinear Dynamical Systems Group, Department of Mathematics and Statistics, San Diego State University, San Diego, CA 92182 (United States)], E-mail: mayra.alina@yahoo.com; In, Visarath [Space and Naval Warfare Systems Center, Code 71730, 53560 Hull Street, San Diego, CA 92152-5001 (United States)], E-mail: visarath.in@navy.mil; Longhini, Patrick [Space and Naval Warfare Systems Center, Code 71730, 53560 Hull Street, San Diego, CA 92152-5001 (United States)], E-mail: longhini@navy.mil; Palacios, Antonio [Nonlinear Dynamical Systems Group, Department of Mathematics and Statistics, San Diego State University, San Diego, CA 92182 (United States)], E-mail: palacios@euler.sdsu.edu; Bulsara, Adi [Space and Naval Warfare Systems Center, Code 71730, 53560 Hull Street, San Diego, CA 92152-5001 (United States)], E-mail: bulsara@spawar.navy.mil; Kho, Andy [Space and Naval Warfare Systems Center, Code 71730, 53560 Hull Street, San Diego, CA 92152-5001 (United States)], E-mail: kho@spawar.navy.mil

    2008-06-09

    Coupling-induced oscillations in a homogeneous network of overdamped bistable systems have been previously studied both theoretically and experimentally for a system of N (odd) elements, unidirectionally coupled in a ring topology. In this work, we extend the analysis of this system to include a network of nonhomogeneous elements with respect to the parameter that controls the topology of the potential function and the bistability of each element. In particular, we quantify the effects of the nonhomogeneity on the onset of oscillations and the response of the network to external (assumed to be constant and very small) perturbations, using our (recently developed) coupled core fluxgate magnetometer as a representative system. The potential applications of this work include signal detection and characterization for a large class of sensor systems.

  11. A minimal model of burst-noise induced bistability.

    Directory of Open Access Journals (Sweden)

    Johannes Falk

    Full Text Available 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. We find that changing the size of bursts can destroy and even induce saddle-node bifurcations. This means that a bursty production of molecules can qualitatively change the dynamics of a chemical reaction system even when the deterministic description remains unchanged.

  12. Mathematical modeling of Myosin induced bistability of Lamellipodial fragments.

    Science.gov (United States)

    Hirsch, S; Manhart, A; Schmeiser, C

    2017-01-01

    For various cell types and for lamellipodial fragments on flat surfaces, externally induced and spontaneous transitions between symmetric nonmoving states and polarized migration have been observed. This behavior is indicative of bistability of the cytoskeleton dynamics. In this work, the Filament Based Lamellipodium Model (FBLM), a two-dimensional, anisotropic, two-phase continuum model for the dynamics of the actin filament network in lamellipodia, is extended by a new description of actin-myosin interaction. For appropriately chosen parameter values, the resulting model has bistable dynamics with stable states showing the qualitative features observed in experiments. This is demonstrated by numerical simulations and by an analysis of a strongly simplified version of the FBLM with rigid filaments and planar lamellipodia at the cell front and rear.

  13. Waterbomb base: a symmetric single-vertex bistable origami mechanism

    International Nuclear Information System (INIS)

    Hanna, Brandon H; Lund, Jason M; Magleby, Spencer P; Howell, Larry L; Lang, Robert J

    2014-01-01

    The origami waterbomb base is a single-vertex bistable origami mechanism that has unique properties which may prove useful in a variety of applications. It also shows promise as a test bed for smart materials and actuation because of its straightforward geometry and multiple phases of motion, ranging from simple to more complex. This study develops a quantitative understanding of the symmetric waterbomb base's kinetic behavior. This is done by completing kinematic and potential energy analyses to understand and predict bistable behavior. A physical prototype is constructed and tested to validate the results of the analyses. Finite element and virtual work analyses based on the prototype are used to explore the locations of the stable equilibrium positions and the force–deflection response. The model results are verified through comparisons to measurements on a physical prototype. The resulting models describe waterbomb base behavior and provide an engineering tool for application development. (paper)

  14. Novel piezoelectric bistable oscillator architecture for wideband vibration energy harvesting

    International Nuclear Information System (INIS)

    Liu, W Q; Badel, A; Formosa, F; Wu, Y P; Agbossou, A

    2013-01-01

    Bistable vibration energy harvesters are attracting more and more interest because of their capability to scavenge energy over a large frequency band. The bistable effect is usually based on magnetic interaction or buckled beams. This paper presents a novel architecture based on amplified piezoelectric structures. This buckled spring–mass architecture allows the energy of the dynamic mass to be converted into electrical energy in the piezoelectric materials as efficiently as possible. Modeling and design are performed and a normalized expression of the harvester behavior is given. Chirp and band-limited noise excitations are used to evaluate the proposed harvester’s performances. Simulation and experimental results are in good agreement. A method of using a spectrum plot for investigating the interwell motion is presented. The effect of the electric load impedance matching strategy is also studied. Results and comparisons with the literature show that the proposed device combines a large bandwidth and a high power density. (paper)

  15. Bistable dark solitons of a cubic-quintic Helmholtz equation

    International Nuclear Information System (INIS)

    Christian, J. M.; McDonald, G. S.; Chamorro-Posada, P.

    2010-01-01

    We provide a report on exact analytical bistable dark spatial solitons of a nonlinear Helmholtz equation with a cubic-quintic refractive-index model. Our analysis begins with an investigation of the modulational instability characteristics of Helmholtz plane waves. We then derive a dark soliton by mapping the desired asymptotic form onto a uniform background field and obtain a more general solution by deploying rotational invariance laws in the laboratory frame. The geometry of the new soliton is explored in detail, and a range of new physical predictions is uncovered. Particular attention is paid to the unified phenomena of arbitrary-angle off-axis propagation and nondegenerate bistability. Crucially, the corresponding solution of paraxial theory emerges in a simultaneous multiple limit. We conclude with a set of computer simulations that examine the role of Helmholtz dark solitons as robust attractors.

  16. Internal optical bistability of quasi-two-dimensional semiconductor nanoheterostructures

    Science.gov (United States)

    Derevyanchuk, Oleksandr V.; Kramar, Natalia K.; Kramar, Valeriy M.

    2018-01-01

    We represent the results of numerical computations of the frequency and temperature domains of possible realization of internal optical bistability in flat quasi-two-dimensional semiconductor nanoheterostructures with a single quantum well (i.e., nanofilms). Particular computations have been made for a nanofilm of layered semiconductor PbI2 embedded in dielectric medium, i.e. ethylene-methacrylic acid (E-MAA) copolymer. It is shown that an increase in the nanofilm's thickness leads to a long-wave shift of the frequency range of the manifestation the phenomenon of bistability, to increase the size of the hysteresis loop, as well as to the expansion of the temperature interval at which the realization of this phenomenon is possible.

  17. Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yuan; Deng, Li [Department of Applied Physics, East China Jiaotong University, Nanchang, 330013 (China); Chen, Aixi, E-mail: aixichen@ecjtu.jx.cn [Department of Applied Physics, East China Jiaotong University, Nanchang, 330013 (China); Institute for Quantum Computing, University of Waterloo, Ontario N2L 3G1 (Canada)

    2015-02-15

    We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.

  18. Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

    International Nuclear Information System (INIS)

    Chen, Yuan; Deng, Li; Chen, Aixi

    2015-01-01

    We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device

  19. Modeling Bistable Composite Laminates for Piezoelectric Morphing Structures

    OpenAIRE

    Darryl V. Murray; Oliver J. Myers

    2013-01-01

    A sequential modeling effort for bistable composite laminates for piezoelectric morphing structures is presented. Thin unsymmetric carbon fiber composite laminates are examined for use of morphing structures using piezoelectric actuation. When cooling from the elevated cure temperature to room temperature, these unsymmetric composite laminates will deform. These postcure room temperature deformation shapes can be used as morphing structures. Applying a force to these deformed laminates will c...

  20. Spatial effect on stochastic dynamics of bistable evolutionary games

    International Nuclear Information System (INIS)

    So, Kohaku H Z; Ohtsuki, Hisashi; Kato, Takeo

    2014-01-01

    We consider the lifetimes of metastable states in bistable evolutionary games (coordination games), and examine how they are affected by spatial structure. A semiclassical approximation based on a path integral method is applied to stochastic evolutionary game dynamics with and without spatial structure, and the lifetimes of the metastable states are evaluated. It is shown that the population dependence of the lifetimes is qualitatively different in these two models. Our result indicates that spatial structure can accelerate the transitions between metastable states. (paper)

  1. Dynamic optical bistability in resonantly enhanced Raman generation

    International Nuclear Information System (INIS)

    Novikova, I.; Phillips, D.F.; Zibrov, A.S.; Andre, A.; Walsworth, R.L.

    2004-01-01

    We report observations of novel dynamic behavior in resonantly enhanced stimulated Raman scattering in Rb vapor. In particular, we demonstrate a dynamic hysteresis of the Raman scattered optical field in response to changes of the drive laser field intensity and/or frequency. This effect may be described as a dynamic form of optical bistability resulting from the formation and decay of atomic coherence. We have applied this phenomenon to the realization of an all-optical switch

  2. A Precise Temperature-Responsive Bistable Switch Controlling Yersinia Virulence.

    Science.gov (United States)

    Nuss, Aaron Mischa; Schuster, Franziska; Roselius, Louisa; Klein, Johannes; Bücker, René; Herbst, Katharina; Heroven, Ann Kathrin; Pisano, Fabio; Wittmann, Christoph; Münch, Richard; Müller, Johannes; Jahn, Dieter; Dersch, Petra

    2016-12-01

    Different biomolecules have been identified in bacterial pathogens that sense changes in temperature and trigger expression of virulence programs upon host entry. However, the dynamics and quantitative outcome of this response in individual cells of a population, and how this influences pathogenicity are unknown. Here, we address these questions using a thermosensing virulence regulator of an intestinal pathogen (RovA of Yersinia pseudotuberculosis) as a model. We reveal that this regulator is part of a novel thermoresponsive bistable switch, which leads to high- and low-invasive subpopulations within a narrow temperature range. The temperature range in which bistability is observed is defined by the degradation and synthesis rate of the regulator, and is further adjustable via a nutrient-responsive regulator. The thermoresponsive switch is also characterized by a hysteretic behavior in which activation and deactivation occurred on vastly different time scales. Mathematical modeling accurately mirrored the experimental behavior and predicted that the thermoresponsiveness of this sophisticated bistable switch is mainly determined by the thermo-triggered increase of RovA proteolysis. We further observed RovA ON and OFF subpopulations of Y. pseudotuberculosis in the Peyer's patches and caecum of infected mice, and that changes in the RovA ON/OFF cell ratio reduce tissue colonization and overall virulence. This points to a bet-hedging strategy in which the thermoresponsive bistable switch plays a key role in adapting the bacteria to the fluctuating conditions encountered as they pass through the host's intestinal epithelium and suggests novel strategies for the development of antimicrobial therapies.

  3. A Precise Temperature-Responsive Bistable Switch Controlling Yersinia Virulence.

    Directory of Open Access Journals (Sweden)

    Aaron Mischa Nuss

    2016-12-01

    Full Text Available Different biomolecules have been identified in bacterial pathogens that sense changes in temperature and trigger expression of virulence programs upon host entry. However, the dynamics and quantitative outcome of this response in individual cells of a population, and how this influences pathogenicity are unknown. Here, we address these questions using a thermosensing virulence regulator of an intestinal pathogen (RovA of Yersinia pseudotuberculosis as a model. We reveal that this regulator is part of a novel thermoresponsive bistable switch, which leads to high- and low-invasive subpopulations within a narrow temperature range. The temperature range in which bistability is observed is defined by the degradation and synthesis rate of the regulator, and is further adjustable via a nutrient-responsive regulator. The thermoresponsive switch is also characterized by a hysteretic behavior in which activation and deactivation occurred on vastly different time scales. Mathematical modeling accurately mirrored the experimental behavior and predicted that the thermoresponsiveness of this sophisticated bistable switch is mainly determined by the thermo-triggered increase of RovA proteolysis. We further observed RovA ON and OFF subpopulations of Y. pseudotuberculosis in the Peyer's patches and caecum of infected mice, and that changes in the RovA ON/OFF cell ratio reduce tissue colonization and overall virulence. This points to a bet-hedging strategy in which the thermoresponsive bistable switch plays a key role in adapting the bacteria to the fluctuating conditions encountered as they pass through the host's intestinal epithelium and suggests novel strategies for the development of antimicrobial therapies.

  4. Stochastic dynamics of a delayed bistable system with multiplicative noise

    Energy Technology Data Exchange (ETDEWEB)

    Dung, Nguyen Tien, E-mail: dung-nguyentien10@yahoo.com, E-mail: dungnt@fpt.edu.vn [Department of Mathematics, FPT University, No 8 Ton That Thuyet, My Dinh, Tu Liem, Hanoi (Viet Nam)

    2014-05-15

    In this paper we investigate the properties of a delayed bistable system under the effect of multiplicative noise. We first prove the existence and uniqueness of the positive solution and show that its moments are uniformly bounded. Then, we study stochastic dynamics of the solution in long time, the lower and upper bounds for the paths and an estimate for the average value are provided.

  5. Traveling waves in the discrete fast buffered bistable system.

    Science.gov (United States)

    Tsai, Je-Chiang; Sneyd, James

    2007-11-01

    We study the existence and uniqueness of traveling wave solutions of the discrete buffered bistable equation. Buffered excitable systems are used to model, among other things, the propagation of waves of increased calcium concentration, and discrete models are often used to describe the propagation of such waves across multiple cells. We derive necessary conditions for the existence of waves, and, under some restrictive technical assumptions, we derive sufficient conditions. When the wave exists it is unique and stable.

  6. Bistable flapping of flexible flyers in oscillatory flow

    Science.gov (United States)

    Huang, Yangyang; Kanso, Eva

    2016-11-01

    Biological and bio-inspired flyers move by shape actuation. The direct control of shape variables for locomotory purposes is well studied. Less is known about indirect shape actuation via the fluid medium. Here, we consider a flexible Λ-flyer in oscillatory flow that is free to flap and rotate around its fixed apex. We study its motion in the context of the inviscid vortex sheet model. We first analyze symmetric flapping about the vertical axis of gravity. We find that there is a finite value of the flexibility that maximizes both the flapping amplitude and elastic energy storage. Our results show that rather than resonance, the flyer relies on fluidic effects to optimize these two quantities. We then perturb the flyer away from the vertical and analyze its stability. Four distinct types of rolling behavior are identified: mono-stable, bistable, bistable oscillatory rotations and chaotic dynamics. We categorize these types of behavior in terms of the flyer's and flow parameters. In particular, the transition from mono-stable to bistable behavior occurs at a constant value of the product of the flow amplitude and acceleration. This product can be interpreted as the ratio of fluidic drag to gravity, confirming the fluid role in this transition.

  7. Interplay of bistable kinetics of gene expression during cellular growth

    International Nuclear Information System (INIS)

    Zhdanov, Vladimir P

    2009-01-01

    In cells, the bistable kinetics of gene expression can be observed on the level of (i) one gene with positive feedback between protein and mRNA production, (ii) two genes with negative mutual feedback between protein and mRNA production, or (iii) in more complex cases. We analyse the interplay of two genes of type (ii) governed by a gene of type (i) during cellular growth. In particular, using kinetic Monte Carlo simulations, we show that in the case where gene 1, operating in the bistable regime, regulates mutually inhibiting genes 2 and 3, also operating in the bistable regime, the latter genes may eventually be trapped either to the state with high transcriptional activity of gene 2 and low activity of gene 3 or to the state with high transcriptional activity of gene 3 and low activity of gene 2. The probability to get to one of these states depends on the values of the model parameters. If genes 2 and 3 are kinetically equivalent, the probability is equal to 0.5. Thus, our model illustrates how different intracellular states can be chosen at random with predetermined probabilities. This type of kinetics of gene expression may be behind complex processes occurring in cells, e.g., behind the choice of the fate by stem cells

  8. Bistable switches control memory and plasticity in cellular differentiation

    Science.gov (United States)

    Wang, Lei; Walker, Brandon L.; Iannaccone, Stephen; Bhatt, Devang; Kennedy, Patrick J.; Tse, William T.

    2009-01-01

    Development of stem and progenitor cells into specialized tissues in multicellular organisms involves a series of cell fate decisions. Cellular differentiation in higher organisms is generally considered irreversible, and the idea of developmental plasticity in postnatal tissues is controversial. Here, we show that inhibition of mitogen-activated protein kinase (MAPK) in a human bone marrow stromal cell-derived myogenic subclone suppresses their myogenic ability and converts them into satellite cell-like precursors that respond to osteogenic stimulation. Clonal analysis of the induced osteogenic response reveals ultrasensitivity and an “all-or-none” behavior, hallmarks of a bistable switch mechanism with stochastic noise. The response demonstrates cellular memory, which is contingent on the accumulation of an intracellular factor and can be erased by factor dilution through cell divisions or inhibition of protein synthesis. The effect of MAPK inhibition also exhibits memory and appears to be controlled by another bistable switch further upstream that determines cell fate. Once the memory associated with osteogenic differentiation is erased, the cells regain their myogenic ability. These results support a model of cell fate decision in which a network of bistable switches controls inducible production of lineage-specific differentiation factors. A competitive balance between these factors determines cell fate. Our work underscores the dynamic nature of cellular differentiation and explains mechanistically the dual properties of stability and plasticity associated with the process. PMID:19366677

  9. Experimental chaotic quantification in bistable vortex induced vibration systems

    Science.gov (United States)

    Huynh, B. H.; Tjahjowidodo, T.

    2017-02-01

    The study of energy harvesting by means of vortex induced vibration systems has been initiated a few years ago and it is considered to be potential as a low water current energy source. The energy harvester is realized by exposing an elastically supported blunt structure under water flow. However, it is realized that the system will only perform at a limited operating range (water flow) that is attributed to the resonance phenomenon that occurs only at a frequency that corresponds to the fluid flow. An introduction of nonlinear elements seems to be a prominent solution to overcome the problem. Among many nonlinear elements, a bistable spring is known to be able to improve the harvested power by a vortex induced vibrations (VIV) based energy converter at the low velocity water flows. However, it is also observed that chaotic vibrations will occur at different operating ranges that will erratically diminish the harvested power and cause a difficulty in controlling the system that is due to the unpredictability in motions of the VIV structure. In order to design a bistable VIV energy converter with improved harvested power and minimum negative effect of chaotic vibrations, the bifurcation map of the system for varying governing parameters is highly on demand. In this study, chaotic vibrations of a VIV energy converter enhanced by a bistable stiffness element are quantified in a wide range of the governing parameters, i.e. damping and bistable gap. Chaotic vibrations of the bistable VIV energy converter are simulated by utilization of a wake oscillator model and quantified based on the calculation of the Lyapunov exponent. Ultimately, a series of experiments of the system in a water tunnel, facilitated by a computer-based force-feedback testing platform, is carried out to validate the existence of chaotic responses. The main challenge in dealing with experimental data is in distinguishing chaotic response from noise-contaminated periodic responses as noise will smear

  10. Pivotal role of hMT+ in long-range disambiguation of interhemispheric bistable surface motion.

    Science.gov (United States)

    Duarte, João Valente; Costa, Gabriel Nascimento; Martins, Ricardo; Castelo-Branco, Miguel

    2017-10-01

    It remains an open question whether long-range disambiguation of ambiguous surface motion can be achieved in early visual cortex or instead in higher level regions, which concerns object/surface segmentation/integration mechanisms. We used a bistable moving stimulus that can be perceived as a pattern comprehending both visual hemi-fields moving coherently downward or as two widely segregated nonoverlapping component objects (in each visual hemi-field) moving separately inward. This paradigm requires long-range integration across the vertical meridian leading to interhemispheric binding. Our fMRI study (n = 30) revealed a close relation between activity in hMT+ and perceptual switches involving interhemispheric segregation/integration of motion signals, crucially under nonlocal conditions where components do not overlap and belong to distinct hemispheres. Higher signal changes were found in hMT+ in response to spatially segregated component (incoherent) percepts than to pattern (coherent) percepts. This did not occur in early visual cortex, unlike apparent motion, which does not entail surface segmentation. We also identified a role for top-down mechanisms in state transitions. Deconvolution analysis of switch-related changes revealed prefrontal, insula, and cingulate areas, with the right superior parietal lobule (SPL) being particularly involved. We observed that directed influences could emerge either from left or right hMT+ during bistable motion integration/segregation. SPL also exhibited significant directed functional connectivity with hMT+, during perceptual state maintenance (Granger causality analysis). Our results suggest that long-range interhemispheric binding of ambiguous motion representations mainly reflect bottom-up processes from hMT+ during perceptual state maintenance. In contrast, state transitions maybe influenced by high-level regions such as the SPL. Hum Brain Mapp 38:4882-4897, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley

  11. Bistable optical response of a nanoparticle heterodimer : Mechanism, phase diagram, and switching time

    NARCIS (Netherlands)

    Nugroho, Bintoro; Iskandar, Alexander; Malyshev, V.A.; Knoester, Jasper

    2013-01-01

    We conduct a theoretical study of the bistable optical response of a nanoparticle heterodimer comprised of a closely spaced semiconductor quantum dot and a metal nanoparticle. The bistable nature of the response results from the interplay between the quantum dot's optical nonlinearity and its

  12. Optical bistability in Er-Yb codoped phosphate glass microspheres at room temperature

    NARCIS (Netherlands)

    Warda, Jonathan M.; O'Shea, Danny G.; Shortt, Brian J.; Chormaic, Sile Nic

    2007-01-01

    We experimentally demonstrate optical bistability in Er(3+)-Yb(3+) phosphate glass microspheres at 295 K. Bistability is associated with both Er(3+) fluorescence and lasing behavior, and chromatic switching. The chromatic switching results from an intrinsic mechanism exploiting the thermal coupling

  13. Take it of leave it : Mechanisms underlying bacterial bistable regulatory networks

    NARCIS (Netherlands)

    Siebring, Jeroen; Sorg, Robin; Herber, Martijn; Kuipers, Oscar; Filloux, Alain A.M.

    2012-01-01

    Bistable switches occur in regulatory networks that can exist in two distinct stable states. Such networks allow distinct switching of individual cells. In bacteria these switches coexist with regulatory networks that respond gradually to environmental input. Bistable switches play key roles in high

  14. Configurational rearrangements of bistable centers in covalent semiconductors - phase transitions of the second type

    International Nuclear Information System (INIS)

    Ivanyukovich, V.A.; Karas', V.I.; Lomako, V.M.

    1989-01-01

    A new radiation configurational-bistable defect diffring from the known similar defects by the fact that it possessestemperature inversion of states is detected in gallium arsenide. Configurational-bistable rearrangements are shown to be considered as phase transitions of the second type

  15. Bistable traveling waves for a competitive-cooperative system with nonlocal delays

    Science.gov (United States)

    Tian, Yanling; Zhao, Xiao-Qiang

    2018-04-01

    This paper is devoted to the study of bistable traveling waves for a competitive-cooperative reaction and diffusion system with nonlocal time delays. The existence of bistable waves is established by appealing to the theory of monotone semiflows and the finite-delay approximations. Then the global stability of such traveling waves is obtained via a squeezing technique and a dynamical systems approach.

  16. Topical Meeting on Optical Bistability Held at Rochester, New York on 15-17 June 1983.

    Science.gov (United States)

    1983-01-01

    ThB16-1 SELF-BEATING INSTABILITIES IN BISTABLE DEVICES J.A. MARTIN-PEREDA .. M.A. MURIEL DEPARTAMENTO DE ELECTRONICA CUANTICA E.T.S. ING...OPTICAL BISTABLL SYSTEMS J.A. MARTIN PEREDA M.A. MURIEL ; DEPARTAMENIO DE ELECTRONICA CUANTICA E.T.S. ING. TELLCOMUNICACION UNIVERSIDAD POLITECNICA DE

  17. Linear population allocation by bistable switches in response to transient stimulation.

    Science.gov (United States)

    Srimani, Jaydeep K; Yao, Guang; Neu, John; Tanouchi, Yu; Lee, Tae Jun; You, Lingchong

    2014-01-01

    Many cellular decision processes, including proliferation, differentiation, and phenotypic switching, are controlled by bistable signaling networks. In response to transient or intermediate input signals, these networks allocate a population fraction to each of two distinct states (e.g. OFF and ON). While extensive studies have been carried out to analyze various bistable networks, they are primarily focused on responses of bistable networks to sustained input signals. In this work, we investigate the response characteristics of bistable networks to transient signals, using both theoretical analysis and numerical simulation. We find that bistable systems exhibit a common property: for input signals with short durations, the fraction of switching cells increases linearly with the signal duration, allowing the population to integrate transient signals to tune its response. We propose that this allocation algorithm can be an optimal response strategy for certain cellular decisions in which excessive switching results in lower population fitness.

  18. Optical bistability via quantum interference from incoherent pumping and spontaneous emission

    International Nuclear Information System (INIS)

    Sahrai, M.; Asadpour, S.H.; Sadighi-Bonabi, R.

    2011-01-01

    We theoretically investigate the optical bistability (OB) in a V-type three-level atomic system confined in a unidirectional ring cavity via incoherent pumping field. It is shown that the threshold of optical bistability can be controlled by the rate of an incoherent pumping field and by interference mechanism arising from the spontaneous emission and incoherent pumping field. We demonstrate that the optical bistability converts to optical multi-stability (OM) by the quantum interference mechanism. - Highlights: → We modulate the optical bistability (OB) in a four-level N-type atomic system. → The threshold of optical bistability can be controlled by the quantum interferences. → OB converts to optical multi-stability (OM) by the quantum interferences. → We discuss the effect of an incoherent pumping field on reduction of OB threshold.

  19. A review of the recent research on vibration energy harvesting via bistable systems

    International Nuclear Information System (INIS)

    Harne, R L; Wang, K W

    2013-01-01

    The investigation of the conversion of vibrational energy into electrical power has become a major field of research. In recent years, bistable energy harvesting devices have attracted significant attention due to some of their unique features. Through a snap-through action, bistable systems transition from one stable state to the other, which could cause large amplitude motion and dramatically increase power generation. Due to their nonlinear characteristics, such devices may be effective across a broad-frequency bandwidth. Consequently, a rapid engagement of research has been undertaken to understand bistable electromechanical dynamics and to utilize the insight for the development of improved designs. This paper reviews, consolidates, and reports on the major efforts and findings documented in the literature. A common analytical framework for bistable electromechanical dynamics is presented, the principal results are provided, the wide variety of bistable energy harvesters are described, and some remaining challenges and proposed solutions are summarized. (topical review)

  20. Optical manipulation of photonic defect-modes in cholesteric liquid crystals induced by direct laser-lithography

    International Nuclear Information System (INIS)

    Yoshida, Hiroyuki; Lee, Chee Heng; Miura, Yusuke; Fujii, Akihiko; Ozaki, Masanori

    2008-01-01

    Manipulation of photonic defect-modes in cholesteric liquid crystals (ChLCs), which are one-dimensional pseudo photonic band-gap materials have been demonstrated by an external optical field. A structural defect in which the pitch length of the ChLC in the bulk and the defect are different was introduced by inducing local polymerization in a photo-polymerizable ChLC material by a direct laser-lithography process, and infiltrating a different ChLC material as the defect medium. When an azobenzene dye-doped ChLC was infiltrated in the defect, the trans-cis isomerization of the dye upon ultraviolet (UV) exposure caused the pitch to shorten, changing the contrast in the pitch lengths at the bulk and the defect, leading to a consequent shifting of the defect-mode. The all-optical manipulation was reversible and had high reproducibility

  1. Stochastic resonance in bistable systems driven by harmonic noise

    International Nuclear Information System (INIS)

    Neiman, A.; Schimansky-Geier, L.

    1994-01-01

    We study stochastic resonance in a bistable system which is excited simultaneously by white and harmonic noise which we understand as the signal. In our case the spectral line of the signal has a finite width as it occurs in many real situations. Using techniques of cumulant analysis as well as computer simulations we find that the effect of stochastic resonance is preserved in the case of harmonic noise excitation. Moreover we show that the width of the spectral line of the signal at the output can be decreased via stochastic resonance. The last could be of importance in the practical using of the stochastic resonance

  2. The tunable bistable and multistable memory effect in polymer nanowires

    International Nuclear Information System (INIS)

    Rahman, Atikur; Sanyal, Milan K

    2008-01-01

    Tunable bistable and multistable resistance switching in conducting polymer nanowires has been reported. These wires show reproducible switching transition under several READ-WRITE-ERASE cycles. The switching is observed at low temperature and the ON/OFF resistance ratio for the voltage biased switching transition was found to be more than 10 3 . Current biased measurements show lower ON/OFF ratio and some of the nanowires exhibit a multistable switching transition in current biased measurements. The threshold voltage for switching and the ON/OFF resistance ratio can be tuned by changing doping concentration of the nanowires

  3. Electron transfer dynamics of bistable single-molecule junctions

    DEFF Research Database (Denmark)

    Danilov, A.V; Kubatkin, S.; Kafanov, S. G.

    2006-01-01

    We present transport measurements of single-molecule junctions bridged by a molecule with three benzene rings connected by two double bonds and with thiol end-groups that allow chemical binding to gold electrodes. The I-V curves show switching behavior between two distinct states. By statistical ...... analysis of the switching events, we show that a 300 meV mode mediates the transition between the two states. We propose that breaking and reformation of a S-H bond in the contact zone between molecule and electrode explains the observed bistability....

  4. Application of the Asymptotic Taylor Expansion Method to Bistable Potentials

    Directory of Open Access Journals (Sweden)

    Okan Ozer

    2013-01-01

    Full Text Available A recent method called asymptotic Taylor expansion (ATEM is applied to determine the analytical expression for eigenfunctions and numerical results for eigenvalues of the Schrödinger equation for the bistable potentials. Optimal truncation of the Taylor series gives a best possible analytical expression for eigenfunctions and numerical results for eigenvalues. It is shown that the results are obtained by a simple algorithm constructed for a computer system using symbolic or numerical calculation. It is observed that ATEM produces excellent results consistent with the existing literature.

  5. Atom-loss-induced quantum optical bi-stability switch

    International Nuclear Information System (INIS)

    Wu Bao-Jun; Cui Fu-Cheng

    2012-01-01

    We investigate the nonlinear dynamics of a system composed of a cigar-shaped Bose—Einstein condensate and an optical cavity with the two sides coupled dispersively. By adopting discrete-mode approximation for the condensate, taking atom loss as a necessary part of the model to analyze the evolution of the system, while using trial and error method to find out steady states of the system as a reference, numerical simulation demonstrates that with a constant pump, atom loss will trigger a quantum optical bi-stability switch, which predicts a new interesting phenomenon for experiments to verify

  6. Optical bistabilities of higher harmonics: Inhomogeneous and transverse effects

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, S.S., E-mail: Shoukryhassan@hotmail.com [Department of Mathematics, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain); Manchester Metropolitan University, Dept. of Computing, Maths. and Digital Technology, Manchester M1 5GD (United Kingdom); Sharaby, Y.A., E-mail: Yasser_Sharaby@hotmail.com [Department of Physics, Faculty of Science, Suez Canal University, Suez (Egypt); Ali, M.F.M., E-mail: dr.mona.fathy@hotmail.com [Department of Mathematics: Faculty of Science, Ain Shams University, Cairo (Egypt); Joshi, A., E-mail: ajoshi@eiu.edu [Department of Physics, Eastern Illinois University, Charleston, IL 61920 (United States)

    2012-10-15

    The steady state behavior of optical bistable system in a ring cavity with transverse field variations and inhomogeneousely broadened two-level atoms is investigated outside the rotating wave approximation (RWA). Analytical and numerical investigation is presented for different cases of transverse field variations with Lorentzian or Gaussian line widths. When both (transverse and inhomogeneous) features taken into account, the first harmonic output field component outside the RWA exhibits a one-way switching down processes (butterfly OB) or reversed (clockwise) OB behavior, depending on the atomic linewidth shape.

  7. Optical bistabilities of higher harmonics: Inhomogeneous and transverse effects

    International Nuclear Information System (INIS)

    Hassan, S.S.; Sharaby, Y.A.; Ali, M.F.M.; Joshi, A.

    2012-01-01

    The steady state behavior of optical bistable system in a ring cavity with transverse field variations and inhomogeneousely broadened two-level atoms is investigated outside the rotating wave approximation (RWA). Analytical and numerical investigation is presented for different cases of transverse field variations with Lorentzian or Gaussian line widths. When both (transverse and inhomogeneous) features taken into account, the first harmonic output field component outside the RWA exhibits a one-way switching down processes (butterfly OB) or reversed (clockwise) OB behavior, depending on the atomic linewidth shape.

  8. Bistable Helmholtz solitons in cubic-quintic materials

    International Nuclear Information System (INIS)

    Christian, J. M.; McDonald, G. S.; Chamorro-Posada, P.

    2007-01-01

    We propose a nonlinear Helmholtz equation for modeling the evolution of broad optical beams in media with a cubic-quintic intensity-dependent refractive index. This type of nonlinearity is appropriate for some semiconductor materials, glasses, and polymers. Exact analytical soliton solutions are presented that describe self-trapped nonparaxial beams propagating at any angle with respect to the reference direction. These spatially symmetric solutions are, to the best of our knowledge, the first bistable Helmholtz solitons to be derived. Accompanying conservation laws (both integral and particular forms) are also reported. Numerical simulations investigate the stability of the solitons, which appear to be remarkably robust against perturbations

  9. Bistable switching in dual-frequency liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Barnik, M I [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2006-06-15

    Various bistable switching modes in nematic liquid crystals with frequency inversion of the sign of dielectric anisotropy are revealed and investigated. Switching between states with different helicoidal distributions of the director field of a liquid crystal, as well as between uniform and helicoidal states, is realized by dual-frequency waveforms of a driving voltage. A distinctive feature of the dual-frequency switching is that the uniform planar distribution of the director field may correspond to a thermodynamically equilibrium state, and the chirality of an LC is not a necessary condition for switching to a helicoidal state.

  10. Entire solutions for bistable lattice differential equations with obstacles

    CERN Document Server

    Hoffman, Aaron; Vleck, E S Van

    2018-01-01

    The authors consider scalar lattice differential equations posed on square lattices in two space dimensions. Under certain natural conditions they show that wave-like solutions exist when obstacles (characterized by "holes") are present in the lattice. Their work generalizes to the discrete spatial setting the results obtained in Berestycki, Hamel, and Matuno (2009) for the propagation of waves around obstacles in continuous spatial domains. The analysis hinges upon the development of sub and super-solutions for a class of discrete bistable reaction-diffusion problems and on a generalization of a classical result due to Aronson and Weinberger that concerns the spreading of localized disturbances.

  11. Noticeable positive Doppler effect on optical bistability in an N-type active Raman gain atomic system

    International Nuclear Information System (INIS)

    Chang Zeng-Guang; Zhang Jing-Tao; Niu Yue-Ping; Gong Shang-Qing

    2012-01-01

    We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region, which has been known as the positive Doppler effect on optical bistability. In addition, we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type

  12. Multiple Bistability in Quinonoid-Bridged Diiron(II) Complexes: Influence of Bridge Symmetry on Bistable Properties.

    Science.gov (United States)

    van der Meer, Margarethe; Rechkemmer, Yvonne; Breitgoff, Frauke D; Marx, Raphael; Neugebauer, Petr; Frank, Uta; van Slageren, Joris; Sarkar, Biprajit

    2016-11-21

    Quinonoid bridges are well-suited for generating dinuclear assemblies that might display various bistable properties. In this contribution we present two diiron(II) complexes where the iron(II) centers are either bridged by the doubly deprotonated form of a symmetrically substituted quinonoid bridge, 2,5-bis[4-(isopropyl)anilino]-1,4-benzoquinone (H 2 L2') with a [O,N,O,N] donor set, or with the doubly deprotonated form of an unsymmetrically substituted quinonoid bridge, 2-[4-(isopropyl)anilino]-5-hydroxy-1,4-benzoquinone (H 2 L5') with a [O,O,O,N] donor set. Both complexes display temperature-induced spin crossover (SCO). The nature of the SCO is strongly dependent on the bridging ligand, with only the complex with the [O,O,O,N] donor set displaying a prominent hysteresis loop of about 55 K. Importantly, only the latter complex also shows a pronounced light-induced spin state change. Furthermore, both complexes can be oxidized to the mixed-valent iron(II)-iron(III) form, and the nature of the bridge determines the Robin and Day classification of these forms. Both complexes have been probed by a battery of electrochemical, spectroscopic, and magnetic methods, and this combined approach is used to shed light on the electronic structures of the complexes and on bistability. The results presented here thus show the potential of using the relatively new class of unsymmetrically substituted bridging quinonoid ligands for generating intriguing bistable properties and for performing site-specific magnetic switching.

  13. Optical bistability and limiting in polymer dispersed liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Yshino, K.; Tagawa, A.; Sadohara, Y.; Ozaki, M. (Osaka University, Osaka (Japan). Faculty of Engineering); Munezawa, T. (Ajinomoto Co. Inc., Tokyo (Japan)); Nomura, Y. (Takiron Co. Ltd., Osaka (Japan))

    1991-04-15

    The linear electro-optical effect of polymer dispersed liquid crystal (PDLC) and the nonlinear optical response of electrically feedbacked PDLC were studied. Electro-optical limiting and bistability were observed in PDLCs with negative and positive feedback, respectively. In the PDLC film with positive feedback gain, an optical hysteresis loop shifted toward a high intensity region with decreasing magnitude of the feedback gain. The switching between high and low transmission states in an optical bistable region was realized by controlling incident light, and the on-off switching by superimposing light pulse on incident light for an extremely short period (several hundreds {mu}s). As the light pulse was strong, the minimum pulse width required for switching was as short as 500 {mu}s or less. The on-off switching was also realized by shutting out the incident light for a period equivalent to the pulse width. Slower response times of the PDLC film required longer minimum pulse widths. 12 refs., 11 figs.

  14. Bistability and displacement fluctuations in a quantum nanomechanical oscillator

    Science.gov (United States)

    Avriller, R.; Murr, B.; Pistolesi, F.

    2018-04-01

    Remarkable features have been predicted for the mechanical fluctuations at the bistability transition of a classical oscillator coupled capacitively to a quantum dot [Micchi et al., Phys. Rev. Lett. 115, 206802 (2015), 10.1103/PhysRevLett.115.206802]. These results have been obtained in the regime ℏ ω0≪kBT ≪ℏ Γ , where ω0, T , and Γ are the mechanical resonating frequency, the temperature, and the tunneling rate, respectively. A similar behavior could be expected in the quantum regime of ℏ Γ ≪kBT ≪ℏ ω0 . We thus calculate the energy- and displacement-fluctuation spectra and study their behavior as a function of the electromechanical coupling constant when the system enters the Frank-Condon regime. We find that in analogy with the classical case, the energy-fluctuation spectrum and the displacement spectrum widths show a maximum for values of the coupling constant at which a mechanical bistability is established.

  15. Designing a stochastic genetic switch by coupling chaos and bistability

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xiang [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Ouyang, Qi [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Center for Quantitative Biology, Peking University, Beijing 100871 (China); The Peking-Tsinghua Center for Life Sciences, Beijing 100871 (China); Wang, Hongli, E-mail: hlwang@pku.edu.cn [State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Center for Quantitative Biology, Peking University, Beijing 100871 (China)

    2015-11-15

    In stem cell differentiation, a pluripotent stem cell becomes progressively specialized and generates specific cell types through a series of epigenetic processes. How cells can precisely determine their fate in a fluctuating environment is a currently unsolved problem. In this paper, we suggest an abstract gene regulatory network to describe mathematically the differentiation phenomenon featuring stochasticity, divergent cell fates, and robustness. The network consists of three functional motifs: an upstream chaotic motif, a buffering motif of incoherent feed forward loop capable of generating a pulse, and a downstream motif which is bistable. The dynamic behavior is typically a transient chaos with fractal basin boundaries. The trajectories take transiently chaotic journeys before divergently settling down to the bistable states. The ratio of the probability that the high state is achieved to the probability that the low state is reached can maintain a constant in a population of cells with varied molecular fluctuations. The ratio can be turned up or down when proper parameters are adjusted. The model suggests a possible mechanism for the robustness against fluctuations that is prominently featured in pluripotent cell differentiations and developmental phenomena.

  16. Control and characterization of a bistable laminate generated with piezoelectricity

    Science.gov (United States)

    Lee, Andrew J.; Moosavian, Amin; Inman, Daniel J.

    2017-08-01

    Extensive research has been conducted on utilizing smart materials such as piezoelectric and shape memory alloy actuators to induce snap through of bistable structures for morphing applications. However, there has only been limited success in initiating snap through from both stable states due to the lack of actuation authority. A novel solution in the form of a piezoelectrically generated bistable laminate consisting of only macro fiber composites (MFC), allowing complete configuration control without any external assistance, is explored in detail here. Specifically, this paper presents the full analytical, computational, and experimental results of the laminate’s design, geometry, bifurcation behavior, and snap through capability. By bonding two actuated MFCs in a [0MFC/90MFC]T layup and releasing the voltage post cure, piezoelectric strain anisotropy and the resulting in-plane residual stresses yield two statically stable states that are cylindrically shaped. The analytical model uses the Rayleigh-Ritz minimization of total potential energy and finite element analysis is implemented in MSC Nastran. The [0MFC/90MFC]T laminate is then manufactured and experimentally characterized for model validation. This paper demonstrates the adaptive laminate’s unassisted forward and reverse snap through capability enabled by the efficiencies gained from simultaneously being the actuator and the primary structure.

  17. A new concept for active bistable twisting structures

    Science.gov (United States)

    Schultz, Marc R.

    2005-05-01

    A novel type of morphing structure capable of a large change in shape with a small energy input is discussed in this paper. The considered structures consist of two curved shells that are joined in a specific manner to form a bistable airfoil-like structure. The two stable shapes have a difference in axial twist, and the structure may be transformed between the stable shapes by a simple snap-through action. The benefit of a bistable structure of this type is that, if the stable shapes are operational shapes, power is needed only to transform the structure from one shape to another. The discussed structures could be used in aerodynamic applications such as morphing wings, or as aerodynamic control surfaces. The investigation discussed in this paper considers both experiment and finite-element analysis. Several graphite-epoxy composite and one steel device were created as proof-of-concept models. To demonstrate active control of these structures, piezocomposite actuators were applied to one of the composite structures and used to transform the structure between stable shapes. The analysis was used to compare the predicted shapes with the experimental shapes, and to study how changes to the geometric input values affected the shape and operational characteristics of the structures. The predicted shapes showed excellent agreement with the experimental shapes, and the results of the parametric study suggest that the shapes and the snap-through characteristics can be easily tailored to meet specific needs.

  18. A Reliable Bistable Board Implementation through I/O Redundancy

    International Nuclear Information System (INIS)

    Kim, Min Gyu; Chung, Tae Hyok; Lee, Youn Sang; Kim, Tae Hee; Song, Seung Hwan

    2010-01-01

    Nuclear power plant safety systems and related equipment used in the design, including an accident in all driving conditions that must be proven In addition, the safety-related equipment that is derived according to the digitization of the safety equipment is the most important factors. Therefore, it is necessary to prove that the device was satisfied the requirements for a given performance for safety-related digital equipment for the life of the installation. These proven is done through the process, design verification of the equipment, production management, such as installation and maintenance. Among other things, it is most important to implement of the performance and reliability features the safety-related equipment in the design phase. In this paper, Bistable Board implemented to generate a ESF sign-on signal throughout the signal processing of input signal from sensors. Also, for the reliable signal input and output, I/O Module that implements the redundancy increases the reliability of the Bistable Board , to verify the performance of safety-related equipment

  19. Designing a stochastic genetic switch by coupling chaos and bistability.

    Science.gov (United States)

    Zhao, Xiang; Ouyang, Qi; Wang, Hongli

    2015-11-01

    In stem cell differentiation, a pluripotent stem cell becomes progressively specialized and generates specific cell types through a series of epigenetic processes. How cells can precisely determine their fate in a fluctuating environment is a currently unsolved problem. In this paper, we suggest an abstract gene regulatory network to describe mathematically the differentiation phenomenon featuring stochasticity, divergent cell fates, and robustness. The network consists of three functional motifs: an upstream chaotic motif, a buffering motif of incoherent feed forward loop capable of generating a pulse, and a downstream motif which is bistable. The dynamic behavior is typically a transient chaos with fractal basin boundaries. The trajectories take transiently chaotic journeys before divergently settling down to the bistable states. The ratio of the probability that the high state is achieved to the probability that the low state is reached can maintain a constant in a population of cells with varied molecular fluctuations. The ratio can be turned up or down when proper parameters are adjusted. The model suggests a possible mechanism for the robustness against fluctuations that is prominently featured in pluripotent cell differentiations and developmental phenomena.

  20. Model-based design of bistable cell factories for metabolic engineering.

    Science.gov (United States)

    Srinivasan, Shyam; Cluett, William R; Mahadevan, Radhakrishnan

    2018-04-15

    Metabolism can exhibit dynamic phenomena like bistability due to the presence of regulatory motifs like the positive feedback loop. As cell factories, microorganisms with bistable metabolism can have a high and a low product flux at the two stable steady states, respectively. The exclusion of metabolic regulation and network dynamics limits the ability of pseudo-steady state stoichiometric models to detect the presence of bistability, and reliably assess the outcomes of design perturbations to metabolic networks. Using kinetic models of metabolism, we assess the change in the bistable characteristics of the network, and suggest designs based on perturbations to the positive feedback loop to enable the network to produce at its theoretical maximum rate. We show that the most optimal production design in parameter space, for a small bistable metabolic network, may exist at the boundary of the bistable region separating it from the monostable region of low product fluxes. The results of our analysis can be broadly applied to other bistable metabolic networks with similar positive feedback network topologies. This can complement existing model-based design strategies by providing a smaller number of feasible designs that need to be tested in vivo. http://lmse.biozone.utoronto.ca/downloads/. krishna.mahadevan@utoronto.ca. Supplementary data are available at Bioinformatics online.

  1. Bistable resistive memory behavior in gelatin-CdTe quantum dot composite film

    Science.gov (United States)

    Vallabhapurapu, Sreedevi; Rohom, Ashwini; Chaure, N. B.; Du, Shengzhi; Srinivasan, Ananthakrishnan

    2018-05-01

    Bistable memory behavior has been observed for the first time in gelatin type A thin film dispersed with functionalized CdTe quantum dots. The two terminal device with the polymer nanocomposite layer sandwiched between an indium tin oxide coated glass plate and an aluminium top electrode performs as a bistable resistive random access memory module. Butterfly shaped (O-shaped with a hysteresis in forward and reverse sweeps) current-voltage response is observed in this device. The conduction mechanism leading to the bistable electrical switching has been deduced to be a combination of ohmic and electron hopping.

  2. Bistability Analysis of Excitatory-Inhibitory Neural Networks in Limited-Sustained-Activity Regime

    International Nuclear Information System (INIS)

    Ni Yun; Wu Liang; Wu Dan; Zhu Shiqun

    2011-01-01

    Bistable behavior of neuronal complex networks is investigated in the limited-sustained-activity regime when the network is composed of excitatory and inhibitory neurons. The standard stability analysis is performed on the two metastable states separately. Both theoretical analysis and numerical simulations show consistently that the difference between time scales of excitatory and inhibitory populations can influence the dynamical behaviors of the neuronal networks dramatically, leading to the transition from bistable behaviors with memory effects to the collapse of bistable behaviors. These results may suggest one possible neuronal information processing by only tuning time scales. (interdisciplinary physics and related areas of science and technology)

  3. Optical nonlinearity and bistability in the bound exciton energy range of CdS

    International Nuclear Information System (INIS)

    Hoenig, T.; Gutowski, J.

    1988-01-01

    Under high excitation conditions thick CdS samples show pronounced broad-band nonlinear transmission in the bound exciton region and up to a wavelength of about 515 nm at cryo-temperatures. This behavior is only explainable in a model based on impurity neutralization and bound exciton creation. The suitability of these nonlinearities to yield optical bistability will be shown. Bistable operation is investigated in dependence of crystal thickness, impurity concentration, excitation density, wavelength, and temperature. A strong correlation to acceptor-bound exciton generation is obtained, and the explanation of this bistable operation fits well with that of the above mentioned transmission behavior. (author)

  4. Aqueous cholesteric liquid crystals using uncharged rodlike polypeptides. Polypeptide vesicles by conformation-specific assembly. Ordered chiral macroporous hybrid silica-polypeptide composites

    Science.gov (United States)

    Bellomo, Enrico Giuseppe

    2005-07-01

    Aqueous cholesteric liquid crystals using uncharged rodlike polypeptides . The aqueous, lyotropic liquid-crystalline phase behavior of an alpha helical polypeptide, has been studied using optical microscopy and X-ray scattering. Solutions of optically pure polypeptide were found to form cholesteric liquid crystals at volume fractions that decreased with increasing average chain length. At very high volume fractions, the formation of a hexagonal mesophase was observed. The pitch of the cholesteric phase could be varied by a mixture of enantiomeric samples, where the pitch increased as the mixture approached equimolar. The cholesteric phases could be untwisted, using either magnetic field or shear flow, into nematic phases, which relaxed into cholesterics upon removal of field or shear. We have found that the phase diagram of this polypeptide in aqueous solution parallels that of poly(gamma-benzyl glutamate) in organic solvents, thus providing a useful system for liquid-crystal applications requiring water as solvent. Polypeptide vesicles by conformation-specific assembly. We have found that block copolymers composed of polypeptide segments provide significant advantages in controlling both the function and supramolecular structure of bioinspired self-assemblies. Incorporation of the stable chain conformations found in proteins into block copolymers was found to provide an additional element of control, beyond amphiphilicity and composition that defines self-assembled architecture. The abundance of functionality present in amino acids, and the ease by which they can be incorporated into these materials, also provides a powerful mechanism to impart block copolypeptides with function. This combination of structure and function work synergistically to enable significant advantages in the preparation of therapeutic agents as well as provide insight into design of self-assemblies beginning to approach the complexity of natural structures such as virus capsids. Ordered

  5. Delay induced stability switch, multitype bistability and chaos in an intraguild predation model.

    Science.gov (United States)

    Shu, Hongying; Hu, Xi; Wang, Lin; Watmough, James

    2015-12-01

    In many predator-prey models, delay has a destabilizing effect and induces oscillations; while in many competition models, delay does not induce oscillations. By analyzing a rather simple delayed intraguild predation model, which combines both the predator-prey relation and competition, we show that delay in intraguild predation models promotes very complex dynamics. The delay can induce stability switches exhibiting a destabilizing role as well as a stabilizing role. It is shown that three types of bistability are possible: one stable equilibrium coexists with another stable equilibrium (node-node bistability); one stable equilibrium coexists with a stable periodic solution (node-cycle bistability); one stable periodic solution coexists with another stable periodic solution (cycle-cycle bistability). Numerical simulations suggest that delay can also induce chaos in intraguild predation models.

  6. A novel optic bistable device with very low threshold intensity using photorefractive films

    Science.gov (United States)

    Wang, Sean X.; Sun, Yuankun; Trivedi, Sudhir B.; Li, Guifang

    1994-08-01

    Brimrose Corporation of America reports the successful completion of the SBIR Phase I research in low-threshold intensity optical bistable devices using photorefractive nonlinearity. A thin photorefractive film optical bistable device was proposed in the Phase I proposal. The feasibility of this device was theoretically investigated. The theoretical feasibility study formulates the materials requirements in such a kind of configuration for Phase II research. In addition, we have proposed and investigated another configuration of optical bistable devices that do not require advanced photorefractive materials, namely, the self-pumped phase conjugator. We have successfully demonstrated a low-threshold optical bistable operation in a KNSBN:CU crystal. To the best of our knowledge, the threshold of 650 mW/sq. cm is the lowest of its kind to be achieved so far.

  7. Innovative Energy Harvester Design Using Bistable Mechanism With Compensational Springs In Gravity Field

    International Nuclear Information System (INIS)

    Vysotskyi, Bogdan; Parrain, Fabien; Lefeuvre, Elie; Aubry, Denis; Gaucher, Philippe

    2016-01-01

    The purpose of the presented work is to introduce the novel design of electrostatic energy harvester using bistable mechanism with compensational springs in gravity field capable of providing the output of several μW under the excitation of extremely small amplitude (up to 0.2g) and low frequency (10-100Hz). Presented energy harvester uses the bistable hysteresis modification to achieve low-frequency low-amplitude sensibility. It was demonstrated with finite element modelling (FEM) that hysteresis width produced by bistability is changing with a constant linear coefficient as a function of a compensational spring stiffness and thus a device sensitivity could be adjusted to the minimum point for the amplitude of external excitation. Further, highly non-linear bistable double curved beam mechanism assures the high sensitivity in frequencial domain due to the non-defined bandwidth. The equivalent circuit technique is used for simulating the device performance. (paper)

  8. Geometric and potential dynamics interpretation of the optic ring resonator bistability

    Science.gov (United States)

    Chiangga, S.; Chittha, T.; Frank, T. D.

    2015-07-01

    The optical bistability is a fundamental nonlinear feature of the ring resonator. A geometric and potential dynamics interpretation of the bistability is given. Accordingly, the bistability of the nonlinear system is shown to be a consequence of geometric laws of vector calculus describing the resonator ring. In contrast, the so-called transcendental relations that have been obtained in the literature in order to describe the optical wave are interpreted in terms of potential dynamical systems. The proposed novel interpretation provides new insights into the nature of the ring resonator optical bistability. The fundamental work by Rukhlenko, Premaratne and Agrawal (2010) as well as a more recent study by Chiangga, Pitakwongsaporn, Frank and Yupapin (2013) are considered.

  9. Bistable output from a coupled-resonator vertical-cavity laser diode

    International Nuclear Information System (INIS)

    Fischer, A. J.; Choquette, K. D.; Chow, W. W.; Allerman, A. A.; Geib, K.

    2000-01-01

    We report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits bistable behavior in the light output versus injection current. Large bistability regions over current ranges as wide as 18 mA have been observed with on/off contrast ratios of greater than 20 dB. The position and width of the bistability region can be varied by changing the bias to the top cavity. Switching between on and off states can be accomplished with changes as small as 250 μW to the electrical power applied to the top cavity. The bistable behavior is the response of the nonlinear susceptibility in the top cavity to the changes in the bottom intracavity laser intensity as the bottom cavity reaches the thermal rollover point

  10. Harnessing the bistable composite shells to design a tunable phononic band gap structure

    Science.gov (United States)

    Li, Yi; Xu, Yanlong

    2018-02-01

    By proposing a system composed of an array of bistable composite shells immersed in air, we develop a new class of periodic structure to control the propagation of sound. Through numerical investigation, we find that the acoustic band gap of this system can be switched on and off by triggering the snap through deformation of the bistable composite shells. The shape of cross section and filling fraction of unit cell can be altered by different number of bistable composite shells, and they have strong impact on the position and width of the band gap. The proposed concept paves the way of using the bistable structures to design a new class of metamaterials that can be enable to manipulate sound.

  11. Microscopic observation of zenithal bistable switching in nematic devices with different surface relief structures

    International Nuclear Information System (INIS)

    Uche, C; Elston, S J; Parry-Jones, L A

    2005-01-01

    Nematic liquid crystals have been shown to exhibit zenithal electro-optic bistability in devices containing sinusoidal and deformed sinusoidal gratings. Recently it has been shown that zenithal bistable states can also be supported at isolated edges of square gratings. In this paper, we present microscopic observations of bistability in cells containing sinusoidal gratings and long-pitch square gratings. We have also investigated a novel display based on square wells. High frame-rate video microscopy was used to obtain time-sequenced images when the devices were switched with monopolar pulses. These show that zenithal bistable switching can occur by two different processes: (i) domain growth (observed in cells containing sinusoidal gratings) and (ii) homogenous switching (observed in cells containing isolated edges

  12. Optical bistability in the oscillation of an inhomogeneously broadened quasi-three-level laser

    International Nuclear Information System (INIS)

    Liu, Junhai; Tian, Xueping

    2013-01-01

    A theoretical modeling analysis is presented to study the optical bistability exhibited in the oscillation of an inhomogeneously broadened quasi-three-level laser. All the major characteristics of optical bistability depend on two normalized parameters, f and x a , which are defined by f = I sat,a /I sat,m and x a = 2α a0 p a /δ and are related to measurable properties of the laser medium. In comparison with the case of a homogeneously broadened laser, the essential condition for the occurrence of such bistability, f a /(x a + 1), turns out to be the same, whereas the intensities at the up- and down-thresholds are substantially increased and the bistability range is reduced. (paper)

  13. A bistable switch in dynamic thiodepsipeptide folding and template-directed ligation.

    Science.gov (United States)

    Mukherjee, Rakesh; Cohen-Luria, Rivka; Wagner, Nathaniel; Ashkenasy, Gonen

    2015-10-12

    Bistable reaction networks provide living cells with chemically controlled mechanisms for long-term memory storage. Such networks are also often switchable and can be flipped from one state to the other. We target here a major challenge in systems chemistry research, namely developing synthetic, non-enzymatic, networks that mimic such a complex function. Therefore, we describe a dynamic network that depending on initial thiodepsipeptide concentrations leads to one of two distinct steady states. This bistable system is readily switched by applying the appropriate stimuli. The relationship between the reaction network topology and its capacity to invoke bistability is then analyzed by control experiments and theory. We suggest that demonstrating bistable behavior using synthetic networks further highlights their possible role in early evolution, and may shine light on potential utility for novel applications, such as chemical memories. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Low threshold optical bistability and superluminal light propagation using a dielectric slab via inter-dot tunneling

    International Nuclear Information System (INIS)

    Taherzadeh, S; Nasehi, R; Mahmoudi, Mohammad

    2015-01-01

    The optical bistability (OB) behavior of a dielectric slab doped with quantum dot (QD) molecules is investigated in the presence of the inter-dot tunneling effect. It is shown that the threshold point of OB reduces by increasing inter-dot tunneling as well as by reducing the slab thickness. It is worth noting that the threshold of OB in a slab doped with QD molecules is smaller, by at least one order of magnitude, in respect to free QD molecules. We find that the inter-dot tunneling induces a negative group delay to the reflected pulse and it propagates in the superluminal region. Such simple control can be used in all optical switching. (paper)

  15. Angular dependence of the exchange bias for the bistable state

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Yuhao [College of Physics and Electronic Information, Shanxi Normal University, Linfen 041004 (China); Research College of materials science, Shanxi Normal University, Linfen 041004 (China); Xu, Xiaohong, E-mail: xuxh@dns.sxnu.edu.cn [Research College of materials science, Shanxi Normal University, Linfen 041004 (China); Key Laboratory of Magnetic Molecules and Magnetic Information Materials, Ministry of Education, Shanxi Normal University, Linfen 041004 (China)

    2017-06-15

    The angular dependence of the exchange bias (ADEB) has been investigated in detail when the exchange-coupled ferromagnetic (FM)/antiferromagnetic (AFM) bilayer is in the bistable state. Complete and incomplete jump phenomena were found at the intrinsic easy and hard axes, when they pass through two special positions making the angular deviation of 58.2826° and 121.7174° from the easy axis of the uniaxial anisotropy, respectively. The combination of these different types of the jump phenomena at the intrinsic easy and hard axes yields five distinct types of the ADEB. The physical condition for each type of ADEB is established. Additionally, the extreme value problem of the exchange bias field and coercivity are also discussed, which is an important technological issue in the design of the magnetoresistive and spintronic devices. These results enable us to make a comprehensive understanding of the experimental ADEB curves.

  16. Synaptic Bistability Due to Nucleation and Evaporation of Receptor Clusters

    KAUST Repository

    Burlakov, V. M.

    2012-01-10

    We introduce a bistability mechanism for long-term synaptic plasticity based on switching between two metastable states that contain significantly different numbers of synaptic receptors. One state is characterized by a two-dimensional gas of mobile interacting receptors and is stabilized against clustering by a high nucleation barrier. The other state contains a receptor gas in equilibrium with a large cluster of immobile receptors, which is stabilized by the turnover rate of receptors into and out of the synapse. Transitions between the two states can be initiated by either an increase (potentiation) or a decrease (depotentiation) of the net receptor flux into the synapse. This changes the saturation level of the receptor gas and triggers nucleation or evaporation of receptor clusters. © 2012 American Physical Society.

  17. Controllable optical bistability and multistability in a graphene monolayer system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Duo, E-mail: zhangduo10@126.com [School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Sun, Zhaoyu [School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Ding, Chunling [School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Yu, Rong [School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073 (China); Yang, Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2016-02-15

    We theoretically investigate the behavior of optical bistability (OB) and optical multistability (OM) in a graphene monolayer system driven by an elliptically polarized control field and a right-hand circularly polarized probe field. Our numerical results show that it is easy to realize the transition from OB to OM or vice versa by adjusting the frequency detunings of the probe field and the control field, as well as the polarization-dependent phase difference between the two components of the control laser field. The influences of the intensity of the control field and the cooperation parameter on the OB behavior are also discussed in detail. These results may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

  18. Coherent-feedback-induced controllable optical bistability and photon blockade

    International Nuclear Information System (INIS)

    Liu, Yu-Long; Liu, Zhong-Peng; Zhang, Jing

    2015-01-01

    It is well known that some nonlinear phenomena such as strong photon blockade are difficult to observe in optomechanical systems with current experimental technology. Here we present a coherent feedback control strategy in which a linear cavity is coherently controlled by an optomechanical controller in a feedback manner. The coherent feedback loop transfers quantum nonlinearity from the controller to the controlled cavity causing destructive quantum interference to occur, and making it possible to observe strong nonlinear effects. With the help of the coherent feedback loop, large and tunable bistability and strong photon blockade of the cavity modes can be achieved even in the optomechanical weak coupling regime. Additionally, the coherent feedback loop leads to two-photon and multiphoton tunnelings for the controlled linear cavity, which are also typical quantum nonlinear phenomena. We hope that our work can give new perspectives on engineering nonlinear interactions in quantum systems. (paper)

  19. Oscillatory bistability of real-space transfer in semiconductor heterostructures

    Science.gov (United States)

    Do˙ttling, R.; Scho˙ll, E.

    1992-01-01

    Charge transport parallel to the layers of a modulation-doped GaAs/AlxGa1-xAs heterostructure is studied theoretically. The heating of electrons by the applied electric field leads to real-space transfer of electrons from the GaAs into the adjacent AlxGa1-xAs layer. For sufficiently large dc bias, spontaneous periodic 100-GHz current oscillations, and bistability and hysteretic switching transitions between oscillatory and stationary states are predicted. We present a detailed investigation of complex bifurcation scenarios as a function of the bias voltage U0 and the load resistance RL. For large RL subcritical Hopf bifurcations and global bifurcations of limit cycles are displayed.

  20. Optical bistability of optical fiber ring doped by Erbium and quantum dots

    International Nuclear Information System (INIS)

    Safari, S.; Tofighi, S.; Bahrampour, A.; Sajad, B.; Shahshahani, F.

    2012-01-01

    In this paper, theoretical analysis of the steady state behavior of the optical bistability in an optical fiber ring doped by Erbium and quantum dots is presented. The up and down switching power is calculated and the dependence of the switching power on different fiber ring parameters is investigated. The switching power for this type of optical bistability device is obtained much lower than the fiber ring which its half length is doped by Erbium ion.

  1. A predictive coding account of bistable perception - a model-based fMRI study.

    Directory of Open Access Journals (Sweden)

    Veith Weilnhammer

    2017-05-01

    Full Text Available 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. Data simulations revealed close similarities between the model's predictions and key temporal characteristics of perceptual bistability, indicating that the model was able to reproduce bistable perception. Fitting the predictive coding model to behavioural data from an fMRI-experiment on bistable perception, we found a correlation across participants between the model parameter encoding perceptual stabilization and the behaviourally measured frequency of perceptual transitions, corroborating that the model successfully accounted for participants' perception. Formal model comparison with established models of bistable perception based on mutual inhibition and adaptation, noise or a combination of adaptation and noise was used for the validation of the predictive coding model against the established models. Most importantly, model-based analyses of the fMRI data revealed that prediction error time-courses derived from the predictive coding model correlated with neural signal time-courses in bilateral inferior frontal gyri and anterior insulae. Voxel-wise model selection indicated a superiority of the predictive coding model over conventional analysis approaches in explaining neural activity in these frontal areas, suggesting that frontal cortex encodes prediction errors that mediate endogenous perceptual transitions in bistable perception. Taken together

  2. Bistability of heat transfer of a viscous liquid under conditions of flow channel

    International Nuclear Information System (INIS)

    Melkikh, A.V.; Seleznev, V.D.

    2001-01-01

    The heat exchange model for a viscous liquid flowing under the pressure drop effect in a tube, surrounded by the medium with a lower temperature, is considered. It is shown that the system bistable behavior is possible by availability of the liquid viscosity exponential dependence on the temperature and by negligible dissipative heat release. The transitions between cold and hot flows in this case should proceed by a jump. The liquid and channel parameters, whereby the bistability may be observed, are determined [ru

  3. Heat dissipation and information flow for delayed bistable Langevin systems near coherence resonance.

    Science.gov (United States)

    Xiao, Tiejun

    2016-11-01

    In this paper, stochastic thermodynamics of delayed bistable Langevin systems near coherence resonance is discussed. We calculate the heat dissipation rate and the information flow of a delayed bistable Langevin system under various noise intensities. Both the heat dissipation rate and the information flow are found to be bell-shaped functions of the noise intensity, which implies that coherence resonance manifests itself in the thermodynamic properties.

  4. Bistable laser device with multiple coupled active vertical-cavity resonators

    Science.gov (United States)

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-08-19

    A new class of bistable coupled-resonator vertical-cavity semiconductor laser devices has been developed. These bistable laser devices can be switched, either electrically or optically, between lasing and non-lasing states. A switching signal with a power of a fraction of a milliwatt can change the laser output of such a device by a factor of a hundred, thereby enabling a range of optical switching and data encoding applications.

  5. A predictive coding account of bistable perception - a model-based fMRI study.

    Science.gov (United States)

    Weilnhammer, Veith; Stuke, Heiner; Hesselmann, Guido; Sterzer, Philipp; Schmack, Katharina

    2017-05-01

    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. Data simulations revealed close similarities between the model's predictions and key temporal characteristics of perceptual bistability, indicating that the model was able to reproduce bistable perception. Fitting the predictive coding model to behavioural data from an fMRI-experiment on bistable perception, we found a correlation across participants between the model parameter encoding perceptual stabilization and the behaviourally measured frequency of perceptual transitions, corroborating that the model successfully accounted for participants' perception. Formal model comparison with established models of bistable perception based on mutual inhibition and adaptation, noise or a combination of adaptation and noise was used for the validation of the predictive coding model against the established models. Most importantly, model-based analyses of the fMRI data revealed that prediction error time-courses derived from the predictive coding model correlated with neural signal time-courses in bilateral inferior frontal gyri and anterior insulae. Voxel-wise model selection indicated a superiority of the predictive coding model over conventional analysis approaches in explaining neural activity in these frontal areas, suggesting that frontal cortex encodes prediction errors that mediate endogenous perceptual transitions in bistable perception. Taken together, our current work

  6. Evidence for distinct mechanisms underlying attentional priming and sensory memory for bistable perception.

    Science.gov (United States)

    Brinkhuis, M A B; Kristjánsson, Á; Brascamp, J W

    2015-08-01

    Attentional selection in visual search paradigms and perceptual selection in bistable perception paradigms show functional similarities. For example, both are sensitive to trial history: They are biased toward previously selected targets or interpretations. We investigated whether priming by target selection in visual search and sensory memory for bistable perception are related. We did this by presenting two trial types to observers. We presented either ambiguous spheres that rotated over a central axis and could be perceived as rotating in one of two directions, or search displays in which the unambiguously rotating target and distractor spheres closely resembled the two possible interpretations of the ambiguous stimulus. We interleaved both trial types within experiments, to see whether priming by target selection during search trials would affect the perceptual outcome of bistable perception and, conversely, whether sensory memory during bistable perception would affect target selection times during search. Whereas we found intertrial repetition effects among consecutive search trials and among consecutive bistable trials, we did not find cross-paradigm effects. Thus, even though we could ascertain that our experiments robustly elicited processes of both search priming and sensory memory for bistable perception, these same experiments revealed no interaction between the two.

  7. Cell individuality: the bistable gene expression of the type III secretion system in Dickeya dadantii 3937.

    Science.gov (United States)

    Zeng, Quan; Laiosa, Michael D; Steeber, Douglas A; Biddle, Eulandria M; Peng, Quan; Yang, Ching-Hong

    2012-01-01

    Dickeya dadantii 3937 is a gram-negative phytopathogenic bacterium that expresses genes encoding a type III secretion system (T3SS) in a bistable pattern when cultured in a homogeneous minimal media. In this work, we further characterized the bistable gene expression of T3SS at the single-cell level. We demonstrated that bistable expression of the HrpL-regulon genes, such as hrpA and hrpN, is controlled by the same regulatory mechanism. We also showed that the expression level of the T3SS master regulatory gene hrpL plays an important role in the development of the bistable expression of hrpA. A high expression level of hrpL is required but unable to guarantee the high-state expression of hrpA in a cell. In addition, bistable expression patterns of T3SS genes in other gram-negative pathogens of the Enterobacteriaceae and Pseudomonadaceae families were also described in this study. This suggests that the T3SS bistability might be a conserved population behavior in several gram-negative bacterial pathogens.

  8. Investigation of a bistable dual-stage vibration isolator under harmonic excitation

    International Nuclear Information System (INIS)

    Yang, Kai; Huang, Hai; Harne, R L; Wang, K W

    2014-01-01

    This study explores the steady-state performance of a dual-stage vibration isolator, which is configured by a bistable oscillator and a linear oscillator. The potential force of the bistable stage comprises negative linear and positive cubic nonlinear stiffnesses such that the two restoring force contributions may counterbalance to minimize dynamic force transmission. By applying a first-order harmonic balance, it is predicted that the bistable dual-stage isolator may significantly outperform an equivalent pure linear dual-stage isolator. This conclusion is verified through a series of numerical investigations. Following a parametric study, design guidelines are detailed to achieve performance improvements. Then, the ‘valley’ response, which is the special phenomenon of the bistable dual-stage isolator due to the counterbalance of the negative linear and positive nonlinear potential forces, is revealed and quantitatively explained. Numerical studies demonstrate the role of initial conditions, and it is shown that the likelihood of beneficial single periodic valley and intra-well responses for isolation purposes can be increased by greater bistable stage damping. Finally, a bistable dual-stage isolator prototype is developed and tested, and the numerical and experimental results verify the theoretical predictions. (paper)

  9. Magnetic-field induced bistability in a quasi-one-dimensional semiconductor microcavity

    International Nuclear Information System (INIS)

    Zhang, Chuanyi; Zhang, Weifeng

    2015-01-01

    We theoretically study the magnetic-field induced bistability in a quasi-one-dimensional semiconductor microcavity. A critical magnetic field is obtained, and the bistability appears if a magnetic field is greater than the critical value. For a positive energy detuning of the pump from the bare exciton polaritons, one bistability loop first emerges, then it divides into two loops, and finally one of them vanishes with the increasing magnetic field. This phenomenon originates from the magnetic-field modulated interactions for opposite spins. In the variational process, there are two important effects: one is a logic gate with a small variation of the excitation laser, and the other is a spin texture like skyrmion and this texture is periodic if the energy detuning varies periodically in real space, which is useful for designing the spin-dependent optoelectronic devices. - Highlights: • We study the bistability induced by a magnetic field in a microcavity. • One bistability loop can divide into two, and then the two loops return to one. • A spin texture like skyrmion and logic gate arise in the variation of bistability loop

  10. Solvent Vapour Detection with Cholesteric Liquid Crystals—Optical and Mass-Sensitive Evaluation of the Sensor Mechanism

    Directory of Open Access Journals (Sweden)

    Adnan Mujahid

    2010-05-01

    Full Text Available Cholesteric liquid crystals (CLCs are used as sensitive coatings for the detection of organic solvent vapours for both polar and non-polar substances. The incorporation of different analyte vapours in the CLC layers disturbs the pitch length which changes the optical properties, i.e., shifting the absorption band. The engulfing of CLCs around non-polar solvent vapours such as tetrahedrofuran (THF, chloroform and tetrachloroethylene is favoured in comparison to polar ones, i.e., methanol and ethanol. Increasing solvent vapour concentrations shift the absorbance maximumto smaller wavelengths, e.g., as observed for THF. Additionally, CLCs have been coated on acoustic devices such as the quartz crystal microbalance (QCM to measure the frequency shift of analyte samples at similar concentration levels. The mass effect for tetrachloroethylene was about six times higher than chloroform. Thus, optical response can be correlated with intercalation in accordance to mass detection. The mechanical stability was gained by combining CLCs with imprinted polymers. Therefore, pre-concentration of solvent vapours was performed leading to an additional selectivity.

  11. An Ambipolar BODIPY Derivative for a White Exciplex OLED and Cholesteric Liquid Crystal Laser toward Multifunctional Devices.

    Science.gov (United States)

    Chapran, Marian; Angioni, Enrico; Findlay, Neil J; Breig, Benjamin; Cherpak, Vladyslav; Stakhira, Pavlo; Tuttle, Tell; Volyniuk, Dmytro; Grazulevicius, Juozas V; Nastishin, Yuriy A; Lavrentovich, Oleg D; Skabara, Peter J

    2017-02-08

    A new interface engineering method is demonstrated for the preparation of an efficient white organic light-emitting diode (WOLED) by embedding an ultrathin layer of the novel ambipolar red emissive compound 4,4-difluoro-2,6-di(4-hexylthiopen-2-yl)-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (bThBODIPY) in the exciplex formation region. The compound shows a hole and electron mobility of 3.3 × 10 -4 and 2 × 10 -4 cm 2 V -1 s -1 , respectively, at electric fields higher than 5.3 × 10 5 V cm -1 . The resulting WOLED exhibited a maximum luminance of 6579 cd m -2 with CIE 1931 color coordinates (0.39; 0.35). The bThBODIPY dye is also demonstrated to be an effective laser dye for a cholesteric liquid crystal (ChLC) laser. New construction of the ChLC laser, by which a flat capillary with an optically isotropic dye solution is sandwiched between two dye-free ChLC cells, provides photonic lasing at a wavelength well matched with that of a dye-doped planar ChLC cell.

  12. Bulk chirality effect for symmetric bistable switching of liquid crystals on topologically self-patterned degenerate anchoring surface.

    Science.gov (United States)

    Park, Min-Kyu; Joo, Kyung-Il; Kim, Hak-Rin

    2017-06-26

    We demonstrate a bistable switching liquid crystal (LC) mode utilizing a topologically self-structured dual-groove surface for degenerated easy axes of LC anchoring. In our study, the effect of the bulk elastic distortion of the LC directors on the bistable anchoring surface is theoretically analyzed for balanced bistable states based on a free energy diagram. By adjusting bulk LC chirality, we developed ideally symmetric and stable bistable anchoring and switching properties, which can be driven by a low in-plane pulsed field of about 0.7 V/µm. The fabricated device has a contrast ratio of 196:1.

  13. The effect of magnetic field on bistability in 1D photonic crystal doped by magnetized plasma and coupled nonlinear defects

    International Nuclear Information System (INIS)

    Mehdian, H.; Mohammadzahery, Z.; Hasanbeigi, A.

    2014-01-01

    In this work, we study the defect mode and bistability behavior of 1-D photonic band gap structure with magnetized plasma and coupled nonlinear defects. The transfer matrix method has been employed to investigate the magnetic field effect on defect mode frequency and bistability threshold. The obtained results show that the frequency of defect mode and bistability threshold can be altered, without changing the structure of the photonic multilayer. Therefore, the bistability behavior of the subjected structure in the presence of magnetized plasma can be utilized in manufacturing wide frequency range devices

  14. Influence of Fano interference and incoherent processes on optical bistability in a four-level quantum dot nanostructure

    International Nuclear Information System (INIS)

    Hossein Asadpour, Seyyed; Solookinejad, G; Panahi, M; Ahmadi Sangachin, E

    2016-01-01

    Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed InGaN/GaN quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily. (paper)

  15. Conditional bistability, a generic cellular mnemonic mechanism for robust and flexible working memory computations.

    Science.gov (United States)

    Rodriguez, Guillaume; Sarazin, Matthieu; Clemente, Alexandra; Holden, Stephanie; Paz, Jeanne T; Delord, Bruno

    2018-04-30

    Persistent neural activity, the substrate of working memory, is thought to emerge from synaptic reverberation within recurrent networks. However, reverberation models do not robustly explain fundamental dynamics of persistent activity, including high-spiking irregularity, large intertrial variability, and state transitions. While cellular bistability may contribute to persistent activity, its rigidity appears incompatible with persistent activity labile characteristics. Here, we unravel in a cellular model a form of spike-mediated conditional bistability that is robust, generic and provides a rich repertoire of mnemonic computations. Under asynchronous synaptic inputs of the awakened state, conditional bistability generates spiking/bursting episodes, accounting for the irregularity, variability and state transitions characterizing persistent activity. This mechanism has likely been overlooked because of the sub-threshold input it requires and we predict how to assess it experimentally. Our results suggest a reexamination of the role of intrinsic properties in the collective network dynamics responsible for flexible working memory. SIGNIFICANCE STATEMENT This study unravels a novel form of intrinsic neuronal property, i.e. conditional bistability. We show that, thanks of its conditional character, conditional bistability favors the emergence of flexible and robust forms of persistent activity in PFC neural networks, in opposition to previously studied classical forms of absolute bistability. Specifically, we demonstrate for the first time that conditional bistability 1) is a generic biophysical spike-dependent mechanism of layer V pyramidal neurons in the PFC and that 2) it accounts for essential neurodynamical features for the organisation and flexibility of PFC persistent activity (the large irregularity and intertrial variability of the discharge and its organization under discrete stable states), which remain unexplained in a robust fashion by current models

  16. Dynamics and control of twisting bi-stable structures

    Science.gov (United States)

    Arrieta, Andres F.; van Gemmeren, Valentin; Anderson, Aaron J.; Weaver, Paul M.

    2018-02-01

    Compliance-based morphing structures have the potential to offer large shape adaptation, high stiffness and low weight, while reducing complexity, friction, and scalability problems of mechanism based systems. A promising class of structure that enables these characteristics are multi-stable structures given their ability to exhibit large deflections and rotations without the expensive need for continuous actuation, with the latter only required intermittently. Furthermore, multi-stable structures exhibit inherently fast response due to the snap-through instability governing changes between stable states, enabling rapid configuration switching between the discrete number of programmed shapes of the structure. In this paper, the design and utilisation of the inherent nonlinear dynamics of bi-stable twisting I-beam structures for actuation with low strain piezoelectric materials is presented. The I-beam structure consists of three compliant components assembled into a monolithic single element, free of moving parts, and showing large deflections between two stable states. Finite element analysis is utilised to uncover the distribution of strain across the width of the flange, guiding the choice of positioning for piezoelectric actuators. In addition, the actuation authority is maximised by calculating the generalised coupling coefficient for different positions of the piezoelectric actuators. The results obtained are employed to tailor and test I-beam designs exhibiting desired large deflection between stable states, while still enabling the activation of snap-through with the low strain piezoelectric actuators. To this end, the dynamic response of the I-beams to piezoelectric excitation is investigated, revealing that resonant excitations are insufficient to dynamically trigger snap-through. A novel bang-bang control strategy, which exploits the nonlinear dynamics of the structure successfully triggers both single and constant snap-through between the stable states

  17. Asymmetric bistable reflection and polarization switching in a magnetic nonlinear multilayer structure

    DEFF Research Database (Denmark)

    Tuz, Vladimir R.; Novitsky, Denis V.; Prosvirnin, Sergey L.

    2014-01-01

    Optical properties of one-dimensional photonic structures consisting of Kerr-type nonlinear and magnetic layers under the action of an external static magnetic field in the Faraday geometry are investigated. The structure is a periodic arrangement of alternating nonlinear and magnetic layers (a o...

  18. Reflecting reflection in supervision

    DEFF Research Database (Denmark)

    Lystbæk, Christian Tang

    associated with reflection and an exploration of alternative conceptions that view reflection within the context of settings which have a more group- and team-based orientation. Drawing on an action research project on health care supervision, the paper questions whether we should reject earlier views...... of reflection, rehabilitate them in order to capture broader connotations or move to new ways of regarding reflection that are more in keeping with not only reflective but also emotive, normative and formative views on supervision. The paper presents a critical perspective on supervision that challenge...... the current reflective paradigm I supervision and relate this to emotive, normative and formative views supervision. The paper is relevant for Nordic educational research into the supervision and guidance...

  19. Rac1 and RhoA: Networks, loops and bistability.

    Science.gov (United States)

    Nguyen, Lan K; Kholodenko, Boris N; von Kriegsheim, Alex

    2016-08-17

    Cell migration requires a precise temporal and spatial coordination of several processes which allow the cell to efficiently move. The extension and retraction of membrane protrusion, as well as adhesion are controlled by the Rho-family small GTPases. Two members of the family, Rac1 and RhoA, can show opposite behaviors and spatial localisations, with RhoA being active toward the rear of the cell and regulating its retraction during migration, whereas Rac1 is active toward the front of the cell. In addition to the spatial segregation, RhoA and Rac1 activity at the leading edge of the cells has an element of temporal segregation, with RhoA and Rac1 activities peaking at separate points during the migratory cycle of protrusion and retraction. Elements of this separation have been explained by the presence of 2 mutually inhibitory feedbacks, where Rac1 inhibits RhoA and RhoA in turn can inhibit Rac1. Recently, it was shown that Rac1 and RhoA activity and downstream signaling respond in a bistable manner to perturbations of this network.

  20. Hindrances to bistable front propagation: application to Wolbachia invasion.

    Science.gov (United States)

    Nadin, Grégoire; Strugarek, Martin; Vauchelet, Nicolas

    2018-05-01

    We study the biological situation when an invading population propagates and replaces an existing population with different characteristics. For instance, this may occur in the presence of a vertically transmitted infection causing a cytoplasmic effect similar to the Allee effect (e.g. Wolbachia in Aedes mosquitoes): the invading dynamics we model is bistable. We aim at quantifying the propagules (what does it take for an invasion to start?) and the invasive power (how far can an invading front go, and what can stop it?). We rigorously show that a heterogeneous environment inducing a strong enough population gradient can stop an invading front, which will converge in this case to a stable front. We characterize the critical population jump, and also prove the existence of unstable fronts above the stable (blocking) fronts. Being above the maximal unstable front enables an invading front to clear the obstacle and propagate further. We are particularly interested in the case of artificial Wolbachia infection, used as a tool to fight arboviruses.

  1. Nonlinear response and bistability of driven ion acoustic waves

    Science.gov (United States)

    Akbari-Moghanjoughi, M.

    2017-08-01

    The hydrodynamic model is used to obtain a generalized pseudoforce equation through which the nonlinear response of periodically driven ion acoustic waves is studied in an electron-ion plasma with isothermal and adiabatic ion fluids. The pseudotime series, corresponding to different driving frequencies, indicates that nonlinearity effects appear more strongly for smaller frequency values. The existence of extra harmonic resonances in the nonlinear amplitude spectrum is a clear indication of the interaction of an external force with harmonic components of the nonlinear ion acoustic waves. It is shown that many plasma parameters significantly and differently affect the nonlinear resonance spectrum of ion acoustic excitations. A heuristic but accurate model for the foldover effect is used which quite satisfactorily predicts the bistability of driven plasma oscillations. It is remarked that the characteristic resonance peak of isothermal ion plasma oscillations appears at lower frequencies but is stronger compared to that of adiabatic ions. Comparison of the exact numerical results for fully nonlinear and approximate (weakly nonlinear) models indicates that a weakly nonlinear model exaggerates the hysteresis and jump phenomenon for higher values of the external force amplitude.

  2. On the functional relevance of frontal cortex for passive and voluntarily controlled bistable vision.

    Science.gov (United States)

    de Graaf, Tom A; de Jong, Maartje C; Goebel, Rainer; van Ee, Raymond; Sack, Alexander T

    2011-10-01

    In bistable vision, one constant ambiguous stimulus leads to 2 alternating conscious percepts. This perceptual switching occurs spontaneously but can also be influenced through voluntary control. Neuroimaging studies have reported that frontal regions are activated during spontaneous perceptual switches, leading some researchers to suggest that frontal regions causally induce perceptual switches. But the opposite also seems possible: frontal activations may themselves be caused by spontaneous switches. Classically implicated in attentional processes, these same regions are also candidates for the origins of voluntary control over bistable vision. Here too, it remains unknown whether frontal cortex is actually functionally relevant. It is even possible that spontaneous perceptual switches and voluntarily induced switches are mediated by the same top-down mechanisms. To directly address these issues, we here induced "virtual lesions," with transcranial magnetic stimulation, in frontal, parietal, and 2 lower level visual cortices using an established ambiguous structure-from-motion stimulus. We found that dorsolateral prefrontal cortex was causally relevant for voluntary control over perceptual switches. In contrast, we failed to find any evidence for an active role of frontal cortex in passive bistable vision. Thus, it seems the same pathway used for willed top-down modulation of bistable vision is not used during passive bistable viewing.

  3. Investigation of bistable perception with the "silhouette spinner": sit still, spin the dancer with your will.

    Science.gov (United States)

    Liu, Chao-Hsuan; Tzeng, Ovid J L; Hung, Daisy L; Tseng, Philip; Juan, Chi-Hung

    2012-05-01

    Many studies have used static and non-biologically related stimuli to investigate bistable perception and found that the percept is usually dominated by their intrinsic nature with some influence of voluntary control from the viewer. Here we used a dynamic stimulus of a rotating human body, the silhouette spinner illusion, to investigate how the viewers' intentions may affect their percepts. In two experiments, we manipulated observer intention (active or passive), fixation position (body or feet), and spinning velocity (fast, medium, or slow). Our results showed that the normalized alternating rate between two bistable percepts was greater when (1) participants actively attempted to switch percepts, (2) when participants fixated at the spinner's feet rather than the body, inducing as many as 25 switches of the bistable percepts within 1 min, and (3) when they watched the spinner at high velocity. These results suggest that a dynamic biologically-bistable percept can be quickly alternated by the viewers' intention. Furthermore, the higher alternating rate in the feet condition compared to the body condition suggests a role for biological meaningfulness in determining bistable percepts, where 'biologically plausible' interpretations are favored by the visual system. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. Revisiting the Lissajous figure as a tool to study bistable perception.

    Science.gov (United States)

    Weilnhammer, V A; Ludwig, K; Sterzer, P; Hesselmann, G

    2014-05-01

    During bistable vision perception spontaneously "switches" between two mutually exclusive percepts despite constant sensory input. The endogenous nature of these perceptual transitions has motivated extensive research aimed at the underlying mechanisms, since spontaneous perceptual transitions of bistable stimuli should in principle allow for a dissociation of processes related to sensory stimulation from those related to conscious perception. However, transitions from one conscious percept to another are often not instantaneous, and participants usually report a considerable amount of mixed or unclear percepts. This feature of bistable vision makes it difficult to isolate transition-related visual processes. Here, we revisited an ambiguous depth-from-motion stimulus which was first introduced to experimental psychology more than 80 years ago. This rotating Lissajous figure might prove useful in complementing other bistable stimuli, since its perceptual transitions only occur at critical stimulus configurations and are virtually instantaneous, thus facilitating the construction of a perceptually equivalent replay condition. We found that three parameters of the Lissajous figure - complexity, line width, and rotational speed - differentially modulated its perceptual dominance durations and transition probabilities, thus providing experimenters with a versatile tool to study the perceptual dynamics of bistable vision. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Maximizing direct current power delivery from bistable vibration energy harvesting beams subjected to realistic base excitations

    Science.gov (United States)

    Dai, Quanqi; Harne, Ryan L.

    2017-04-01

    Effective development of vibration energy harvesters is required to convert ambient kinetic energy into useful electrical energy as power supply for sensors, for example in structural health monitoring applications. Energy harvesting structures exhibiting bistable nonlinearities have previously been shown to generate large alternating current (AC) power when excited so as to undergo snap-through responses between stable equilibria. Yet, most microelectronics in sensors require rectified voltages and hence direct current (DC) power. While researchers have studied DC power generation from bistable energy harvesters subjected to harmonic excitations, there remain important questions as to the promise of such harvester platforms when the excitations are more realistic and include both harmonic and random components. To close this knowledge gap, this research computationally and experimentally studies the DC power delivery from bistable energy harvesters subjected to such realistic excitation combinations as those found in practice. Based on the results, it is found that the ability for bistable energy harvesters to generate peak DC power is significantly reduced by introducing sufficient amount of stochastic excitations into an otherwise harmonic input. On the other hand, the elimination of a low amplitude, coexistent response regime by way of the additive noise promotes power delivery if the device was not originally excited to snap-through. The outcomes of this research indicate the necessity for comprehensive studies about the sensitivities of DC power generation from bistable energy harvester to practical excitation scenarios prior to their optimal deployment in applications.

  6. Elastic energy for reflection-symmetric topologies

    International Nuclear Information System (INIS)

    Majumdar, A; Robbins, J M; Zyskin, M

    2006-01-01

    Nematic liquid crystals in a polyhedral domain, a prototype for bistable displays, may be described by a unit-vector field subject to tangent boundary conditions. Here we consider the case of a rectangular prism. For configurations with reflection-symmetric topologies, we derive a new lower bound for the one-constant elastic energy. For certain topologies, called conformal and anticonformal, the lower bound agrees with a previous result. For the remaining topologies, called nonconformal, the new bound is an improvement. For nonconformal topologies we derive an upper bound, which differs from the lower bound by a factor depending only on the aspect ratios of the prism

  7. Bistability, non-ergodicity, and inhibition in pairwise maximum-entropy models.

    Science.gov (United States)

    Rostami, Vahid; Porta Mana, PierGianLuca; Grün, Sonja; Helias, Moritz

    2017-10-01

    Pairwise maximum-entropy models have been used in neuroscience to predict the activity of neuronal populations, given only the time-averaged correlations of the neuron activities. This paper provides evidence that the pairwise model, applied to experimental recordings, would produce a bimodal distribution for the population-averaged activity, and for some population sizes the second mode would peak at high activities, that experimentally would be equivalent to 90% of the neuron population active within time-windows of few milliseconds. Several problems are connected with this bimodality: 1. The presence of the high-activity mode is unrealistic in view of observed neuronal activity and on neurobiological grounds. 2. Boltzmann learning becomes non-ergodic, hence the pairwise maximum-entropy distribution cannot be found: in fact, Boltzmann learning would produce an incorrect distribution; similarly, common variants of mean-field approximations also produce an incorrect distribution. 3. The Glauber dynamics associated with the model is unrealistically bistable and cannot be used to generate realistic surrogate data. This bimodality problem is first demonstrated for an experimental dataset from 159 neurons in the motor cortex of macaque monkey. Evidence is then provided that this problem affects typical neural recordings of population sizes of a couple of hundreds or more neurons. The cause of the bimodality problem is identified as the inability of standard maximum-entropy distributions with a uniform reference measure to model neuronal inhibition. To eliminate this problem a modified maximum-entropy model is presented, which reflects a basic effect of inhibition in the form of a simple but non-uniform reference measure. This model does not lead to unrealistic bimodalities, can be found with Boltzmann learning, and has an associated Glauber dynamics which incorporates a minimal asymmetric inhibition.

  8. Improved estimates for the role of grey matter volume and GABA in bistable perception.

    Science.gov (United States)

    Sandberg, Kristian; Blicher, Jakob Udby; Del Pin, Simon Hviid; Andersen, Lau Møller; Rees, Geraint; Kanai, Ryota

    2016-10-01

    Across a century or more, ambiguous stimuli have been studied scientifically because they provide a method for studying the internal mechanisms of the brain while ensuring an unchanging external stimulus. In recent years, several studies have reported correlations between perceptual dynamics during bistable perception and particular brain characteristics such as the grey matter volume of areas in the superior parietal lobule (SPL) and the relative GABA concentration in the occipital lobe. Here, we attempt to replicate previous results using similar paradigms to those used in the studies first reporting the correlations. Using the original findings as priors for Bayesian analyses, we found strong support for the correlation between structure-from-motion percept duration and anterior SPL grey matter volume. Correlations between percept duration and other parietal areas as well as occipital GABA, however, were not directly replicated or appeared less strong than previous studies suggested. Inspection of the posterior distributions (current "best guess" based on new data given old data as prior) revealed that several original findings may reflect true relationships although no direct evidence was found in support of them in the current sample. Additionally, we found that multiple regression models based on grey matter volume at 2-3 parietal locations (but not including GABA) were the best predictors of percept duration, explaining approximately 35% of the inter-individual variance. Taken together, our results provide new estimates of correlation strengths, generally increasing confidence in the role of the aSPL while decreasing confidence in some of the other relationships. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Unstable Modes and Order Parameters of Bistable Signaling Pathways at Saddle-Node Bifurcations: A Theoretical Study Based on Synergetics

    Directory of Open Access Journals (Sweden)

    Till D. Frank

    2016-01-01

    Full Text Available Mathematical modeling has become an indispensable part of systems biology which is a discipline that has become increasingly popular in recent years. In this context, our understanding of bistable signaling pathways in terms of mathematical modeling is of particular importance because such bistable components perform crucial functions in living cells. Bistable signaling pathways can act as switches or memory functions and can determine cell fate. In the present study, properties of mathematical models of bistable signaling pathways are examined from the perspective of synergetics, a theory of self-organization and pattern formation founded by Hermann Haken. At the heart of synergetics is the concept of so-called unstable modes or order parameters that determine the behavior of systems as a whole close to bifurcation points. How to determine these order parameters for bistable signaling pathways at saddle-node bifurcation points is shown. The procedure is outlined in general and an explicit example is worked out in detail.

  10. Bistable behavior of the lac operon in E. coli when induced with a mixture of lactose and TMG

    Directory of Open Access Journals (Sweden)

    Orlando Díaz-Hernández

    2010-07-01

    Full Text Available In this work we investigate multistability in the lac operon of Escherichia coli when it is induced by a mixture of lactose and the non-metabolizable thiomethyl galactoside (TMG. In accordance with previously published experimental results and computer simulations, our simulations predict that: (1 when the system is induced by TMG, the system shows a discernible bistable behavior while, (2 when the system is induced by lactose, bistability does not disappear but excessively high concentrations of lactose would be required to observe it. Finally, our simulation results predict that when a mixture of lactose and TMG is used, the bistability region in the extracellular glucose concentration vs. extracellular lactose concentration parameter space changes in such a way that the model predictions regarding bistability could be tested experimentally. These experiments could help to solve a recent controversy regarding the existence of bistability in the lac operon under natural conditions.

  11. Bistable behavior of the lac operon in E. coli when induced with a mixture of lactose and TMG.

    Science.gov (United States)

    Díaz-Hernández, Orlando; Santillán, Moisés

    2010-01-01

    In this work we investigate multistability in the lac operon of Escherichia coli when it is induced by a mixture of lactose and the non-metabolizable thiomethyl galactoside (TMG). In accordance with previously published experimental results and computer simulations, our simulations predict that: (1) when the system is induced by TMG, the system shows a discernible bistable behavior while, (2) when the system is induced by lactose, bistability does not disappear but excessively high concentrations of lactose would be required to observe it. Finally, our simulation results predict that when a mixture of lactose and TMG is used, the bistability region in the extracellular glucose concentration vs. extracellular lactose concentration parameter space changes in such a way that the model predictions regarding bistability could be tested experimentally. These experiments could help to solve a recent controversy regarding the existence of bistability in the lac operon under natural conditions.

  12. Bistability induces episodic spike communication by inhibitory neurons in neuronal networks.

    Science.gov (United States)

    Kazantsev, V B; Asatryan, S Yu

    2011-09-01

    Bistability is one of the important features of nonlinear dynamical systems. In neurodynamics, bistability has been found in basic Hodgkin-Huxley equations describing the cell membrane dynamics. When the neuron is clamped near its threshold, the stable rest potential may coexist with the stable limit cycle describing periodic spiking. However, this effect is often neglected in network computations where the neurons are typically reduced to threshold firing units (e.g., integrate-and-fire models). We found that the bistability may induce spike communication by inhibitory coupled neurons in the spiking network. The communication is realized in the form of episodic discharges with synchronous (correlated) spikes during the episodes. A spiking phase map is constructed to describe the synchronization and to estimate basic spike phase locking modes.

  13. A computational role for bistability and traveling waves in motor cortex

    Directory of Open Access Journals (Sweden)

    Stewart eHeitmann

    2012-09-01

    Full Text Available Adaptive changes in behavior require rapid changes in brain states yet the brain must also remain stable. We investigated two neural mechanisms for evoking rapid transitions between spatiotemporal synchronization patterns of beta oscillations (13--30Hz in motor cortex. Cortex was modeled as a sheet of neural oscillators that were spatially coupled using a center-surround connection topology. Manipulating the inhibitory surround was found to evoke reliable transitions between synchronous oscillation patterns and traveling waves. These transitions modulated the simulated local field potential in agreement with physiological observations in humans. Intermediate levels of surround inhibition were also found to produce bistable coupling topologies that supported both waves and synchrony. State-dependent perturbation between bistable states produced very rapid transitions but were less reliable. We surmise that motor cortex may thus employ state-dependent computation to achieve very rapid changes between bistable motor states when the demand for speed exceeds the demand for accuracy.

  14. Dynamic and energetic characteristics of a bistable piezoelectric vibration energy harvester with an elastic magnifier

    Science.gov (United States)

    Wang, Guangqing; Liao, Wei-Hsin; Yang, Binqiang; Wang, Xuebao; Xu, Wentan; Li, Xiuling

    2018-05-01

    Bistable piezoelectric energy harvesters are being increasingly seen as an alternative to batteries in low-power devices. However, their energy harvesting characteristics are limited. To enhance these, we use a configuration including an elastic magnifier to amplify base excitation and provide sufficient kinetic energy to overcome potential well barriers, thus leading to large-amplitude bistable motion. We derive the distributed parameter mathematical model of this configuration by using Hamilton's principle. We then investigate the nonlinear dynamic behaviors and energetic characteristics and analyze the bifurcation for the equilibrium solution of the model. The simulations and experiments show high electromechanical responses and energy generation characteristics of the proposed system over a broad frequency band. The results suggest that, compared with a typical bistable piezoelectric energy harvester, the proposed energy harvester system with an elastic magnifier can provide higher output over a broader frequency band at lower excitation levels by adjusting the system's mass and stiffness ratios.

  15. Focused Role of an Organic Small-Molecule PBD on Performance of the Bistable Resistive Switching.

    Science.gov (United States)

    Li, Lei; Sun, Yanmei; Ai, Chunpeng; Lu, Junguo; Wen, Dianzhong; Bai, Xuduo

    2015-12-01

    An undoped organic small-molecule 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) and a kind of nanocomposite blending poly(methyl methacrylate) (PMMA) into PBD are employed to implement bistable resistive switching. For the bistable resistive switching indium tin oxide (ITO)/PBD/Al, its ON/OFF current ratio can touch 6. What is more, the ON/OFF current ratio, approaching to 10(4), is available due to the storage layer PBD:PMMA with the chemical composition 1:1 in the bistable resistive switching ITO/PBD:PMMA/Al. The capacity, data retention of more than 1 year and endurance performance (>10(4) cycles) of ITO/PBD:PMMA(1:1)/Al, exhibits better stability and reliability of the samples, which underpins the technique and application of organic nonvolatile memory.

  16. Experimental Analysis of a Coupled Energy Harvesting System with Monostable and Bistable Configuration

    International Nuclear Information System (INIS)

    Hoffmann, D; Folkmer, B; Manoli, Y

    2014-01-01

    In this paper we present experimental results from an energy harvesting system with two coupled energy harvesters. The energy conversion mechanism of the two coupled energy harvesters is based on the electromagnetic principle. The coupling is generated by two magnets in a repulsive arrangement. In this manner a bistable configuration can be obtained if the gap between the magnets is sufficiently small. We demonstrate that the total power output can be increased in comparison to a linear reference system, if specific conditions are fulfilled. In this respect, the highest power output occurs in the nonlinear region of a monostable system configuration, mostly near the transition to a bistable configuration. On the other hand, the results also indicate, that a bistable operating mode does not necessarily enhance the power output of the coupled system

  17. Low-threshold optical bistability with multilayer graphene-covering Otto configuration

    International Nuclear Information System (INIS)

    Wang, Hengliang; Wu, Jipeng; Xiang, Yuanjiang; Wen, Shuangchun; Guo, Jun; Jiang, Leyong

    2016-01-01

    In this paper, we propose a modified Otto configuration to realize tunable and low-threshold optical bistability at terahertz frequencies by attaching multilayer graphene sheets to a nonlinear substrate interface. Our work demonstrates that the threshold of optical bistability can be markedly reduced (three orders of magnitude) by covering the nonlinear substrate with multilayer graphene sheets, due to strong local field enhancement with the excitation of surface plasmons. We present the influences of the Fermi energy of graphene, the incident angle, the thickness of air gap and the relaxation time of graphene on the hysteresis phenomenon and give a way to optimize the surface plasmon resonance, which will enable us to further lower the minimal power requirements for realizing optical bistability due to the strong interaction of light with graphene sheets. These results are promising for realization of terahertz optical switches, optical modulators and logical devices. (paper)

  18. High-resolution bistable nematic liquid crystal device realized on orientational surface patterns

    International Nuclear Information System (INIS)

    Kim, Jong-Hyun; Yoneya, Makoto; Yokoyama, Hiroshi

    2003-01-01

    The four-fold symmetry of a checkerboard-like surface alignment consisted of square domains arrived at the macroscopic orientational bistability of nematic liquid crystals. Switching between the two orientations took place with an appropriate electric field. Here the threshold field of bistable switching decreased as temperature increased, and the light could heat only the selected region in the cell including a light-absorbing medium. Irradiating the laser concurrently with an electric field, we addressed a selected region in the alignment pattern without the disturbance of neighboring regions. Extending this process, we realized an extremely fine bistable device of nematic liquid crystal with a pixel size down to about 2 μm

  19. Orientational transitions in ferromagnetic liquid crystals with bistable coupling between colloidal particles and the matrix

    Energy Technology Data Exchange (ETDEWEB)

    Zakhlevnykh, A. N., E-mail: anz@psu.ru; Petrov, D. A. [Perm State National Research University (Russian Federation)

    2016-10-15

    We study the orientational response of a ferromagnetic liquid crystal that is induced by magnetic and electric fields. A modified form of the energy of the orientational interaction between magnetic impurity particles and the liquid crystal matrix that leads to bistable coupling is considered. It is shown that apart from magnetic impurity segregation, first-order orientational transitions can be due to the bistability of the potential of the orientational coupling between the director and the magnetization. The ranges of material parameters that lead to optical bistability are determined. The possibility of first-order orientational transitions is analyzed for the optical phase difference between the ordinary and extraordinary light rays transmitted through a ferronematic cell. It is shown that an electric field applied in the given geometry considerably enhances the magneto-orientational response of the ferronematic.

  20. Dynamics of interface in three-dimensional anisotropic bistable reaction-diffusion system

    International Nuclear Information System (INIS)

    He Zhizhu; Liu, Jing

    2010-01-01

    This paper presents a theoretical investigation of dynamics of interface (wave front) in three-dimensional (3D) reaction-diffusion (RD) system for bistable media with anisotropy constructed by means of anisotropic surface tension. An equation of motion for the wave front is derived to carry out stability analysis of transverse perturbations, which discloses mechanism of pattern formation such as labyrinthine in 3D bistable media. Particularly, the effects of anisotropy on wave propagation are studied. It was found that, sufficiently strong anisotropy can induce dynamical instabilities and lead to breakup of the wave front. With the fast-inhibitor limit, the bistable system can further be described by a variational dynamics so that the boundary integral method is adopted to study the dynamics of wave fronts.

  1. Large Out-of-Plane Displacement Bistable Electromagnetic Microswitch on a Single Wafer.

    Science.gov (United States)

    Miao, Xiaodan; Dai, Xuhan; Huang, Yi; Ding, Guifu; Zhao, Xiaolin

    2016-05-05

    This paper presents a bistable microswitch fully batch-fabricated on a single glass wafer, comprising of a microactuator, a signal transformer, a microspring and a permanent magnet. The bistable mechanism of the microswitch with large displacement of 160 μm depends on the balance of the magnetic force and elastic force. Both the magnetic force and elastic force were optimized by finite-element simulation to predict the reliable of the device. The prototype was fabricated and characterized. By utilizing thick laminated photoresist sacrificial layer, the large displacement was obtained to ensure the insulation of the microswitch. The testing results show that the microswitch realized the bistable mechanism at a 3-5 V input voltage and closed in 0.96 ms, which verified the simulation.

  2. Bistable out-of-plane stress-mismatched thermally actuated bilayer devices with large deflection

    International Nuclear Information System (INIS)

    Goessling, B A; Lucas, T M; Moiseeva, E V; Aebersold, J W; Harnett, C K

    2011-01-01

    In this paper, we explore microfabricated bistable actuators released as thin films from a silicon wafer. The actuators are based on a serpentine design where two cantilevers are coupled at the tips by a thin-film bar. These devices are parameterized by two lengths: cantilever length and the length of the coupling bar. These two dimensions are systematically varied to study the effect of design parameters on bistability. The three-dimensional devices have extremely large deflection (hundreds of microns rather than tens of microns for most planar microactuators of similar size) and are thermally actuated out of the plane of the wafer by applying a bias across either the left or right side of the serpentine. The bistability of these devices is evaluated using electron and optical microscopy. Potential applications include non-volatile mechanical memory, optical shutters, and reconfigurable antenna elements

  3. Propensity for Bistability of Bursting and Silence in the Leech Heart Interneuron

    Directory of Open Access Journals (Sweden)

    Tatiana Dashevskiy

    2018-02-01

    Full Text Available 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. It exhibits bistability of bursting and silence in a narrow range of the leak current parameters, conductance (gleak and reversal potential (Eleak. We assessed the propensity for bistability of the model by using bifurcation diagrams. On the diagram (gleak, Eleak, we mapped bursting and silent regimes. For the canonical value of Eleak we determined the range of gleak which supported the bistability. We use this range as an index of propensity for bistability. We investigated how this index was affected by alterations of ionic currents. We systematically changed their conductances, one at a time, and built corresponding bifurcation diagrams in parameter planes of the maximal conductance of a given current and the leak conductance. We found that conductance of only one current substantially affected the index of propensity; the increase of the maximal conductance of the hyperpolarization-activated cationic current increased the propensity index. The second conductance with the strongest effect was the conductance of the low-threshold fast Ca2+ current; its reduction increased the propensity index although the effect was about two times smaller in magnitude. Analyzing the model with both changes applied simultaneously, we found that the diagram (gleak, Eleak showed a progressively expanded area of bistability of bursting and silence.

  4. Remnants of semiclassical bistability in the few-photon regime of cavity QED.

    Science.gov (United States)

    Kerckhoff, Joseph; Armen, Michael A; Mabuchi, Hideo

    2011-11-21

    Broadband homodyne detection of the light transmitted by a Fabry-Perot cavity containing a strongly-coupled (133)Cs atom is used to probe the dynamic optical response in a regime where semiclassical theory predicts bistability but strong quantum corrections should apply. While quantum fluctuations destabilize true equilibrium bistability, our observations confirm the existence of metastable states with finite lifetimes and a hysteretic response is apparent when the optical drive is modulated on comparable timescales. Our experiment elucidates remnant semiclassical behavior in the attojoule (~10 photon) regime of single-atom cavity QED, of potential significance for ultra-low power photonic signal processing. © 2011 Optical Society of America

  5. A silicon-nanowire memory driven by optical gradient force induced bistability

    Energy Technology Data Exchange (ETDEWEB)

    Dong, B. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), Singapore 117685 (Singapore); Cai, H., E-mail: caih@ime.a-star.edu.sg; Gu, Y. D.; Kwong, D. L. [Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), Singapore 117685 (Singapore); Chin, L. K.; Ng, G. I.; Ser, W. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Huang, J. G. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), Singapore 117685 (Singapore); School of Mechanical Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Yang, Z. C. [School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); Liu, A. Q., E-mail: eaqliu@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

    2015-12-28

    In this paper, a bistable optical-driven silicon-nanowire memory is demonstrated, which employs ring resonator to generate optical gradient force over a doubly clamped silicon-nanowire. Two stable deformation positions of a doubly clamped silicon-nanowire represent two memory states (“0” and “1”) and can be set/reset by modulating the light intensity (<3 mW) based on the optical force induced bistability. The time response of the optical-driven memory is less than 250 ns. It has applications in the fields of all optical communication, quantum computing, and optomechanical circuits.

  6. Stable Amplification and High Current Drop Bistable Switching in Supercritical GaAs Tills

    DEFF Research Database (Denmark)

    Izadpanah, S.H; Jeppsson, B; Jeppesen, Palle

    1974-01-01

    Bistable switching with current drops of 40% and switching times of 100 ps are obtained in pulsed operation of 10¿m supercritically doped n+ nn+ GaAs Transferred Electron Devices (TEDs). When CW-operated the same devices exhibit a 5-17 GHz bandwidth for the stable negative resistance.......Bistable switching with current drops of 40% and switching times of 100 ps are obtained in pulsed operation of 10¿m supercritically doped n+ nn+ GaAs Transferred Electron Devices (TEDs). When CW-operated the same devices exhibit a 5-17 GHz bandwidth for the stable negative resistance....

  7. Controlling steady-state and dynamical properties of atomic optical bistability

    CERN Document Server

    Joshi, Amitabh

    2012-01-01

    This book provides a comprehensive introduction to the theoretical and experimental studies of atomic optical bistability and multistability, and their dynamical properties in systems with two- and three-level inhomogeneously-broadened atoms inside an optical cavity. By making use of the modified linear absorption and dispersion, as well as the greatly enhanced nonlinearity in the three-level electromagnetically induced transparency system, the optical bistablity and efficient all-optical switching can be achieved at relatively low laser powers, which can be well controlled and manipulated. Un

  8. Bistability of self-modulation oscillations in an autonomous solid-state ring laser

    International Nuclear Information System (INIS)

    Dudetskii, V Yu

    2013-01-01

    Bistable self-modulation regimes of generation for a ring YAG : Nd chip laser with the counterpropagating waves asymmetrically coupled via backward scattering are simulated numerically. Two branches of bistable self-modulation regimes of generation are found in the domain of the parametric resonance between the selfmodulation and relaxation oscillations. The self-modulation regimes observed in earlier experiments pertain to only one of the branches. Possible reasons for such a discrepancy are considered, related to the influence of technical and natural noise on the dynamics of solid-state ring lasers. (control of laser radiation parameters)

  9. Toward Singlet-Triplet Bistable Nonalternant Kekulé Hydrocarbons: Azulene-to-Naphthalene Rearrangement.

    Science.gov (United States)

    Das, Soumyajit; Wu, Jishan

    2015-12-04

    Recent developments of open-shell singlet diradicaloids motivated the search for stable singlet-triplet bistable nonalternant polycyclic hydrocarbons. During the synthesis of this type of molecule, such as the dibenzo-cyclohepta[def]fluorene 3, an unexpected azulene-to-naphthalene rearrangement was observed at room temperature, which resulted in new nonalternant hydrocarbons 8a/8b with a closed-shell singlet ground state. These studies provided insight into the unique chemistry of azulene and challenges for the synthesis of singlet-triplet bistable polycyclic hydrocarbons.

  10. Chimeralike states in networks of bistable time-delayed feedback oscillators coupled via the mean field.

    Science.gov (United States)

    Ponomarenko, V I; Kulminskiy, D D; Prokhorov, M D

    2017-08-01

    We study the collective dynamics of oscillators in a network of identical bistable time-delayed feedback systems globally coupled via the mean field. The influence of delay and inertial properties of the mean field on the collective behavior of globally coupled oscillators is investigated. A variety of oscillation regimes in the network results from the presence of bistable states with substantially different frequencies in coupled oscillators. In the physical experiment and numerical simulation we demonstrate the existence of chimeralike states, in which some of the oscillators in the network exhibit synchronous oscillations, while all other oscillators remain asynchronous.

  11. Optically levitated nanoparticle as a model system for stochastic bistable dynamics.

    Science.gov (United States)

    Ricci, F; Rica, R A; Spasenović, M; Gieseler, J; Rondin, L; Novotny, L; Quidant, R

    2017-05-09

    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. This work contributes to showing the use of levitated nanoparticles as a model system for stochastic bistable dynamics, with applications to a wide variety of fields.

  12. Study on non-linear bistable dynamics model based EEG signal discrimination analysis method.

    Science.gov (United States)

    Ying, Xiaoguo; Lin, Han; Hui, Guohua

    2015-01-01

    Electroencephalogram (EEG) is the recording of electrical activity along the scalp. EEG measures voltage fluctuations generating from ionic current flows within the neurons of the brain. EEG signal is looked as one of the most important factors that will be focused in the next 20 years. In this paper, EEG signal discrimination based on non-linear bistable dynamical model was proposed. EEG signals were processed by non-linear bistable dynamical model, and features of EEG signals were characterized by coherence index. Experimental results showed that the proposed method could properly extract the features of different EEG signals.

  13. Thiol-modified MoS2 nanosheets as a functional layer for electrical bistable devices

    Science.gov (United States)

    Li, Guan; Tan, Fenxue; Lv, Bokun; Wu, Mengying; Wang, Ruiqi; Lu, Yue; Li, Xu; Li, Zhiqiang; Teng, Feng

    2018-01-01

    Molybdenum disulfide nanosheets have been synthesized by one-pot method using 1-ODT as sulfur source and surfactant. The structure, morphology and optical properties of samples were investigated by XRD, FTIR, Abs spectrum and TEM patterns. The XRD pattern indicated that the as-obtained MoS2 belong to hexagonal system. The as-obtained MoS2 nanosheets blending with PVK could be used to fabricate an electrically bistable devices through a simple spin-coating method and the device exhibited an obvious electrical bistability properties. The charge transport mechanism of the device was discussed based on the filamentary switching models.

  14. Bistable dynamics underlying excitability of ion homeostasis in neuron models.

    Directory of Open Access Journals (Sweden)

    Niklas Hübel

    2014-05-01

    Full Text Available When neurons fire action potentials, dissipation of free energy is usually not directly considered, because the change in free energy is often negligible compared to the immense reservoir stored in neural transmembrane ion gradients and the long-term energy requirements are met through chemical energy, i.e., metabolism. However, these gradients can temporarily nearly vanish in neurological diseases, such as migraine and stroke, and in traumatic brain injury from concussions to severe injuries. We study biophysical neuron models based on the Hodgkin-Huxley (HH formalism extended to include time-dependent ion concentrations inside and outside the cell and metabolic energy-driven pumps. We reveal the basic mechanism of a state of free energy-starvation (FES with bifurcation analyses showing that ion dynamics is for a large range of pump rates bistable without contact to an ion bath. This is interpreted as a threshold reduction of a new fundamental mechanism of ionic excitability that causes a long-lasting but transient FES as observed in pathological states. We can in particular conclude that a coupling of extracellular ion concentrations to a large glial-vascular bath can take a role as an inhibitory mechanism crucial in ion homeostasis, while the Na⁺/K⁺ pumps alone are insufficient to recover from FES. Our results provide the missing link between the HH formalism and activator-inhibitor models that have been successfully used for modeling migraine phenotypes, and therefore will allow us to validate the hypothesis that migraine symptoms are explained by disturbed function in ion channel subunits, Na⁺/K⁺ pumps, and other proteins that regulate ion homeostasis.

  15. A Strategy for Magnifying Vibration in High-Energy Orbits of a Bistable Oscillator at Low Excitation Levels

    International Nuclear Information System (INIS)

    Wang Guang-Qing; Liao Wei-Hsin

    2015-01-01

    This work focuses on how to maintain a high-energy orbit motion of a bistable oscillator when subjected to a low level excitation. An elastic magnifier (EM) positioned between the base and the bistable oscillator is used to magnify the base vibration displacement to significantly enhance the output characteristics of the bistable oscillator. The dimensionless electromechanical equations of the bistable oscillator with an EM are derived, and the effects of the mass and stiffness ratios between the EM and the bistable oscillator on the output displacement are studied. It is shown that the jump phenomenon occurs at a lower excitation level with increasing the mass and stiffness ratios. With the comparison of the displacement trajectories and the phase portraits obtained from experiments, it is validated that the bistable oscillator with an EM can effectively oscillate in a high-energy orbit and can generate a superior output vibration at a low excitation level as compared with the bistable oscillator without an EM. (paper)

  16. Reverse bistable effect in ferroelectric liquid crystal devices with ultra-fast switching at low driving voltage.

    Science.gov (United States)

    Guo, Qi; Zhao, Xiaojin; Zhao, Huijie; Chigrinov, V G

    2015-05-15

    In this Letter, reverse bistable effect with deep-sub-millisecond switching time is first reported in ferroelectric liquid crystal (FLC) devices using a homogeneous photo-alignment technique. It is indicated by our experimental results that both the anchoring energy and the dielectric property of the FLC's alignment layer is critical for the existence of the reverse bistable effect. In addition, with the derived criteria of the reverse bistable effect, we quantitatively analyze the switching dynamics of the reverse bistable FLC and the transition condition between the traditional bistability and our presented reverse bistability. Moreover, the fabricated FLC device exhibits an ultra-fast switching of ∼160  μs and a high contrast ratio of 1000:1, both of which were measured at a low driving voltage of 11 V. The featured deep-sub-millisecond switching time is really advantageous for our presented reverse bistable FLC devices, which enables a significant quality improvement of the existing optical devices, as well as a wide range of new applications in photonics and display areas.

  17. Neural Decoding of Bistable Sounds Reveals an Effect of Intention on Perceptual Organization.

    Science.gov (United States)

    Billig, Alexander J; Davis, Matthew H; Carlyon, Robert P

    2018-03-14

    Auditory signals arrive at the ear as a mixture that the brain must decompose into distinct sources based to a large extent on acoustic properties of the sounds. An important question concerns whether listeners have voluntary control over how many sources they perceive. This has been studied using pure high (H) and low (L) tones presented in the repeating pattern HLH-HLH-, which can form a bistable percept heard either as an integrated whole (HLH-) or as segregated into high (H-H-) and low (-L-) sequences. Although instructing listeners to try to integrate or segregate sounds affects reports of what they hear, this could reflect a response bias rather than a perceptual effect. We had human listeners (15 males, 12 females) continuously report their perception of such sequences and recorded neural activity using MEG. During neutral listening, a classifier trained on patterns of neural activity distinguished between periods of integrated and segregated perception. In other conditions, participants tried to influence their perception by allocating attention either to the whole sequence or to a subset of the sounds. They reported hearing the desired percept for a greater proportion of time than when listening neutrally. Critically, neural activity supported these reports; stimulus-locked brain responses in auditory cortex were more likely to resemble the signature of segregation when participants tried to hear segregation than when attempting to perceive integration. These results indicate that listeners can influence how many sound sources they perceive, as reflected in neural responses that track both the input and its perceptual organization. SIGNIFICANCE STATEMENT Can we consciously influence our perception of the external world? We address this question using sound sequences that can be heard either as coming from a single source or as two distinct auditory streams. Listeners reported spontaneous changes in their perception between these two interpretations while

  18. First-passage time in a bistable potential with colored noise

    International Nuclear Information System (INIS)

    Ramirez-Piscina, L.; Maria Sancho, J.; Javier de la Rubia, F.; Lindenberg, K.; Tsironis, G.P.

    1989-01-01

    A precise digital simulation of a bistable system under the effect of colored noise is carried out. A set of data for the mean first-passage time is obtained. The results are interpreted and compared with presently available theories, which are revisited following a new insight. Discrepancies that have been discussed in the literature are understood within our framework

  19. Temperature persistent bistability and threshold switching in a single barrier heterostructure hot-electron diode

    DEFF Research Database (Denmark)

    Stasch, R.; Hey, R.; Asche, M.

    1996-01-01

    Bistable current–voltage characteristics caused by competition of tunneling through and field-enhanced thermionic emission across a single barrier are investigated in an n–-GaAs/Al0.34Ga0.66As/n+-GaAs structure. The S-shaped part of the characteristic persists in the whole temperature regime...

  20. Interplay of Multisensory Processing, Attention, and Consciousness as Revealed by Bistable Figures

    Directory of Open Access Journals (Sweden)

    Su-Ling Yeh

    2011-10-01

    Full Text Available We examined the novel crossmodal semantic congruency effect on bistable figures in which a static stimulus gives rise to two competing percepts that alternate over time. Participants viewed the bistable figure “my wife or my mother-in-law” while listening to the voice of an old woman or a young lady speaking in an unfamiliar language. They had to report whether they saw the old woman, the young lady, or a mixed percept. Robust crossmodal semantic congruency effects in the measures of the first percept and the predominance duration were observed. The possibilities that the participants simply responded to, and/or that they fixed at the location in favor of, the percept congruent with the sound that they happened to hear were ruled out. When the participants were instructed to maintain their attention to a specific view, a strong top-down modulation on the perception of bistable figure was observed, although the audiovisual semantic congruency effect still remained. These results thus demonstrate that top-down attention (ie,, selection and/or voluntary control modulates the audiovisual semantic congruency effect. As the alternating percepts in bistable figures indicate competition for conscious perception, this study has important implications for the multifaceted interactions between multisensory processing, attention, and consciousness.

  1. Bistability breaks-off deterministic responses to intracortical stimulation during non-REM sleep

    Directory of Open Access Journals (Sweden)

    Andrea Pigorini

    2015-04-01

    These results point to bistability as the underlying critical mechanism that prevents the emergence of complex interactions in human thalamocortical networks during NREM sleep. Besides sleep, the same basic neurophysiological dynamics may play a role in pathological conditions(Casali et al., 2013; Rosanova et al., 2012 where cortico-cortical communication and consciousness are impaired in spite of preserved neuronal activity.

  2. Non-symmetric bi-stable flow around the Ahmed body

    International Nuclear Information System (INIS)

    Meile, W.; Ladinek, T.; Brenn, G.; Reppenhagen, A.; Fuchs, A.

    2016-01-01

    Highlights: • The non-symmetric bi-stable flow around the Ahmed body is investigated experimentally. • Bi-stability, described for symmetric flow by Cadot and co-workers, was found in nonsymmetric flow also. • The flow field randomly switches between two states. • The flow is subject to a spanwise instability identified by Cadot and co-workers for symmetric flow. • Aerodynamic forces fluctuate strongly due to the bi-stability. - Abstract: The flow around the Ahmed body at varying Reynolds numbers under yawing conditions is investigated experimentally. The body geometry belongs to a regime subject to spanwise flow instability identified in symmetric flow by Cadot and co-workers (Grandemange et al., 2013b). Our experiments cover the two slant angles 25° and 35° and Reynolds numbers up to 2.784 × 10"6. Special emphasis lies on the aerodynamics under side wind influence. For the 35° slant angle, forces and moments change significantly with the yawing angle in the range 10° ≤ |β| ≤ 15°. The lift and the pitching moment exhibit strong fluctuations due to bi-stable flow around a critical angle β of ±12.5°, where the pitching moment changes sign. Time series of the forces and moments are studied and explained by PIV measurements in the flow field near the rear of the body.

  3. Parallel replica dynamics method for bistable stochastic reaction networks: Simulation and sensitivity analysis

    Science.gov (United States)

    Wang, Ting; Plecháč, Petr

    2017-12-01

    Stochastic reaction networks that exhibit bistable behavior are common in systems biology, materials science, and catalysis. Sampling of stationary distributions is crucial for understanding and characterizing the long-time dynamics of bistable stochastic dynamical systems. However, simulations are often hindered by the insufficient sampling of rare transitions between the two metastable regions. In this paper, we apply the parallel replica method for a continuous time Markov chain in order to improve sampling of the stationary distribution in bistable stochastic reaction networks. The proposed method uses parallel computing to accelerate the sampling of rare transitions. Furthermore, it can be combined with the path-space information bounds for parametric sensitivity analysis. With the proposed methodology, we study three bistable biological networks: the Schlögl model, the genetic switch network, and the enzymatic futile cycle network. We demonstrate the algorithmic speedup achieved in these numerical benchmarks. More significant acceleration is expected when multi-core or graphics processing unit computer architectures and programming tools such as CUDA are employed.

  4. Brain activity dynamics in human parietal regions during spontaneous switches in bistable perception.

    Science.gov (United States)

    Megumi, Fukuda; Bahrami, Bahador; Kanai, Ryota; Rees, Geraint

    2015-02-15

    The neural mechanisms underlying conscious visual perception have been extensively investigated using bistable perception paradigms. Previous functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) studies suggest that the right anterior superior parietal (r-aSPL) and the right posterior superior parietal lobule (r-pSPL) have opposite roles in triggering perceptual reversals. It has been proposed that these two areas are part of a hierarchical network whose dynamics determine perceptual switches. However, how these two parietal regions interact with each other and with the rest of the brain during bistable perception is not known. Here, we investigated such a model by recording brain activity using fMRI while participants viewed a bistable structure-from-motion stimulus. Using dynamic causal modeling (DCM), we found that resolving such perceptual ambiguity was specifically associated with reciprocal interactions between these parietal regions and V5/MT. Strikingly, the strength of bottom-up coupling between V5/MT to r-pSPL and from r-pSPL to r-aSPL predicted individual mean dominance duration. Our findings are consistent with a hierarchical predictive coding model of parietal involvement in bistable perception and suggest that visual information processing underlying spontaneous perceptual switches can be described as changes in connectivity strength between parietal and visual cortical regions. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  5. Switching between bistable states in a discrete nonlinear model with long-range dispersion

    DEFF Research Database (Denmark)

    Johansson, Magnus; Gaididei, Yuri B.; Christiansen, Peter Leth

    1998-01-01

    In the framework of a discrete nonlinear Schrodinger equation with long-range dispersion, we propose a general mechanism for obtaining a controlled switching between bistable localized excitations. We show that the application of a spatially symmetric kick leads to the excitation of an internal...

  6. Spatial waves of advance with bistable dynamics: cytoplasmic and genetic analogues of Allee effects.

    Science.gov (United States)

    Barton, N H; Turelli, Michael

    2011-09-01

    Unlike unconditionally advantageous "Fisherian" variants that tend to spread throughout a species range once introduced anywhere, "bistable" variants, such as chromosome translocations, have two alternative stable frequencies, absence and (near) fixation. Analogous to populations with Allee effects, bistable variants tend to increase locally only once they become sufficiently common, and their spread depends on their rate of increase averaged over all frequencies. Several proposed manipulations of insect populations, such as using Wolbachia or "engineered underdominance" to suppress vector-borne diseases, produce bistable rather than Fisherian dynamics. We synthesize and extend theoretical analyses concerning three features of their spatial behavior: rate of spread, conditions to initiate spread from a localized introduction, and wave stopping caused by variation in population densities or dispersal rates. Unlike Fisherian variants, bistable variants tend to spread spatially only for particular parameter combinations and initial conditions. Wave initiation requires introduction over an extended region, while subsequent spatial spread is slower than for Fisherian waves and can easily be halted by local spatial inhomogeneities. We present several new results, including robust sufficient conditions to initiate (and stop) spread, using a one-parameter cubic approximation applicable to several models. The results have both basic and applied implications.

  7. Controlling the optical bistability and transmission coefficient in a four-level atomic medium

    International Nuclear Information System (INIS)

    Asadpour, Seyyed Hossein; Eslami-Majd, Abdullah

    2012-01-01

    A novel four level atomic configuration is proposed for controlling the optical bistability and transmission coefficient with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field has derived another atomic transition. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by magnitude of the external magnetic field. Also, it is shown that optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams. - Highlights: ► An inverted Y-type four level atomic system is proposed. ► Transmission coefficient can be controlled by a novel interesting parameter. ► Optical bistability and multistability can be achieved via external magnetic field. ► It is shown that our proposed model is suitable for all optical switching application.

  8. Combined fMRI- and eye movement-based decoding of bistable plaid motion perception.

    Science.gov (United States)

    Wilbertz, Gregor; Ketkar, Madhura; Guggenmos, Matthias; Sterzer, Philipp

    2018-05-01

    The phenomenon of bistable perception, in which perception alternates spontaneously despite constant sensory stimulation, has been particularly useful in probing the neural bases of conscious perception. The study of such bistability requires access to the observer's perceptual dynamics, which is usually achieved via active report. This report, however, constitutes a confounding factor in the study of conscious perception and can also be biased in the context of certain experimental manipulations. One approach to circumvent these problems is to track perceptual alternations using signals from the eyes or the brain instead of observers' reports. Here we aimed to optimize such decoding of perceptual alternations by combining eye and brain signals. Eye-tracking and functional magnetic resonance imaging (fMRI) was performed in twenty participants while they viewed a bistable visual plaid motion stimulus and reported perceptual alternations. Multivoxel pattern analysis (MVPA) for fMRI was combined with eye-tracking in a Support vector machine to decode participants' perceptual time courses from fMRI and eye-movement signals. While both measures individually already yielded high decoding accuracies (on average 86% and 88% correct, respectively) classification based on the two measures together further improved the accuracy (91% correct). These findings show that leveraging on both fMRI and eye movement data may pave the way for optimized no-report paradigms through improved decodability of bistable motion perception and hence for a better understanding of the neural correlates of consciousness. Copyright © 2018 Elsevier Inc. All rights reserved.

  9. The role of frontal and parietal brain areas in bistable perception

    NARCIS (Netherlands)

    Knapen, T.; Brascamp, J.; Pearson, J.; van Ee, R.; Blake, R.

    2011-01-01

    When sensory input allows for multiple, competing perceptual interpretations, observers' perception can fluctuate over time, which is called bistable perception. Imaging studies in humans have revealed transient responses in a right-lateralized network in the frontal-parietal cortex (rFPC) around

  10. Parallel replica dynamics method for bistable stochastic reaction networks: Simulation and sensitivity analysis.

    Science.gov (United States)

    Wang, Ting; Plecháč, Petr

    2017-12-21

    Stochastic reaction networks that exhibit bistable behavior are common in systems biology, materials science, and catalysis. Sampling of stationary distributions is crucial for understanding and characterizing the long-time dynamics of bistable stochastic dynamical systems. However, simulations are often hindered by the insufficient sampling of rare transitions between the two metastable regions. In this paper, we apply the parallel replica method for a continuous time Markov chain in order to improve sampling of the stationary distribution in bistable stochastic reaction networks. The proposed method uses parallel computing to accelerate the sampling of rare transitions. Furthermore, it can be combined with the path-space information bounds for parametric sensitivity analysis. With the proposed methodology, we study three bistable biological networks: the Schlögl model, the genetic switch network, and the enzymatic futile cycle network. We demonstrate the algorithmic speedup achieved in these numerical benchmarks. More significant acceleration is expected when multi-core or graphics processing unit computer architectures and programming tools such as CUDA are employed.

  11. Early Top-Down Influences on Bistable Perception Revealed by Event-Related Potentials

    Science.gov (United States)

    Pitts, Michael A.; Gavin, William J.; Nerger, Janice L.

    2008-01-01

    A longstanding debate exists in the literature concerning bottom-up vs. top-down influences on bistable perception. Recently, a technique has been developed to measure early changes in brain activity (via ERPs) related to perceptual reversals (Kornmeier & Bach, 2004). An ERP component, the reversal negativity (RN) has been identified, and is…

  12. Controllable optical bistability in photonic-crystal one-atom laser

    International Nuclear Information System (INIS)

    Guo Xiaoyong; Lue Shuchen

    2009-01-01

    We investigate the property of optical bistability in a photonic-crystal one-atom laser when nonlinear microcavity is present. The physical system consists of a coherently driven two-level light emitter strongly coupled to a high-quality microcavity which is embedded within a photonic crystal and another coherent probing field which has incident into the microcavity. In our case, the microcavity is fabricated by nonlinear material and placed as an impurity in photonic crystal. This study reveals that such a system can exhibit optical bistability. The dependence of threshold value and hysteresis loop on the photonic band gap of the photonic crystal, driving field Rabi frequency and dephasing processes, are studied. Our results clearly illustrate the ability to control optical bistability through suitable photonic-crystal architectures and external coherent driving field, and this study suggests that in a photonic-crystal nonlinear microcavity, the one-atom laser acts as an effective controllable bistable device in the design of all-light digital computing systems in the near future.

  13. An analytical approach to bistable biological circuit discrimination using real algebraic geometry.

    Science.gov (United States)

    Siegal-Gaskins, Dan; Franco, Elisa; Zhou, Tiffany; Murray, Richard M

    2015-07-06

    Biomolecular circuits with two distinct and stable steady states have been identified as essential components in a wide range of biological networks, with a variety of mechanisms and topologies giving rise to their important bistable property. Understanding the differences between circuit implementations is an important question, particularly for the synthetic biologist faced with determining which bistable circuit design out of many is best for their specific application. In this work we explore the applicability of Sturm's theorem--a tool from nineteenth-century real algebraic geometry--to comparing 'functionally equivalent' bistable circuits without the need for numerical simulation. We first consider two genetic toggle variants and two different positive feedback circuits, and show how specific topological properties present in each type of circuit can serve to increase the size of the regions of parameter space in which they function as switches. We then demonstrate that a single competitive monomeric activator added to a purely monomeric (and otherwise monostable) mutual repressor circuit is sufficient for bistability. Finally, we compare our approach with the Routh-Hurwitz method and derive consistent, yet more powerful, parametric conditions. The predictive power and ease of use of Sturm's theorem demonstrated in this work suggest that algebraic geometric techniques may be underused in biomolecular circuit analysis.

  14. Different cell fates from cell-cell interactions: core architectures of two-cell bistable networks.

    Science.gov (United States)

    Rouault, Hervé; Hakim, Vincent

    2012-02-08

    The acquisition of different fates by cells that are initially in the same state is central to development. Here, we investigate the possible structures of bistable genetic networks that can allow two identical cells to acquire different fates through cell-cell interactions. Cell-autonomous bistable networks have been previously sampled using an evolutionary algorithm. We extend this evolutionary procedure to take into account interactions between cells. We obtain a variety of simple bistable networks that we classify into major subtypes. Some have long been proposed in the context of lateral inhibition through the Notch-Delta pathway, some have been more recently considered and others appear to be new and based on mechanisms not previously considered. The results highlight the role of posttranscriptional interactions and particularly of protein complexation and sequestration, which can replace cooperativity in transcriptional interactions. Some bistable networks are entirely based on posttranscriptional interactions and the simplest of these is found to lead, upon a single parameter change, to oscillations in the two cells with opposite phases. We provide qualitative explanations as well as mathematical analyses of the dynamical behaviors of various created networks. The results should help to identify and understand genetic structures implicated in cell-cell interactions and differentiation. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  15. Models of charge transport and transfer in molecular switch tunnel junctions of bistable catenanes and rotaxanes

    International Nuclear Information System (INIS)

    Flood, Amar H.; Wong, Eric W.; Stoddart, J. Fraser

    2006-01-01

    The processes by which charge transfer can occur play a foundational role in molecular electronics. Here we consider simplified models of the transfer processes that could be present in bistable molecular switch tunnel junction (MSTJ) devices during one complete cycle of the device from its low- to high- and back to low-conductance state. The bistable molecular switches, which are composed of a monolayer of either switchable catenanes or rotaxanes, exist in either a ground-state co-conformation or a metastable one in which the conduction properties of the two co-conformations, when measured at small biases (+0.1 V), are significantly different irrespective of whether transport is dominated by tunneling or hopping. The voltage-driven generation (±2 V) of molecule-based redox states, which are sufficiently long-lived to allow the relative mechanical movements necessary to switch between the two co-conformations, rely upon unequal charge transfer rates on to and/or off of the molecules. Surface-enhanced Raman spectroscopy has been used to image the ground state of the bistable rotaxane in MSTJ-like devices. Consideration of these models provide new ways of looking at molecular electronic devices that rely, not only on nanoscale charge-transport, but also upon the bustling world of molecular motion in mechanically interlocked bistable molecules

  16. Implications of the spatial dynamics of fire spread for the bistability of savanna and forest.

    Science.gov (United States)

    Schertzer, E; Staver, A C; Levin, S A

    2015-01-01

    The role of fire in expanding the global distribution of savanna is well recognized. Empirical observations and modeling suggest that fire spread has a threshold response to fuel-layer continuity, which sets up a positive feedback that maintains savanna-forest bistability. However, modeling has so far failed to examine fire spread as a spatial process that interacts with vegetation. Here, we use simple, well-supported assumptions about fire spread as an infection process and its effects on trees to ask whether spatial dynamics qualitatively change the potential for savanna-forest bistability. We show that the spatial effects of fire spread are the fundamental reason that bistability is possible: because fire spread is an infection process, it exhibits a threshold response to fuel continuity followed by a rapid increase in fire size. Other ecological processes affecting fire spread may also contribute including temporal variability in demography or fire spread. Finally, including the potential for spatial aggregation increases the potential both for savanna-forest bistability and for savanna and forest to coexist in a landscape mosaic.

  17. Bi-stability in accelerator driven 233U breeders

    International Nuclear Information System (INIS)

    Ghosh, Biplab; Degweker, S.B.

    2011-01-01

    -linear, several interesting phenomena can be observed. Under certain circumstances, the equilibrium discharge fluence, power, rate of breeding, 233 U fraction are triple valued functions of the irradiation time. For the solution corresponding to the middle value, the fluence decreases with increasing irradiation time and the equilibrium appears to be unstable. For the two solutions with values below and above middle value, the fluence increases with increasing irradiation time and the equilibrium appears to be stable. This looks like a typical bi-stable system. A simple model based on nonlinear differential equations for the breeding process is studied to obtain a better understanding of this phenomenon. (author)

  18. Design and experiment of controlled bistable vortex induced vibration energy harvesting systems operating in chaotic regions

    Science.gov (United States)

    Huynh, B. H.; Tjahjowidodo, T.; Zhong, Z.-W.; Wang, Y.; Srikanth, N.

    2018-01-01

    Vortex induced vibration based energy harvesting systems have gained interests in these recent years due to its potential as a low water current energy source. However, the effectiveness of the system is limited only at a certain water current due to the resonance principle that governs the concept. In order to extend the working range, a bistable spring to support the structure is introduced on the system. The improvement on the performance is essentially dependent on the bistable gap as one of the main parameters of the nonlinear spring. A sufficiently large bistable gap will result in a significant performance improvement. Unfortunately, a large bistable gap might also increase a chance of chaotic responses, which in turn will result in diminutive harvested power. To mitigate the problem, an appropriate control structure is required to stabilize the chaotic vibrations of a VIV energy converter with the bistable supporting structure. Based on the nature of the double-well potential energy in a bistable spring, the ideal control structure will attempt to drive the responses to inter-well periodic vibrations in order to maximize the harvested power. In this paper, the OGY control algorithm is designed and implemented to the system. The control strategy is selected since it requires only a small perturbation in a structural parameter to execute the control effort, thus, minimum power is needed to drive the control input. Facilitated by a wake oscillator model, the bistable VIV system is modelled as a 4-dimensional autonomous continuous-time dynamical system. To implement the controller strategy, the system is discretized at a period estimated from the subspace hyperplane intersecting to the chaotic trajectory, whereas the fixed points that correspond to the desired periodic orbits are estimated by the recurrence method. Simultaneously, the Jacobian and sensitivity matrices are estimated by the least square regression method. Based on the defined fixed point and the

  19. Ground-state kinetics of bistable redox-active donor-acceptor mechanically interlocked molecules.

    Science.gov (United States)

    Fahrenbach, Albert C; Bruns, Carson J; Li, Hao; Trabolsi, Ali; Coskun, Ali; Stoddart, J Fraser

    2014-02-18

    The ability to design and confer control over the kinetics of theprocesses involved in the mechanisms of artificial molecular machines is at the heart of the challenge to create ones that can carry out useful work on their environment, just as Nature is wont to do. As one of the more promising forerunners of prototypical artificial molecular machines, chemists have developed bistable redox-active donor-acceptor mechanically interlocked molecules (MIMs) over the past couple of decades. These bistable MIMs generally come in the form of [2]rotaxanes, molecular compounds that constitute a ring mechanically interlocked around a dumbbell-shaped component, or [2]catenanes, which are composed of two mechanically interlocked rings. As a result of their interlocked nature, bistable MIMs possess the inherent propensity to express controllable intramolecular, large-amplitude, and reversible motions in response to redox stimuli. In this Account, we rationalize the kinetic behavior in the ground state for a large assortment of these types of bistable MIMs, including both rotaxanes and catenanes. These structures have proven useful in a variety of applications ranging from drug delivery to molecular electronic devices. These bistable donor-acceptor MIMs can switch between two different isomeric states. The favored isomer, known as the ground-state co-conformation (GSCC) is in equilibrium with the less favored metastable state co-conformation (MSCC). The forward (kf) and backward (kb) rate constants associated with this ground-state equilibrium are intimately connected to each other through the ground-state distribution constant, KGS. Knowing the rate constants that govern the kinetics and bring about the equilibration between the MSCC and GSCC, allows researchers to understand the operation of these bistable MIMs in a device setting and apply them toward the construction of artificial molecular machines. The three biggest influences on the ground-state rate constants arise from

  20. Control of optical bistability and third-order nonlinearity via tunneling induced quantum interference in triangular quantum dot molecules

    International Nuclear Information System (INIS)

    Tian, Si-Cong; Tong, Cun-Zhu; Zhang, Jin-Long; Shan, Xiao-Nan; Fu, Xi-Hong; Zeng, Yu-Gang; Qin, Li; Ning, Yong-Qiang; Wan, Ren-Gang

    2015-01-01

    The optical bistability of a triangular quantum dot molecules embedded inside a unidirectional ring cavity is studied. The type, the threshold and the hysteresis loop of the optical bistability curves can be modified by the tunneling parameters, as well as the probe laser field. The linear and nonlinear susceptibilities of the medium are also studied to interpret the corresponding results. The physical interpretation is that the tunneling can induce the quantum interference, which modifies the linear and the nonlinear response of the medium. As a consequence, the characteristics of the optical bistability are changed. The scheme proposed here can be utilized for optimizing and controlling the optical switching process

  1. The transformation of optical bistability effect and of generated pulses in operation of a DFB laser with two sections

    International Nuclear Information System (INIS)

    Nguyen Van Phu; Dinh Van Hoang

    2005-01-01

    In this paper is presented the transformation of characteristics of optical bistability effect and of generated pulses in operation of a DFB laser with two sections. By solving the rate equations describing the operation of this laser the appearance of optical bistability effect in stationary regime and of short pulses in transient regime is obtained. With the variation of dynamical laser parameter we can evaluate the transformation indicated above. The method of examination used here is simple for determining the influence of any dynamical laser parameter on characteristics of optical bistability effect and generated pulses. (author)

  2. Optical bistability and multistability in a three-level Δ-type atomic system under the nonresonant condition

    International Nuclear Information System (INIS)

    Ai-Xi, Chen; Zhi-Ping, Wang; De-Hai, Chen; Yan-Qiu, Xu

    2009-01-01

    Under a nonresonant condition, we theoretically investigate hybrid absorptive-dispersive optical bistability and multistability behaviours in a three-level Δ-type system by using a microwave field to drive a hyperfine transition between two upper excited states inside a unidirectional ring cavity. We find that the optical bistability and multistability behaviours can be controlled by adjusting the intensity of the microwave field or the intensity of the coherent coupling field. Furthermore, our studies show an interesting phenomenon of the transition from the optical bistability to the optical multistability only by changing the negative detuning of the coupling field into the positive detuning of the coupling field. (classical areas of phenomenology)

  3. Evolution of the bi-stable wake of a square-back automotive shape

    Science.gov (United States)

    Pavia, Giancarlo; Passmore, Martin; Sardu, Costantino

    2018-01-01

    Square-back shapes are popular in the automotive market for their high level of practicality. These geometries, however, are usually characterised by high drag and their wake dynamics present aspects, such as the coexistence of a long-time bi-stable behaviour and short-time global fluctuating modes that are not fully understood. In the present paper, the unsteady behaviour of the wake of a generic square-back car geometry is characterised with an emphasis on identifying the causal relationship between the different dynamic modes in the wake. The study is experimental, consisting of balance, pressure, and stereoscopic PIV measurements. Applying wavelet and cross-wavelet transforms to the balance data, a quasi-steady correlation is demonstrated between the forces and bi-stable modes. This is investigated by applying proper orthogonal decomposition to the pressure and velocity data sets and a new structure is proposed for each bi-stable state, consisting of a hairpin vortex that originates from one of the two model's vertical trailing edges and bends towards the opposite side as it merges into a single streamwise vortex downstream. The wake pumping motion is also identified and for the first time linked with the motion of the bi-stable vortical structure in the streamwise direction, resulting in out-of-phase pressure variations between the two vertical halves of the model base. A phase-averaged low-order model is also proposed that provides a comprehensive description of the mechanisms of the switch between the bi-stable states. It is demonstrated that, during the switch, the wake becomes laterally symmetric and, at this point, the level of interaction between the recirculating structures and the base reaches a minimum, yielding, for this geometry, a 7% reduction of the base drag compared to the time-averaged result.

  4. Bistability in a self-assembling system confined by elastic walls: Exact results in a one-dimensional lattice model

    Energy Technology Data Exchange (ETDEWEB)

    Pȩkalski, J.; Ciach, A. [Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warszawa (Poland); Almarza, N. G. [Instituto de Química Física Rocasolano, CSIC, Serrano 119, E-28006 Madrid (Spain)

    2015-01-07

    The impact of confinement on self-assembly of particles interacting with short-range attraction and long-range repulsion potential is studied for thermodynamic states corresponding to local ordering of clusters or layers in the bulk. Exact and asymptotic expressions for the local density and for the effective potential between the confining surfaces are obtained for a one-dimensional lattice model introduced by J. Pȩkalski et al. [J. Chem. Phys. 138, 144903 (2013)]. The simple asymptotic formulas are shown to be in good quantitative agreement with exact results for slits containing at least 5 layers. We observe that the incommensurability of the system size and the average distance between the clusters or layers in the bulk leads to structural deformations that are different for different values of the chemical potential μ. The change of the type of defects is reflected in the dependence of density on μ that has a shape characteristic for phase transitions. Our results may help to avoid misinterpretation of the change of the type of defects as a phase transition in simulations of inhomogeneous systems. Finally, we show that a system confined by soft elastic walls may exhibit bistability such that two system sizes that differ approximately by the average distance between the clusters or layers are almost equally probable. This may happen when the equilibrium separation between the soft boundaries of an empty slit corresponds to the largest stress in the confined self-assembling system.

  5. Design of all-optical flip-flop by using optical bistability in passive micro-rings

    International Nuclear Information System (INIS)

    Karimi, M.; Abolfazli, M. J.; Rouholamini Nejad, H.; Bahrampour, A.

    2007-01-01

    In this paper at first, Optical bistability in the micro ring resonators in the presence of Kerr and two-photon absorption effects is studied and also, attenuation in micro rings with these nonlinear effects is calculated. An all-optical R-S flip-flop is designed by using optical bistability. Conditions for SET and RESET signals are calculated and their dependences on the optical parameters of micro rings are investigated.

  6. Intrinsic Bistability and Critical Slowing in Tm3+/Yb3+ Codoped Laser Crystal with the Photon Avalanche Mechanism

    International Nuclear Information System (INIS)

    Li, Li; Li-Xue, Chen; Xin-Lu, Zhang

    2009-01-01

    We present theoretically a novel intrinsic optical bistability (IOB) in the Tm 3+ /Yb 3+ codoped system with a photon avalanche mechanism. Numerical simulations based on the rate equation model demonstrate distinct IOB hysteresis and critical slowing dynamics around the avalanche thresholds. Such an IOB characteristic in Tm 3+ /Yb 3+ codoped crystal has potential applications in solid-state bistable optical displays and luminescence switchers in visible-infrared spectra. (fundamental areas of phenomenology (including applications))

  7. Ground-state thermodynamics of bistable redox-active donor-acceptor mechanically interlocked molecules.

    Science.gov (United States)

    Fahrenbach, Albert C; Bruns, Carson J; Cao, Dennis; Stoddart, J Fraser

    2012-09-18

    Fashioned through billions of years of evolution, biological molecular machines, such as ATP synthase, myosin, and kinesin, use the intricate relative motions of their components to drive some of life's most essential processes. Having control over the motions in molecules is imperative for life to function, and many chemists have designed, synthesized, and investigated artificial molecular systems that also express controllable motions within molecules. Using bistable mechanically interlocked molecules (MIMs), based on donor-acceptor recognition motifs, we have sought to imitate the sophisticated nanoscale machines present in living systems. In this Account, we analyze the thermodynamic characteristics of a series of redox-switchable [2]rotaxanes and [2]catenanes. Control and understanding of the relative intramolecular movements of components in MIMs have been vital in the development of a variety of applications of these compounds ranging from molecular electronic devices to drug delivery systems. These bistable donor-acceptor MIMs undergo redox-activated switching between two isomeric states. Under ambient conditions, the dominant translational isomer, the ground-state coconformation (GSCC), is in equilibrium with the less favored translational isomer, the metastable-state coconformation (MSCC). By manipulating the redox state of the recognition site associated with the GSCC, we can stimulate the relative movements of the components in these bistable MIMs. The thermodynamic parameters of model host-guest complexes provide a good starting point to rationalize the ratio of GSCC to MSCC at equilibrium. The bistable [2]rotaxanes show a strong correlation between the relative free energies of model complexes and the ground-state distribution constants (K(GS)). This relationship does not always hold for bistable [2]catenanes, most likely because of the additional steric and electronic constraints present when the two rings are mechanically interlocked with each other

  8. The interplay of multiple feedback loops with post-translational kinetics results in bistability of mycobacterial stress response

    International Nuclear Information System (INIS)

    Tiwari, Abhinav; Igoshin, Oleg A; Balázsi, Gábor; Gennaro, Maria Laura

    2010-01-01

    Bacterial persistence is the phenomenon in which a genetically identical fraction of a bacterial population can survive exposure to stress by reduction or cessation of growth. Persistence in mycobacteria has been recently linked to a stress-response network, consisting of the MprA/MprB two-component system and alternative sigma factor σ E . This network contains multiple positive transcriptional feedback loops which may give rise to bistability, making it a good candidate for controlling the mycobacterial persistence switch. To analyze the possibility of bistability, we develop a method that involves decoupling of the network into transcriptional and post-translational interaction modules. As a result we reduce the dimensionality of the dynamical system and independently analyze input–output relations in the two modules to formulate a necessary condition for bistability in terms of their logarithmic gains. We show that neither the positive autoregulation in the MprA/MprB network nor the σ E -mediated transcriptional feedback is sufficient to induce bistability in a biochemically realistic parameter range. Nonetheless, inclusion of the post-translational regulation of σ E by RseA increases the effective cooperativity of the system, resulting in bistability that is robust to parameter variation. We predict that overexpression or deletion of RseA, the key element controlling the ultrasensitive response, can eliminate bistability

  9. Phase-dependent optical bistability and multistability in a semiconductor quantum well system

    International Nuclear Information System (INIS)

    Wang Zhiping; Fan Hongyi

    2010-01-01

    We theoretically investigate the hybrid absorptive-dispersive optical bistability and multistability in a four-level inverted-Y quantum well system inside a unidirectional ring cavity. We find that the coupling field, the pumping field as well as the cycling field can affect the optical bistability and multistability dramatically, which can be used to manipulate efficiently the threshold intensity and the hysteresis loop. The effects of the relative phase and the electronic cooperation parameter on the OB and OM are also studied. Our study is much more practical than its atomic counterpart due to its flexible design and the wide adjustable parameters. Thus, it may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

  10. Bifurcation properties of nematic liquid crystals exposed to an electric field: Switchability, bistability, and multistability

    KAUST Repository

    Cummings, L. J.

    2013-07-01

    Bistable liquid crystal displays (LCDs) offer the potential for considerable power savings compared with conventional (monostable) LCDs. The existence of two (or more) stable field-free states that are optically distinct means that contrast can be maintained in a display without an externally applied electric field. An applied field is required only to switch the device from one state to the other, as needed. In this paper we examine the basic physical principles involved in generating multiple stable states and the switching between these states. We consider a two-dimensional geometry in which variable surface anchoring conditions are used to control the steady-state solutions and explore how different anchoring conditions can influence the number and type of solutions and whether or not switching is possible between the states. We find a wide range of possible behaviors, including bistability, tristability, and tetrastability, and investigate how the solution landscape changes as the boundary conditions are tuned. © 2013 American Physical Society.

  11. Control of stochastic resonance in bistable systems by using periodic signals

    International Nuclear Information System (INIS)

    Min, Lin; Li-Min, Fang; Yong-Jun, Zheng

    2009-01-01

    According to the characteristic structure of double wells in bistable systems, this paper analyses stochastic fluctuations in the single potential well and probability transitions between the two potential wells and proposes a method of controlling stochastic resonance by using a periodic signal. Results of theoretical analysis and numerical simulation show that the phenomenon of stochastic resonance happens when the time scales of the periodic signal and the noise-induced probability transitions between the two potential wells achieve stochastic synchronization. By adding a bistable system with a controllable periodic signal, fluctuations in the single potential well can be effectively controlled, thus affecting the probability transitions between the two potential wells. In this way, an effective control can be achieved which allows one to either enhance or realize stochastic resonance

  12. Towards an optimal model for a bistable nematic liquid crystal display device

    KAUST Repository

    Cummings, L. J.

    2013-03-13

    Bistable liquid crystal displays offer the potential for considerable power savings compared with conventional (monostable) LCDs. The existence of two stable field-free states that are optically distinct means that contrast can be maintained in a display without an externally applied electric field. An applied field is required only to switch the device from one state to the other, as needed. In this paper we examine a theoretical model of a possible bistable device, originally proposed by Cummings and Richardson (Euro J Appl Math 17:435-463 2006), and explore means by which it may be optimized, in terms of optical contrast, manufacturing considerations, switching field strength, and switching times. The compromises inherent in these conflicting design criteria are discussed. © 2013 Springer Science+Business Media Dordrecht.

  13. Vibration Energy Harvester with Bi-stable Curved Beam Spring Offset by Gravitational Acceleration

    International Nuclear Information System (INIS)

    Yamamoto, Koki; Fujita, Takayuki; Kanda, Kensuke; Maenaka, Kazusuke; Badel, Adrien; Formosa, Fabien

    2015-01-01

    We developed MEMS bi-stable spring for vibration energy harvester (VEH), which consists of intrinsically curved shape spring and gravitational acceleration. By applying the gravitational acceleration, the curved beam is offset to the gravity direction. It will make more symmetrical bi-stable motion and the symmetry is improved from 3.3 to 65.4%. We proposed that the combination between curved beam and gravity acceleration for decreasing snap- through acceleration. From the analytical result, we investigate the combination can effective to use for decreasing of snap-through force. We also fabricated the prototype device by using MEMS fabrication process. The frequency response for horizontal direction and the acceleration response for vertical direction are measured. The acceleration response shows that the gravitational acceleration improves the symmetry of snap-through force. (paper)

  14. Double-well chimeras in 2D lattice of chaotic bistable elements

    Science.gov (United States)

    Shepelev, I. A.; Bukh, A. V.; Vadivasova, T. E.; Anishchenko, V. S.; Zakharova, A.

    2018-01-01

    We investigate spatio-temporal dynamics of a 2D ensemble of nonlocally coupled chaotic cubic maps in a bistability regime. In particular, we perform a detailed study on the transition ;coherence - incoherence; for varying coupling strength for a fixed interaction radius. For the 2D ensemble we show the appearance of amplitude and phase chimera states previously reported for 1D ensembles of nonlocally coupled chaotic systems. Moreover, we uncover a novel type of chimera state, double-well chimera, which occurs due to the interplay of the bistability of the local dynamics and the 2D ensemble structure. Additionally, we find double-well chimera behavior for steady states which we call double-well chimera death. A distinguishing feature of chimera patterns observed in the lattice is that they mainly combine clusters of different chimera types: phase, amplitude and double-well chimeras.

  15. Phase-locking and bistability in neuronal networks with synaptic depression

    Science.gov (United States)

    Akcay, Zeynep; Huang, Xinxian; Nadim, Farzan; Bose, Amitabha

    2018-02-01

    We consider a recurrent network of two oscillatory neurons that are coupled with inhibitory synapses. We use the phase response curves of the neurons and the properties of short-term synaptic depression to define Poincaré maps for the activity of the network. The fixed points of these maps correspond to phase-locked modes of the network. Using these maps, we analyze the conditions that allow short-term synaptic depression to lead to the existence of bistable phase-locked, periodic solutions. We show that bistability arises when either the phase response curve of the neuron or the short-term depression profile changes steeply enough. The results apply to any Type I oscillator and we illustrate our findings using the Quadratic Integrate-and-Fire and Morris-Lecar neuron models.

  16. Study on monostable and bistable reaction-diffusion equations by iteration of travelling wave maps

    Science.gov (United States)

    Yi, Taishan; Chen, Yuming

    2017-12-01

    In this paper, based on the iterative properties of travelling wave maps, we develop a new method to obtain spreading speeds and asymptotic propagation for monostable and bistable reaction-diffusion equations. Precisely, for Dirichlet problems of monostable reaction-diffusion equations on the half line, by making links between travelling wave maps and integral operators associated with the Dirichlet diffusion kernel (the latter is NOT invariant under translation), we obtain some iteration properties of the Dirichlet diffusion and some a priori estimates on nontrivial solutions of Dirichlet problems under travelling wave transformation. We then provide the asymptotic behavior of nontrivial solutions in the space-time region for Dirichlet problems. These enable us to develop a unified method to obtain results on heterogeneous steady states, travelling waves, spreading speeds, and asymptotic spreading behavior for Dirichlet problem of monostable reaction-diffusion equations on R+ as well as of monostable/bistable reaction-diffusion equations on R.

  17. Bistability in self-activating genes regulated by non-coding RNAs

    International Nuclear Information System (INIS)

    Miro-Bueno, Jesus

    2015-01-01

    Non-coding RNA molecules are able to regulate gene expression and play an essential role in cells. On the other hand, bistability is an important behaviour of genetic networks. Here, we propose and study an ODE model in order to show how non-coding RNA can produce bistability in a simple way. The model comprises a single gene with positive feedback that is repressed by non-coding RNA molecules. We show how the values of all the reaction rates involved in the model are able to control the transitions between the high and low states. This new model can be interesting to clarify the role of non-coding RNA molecules in genetic networks. As well, these results can be interesting in synthetic biology for developing new genetic memories and biomolecular devices based on non-coding RNAs

  18. Entanglement and bistability in coupled quantum dots inside a driven cavity

    International Nuclear Information System (INIS)

    Mitra, Arnab; Vyas, Reeta

    2010-01-01

    Generation and dissipation of entanglement between two coupled quantum dots (QDs) in a cavity driven by a coherent field is studied. We find that it is possible to generate and sustain a large amount of entanglement between the quantum dots in the steady state, even in the presence of strong decay in both the cavity and the dots. We investigate the effect of different parameters (decay rates, coupling strengths, and detunings) on entanglement. We find that the cavity field shows bistability and study the effect of relevant parameters on the existence of this bistable behavior. We also study the correlation between the cavity field and the entanglement between the dots. The experimental viability of the proposed scheme is discussed.

  19. Input-Independent Energy Harvesting in Bistable Lattices from Transition Waves.

    Science.gov (United States)

    Hwang, Myungwon; Arrieta, Andres F

    2018-02-26

    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. We achieve further localisation of energy and numerically observe a breather-like mode for the first time in this type of lattice, improving the harvesting performance by an order of magnitude. Our approach considers generic bistable unit cells and thus provides a universal mechanism to harvest energy and realise metamaterials effectively behaving as a capacitor and power delivery system.

  20. Fractionation of parietal function in bistable perception probed with concurrent TMS-EEG.

    Science.gov (United States)

    Schauer, Georg; Chang, Acer; Schwartzman, David; Rae, Charlotte L; Iriye, Heather; Seth, Anil K; Kanai, Ryota

    2016-08-16

    When visual input has conflicting interpretations, conscious perception can alternate spontaneously between these possible interpretations. This is called bistable perception. Previous neuroimaging studies have indicated the involvement of two right parietal areas in resolving perceptual ambiguity (ant-SPLr and post-SPLr). Transcranial magnetic stimulation (TMS) studies that selectively interfered with the normal function of these regions suggest that they play opposing roles in this type of perceptual switch. In the present study, we investigated this fractionation of parietal function by use of combined TMS with electroencephalography (EEG). Specifically, while participants viewed either a bistable stimulus, a replay stimulus, or resting-state fixation, we applied single pulse TMS to either location independently while simultaneously recording EEG. Combined with participant's individual structural magnetic resonance imaging (MRI) scans, this dataset allows for complex analyses of the effect of TMS on neural time series data, which may further elucidate the causal role of the parietal cortex in ambiguous perception.

  1. Oscillatory pulses and wave trains in a bistable reaction-diffusion system with cross diffusion.

    Science.gov (United States)

    Zemskov, Evgeny P; Tsyganov, Mikhail A; Horsthemke, Werner

    2017-01-01

    We study waves with exponentially decaying oscillatory tails in a reaction-diffusion system with linear cross diffusion. To be specific, we consider a piecewise linear approximation of the FitzHugh-Nagumo model, also known as the Bonhoeffer-van der Pol model. We focus on two types of traveling waves, namely solitary pulses that correspond to a homoclinic solution, and sequences of pulses or wave trains, i.e., a periodic solution. The effect of cross diffusion on wave profiles and speed of propagation is analyzed. We find the intriguing result that both pulses and wave trains occur in the bistable cross-diffusive FitzHugh-Nagumo system, whereas only fronts exist in the standard bistable system without cross diffusion.

  2. Parietal theta burst TMS: Functional fractionation observed during bistable perception not evident in attention tasks.

    Science.gov (United States)

    Schauer, Georg; Kanai, Ryota; Brascamp, Jan W

    2016-02-01

    When visual input is ambiguous, perception spontaneously alternates between interpretations: bistable perception. Studies have identified two distinct sites near the right intraparietal sulcus where inhibitory transcranial magnetic stimulation (TMS) affects the frequency of occurrence of these alternations, but strikingly with opposite directions of effect for the two sites. Lesion and TMS studies on spatial and sustained attention have also indicated a parcellation of right parietal cortex, into areas serving distinct attentional functions. We used the exact TMS procedure previously employed to affect bistable perception, yet measured its effect on spatial and sustained attention tasks. Although there was a trend for TMS to affect performance, trends were consistently similar for both parietal sites, with no indication of opposite effects. We interpret this as signifying that the previously observed parietal fractionation of function regarding the perception of ambiguous stimuli is not due to TMS-induced modification of spatial or sustained attention. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Optical wall dynamics induced by coexistence of monostable and bistable spatial regions.

    Science.gov (United States)

    Odent, V; Louvergneaux, E; Clerc, M G; Andrade-Silva, I

    2016-11-01

    When nonequilibrium extended homogeneous systems exhibit multistability, it leads to the presence of domain walls between the existing equilibria. Depending on the stability of the steady states, the dynamics differs. Here, we consider the interface dynamics in the case of a spatially inhomogeneous system, namely, an optical system where the control parameter is spatially Gaussian. Then interfaces connect the monostable and the bistable nonuniform states that are associated with two distinct spatial regions. The coexistence of these two regions of different stability induces relaxation dynamics and the propagation of a wall with a time-dependent speed. We emphasize analytically these two dynamical behaviors using a generic bistable model. Experimentally, an inhomogeneous Gaussian light beam traveling through either a dye-doped liquid crystal cell or a Kerr cavity depicts these behaviors, in agreement with the theoretical predictions.

  4. Lake Restoration in Terms of Ecological Resilience: a Numerical Study of Biomanipulations under Bistable Conditions

    Directory of Open Access Journals (Sweden)

    Takashi Amemiya

    2005-12-01

    Full Text Available An abstract version of the comprehensive aquatic simulation model (CASM is found to exhibit bistability under intermediate loading of nutrient input, supporting the alternative-stable-states theory and field observations for shallow lakes. Our simulations of biomanipulations under the bistable conditions reveal that a reduction in the abundance of zooplanktivorous fish cannot switch the system from a turbid to a clear state. Rather, a direct reduction of phytoplankton and detritus was found to be most effective to make this switch in the present model. These results imply that multiple manipulations may be effective for practical restorations of lakes. We discuss the present results of biomanipulations in terms of ecological resilience in multivariable systems or natural systems.

  5. Temporal cross-correlation asymmetry and departure from equilibrium in a bistable chemical system.

    Science.gov (United States)

    Bianca, C; Lemarchand, A

    2014-06-14

    This paper aims at determining sustained reaction fluxes in a nonlinear chemical system driven in a nonequilibrium steady state. The method relies on the computation of cross-correlation functions for the internal fluctuations of chemical species concentrations. By employing Langevin-type equations, we derive approximate analytical formulas for the cross-correlation functions associated with nonlinear dynamics. Kinetic Monte Carlo simulations of the chemical master equation are performed in order to check the validity of the Langevin equations for a bistable chemical system. The two approaches are found in excellent agreement, except for critical parameter values where the bifurcation between monostability and bistability occurs. From the theoretical point of view, the results imply that the behavior of cross-correlation functions cannot be exploited to measure sustained reaction fluxes in a specific nonlinear system without the prior knowledge of the associated chemical mechanism and the rate constants.

  6. Stochastic resonance in an asymmetric bistable system driven by multiplicative colored noise and additive white noise

    International Nuclear Information System (INIS)

    Zhou Bingchang; Xu Wei

    2008-01-01

    The phenomenon of stochastic resonance (SR) in a bistable system driven by multiplicative colored and additive white noises and a periodic rectangular signal with a constant component is studied by using the unified colored noise approximation and the theory of signal-to-noise (SNR) in the adiabatic limit. The analytic expression of the SNR is obtained for arbitrary signal amplitude without being restricted to small amplitudes. The SNR is a non-monotonic function of intensities of multiplicative colored and additive white noises and correlation time of multiplicative colored noise, so SR exhibits in the bistable system. The effects of potential asymmetry r and correlation time τ of multiplicative colored noise on SNR are opposite. Moreover, It is more sensitive to control SR through adjusting the additive white noise intensity D than adjusting the multiplicative colored noise intensity Q

  7. Review of inductively coupled plasmas: Nano-applications and bistable hysteresis physics

    Science.gov (United States)

    Lee, Hyo-Chang

    2018-03-01

    Many different gas discharges and plasmas exhibit bistable states under a given set of conditions, and the history-dependent hysteresis that is manifested by intensive quantities of the system upon variation of an external parameter has been observed in inductively coupled plasmas (ICPs). When the external parameters (such as discharge powers) increase, the plasma density increases suddenly from a low- to high-density mode, whereas decreasing the power maintains the plasma in a relatively high-density mode, resulting in significant hysteresis. To date, a comprehensive description of plasma hysteresis and a physical understanding of the main mechanism underlying their bistability remain elusive, despite many experimental observations of plasma bistability conducted under radio-frequency ICP excitation. This fundamental understanding of mode transitions and hysteresis is essential and highly important in various applied fields owing to the widespread use of ICPs, such as semiconductor/display/solar-cell processing (etching, deposition, and ashing), wireless light lamp, nanostructure fabrication, nuclear-fusion operation, spacecraft propulsion, gas reformation, and the removal of hazardous gases and materials. If, in such applications, plasma undergoes a mode transition and hysteresis occurs in response to external perturbations, the process result will be strongly affected. Due to these reasons, this paper comprehensively reviews both the current knowledge in the context of the various applied fields and the global understanding of the bistability and hysteresis physics in the ICPs. At first, the basic understanding of the ICP is given. After that, applications of ICPs to various applied fields of nano/environmental/energy-science are introduced. Finally, the mode transition and hysteresis in ICPs are studied in detail. This study will show the fundamental understanding of hysteresis physics in plasmas and give open possibilities for applications to various applied

  8. Demonstration of brain noise on human EEG signals in perception of bistable images

    Science.gov (United States)

    Grubov, Vadim V.; Runnova, Anastasiya E.; Kurovskaya, Maria K.; Pavlov, Alexey N.; Koronovskii, Alexey A.; Hramov, Alexander E.

    2016-03-01

    In this report we studied human brain activity in the case of bistable visual perception. We proposed a new approach for quantitative characterization of this activity based on analysis of EEG oscillatory patterns and evoked potentials. Accordingly to theoretical background, obtained experimental EEG data and results of its analysis we studied a characteristics of brain activity during decision-making. Also we have shown that decisionmaking process has the special patterns on the EEG data.

  9. Chimera states in an ensemble of linearly locally coupled bistable oscillators

    Science.gov (United States)

    Shchapin, D. S.; Dmitrichev, A. S.; Nekorkin, V. I.

    2017-11-01

    Chimera states in a system with linear local connections have been studied. The system is a ring ensemble of analog bistable self-excited oscillators with a resistive coupling. It has been shown that the existence of chimera states is not due to the nonidentity of oscillators and noise, which is always present in real experiments, but is due to the nonlinear dynamics of the system on invariant tori with various dimensions.

  10. Basins of attraction of the bistable region of time-delayed cutting dynamics

    Science.gov (United States)

    Yan, Yao; Xu, Jian; Wiercigroch, Marian

    2017-09-01

    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. Special attention was paid to the influences of delayed initial conditions, starting points, and states at time zero on the long-term dynamics of time-delayed systems. By using this concept, it has been confirmed that the chatter is prone to occur when the waviness frequency in the workpiece surface coincides with the effective natural frequency of the cutting process. Further investigations unveil a thin "boundary layer" inside the UZ in the immediate vicinity of the stability boundary, in which we observe an extremely fast growth of the chatter basin stability. The results reveal that the system is more stable when the initial cutting depth is smaller. The physics of the tool deflection at the instant of the tool-workpiece engagement is used to evaluate the cutting safety, and the safe level could be zero when the geometry of tool engagement is unfavorable. Finally, the basins of attraction are used to quench the chatter by a single strike, where the resultant "islands" offer an opportunity to suppress the chatter even when the cutting is very close to the stability boundary.

  11. Solution-verified reliability analysis and design of bistable MEMS using error estimation and adaptivity.

    Energy Technology Data Exchange (ETDEWEB)

    Eldred, Michael Scott; Subia, Samuel Ramirez; Neckels, David; Hopkins, Matthew Morgan; Notz, Patrick K.; Adams, Brian M.; Carnes, Brian; Wittwer, Jonathan W.; Bichon, Barron J.; Copps, Kevin D.

    2006-10-01

    This report documents the results for an FY06 ASC Algorithms Level 2 milestone combining error estimation and adaptivity, uncertainty quantification, and probabilistic design capabilities applied to the analysis and design of bistable MEMS. Through the use of error estimation and adaptive mesh refinement, solution verification can be performed in an automated and parameter-adaptive manner. The resulting uncertainty analysis and probabilistic design studies are shown to be more accurate, efficient, reliable, and convenient.

  12. Characterization of conformational dynamics of bistable RNA by equilibrium and non-equilibrium NMR.

    Science.gov (United States)

    Fürtig, Boris; Reining, Anke; Sochor, Florian; Oberhauser, Eva Marie; Heckel, Alexander; Schwalbe, Harald

    2014-12-19

    Unlike proteins, a given RNA sequence can adopt more than a single conformation. The two (or more) conformations are long-lived and have similar stabilities, but interconvert only slowly. Such bi- or multistability is often linked to the biological functions of the RNA. This unit describes how nuclear magnetic resonance (NMR) spectroscopy can be used to characterize the conformational dynamics of bistable RNAs. Copyright © 2014 John Wiley & Sons, Inc.

  13. Basins of attraction of the bistable region of time-delayed cutting dynamics.

    Science.gov (United States)

    Yan, Yao; Xu, Jian; Wiercigroch, Marian

    2017-09-01

    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. Special attention was paid to the influences of delayed initial conditions, starting points, and states at time zero on the long-term dynamics of time-delayed systems. By using this concept, it has been confirmed that the chatter is prone to occur when the waviness frequency in the workpiece surface coincides with the effective natural frequency of the cutting process. Further investigations unveil a thin "boundary layer" inside the UZ in the immediate vicinity of the stability boundary, in which we observe an extremely fast growth of the chatter basin stability. The results reveal that the system is more stable when the initial cutting depth is smaller. The physics of the tool deflection at the instant of the tool-workpiece engagement is used to evaluate the cutting safety, and the safe level could be zero when the geometry of tool engagement is unfavorable. Finally, the basins of attraction are used to quench the chatter by a single strike, where the resultant "islands" offer an opportunity to suppress the chatter even when the cutting is very close to the stability boundary.

  14. Method of bistable optical information storage using antiferroelectric phase PLZT ceramics

    Science.gov (United States)

    Land, Cecil E.

    1990-01-01

    A method for bistable storage of binary optical information includes an antiferroelectric (AFE) lead lanthanum zirconate titanate (PLZT) layer having a stable antiferroelectric first phase and a ferroelectric (FE) second phase obtained by applying a switching electric field across the surface of the device. Optical information is stored by illuminating selected portions of the layer to photoactivate an FE to AFE transition in those portions. Erasure of the stored information is obtained by reapplying the switching field.

  15. A Compliant Bistable Mechanism Design Incorporating Elastica Buckling Beam Theory and Pseudo-Rigid-Body Model

    DEFF Research Database (Denmark)

    Sönmez, Ümit; Tutum, Cem Celal

    2008-01-01

    In this work, a new compliant bistable mechanism design is introduced. The combined use of pseudo-rigid-body model (PRBM) and the Elastica buckling theory is presented for the first time to analyze the new design. This mechanism consists of the large deflecting straight beams, buckling beams...... and the buckling Elastica solution for an original compliant mechanism kinematic analysis. New compliant mechanism designs are presented to highlight where such combined kinematic analysis is required....

  16. Indicators of Arctic Sea Ice Bistability in Climate Model Simulations and Observations

    Science.gov (United States)

    2014-09-30

    associated with the ice - albedo feedback and the seasonal melt and growth of sea ice , as well as horizontal climate variations on a global domain. (2...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Indicators of Arctic Sea Ice Bistability in Climate...possibility that the climate system supports multiple Arctic sea ice states that are relevant for the evolution of sea ice during the next several

  17. Effects of error feedback on a nonlinear bistable system with stochastic resonance

    International Nuclear Information System (INIS)

    Li Jian-Long; Zhou Hui

    2012-01-01

    In this paper, we discuss the effects of error feedback on the output of a nonlinear bistable system with stochastic resonance. The bit error rate is employed to quantify the performance of the system. The theoretical analysis and the numerical simulation are presented. By investigating the performances of the nonlinear systems with different strengths of error feedback, we argue that the presented system may provide guidance for practical nonlinear signal processing

  18. Statistical approach to bistable behaviour of a nonlinear system in a stationary field

    International Nuclear Information System (INIS)

    Luks, A.; Perina, J.; Perinova, V.; Bertolotti, M.; Sibilia, C.

    1984-01-01

    The quantum statistical properties of an elastic scattering process are investigated comprising crossed light beams which are in interaction with a particle (electron) beam treated as ''two-step'' system. Using the master equation and the generalized Fokker-Planck equation techniques, the integrated intensities are characterized by their probability distributions and it is demonstrated that single modes exhibit two-peak bistable behaviour. (author)

  19. Single-Trial Decoding of Bistable Perception Based on Sparse Nonnegative Tensor Decomposition

    Science.gov (United States)

    Wang, Zhisong; Maier, Alexander; Logothetis, Nikos K.; Liang, Hualou

    2008-01-01

    The study of the neuronal correlates of the spontaneous alternation in perception elicited by bistable visual stimuli is promising for understanding the mechanism of neural information processing and the neural basis of visual perception and perceptual decision-making. In this paper, we develop a sparse nonnegative tensor factorization-(NTF)-based method to extract features from the local field potential (LFP), collected from the middle temporal (MT) visual cortex in a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. We apply the feature extraction approach to the multichannel time-frequency representation of the intracortical LFP data. The advantages of the sparse NTF-based feature extraction approach lies in its capability to yield components common across the space, time, and frequency domains yet discriminative across different conditions without prior knowledge of the discriminating frequency bands and temporal windows for a specific subject. We employ the support vector machines (SVMs) classifier based on the features of the NTF components for single-trial decoding the reported perception. Our results suggest that although other bands also have certain discriminability, the gamma band feature carries the most discriminative information for bistable perception, and that imposing the sparseness constraints on the nonnegative tensor factorization improves extraction of this feature. PMID:18528515

  20. A simple photometric factor in perceived depth order of bistable transparency patterns.

    Science.gov (United States)

    Fukiage, Taiki; Oishi, Takeshi; Ikeuchi, Katsushi

    2014-05-05

    Previous studies on perceptual transparency defined the photometric condition in which perceived depth ordering between two surfaces becomes ambiguous. Even under this bistable transparency condition, it is known that depth-order perceptions are often biased toward one specific interpretation (Beck, Prazdny, & Ivry, 1984; Delogu, Fedorov, Belardinelli, & van Leeuwen, 2010; Kitaoka, 2005; Oyama & Nakahara, 1960). In this study, we examined what determines the perceived depth ordering for bistable transparency patterns using stimuli that simulated two partially overlapping disks resulting in four regions: a (background), b (portion of right disk), p (portion of left disk), and q (shared region). In contrast to the previous theory that proposed contributions of contrast against the background region (i.e., contrast at contour b/a and contrast at contour p/a) to perceived depth order in bistable transparency patterns, the present study demonstrated that contrast against the background region has little influence on perceived depth order compared with contrast against the shared region (i.e., contrast at contour b/q and contrast at contour p/q). In addition, we found that the perceived depth ordering is well predicted by a simpler model that takes into consideration only relative size of lightness difference against the shared region. Specifically, the probability that the left disk is perceived as being in front is proportional to (|b - q| - |p - q|) / (|b - q| + |p - q|) calculated based on lightness.

  1. On square-wave-driven stochastic resonance for energy harvesting in a bistable system

    Energy Technology Data Exchange (ETDEWEB)

    Su, Dongxu, E-mail: sudx@iis.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, Tokyo 1538505 (Japan); Zheng, Rencheng; Nakano, Kimihiko [Institute of Industrial Science, The University of Tokyo, Tokyo 1538505 (Japan); Cartmell, Matthew P [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2014-11-15

    Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.

  2. On square-wave-driven stochastic resonance for energy harvesting in a bistable system

    International Nuclear Information System (INIS)

    Su, Dongxu; Zheng, Rencheng; Nakano, Kimihiko; Cartmell, Matthew P

    2014-01-01

    Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation

  3. Feedback-induced bistability of an optically levitated nanoparticle: A Fokker-Planck treatment

    Science.gov (United States)

    Ge, Wenchao; Rodenburg, Brandon; Bhattacharya, M.

    2016-08-01

    Optically levitated nanoparticles have recently emerged as versatile platforms for investigating macroscopic quantum mechanics and enabling ultrasensitive metrology. In this paper we theoretically consider two damping regimes of an optically levitated nanoparticle cooled by cavityless parametric feedback. Our treatment is based on a generalized Fokker-Planck equation derived from the quantum master equation presented recently and shown to agree very well with experiment [B. Rodenburg, L. P. Neukirch, A. N. Vamivakas, and M. Bhattacharya, Quantum model of cooling and force sensing with an optically trapped nanoparticle, Optica 3, 318 (2016), 10.1364/OPTICA.3.000318]. For low damping, we find that the resulting Wigner function yields the single-peaked oscillator position distribution and recovers the appropriate energy distribution derived earlier using a classical theory and verified experimentally [J. Gieseler, R. Quidant, C. Dellago, and L. Novotny, Dynamic relaxation of a levitated nanoparticle from a non-equilibrium steady state, Nat. Nano. 9, 358 (2014), 10.1038/nnano.2014.40]. For high damping, in contrast, we predict a double-peaked position distribution, which we trace to an underlying bistability induced by feedback. Unlike in cavity-based optomechanics, stochastic processes play a major role in determining the bistable behavior. To support our conclusions, we present analytical expressions as well as numerical simulations using the truncated Wigner function approach. Our work opens up the prospect of developing bistability-based devices, characterization of phase-space dynamics, and investigation of the quantum-classical transition using levitated nanoparticles.

  4. Continuous control of asymmetric forebody vortices in a bi-stable state

    Science.gov (United States)

    Wang, Qi-te; Cheng, Ke-ming; Gu, Yun-song; Li, Zhuo-qi

    2018-02-01

    Aiming at the problem of continuous control of asymmetric forebody vortices at a high angle of attack in a bi-stable regime, a dual synthetic jet actuator embedded in an ogive forebody was designed. Alternating unsteady disturbance with varying degree asymmetrical flow fields near the nozzles is generated by adjusting the duty cycle of the drive signal of the actuator, specifically embodying the asymmetric time-averaged pattern of jet velocity, vorticity, and turbulent kinetic energy. Experimental results show that within the range of relatively high angles of attack, including the angle-of-attack region in a bi-stable state, the lateral force of the ogive forebody is continuously controlled by adjusting the duty cycle of the drive signal; the position of the forebody vortices in space, the vorticity magnitude, the total pressure coefficient near the vortex core, and the vortex breakdown location are continuously changed with the duty cycle increased observed from the time-averaged flow field. Instantaneous flow field results indicate that although the forebody vortices are in an unsteady oscillation state, a continuous change in the forebody vortices' oscillation balance position as the duty cycle increases leads to a continuous change in the model's surface pressure distribution and time-averaged lateral force. Different from the traditional control principle, in this study, other different degree asymmetrical states of the forebody vortices except the bi-stable state are obtained using the dual synthetic jet control technology.

  5. Dynamics and bistability in a reduced model of the lac operon

    Science.gov (United States)

    Yildirim, Necmettin; Santillán, Moisés; Horike, Daisuke; Mackey, Michael C.

    2004-06-01

    It is known that the lac operon regulatory pathway is capable of showing bistable behavior. This is an important complex feature, arising from the nonlinearity of the involved mechanisms, which is essential to understand the dynamic behavior of this molecular regulatory system. To find which of the mechanisms involved in the regulation of the lac operon is the origin of bistability, we take a previously published model which accounts for the dynamics of mRNA, lactose, allolactose, permease and β-galactosidase involvement and simplify it by ignoring permease dynamics (assuming a constant permease concentration). To test the behavior of the reduced model, three existing sets of data on β-galactosidase levels as a function of time are simulated and we obtain a reasonable agreement between the data and the model predictions. The steady states of the reduced model were numerically and analytically analyzed and it was shown that it may indeed display bistability, depending on the extracellular lactose concentration and growth rate.

  6. Bistable Si dopants in the GaAs (1 1 0) surface

    International Nuclear Information System (INIS)

    Smakman, E P; Koenraad, P M

    2015-01-01

    In this review, recent work is discussed on bistable Si dopants in the GaAs (1 1 0) surface, studied by scanning tunneling microscopy (STM). The bistability arises because the dopant atom can switch between a positive and a negative charge state, which are associated with two different lattice configurations. Manipulation of the Si atom charge configuration is achieved by tuning the local band bending with the STM tip. Furthermore, illuminating the sample with a laser also influences the charge state, allowing the operation of the dopant atom as an optical switch. The switching dynamics without illumination is investigated in detail as a function of temperature, lateral tip position, and applied tunneling conditions. A physical model is presented that independently describes the thermal and quantum tunneling contributions to the switching frequency and charge state occupation of a single Si atom. The basic functionality of a memory cell is demonstrated employing a single bistable Si dopant as the active element, using the STM tip as a gate to write and read the information. (topical review)

  7. Traveling and Pinned Fronts in Bistable Reaction-Diffusion Systems on Networks

    Science.gov (United States)

    Kouvaris, Nikos E.; Kori, Hiroshi; Mikhailov, Alexander S.

    2012-01-01

    Traveling fronts and stationary localized patterns in bistable reaction-diffusion systems have been broadly studied for classical continuous media and regular lattices. Analogs of such non-equilibrium patterns are also possible in networks. Here, we consider traveling and stationary patterns in bistable one-component systems on random Erdös-Rényi, scale-free and hierarchical tree networks. As revealed through numerical simulations, traveling fronts exist in network-organized systems. They represent waves of transition from one stable state into another, spreading over the entire network. The fronts can furthermore be pinned, thus forming stationary structures. While pinning of fronts has previously been considered for chains of diffusively coupled bistable elements, the network architecture brings about significant differences. An important role is played by the degree (the number of connections) of a node. For regular trees with a fixed branching factor, the pinning conditions are analytically determined. For large Erdös-Rényi and scale-free networks, the mean-field theory for stationary patterns is constructed. PMID:23028746

  8. Stochastic stabilization of phenotypic States: the genetic bistable switch as a case study.

    Science.gov (United States)

    Weber, Marc; Buceta, Javier

    2013-01-01

    We study by means of analytical calculation and stochastic simulations how intrinsic noise modifies the bifurcation diagram of gene regulatory processes that can be effectively described by the Langevin formalism. In a general context, our study raises the intriguing question of how biochemical fluctuations redesign the epigenetic landscape in differentiation processes. We have applied our findings to a general class of regulatory processes that includes the simplest case that displays a bistable behavior and hence phenotypic variability: the genetic auto-activating switch. Thus, we explain why and how the noise promotes the stability of the low-state phenotype of the switch and show that the bistable region is extended when increasing the intensity of the fluctuations. This phenomenology is found in a simple one-dimensional model of the genetic switch as well as in a more detailed model that takes into account the binding of the protein to the promoter region. Altogether, we prescribe the analytical means to understand and quantify the noise-induced modifications of the bifurcation points for a general class of regulatory processes where the genetic bistable switch is included.

  9. Revisiting bistability in the lysis/lysogeny circuit of bacteriophage lambda.

    Directory of Open Access Journals (Sweden)

    Michael Bednarz

    Full Text Available The lysis/lysogeny switch of bacteriophage lambda serves as a paradigm for binary cell fate decision, long-term maintenance of cellular state and stimulus-triggered switching between states. In the literature, the system is often referred to as "bistable." However, it remains unclear whether this term provides an accurate description or is instead a misnomer. Here we address this question directly. We first quantify transcriptional regulation governing lysogenic maintenance using a single-cell fluorescence reporter. We then use the single-cell data to derive a stochastic theoretical model for the underlying regulatory network. We use the model to predict the steady states of the system and then validate these predictions experimentally. Specifically, a regime of bistability, and the resulting hysteretic behavior, are observed. Beyond the steady states, the theoretical model successfully predicts the kinetics of switching from lysogeny to lysis. Our results show how the physics-inspired concept of bistability can be reliably used to describe cellular phenotype, and how an experimentally-calibrated theoretical model can have accurate predictive power for cell-state switching.

  10. Theoretical Investigation of the Bistability Effect in Non-Self-Sustained Discharges in Kr and Ar

    International Nuclear Information System (INIS)

    Dyatko, N.A.; Napartovich, A.P.

    2004-01-01

    The electron energy distribution function and the related plasma parameters in non-self-sustained discharges in Kr and Ar are studied theoretically. The investigations are carried out by numerically solving the corresponding Boltzmann equation for the electron energy distribution function with allowance for electron-electron collisions. The electron energy distribution and electron density are calculated self-consistently as functions of the intensity q of the source of secondary electrons and the magnitude of the reduced electric field E/N. The main goal of the investigations was to determine the conditions under which the plasma exhibits bistable parameters. Calculations show that, for discharges in Kr, there is a certain range of q and E/N values in which the Boltzmann equation has two different stable solutions. For an Ar plasma, such a bistability effect was not found: over the parameter range under consideration, the Boltzmann equation has a unique solution. Various plasma parameters (such as the effective electron temperature, electron drift velocity, and electron current density) are calculated for different discharge conditions, including those corresponding to the bistability effect

  11. Stationary patterns in star networks of bistable units: Theory and application to chemical reactions.

    Science.gov (United States)

    Kouvaris, Nikos E; Sebek, Michael; Iribarne, Albert; Díaz-Guilera, Albert; Kiss, István Z

    2017-04-01

    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. Weak coupling results in trivial pinned states where the activation cannot propagate. At strong coupling, a uniform state is expected with active or inactive elements at small or large degree networks, respectively. A nontrivial stationary spatial pattern, corresponding to an activation pinning, is predicted to occur at an intermediate number of peripheral elements and at intermediate coupling strengths, where the central activation of the network is pinned, but the peripheral activation propagates toward the center. The results are confirmed in experiments with star networks of bistable electrochemical reactions. The experiments confirm the existence of the stationary spatial patterns and the dependence of coupling strength on the number of peripheral elements for transitions between pinned and retreating or spreading fronts in forced network configurations (where the central or periphery elements are forced to maintain their states).

  12. On-Demand Final State Control of a Surface-Bound Bistable Single Molecule Switch.

    Science.gov (United States)

    Garrido Torres, José A; Simpson, Grant J; Adams, Christopher J; Früchtl, Herbert A; Schaub, Renald

    2018-04-12

    Modern electronic devices perform their defined action because of the complete reliability of their individual active components (transistors, switches, diodes, and so forth). For instance, to encode basic computer units (bits) an electrical switch can be used. The reliability of the switch ensures that the desired outcome (the component's final state, 0 or 1) can be selected with certainty. No practical data storage device would otherwise exist. This reliability criterion will necessarily need to hold true for future molecular electronics to have the opportunity to emerge as a viable miniaturization alternative to our current silicon-based technology. Molecular electronics target the use of single-molecules to perform the actions of individual electronic components. On-demand final state control over a bistable unimolecular component has therefore been one of the main challenges in the past decade (1-5) but has yet to be achieved. In this Letter, we demonstrate how control of the final state of a surface-supported bistable single molecule switch can be realized. On the basis of the observations and deductions presented here, we further suggest an alternative strategy to achieve final state control in unimolecular bistable switches.

  13. Numerical and Experimental Studies on Nonlinear Dynamics and Performance of a Bistable Piezoelectric Cantilever Generator

    Directory of Open Access Journals (Sweden)

    Kangkang Guo

    2015-01-01

    Full Text Available A piezo-magneto-elastically coupled distributed-parameter model of a bistable piezoelectric cantilever generator is developed by using the generalized Hamilton principle. The influence of the spacing between two adjacent magnets on the static bifurcation characteristics of the system is studied and the range of magnet spacing corresponding to the bistable states is obtained. Numerical and experimental studies are carried out to analyze the bifurcation, response characteristics, and their impact on the electrical output performance under varying external excitations. Results indicate that interwell limit cycle motion of the beam around the two centers corresponds to optimum power output; interwell chaotic motion and multiperiodic motion including intrawell oscillations are less effective. At a given frequency, the phenomena of symmetric-breaking and amplitude-phase modulation are observed with increase of base excitation. Both period-doubling bifurcation and intermittency routes to chaotic motion in the bistable system are found. It can be observed that the power output is not proportional to the excitation level because of the bifurcation behaviours.

  14. Regularity, variability and bi-stability in the activity of cerebellar purkinje cells.

    Science.gov (United States)

    Rokni, Dan; Tal, Zohar; Byk, Hananel; Yarom, Yosef

    2009-01-01

    Recent studies have demonstrated that the membrane potential of Purkinje cells is bi-stable and that this phenomenon underlies bi-modal simple spike firing. Membrane potential alternates between a depolarized state, that is associated with spontaneous simple spike firing (up state), and a quiescent hyperpolarized state (down state). A controversy has emerged regarding the relevance of bi-stability to the awake animal, yet recordings made from behaving cat Purkinje cells have demonstrated that at least 50% of the cells exhibit bi-modal firing. The robustness of the phenomenon in vitro or in anaesthetized systems on the one hand, and the controversy regarding its expression in behaving animals on the other hand suggest that state transitions are under neuronal control. Indeed, we have recently demonstrated that synaptic inputs can induce transitions between the states and suggested that the role of granule cell input is to control the states of Purkinje cells rather than increase or decrease firing rate gradually. We have also shown that the state of a Purkinje cell does not only affect its firing but also the waveform of climbing fiber-driven complex spikes and the associated calcium influx. These findings call for a reconsideration of the role of Purkinje cells in cerebellar function. In this manuscript we review the recent findings on Purkinje cell bi-stability and add some analyses of its effect on the regularity and variability of Purkinje cell activity.

  15. Regularity, variabilty and bi-stability in the activity of cerebellar Purkinje cells

    Directory of Open Access Journals (Sweden)

    Dan Rokni

    2009-11-01

    Full Text Available Recent studies have demonstrated that the membrane potential of Purkinje cells is bi-stable and that this phenomenon underlies bi-modal simple spike firing. Membrane potential alternates between a depolarized state, that is associated with spontaneous simple spike firing (up state, and a quiescent hyperpolarized state (down state. A controversy has emerged regarding the relevance of bi-stability to the awake animal, yet recordings made from behaving cat Purkinje cells have demonstrated that at least 50% of the cells exhibit bi-modal firing. The robustness of the phenomenon in-vitro or in anaesthetized systems on the one hand, and the controversy regarding its expression in behaving animals on the other hand suggest that state transitions are under neuronal control. Indeed, we have recently demonstrated that synaptic inputs can induce transitions between the states and suggested that the role of granule cell input is to control the states of Purkinje cells rather than increase or decrease firing rate gradually. We have also shown that the state of a Purkinje cell does not only affect its firing but also the waveform of climbing fiber-driven complex spikes and the associated calcium influx. These findings call for a reconsideration of the role of Purkinje cells in cerebellar function. In this manuscript we review the recent findings on Purkinje cell bi-stability and add some analyses of its effect on the regularity and variability of Purkinje cell activity.

  16. Manually operatable on-chip bistable pneumatic microstructures for microfluidic manipulations.

    Science.gov (United States)

    Chen, Arnold; Pan, Tingrui

    2014-09-07

    Bistable microvalves are of particular interest because of their distinct nature of requiring energy consumption only during the transition between the open and closed states. This characteristic can be highly advantageous in reducing the number of external inputs and the complexity of control circuitries since microfluidic devices as contemporary lab-on-a-chip platforms are transferring from research settings to low-resource environments with high integrability and a small form factor. In this paper, we first present manually operatable, on-chip bistable pneumatic microstructures (BPMs) for microfluidic manipulation. The structural design and operation of the BPM devices can be readily integrated into any pneumatically powered microfluidic network consisting of pneumatic and fluidic channels. It is mainly composed of a vacuum activation chamber (VAC) and a pressure release chamber (PRC), of which users have direct control through finger pressing to switch either to the bistable vacuum state (VS) or the atmospheric state (AS). We have integrated multiple BPM devices into a 4-to-1 microfluidic multiplexor to demonstrate on-chip digital flow switching from different sources. Furthermore, we have shown its clinical relevance in a point-of-care diagnostic chip that processes blood samples to identify the distinct blood types (A/B/O) on-chip.

  17. Electrical bistabilities and memory mechanisms of nonvolatile organic bistable devices based on exfoliated muscovite-type mica nanoparticle/poly(methylmethacrylate) nanocomposites

    Science.gov (United States)

    Lim, Won Gyu; Lee, Dea Uk; Na, Han Gil; Kim, Hyoun Woo; Kim, Tae Whan

    2018-02-01

    Organic bistable devices (OBDs) with exfoliated mica nanoparticles (NPs) embedded into an insulating poly(methylmethacrylate) (PMMA) layer were fabricated by using a spin-coating method. Current-voltage (I-V) curves for the Al/PMMA/exfoliated mica NP/PMMA/indium-tin-oxide/glass devices at 300 K showed a clockwise current hysteresis behavior due to the existence of the exfoliated muscovite-type mica NPs, which is an essential feature for bistable devices. Write-read-erase-read data showed that the OBDs had rewritable nonvolatile memories and an endurance number of ON/OFF switching for the OBDs of 102 cycles. An ON/OFF ratio of 1 × 103 was maintained for retention times larger than 1 × 104 s. The memory mechanisms of the fabricated OBDs were described by using the trapping and the tunneling processes within a PMMA active layer containing exfoliated muscovite-type mica NPs on the basis of the energy band diagram and the I-V curves.

  18. Coupling between feedback loops in autoregulatory networks affects bistability range, open-loop gain and switching times

    International Nuclear Information System (INIS)

    Tiwari, Abhinav; Igoshin, Oleg A

    2012-01-01

    Biochemical regulatory networks governing diverse cellular processes such as stress-response, differentiation and cell cycle often contain coupled feedback loops. We aim at understanding how features of feedback architecture, such as the number of loops, the sign of the loops and the type of their coupling, affect network dynamical performance. Specifically, we investigate how bistability range, maximum open-loop gain and switching times of a network with transcriptional positive feedback are affected by additive or multiplicative coupling with another positive- or negative-feedback loop. We show that a network's bistability range is positively correlated with its maximum open-loop gain and that both quantities depend on the sign of the feedback loops and the type of feedback coupling. Moreover, we find that the addition of positive feedback could decrease the bistability range if we control the basal level in the signal-response curves of the two systems. Furthermore, the addition of negative feedback has the capacity to increase the bistability range if its dissociation constant is much lower than that of the positive feedback. We also find that the addition of a positive feedback to a bistable network increases the robustness of its bistability range, whereas the addition of a negative feedback decreases it. Finally, we show that the switching time for a transition from a high to a low steady state increases with the effective fold change in gene regulation. In summary, we show that the effect of coupled feedback loops on the bistability range and switching times depends on the underlying mechanistic details. (paper)

  19. The Reflective Learning Continuum: Reflecting on Reflection

    Science.gov (United States)

    Peltier, James W.; Hay, Amanda; Drago, William

    2005-01-01

    The importance of reflection to marketing educators is increasingly recognized. However, there is a lack of empirical research that considers reflection within the context of both the marketing and general business education literature. This article describes the use of an instrument that can be used to measure four identified levels of a…

  20. Transparent Electrochemical Gratings from a Patterned Bistable Silver Mirror.

    Science.gov (United States)

    Park, Chihyun; Na, Jongbeom; Han, Minsu; Kim, Eunkyoung

    2017-07-25

    Silver mirror patterns were formed reversibly on a polystyrene (PS)-patterned electrode to produce gratings through the electrochemical reduction of silver ions. The electrochemical gratings exhibited high transparency (T > 95%), similar to a see-through window, by matching the refractive index of the grating pattern with the surrounding medium. The gratings switch to a diffractive state upon the formation of a mirror pattern (T modulation, NIR light reflection, and on-demand heat transfer.

  1. Effect on the mean first passage time in symmetrical bistable systems by cross-correlation between noises

    International Nuclear Information System (INIS)

    Wang, J.; Cao, L.; Wu, D.J.

    2003-01-01

    We present an analytic investigation of the mean first passage time in two opposite directions (from the left well to the right well and from right to left) by studying symmetrical bistable systems driven by correlated Gaussian white noises, and prove that the mean first passage time in two opposite directions is not symmetrical any more when noises are correlated. As examples, the mean first passage time in the quartic bistable model and the sawtooth bistable model are calculated, respectively. From the analytic results of the mean first passage time, we testify further the relation T(from x - to x + ,λ)≠T(from x + to x - ,λ) in the same area of the parameter plan. Moreover, it is found that the dependences of T + (i.e., T(from x - to x + ,λ)) and T - (i.e., T(from x + to x - ,λ)) upon the multiplicative noise intensity Q and the additive noise intensity D exhibit entirely different properties. For same areas of the parameter plan: in the quartic bistable system, when the T + vs. Q curve exhibits a maximum, while the T - vs. Q curve is monotonous; when the T + vs. D curve is monotonous, while the T - vs. D curve experiences a phase transition from decreasing monotonously to possessing one minimum. Increasing Q, when the T + vs. D curve experiences a phase transition from decreasing monotonously to possessing one maximum, while the T - vs. D curve only increases monotonously. Similar behaviours also exist in the sawtooth bistable model

  2. Reflective photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Lentine, Anthony L.; Nielson, Gregory N.; Cruz-Campa, Jose Luis; Okandan, Murat; Goeke, Ronald S.

    2018-03-06

    A photovoltaic module includes colorized reflective photovoltaic cells that act as pixels. The colorized reflective photovoltaic cells are arranged so that reflections from the photovoltaic cells or pixels visually combine into an image on the photovoltaic module. The colorized photovoltaic cell or pixel is composed of a set of 100 to 256 base color sub-pixel reflective segments or sub-pixels. The color of each pixel is determined by the combination of base color sub-pixels forming the pixel. As a result, each pixel can have a wide variety of colors using a set of base colors, which are created, from sub-pixel reflective segments having standard film thicknesses.

  3. Phase dependence of optical bistability and multistability in a four-level quantum system near a plasmonic nanostructure

    International Nuclear Information System (INIS)

    Asadpour, Seyyed Hossein; Rahimpour Soleimani, H.

    2016-01-01

    The optical bistability and multistability properties of a four-level quantum system near a plasmonic nanostructure embedded in a unidirectional ring cavity are studied theoretically. Two orthogonal circularly polarized laser fields with the same frequency, different phases and electric fields amplitude are interacted by four-level quantum system. It is found that in the presence of the plasmonic nanostructure, the bistable behaviors related to one of the laser fields propagating through the unidirectional ring cavity can be modified by relative phase and amplitude control of another laser fields. Our obtained results show that the optical bistability can be converted into the optical multistability by varying the value of distance between the quantum system and the surface of the plasmonic nanostructure. Moreover, it is shown that under specific condition related to the distance, the lasing without population inversion can be obtained

  4. Electrical bistability and charge-transport mechanisms in cuprous sulfide nanosphere-poly(N-vinylcarbazole) composite films

    International Nuclear Information System (INIS)

    Tang Aiwei; Teng Feng; Liu Jie; Wang Yichao; Peng Hongshang; Hou Yanbing; Wang Yongsheng

    2011-01-01

    In this study, electrically bistable devices were fabricated by incorporating cuprous sulfide (Cu 2 S) nanospheres with mean size less than 10 nm into a poly(N-vinylcarbazole) (PVK) matrix. A remarkable electrical bistability was clearly observed in the current–voltage curves of the devices due to an electric-field-induced charge transfer between the dodecanethiol-capped Cu 2 S nanospheres and PVK. The maximum ON/OFF current ratio reached up to value as large as 10 4 , which was dependent on the mass ratios of Cu 2 S nanospheres to PVK, the amplitude of the scanning voltages, and the film thickness. The charge-transport mechanisms of the electrically bistable devices were described on the basis of the experimental results using different theoretical models of organic electronics.

  5. Phase dependence of optical bistability and multistability in a four-level quantum system near a plasmonic nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Asadpour, Seyyed Hossein; Rahimpour Soleimani, H., E-mail: Rahimpour@guilan.ac.ir [Computational Nanophysics Laboratory (CNL), Department of Physics, University of Guilan, Rasht (Iran, Islamic Republic of)

    2016-01-14

    The optical bistability and multistability properties of a four-level quantum system near a plasmonic nanostructure embedded in a unidirectional ring cavity are studied theoretically. Two orthogonal circularly polarized laser fields with the same frequency, different phases and electric fields amplitude are interacted by four-level quantum system. It is found that in the presence of the plasmonic nanostructure, the bistable behaviors related to one of the laser fields propagating through the unidirectional ring cavity can be modified by relative phase and amplitude control of another laser fields. Our obtained results show that the optical bistability can be converted into the optical multistability by varying the value of distance between the quantum system and the surface of the plasmonic nanostructure. Moreover, it is shown that under specific condition related to the distance, the lasing without population inversion can be obtained.

  6. Bistable four-wave mixing response in a semiconductor quantum dot coupled to a photonic crystal nanocavity.

    Science.gov (United States)

    Li, Jian-Bo; Xiao, Si; Liang, Shan; He, Meng-Dong; Luo, Jian-Hua; Kim, Nam-Chol; Chen, Li-Qun

    2017-10-16

    We perform a theoretical study of the bistable four-wave mixing (FWM) response in a coupled system comprised of a semiconductor quantum dot (SQD) and a photonic crystal (PC) nanocavity in which the SQD is embedded. It is shown that the shape of the FWM spectrum can switch among single-peaked, double-peaked, triple-peaked, and four-peaked arising from the vacuum Rabi splitting and the exciton-nanocavity coupling. Especially, we map out bistability phase diagrams within a parameter subspace of the system, and find that it is easy to turn on or off the bistable FWM response by only adjusting the excitation frequency or the pumping intensity. Our results offer a feasible means for measuring the SQD-PC nanocavity coupling strength and open a new avenue to design optical switches and memories.

  7. Activation of Transducin by Bistable Pigment Parapinopsin in the Pineal Organ of Lower Vertebrates.

    Science.gov (United States)

    Kawano-Yamashita, Emi; Koyanagi, Mitsumasa; Wada, Seiji; Tsukamoto, Hisao; Nagata, Takashi; Terakita, Akihisa

    2015-01-01

    Pineal organs of lower vertebrates contain several kinds of photosensitive molecules, opsins that are suggested to be involved in different light-regulated physiological functions. We previously reported that parapinopsin is an ultraviolet (UV)-sensitive opsin that underlies hyperpolarization of the pineal photoreceptor cells of lower vertebrates to achieve pineal wavelength discrimination. Although, parapinopsin is phylogenetically close to vertebrate visual opsins, it exhibits a property similar to invertebrate visual opsins and melanopsin: the photoproduct of parapinopsin is stable and reverts to the original dark states, demonstrating the nature of bistable pigments. Therefore, it is of evolutionary interest to identify a phototransduction cascade driven by parapinopsin and to compare it with that in vertebrate visual cells. Here, we showed that parapinopsin is coupled to vertebrate visual G protein transducin in the pufferfish, zebrafish, and lamprey pineal organs. Biochemical analyses demonstrated that parapinopsins activated transducin in vitro in a light-dependent manner, similar to vertebrate visual opsins. Interestingly, transducin activation by parapinopsin was provoked and terminated by UV- and subsequent orange-lights irradiations, respectively, due to the bistable nature of parapinopsin, which could contribute to a wavelength-dependent control of a second messenger level in the cell as a unique optogenetic tool. Immunohistochemical examination revealed that parapinopsin was colocalized with Gt2 in the teleost, which possesses rod and cone types of transducin, Gt1, and Gt2. On the other hand, in the lamprey, which does not possess the Gt2 gene, in situ hybridization suggested that parapinopsin-expressing photoreceptor cells contained Gt1 type transducin GtS, indicating that lamprey parapinopsin may use GtS in place of Gt2. Because it is widely accepted that vertebrate visual opsins having a bleaching nature have evolved from non-bleaching opsins

  8. Divergence of relative difference in Gaussian distribution function and stochastic resonance in a bistable system with frictionless state transition

    Science.gov (United States)

    Kasai, Seiya; Ichiki, Akihisa; Tadokoro, Yukihiro

    2018-03-01

    A bistable system efficiently detects a weak signal by adding noise, which is referred to as stochastic resonance. A previous theory deals with friction in state transition; however, this hypothesis is inadequate when friction force is negligible such as in nano- and molecular-scale systems. We show that, when the transition occurs without friction, the sensitivity of the bistable system to a Gaussian-noise-imposed weak signal becomes significantly high. The sensitivity is determined by the relative difference in noise distribution function. We find that the relative difference in Gaussian distribution function diverges in its tail edge, resulting in a high sensitivity in the present system.

  9. Optical bistability and multistability driven by external magnetic field in a dielectric slab doped with nanodiamond nitrogen vacancy centres

    Science.gov (United States)

    Nasehi, R.; Norouzi, F.

    2016-08-01

    The theoretical investigation of controlling the optical bistability (OB) and optical multistability (OM) in a dielectric medium doped with nanodiamond nitrogen vacancy centres under optical excitation are reported. The shape of the OB curve from dielectric slab can be tuned by changing the external magnetic field and polarization of the control beam. The effect of the intensity of the control laser field and the frequency detuning of probe laser field on the OB and OM behaviour are also discussed in this paper. The results obtained can be used for realizing an all-optical bistable switching or development of nanoelectronic devices.

  10. Bistable electroactive polymer for refreshable Braille display with improved actuation stability

    Science.gov (United States)

    Niu, Xiaofan; Brochu, Paul; Stoyanov, Hristiyan; Yun, Sung Ryul; Pei, Qibing

    2012-04-01

    Poly(t-butyl acrylate) is a bistable electroactive polymer (BSEP) capable of rigid-to-rigid actuation. The BSEP combines the large-strain actuation of dielectric elastomers with shape memory property. We have introduced a material approach to overcome pull-in instability in poly(t-butyl acrylate) that significantly improves the actuation lifetime at strains greater than 100%. Refreshable Braille display devices with size of a smartphone screen have been fabricated to manifest a potential application of the BSEP. We will report the testing results of the devices by a Braille user.

  11. Bistable optical devices with laser diodes coupled to absorbers of narrow spectral bandwidth.

    Science.gov (United States)

    Maeda, Y

    1994-06-20

    An optical signal inverter was demonstrated with a combination of the following two effects: One is the decrease of the transmission of an Er-doped YAG crystal with increasing red shift of a laser diode resulting from an increase in the injection current, and the other is a negative nonlinear absorption in which the transmission decreases inversely with increasing laser intensity. Because a hysteresis characteristic exists in the relationship between the wavelength and the injection current of the laser diode, an optical bistability was observed in this system.

  12. Optical bistability in erbium-doped yttrium aluminum garnet crystal combined with a laser diode.

    Science.gov (United States)

    Maeda, Y

    1994-01-10

    Optical bistability was observed in a simple structure of an injection laser diode combined with an erbium-doped yttrium aluminum garnet crystal. Since a hysteresis characteristic exists in the relationship between the wavelength and the injection current of a laser diode, an optical memory function capable of holding the output status is confirmed. In addition, an optical signal inversion was caused by the decrease of transmission of the erbium-doped yttrium aluminum garnet crystal against the red shift (principally mode hopping) of the laser diode. It is suggested that the switching time of this phenomenon is the time necessary for a mode hopping by current injection.

  13. Parity-breaking front bifurcation in bistable media: link between discrete and continuous versions

    International Nuclear Information System (INIS)

    Pazo, Diego; Deza, Roberto R.; Perez-Munuzuri, Vicente

    2005-01-01

    The effect of space-discretization in the onset of traveling fronts in symmetrically bistable media is studied. For the FitzHugh-Nagumo model stable standing and propagating front solutions coexist. In the continuum limit this region of coexistence shrinks to a (double-zero eigenvalue) point. The unfolding of this point severely restricts the possible scenarios for the transition from standing to propagating fronts, such that the route described here and the one reported in [Phys. Rev. E 64 (2001) 065203(R)] are the most typical scenarios

  14. Bistable intrinsic charge fluctuations of a dust grain subject to secondary electron emission in a plasma.

    Science.gov (United States)

    Shotorban, B

    2015-10-01

    A master equation was formulated to study intrinsic charge fluctuations of a grain in a plasma as ions and primary electrons are attached to the grain through collisional collection, and secondary electrons are emitted from the grain. Two different plasmas with Maxwellian and non-Maxwellian distributions were considered. The fluctuations could be bistable in either plasma when the secondary electron emission is present, as two stable macrostates, associated with two stable roots of the charge net current, may exist. Metastablity of fluctuations, manifested by the passage of the grain charge between two macrostates, was shown to be possible.

  15. Origami-based cellular metamaterial with auxetic, bistable, and self-locking properties

    Science.gov (United States)

    Kamrava, Soroush; Mousanezhad, Davood; Ebrahimi, Hamid; Ghosh, Ranajay; Vaziri, Ashkan

    2017-04-01

    We present a novel cellular metamaterial constructed from Origami building blocks based on Miura-ori fold. The proposed cellular metamaterial exhibits unusual properties some of which stemming from the inherent properties of its Origami building blocks, and others manifesting due to its unique geometrical construction and architecture. These properties include foldability with two fully-folded configurations, auxeticity (i.e., negative Poisson’s ratio), bistability, and self-locking of Origami building blocks to construct load-bearing cellular metamaterials. The kinematics and force response of the cellular metamaterial during folding were studied to investigate the underlying mechanisms resulting in its unique properties using analytical modeling and experiments.

  16. A bistable switch and anatomical site control Vibrio cholerae virulence gene expression in the intestine.

    Directory of Open Access Journals (Sweden)

    Alex T Nielsen

    2010-09-01

    Full Text Available A fundamental, but unanswered question in host-pathogen interactions is the timing, localization and population distribution of virulence gene expression during infection. Here, microarray and in situ single cell expression methods were used to study Vibrio cholerae growth and virulence gene expression during infection of the rabbit ligated ileal loop model of cholera. Genes encoding the toxin-coregulated pilus (TCP and cholera toxin (CT were powerfully expressed early in the infectious process in bacteria adjacent to epithelial surfaces. Increased growth was found to co-localize with virulence gene expression. Significant heterogeneity in the expression of tcpA, the repeating subunit of TCP, was observed late in the infectious process. The expression of tcpA, studied in single cells in a homogeneous medium, demonstrated unimodal induction of tcpA after addition of bicarbonate, a chemical inducer of virulence gene expression. Striking bifurcation of the population occurred during entry into stationary phase: one subpopulation continued to express tcpA, whereas the expression declined in the other subpopulation. ctxA, encoding the A subunit of CT, and toxT, encoding the proximal master regulator of virulence gene expression also exhibited the bifurcation phenotype. The bifurcation phenotype was found to be reversible, epigenetic and to persist after removal of bicarbonate, features consistent with bistable switches. The bistable switch requires the positive-feedback circuit controlling ToxT expression and formation of the CRP-cAMP complex during entry into stationary phase. Key features of this bistable switch also were demonstrated in vivo, where striking heterogeneity in tcpA expression was observed in luminal fluid in later stages of the infection. When this fluid was diluted into artificial seawater, bacterial aggregates continued to express tcpA for prolonged periods of time. The bistable control of virulence gene expression points to a

  17. The transition between monostable and bistable states induced by time delay in intracellular calcium oscillation

    International Nuclear Information System (INIS)

    Duan, Wei-Long

    2013-01-01

    The revised role of the time delay of active processes with colored noises of transmission of intracellular Ca 2+ in intracellular calcium oscillation (ICO) is investigated by means of a first-order algorithm based on stochastic simulation. The simulation results indicate that time delay induces a double critical phenomenon and a transition between the monostable and bistable states of the ICO system. In addition, as the time delay increases, for a cytosolic Ca 2+ concentration with weak colored noises there appears a calcium burst, and the Ca 2+ concentration of the calcium store shows nonmonotonic variation. (paper)

  18. Second-order differential-delay equation to describe a hybrid bistable device

    Science.gov (United States)

    Vallee, R.; Dubois, P.; Cote, M.; Delisle, C.

    1987-08-01

    The problem of a dynamical system with delayed feedback, a hybrid bistable device, characterized by n response times and described by an nth-order differential-delay equation (DDE) is discussed. Starting from a linear-stability analysis of the DDE, the effects of the second-order differential terms on the position of the first bifurcation and on the frequency of the resulting self-oscillation are shown. The effects of the third-order differential terms on the first bifurcation are also considered. Experimental results are shown to support the linear analysis.

  19. Noise-induced coherence in bistable systems with multiple time delays

    International Nuclear Information System (INIS)

    Jiang Yu; Dong, Shi-Hai; Lozada-Cassou, M.

    2004-01-01

    We study the correlation properties of noise-driven bistable systems with multiple time-delay feedbacks. For small noisy perturbation and feedback magnitude, we derive the autocorrelation function and the power spectrum based on the two-state model with transition rates depending on the earlier states of the system. A comparison between the single and double time delays reveals that the auto correlation functions exhibit exponential decay with small undulation for the double time delays, in contrast with the remarkable oscillatory behavior at small time lags for the single time delay

  20. Kinetic evaluation of photosensitivity in bi-stable variants of chimeric channelrhodopsins.

    Directory of Open Access Journals (Sweden)

    Shoko Hososhima

    Full Text Available Channelrhodopsin-1 and 2 (ChR1 and ChR2 form cation channels that are gated by light through an unknown mechanism. We tested the DC-gate hypothesis that C167 and D195 are involved in the stabilization of the cation-permeable state of ChRWR/C1C2 which consists of TM1-5 of ChR1 and TM6-7 of ChR2 and ChRFR which consists of TM1-2 of ChR1 and TM3-7 of ChR2. The cation permeable state of each ChRWR and ChRFR was markedly prolonged in the order of several tens of seconds when either C167 or D195 position was mutated to alanine (A. Therefore, the DC-gate function was conserved among these chimeric ChRs. We next investigated the kinetic properties of the ON/OFF response of these bi-stable ChR mutants as they are important in designing the photostimulation protocols for the optogenetic manipulation of neuronal activities. The turning-on rate constant of each photocurrent followed a linear relationship to 0-0.12 mW mm(-2 of blue LED light or to 0-0.33 mW mm(-2 of cyan LED light. Each photocurrent of bi-stable ChR was shut off to the non-conducting state by yellow or orange LED light in a manner dependent on the irradiance. As the magnitude of the photocurrent was mostly determined by the turning-on rate constant and the irradiation time, the minimal irradiance that effectively evoked an action potential (threshold irradiance was decreased with time only if the neuron, which expresses bi-stable ChRs, has a certain large membrane time constant (eg. τm > 20 ms. On the other hand, in another group of neurons, the threshold irradiance was not dependent on the irradiation time. Based on these quantitative data, we would propose that these bi-stable ChRs would be most suitable for enhancing the intrinsic activity of excitatory pyramidal neurons at a minimal magnitude of irradiance.

  1. Method and apparatus for bistable optical information storage for erasable optical disks

    Science.gov (United States)

    Land, Cecil E.; McKinney, Ira D.

    1990-01-01

    A method and an optical device for bistable storage of optical information, together with reading and erasure of the optical information, using a photoactivated shift in a field dependent phase transition between a metastable or a bias-stabilized ferroelectric (FE) phase and a stable antiferroelectric (AFE) phase in an lead lanthanum zirconate titanate (PLZT). An optical disk contains the PLZT. Writing and erasing of optical information can be accomplished by a light beam normal to the disk. Reading of optical information can be accomplished by a light beam at an incidence angle of 15 to 60 degrees to the normal of the disk.

  2. Modeling bistable cell-fate choices in the Drosophila eye: qualitative and quantitative perspectives

    Science.gov (United States)

    Graham, Thomas G. W.; Tabei, S. M. Ali; Dinner, Aaron R.; Rebay, Ilaria

    2010-01-01

    A major goal of developmental biology is to understand the molecular mechanisms whereby genetic signaling networks establish and maintain distinct cell types within multicellular organisms. Here, we review cell-fate decisions in the developing eye of Drosophila melanogaster and the experimental results that have revealed the topology of the underlying signaling circuitries. We then propose that switch-like network motifs based on positive feedback play a central role in cell-fate choice, and discuss how mathematical modeling can be used to understand and predict the bistable or multistable behavior of such networks. PMID:20570936

  3. Memristic Characteristics from Bistable to Tristable Memory with Controllable Charge Trap Carbon Nanotubes.

    Science.gov (United States)

    Li, Lei; Wen, Dianzhong

    2018-02-17

    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. This study will be useful for the development and tuning of multi-bit storable organic nanocomposite memory device systems.

  4. Memristic Characteristics from Bistable to Tristable Memory with Controllable Charge Trap Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Lei Li

    2018-02-01

    Full Text Available 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. This study will be useful for the development and tuning of multi-bit storable organic nanocomposite memory device systems.

  5. Bistable states of TM polarized non-linear waves guided by symmetric layered structures

    International Nuclear Information System (INIS)

    Mihalache, D.

    1985-04-01

    Dispersion relations for TM polarized non-linear waves propagating in a symmetric single film optical waveguide are derived. The system consists of a layer of thickness d with dielectric constant epsilon 1 bounded at two sides by a non-linear medium characterized by the diagonal dielectric tensor epsilon 11 =epsilon 22 =epsilon 0 , epsilon 33 =epsilon 0 +α|E 3 | 2 , where E 3 is the normal electric field component. For sufficiently large d/lambda (lambda is the wavelength) we predict bistable states of both symmetric and antisymmetric modes provided that the power flow is the control parameter. (author)

  6. Bistable Bacterial Growth Rate in Response to Antibiotics with Low Membrane Permeability

    Science.gov (United States)

    Elf, Johan; Nilsson, Karin; Tenson, Tanel; Ehrenberg, Måns

    2006-12-01

    We demonstrate that growth rate bistability for bacterial cells growing exponentially at a fixed external antibiotic concentration can emerge when the cell wall permeability for the drug is low and the growth rate sensitivity to the intracellular drug concentration is high. Under such conditions, an initially high growth rate can remain high, due to dilution of the intracellular drug concentration by rapid cell volume increase, while an initially low growth rate can remain low, due to slow cell volume increase and insignificant drug dilution. Our findings have implications for the testing of novel antibiotics on growing bacterial strains.

  7. Bistability, electric potentials and sensor behaviour in an enzymatic reaction system

    International Nuclear Information System (INIS)

    Malchow, H.; Felber, F.

    1987-07-01

    A special ionic enzyme kinetics in a continuously stirred flow reactor which is membrane coupled to a reservoir is considered starting from a general expression for the substrate dependence of enzymatic reaction rates including pH effects. Both bistability of the reaction and electric potentials between the interior and exterior of the reactor can be observed having regard to mass and charge conservation as well as global electroneutrality. The sudden jumps at critical concentration values from one stable solution branch to the other on a hysteresis loop are supposed to be the basic action principle of a non-equilibrium concentration threshold sensor. (author). 38 refs, 3 figs

  8. Bistability, multistability and non-reciprocal light propagation in Thue-Morse multilayered structures

    International Nuclear Information System (INIS)

    Grigoriev, Victor; Biancalana, Fabio

    2010-01-01

    The nonlinear properties of quasi-periodic photonic crystals based on the Thue-Morse sequence are investigated. The intrinsic spatial asymmetry of these one-dimensional structures for odd generation numbers results in bistability thresholds, which are sensitive to the propagation direction. Along with resonances of perfect transmission, this feature allows us to achieve strongly non-reciprocal propagation and to create an all-optical diode. The salient qualitative features of such optical diode action are readily explained through a simple coupled resonator model. The efficiency of a passive scheme that does not necessitate an additional short pump signal is compared to an active scheme where such a signal is required.

  9. Personal Reflections

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education. Personal Reflections. Articles in Resonance – Journal of Science Education. Volume 6 Issue 3 March 2001 pp 90-93 Personal Reflections. Why did I opt for Career in Science? Jayant V Narlikar · More Details Fulltext PDF. Volume 9 Issue 8 August 2004 pp 89-89 ...

  10. Reflection groups

    International Nuclear Information System (INIS)

    Eggermont, G.

    2006-01-01

    In 2005, PISA organised proactive meetings of reflection groups on involvement in decision making, expert culture and ethical aspects of radiation protection.All reflection group meetings address particular targeted audiences while the output publication in book form is put forward

  11. Reflection ciphers

    DEFF Research Database (Denmark)

    Boura, Christina; Canteaut, Anne; Knudsen, Lars Ramkilde

    2017-01-01

    study the necessary properties for this coupling permutation. Special care has to be taken of some related-key distinguishers since, in the context of reflection ciphers, they may provide attacks in the single-key setting.We then derive some criteria for constructing secure reflection ciphers...

  12. Quantifying Reflection

    DEFF Research Database (Denmark)

    Alcock, Gordon Lindsay

    2013-01-01

    ´ These are all based on Blooms taxonomy and levels of competence and form a major part of individual student and group learning portfolios. Key Words :Project-Based learning, Reflective Portfolios, Self assessment, Defining learning gains, Developing learning strategies , Reflections on and for learning....... It contrasts the students’ self-assessment in a range of ‘product’ skills such as Revit, Structural Design, Mathematics of construction, Technical Installations; as well as ‘process’ competencies such as ‘Working in a team’, Sharing knowledge, Maintaining a portfolio and Reflecting ON learning and FOR learning......This paper documents 1st semester student reflections on “learning to learn” in a team-based PBL environment with quantitative and qualitative student reflective feedback on the learning gains of 60 Architectural Technology and Construction Management students at VIA University College, Denmark...

  13. The theory of stability, bistability, and instability in three-mode class-A lasers

    International Nuclear Information System (INIS)

    Jahanpanah, J; Rahdar, A A

    2014-01-01

    Instability is an inevitable and common problem in all different kinds of lasers when they are oscillating in both single-and multi-mode states. Here, the stability conditions are investigated for a three-mode class-A laser. A set of linear equations is derived for the stable oscillation of the cavity central mode together with its left and right adjacent longitudinal modes. The coefficient determinant of stability equations is Hermitian and equal to zero for the roots of two diagonal arrays. In other words, the novelty of our work is to expand the stability coefficient determinant in terms of main diagonal arrays rather than for one row or one column. These diagonal roots lead to two lower and upper boundary curves in the form of a bifurcation. The lower boundary curve mimics the single-mode laser and delimits the instability region (with no above-threshold oscillating mode) from the bistability region (with two above-threshold oscillating modes). The upper boundary curve mimics the two-mode laser and delimits the bistability region from the stability region, in which all three-longitudinal modes are simultaneously oscillating in the above-threshold state. (paper)

  14. Phase synchronization for two Brownian motors with bistable coupling on a ratchet

    International Nuclear Information System (INIS)

    Mateos, Jose L.; Alatriste, F.R.

    2010-01-01

    Graphical abstract: We study phase synchronization for a walker with two Brownian motors with bistable coupling on a ratchet and show a connection between synchronization and optimal transport. - Abstract: We study phase synchronization for a walker on a ratchet potential. The walker consist of two particles coupled by a bistable potential that allow the interchange of the order of the particles while moving through a one-dimensional asymmetric periodic ratchet potential. We consider the deterministic and the stochastic dynamics of the center of mass of the walker in a tilted ratchet potential with an external periodic forcing, in the overdamped case. The ratchet potential has to be tilted in order to obtain a rotator or self-sustained nonlinear oscillator in the absence of external periodic forcing. This oscillator has an intrinsic frequency that can be entrained with the frequency of the external driving. We introduced a linear phase through a set of discrete time events and the associated average frequency, and show that this frequency can be synchronized with the frequency of the external driving. In this way, we can properly characterize the phenomenon of synchronization through Arnold tongues and show that the local maxima in the average velocity of the center of mass of the walker, both in the deterministic case and in the presence of noise, correspond to the borders of these Arnold tongues. In this way, we established a connection between optimal transport in ratchets and the phenomenon of phase synchronization.

  15. Flytrap-inspired robot using structurally integrated actuation based on bistability and a developable surface.

    Science.gov (United States)

    Kim, Seung-Won; Koh, Je-Sung; Lee, Jong-Gu; Ryu, Junghyun; Cho, Maenghyo; Cho, Kyu-Jin

    2014-09-01

    The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m(-1) within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position.

  16. Bi-stability in cooperative transport by ants in the presence of obstacles.

    Directory of Open Access Journals (Sweden)

    Jonathan E Ron

    2018-05-01

    Full Text Available To cooperatively carry large food items to the nest, individual ants conform their efforts and coordinate their motion. Throughout this expedition, collective motion is driven both by internal interactions between the carrying ants and a response to newly arrived informed ants that orient the cargo towards the nest. During the transport process, the carrying group must overcome obstacles that block their path to the nest. Here, we investigate the dynamics of cooperative transport, when the motion of the ants is frustrated by a linear obstacle that obstructs the motion of the cargo. The obstacle contains a narrow opening that serves as the only available passage to the nest, and through which single ants can pass but not with the cargo. We provide an analytical model for the ant-cargo system in the constrained environment that predicts a bi-stable dynamic behavior between an oscillatory mode of motion along the obstacle and a convergent mode of motion near the opening. Using both experiments and simulations, we show how for small cargo sizes, the system exhibits spontaneous transitions between these two modes of motion due to fluctuations in the applied force on the cargo. The bi-stability provides two possible problem solving strategies for overcoming the obstacle, either by attempting to pass through the opening, or take large excursions to circumvent the obstacle.

  17. Bio-inspired structural bistability employing elastomeric origami for morphing applications

    International Nuclear Information System (INIS)

    Daynes, Stephen; Trask, Richard S; Weaver, Paul M

    2014-01-01

    A structural concept based upon the principles of adaptive morphing cells is presented whereby controlled bistability from a flat configuration into a textured arrangement is shown. The material consists of multiple cells made from silicone rubber with locally reinforced regions based upon kirigami principles. On pneumatic actuation these cells fold or unfold based on the fold lines created by the interaction of the geometry with the reinforced regions. Each cell is able to maintain its shape in either a retracted or deployed state, without the aid of mechanisms or sustained actuation, due to the existence of structural bistability. Mathematical quantification of the surface texture is introduced, based on out-of-plane deviations of a deployed structure compared to a reference plane. Additionally, finite element analysis is employed to characterize the geometry and stability of an individual cell during actuation and retraction. This investigation highlights the critical role that angular rotation, at the center of each cell, plays on the deployment angle as it transitions through the elastically deployed configuration. The analysis of this novel concept is presented and a pneumatically actuated proof-of-concept demonstrator is fabricated. (paper)

  18. Bio-inspired structural bistability employing elastomeric origami for morphing applications

    Science.gov (United States)

    Daynes, Stephen; Trask, Richard S.; Weaver, Paul M.

    2014-12-01

    A structural concept based upon the principles of adaptive morphing cells is presented whereby controlled bistability from a flat configuration into a textured arrangement is shown. The material consists of multiple cells made from silicone rubber with locally reinforced regions based upon kirigami principles. On pneumatic actuation these cells fold or unfold based on the fold lines created by the interaction of the geometry with the reinforced regions. Each cell is able to maintain its shape in either a retracted or deployed state, without the aid of mechanisms or sustained actuation, due to the existence of structural bistability. Mathematical quantification of the surface texture is introduced, based on out-of-plane deviations of a deployed structure compared to a reference plane. Additionally, finite element analysis is employed to characterize the geometry and stability of an individual cell during actuation and retraction. This investigation highlights the critical role that angular rotation, at the center of each cell, plays on the deployment angle as it transitions through the elastically deployed configuration. The analysis of this novel concept is presented and a pneumatically actuated proof-of-concept demonstrator is fabricated.

  19. Understanding bistability in yeast glycolysis using general properties of metabolic pathways.

    Science.gov (United States)

    Planqué, Robert; Bruggeman, Frank J; Teusink, Bas; Hulshof, Josephus

    2014-09-01

    Glycolysis is the central pathway in energy metabolism in the majority of organisms. In a recent paper, van Heerden et al. showed experimentally and computationally that glycolysis can exist in two states, a global steady state and a so-called imbalanced state. In the imbalanced state, intermediary metabolites accumulate at low levels of ATP and inorganic phosphate. It was shown that Baker's yeast uses a peculiar regulatory mechanism--via trehalose metabolism--to ensure that most yeast cells reach the steady state and not the imbalanced state. Here we explore the apparent bistable behaviour in a core model of glycolysis that is based on a well-established detailed model, and study in great detail the bifurcation behaviour of solutions, without using any numerical information on parameter values. We uncover a rich suite of solutions, including so-called imbalanced states, bistability, and oscillatory behaviour. The techniques employed are generic, directly suitable for a wide class of biochemical pathways, and could lead to better analytical treatments of more detailed models. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Amplification without inversion, fast light and optical bistability in a duplicated two-level system

    International Nuclear Information System (INIS)

    Ebrahimi Zohravi, Lida; Vafafard, Azar; Mahmoudi, Mohammad

    2014-01-01

    The optical properties of a weak probe field in a duplicated two-level system are investigated in multi-photon resonance (MPR) condition and beyond it. It is shown that by changing the relative phase of applied fields, the absorption switches to the amplification without inversion in MPR condition. By applying the Floquet decomposition to the equations of motion beyond MPR condition, it is shown that the phase-dependent behavior is valid only in MPR condition. Moreover, it is demonstrated that the group velocity of light pulse can be controlled by the intensity of the applied fields and the gain-assisted superluminal light propagation (fast light) is obtained in this system. In addition, the optical bistability (OB) behavior of the system is studied beyond MPR condition. We apply an indirect incoherent pumping field to the system and it is found that the group velocity and OB behavior of the system can be controlled by the incoherent pumping rate. - Highlights: • We studied the optical properties of DTL system under MPR condition and beyond it. • By changing the relative phase, the absorption switches to the amplification without inversion in MPR condition. • The gain-assisted superluminal light propagation (fast light) is obtained in this system. • The optical bistability (OB) behavior of the system is studied beyond MPR condition. • The incoherent pumping rate has a major role in controlling the group velocity and OB behavior of the system

  1. BRIEF COMMUNICATION: Electrothermal bistability tuning in a large displacement micro actuator

    Science.gov (United States)

    Gerson, Y.; Krylov, S.; Ilic, B.

    2010-11-01

    We report on an approach allowing simple yet efficient tuning of the bistability properties in large displacement micro actuators. The devices fabricated from silicon on insulator (SOI) wafers using a deep reactive ion etching (DRIE)-based process incorporate elastic suspension realized as a pair of beams initially curved in-plane and are operated electrostatically by a comb-drive transducer. The curvature of beam and therefore the stability characteristics of the suspension are controlled by passing a current through the suspension and resistive heating the beam material. Experimental results, which are in good agreement with the finite elements model predictions, demonstrate the feasibility of the suggested approach and show that the application of a small tuning current increases the device deflection from 42 to 56 µm, allows adjustment of the critical snap-through and snap-back voltages and makes it possible the control of latching without an additional electrode. The approach can be efficiently implemented in electrical and optical switches and threshold inertial and mass sensors where the use of long displacement actuators with an adjustable bistability range is beneficial.

  2. The limiting dynamics of a bistable molecular switch with and without noise.

    Science.gov (United States)

    Mackey, Michael C; Tyran-Kamińska, Marta

    2016-08-01

    We consider the dynamics of a population of organisms containing two mutually inhibitory gene regulatory networks, that can result in a bistable switch-like behaviour. We completely characterize their local and global dynamics in the absence of any noise, and then go on to consider the effects of either noise coming from bursting (transcription or translation), or Gaussian noise in molecular degradation rates when there is a dominant slow variable in the system. We show analytically how the steady state distribution in the population can range from a single unimodal distribution through a bimodal distribution and give the explicit analytic form for the invariant stationary density which is globally asymptotically stable. Rather remarkably, the behaviour of the stationary density with respect to the parameters characterizing the molecular behaviour of the bistable switch is qualitatively identical in the presence of noise coming from bursting as well as in the presence of Gaussian noise in the degradation rate. This implies that one cannot distinguish between either the dominant source or nature of noise based on the stationary molecular distribution in a population of cells. We finally show that the switch model with bursting but two dominant slow genes has an asymptotically stable stationary density.

  3. EEG correlates of cognitive time scales in the Necker-Zeno model for bistable perception.

    Science.gov (United States)

    Kornmeier, J; Friedel, E; Wittmann, M; Atmanspacher, H

    2017-08-01

    The Necker-Zeno model of bistable perception provides a formal relation between the average duration of meta-stable percepts (dwell times T) of ambiguous figures and two other basic time scales (t 0 , ΔT) underlying cognitive processing. The model predicts that dwell times T covary with t 0 , ΔT or both. We tested this prediction by exploiting that observers, in particular experienced meditators, can volitionally control dwell times T. Meditators and non-meditators observed bistable Necker cubes either passively or tried to hold their current percept. The latencies of a centro-parietal event-related potential (CPP) were recorded as a physiological correlate of t 0 . Dwell times T and the CPP latencies, correlated with t 0 , differed between conditions and observer groups, while ΔT remained constant in the range predicted by the model. The covariation of CPP latencies and dwell times, as well as their quadratic functional dependence extends previous psychophysical confirmation of the Necker-Zeno model to psychophysiological measures. Copyright © 2017. Published by Elsevier Inc.

  4. Phase-dependent dynamic potential of magnetically coupled two-degree-of-freedom bistable energy harvester.

    Science.gov (United States)

    Kim, Pilkee; Nguyen, Minh Sang; Kwon, Ojin; Kim, Young-Jin; Yoon, Yong-Jin

    2016-09-28

    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. Through theoretical simulations and analyses, two distinct dynamic regimes, called the out-of-phase and in-phase mode regimes in this report, are found to exist in the frequency regions of the 1 st and 2 nd primary intrawell resonances. For the out-of-phase mode regime, the frequency displacement (and output power) responses of the 2-DOF BEH system exhibit typical double-well dynamics, whereas for the in-phase mode regime, only single-well dynamics is observed though the system is statically bistable. These dynamic regimes are also revealed to be caused by the difference in the dynamic potential energy trajectories propagating on a high-dimensional potential energy surface. The present approach to the dynamics of the 2-DOF BEH system can be extended and applied to higher-DOF systems, which sheds light on compact and efficient designs of magnetically coupled BEH chain structures.

  5. Coupled Reversible and Irreversible Bistable Switches Underlying TGFβ-induced Epithelial to Mesenchymal Transition

    Science.gov (United States)

    Tian, Xiao-Jun; Zhang, Hang; Xing, Jianhua

    2013-01-01

    Epithelial to mesenchymal transition (EMT) plays an important role in embryonic development, tissue regeneration, and cancer metastasis. Whereas several feedback loops have been shown to regulate EMT, it remains elusive how they coordinately modulate EMT response to TGF-β treatment. We construct a mathematical model for the core regulatory network controlling TGF-β-induced EMT. Through deterministic analyses and stochastic simulations, we show that EMT is a sequential two-step program in which an epithelial cell first is converted to partial EMT then to the mesenchymal state, depending on the strength and duration of TGF-β stimulation. Mechanistically the system is governed by coupled reversible and irreversible bistable switches. The SNAIL1/miR-34 double-negative feedback loop is responsible for the reversible switch and regulates the initiation of EMT, whereas the ZEB/miR-200 feedback loop is accountable for the irreversible switch and controls the establishment of the mesenchymal state. Furthermore, an autocrine TGF-β/miR-200 feedback loop makes the second switch irreversible, modulating the maintenance of EMT. Such coupled bistable switches are robust to parameter variation and molecular noise. We provide a mechanistic explanation on multiple experimental observations. The model makes several explicit predictions on hysteretic dynamic behaviors, system response to pulsed stimulation, and various perturbations, which can be straightforwardly tested. PMID:23972859

  6. Bistable Epigenetic States Explain Age-Dependent Decline in Mesenchymal Stem Cell Heterogeneity.

    Science.gov (United States)

    Hamidouche, Zahia; Rother, Karen; Przybilla, Jens; Krinner, Axel; Clay, Denis; Hopp, Lydia; Fabian, Claire; Stolzing, Alexandra; Binder, Hans; Charbord, Pierre; Galle, Joerg

    2017-03-01

    The molecular mechanisms by which heterogeneity, a major characteristic of stem cells, is achieved are yet unclear. We here study the expression of the membrane stem cell antigen-1 (Sca-1) in mouse bone marrow mesenchymal stem cell (MSC) clones. We show that subpopulations with varying Sca-1 expression profiles regenerate the Sca-1 profile of the mother population within a few days. However, after extensive replication in vitro, the expression profiles shift to lower values and the regeneration time increases. Study of the promoter of Ly6a unravels that the expression level of Sca-1 is related to the promoter occupancy by the activating histone mark H3K4me3. We demonstrate that these findings can be consistently explained by a computational model that considers positive feedback between promoter H3K4me3 modification and gene transcription. This feedback implicates bistable epigenetic states which the cells occupy with an age-dependent frequency due to persistent histone (de-)modification. Our results provide evidence that MSC heterogeneity, and presumably that of other stem cells, is associated with bistable epigenetic states and suggest that MSCs are subject to permanent state fluctuations. Stem Cells 2017;35:694-704. © The Authors Stem Cells published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.

  7. Bridging time scales in cellular decision making with a stochastic bistable switch

    Directory of Open Access Journals (Sweden)

    Waldherr Steffen

    2010-08-01

    Full Text Available Abstract Background Cellular transformations which involve a significant phenotypical change of the cell's state use bistable biochemical switches as underlying decision systems. Some of these transformations act over a very long time scale on the cell population level, up to the entire lifespan of the organism. Results In this work, we aim at linking cellular decisions taking place on a time scale of years to decades with the biochemical dynamics in signal transduction and gene regulation, occuring on a time scale of minutes to hours. We show that a stochastic bistable switch forms a viable biochemical mechanism to implement decision processes on long time scales. As a case study, the mechanism is applied to model the initiation of follicle growth in mammalian ovaries, where the physiological time scale of follicle pool depletion is on the order of the organism's lifespan. We construct a simple mathematical model for this process based on experimental evidence for the involved genetic mechanisms. Conclusions Despite the underlying stochasticity, the proposed mechanism turns out to yield reliable behavior in large populations of cells subject to the considered decision process. Our model explains how the physiological time constant may emerge from the intrinsic stochasticity of the underlying gene regulatory network. Apart from ovarian follicles, the proposed mechanism may also be of relevance for other physiological systems where cells take binary decisions over a long time scale.

  8. Bistable direction switching in an off-axis pumped continuous wave ruby laser

    Science.gov (United States)

    Afzal, R. Sohrab; Lawandy, N. M.

    1988-01-01

    A report is presented of the observation of hysteretic bistable direction switching in a single-mode CW ruby laser system. This effect is only observed when the pump beam which is focused into the ruby rod is misaligned with respect to the rod end faces. At low pump powers, the ruby lases in a mode nearly collinear with the pump axis. At a higher pump power the ruby switches to a mode that is collinear with the rod end faces and preserves the original polarization. The effect is large enough to switch the beam by an angle equal to twice the diffraction angle. The observations show that under steady-state pumping, a CW ruby laser can exhibit bistable operation in its output direction and power. A calculation using the heat equation with two concentric cylinders with one as a heat source (pump laser) and the outer wall of the other held at 77 K, gives an increase in core temperature of about 0.01 K. Therefore, the increase in temperature is not large enough to change the index of refraction to account for such large macroscopic effects.

  9. Flytrap-inspired robot using structurally integrated actuation based on bistability and a developable surface

    International Nuclear Information System (INIS)

    Kim, Seung-Won; Koh, Je-Sung; Cho, Kyu-Jin; Lee, Jong-Gu; Ryu, Junghyun; Cho, Maenghyo

    2014-01-01

    The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m −1  within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position. (paper)

  10. Confinement and diffusion modulate bistability and stochastic switching in a reaction network with positive feedback

    International Nuclear Information System (INIS)

    Mlynarczyk, Paul J.; Pullen, Robert H.; Abel, Steven M.

    2016-01-01

    Positive feedback is a common feature in signal transduction networks and can lead to phenomena such as bistability and signal propagation by domain growth. Physical features of the cellular environment, such as spatial confinement and the mobility of proteins, play important but inadequately understood roles in shaping the behavior of signaling networks. Here, we use stochastic, spatially resolved kinetic Monte Carlo simulations to explore a positive feedback network as a function of system size, system shape, and mobility of molecules. We show that these physical properties can markedly alter characteristics of bistability and stochastic switching when compared with well-mixed simulations. Notably, systems of equal volume but different shapes can exhibit qualitatively different behaviors under otherwise identical conditions. We show that stochastic switching to a state maintained by positive feedback occurs by cluster formation and growth. Additionally, the frequency at which switching occurs depends nontrivially on the diffusion coefficient, which can promote or suppress switching relative to the well-mixed limit. Taken together, the results provide a framework for understanding how confinement and protein mobility influence emergent features of the positive feedback network by modulating molecular concentrations, diffusion-influenced rate parameters, and spatiotemporal correlations between molecules

  11. An analytical approach for predicting the energy capture and conversion by impulsively-excited bistable vibration energy harvesters

    Science.gov (United States)

    Harne, R. L.; Zhang, Chunlin; Li, Bing; Wang, K. W.

    2016-07-01

    Impulsive energies are abundant throughout the natural and built environments, for instance as stimulated by wind gusts, foot-steps, or vehicle-road interactions. In the interest of maximizing the sustainability of society's technological developments, one idea is to capture these high-amplitude and abrupt energies and convert them into usable electrical power such as for sensors which otherwise rely on less sustainable power supplies. In this spirit, the considerable sensitivity to impulse-type events previously uncovered for bistable oscillators has motivated recent experimental and numerical studies on the power generation performance of bistable vibration energy harvesters. To lead to an effective and efficient predictive tool and design guide, this research develops a new analytical approach to estimate the electroelastic response and power generation of a bistable energy harvester when excited by an impulse. Comparison with values determined by direct simulation of the governing equations shows that the analytically predicted net converted energies are very accurate for a wide range of impulse strengths. Extensive experimental investigations are undertaken to validate the analytical approach and it is seen that the predicted estimates of the impulsive energy conversion are in excellent agreement with the measurements, and the detailed structural dynamics are correctly reproduced. As a result, the analytical approach represents a significant leap forward in the understanding of how to effectively leverage bistable structures as energy harvesting devices and introduces new means to elucidate the transient and far-from-equilibrium dynamics of nonlinear systems more generally.

  12. All-polymer bistable resistive memory device based on nanoscale phase-separated PCBM-ferroelectric blends

    KAUST Repository

    Khan, Yasser; Bhansali, Unnat Sampatraj; Cha, Dong Kyu; Alshareef, Husam N.

    2012-01-01

    All polymer nonvolatile bistable memory devices are fabricated from blends of ferroelectric poly(vinylidenefluoride-trifluoroethylene (P(VDF-TrFE)) and n-type semiconducting [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The nanoscale phase

  13. The effects of intrinsic noise on the behaviour of bistable cell regulatory systems under quasi-steady state conditions.

    Science.gov (United States)

    de la Cruz, Roberto; Guerrero, Pilar; Spill, Fabian; Alarcón, Tomás

    2015-08-21

    We analyse the effect of intrinsic fluctuations on the properties of bistable stochastic systems with time scale separation operating under quasi-steady state conditions. We first formulate a stochastic generalisation of the quasi-steady state approximation based on the semi-classical approximation of the partial differential equation for the generating function associated with the chemical master equation. Such approximation proceeds by optimising an action functional whose associated set of Euler-Lagrange (Hamilton) equations provides the most likely fluctuation path. We show that, under appropriate conditions granting time scale separation, the Hamiltonian can be re-scaled so that the set of Hamilton equations splits up into slow and fast variables, whereby the quasi-steady state approximation can be applied. We analyse two particular examples of systems whose mean-field limit has been shown to exhibit bi-stability: an enzyme-catalysed system of two mutually inhibitory proteins and a gene regulatory circuit with self-activation. Our theory establishes that the number of molecules of the conserved species is order parameters whose variation regulates bistable behaviour in the associated systems beyond the predictions of the mean-field theory. This prediction is fully confirmed by direct numerical simulations using the stochastic simulation algorithm. This result allows us to propose strategies whereby, by varying the number of molecules of the three conserved chemical species, cell properties associated to bistable behaviour (phenotype, cell-cycle status, etc.) can be controlled.

  14. Numerical analysis of intrinsic bistability and chromatic switching in Tm3+ single-doped systems under photon avalanche pumping scheme

    International Nuclear Information System (INIS)

    Li Li; Zhang Xinlu; Chen Lixue

    2008-01-01

    In this paper, we predict and numerically demonstrate the intrinsic intensity bistability, spectra bistability and chromatic switching of visible-infrared emission in Tm 3+ single-doped systems that are pumped by the photon avalanche scheme at 648 nm. Based on the coupled rate equation theory, the evolutions of the populations at various Tm 3+ energy levels, emission spectra and fluorescence intensity versus pump excitation are numerically investigated in detail. The results show that intrinsic optical bistability (IOB) associated with emission spectra and luminescence intensity takes place in the vicinity of the avalanche threshold (∼10 kW cm -2 ). When the pump excitation rises above the switching threshold (∼17.5 kW cm -2 ), the chromatic switching between the infrared (1716 nm) and the visible blue (452/469 nm) spectra can be performed. Moreover, the influences of system parameters on IOB and the origin of chromatic switching are discussed. These unique characteristics of Tm 3+ -doped systems would lead to the new possibility of the development of pump-controlled all-solid-state luminescence switches and optical bistability switches.

  15. A statically balanced and bi-stable compliant end effector combined with a laparoscopic 2DoF robotic arm

    NARCIS (Netherlands)

    Lassooij, J.; Tolou, N.; Tortora, G.; Caccavaro, S.; Menciassi, A.; Herder, J.L.

    2012-01-01

    This article presents the design of a newly developed 2DoF robotic arm with a novel statically balanced and bi-stable compliant grasper as the end effector for laparoscopic surgery application. The arm is based on internal motors actuating 2 rotational DoFs: pitch and roll. The positive stiffness of

  16. The effects of intrinsic noise on the behaviour of bistable cell regulatory systems under quasi-steady state conditions

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, Roberto; Alarcón, Tomás de la [Centre de Recerca Matemàtica. Edifici C, Campus de Bellaterra, 08193 Bellaterra (Barcelona) (Spain); Departament de Matemàtiques, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain); Guerrero, Pilar [Department of Mathematics, University College London, Gower Street, London WC1E 6BT (United Kingdom); Spill, Fabian [Department of Biomedical Engineering, Boston University, 44 Cummington Street, Boston, Massachusetts 02215 (United States); Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States)

    2015-08-21

    We analyse the effect of intrinsic fluctuations on the properties of bistable stochastic systems with time scale separation operating under quasi-steady state conditions. We first formulate a stochastic generalisation of the quasi-steady state approximation based on the semi-classical approximation of the partial differential equation for the generating function associated with the chemical master equation. Such approximation proceeds by optimising an action functional whose associated set of Euler-Lagrange (Hamilton) equations provides the most likely fluctuation path. We show that, under appropriate conditions granting time scale separation, the Hamiltonian can be re-scaled so that the set of Hamilton equations splits up into slow and fast variables, whereby the quasi-steady state approximation can be applied. We analyse two particular examples of systems whose mean-field limit has been shown to exhibit bi-stability: an enzyme-catalysed system of two mutually inhibitory proteins and a gene regulatory circuit with self-activation. Our theory establishes that the number of molecules of the conserved species is order parameters whose variation regulates bistable behaviour in the associated systems beyond the predictions of the mean-field theory. This prediction is fully confirmed by direct numerical simulations using the stochastic simulation algorithm. This result allows us to propose strategies whereby, by varying the number of molecules of the three conserved chemical species, cell properties associated to bistable behaviour (phenotype, cell-cycle status, etc.) can be controlled.

  17. Study of thermally-induced optical bistability and the role of surface treatments in Si-based mid-infrared photonic crystal cavities.

    Science.gov (United States)

    Shankar, Raji; Bulu, Irfan; Leijssen, Rick; Lončar, Marko

    2011-11-21

    We report the observation of optical bistability in Si-based photonic crystal cavities operating around 4.5 µm. Time domain measurements indicate that the source of this optical bistability is thermal, with a time constant on the order of 5 µs. Quality (Q) factor improvement is shown by the use of surface treatments (wet processes and annealing), resulting in a significant increase in Q-factor, which in our best devices is on the order of ~45,000 at 4.48 µm. After annealing in a N(2) environment, optical bistability is no longer seen in our cavities. © 2011 Optical Society of America

  18. Bistability and hysteresis of the 'Secteur' differentiation are controlled by a two-gene locus in Nectria haematococca

    Directory of Open Access Journals (Sweden)

    Daboussi Marie-Josée

    2004-08-01

    Full Text Available Abstract Background Bistability and hysteresis are increasingly recognized as major properties of regulatory networks governing numerous biological phenomena, such as differentiation and cell cycle progression. The full scope of the underlying molecular mechanisms leading to bistability and hysteresis remains elusive. Nectria haemaotcocca, a saprophytic or pathogenic fungus with sexual reproduction, exhibits a bistable morphological modification characterized by a reduced growth rate and an intense pigmentation. Bistability is triggered by the presence or absence of σ, a cytoplasmic determinant. This determinant spreads in an infectious manner in the hyphae of the growing margin, insuring hysteresis of the differentiation. Results Seven mutants specifically affected in the generation of σ were selected through two different screening strategies. The s1 and s2 mutations completely abolish the generation of σ and of its morphological expression, the Secteur. The remaining five mutations promote its constitutive generation, which determines an intense pigmentation but not growth alteration. The seven mutations map at the same locus, Ses (for 'Secteur-specific'. The s2 mutant was obtained by an insertional mutagenesis strategy, which permitted the cloning of the Ses locus. Sequence and transcription analysis reveals that Ses is composed of two closely linked genes, SesA, mutated in the s1 and s2 mutant strains, and SesB, mutated in the s* mutant strains. SesB shares sequence similarity with animal and fungal putative proteins, with potential esterase/lipase/thioesterase activity, whereas SesA is similar to proteins of unknown function present only in the filamentous fungi Fusarium graminearum and Podospora anserina. Conclusions The cloning of Ses provides evidence that a system encoded by two linked genes directs a bistable and hysteretic switch in a eukaryote. Atypical regulatory relations between the two proteins may account for the hysteresis

  19. Bistability and hysteresis of the 'Secteur' differentiation are controlled by a two-gene locus in Nectria haematococca

    Science.gov (United States)

    Graziani, Stéphane; Silar, Philippe; Daboussi, Marie-Josée

    2004-01-01

    Background Bistability and hysteresis are increasingly recognized as major properties of regulatory networks governing numerous biological phenomena, such as differentiation and cell cycle progression. The full scope of the underlying molecular mechanisms leading to bistability and hysteresis remains elusive. Nectria haemaotcocca, a saprophytic or pathogenic fungus with sexual reproduction, exhibits a bistable morphological modification characterized by a reduced growth rate and an intense pigmentation. Bistability is triggered by the presence or absence of σ, a cytoplasmic determinant. This determinant spreads in an infectious manner in the hyphae of the growing margin, insuring hysteresis of the differentiation. Results Seven mutants specifically affected in the generation of σ were selected through two different screening strategies. The s1 and s2 mutations completely abolish the generation of σ and of its morphological expression, the Secteur. The remaining five mutations promote its constitutive generation, which determines an intense pigmentation but not growth alteration. The seven mutations map at the same locus, Ses (for 'Secteur-specific'). The s2 mutant was obtained by an insertional mutagenesis strategy, which permitted the cloning of the Ses locus. Sequence and transcription analysis reveals that Ses is composed of two closely linked genes, SesA, mutated in the s1 and s2 mutant strains, and SesB, mutated in the s* mutant strains. SesB shares sequence similarity with animal and fungal putative proteins, with potential esterase/lipase/thioesterase activity, whereas SesA is similar to proteins of unknown function present only in the filamentous fungi Fusarium graminearum and Podospora anserina. Conclusions The cloning of Ses provides evidence that a system encoded by two linked genes directs a bistable and hysteretic switch in a eukaryote. Atypical regulatory relations between the two proteins may account for the hysteresis of Secteur differentiation

  20. Measurement of the ground-state distributions in bistable mechanically interlocked molecules using slow scan rate cyclic voltammetry.

    Science.gov (United States)

    Fahrenbach, Albert C; Barnes, Jonathan C; Li, Hao; Benítez, Diego; Basuray, Ashish N; Fang, Lei; Sue, Chi-Hau; Barin, Gokhan; Dey, Sanjeev K; Goddard, William A; Stoddart, J Fraser

    2011-12-20

    In donor-acceptor mechanically interlocked molecules that exhibit bistability, the relative populations of the translational isomers--present, for example, in a bistable [2]rotaxane, as well as in a couple of bistable [2]catenanes of the donor-acceptor vintage--can be elucidated by slow scan rate cyclic voltammetry. The practice of transitioning from a fast scan rate regime to a slow one permits the measurement of an intermediate redox couple that is a function of the equilibrium that exists between the two translational isomers in the case of all three mechanically interlocked molecules investigated. These intermediate redox potentials can be used to calculate the ground-state distribution constants, K. Whereas, (i) in the case of the bistable [2]rotaxane, composed of a dumbbell component containing π-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two π-electron-deficient bipyridinium units), a value for K of 10 ± 2 is calculated, (ii) in the case of the two bistable [2]catenanes--one containing a crown ether with tetrathiafulvalene and dioxynaphthalene recognition sites for the tetracationic cyclophane, and the other, tetrathiafulvalene and butadiyne recognition sites--the values for K are orders (one and three, respectively) of magnitude greater. This observation, which has also been probed by theoretical calculations, supports the hypothesis that the extra stability of one translational isomer over the other is because of the influence of the enforced side-on donor-acceptor interactions brought about by both π-electron-rich recognition sites being part of a macrocyclic polyether.

  1. Reflectance Modeling

    Science.gov (United States)

    Smith, J. A.; Cooper, K.; Randolph, M.

    1984-01-01

    A classical description of the one dimensional radiative transfer treatment of vegetation canopies was completed and the results were tested against measured prairie (blue grama) and agricultural canopies (soybean). Phase functions are calculated in terms of directly measurable biophysical characteristics of the canopy medium. While the phase functions tend to exhibit backscattering anisotropy, their exact behavior is somewhat more complex and wavelength dependent. A Monte Carlo model was developed that treats soil surfaces with large periodic variations in three dimensions. A photon-ray tracing technology is used. Currently, the rough soil surface is described by analytic functions and appropriate geometric calculations performed. A bidirectional reflectance distribution function is calculated and, hence, available for other atmospheric or canopy reflectance models as a lower boundary condition. This technique is used together with an adding model to calculate several cases where Lambertian leaves possessing anisotropic leaf angle distributions yield non-Lambertian reflectance; similar behavior is exhibited for simulated soil surfaces.

  2. Electro-Optical Characterization of Bistable Smectic A Liquid Crystal Displays

    Science.gov (United States)

    Buyuktanir, Ebru Aylin

    My dissertation focuses the characterization and optimization of the electro-optical properties of smectic A (SmA) based liquid crystal (LC) displays. I present the development of robust and flexible bistable SmA LC displays utilizing polymer dispersed liquid crystal (PDLC) technology. The SmA PDLC displays produced on plastic substrates present electrically reversible memory, high contrast ratio, paper-like sunlight readability, and wide viewing angle characteristics. In order to optimize the SmA PDLC display, I investigated polymerization conditions, such as polymer concentration effect, polymerization temperature, and UV-light intensity variations. I characterized the electro-optical responses-such as static-response, time-response, threshold characteristics, and contrast ratio values' of the optimized SmA PDLC display and compared them to those of the pure SmA LC. The best electro-optical performance of SmA PDLC formulation was obtained using the combination of low mW/cm 2 and high mW/cm2 UV-light curing intensity. The contrast ratio of the optimum SmA PDLC at a 5o collection angle was 83% of that of the pure SmA material on plastic substrates. I fabricated 2.5 x 2.5 in., 4 x 4 in., and 6 x 6 in. sized monochrome flexible SmA PDLC displays, as well as red, yellow, and fluorescent dyes colored SmA PDLC displays on plastic substrates. The electro-optic performance of the bistable SmA LC display consisting of a patterned field-induced polymer wall infrastructure was also studied and compared to those of pure SmA material. I found that the contrast ratio of the SmA LC encapsulated between polymer walls was much greater than that of the SmA PDLC system, approaching the contrast ratio value of the pure SmA material. I also improved the electro-optical characteristics of bistable SmA LC displays by adding ferroparticles into the system. Finally, I illustrated the unique capabilities of polarized confocal Raman microscopy (CRM) to resolve the orientational order of Sm

  3. Collective Activity of Many Bistable Assemblies Reproduces Characteristic Dynamics of Multistable Perception.

    Science.gov (United States)

    Cao, Robin; Pastukhov, Alexander; Mattia, Maurizio; Braun, Jochen

    2016-06-29

    The timing of perceptual decisions depends on both deterministic and stochastic factors, as the gradual accumulation of sensory evidence (deterministic) is contaminated by sensory and/or internal noise (stochastic). When human observers view multistable visual displays, successive episodes of stochastic accumulation culminate in repeated reversals of visual appearance. Treating reversal timing as a "first-passage time" problem, we ask how the observed timing densities constrain the underlying stochastic accumulation. Importantly, mean reversal times (i.e., deterministic factors) differ enormously between displays/observers/stimulation levels, whereas the variance and skewness of reversal times (i.e., stochastic factors) keep characteristic proportions of the mean. What sort of stochastic process could reproduce this highly consistent "scaling property?" Here we show that the collective activity of a finite population of bistable units (i.e., a generalized Ehrenfest process) quantitatively reproduces all aspects of the scaling property of multistable phenomena, in contrast to other processes under consideration (Poisson, Wiener, or Ornstein-Uhlenbeck process). The postulated units express the spontaneous dynamics of attractor assemblies transitioning between distinct activity states. Plausible candidates are cortical columns, or clusters of columns, as they are preferentially connected and spontaneously explore a restricted repertoire of activity states. Our findings suggests that perceptual representations are granular, probabilistic, and operate far from equilibrium, thereby offering a suitable substrate for statistical inference. Spontaneous reversals of high-level perception, so-called multistable perception, conform to highly consistent and characteristic statistics, constraining plausible neural representations. We show that the observed perceptual dynamics would be reproduced quantitatively by a finite population of distinct neural assemblies, each with

  4. Reflective optics

    CERN Document Server

    Korsch, Dietrich

    1991-01-01

    This is the first book dedicated exclusively to all-reflective imaging systems. It is a teaching tool as well as a practical design tool for anyone who specializes in optics, particularly for those interested in telescopes, infrared, and grazing-incidence systems. The first part of the book describes a unified geometric optical theory of all-reflective imaging systems (from near-normal to grazing incidence) developed from basic principles. The second part discusses correction methods and a multitude of closed-form solutions of well-corrected systems, supplemented with many conventional and unc

  5. Carrier transport in flexible organic bistable devices of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) polymer layer

    International Nuclear Information System (INIS)

    Son, Dong-Ick; Park, Dong-Hee; Choi, Won Kook; Cho, Sung-Hwan; Kim, Won-Tae; Kim, Tae Whan

    2009-01-01

    The bistable effects of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) (PMMA) polymer single layer by using flexible polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that ZnO nanoparticles were formed inside the PMMA polymer layer. Current-voltage (I-V) measurement on the Al/ZnO nanoparticles embedded in an insulating PMMA polymer layer/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the ZnO nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the ZnO nanoparticles. The carrier transport mechanism of the bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results by analyzing the effect of space charge.

  6. Decision making in noisy bistable systems with time-dependent asymmetry

    Science.gov (United States)

    Nené, Nuno R.; Zaikin, Alexey

    2013-01-01

    Our work draws special attention to the importance of the effects of time-dependent parameters on decision making in bistable systems. Here, we extend previous studies of the mechanism known as speed-dependent cellular decision making in genetic circuits by performing an analytical treatment of the canonical supercritical pitchfork bifurcation problem with an additional time-dependent asymmetry and control parameter. This model has an analogous behavior to the genetic switch. In the presence of transient asymmetries and fluctuations, slow passage through the critical region in both systems increases substantially the probability of specific decision outcomes. We also study the relevance for attractor selection of reaching maximum values for the external asymmetry before and after the critical region. Overall, maximum asymmetries should be reached at an instant where the position of the critical point allows for compensation of the detrimental effects of noise in retaining memory of the transient asymmetries.

  7. Delay-enhanced stability and stochastic resonance in perception bistability under non-Gaussian noise

    International Nuclear Information System (INIS)

    Yang, Tao; Zeng, Chunhua; Liu, Ruifen; Wang, Hua; Mei, Dongcheng

    2015-01-01

    In this paper we investigate the effect of time delay in an attractor network model of perception bistability driven by non-Gaussian noise. Using delay Langevin and Fokker–Planck approaches, the theoretical analysis of the model is presented. It is found that the mean first-passage time (MFPT) as a function of the time delay exhibits a maximum, which is identified as the characteristic of the delay-enhanced stability of the system. This is different to the case of noise-enhanced stability. The non-Gaussian noise-enhanced stability of the system is also analyzed. The signal-to-noise ratio (SNR) as a function of the noise intensity exhibits a maximum. This maximum implies the identifying characteristic of stochastic resonance (SR), and the time delay and non-Gaussian noise can enhance the SR phenomenon. (paper)

  8. Magnetic and optical bistability in tetrairon(III) single molecule magnets functionalized with azobenzene groups.

    Science.gov (United States)

    Prasad, Thazhe Kootteri; Poneti, Giordano; Sorace, Lorenzo; Rodriguez-Douton, Maria Jesus; Barra, Anne-Laure; Neugebauer, Petr; Costantino, Luca; Sessoli, Roberta; Cornia, Andrea

    2012-07-21

    Tetrairon(III) complexes known as "ferric stars" have been functionalized with azobenzene groups to investigate the effect of light-induced trans-cis isomerization on single-molecule magnet (SMM) behaviour. According to DC magnetic data and EPR spectroscopy, clusters dispersed in polystyrene (4% w/w) exhibit the same spin (S = 5) and magnetic anisotropy as bulk samples. Ligand photoisomerization, achieved by irradiation at 365 nm, has no detectable influence on static magnetic properties. However, it induces a small but significant acceleration of magnetic relaxation as probed by AC susceptometry. The pristine behaviour can be almost quantitatively recovered by irradiation with white light. Our studies demonstrate that magnetic and optical bistability can be made to coexist in SMM materials, which are of current interest in molecular spintronics.

  9. Induced fluid rotation and bistable fluidic turn-down valves (a survey

    Directory of Open Access Journals (Sweden)

    Tesař Václav

    2015-01-01

    Full Text Available Paper surveys engineering applications of an unusual fluidic principle — momentum transfer through a relatively small communicating window into a vortex chamber, where the initially stationary fluid is put into rotation. The transfer is often by shear stress acting in the window plane, but may be enhanced and perhaps even dominated by fluid flow crossing the boundary. The case of zero-time-mean fluid transport through the window has found use in experimental fluid mechanics: non-invasive measurement of wall shear stress on objects by evaluating the induced rotation in the vortex chamber. The case with the non-zero flow through the interface became the starting point in development of fluidic valves combining two otherwise mutually incompatible properties: bistability and flow turning down.

  10. Prey-Predator Model with a Nonlocal Bistable Dynamics of Prey

    Directory of Open Access Journals (Sweden)

    Malay Banerjee

    2018-03-01

    Full Text Available Spatiotemporal pattern formation in integro-differential equation models of interacting populations is an active area of research, which has emerged through the introduction of nonlocal intra- and inter-specific interactions. Stationary patterns are reported for nonlocal interactions in prey and predator populations for models with prey-dependent functional response, specialist predator and linear intrinsic death rate for predator species. The primary goal of our present work is to consider nonlocal consumption of resources in a spatiotemporal prey-predator model with bistable reaction kinetics for prey growth in the absence of predators. We derive the conditions of the Turing and of the spatial Hopf bifurcation around the coexisting homogeneous steady-state and verify the analytical results through extensive numerical simulations. Bifurcations of spatial patterns are also explored numerically.

  11. Mean first-passage time of an asymmetric bistable system driven by colour-correlated noise

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiao-Yan; Xu Wei

    2007-01-01

    In this paper, the effect of every parameter (including p, q,r, λ,τ) on the mean first-passage time (MFPT) is investigated in an asymmetric bistable system driven by colour-correlated noise. The expression of MFPT has been obtained by applying the steepest-descent approximation. Numerical results show that (1) the intensity of multiplicative noise p and the intensity of additive noise q play different roles in the MFPT of the system, (2) suppression appears on the curve of the MFPT with small λ (e.g. λ< 0.5) but there is a peak on the curve of the MFPT when λ is big (e.g.λ> 0.5), and (3) with different values of r (e.g. r = 0.1, 0.5, 1.5), the effort of τ on the MFPT is diverse.

  12. Parameter allocation of parallel array bistable stochastic resonance and its application in communication systems

    International Nuclear Information System (INIS)

    Liu Jian; Zhai Qi-Qing; Wang You-Guo; Liu Jin

    2016-01-01

    In this paper, we propose a parameter allocation scheme in a parallel array bistable stochastic resonance-based communication system (P-BSR-CS) to improve the performance of weak binary pulse amplitude modulated (BPAM) signal transmissions. The optimal parameter allocation policy of the P-BSR-CS is provided to minimize the bit error rate (BER) and maximize the channel capacity (CC) under the adiabatic approximation condition. On this basis, we further derive the best parameter selection theorem in realistic communication scenarios via variable transformation. Specifically, the P-BSR structure design not only brings the robustness of parameter selection optimization, where the optimal parameter pair is not fixed but variable in quite a wide range, but also produces outstanding system performance. Theoretical analysis and simulation results indicate that in the P-BSR-CS the proposed parameter allocation scheme yields considerable performance improvement, particularly in very low signal-to-noise ratio (SNR) environments. (paper)

  13. Organic bistable memory devices based on MoO3 nanoparticle embedded Alq3 structures

    Science.gov (United States)

    Abhijith, T.; Kumar, T. V. Arun; Reddy, V. S.

    2017-03-01

    Organic bistable memory devices were fabricated by embedding a thin layer of molybdenum trioxide (MoO3) between two tris-(8-hydroxyquinoline)aluminum (Alq3) layers. The device exhibited excellent switching characteristics with an ON/OFF current ratio of 1.15 × 103 at a read voltage of 1 V. The device showed repeatable write-erase capability and good stability in both the conductance states. These conductance states are non-volatile in nature and can be obtained by applying appropriate voltage pulses. The effect of MoO3 layer thickness and its location in the Alq3 matrix on characteristics of the memory device was investigated. The field emission scanning electron microscopy (FE-SEM) images of the MoO3 layer revealed the presence of isolated nanoparticles. Based on the experimental results, a mechanism has been proposed for explaining the conductance switching of fabricated devices.

  14. Beam-splitter switches based on zenithal bistable liquid-crystal gratings.

    Science.gov (United States)

    Zografopoulos, Dimitrios C; Beccherelli, Romeo; Kriezis, Emmanouil E

    2014-10-01

    The tunable optical diffractive properties of zenithal bistable nematic liquid-crystal gratings are theoretically investigated. The liquid-crystal orientation is rigorously solved via a tensorial formulation of the Landau-de Gennes theory and the optical transmission properties of the gratings are investigated via full-wave finite-element frequency-domain simulations. It is demonstrated that by proper design the two stable states of the grating can provide nondiffracting and diffracting operation, the latter with equal power splitting among different diffraction orders. An electro-optic switching mechanism, based on dual-frequency nematic materials, and its temporal dynamics are further discussed. Such gratings provide a solution towards tunable beam-steering and beam-splitting components with extremely low power consumption.

  15. Stochastic resonance in a time-delayed asymmetric bistable system with mixed periodic signal

    International Nuclear Information System (INIS)

    Yong-Feng, Guo; Wei, Xu; Liang, Wang

    2010-01-01

    This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A general approximate Fokker–Planck equation and the expression of the signal-to-noise ratio are derived through the small time delay approximation at both fundamental harmonics and mixed harmonics. The effects of the additive noise intensity Q, multiplicative noise intensity D, static asymmetry r and delay time τ on the signal-to-noise ratio are discussed. It is found that the higher mixed harmonics and the static asymmetry r can restrain stochastic resonance, and the delay time τ can enhance stochastic resonance. Moreover, the longer the delay time τ is, the larger the additive noise intensity Q and the multiplicative noise intensity D are, when the stochastic resonance appears. (general)

  16. Air-stable memory array of bistable rectifying diodes based on ferroelectric-semiconductor polymer blends

    Science.gov (United States)

    Kumar, Manasvi; Sharifi Dehsari, Hamed; Anwar, Saleem; Asadi, Kamal

    2018-03-01

    Organic bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers have emerged as promising candidates for non-volatile information storage for low-cost solution processable electronics. One of the bottlenecks impeding upscaling is stability and reliable operation of the array in air. Here, we present a memory array fabricated with an air-stable amine-based semiconducting polymer. Memory diode fabrication and full electrical characterizations were carried out in atmospheric conditions (23 °C and 45% relative humidity). The memory diodes showed on/off ratios greater than 100 and further exhibited robust and stable performance upon continuous write-read-erase-read cycles. Moreover, we demonstrate a 4-bit memory array that is free from cross-talk with a shelf-life of several months. Demonstration of the stability and reliable air operation further strengthens the feasibility of the resistance switching in ferroelectric memory diodes for low-cost applications.

  17. Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaopu, E-mail: xl6ba@virginia.edu; Ma, Chung T.; Poon, S. Joseph, E-mail: sjp9x@virginia.edu [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Devaraj, Arun [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Spurgeon, Steven R.; Comes, Ryan B. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2016-01-04

    Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.

  18. Simulating the room-temperature dynamic motion of a ferromagnetic vortex in a bistable potential

    Science.gov (United States)

    Haber, E.; Badea, R.; Berezovsky, J.

    2018-05-01

    The ability to precisely and reliably control the dynamics of ferromagnetic (FM) vortices could lead to novel nonvolatile memory devices and logic gates. Intrinsic and fabricated defects in the FM material can pin vortices and complicate the dynamics. Here, we simulated switching a vortex between bistable pinning sites using magnetic field pulses. The dynamic motion was modeled with the Thiele equation for a massless, rigid vortex subject to room-temperature thermal noise. The dynamics were explored both when the system was at zero temperature and at room-temperature. The probability of switching for different pulses was calculated, and the major features are explained using the basins of attraction map of the two pinning sites.

  19. Isolation by crystallization of translational isomers of a bistable donor-acceptor [2]catenane

    Science.gov (United States)

    Wang, Cheng; Olson, Mark A.; Fang, Lei; Benítez, Diego; Tkatchouk, Ekaterina; Basu, Subhadeep; Basuray, Ashish N.; Zhang, Deqing; Zhu, Daoben; Goddard, William A.; Stoddart, J. Fraser

    2010-01-01

    The template-directed synthesis of a bistable donor-acceptor [2]catenane wherein both translational isomers—one in which a tetrathiafulvalene unit in a mechanically interlocked crown ether occupies the cavity of a cyclobis(paraquat-p-phenylene) ring and the other in which a 1,5-dioxynaphthalene unit in the crown ether resides inside the cavity of the tetracationic cyclophane—exist in equilibrium in solution, has led to the isolation and separation by hand picking of single crystals colored red and green, respectively. These two crystalline co-conformations have been characterized separately at both the molecular and supramolecular levels, and also by dynamic NMR spectroscopy in solution where there is compelling evidence that the mechanically interlocked molecules are present as a complex mixture of translational, configurational, and conformational isomers wherein the isomerization is best described as being a highly dynamic and adaptable phenomenon. PMID:20663950

  20. Differentiating aversive conditioning in bistable perception: Avoidance of a percept vs. salience of a stimulus.

    Science.gov (United States)

    Wilbertz, Gregor; Sterzer, Philipp

    2018-05-01

    Alternating conscious visual perception of bistable stimuli is influenced by several factors. In order to understand the effect of negative valence, we tested the effect of two types of aversive conditioning on dominance durations in binocular rivalry. Participants received either aversive classical conditioning of the stimuli shown alone between rivalry blocks, or aversive percept conditioning of one of the two possible perceptual choices during rivalry. Both groups showed successful aversive conditioning according to skin conductance responses and affective valence ratings. However, while classical conditioning led to an immediate but short-lived increase in dominance durations of the conditioned stimulus, percept conditioning yielded no significant immediate effect but tended to decrease durations of the conditioned percept during extinction. These results show dissociable effects of value learning on perceptual inference in situations of perceptual conflict, depending on whether learning relates to the decision between conflicting perceptual choices or the sensory stimuli per se. Copyright © 2018 Elsevier Inc. All rights reserved.