WorldWideScience

Sample records for bistable vertical-cavity surface-emitting

  1. Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Hurtado, A. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Institute of Photonics, Physics Department, University of Strathclyde, Wolfson Centre, 106 Rottenrow East, Glasgow G4 0NW, Scotland (United Kingdom); Korpijarvi, V.-M.; Guina, M. [Optoelectronics Research Centre (ORC), Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere (Finland)

    2015-01-12

    We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.

  2. 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.

  3. III-Nitride Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Leonard, John T.

    Vertical-cavity surface-emitting lasers (VCSELs) have a long history of development in GaAs-based and InP-based systems, however III-nitride VCSELs research is still in its infancy. Yet, over the past several years we have made dramatic improvements in the lasing characteristics of these highly complex devices. Specifically, we have reduced the threshold current density from ˜100 kA/cm2 to ˜3 kA/cm2, while simultaneously increasing the output power from ˜10 muW to ˜550 muW. These developments have primarily come about by focusing on the aperture design and intracavity contact design for flip-chip dual dielectric DBR III-nitride VCSELs. We have carried out a number of studies developing an Al ion implanted aperture (IIA) and photoelectrochemically etched aperture (PECA), while simultaneously improving the quality of tin-doped indium oxide (ITO) intracavity contacts, and demonstrating the first III-nitride VCSEL with an n-GaN tunnel junction intracavity contact. Beyond these most notable research fronts, we have analyzed numerous other parameters, including epitaxial growth, flip-chip bonding, substrate removal, and more, bringing further improvement to III-nitride VCSEL performance and yield. This thesis aims to give a comprehensive discussion of the relevant underlying concepts for nonpolar VCSELs, while detailing our specific experimental advances. In Section 1, we give an overview of the applications of VCSELs generally, before describing some of the potential applications for III-nitride VCSELs. This is followed by a summary of the different material systems used to fabricate VCSELs, before going into detail on the basic design principles for developing III-nitride VCSELs. In Section 2, we outline the basic process and geometry for fabricating flip-chip nonpolar VCSELs with different aperture and intracavity contact designs. Finally, in Section 3 and 4, we delve into the experimental results achieved in the last several years, beginning with a discussion on

  4. Polymer-coated vertical-cavity surface-emitting laser diode vapor sensor

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2010-01-01

    We report a new method for monitoring vapor concentration of volatile organic compounds using a vertical-cavity surface-emitting laser (VCSEL). The VCSEL is coated with a polymer thin film on the top distributed Bragg reflector (DBR). The analyte absorption is transduced to the electrical domain ...

  5. Acetone vapor sensing using a vertical cavity surface emitting laser diode coated with polystyrene

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgaard; Larsen, Niels Bent

    2009-01-01

    We report theoretical and experimental on a new vapor sensor, using a single-mode vertical-cavity surface-emitting laser (VCSEL) coated with a polymer sensor coating, which can detect acetone vapor at a volume fraction of 2.5%. The sensor provides the advantage of standard packaging, small form......-factor, mechanical stability and low cost when combined with a monolithically integrated photodiode detector....

  6. Controllable spiking patterns in long-wavelength vertical cavity surface emitting lasers for neuromorphic photonics systems

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, Antonio, E-mail: antonio.hurtado@strath.ac.uk [Institute of Photonics, SUPA Department of Physics, University of Strathclyde, TIC Centre, 99 George Street, Glasgow G1 1RD (United Kingdom); Javaloyes, Julien [Departament de Fisica, Universitat de les Illes Balears, c/Valldemossa km 7.5, 07122 Mallorca (Spain)

    2015-12-14

    Multiple controllable spiking patterns are achieved in a 1310 nm Vertical-Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely, parallel and orthogonal. Furthermore, reproducible spiking responses are demonstrated experimentally at sub-nanosecond speed resolution and with a controlled number of spikes fired. This work opens therefore exciting research avenues for the use of VCSELs in ultrafast neuromorphic photonic systems for non-traditional computing applications, such as all-optical binary-to-spiking format conversion and spiking information encoding.

  7. Transverse-mode-selectable microlens vertical-cavity surface-emitting laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Debernardi, Pierluigi; Lee, Yong Tak

    2010-01-01

    of the mode selection properties of the new structure is rigorously analyzed and compared to other structures reported in the literature. The possibility of engineering the emission shape while retaining strong single mode operation is highly desirable for low-cost mid-range optical interconnects applications......A new vertical-cavity surface-emitting laser structure employing a thin microlens is suggested and numerically investigated. The laser can be made to emit in either a high-power Gaussian-shaped single-fundamental mode or a high-power doughnut-shaped higher-order mode. The physical origin...

  8. Vertical-cavity surface-emitting laser vapor sensor using swelling polymer reflection modulation

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Nielsen, Claus Højgård; Dohn, Søren

    2012-01-01

    Vapor detection using a low-refractive index polymer for reflection modulation of the top mirror in a vertical-cavity surface-emitting laser (VCSEL) is demonstrated. The VCSEL sensor concept presents a simple method to detect the response of a sensor polymer in the presence of volatile organic co...... compounds. We model the physics as a change in the top mirror loss caused by swelling of the polymer upon absorbing the target volatile organic compound. Further we show how acetone vapors at 82 000 ppm concentration can change the polymer coated VCSEL output power by 20 mu W....

  9. Spectral-Modulation Characteristics of Vertical-Cavity Surface-Emitting Lasers

    Science.gov (United States)

    Vas'kovskaya, M. I.; Vasil'ev, V. V.; Zibrov, S. A.; Yakovlev, V. P.; Velichanskii, V. L.

    2018-01-01

    The requirements imposed on vertical-cavity surface-emitting lasers in a number of metrological problems in which optical pumping of alkali atoms is used are considered. For lasers produced by different manufacturers, these requirements are compared with the experimentally observed spectral characteristics at a constant pump current and in the microwave modulation mode. It is shown that a comparatively small number of lasers in the microwave modulation mode make it possible to obtain the spectrum required for atomic clocks based on the coherent population-trapping effect.

  10. The simulation of thermal characteristics of 980 nm vertical cavity surface emitting lasers

    Science.gov (United States)

    Fang, Tianxiao; Cui, Bifeng; Hao, Shuai; Wang, Yang

    2018-02-01

    In order to design a single mode 980 nm vertical cavity surface emitting laser (VCSEL), a 2 μm output aperture is designed to guarantee the single mode output. The effects of different mesa sizes on the lattice temperature, the output power and the voltage are simulated under the condition of continuous working at room temperature, to obtain the optimum process parameters of mesa. It is obtained by results of the crosslight simulation software that the sizes of mesa radius are between 9.5 to 12.5 μm, which cannot only obtain the maximum output power, but also improve the heat dissipation of the device. Project supported by the Beijing Municipal Eduaction Commission (No. PXM2016_014204_500018) and the Construction of Scientific and Technological Innovation Service Ability in 2017 (No. PXM2017_014204_500034).

  11. VCSELs Fundamentals, Technology and Applications of Vertical-Cavity Surface-Emitting Lasers

    CERN Document Server

    2013-01-01

    The huge progress which has been achieved in the field is covered here, in the first comprehensive monograph on vertical-cavity surface-emitting lasers (VCSELs) since eight years. Apart from chapters reviewing the research field and the laser fundamentals, there are comprehensive updates on red and blue emitting VCSELs, telecommunication VCSELs, optical transceivers, and parallel-optical links for computer interconnects. Entirely new contributions are made to the fields of vectorial three-dimensional optical modeling, single-mode VCSELs, polarization control, polarization dynamics, very-high-speed design, high-power emission, use of high-contrast gratings, GaInNAsSb long-wavelength VCSELs, optical video links, VCSELs for optical mice and sensing, as well as VCSEL-based laser printing. The book appeals to researchers, optical engineers and graduate students.

  12. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    KAUST Repository

    Leonard, J. T.

    2015-07-06

    © 2015 AIP Publishing LLC. We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3nm quantum well width, 1nm barriers, a 5nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406nm nonpolar VCSEL with a low threshold current density (∼16kA/cm2), a peak output power of ∼12μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  13. Transverse mode dynamics in vertical-cavity surface-emitting lasers: Spatiotemporal versus modal expansion descriptions

    International Nuclear Information System (INIS)

    Mulet, Josep; Balle, Salvador

    2002-01-01

    We discuss the range of validity of a modal description for the spatiotemporal dynamics of the optical field in vertical-cavity surface-emitting lasers. We focus on the secondary pulsations that appear during the turn-off transients when the injection current is modulated by a square-wave signal. We compare the results obtained with both a full spatiotemporal model [J. Mulet and S. Balle, IEEE J. Quantum. Electron. 38, 291 (2002)] and a modal expansion derived from this model. We find that the results obtained from the two descriptions agree for strong lateral guiding. However, for weak lateral guiding we find differences because the optical-field profile changes significantly due to spatial changes in the refractive index induced by the carrier density. The reason is that in the full spatiotemporal model a shrinkage of the mode profile occurs, which leads to an enhancement of the secondary pulsations. This effect is not included in the modal expansion, and it determines the limits of validity of such an approach for gain-guided devices

  14. Nonlinear dynamic behaviors of an optically injected vertical-cavity surface-emitting laser

    International Nuclear Information System (INIS)

    Li Xiaofeng; Pan Wei; Luo Bin; Ma Dong; Wang Yong; Li Nuohan

    2006-01-01

    Nonlinear dynamics of a vertical-cavity surface-emitting laser (VCSEL) with external optical injection are studied numerically. We consider a master-slave configuration where the dynamic characteristics of the slave are affected by the optical injection from the master, and we also establish the corresponding Simulink model. The period-doubling route as well as the period-halving route is observed, where the regular, double-periodic, and chaotic pulsings are found. By adjusting the injection strength properly, the laser can be controlled to work at a given state. The effects of frequency detuning on the nonlinear behaviors are also investigated in terms of the bifurcation diagrams of photon density with the frequency detuning. For weak injection case, the nonlinear dynamics shown by the laser are quite different when the value of frequency detuning varies contrarily (positive and negative direction). If the optical injection is strong enough, the slave can be locked by the master even though the frequency detuning is relatively large

  15. Optically pumped GaN vertical cavity surface emitting laser with high index-contrast nanoporous distributed Bragg reflector.

    Science.gov (United States)

    Lee, Seung-Min; Gong, Su-Hyun; Kang, Jin-Ho; Ebaid, Mohamed; Ryu, Sang-Wan; Cho, Yong-Hoon

    2015-05-04

    Laser operation of a GaN vertical cavity surface emitting laser (VCSEL) is demonstrated under optical pumping with a nanoporous distributed Bragg reflector (DBR). High reflectivity, approaching 100%, is obtained due to the high index-contrast of the nanoporous DBR. The VCSEL system exhibits low threshold power density due to the formation of high Q-factor cavity, which shows the potential of nanoporous medium for optical devices.

  16. Optical Injection Locking of Vertical Cavity Surface-Emitting Lasers: Digital and Analog Applications

    Science.gov (United States)

    Parekh, Devang

    With the rise of mobile (cellphones, tablets, notebooks, etc.) and broadband wireline communications (Fiber to the Home), there are increasing demands being placed on transmitters for moving data from device to device and around the world. Digital and analog fiber-optic communications have been the key technology to meet this challenge, ushering in ubiquitous Internet and cable TV over the past 20 years. At the physical layer, high-volume low-cost manufacturing of semiconductor optoelectronic devices has played an integral role in allowing for deployment of high-speed communication links. In particular, vertical cavity surface emitting lasers (VCSEL) have revolutionized short reach communications and are poised to enter more markets due to their low cost, small size, and performance. However, VCSELs have disadvantages such as limited modulation performance and large frequency chirp which limits fiber transmission speed and distance, key parameters for many fiber-optic communication systems. Optical injection locking is one method to overcome these limitations without re-engineering the VCSEL at the device level. By locking the frequency and phase of the VCSEL by the direct injection of light from another laser oscillator, improved device performance is achieved in a post-fabrication method. In this dissertation, optical injection locking of VCSELs is investigated from an applications perspective. Optical injection locking of VCSELs can be used as a pathway to reduce complexity, cost, and size of both digital and analog fiber-optic communications. On the digital front, reduction of frequency chirp via bit pattern inversion for large-signal modulation is experimentally demonstrated showing up to 10 times reduction in frequency chirp and over 90 times increase in fiber transmission distance. Based on these results, a new reflection-based interferometric model for optical injection locking was established to explain this phenomenon. On the analog side, the resonance

  17. GaN-based vertical-cavity surface emitting lasers with sub-milliamp threshold and small divergence angle

    Science.gov (United States)

    Yeh, P. S.; Chang, C.-C.; Chen, Y.-T.; Lin, D.-W.; Liou, J.-S.; Wu, C. C.; He, J. H.; Kuo, H.-C.

    2016-12-01

    A GaN-based vertical-cavity surface emitting laser (VCSEL) structure featuring a silicon-diffusion-defined current blocking layer for lateral confinement is described. Sub-milliamp threshold currents were achieved for both 3- and 5-μm-aperture VCSELs under continuous-wave operation at room temperature. The vertical cavity was defined by a top dielectric distributed Bragg reflector (DBR) and a bottom epitaxial DBR. The emission spectrum exhibited a single peak at 411.2 nm with a linewidth of 0.4 nm and a side mode suppression ratio of more than 10 dB before device packaging. The full-width-at-half-maximum divergence angle of the 3-μm-aperture VCSEL was as small as approximately 5° which is the lowest number reported. These results implied the 3-μm-aperture VCSEL was in near single-mode operation.

  18. Vertical-cavity surface-emitting lasers enable high-density ultra-high bandwidth optical interconnects

    Science.gov (United States)

    Chitica, N.; Carlsson, J.; Svenson, L.-G.; Chacinski, M.

    2015-03-01

    Vertical-Cavity Surface-Emitting Lasers (VCSELs) are key components enabling power- and cost-efficient, high-density, ultra-high bandwidth parallel optical interconnects for data center and high-performance computing applications. This paper presents recent developments at TE Connectivity (TE) in the area of 25 Gb/s per channel-class VCSEL and optical transmitter technology for applications such as 100G and 400G Ethernet and Enhanced Data Rate InfiniBand pluggable and mid-board connectivity solutions.

  19. Electron spin injection from a regrown Fe layer in a spin-polarized vertical-cavity surface-emitting laser

    Science.gov (United States)

    Holub, M.; Bhattacharya, P.; Shin, J.; Saha, D.

    2007-04-01

    An electroluminescence circular polarization of 23% and threshold current reduction of 11% are obtained in an electrically pumped spin-polarized vertical-cavity surface-emitting laser. Electron spin injection is accomplished utilizing a regrown Fe/ n-AlGaAs Schottky tunnel barrier deposited around the base of the laser mesas. Negligible circular polarizations and threshold current reductions are measured for nonmagnetic and Fe-based control VCSELs, which provides convincing evidence of spin injection, transport, and detection in our spin-polarized laser.

  20. High-Speed Semiconductor Vertical-Cavity Surface-Emitting Lasers for Optical Data-Transmission Systems (Review)

    Science.gov (United States)

    Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Sakharov, A. V.; Ustinov, V. M.

    2018-01-01

    The main problems of providing a high-speed operation semiconductor lasers with a vertical microcavity (so-called "vertical-cavity surface-emitting lasers") under amplitude modulation and ways to solve them have been considered. The influence of the internal properties of the radiating active region and the electrical parasitic elements of the equivalent circuit of lasers are discussed. An overview of approaches that lead to an increase of the cutoff parasitic frequency, an increase of the differential gain of the active region, the possibility of the management of mode emission composition and the lifetime of photons in the optical microcavities, and reduction of the influence of thermal effects have been presented. The achieved level of modulation bandwidth of ˜30 GHz is close to the maximum achievable for the classical scheme of the direct-current modulation, which makes it necessary to use a multilevel modulation format to further increase the information capacity of optical channels constructed on the basis of vertical-cavity surface-emitting lasers.

  1. 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.

  2. Single-exposure two-dimensional superresolution in digital holography using a vertical cavity surface-emitting laser source array.

    Science.gov (United States)

    Granero, Luis; Zalevsky, Zeev; Micó, Vicente

    2011-04-01

    We present a new implementation capable of producing two-dimensional (2D) superresolution (SR) imaging in a single exposure by aperture synthesis in digital lensless Fourier holography when using angular multiplexing provided by a vertical cavity surface-emitting laser source array. The system performs the recording in a single CCD snapshot of a multiplexed hologram coming from the incoherent addition of multiple subholograms, where each contains information about a different 2D spatial frequency band of the object's spectrum. Thus, a set of nonoverlapping bandpass images of the input object can be recovered by Fourier transformation (FT) of the multiplexed hologram. The SR is obtained by coherent addition of the information contained in each bandpass image while generating an enlarged synthetic aperture. Experimental results demonstrate improvement in resolution and image quality.

  3. Steady-state characteristics of lateral p-n junction vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Ryzhii, V.; Tsutsui, N.; Khmyrova, I.; Ikegami, T.; Vaccaro, P. O.; Taniyama, H.; Aida, T.

    2001-09-01

    We developed an analytical device model for lateral p-n junction vertical-cavity surface-emitting lasers (LJVCSELs) with a quantum well active region. The model takes into account the features of the carrier injection, transport, and recombination in LJVCSELs as well as the features of the photon propagation in the cavity. This model is used for the calculation and analysis of the LJVCSEL steady-state characteristics. It is shown that the localization of the injected electrons primarily near the p-n junction and the reabsorption of lateral propagating photons significantly effects the LJVCSELs performance, in particular, the LJVCSEL threshold current and power-current characteristics. The reincarnation of electrons and holes due to the reabsorption of lateral propagating photons can substantially decrease the threshold current.

  4. Eigenmodes of spin vertical-cavity surface-emitting lasers with local linear birefringence and gain dichroism

    Science.gov (United States)

    Fördös, T.; Jaffrès, H.; Postava, K.; Seghilani, M. S.; Garnache, A.; Pištora, J.; Drouhin, H. J.

    2017-10-01

    We present a general method for the modeling of semiconductor lasers such as a vertical-cavity surface-emitting laser and a vertical-external-cavity surface-emitting laser containing multiple quantum wells and involving anisotropies that may reveal (i) a local linear birefringence due to the strain field at the surface or (ii) a birefringence in quantum wells due to phase amplitude coupling originating from the reduction of the biaxial D2 d symmetry group to the C2 v symmetry group at the III-V ternary semiconductor interfaces. From a numerical point of view, a scattering S-matrix recursive method is implemented using a gain or amplification tensor derived analytically from the Maxwell-Bloch equations. It enables one to model the properties of the emission (threshold, polarization, and mode splitting) from the laser with multiple quantum well active zones by searching for the resonant eigenmodes of the cavity. The method is demonstrated on real laser structures and is presently used for the extraction of optical permittivity tensors of surface strain and quantum wells in agreement with experiments. The method can be generalized to find the laser eigenmodes in the most general case of circular polarized pumps (unbalance between the spin-up and spin-down channels) and/or dichroism allowing an elliptically polarized light emission as recently demonstrated experimentally when the linear birefringence is almost compensated [Joly et al., Opt. Lett. 42, 651 (2017), 10.1364/OL.42.000651].

  5. Operation of a novel hot-electron vertical-cavity surface-emitting laser

    Science.gov (United States)

    Balkan, Naci; O'Brien-Davies, Angela; Thoms, A. B.; Potter, Richard J.; Poolton, Nigel; Adams, Michael J.; Masum, J.; Bek, Alpan; Serpenguzel, Ali; Aydinli, Atilla; Roberts, John S.

    1998-07-01

    The hot Electron Light Emission and Lasing in Semiconductor Heterostructures devices (HELLISH-1) is novel surface emitter consisting of a GaAs quantum well, within the depletion region, on the n side of Ga1-xAlxAs p- n junction. It utilizes hot electron transport parallel to the layers and injection of hot electron hole pairs into the quantum well through a combination of mechanisms including tunnelling, thermionic emission and diffusion of `lucky' carriers. Super Radiant HELLISH-1 is an advanced structure incorporating a lower distributed Bragg reflector (DBR). Combined with the finite reflectivity of the upper semiconductor-air interface reflectivity it defines a quasi- resonant cavity enabling emission output from the top surface with a higher spectral purity. The output power has increased by two orders of magnitude and reduced the full width at half maximum (FWHM) to 20 nm. An upper DBR added to the structure defines HELLISH-VCSEL which is currently the first operational hot electron surface emitting laser and lases at room temperature with a 1.5 nm FWHM. In this work we demonstrate and compare the operation of UB-HELLISH-1 and HELLISH-VCSEL using experimental and theoretical reflectivity spectra over an extensive temperature range.

  6. Dynamics of 1.55 μm Wavelength Single-Mode Vertical-Cavity Surface-Emitting Laser Output under External Optical Injection

    Directory of Open Access Journals (Sweden)

    Kyong Hon Kim

    2012-01-01

    Full Text Available We review the temporal dynamics of the laser output spectrum and polarization state of 1.55 μm wavelength single-mode (SM vertical-cavity surface-emitting lasers (VCSELs induced by external optical beam injection. Injection of an external continuous-wave laser beam to a gain-switched SM VCSEL near the resonance wavelength corresponding to its main polarization-mode output was critical for improvement of its laser pulse generation characteristics, such as pulse timing-jitter reduction, linewidth narrowing, pulse amplitude enhancement, and pulse width shortening. Pulse injection of pulse width shorter than the cavity photon lifetime into the SM VCSEL in the orthogonal polarization direction with respect to its main polarization mode caused temporal delay of the polarization recovery after polarization switching (PS, and its delay was found to be the minimum at an optimized bias current. Polarization-mode bistability was observed even in the laser output of an SM VCSEL of a standard circularly cylindrical shape and used for all-optical flip-flop operations with set and reset injection pulses of very low pulse energy of order of the 3.5~4.5 fJ.

  7. Tradeoffs of vertical-cavity surface emitting lasers modeling for the development of driver circuits in short distance optical links

    Science.gov (United States)

    Sialm, Gion; Erni, Daniel; Vez, Dominique; Kromer, Christian; Ellinger, Frank; Bona, Gian-Luca; Morf, Thomas; Jäckel, Heinz

    2005-10-01

    In short-distance optical links, the development of driving circuits for vertical-cavity surface-emitting lasers (VCSELs) requires precise and computationally efficient VCSEL models. A small-signal model of a VCSEL is computationally efficient and simple to implement; however, it does not take into account the nonlinear output behavior of the VCSEL. In contrast, VCSEL models that are highly based on first principles cannot be implemented in standard circuit device simulators, because the simulation of eye diagrams becomes too time consuming. We present another approach using VCSEL models, which are based on the 1-D rate equations. Our analysis shows that they combine efficient extraction and short simulation time with an accurate calculation of eye diagrams over a wide range of ambient temperatures. As different implementations of the rate equations exist, tradeoffs between three different versions are presented and compared with measured GaAs oxide-confined VCSELs. The first model has a linear and the second a logarithmic function of the gain versus the carrier density. The third model considers the additional transport time for carriers to reach the active region with quantum wells. For parameter extraction, a minimum set of parameters is identified, which can be determined from fundamental measurements.

  8. A GaInAsP/InP Vertical Cavity Surface Emitting Laser for 1.5 m m operation

    Science.gov (United States)

    Sceats, R.; Balkan, N.; Adams, M. J.; Masum, J.; Dann, A. J.; Perrin, S. D.; Reid, I.; Reed, J.; Cannard, P.; Fisher, M. A.; Elton, D. J.; Harlow, M. J.

    1999-04-01

    We present the results of our studies concerning the pulsed operation of a bulk GaInAsP/InP vertical cavity surface emitting laser (VCSEL). The device is tailored to emit at around 1.5 m m at room temperature. The structure has a 45 period n-doped GaInAsP/InP bottom distributed Bragg reflector (DBR), and a 4 period Si/Al2O3 dielectric top reflector defining a 3-l cavity. Electroluminescence from a 16 m m diameter top window was measured in the pulsed injection mode. Spectral measurements were recorded in the temperature range between 125K and 240K. Polarisation, lasing threshold current and linewidth measurements were also carried out at the same temperatures. The threshold current density has a broad minimum at temperatures between 170K and 190K, (Jth=13.2 kA/cm2), indicating a good match between the gain and the cavity resonance in this temperature range. Maximum emitted power from the VCSEL is 0.18 mW at 180K.

  9. Attractor hopping between polarization dynamical states in a vertical-cavity surface-emitting laser subject to parallel optical injection

    Science.gov (United States)

    Denis-le Coarer, Florian; Quirce, Ana; Valle, Angel; Pesquera, Luis; Rodríguez, Miguel A.; Panajotov, Krassimir; Sciamanna, Marc

    2018-03-01

    We present experimental and theoretical results of noise-induced attractor hopping between dynamical states found in a single transverse mode vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. These transitions involve dynamical states with different polarizations of the light emitted by the VCSEL. We report an experimental map identifying, in the injected power-frequency detuning plane, regions where attractor hopping between two, or even three, different states occur. The transition between these behaviors is characterized by using residence time distributions. We find multistability regions that are characterized by heavy-tailed residence time distributions. These distributions are characterized by a -1.83 ±0.17 power law. Between these regions we find coherence enhancement of noise-induced attractor hopping in which transitions between states occur regularly. Simulation results show that frequency detuning variations and spontaneous emission noise play a role in causing switching between attractors. We also find attractor hopping between chaotic states with different polarization properties. In this case, simulation results show that spontaneous emission noise inherent to the VCSEL is enough to induce this hopping.

  10. 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

  11. Bistable Output from a Coupled-Resonator Vertical-Cavity Laser Diode

    Energy Technology Data Exchange (ETDEWEB)

    FISCHER,ARTHUR J.; CHOQUETTE,KENT D.; CHOW,WENG W.; ALLERMAN,ANDREW A.; GEIB,KENT M.

    2000-07-20

    The authors 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 {micro}W to the electrical power applied to the top cavity. Theoretical analysis suggests that 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.

  12. Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

    KAUST Repository

    Leonard, J. T.

    2016-03-01

    We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with III-nitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 mu m aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of similar to 550 mu W with a threshold current density of similar to 3.5 kA/cm(2), while the ITO VCSELs show peak powers of similar to 80 mu W and threshold current densities of similar to 7 kA/cm

  13. Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, J. T., E-mail: jtleona01@gmail.com; Yonkee, B. P.; Cohen, D. A.; Megalini, L.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Lee, S. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); DenBaars, S. P.; Nakamura, S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2016-01-18

    We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC) etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PEC etch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PEC etch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm{sup 2} (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP{sub 12,1}), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.

  14. Research of the use of silver nanowires as a current spreading layer on vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Guo, Xia; Shi, Lei; Li, Chong; Dong, Jian; Liu, Bai; Hu, Shuai; He, Yan

    2016-11-01

    Silver nanowire (AgNW) film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers (VCSELs) with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality. Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm. The performance of VCSELs with and without AgNW film was studied. When the AgNW film was applied to the surface of VCSELs, due to its better current spreading effect, the maximum output optical power increased from 23.4 mW to 24.4 mW, the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA, the differential resistance decreased from 23.95 Ω to 21.13 Ω, and the far field pattern at 50 mA decreased from 21.6° to 19.2°. At the same time, the near field test results showed that the light in the aperture was more uniform, and the far field exhibited a better single peak characteristic. Various results showed that VCSELs with AgNW on the surface showed better beam quality. Project supported by the National Natural Science Foundation of China (Grant Nos. 61335004 and 61505003), the National High Technology Research and Development Program of China (Grant No. 2015AA017101), and the National Key Research and Development of China (Grant No. 2016YFB0400603).

  15. Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

    Science.gov (United States)

    Leonard, J. T.; Young, E. C.; Yonkee, B. P.; Cohen, D. A.; Shen, C.; Margalith, T.; Ng, T. K.; DenBaars, S. P.; Ooi, B. S.; Speck, J. S.; Nakamura, S.

    2016-02-01

    We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with IIInitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 μm aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of ~550 μW with a threshold current density of ~3.5 kA/cm2, while the ITO VCSELs show peak powers of ~80 μW and threshold current densities of ~7 kA/cm2.

  16. Optically pumped vertical-cavity surface-emitting laser at 374.9 nm with an electrically conducting n-type distributed Bragg reflector

    Science.gov (United States)

    Liu, Yuh-Shiuan; Saniul Haq, Abul Fazal Muhammad; Mehta, Karan; Kao, Tsung-Ting; Wang, Shuo; Xie, Hongen; Shen, Shyh-Chiang; Yoder, P. Douglas; Ponce, Fernando A.; Detchprohm, Theeradetch; Dupuis, Russell D.

    2016-11-01

    An optically pumped vertical-cavity surface-emitting laser with an electrically conducting n-type distributed Bragg reflector was achieved at 374.9 nm. An epitaxially grown 40-pair n-type AlGaN/GaN distributed Bragg reflector was used as the bottom mirror, while the top mirror was formed by a dielectric distributed Bragg reflector composed of seven pairs of HfO2/SiO2. A numerical simulation for the optical mode clearly demonstrated that a high confinement factor was achieved and the threshold pumping power density at room temperature was measured as 1.64 MW/cm2. The achieved optically pumped laser demonstrates the potential of utilizing an n-type distributed Bragg reflector for surface-emitting optical devices.

  17. Characterization of 2.3 μm GaInAsSb-based vertical-cavity surface-emitting laser structures using photo-modulated reflectance

    Energy Technology Data Exchange (ETDEWEB)

    Chai, G. M. T. [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Hosea, T. J. C., E-mail: j.hosea@surrey.ac.uk [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Fox, N. E.; Hild, K.; Ikyo, A. B.; Marko, I. P.; Sweeney, S. J. [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Bachmann, A.; Arafin, S.; Amann, M.-C. [Walter Schottky Institut, Technische Universität Munchen, Am Coulombwall 4, D-85748 Garching (Germany)

    2014-01-07

    We report angle dependent and temperature dependent (9 K–300 K) photo-modulated reflectance (PR) studies on vertical-cavity surface-emitting laser (VCSEL) structures, designed for 2.3 μm mid-infrared gas sensing applications. Changing the temperature allows us to tune the energies of the quantum well (QW) transitions relative to the VCSEL cavity mode (CM) energy. These studies show that this VCSEL structure has a QW-CM offset of 21 meV at room temperature. Consequently the QW ground-state transition comes into resonance with the CM at 220 ± 2 K. The results from these PR studies are closely compared with those obtained in a separate study of actual operating devices and show how the PR technique may be useful for device optimisation without the necessity of having first to process the wafers into working devices.

  18. A UWOC system based on a 6 m/5.2 Gbps 680 nm vertical-cavity surface-emitting laser

    Science.gov (United States)

    Li, Chung-Yi; Tsai, Wen-Shing

    2018-02-01

    This study proves that an underwater wireless optical communication (UWOC) based on a 6 m/5.2 Gbps 68 nm vertical-cavity surface-emitting laser (VCSEL)-based system is superior to a 405 nm UWOC system. This UWOC application is the first to use a VCSEL at approximately 680 nm. The experiment also proved that a 680 nm VCSEL has the same transmission distance as that of an approximately 405 nm laser diode. The 680 nm VCSEL has a 5.2 Gbps high transmission rate and can transmit up to 6 m. Thus, the setup is the best alternative solution for high-speed UWOC applications.

  19. Low threshold continuous-wave lasing of yellow-green InGaN-QD vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Weng, Guoen; Mei, Yang; Liu, Jianping; Hofmann, Werner; Ying, Leiying; Zhang, Jiangyong; Bu, Yikun; Li, Zengcheng; Yang, Hui; Zhang, Baoping

    2016-07-11

    Low threshold continuous-wave (CW) lasing of current injected InGaN quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs) was achieved at room temperature. The VCSEL was fabricated by metal bonding technique on a copper substrate to improve the heat dissipation ability of the device. For the first time, lasing was obtained at yellow-green wavelength of 560.4 nm with a low threshold of 0.61 mA, corresponding to a current density of 0.78 kA/cm2. A high degree of polarization of 94% were measured. Despite the operation in the range of "green gap" of GaN-based devices, single longitudinal mode laser emission was clearly achieved due to the high quality of active region based on InGaN QDs and the excellent thermal design of the VCSELs.

  20. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Liu, W. J.; Hu, X. L.; Ying, L. Y.; Chen, S. Q.; Zhang, J. Y.; Akiyama, H.; Cai, Z. P.; Zhang, B. P.

    2015-04-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400 nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355 nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355 nm pulsed laser. These were explained by taking into account of the significant heating effect under 355 nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs.

  1. Surface photovoltage spectroscopy as a valuable nondestructive characterization technique for GaAs/GaAlAs vertical-cavity surface-emitting laser structures

    CERN Document Server

    Liang, J S; Huang, Y S; Tien, C W; Chang, Y M; Chen, C W; Li, N Y; Tiong, K K; Pollak, F H

    2003-01-01

    We have investigated an 850 nm GaAs/GaAlAs (001) vertical-cavity surface-emitting laser (VCSEL) structure using angle- and temperature-dependent surface photovoltage spectroscopy (SPS). The SPS measurements were performed as functions of angle of incidence (0 deg. <= theta <= 60 deg.) and temperature (25 deg. C <= T <= 215 deg. C) for both the metal-insulator-semiconductor (MIS) and wavelength-modulated MIS configurations. Angle-dependent reflectance (R) measurements have also been performed to illustrate the superior features of the SPS technique. The SPS spectra exhibit both the fundamental conduction to heavy-hole excitonic transition of quantum well and cavity mode (CM) plus a rich interference pattern related to the mirror stacks, whereas in the R spectra only the CM and interference features are clearly visible. The variations of SPS spectra as functions of incident angle and temperature enable exploration of light emission from the quantum well confined in a microcavity with relation to the...

  2. Compact electro-absorption modulator integrated with vertical-cavity surface-emitting laser for highly efficient millimeter-wave modulation

    International Nuclear Information System (INIS)

    Dalir, Hamed; Ahmed, Moustafa; Bakry, Ahmed; Koyama, Fumio

    2014-01-01

    We demonstrate a compact electro-absorption slow-light modulator laterally-integrated with an 850 nm vertical-cavity surface-emitting laser (VCSEL), which enables highly efficient millimeter-wave modulation. We found a strong leaky travelling wave in the lateral direction between the two cavities via widening the waveguide width with a taper shape. The small signal response of the fabricated device shows a large enhancement of over 55 dB in the modulation amplitude at frequencies beyond 35 GHz; thanks to the photon-photon resonance. A large group index of over 150 in a Bragg reflector waveguide enables the resonance at millimeter wave frequencies for 25 μm long compact modulator. Based on the modeling, we expect a resonant modulation at a higher frequency of 70 GHz. The resonant modulation in a compact slow-light modulator plays a significant key role for high efficient narrow-band modulation in the millimeter wave range far beyond the intrinsic modulation bandwidth of VCSELs.

  3. A Study of the interaction of radiation and semiconductor lasers: an analysis of transient and permanent effects induced on edge emitting and vertical cavity surface emitting laser diodes

    International Nuclear Information System (INIS)

    Pailharey, Eric

    2000-01-01

    The behavior of laser diodes under transient environment is presented in this work. The first section describes the basic phenomena of radiation interaction with matter. The radiative environments, the main characteristics of laser diodes and the research undertaken on the subject are presented and discussed. The tests on 1300 nm edge emitting laser diode are presented in the second section. The response to a transient ionizing excitation is explored using a 532 nm laser beam. The time of return to steady state after the perturbation is decomposed into several steps: decrease of the optical power during excitation, turn-on delay, relaxation oscillations and optical power offset. Their origins are analyzed using the device structure. To include all the phenomena in a numerical simulation of the device, an individual study of low conductivity materials used for the lateral confinement of the current density is undertaken. The effects of a single particle traversing the optical cavity and an analysis of permanent damages induced by neutrons are also determined. In the last section, 850 nm vertical cavity surface emitting laser diodes (VCSEL) are studied. The behavior of these devices which performances are in constant evolution, is investigated as a function of both temperature and polarization. Then VCSEL are submitted to transient ionizing irradiation and their responses are compared to those of edge emitting diodes. When proton implantation is used in the process, we observe the same behavior for both technologies. VCSEL were submitted to neutron fluence and we have studied the influence of the damages on threshold current, emission patterns and maximum of optical power. (author) [fr

  4. Continuous wave operation of high power GaN-based blue vertical-cavity surface-emitting lasers using epitaxial lateral overgrowth

    Science.gov (United States)

    Hamaguchi, Tatsushi; Fuutagawa, Noriyuki; Izumi, Shouichiro; Murayama, Masahiro; Narui, Hironobu

    2016-02-01

    We have succeeded in achieving continuous-wave operation of gallium nitride (GaN) based vertical-cavity surfaceemitting lasers (VCSELs), which was fabricated by epitaxial lateral overgrowth (ELO) using dielectric distributed Bragg reflectors(DBRs) as masks for selective growth. The device exhibited CW operation at a wavelength of 453.9nm. The maximum output power was 1.1 mW, which is the highest value reported in previously published articles. The ELO process used for this study represents a breakthrough for challenges which were indicated by other former reports for GaN-based VCSELs and is suitable for mass production.

  5. Investigation of cavity mode and excitonic transition in an InGaAs/GaAs/AlGaAs vertical-cavity surface emitting laser structure by variable-temperature micro-photoluminescence, reflectance and photomodulated reflectance

    International Nuclear Information System (INIS)

    Yu, J L; Chen, Y H; Jiang, C Y; Zhang, H Y

    2012-01-01

    Variable-temperature micro-photoluminescence (μ-PL), reflectance (R) and photomodulated reflectance (PR) have been used to study an InGaAs/GaAs/AlGaAs vertical-cavity surface emitting laser (VCSEL) structure. μ-PL and R spectra have been recorded at different temperatures between 80 K and 300 K By comparing μ-PL with R spectra, both the excitonic transition and cavity mode are clearly identified. The Variable-temperature μ-PL and PR results of the etched sample with the top distributed Bragg reflectors (DBR) being removed further confirmed our identification. Our results demonstrate that variable-temperature μ-PL is a powerful noninvasive tool to measure accurate the quantum well transition and the cavity mode alignment.

  6. Swept-source optical coherence tomography powered by a 1.3-μm vertical cavity surface emitting laser enables 2.3-mm-deep brain imaging in mice in vivo

    Science.gov (United States)

    Choi, Woo June; Wang, Ruikang K.

    2015-10-01

    We report noninvasive, in vivo optical imaging deep within a mouse brain by swept-source optical coherence tomography (SS-OCT), enabled by a 1.3-μm vertical cavity surface emitting laser (VCSEL). VCSEL SS-OCT offers a constant signal sensitivity of 105 dB throughout an entire depth of 4.25 mm in air, ensuring an extended usable imaging depth range of more than 2 mm in turbid biological tissue. Using this approach, we show deep brain imaging in mice with an open-skull cranial window preparation, revealing intact mouse brain anatomy from the superficial cerebral cortex to the deep hippocampus. VCSEL SS-OCT would be applicable to small animal studies for the investigation of deep tissue compartments in living brains where diseases such as dementia and tumor can take their toll.

  7. Systematic characterization of a 1550 nm microelectromechanical (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) with 7.92 THz tuning range for terahertz photomixing systems

    Science.gov (United States)

    Haidar, M. T.; Preu, S.; Cesar, J.; Paul, S.; Hajo, A. S.; Neumeyr, C.; Maune, H.; Küppers, F.

    2018-01-01

    Continuous-wave (CW) terahertz (THz) photomixing requires compact, widely tunable, mode-hop-free driving lasers. We present a single-mode microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) featuring an electrothermal tuning range of 64 nm (7.92 THz) that exceeds the tuning range of commercially available distributed-feedback laser (DFB) diodes (˜4.8 nm) by a factor of about 13. We first review the underlying theory and perform a systematic characterization of the MEMS-VCSEL, with particular focus on the parameters relevant for THz photomixing. These parameters include mode-hop-free CW tuning with a side-mode-suppression-ratio >50 dB, a linewidth as narrow as 46.1 MHz, and wavelength and polarization stability. We conclude with a demonstration of a CW THz photomixing setup by subjecting the MEMS-VCSEL to optical beating with a DFB diode driving commercial photomixers. The achievable THz bandwidth is limited only by the employed photomixers. Once improved photomixers become available, electrothermally actuated MEMS-VCSELs should allow for a tuning range covering almost the whole THz domain with a single system.

  8. Single-mode 850-nm vertical-cavity surface-emitting lasers with Zn-diffusion and oxide-relief apertures for > 50 Gbit/sec OOK and 4-PAM transmission

    Science.gov (United States)

    Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jyehong; Ledentsov, N. N.; Yang, Ying-Jay

    2017-02-01

    Vertical-cavity surface-emitting lasers (VCSELs) has become the most important light source in the booming market of short-reach (targeted at 56 Gbit/sec data rate per channel (CEI-56G) with the total data rate up to 400 Gbit/sec. However, the serious modal dispersion of multi-mode fiber (MMF), limited speed of VCSEL, and its high resistance (> 150 Ω) seriously limits the >50 Gbit/sec linking distance (50 Gbit/sec transmission due to that it can save one-half of the required bandwidth. Nevertheless, a 4.7 dB optical power penalty and the linearity of transmitter would become issues in the 4-PAM linking performance. Besides, in the modern OI system, the optics transreceiver module must be packaged as close as possible with the integrated circuits (ICs). The heat generated from ICs will become an issue in speed of VSCEL. Here, we review our recent work about 850 nm VCSEL, which has unique Zn-diffusion/oxide-relief apertures and special p- doping active layer with strong wavelength detuning to further enhance its modulation speed and high-temperature (85°C) performances. Single-mode (SM) devices with high-speed ( 26 GHz), reasonable resistance ( 70 Ω) and moderate output power ( 1.5 mW) can be achieved. Error-free 54 Gbit/sec OOK transmission through 1km MMF has been realized by using such SM device with signal processing techniques. Besides, the volterra nonlinear equalizer has been applied in our 4-PAM 64 Gbit/sec transmission through 2-km OM4 MMF, which significantly enhance the linearity of device and outperforms fed forward equalization (FFE) technique. Record high bit-rate distance product of 128.km is confirmed for optical-interconnect applications.

  9. Hybrid vertical cavity laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2010-01-01

    A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.......A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide....

  10. Vertical-cavity surface-emitting lasers for medical diagnosis

    DEFF Research Database (Denmark)

    Ansbæk, Thor

    and high tuning rate. The VCSEL is highly single-mode and inherently polarization stable due to the use of a High-index Contrast subwavelength Grating (HCG). HCG VCSELs are presented with 1.5% relative tuning range at a tuning rate of 850 kHz. The thesis reports on the analysis of narrow linewidth Fabry...

  11. Reliability of vertical-cavity lasers at Hewlett-Packard

    Science.gov (United States)

    Herrick, Robert W.; Lei, Chun; Keever, Mark R.; Lim, Sui F.; Deng, Hongyu; Dudley, Jim J.; Bhagat, Jay K.

    1999-04-01

    Vertical-Cavity Surface-Emitting Lasers (VCSELs) have rapidly been adopted for use in data communications modules due largely to the improvement in reliability over that of competing compact disc lasers. While very long mean lifetimes for VCSELs have been published elsewhere (> 5 X 106 h MTTF at 40C), telecommunications switching applications require further reduction in the early failure rate to meet targets of < 0.5% failures over 25 years at 50 - 70 degree(s)C. Therefore, a extensive reliability program is needed to measure both the wear-out lifetime and the random failure rate of the devices. The results of accelerated life tests will be presented, and we will discuss the methodology used to estimate the failure rate. Models of current and thermal acceleration will be presented. Degradation mechanisms observed in HP lasers will be briefly discussed. We also present preliminary results from HP oxide-aperture VCSELs.

  12. Broadband subwavelength grating mirror and its application to vertical-cavity surface-emitting laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper; Gilet, Philippe

    2008-01-01

    Various high-index-contrast sub-wavelength grating (HCG) mirror designs have been investigated. It reveals that transverse magnetic (TM-) and transverse electric (TE-) HCG reflect the incident fields in quite different ways and that the TM-HCG enables very thin gap below the grating. Based...... on these results, a new HCG VCSEL design with a thin oxide gap has been suggested. The thin oxide gap structure has a number of advantages including easier fabrication, better mechanical stability, and very strong single-mode properties....

  13. Beam Steering Analysis in Optically Phased Vertical Cavity Surface Emitting Laser Array

    Science.gov (United States)

    Xun, Meng; Sun, Yun; Xu, Chen; Xie, Yi-Yang; Jin, Zhi; Zhou, Jing-Tao; Liu, Xin-Yu; Wu, De-Xin

    2018-03-01

    Not Available Supported by the ‘Supporting First Action’ Joint Foundation for Outstanding Postdoctoral Program under Grant Nos Y7YBSH0001 and Y7BSH14001, the National Natural Science Foundation of China under Grant No 61434006, and the National Key Basic Research Program of China under Grant No 2017YFB0102302.

  14. Vertical-Cavity Surface-Emitting Lasers: Advanced Modulation Formats and Coherent Detection

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto

    transmission link with real-time demodulation. Furthermore, advanced modulation formats are considered in this thesis to expand the state-of-the-art in high-speed short-range data transmission system based on VCSELs. First, directly modulation of a VCSEL with a 4-level pulse amplitude modulation (PAM-4) signal...... at 50 Gb/s is achieved. This is the highest data rate ever transmitted with a single VCSEL at the time of this thesis work. The capacity of this system is increased to 100 Gb/s by using polarization multiplexing emulation and forward error correction techniques. Compared to a non return-to-zero on-off...

  15. Near-infrared wafer-fused vertical-cavity surface-emitting lasers for HF detection

    Czech Academy of Sciences Publication Activity Database

    Civiš, Svatopluk; Zelinger, Zdeněk; Nevrlý, V.; Dorogan, A.; Ferus, Martin; Iakovlev, V.; Sirbu, A.; Mereuta, A.; Caliman, A.; Suruceanu, G.; Kapon, E.

    2014-01-01

    Roč. 147, NOV 2014 (2014), s. 53-59 ISSN 0022-4073 R&D Projects: GA MŠk(CZ) LD14022 Grant - others:Ministerstvo financí, Centrum zahraniční pomoci(CZ) PF049 Institutional support: RVO:61388955 ; RVO:68081707 Keywords : High resolution absorption spectroscopy * Monitoring of hydrogen fluoride, methane , and ammonia * Tunable diode laser spectroscopy (TDLS) Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.645, year: 2014

  16. Broadband subwavelength grating mirror and its application to vertical-cavity surface-emitting laser

    OpenAIRE

    Chung, Il-Sug; Mørk, Jesper; Gilet, Philippe; Chelnokov, Alexei

    2008-01-01

    Various high-index-contrast sub-wavelength grating (HCG) mirror designs have been investigated. It reveals that transverse magnetic (TM-) and transverse electric (TE-) HCG reflect the incident fields in quite different ways and that the TM-HCG enables very thin gap below the grating. Based on these results, a new HCG VCSEL design with a thin oxide gap has been suggested. The thin oxide gap structure has a number of advantages including easier fabrication, better mechanical stability, and very...

  17. Theory and Modeling of Lasing Modes in Vertical Cavity Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Benjamin Klein

    1998-01-01

    modes that the VCSEL can support are then determined by matching the gain necessary for the optical system in both magnitude and phase to the gain available from the laser's electronic system. Examples are provided.

  18. All-optical 2-bit header recognition and packet switching using polarization bistable VCSELs.

    Science.gov (United States)

    Hayashi, Daisuke; Nakao, Kazuya; Katayama, Takeo; Kawaguchi, Hitoshi

    2015-04-06

    We propose and evaluate an all-optical 2-bit header recognition and packet switching method using two 1.55-µm polarization bistable vertical-cavity surface-emitting lasers (VCSELs) and three optical switches. Polarization bistable VCSELs acted as flip-flop devices by using AND-gate operations of the header and set pulses, together with the reset pulses. Optical packets including 40-Gb/s non-return-to-zero pseudo-random bit-sequence payloads were successfully sent to one of four ports according to the state of two bits in the headers with a 4-bit 500-Mb/s return-to-zero format. The input pulse powers were 17.2 to 31.8 dB lower than the VCSEL output power. We also examined an extension of this method to multi-bit header recognition and packet switching.

  19. High-Q, Low-Threshold Monolithic Perovskite Thin-Film Vertical-Cavity Lasers.

    Science.gov (United States)

    Chen, Songtao; Zhang, Cheng; Lee, Joonhee; Han, Jung; Nurmikko, Arto

    2017-04-01

    A vertical-cavity surface-emitting perovskite laser is achieved using a microcavity configuration where CH 3 NH 3 PbI 3 thin solid films are embedded within a custom GaN-based high-quality (Q-factor) resonator. This single-mode perovskite laser reaches a low threshold (≈7.6 µJ cm -2 ) at room temperature and emits spatially coherent Gaussian laser beams. The devices allow direct access to the study of perovskite gain dynamics and material robustness. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Submonolayer Quantum Dots for High Speed Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Zakharov ND

    2007-01-01

    Full Text Available AbstractWe report on progress in growth and applications of submonolayer (SML quantum dots (QDs in high-speed vertical-cavity surface-emitting lasers (VCSELs. SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers. Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting lasers (VCSELs is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than 10−12has been achieved in a temperature range 25–85 °Cwithout current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission.

  1. Low-frequency fluctuations in vertical cavity lasers: Experiments versus Lang-Kobayashi dynamics

    International Nuclear Information System (INIS)

    Torcini, Alessandro; Barland, Stephane; Giacomelli, Giovanni; Marin, Francesco

    2006-01-01

    The limits of applicability of the Lang-Kobayashi (LK) model for a semiconductor laser with optical feedback are analyzed. The model equations, equipped with realistic values of the parameters, are investigated below the solitary laser threshold where low-frequency fluctuations (LFF's) are usually observed. The numerical findings are compared with experimental data obtained for the selected polarization mode from a vertical cavity surface emitting laser (VCSEL) subject to polarization selective external feedback. The comparison reveals the bounds within which the dynamics of the LK model can be considered as realistic. In particular, it clearly demonstrates that the deterministic LK model, for realistic values of the linewidth enhancement factor α, reproduces the LFF's only as a transient dynamics towards one of the stationary modes with maximal gain. A reasonable reproduction of real data from VCSEL's can be obtained only by considering the noisy LK or alternatively deterministic LK model for extremely high α values

  2. Investigation of single-mode vertical-cavity surface-emitting lasers with graphene-bubble dielectric DBR

    Science.gov (United States)

    Guan, Baolu; Li, Pengtao; Arafin, Shamsul; Alaskar, Yazeed; Wang, Kang L.

    2018-02-01

    An inter-cavty contact single mode 850 nm VCSEL was fabricated with a graphene assisted self-assembly curved dielectric bubble Bragg mirror for the first time. Taking the advantage of graphene's uniform low surface energy, the low cost dielectric bubble DBR (Si3N4/SiO2) was deposited on top of the graphene/half-VCSEL structure via van der Waals Force (vdWF) without using any additional spacing elements and sacrificial layer release-etch process. The continuous-wave operating VCSELs with an aperture diameter of 7 μm exhibit single-mode output power of more than 1 mW with a slope efficiency of 0.2 W/A. The sidemode suppression ratios are >40 dB. This novel modification into the lasers can also be applied to a variety of other optoelectronic devices, such as resonance photodetecter and super narrow linewidth VCSEL.

  3. Thermal lensing effects on lateral leakage in GaN-based vertical-cavity surface-emitting laser cavities.

    Science.gov (United States)

    Hashemi, Ehsan; Bengtsson, Jörgen; Gustavsson, Johan; Calciati, Marco; Goano, Michele; Haglund, Åsa

    2017-05-01

    Lateral leakage of light has been identified as a detrimental loss source in many suggested and experimentally realized GaN-based VCSELs. In the present work we include thermal effects to realistically account for the substantial Joule heating in these devices. In contrast to what could be expected from the previous results, the induced thermal lensing does not make antiguided cavities more positively guided, so that they approach the unguided regime with extremely high lateral leakage. Rather, thermal lensing strongly suppresses lateral leakage for both antiguided and guided cavities. This is explained in terms of lowered launch of power from the central part of the cavity and/or lower total internal reflection in the peripheral part; the former effect is active in all cavities whereas the latter only contributes to the very strongly reduced leakage in weakly antiguided cavities. Thermal lensing suppresses lateral leakage both for the fundamental and the first higher order mode, but a strong modal discrimination is still achieved for the antiguided cavities. Thus, strongly antiguided cavities could be used to achieve single-mode devices, but at the cost of slightly higher threshold gain and stronger temperature dependent performance characteristics.

  4. Flattop mode shaping of a vertical cavity surface emitting laser using an external-cavity aspheric mirror.

    Science.gov (United States)

    Yang, Zhaohui; Leger, James

    2004-11-01

    Both square-shaped and circular-shaped flattop modes were experimentally demonstrated in extended-cavity broad-area VCSELs using aspheric feedback mirrors. These refractive aspheric mirrors were fabricated by electron-beam lithography on curved substrates. Excellent single-mode operation and improved power extraction efficiency were observed. The three-mirror structure of the VCSEL and the state-of-the-art fabrication of the aspheric mirror contribute to the superior VCSEL performance. The modal loss analysis using a rigid three-mirror-cavity simulation method is discussed.

  5. Vertical-Cavity In-plane Heterostructures: Physics and Applications

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2015-01-01

    We show that the in-plane heterostructures realized in vertical cavities with high contrast grating(HCG) reflector enables exotic configurations of heterostructure and photonic wells. In photonic crystal heterostructures forming a photonic well, the property of a confined mode is determined by th...

  6. Vertical-cavity laser with a novel grating mirror

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol

    Hybrid III-V on silicon (Si) ‘vertical cavity lasers’ (hybrid VCLs), which can emit light laterally into a Si waveguide, are fabricated and investigated. The Si-integrated hybrid VCL consists of a top dielectric Bragg reflector (DBR), a III-V active layer, and a bottom high contrast grating (HCG...... VCLs have been fabricated. The first version of hybrid VCL is designed for demonstrating in-plane emission into a Si waveguide. The in-plane emission is enabled by the bottom HCG abutting the Si waveguide, which not only functions as a highly reflective mirror but also routes the light from...... dispersion has been observed and discussed, which is unique for HCG-based vertical cavities. The second version proves the potential for high-speed operation of hybrid VCL structure. In the hybrid VCL structure, the effective cavity length is substantially reduced by using a dielectric DBR and a TM-HCG...

  7. Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon (Open Access Publisher’s Version)

    Science.gov (United States)

    2016-01-04

    beam shape, catastrophic optical damage free, and two-dimensional integration capabilities with CMOS electronics , vertical-cavity surface-emitting...longitudinal and transverse mode over a large lasing area , narrow linewidth, high power output, small beam divergence angle, polarization control...crystal lasers—ultimate nanolasers and broad - area coherent lasers [Invited]. J. Opt. Soc. Am. B 27, B1–B8 (2010). 13. Painter, O. et al. Two-dimensional

  8. Broad tunable photonic microwave generation based on period-one dynamics of optical injection vertical-cavity surface-emitting lasers.

    Science.gov (United States)

    Ji, Songkun; Hong, Yanhua; Spencer, Paul S; Benedikt, Johannes; Davies, Iwan

    2017-08-21

    Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has been study experimentally. The results have shown that the frequency of the generated microwave signal can be broadly tunable through the adjustment of the injection power and the frequency detuning. Strong optical injection power and higher frequency detuning are favorable for obtaining a high frequency microwave signal. These results are similar to those found in systems based on distributed feedback lasers and quantum dot lasers. The variation of the microwave power at the fundamental frequency and the second-harmonic distortion have also been characterized.

  9. Non-paraxial contributions to the far-field pattern of surface-emitting lasers: a manifestation of the momentum-space wavefunctions of quantum billiards

    International Nuclear Information System (INIS)

    Yu, Y T; Huang, Y J; Chiang, P Y; Lin, Y C; Huang, K F; Chen, Y F

    2011-01-01

    We investigated experimentally non-paraxial contributions to the high-order far-field pattern of large-area vertical-cavity surface-emitting lasers in order to explore by analogy the momentum-space wave distributions of quantum billiards. Our results reveal that non-paraxial contributions significantly influence the morphology of the high-order far-field pattern. A fast reliable method is developed for transforming the experimental far-field patterns to the correct Fourier transform of the corresponding near-field lasing modes. In this way we visualize the momentum-space (p–q) wavefunctions of quantum billiards

  10. III-V/SOI vertical cavity laser structure for 120 Gbit/s speed

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Mørk, Jesper

    2015-01-01

    Ultrashort-cavity structure for III-V/SOI vertical cavity laser with light output into a Si waveguide is proposed, enabling 17 fJ/bit efficiency or 120 Gbit/s speed. Experimentally, 27-GHz bandwidth is demonstrated at 3.5 times of threshold. © 2015 OSA.......Ultrashort-cavity structure for III-V/SOI vertical cavity laser with light output into a Si waveguide is proposed, enabling 17 fJ/bit efficiency or 120 Gbit/s speed. Experimentally, 27-GHz bandwidth is demonstrated at 3.5 times of threshold. © 2015 OSA....

  11. Efficient quality-eactor estimation of a vertical cavity employing a high-contrast grating

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2017-01-01

    Hybrid vertical cavity lasers employing high-contrast grating reflectors are attractive for Si-integrated light source applications. Here, a method for reducing a three-dimensional (3D) optical simulation of this laser structure to lower-dimensional simulations is suggested, which allows for very...

  12. Numerical Investigation of Vertical Cavity Lasers With High-Contrast Gratings Using the Fourier Modal Method

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2016-01-01

    We explore the use of a modal expansion technique, Fourier modal method (FMM), for investigating the optical properties of vertical cavities employing high-contrast gratings (HCGs). Three techniques for determining the resonance frequency and quality factor (Q-factor) of a cavity mode are compared...

  13. Dynamical dispersion engineering in coupled vertical cavities employing a high-contrast grating

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Chung, Il-Sug

    2017-01-01

    strength. This can be implemented by employing a high-contrast grating (HCG) as the coupling reflector in a system of two coupled vertical cavities, and engineering both the HCG reflection phase and amplitude response. Several examples of HCG-based coupled cavities with novel features are discussed...

  14. Hybrid vertical-cavity laser with lateral emission into a silicon waveguide

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Taghizadeh, Alireza

    2015-01-01

    We experimentally demonstrate an optically-pumped III-V/Si vertical-cavity laser with lateral emission into a silicon waveguide. This on-chip hybrid laser comprises a distributed Bragg reflector, a III-V active layer, and a high-contrast grating reflector, which simultaneously funnels light...

  15. III-V/SOI vertical cavity laser with in-plane output into a Si waveguide

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Semenova, Elizaveta

    2015-01-01

    We experimentally demonstrate an optically-pumped III-V-on-SOI hybrid vertical-cavity laser that outputs light into an in-plane Si waveguide, using CMOS-compatible processes. The laser operates at 1.49 $\\mu$m with a side-mode suppression-ratio of 27 dB and has a similar threshold as long-waveleng......We experimentally demonstrate an optically-pumped III-V-on-SOI hybrid vertical-cavity laser that outputs light into an in-plane Si waveguide, using CMOS-compatible processes. The laser operates at 1.49 $\\mu$m with a side-mode suppression-ratio of 27 dB and has a similar threshold as long...

  16. Surface emitting ring quantum cascade lasers for chemical sensing

    Science.gov (United States)

    Szedlak, Rolf; Hayden, Jakob; Martín-Mateos, Pedro; Holzbauer, Martin; Harrer, Andreas; Schwarz, Benedikt; Hinkov, Borislav; MacFarland, Donald; Zederbauer, Tobias; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Acedo, Pablo; Lendl, Bernhard; Strasser, Gottfried

    2018-01-01

    We review recent advances in chemical sensing applications based on surface emitting ring quantum cascade lasers (QCLs). Such lasers can be implemented in monolithically integrated on-chip laser/detector devices forming compact gas sensors, which are based on direct absorption spectroscopy according to the Beer-Lambert law. Furthermore, we present experimental results on radio frequency modulation up to 150 MHz of surface emitting ring QCLs. This technique provides detailed insight into the modulation characteristics of such lasers. The gained knowledge facilitates the utilization of ring QCLs in combination with spectroscopic techniques, such as heterodyne phase-sensitive dispersion spectroscopy for gas detection and analysis.

  17. Theoretical Investigation of Subwavelength Gratings and Vertical Cavity Lasers Employing Grating Structures

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza

    . Though both sides of the grating layer are not surrounded by low refractive-index materials as in high-index-contrast gratings (HCGs), the HG can provide a near-unity reflectivity over a broader wavelength range than HCGs, or work as a resonator with a quality (Q) factor as high as 109. The physics...... behind these reflector and resonator properties are studied thoroughly. A HG structure comprising a III-V cap layer with a gain material and a Si grating layer enables the realization of a compact vertical cavity laser integrated on Si platform, which has a superior thermal property and fabrication......-factor is investigated, which shows that the uncertainty in the Q-factor can be several orders of magnitude larger than the uncertainty in the resonance frequency. Next, the HG is shown to possess a near-unity reflectivity in a broad wavelength range, which can be broader than the HCG, since the cap layer introduces...

  18. Continuous-wave optically pumped green perovskite vertical-cavity surface-emitter

    KAUST Repository

    Alias, Mohd Sharizal

    2017-09-11

    We report an optically pumped green perovskite vertical-cavity surface-emitter operating in continuous-wave (CW) with a power density threshold of ~89 kW/cm2. The device has an active region of CH3NH3PbBr3 embedded in a dielectric microcavity; this feat was achieved with a combination of optimal spectral alignment of the optical cavity modes with the perovskite optical gain, an adequate Q-factor of the microcavity, adequate thermal stability, and improved material quality with a smooth, passivated, and annealed thin active layer. Our results signify a way towards efficient CW perovskite emitter operation and electrical injection using low-cost fabrication methods for addressing monolithic optoelectronic integration and lasing in the green gap.

  19. Cascadable all-optical inverter based on a nonlinear vertical-cavity semiconductor optical amplifier.

    Science.gov (United States)

    Zhang, Haijiang; Wen, Pengyue; Esener, Sadik

    2007-07-01

    We report, for the first time to our knowledge, the operation of a cascadable, low-optical-switching-power(~10 microW) small-area (~100 microm(2)) high-speed (80 ps fall time) all-optical inverter. This inverter employs cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics of an electrically pumped vertical-cavity semiconductor optical amplifier (VCSOA). The measured transfer characteristics of such an optical inverter resemble those of standard electronic metal-oxide semiconductor field-effect transistor-based inverters exhibiting high noise margin and high extinction ratio (~9.3 dB), making VCSOAs an ideal building block for all-optical logic and memory.

  20. Final report on LDRD project: Semiconductor surface-emitting microcavity laser spectroscopy for analysis of biological cells and microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Gourley, P.L.; McDonald, A.E. [Sandia National Labs., Albuquerque, NM (United States). Nanostructure and Semiconductor Physics Dept.; Gourley, M.F. [Washington Hospital Center, DC (United States); Bellum, J. [Coherent Technologies, Boulder, CO (United States)

    1997-08-01

    This article discusses a new intracavity laser technique that uses living or fixed cells as an integral part of the laser. The cells are placed on a GaAs based semiconductor wafer comprising one half of a vertical cavity surface-emitting laser. After placement, the cells are covered with a dielectric mirror to close the laser cavity. When photo-pumped with an external laser, this hybrid laser emits coherent light images and spectra that depend sensitively on the cell size, shape, and dielectric properties. The light spectra can be used to identify different cell types and distinguish normal and abnormal cells. The laser can be used to study single cells in real time as a cell-biology lab-on-a-chip, or to study large populations of cells by scanning the pump laser at high speed. The laser is well-suited to be integrated with other micro-optical or micro-fluidic components to lead to micro-optical-mechanical systems for analysis of fluids, particulates, and biological cells.

  1. Optical Design of Dilute Nitride Quantum Wells Vertical Cavity Semiconductor Optical Amplifiers for Communication Systems

    Directory of Open Access Journals (Sweden)

    Faten A. Chaqmaqchee

    2016-04-01

    Full Text Available III-V semiconductors components such as Gallium Arsenic (GaAs, Indium Antimony (InSb, Aluminum Arsenic (AlAs and Indium Arsenic (InAs have high carrier mobilities and direct energy gaps. This is making them indispensable for today’s optoelectronic devices such as semiconductor lasers and optical amplifiers at 1.3 μm wavelength operation. In fact, these elements are led to the invention of the Gallium Indium Nitride Arsenic (GaInNAs, where the lattice is matched to GaAs for such applications. This article is aimed to design dilute nitride GaInNAs quantum wells (QWs enclosed between top and bottom of Aluminum (Gallium Arsenic Al(GaAs distributed bragg mirrors (DBRs using MATLAB® program. Vertical cavity semiconductor optical amplifiers (VCSOAs structures are based on Fabry Perot (FP method to design optical gain and bandwidth gain to be operated in reflection and transmission modes. The optical model gives access to the contact layer of epitaxial structure and the reflectivity for successive radiative modes, their lasing thresholds, emission wavelengths and optical field distributions in the laser cavity.

  2. Near Field and Far Field Effects in the Taguchi-Optimized Design of AN InP/GaAs-BASED Double Wafer-Fused Mqw Long-Wavelength Vertical-Cavity Surface-Emitting Laser

    Science.gov (United States)

    Menon, P. S.; Kandiah, K.; Mandeep, J. S.; Shaari, S.; Apte, P. R.

    Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchi's orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchi's orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

  3. Development of III-Sb metamorphic DBR membranes on InP for vertical cavity laser applications

    Science.gov (United States)

    Addamane, S. J.; Mansoori, A.; Renteria, E. J.; Dawson, N.; Shima, D. M.; Rotter, T. J.; Hains, C. P.; Dawson, L. R.; Balakrishnan, G.

    2016-04-01

    Sb-based metamorphic DBR membranes are developed for InP-based vertical cavity laser applications. The reflectivity of the metamorphic DBR membrane is compared to the reflectivity of a lattice-matched DBR to characterize the optical quality of the DBR membrane. The metamorphic interface between InP and the III-antimonides is found to degrade the reflectivity of the DBR. Therefore, the growth temperature for the metamorphic DBR is optimized in order to obtain highly reflective (>99.8%) III-Sb thin-film membranes.

  4. Commercial mode-locked vertical external cavity surface emitting lasers

    Science.gov (United States)

    Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

    2017-02-01

    In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

  5. 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...

  6. Modeling of circular-grating surface-emitting lasers

    Science.gov (United States)

    Shams-Zadeh-Amiri, Ali M.

    Grating-coupled surface-emitting lasers became an area of growing interest due to their salient features. Emission from a broad area normal to the wafer surface, makes them very well suited in high power applications and two- dimensional laser arrays. These new possibilities have caused an interest in different geometries to fully develop their potential. Among them, circular-grating lasers have the additional advantage of producing a narrow beam with a circular cross section. This special feature makes them ideal for coupling to optical fibers. All existing theoretical models dealing with circular- grating lasers only consider first-order gratings, or second-order gratings, neglecting surface emission. In this thesis, the emphasis is to develop accurate models describing the laser performance by considering the radiation field. Toward this aim, and due to the importance of the radiation modes in surface-emitting structures, a theoretical study of these modes in multilayer planar structures has been done in a rigorous and systematic fashion. Problems like orthogonality of the radiation modes have been treated very accurately. We have considered the inner product of radiation modes using the distribution theory. Orthogonality of degenerate radiation modes is an important issue. We have examined its validity using the transfer matrix method. It has been shown that orthogonality of degenerate radiation modes in a very special case leads to the Brewster theorem. In addition, simple analytical formulas for the normalization of radiation modes have been derived. We have shown that radiation modes can be handled in a much easier way than has been thought before. A closed-form spectral dyadic Green's function formulation of multilayer planar structures has been developed. In this formulation, both rectangular and cylindrical structures can be treated within the same mathematical framework. The Hankel transform of some auxiliary functions defined on a circular aperture has

  7. Hybrid III-V/SOI single-mode vertical-cavity laser with in-plane emission into a silicon waveguide

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Semenova, Elizaveta

    2015-01-01

    We report a III-V-on-SOI vertical-cavity laser emitting into an in-plane Si waveguide fabricated by using CMOS-compatible processes. The fabricated laser operates at 1.54 µm with a SMSR of 33 dB and a low threshold.......We report a III-V-on-SOI vertical-cavity laser emitting into an in-plane Si waveguide fabricated by using CMOS-compatible processes. The fabricated laser operates at 1.54 µm with a SMSR of 33 dB and a low threshold....

  8. Linearly Polarized Dual-Wavelength Vertical-External-Cavity Surface-Emitting Laser (Postprint)

    National Research Council Canada - National Science Library

    Fan, Li; Fallahi, Mahmoud; Hader, Joerg; Zakharian, Aramais R; Moloney, Jerome V; Stolz, Wolfgang; Koch, Stephan W; Bedford, Robert; Murray, James T

    2007-01-01

    The authors demonstrate the multiwatt linearly polarized dual-wavelength operation in an optically pumped vertical-external-cavity surface-emitting laser by means of an intracavity tilted Fabry-Perot...

  9. Vertical cavity laser

    DEFF Research Database (Denmark)

    2016-01-01

    of refraction of high-index sections of the grating structure is at least 2.5, and wherein an index of refraction of low-index sections of the grating structure is less than 2, the core grating region defining a projection in a direction normal to the grating layer; a cap layer having a first side and having...

  10. 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.

  11. 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)

  12. 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.

  13. 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.

  14. Bistable Mechanisms for Space Applications

    Science.gov (United States)

    Zirbel, Shannon A.; Tolman, Kyler A.; Trease, Brian P.

    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. PMID:28030588

  15. 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.

  16. THz wave parametric oscillator with a surface-emitted ring-cavity configuration

    Science.gov (United States)

    Yang, Zhen; Wang, Yuye; Xu, Degang; Tang, Longhuang; Xu, Wentao; Duan, Pan; Yan, Chao; Yao, Jianquan

    2016-11-01

    A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning. Through the special optical design with a Galvano optical scanner and four-mirror ring-cavity structure, a maximum THz output of 12.9 μJ/pulse is achieved at 1.359 THz under the pump pulse energy of 172.8 mJ with the repetition rate of 10 Hz. A further research on the performance of the SE ring-cavity TPO has done to explore more characteristics of THz output. The THz pulse instability and the influence of cavity loss has analyzed. Moreover, the pump depletion rate of the ring-cavity configuration is much lower than the conventional surface-emitted terahertz wave parametric oscillator at the same experimental conditions.

  17. High-energy terahertz wave parametric oscillator with a surface-emitted ring-cavity configuration.

    Science.gov (United States)

    Yang, Zhen; Wang, Yuye; Xu, Degang; Xu, Wentao; Duan, Pan; Yan, Chao; Tang, Longhuang; Yao, Jianquan

    2016-05-15

    A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning in a wide frequency range. Through the special optical design with a galvano-optical scanner and four-mirror ring-cavity structure, the maximum THz wave output energy of 12.9 μJ/pulse is achieved at 1.359 THz under the pump energy of 172.8 mJ. The fast THz frequency tuning in the range of 0.7-2.8 THz can be accessed with the step response of 600 μs. Moreover, the maximum THz wave output energy from this configuration is 3.29 times as large as that obtained from the conventional surface-emitted THz wave parametric oscillator with the same experimental conditions.

  18. 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

  19. 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.

  20. 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...

  1. 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

  2. 2 W high efficiency PbS mid-infrared surface emitting laser

    Science.gov (United States)

    Ishida, A.; Sugiyama, Y.; Isaji, Y.; Kodama, K.; Takano, Y.; Sakata, H.; Rahim, M.; Khiar, A.; Fill, M.; Felder, F.; Zogg, H.

    2011-09-01

    High efficiency laser operation with output power exceeding 2 W was obtained for vertical external-cavity PbS based IV-VI compound surface emitting quantum-well structures. The laser showed external quantum efficiency as high as 16%. Generally, mid-infrared III-V or II-VI semiconductor laser operation utilizing interband electron transitions are restricted by Auger recombination and free carrier absorption. Auger recombination is much lower in the IV-VI semiconductors, and the free-carrier absorption is significantly reduced by an optically pumped laser structure including multi-step optical excitation layers.

  3. 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

  4. 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.

  5. 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

    2018-02-02

    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.

  6. 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.

  7. 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

  8. 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

  9. Continuously tunable monomode mid-infrared vertical external cavity surface emitting laser on Si

    Science.gov (United States)

    Khiar, A.; Rahim, M.; Fill, M.; Felder, F.; Hobrecker, F.; Zogg, H.

    2010-10-01

    A tunable PbTe based mid-infrared vertical external cavity surface emitting laser is described. The active part is a ˜1 μm thick PbTe layer grown epitaxially on a Bragg mirror on the Si-substrate. The cavity is terminated with a curved Si/SiO Bragg top mirror and pumped optically with a 1.55 μm laser. Cavity length is <100 μm in order that only one longitudinal mode is supported. By changing the cavity length, up to 5% wavelength continuous and mode-hop free tuning is achieved at fixed temperature. The total tuning extends from 5.6 to 4.7 μm at 100-170 K operation temperature.

  10. Functionally rigid bistable [2]rotaxanes

    DEFF Research Database (Denmark)

    Nygaard, Sune; Leung, Ken C-F; Aprahamian, Ivan

    2007-01-01

    was investigated as a means to simplify both molecular structure and switching function previously observed in related bistable [2]rotaxanes with flexible spacers between their stations and incorporating a cyclobis(paraquat-p-phenylene) (CBPQT4+) ring. The nondegenerate MPTTF-NP switch was isolated as near isomer......-free bistable [2]rotaxane. Utilization of MPTTF removes the cis/trans isomerization that characterizes the tetrathiafulvalene (TTF) parent core structure. Furthermore, only one translational isomer is observed (> 95 ... component resides, to all intents and purposes, predominantly on the MPTTF unit in the ground state. As a consequence of these two effects, the assignment of NMR and UV-vis data is more simplified as compared to previous donor-acceptor bistable [2]rotaxanes. This development has not only allowed for much...

  11. 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

  12. 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.

  13. 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.

  14. Design of photonic crystal surface emitting lasers with indium-tin-oxide top claddings

    Science.gov (United States)

    Huang, Shen-Che; Hong, Kuo-Bin; Chiu, Han-Lun; Lan, Shao-Wun; Chang, Tsu-Chi; Li, Heng; Lu, Tien-Chang

    2018-02-01

    Electrically pumped GaAs-based photonic crystal surface emitting lasers were fabricated using a simple fabrication process by directly capping the indium-tin-oxide transparent conducting thin film as the top cladding layer upon a photonic crystal layer. Optimization of the separate-confinement heterostructures of a laser structure is crucial to improving characteristics by providing advantageous optical confinements. The turn-on voltage, series resistance, threshold current, and slope efficiency of the laser with a 100 × 100 μm2 photonic crystal area operated at room temperature were 1.3 V, 1.5 Ω, 121 mA, and 0.2 W/A, respectively. Furthermore, we demonstrated a single-lobed lasing wavelength of 928.6 nm at 200 mA and a wavelength redshift rate of 0.05 nm/K in temperature-dependent measurements. The device exhibited the maximum output power of approximately 400 mW at an injection current of 2 A; moreover, divergence angles of less than 1° for the unpolarized circular-shaped laser beam were measured at various injection currents. Overall, the low threshold current, excellent beam quality, small divergence, high output power, and high-operating-temperature (up to 343 K) of our devices indicate that they can potentially fill the requirements for next-generation light sources and optoelectronic devices.

  15. Hybrid Vertical-Cavity Laser

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention provides a light source (2) for light circuits on a silicon platform (3). A vertical laser cavity is formed by a gain region (101) arranged between a top mirror (4) and a bottom grating-mirror (12) in a grating region (11) in a silicon layer (10) on a substrate. A waveguide ...

  16. Photodegradation and polarization properties of vertical external surface-emitting organic laser

    International Nuclear Information System (INIS)

    Leang, Tatiana

    2014-01-01

    Although organic solid-state dye lasers can provide wavelength tunability in the whole visible spectrum and offers perspectives of low-cost compact lasers, they are still limited by several drawbacks, especially photodegradation. The geometry of a Vertical External Cavity Surface-emitting Organic Laser (VECSOL) enables organic lasers to reach high energies, excellent conversion efficiencies and good beam quality, it also enables an external control on many parameters, a feature that we have used here to study the photodegradation phenomenon as well as some polarization properties of organic solid-state lasers. In the first part of this thesis, we studied the lifetime of the laser upon varying several parameters (pump pulse-width, repetition rate, output coupling,...) and we found that the intracavity laser intensity, independently of the pump intensity, had a major on photodegradation rate. Moreover, we observed that the profile of the laser beam was also degrading with time: while it is Gaussian in the beginning it gradually shifts to an annular shape. In the second part, we investigated the polarization properties of VECSOLs, with a special emphasis on fluorescence properties of some typical dyes used in lasers. The crucial role played by resonant non-radiative energy transfers between dye molecules (HOMO-FRET) is evidenced and enables explaining the observed fluorescence depolarization, compared to the expected limiting fluorescence anisotropy. Energy transfers happen to play a negligible role above laser threshold, as the organic laser beam is shown to be linearly polarized in a wide range of experimental conditions when excitation occurs in the first singlet state. (author) [fr

  17. 5-μm vertical external-cavity surface-emitting laser (VECSEL) for spectroscopic applications

    Science.gov (United States)

    Rahim, M.; Khiar, A.; Felder, F.; Fill, M.; Zogg, H.; Sigrist, M. W.

    2010-08-01

    Mid-IR tunable VECSELs (Vertical External-Cavity Surface-Emitting Lasers) emitting at 4-7 μm wavelengths and suitable for spectroscopic sensing applications are described. They are realized with lead-chalcogenide (IV-VI) narrow band gap materials. The active part, a single 0.6-2-μm thick PbTe or PbSe gain layer, is grown onto an epitaxial Bragg mirror consisting of two or three Pb1- y Eu y Te/BaF2 quarter-wavelength layer pairs. All layers are deposited by MBE in a single run employing a BaF2 or Si substrate, no further processing is needed. The cavity is completed with an external curved top mirror, which is again realized with an epitaxial Bragg structure. Pumping is performed optically with a 1.5-μm laser. Maximum output power for pulsed operation is currently up to >1 Wp at -173°C and >10 mW at 10°C. In continuous wave (CW) operation, 18 mW at 100 K are reached. Still higher operating temperatures and/or powers are expected with better heat-removal structures and better designs employing QW (Quantum-Wells). Advantages of mid-IR VECSELs compared to edge-emitting lasers are their very good beam quality (circular beam with 15 μm are accessible with Pb1- y X y Z (X=Sr, Eu, Sn, Z=Se, Te) and/or including QW.

  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. 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)

  20. 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

  1. 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/

  2. Bistability in biochemical signaling models.

    Science.gov (United States)

    Sobie, Eric A

    2011-09-20

    This Teaching Resource provides lecture notes, slides, and a student assignment for a two-part lecture on the principles underlying bistability in biochemical signaling networks, which are illustrated with examples from the literature. The lectures cover analog, or graded, versus digital, all-or-none, responses in cells, with examples from different types of biological processes requiring each. Rate-balance plots are introduced as a method for determining whether generic one-variable systems exhibit one or several stable steady states. Bifurcation diagrams are presented as a more general method for detecting the presence of bistability in biochemical signaling networks. The examples include an artificial toggle switch, the lac operon in bacteria, and the mitogen-activated protein kinase cascade in both Xenopus oocytes and mammalian cells. The second part of the lecture links the concepts of bistability more closely to the mathematical tools provided by dynamical systems analysis. The examples from the first part of the lecture are analyzed with phase-plane techniques and bifurcation analysis, using the scientific programming language MATLAB. Using these programs as a template, the assignment requires the students to implement a model from the literature and analyze the stability of this model's steady states.

  3. 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.

  4. The smallest chemical reaction system with bistability

    Directory of Open Access Journals (Sweden)

    Wilhelm Thomas

    2009-09-01

    Full Text Available Abstract Background Bistability underlies basic biological phenomena, such as cell division, differentiation, cancer onset, and apoptosis. So far biologists identified two necessary conditions for bistability: positive feedback and ultrasensitivity. Results Biological systems are based upon elementary mono- and bimolecular chemical reactions. In order to definitely clarify all necessary conditions for bistability we here present the corresponding minimal system. According to our definition, it contains the minimal number of (i reactants, (ii reactions, and (iii terms in the corresponding ordinary differential equations (decreasing importance from i-iii. The minimal bistable system contains two reactants and four irreversible reactions (three bimolecular, one monomolecular. We discuss the roles of the reactions with respect to the necessary conditions for bistability: two reactions comprise the positive feedback loop, a third reaction filters out small stimuli thus enabling a stable 'off' state, and the fourth reaction prevents explosions. We argue that prevention of explosion is a third general necessary condition for bistability, which is so far lacking discussion in the literature. Moreover, in addition to proving that in two-component systems three steady states are necessary for bistability (five for tristability, etc., we also present a simple general method to design such systems: one just needs one production and three different degradation mechanisms (one production, five degradations for tristability, etc.. This helps modelling multistable systems and it is important for corresponding synthetic biology projects. Conclusion The presented minimal bistable system finally clarifies the often discussed question for the necessary conditions for bistability. The three necessary conditions are: positive feedback, a mechanism to filter out small stimuli and a mechanism to prevent explosions. This is important for modelling bistability with

  5. 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)

  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. 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...

  8. Highly Selective Volatile Organic Compounds Breath Analysis Using a Broadly-Tunable Vertical-External-Cavity Surface-Emitting Laser.

    Science.gov (United States)

    Tuzson, Béla; Jágerská, Jana; Looser, Herbert; Graf, Manuel; Felder, Ferdinand; Fill, Matthias; Tappy, Luc; Emmenegger, Lukas

    2017-06-20

    A broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) is employed in a direct absorption laser spectroscopic setup to measure breath acetone. The large wavelength coverage of more than 30 cm -1 at 3.38 μm allows, in addition to acetone, the simultaneous measurement of isoprene, ethanol, methanol, methane, and water. Despite the severe spectral interferences from water and alcohols, an unambiguous determination of acetone is demonstrated with a precision of 13 ppbv that is achieved after 5 min averaging at typical breath mean acetone levels in synthetic gas samples mimicking human breath.

  9. 4.5 μm wavelength vertical external cavity surface emitting laser operating above room temperature

    Science.gov (United States)

    Rahim, M.; Khiar, A.; Felder, F.; Fill, M.; Zogg, H.

    2009-05-01

    A midinfrared vertical external cavity surface emitting laser with 4.5 μm emission wavelength and operating above room temperature has been realized. The active part consists of a single 850 nm thick epitaxial PbSe gain layer. It is followed by a 2 1/2 pair Pb1-yEuyTe/BaF2 Bragg mirror. No microstructural processing is needed. Excitation is done optically with a 1.5 μm wavelength laser. The device operates up to 45 °C with 100 ns pulses and delivers 6 mW output power at 27 °C heat-sink temperature.

  10. 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.

  11. Surface Emitting, High Efficiency Near-Vacuum Ultraviolet Light Source with Aluminum Nitride Nanowires Monolithically Grown on Silicon.

    Science.gov (United States)

    Zhao, S; Djavid, M; Mi, Z

    2015-10-14

    To date, it has remained challenging to realize electrically injected light sources in the vacuum ultraviolet wavelength range (∼200 nm or shorter), which are important for a broad range of applications, including sensing, surface treatment, and photochemical analysis. In this Letter, we have demonstrated such a light source with molecular beam epitaxially grown aluminum nitride (AlN) nanowires on low cost, large area Si substrate. Detailed angle dependent electroluminescence studies suggest that, albeit the light is TM polarized, the dominant light emission direction is from the nanowire top surface, that is, along the c axis, due to the strong light scattering effect. Such an efficient surface emitting device was not previously possible using conventional c-plane AlN planar structures. The AlN nanowire LEDs exhibit an extremely large electrical efficiency (>85%), which is nearly ten times higher than the previously reported AlN planar devices. Our detailed studies further suggest that the performance of AlN nanowire LEDs is predominantly limited by electron overflow. This study provides important insight on the fundamental emission characteristics of AlN nanowire LEDs and also offers a viable path to realize an efficient surface emitting near-vacuum ultraviolet light source through direct electrical injection.

  12. 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

  13. 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.

  14. Resonant activation in bistable semiconductor lasers

    International Nuclear Information System (INIS)

    Lepri, Stefano; Giacomelli, Giovanni

    2007-01-01

    We theoretically investigate the possibility of observing resonant activation in the hopping dynamics of two-mode semiconductor lasers. We present a series of simulations of a rate-equation model under random and periodic modulation of the bias current. In both cases, for an optimal choice of the modulation time scale, the hopping times between the stable lasing modes attain a minimum. The simulation data are understood by means of an effective one-dimensional Langevin equation with multiplicative fluctuations. Our conclusions apply to both edge-emitting and vertical cavity lasers, thus opening the way to several experimental tests in such optical systems

  15. 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.

  16. Lead-chalcogenide mid-infrared vertical external cavity surface emitting lasers with improved threshold: Theory and experiment

    Science.gov (United States)

    Fill, Matthias; Debernardi, Pierluigi; Felder, Ferdinand; Zogg, Hans

    2013-11-01

    Mid-infrared Vertical External Cavity Surface Emitting Lasers (VECSEL) based on narrow gap lead-chalcogenide (IV-VI) semiconductors exhibit strongly reduced threshold powers if the active layers are structured laterally for improved optical confinement. This is predicted by 3-d optical calculations; they show that lateral optical confinement is needed to counteract the anti-guiding features of IV-VIs due to their negative temperature dependence of the refractive index. An experimental proof is performed with PbSe quantum well based VECSEL grown on a Si-substrate by molecular beam epitaxy and emitting around 3.3 μm. With proper mesa-etching, the threshold intensity is about 8-times reduced.

  17. Modular PbSrS/PbS mid-infrared vertical external cavity surface emitting laser on Si

    Science.gov (United States)

    Khiar, A.; Rahim, M.; Fill, M.; Felder, F.; Zogg, H.; Cao, D.; Kobayashi, S.; Yokoyama, T.; Ishida, A.

    2011-07-01

    A mid-infrared vertical external cavity surface emitting laser (VECSEL) based on undoped PbS is described herein. A 200 nm-thick PbS active layer embedded between PbSrS cladding layers forms a double heterostructure. The layers are grown on a lattice and thermal expansion mismatched Si-substrate. The substrate is placed onto a flat bottom Bragg mirror again grown on a Si substrate, and the VECSEL is completed with a curved top mirror. Pumping is done optically with a 1.55 μm laser diode. This leads to an extremely simple modular fabrication process. Lasing wavelengths range from 3-3.8 μm at 100-260 K heat sink temperature. The lowest threshold power is ˜210 mWp and highest output power is ˜250 mWp. The influence of the different recombination mechanism as well as free carrier absorption on the threshold power is modeled.

  18. Lead-chalcogenide mid-infrared vertical external cavity surface emitting lasers with improved threshold: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Fill, Matthias [ETH Zurich, Laser Spectroscopy and Sensing Lab, 8093 Zurich (Switzerland); Phocone AG, 8005 Zurich (Switzerland); Debernardi, Pierluigi [IEIIT-CNR, Torino 10129 (Italy); Felder, Ferdinand [Phocone AG, 8005 Zurich (Switzerland); Zogg, Hans [ETH Zurich (Switzerland)

    2013-11-11

    Mid-infrared Vertical External Cavity Surface Emitting Lasers (VECSEL) based on narrow gap lead-chalcogenide (IV-VI) semiconductors exhibit strongly reduced threshold powers if the active layers are structured laterally for improved optical confinement. This is predicted by 3-d optical calculations; they show that lateral optical confinement is needed to counteract the anti-guiding features of IV-VIs due to their negative temperature dependence of the refractive index. An experimental proof is performed with PbSe quantum well based VECSEL grown on a Si-substrate by molecular beam epitaxy and emitting around 3.3 μm. With proper mesa-etching, the threshold intensity is about 8-times reduced.

  19. PbSe quantum well mid-infrared vertical external cavity surface emitting laser on Si-substrates

    Science.gov (United States)

    Fill, M.; Khiar, A.; Rahim, M.; Felder, F.; Zogg, H.

    2011-05-01

    Mid-infrared vertical external cavity surface emitting lasers based on PbSe/PbSrSe multi-quantum-well structures on Si-substrates are realized. A modular design allows growing the active region and the bottom Bragg mirror on two different Si-substrates, thus facilitating comparison between different structures. Lasing is observed from 3.3 to 5.1 μm wavelength and up to 52 °C heat sink temperature with 1.55 μm optical pumping. Simulations show that threshold powers are limited by Shockley-Read recombination with lifetimes as short as 0.1 ns. At higher temperatures, an additional threshold power increase occurs probably due to limited carrier diffusion length and carrier leakage, caused by an unfavorable band alignment.

  20. Coupled chaotic attractors and driving-induced bistability: A brief ...

    Indian Academy of Sciences (India)

    2015-02-04

    breaking interactions in a drive–response system with the driving-induced bistability. The basins of attraction on the initial conditions plane are observed for the driving-induced bistability. The basins are dependent on the interaction ...

  1. Passive cavity surface-emitting lasers: option of temperature-insensitive lasing wavelength for uncooled dense wavelength division multiplexing systems

    Science.gov (United States)

    Shchukin, V. A.; Ledentsov, N. N.; Slight, T.; Meredith, W.; Gordeev, N. Y.; Nadtochy, A. M.; Payusov, A. S.; Maximov, M. V.; Blokhin, S. A.; Blokhin, A. A.; Zadiranov, Yu. M.; Maleev, N. A.; Ustinov, V. M.; Choquette, K. D.

    2016-03-01

    A concept of passive cavity surface-emitting laser is proposed aimed to control the temperature shift of the lasing wavelength. The device contains an all-semiconductor bottom distributed Bragg reflector (DBR), in which the active medium is placed, a dielectric resonant cavity and a dielectric top DBR, wherein at least one of the dielectric materials has a negative temperature coefficient of the refractive index, dn/dT < 0. This is shown to be the case for commonly used dielectric systems SiO2/TiO2 and SiO2/Ta2O5. Two SiO2/TiO2 resonant structures having a cavity either of SiO2 or TiO2 were deposited on a substrate, their optical power reflectance spectra were measured at various temperatures, and refractive index temperature coefficients were extracted, dn/dT = 0.0021 K-1 for SiO2 and dn/dT = -0.0092 K-1 for TiO2. Using such dielectric materials allows designing passive cavity surface-emitting lasers having on purpose either positive, or zero, or negative temperature shift of the lasing wavelength dλ/dT. A design for temperature-insensitive lasing wavelength (dλ/dT = 0) is proposed. Employing devices with temperature-insensitive lasing wavelength in wavelength division multiplexing systems may allow significant reducing of the spectral separation between transmission channels and an increase in number of channels for a defined spectral interval enabling low cost energy efficient uncooled devices.

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

    Indian Academy of Sciences (India)

    there has been a considerable interest in bistable solitons in glass fibers (with non-Kerr properties), in connection with optical bistability and other possible applications leading to switching and logic-gate devices. In literature one distinguishes between two kinds of bistable solitons: one for which the nonlinear propagation ...

  3. Bistable dynamics of an insect–pathogen model

    Indian Academy of Sciences (India)

    Here, we were able to construct an insect–pathogen model which has bistable dynamics. This simple model may be helpful to identify the universal mechanisms which lead to bistability in a biological system. The control of bistable system is very difficult because the dynamics has sensitivity to initial conditions. Therefore, to ...

  4. Origin of bistability in the lac Operon.

    Science.gov (United States)

    Santillán, M; Mackey, M C; Zeron, E S

    2007-06-01

    Multistability is an emergent dynamic property that has been invoked to explain multiple coexisting biological states. In this work, we investigate the origin of bistability in the lac operon. To do this, we develop a mathematical model for the regulatory pathway in this system and compare the model predictions with other experimental results in which a nonmetabolizable inducer was employed. We investigate the effect of lactose metabolism using this model, and show that it greatly modifies the bistable region in the external lactose (Le) versus external glucose (Ge) parameter space. The model also predicts that lactose metabolism can cause bistability to disappear for very low Ge. We have also carried out stochastic numerical simulations of the model for several values of Ge and Le. Our results indicate that bistability can help guarantee that Escherichia coli consumes glucose and lactose in the most efficient possible way. Namely, the lac operon is induced only when there is almost no glucose in the growing medium, but if Le is high, the operon induction level increases abruptly when the levels of glucose in the environment decrease to very low values. We demonstrate that this behavior could not be obtained without bistability if the stability of the induced and uninduced states is to be preserved. Finally, we point out that the present methods and results may be useful to study the emergence of multistability in biological systems other than the lac operon.

  5. Hybrid optoelectronic device with multiple bistable outputs

    Science.gov (United States)

    Costazo-Caso, Pablo A.; Jin, Yiye; Gelh, Michael; Granieri, Sergio; Siahmakoun, Azad

    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.

  6. 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.

  7. 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....

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Coupled-wave analysis for photonic-crystal surface-emitting lasers on air holes with arbitrary sidewalls.

    Science.gov (United States)

    Peng, Chao; Liang, Yong; Sakai, Kyosuke; Iwahashi, Seita; Noda, Susumu

    2011-11-21

    The coupled-wave theory (CWT) is extended to a photonic crystal structure with arbitrary sidewalls, and a simple, fast, and effective model for the quantitatively analysis of the radiative characteristics of two-dimensional (2D) photonic-crystal surface-emitting lasers (PC-SELs) has been developed. For illustrating complicated coupling effects accurately, sufficient numbers of waves are included in the formulation, by considering their vertical field profiles. The radiation of band-edge modes is analyzed for two in-plane air-hole geometries, in the case of two types of sidewalls: i.e. "tapered case" and "tilted case." The results of CWT analysis agree well with the results of finite-difference time-domain (FDTD) numerical simulation. From the analytical solutions of the CWT, the symmetry properties of the band-edge modes are investigated. In-plane asymmetry of the air holes is crucial for achieving high output power because it causes partial constructive interference. Asymmetric air holes and tilted sidewalls help in inducing in-plane asymmetries. By breaking the symmetries with respect to the two orthogonal symmetric axes of the band-edge modes, the two factors can be tuned independently, so that the radiation power is enhanced while preserving the mode selectivity performance. Finally, top-down reactive ion etching (RIE) approach is suggested for the fabrication of such a structure. © 2011 Optical Society of America

  14. 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.

  15. 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)

  16. 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.

  17. Dimensionality reduction of bistable biological systems.

    Science.gov (United States)

    Zakharova, A; Nikoloski, Z; Koseska, A

    2013-03-01

    Time hierarchies, arising as a result of interactions between system's components, represent a ubiquitous property of dynamical biological systems. In addition, biological systems have been attributed switch-like properties modulating the response to various stimuli across different organisms and environmental conditions. Therefore, establishing the interplay between these features of system dynamics renders itself a challenging question of practical interest in biology. Existing methods are suitable for systems with one stable steady state employed as a well-defined reference. In such systems, the characterization of the time hierarchies has already been used for determining the components that contribute to the dynamics of biological systems. However, the application of these methods to bistable nonlinear systems is impeded due to their inherent dependence on the reference state, which in this case is no longer unique. Here, we extend the applicability of the reference-state analysis by proposing, analyzing, and applying a novel method, which allows investigation of the time hierarchies in systems exhibiting bistability. The proposed method is in turn used in identifying the components, other than reactions, which determine the systemic dynamical properties. We demonstrate that in biological systems of varying levels of complexity and spanning different biological levels, the method can be effectively employed for model simplification while ensuring preservation of qualitative dynamical properties (i.e., bistability). Finally, by establishing a connection between techniques from nonlinear dynamics and multivariate statistics, the proposed approach provides the basis for extending reference-based analysis to bistable systems.

  18. 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.

  19. 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.

  20. 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)

  1. Frequency selective bistable switching in metamaterial based photonic bandgap medium

    Science.gov (United States)

    Jose, Jolly

    2014-10-01

    We present frequency selective bistable response at the defect mode of the zero-nbar bandgap of a photonic bandgap (PBG) material made of negative and positive index media. The nonlinear (Kerr) layer acts as the defect layer in the periodic PBG material. Incorporating metamaterial based electromagnetically induced transparency (EIT) like resonance in the positive layer leads to unprecedented line narrowing of the defect mode which in turn facilitates narrow frequency selective bistable operation, wherein all the bistable characteristics can be effectively engineered. Thresholding the output intensity selects the narrow band of frequencies that exhibit bistability.

  2. Multiple-beam output of a surface-emitted terahertz-wave parametric oscillator by using a slab MgO:LiNbO₃ crystal.

    Science.gov (United States)

    Wang, Weitao; Zhang, Xingyu; Wang, Qingpu; Cong, Zhenhua; Chen, Xiaohan; Liu, Zhaojun; Qin, Zengguang; Li, Ping; Tang, Guanqi; Li, Ning; Wang, Cong; Li, Yongfu; Cheng, Wenyong

    2014-02-15

    A MgO:LiNbO₃ slab configuration for the surface-emitted terahertz-wave parametric oscillator (TPO) is presented. The pump and the oscillating Stokes beams were totally reflected at the slab surface and propagated zigzaggedly in the slab MgO:LiNbO₃ crystal. Up to five terahertz beams were emitted perpendicularly to the surface of the crystal. The total output energy of the five THz-wave beams was 3.56 times as large as that obtained from the conventional surface-emitted TPO at the same experimental conditions. The intensity distributions of the THz wave beams were measured, and they were unsymmetrical in the horizontal direction while symmetrical in the vertical direction.

  3. 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.

  4. High-beam-quality, efficient operation of passively Q-switched Yb:YAG/Cr:YAG laser pumped by photonic-crystal surface-emitting laser

    Science.gov (United States)

    Guo, Xiaoyang; Tokita, Shigeki; Fujioka, Kana; Nishida, Hiro; Hirose, Kazuyoshi; Sugiyama, Takahiro; Watanabe, Akiyoshi; Ishizaki, Kenji; Noda, Susumu; Miyanaga, Noriaki; Kawanaka, Junji

    2017-07-01

    A passively Q-switched Yb:YAG/Cr:YAG laser pumped by a photonic-crystal surface-emitting laser (PCSEL) was developed. Yb:YAG crystal was cryogenically cooled by liquid nitrogen at 77 K. Excellent Gaussian beam profile ( M 2 = 1.02) and high slope efficiency of 58% were demonstrated without using a coupling optics between a laser material and PCSEL.

  5. Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene

    Science.gov (United States)

    2015-07-16

    Vertical External Cavity Surface Emitting Lasers). 2)! Installation of a FTIR based temperature dependent reflectivity setup for characterizing VECSELs...and SESAMs (Semiconductor Saturable Absorber Mirrors). 3)! Demonstration of up to 6 Watts CW with InAs QD (Quantum Dot) VECSELs (1250 nm) and 15...AFRL and at other university collaborators such as the University of Arizona. 2.#Installation#of#a# FTIR #based#temperature#dependent#reflectivity

  6. 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.

  7. 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.

  8. 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.

  9. 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.

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

    Indian Academy of Sciences (India)

    Bistable soliton states and switching in doubly inhomogeneously doped fiber couplers. Ajit Kumar. Theoretical aspects of optical solitons Volume 57 Issue 5-6 November-December 2001 pp 969-979 ... Switching between the bistable soliton states in a doubly and inhomogeneously doped fiber system is studied numerically.

  11. 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.

  12. 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.

  13. 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

  14. Electrically Pumped Vertical-Cavity Amplifiers

    DEFF Research Database (Denmark)

    Greibe, Tine

    2007-01-01

    . Detailed descriptions of the structure designs, clean room processing procedures and characterisations of the designs are presented in this thesis. Furthermore, comprehensive simulations of carrier distributions in the quantum well sections and the gain saturation of the different designs are performed...... of one of our bottom-emitting designs are good. It has an optical output power that is promising for use in an external-cavity mode-locked laser. The growth of the structure however went wrong and the structure has no net gain, which spoiled our chances to investigate it further in an external cavity...

  15. 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

  16. 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

  17. Bistability in Coupled Oscillators Exhibiting Synchronized Dynamics

    Science.gov (United States)

    Olusola, O. I.; Vincent, U. E.; Njah, A. N.; Olowofela, J. A.

    2010-05-01

    We report some new results associated with the synchronization behavior of two coupled double-well Duffing oscillators (DDOs). Some sufficient algebraic criteria for global chaos synchronization of the drive and response DDOs via linear state error feedback control are obtained by means of Lyapunov stability theory. The synchronization is achieved through a bistable state in which a periodic attractor co-exists with a chaotic attractor. Using the linear perturbation analysis, the prevalence of attractors in parameter space and the associated bifurcations are examined. Subcritical and supercritical Hopf bifurcations and abundance of Arnold tongues — a signature of mode locking phenomenon are found.

  18. Bistability in mushroom-type metamaterials

    Science.gov (United States)

    Fernandes, David E.; Silveirinha, Mário G.

    2017-07-01

    Here, we study the electromagnetic response of asymmetric mushroom-type metamaterials loaded with nonlinear elements. It is shown that near a Fano resonance, these structures may have a strong tunable, bistable, and switchable response and enable giant nonlinear effects. By using an effective medium theory and full wave simulations, it is proven that the nonlinear elements may allow the reflection and transmission coefficients to follow hysteresis loops, and to switch the metamaterial between "go" and "no-go" states similar to an ideal electromagnetic switch.

  19. 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...

  20. Stability and morphing characteristics of bistable composite laminates

    Science.gov (United States)

    Tawfik, Samer A.

    The focus of the current research is to investigate the potential of using bistable unsymmetric cross-ply laminated composites as a means for achieving structures with morphed characteristics. To this end, an investigation of the design space for laminated composites exhibiting bistable behavior is undertaken and the key parameters controlling their behavior are identified. For this purpose a nonlinear Finite Element methodology using ABAQUS(TM) code is developed to predict both the cured shapes and the stability characteristics of unsymmetric cross-ply laminates. In addition, an experimental program is developed to validate the analytically predicted results through comparison with test data. A new method is proposed for attaching piezoelectric actuators to a bistable panel in order to preserve its favorable stability characteristics as well as optimizing the actuators performance. The developed nonlinear FE methodology is extended to predict the actuation requirements of bistable panels. Actuator requirements, predicted using the nonlinear FE analysis, are found to be in agreement with the test results. The current research also explores the potential for implementing bistable panels for Uninhabited Aerial Vehicle (UAV) wing configuration. To this end, a set of bistable panels is manufactured by combining symmetric and unsymmetric balanced and unbalanced stacking sequence and their stability characteristics are predicted. A preliminary analysis of the aerodynamic characteristics of the manufactured panels is carried out and the aerodynamic benefits of manufactured bistable panel are noted.

  1. Development of FPGA-Based Bistable Unit

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yoon Hee; Jeong, See Chae; Ha, Jae Hong [Korea Power Engineering Company, Daejeon (Korea, Republic of)

    2010-05-15

    It is well known that existing nuclear power plant (NPP) control systems contain many components which are becoming obsolete at an increasing rate. Various studies have been conducted to address control system hardware obsolescence. Obsolete analog and digital control systems in non-nuclear power plants are commonly replaced with modern digital control systems, programmable logic controllers (PLC) and distributed control systems (DCS). Field Programmable Gate Arrays (FPGAs) are highlighted as an alternative means for obsolete control systems. FPGAs are advanced digital integrated circuits (ICs) that contain configurable (programmable) blocks of logic along with configurable interconnects between these blocks. Designers can configure (program) such devices to perform a tremendous variety of tasks. FPGAs have been evolved from the technology of Programmable Logic Device (PLD). Nowadays they can contain millions of logic gates by nanotechnology and so be used to implement extremely large and complex functions that previously could be realized only using Application-Specific Integrated Circuits (ASICs). This paper is to present the development of a bistable unit which executes protection functions realized in FPGAs. Functional test is performed to verify its function. An Actel ProASIC3 FPGA platform is implemented as the bistable unit for Plant Protection System (PPS).

  2. 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.

  3. 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.

  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...

  5. On the Selection of Bistability in Genetic Regulatory Circuits

    Science.gov (United States)

    Ghim, Cheol-Min; Almaas, Eivind

    2008-03-01

    Bistability is a defining character of switching and memory devices. Many regulatory circuits observed in cellular reaction networks contain ``bistability motifs'' that endow a cell with efficient and reliable switching between different physiological modes of operation. One of the best characterized system, the lac operon in E. coli, has been shown to display a saddle-node bifurcation when induced by nonmetabolizable lactose analogue inducers, such as isopropylthio-β-D-galactoside (IPTG) and thio-methyl-galactoside (TMG). Motivated by the absence of bifurcation in the same system with its natural inducer, lactose, we studied the conditions for bistability and rationalized its fitness effects in the light of evolution. Stochastic simulations as well as mean-field approach confirm that history-dependent behavior as well as nongenetic inheritance, being realized by bistability motifs, may be beneficial in fluctuating environments.

  6. 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

  7. 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

  8. 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.

  9. Bistability, Epigenetics, and Bet-Hedging in Bacteria

    NARCIS (Netherlands)

    Veening, Jan-Willem; Smits, Wiep Klaas; Kuipers, Oscar P.

    2008-01-01

    Clonal populations of microbial cells often show a high degree of phenotypic variability under homogeneous conditions. Stochastic fluctuations in the cellular components that determine cellular states can cause two distinct subpopulations, a property called bistability Phenotypic heterogeneity can

  10. 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)

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Mid-infrared PbTe vertical external cavity surface emitting laser on Si-substrate with above 1 W output power

    Science.gov (United States)

    Rahim, M.; Fill, M.; Felder, F.; Chappuis, D.; Corda, M.; Zogg, H.

    2009-12-01

    Mid-infrared vertical external cavity surface emitting lasers (VECSELs) emitting above 1 W output power in pulsed mode and up to 17 mW in continuous mode at -172 °C were realized. Emission wavelength changes from 5 μm at -172 °C to 3.6 μm at 20 °C heat sink temperature. The active medium is a one wavelength thick PbTe layer grown by molecular beam epitaxy on a Si-substrate. It is followed by a 2.5 pair Pb1-yEuyTe/EuTe epitaxial Bragg mirror. The cavity is completed with an external curved Pb1-yEuyTe/BaF2 mirror. The VECSEL is optically pumped with 1.55 μm wavelength laser and In-soldered to Cu heat sink. No microstructural processing is needed.

  16. Flip-flop between soft-spring and hard-spring bistabilities in the ...

    Indian Academy of Sciences (India)

    freedom Toda oscillator that originally exhibits soft-spring bistability with counterclockwise hysteresis cycle. We observe that if the truncation is made third order, the harmonic bistability changes to hard-spring type with a clockwise hysteresis cycle.

  17. In Silico Evolved lac Operons Exhibit Bistability for Artificial Inducers, but Not for Lactose

    OpenAIRE

    van Hoek, M. J. A.; Hogeweg, P.

    2006-01-01

    Bistability in the lac operon of Escherichia coli has been widely studied, both experimentally and theoretically. Experimentally, bistability has been observed when E. coli is induced by an artificial, nonmetabolizable, inducer. However, if the lac operon is induced with lactose, the natural inducer, bistability has not been demonstrated. We derive an analytical expression that can predict the occurrence of bistability both for artificial inducers and lactose. We find very different condition...

  18. 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)

  19. 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)

  20. 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...

  1. 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)

  2. 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.

  3. 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)

  4. 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.

  5. 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)

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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).

  14. Optical bistability in nonlinear composites with coated ellipsoidal nanoparticles

    CERN Document Server

    Pinchuk, A

    2003-01-01

    Nonlinear composite structures show great promise for use in optical switching, signal processing, etc. We derive an effective nonlinear dielectric permittivity of composite structures where coated ellipsoidal nonlinear particles are imbedded in a linear host medium. The derived expression for the effective dielectric permittivity tensor follows the Clasius-Mossotti approximation. We observe conditions for the existence of the optical bistability effect in a coated ellipsoidal particle with a nonlinear core and a metallic shell. Our numerical results show stronger bistability effects in more dense suspensions of nonlinear heterogeneous ellipsoids.

  15. 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.

  16. 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

  17. 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.

  18. Bistable gradient networks. II. Storage capacity and behavior near saturation

    Science.gov (United States)

    McGraw, Patrick N.; Menzinger, Michael

    2003-01-01

    We examine numerically the storage capacity and the behavior near saturation of an attractor neural network consisting of bistable elements with an adjustable coupling strength, the bistable gradient network. For strong coupling, we find evidence of a first-order “memory blackout” phase transition, as in the Hopfield network. For weak coupling, on the other hand, there is no evidence of such a transition and memorized patterns can be stable even at high levels of loading. The enhanced storage capacity comes, however, at the cost of imperfect retrieval of the patterns from corrupted versions.

  19. In silico evolved lac operons exhibit bistability for artificial inducers, but not for lactose.

    Science.gov (United States)

    van Hoek, M J A; Hogeweg, P

    2006-10-15

    Bistability in the lac operon of Escherichia coli has been widely studied, both experimentally and theoretically. Experimentally, bistability has been observed when E. coli is induced by an artificial, nonmetabolizable, inducer. However, if the lac operon is induced with lactose, the natural inducer, bistability has not been demonstrated. We derive an analytical expression that can predict the occurrence of bistability both for artificial inducers and lactose. We find very different conditions for bistability in the two cases. Indeed, for artificial inducers bistability is predicted, but for lactose the condition for bistability is much more difficult to satisfy. Moreover, we demonstrate that in silico evolution of the lac operon generates an operon that avoids bistability with respect to lactose, but does exhibit bistability with respect to artificial inducers. The activity of this evolved operon strikingly resembles the experimentally observed activity of the operon. Thus our computational experiments suggest that the wild-type lac operon, which regulates lactose metabolism, is not a bistable switch. Nevertheless, for engineering purposes, this operon can be used as a bistable switch with artificial inducers.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. The geodynamo as a bistable oscillator

    Science.gov (United States)

    Hoyng, P.; Ossendrijver, M. A. J. H.; Schmitt, D.

    2001-07-01

    Our intent is to provide a simple and quantitative understanding of the variability of the axial dipole component of the geomagnetic field on both short and long time scales. To this end we study the statistical properties of a prototype nonlinear mean field model. An azimuthal average is employed, so that (1) we address only the axisymmetric component of the field, and (2) the dynamo parameters have a random component that fluctuates on the (fast) eddy turnover time scale. Numerical solutions with a rapidly fluctuating alpha reproduce several features of the geomagnetic field: (1) a variable, dominantly dipolar field with additional fine structure due to excited overtones, and sudden reversals during which the field becomes almost quadrupolar, (2) aborted reversals and excursions, (3) intervals between reversals having a Poisson distribution. These properties are robust, and appear regardless of the type of nonlinearity and the model parameters. A technique is presented for analysing the statistical properties of dynamo models of this type. The Fokker-Planck equation for the amplitude a of the fundamental dipole mode shows that a behaves as the position of a heavily damped particle in a bistable potential ~(1-a^2)^2, subject to random forcing. The dipole amplitude oscillates near the bottom of one well and makes occasional jumps to the other. These reversals are induced solely by the overtones. Theoretical expressions are derived for the statistical distribution of the dipole amplitude, the variance of the dipole amplitude between reversals, and the mean reversal rate. The model explains why the reversal rate increases with increasing secular variation, as observed. Moreover, the present reversal rate of the geodynamo, once per (2-3)x10^5years, is shown to imply a secular variation of the dipole moment of ~15% (about the current value). The theoretical dipole amplitude distribution agrees well with the Sint-800 data.

  5. Time-resolved spectral characterization of ring cavity surface emitting and ridge-type distributed feedback quantum cascade lasers by step-scan FT-IR spectroscopy.

    Science.gov (United States)

    Brandstetter, Markus; Genner, Andreas; Schwarzer, Clemens; Mujagic, Elvis; Strasser, Gottfried; Lendl, Bernhard

    2014-02-10

    We present the time-resolved comparison of pulsed 2nd order ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs) and pulsed 1st order ridge-type distributed feedback (DFB) QCLs using a step-scan Fourier transform infrared (FT-IR) spectrometer. Laser devices were part of QCL arrays and fabricated from the same laser material. Required grating periods were adjusted to account for the grating order. The step-scan technique provided a spectral resolution of 0.1 cm(-1) and a time resolution of 2 ns. As a result, it was possible to gain information about the tuning behavior and potential mode-hops of the investigated lasers. Different cavity-lengths were compared, including 0.9 mm and 3.2 mm long ridge-type and 0.97 mm (circumference) ring-type cavities. RCSE QCLs were found to have improved emission properties in terms of line-stability, tuning rate and maximum emission time compared to ridge-type lasers.

  6. 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

  7. Bistable dynamics of an insect–pathogen model

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 85; Issue 1. Bistable dynamics of an ... Here we consider density-dependent models of transmission because we characterize diseases that spread through environmental propagules or through random contact among individuals. We consider the case where the ...

  8. 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.

  9. 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…

  10. 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...

  11. 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

  12. 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)

  13. 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

  14. The Missing Luminous Blue Variables and the Bistability Jump

    NARCIS (Netherlands)

    Smith, N.; Vink, J.S.; de Koter, A.

    2004-01-01

    We discuss an interesting feature of the distribution of luminous blue variables (LBVs) on the H-R diagram, and we propose a connection with the bistability jump seen in the winds of early-type supergiants. There appears to be a deficiency of quiescent LBVs on the S Doradus instability strip at

  15. 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...

  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. 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

  18. Bistability of the naturally induced lactose utilization system of Escherichia coli

    Science.gov (United States)

    Stajic, Jelena; Wall, Michael

    2006-03-01

    In the absence of the preferred sugar glucose, lactose utilization machinery in the bacterium E. coli is activated. The genetic circuit responsible for this response, lac operon, has been observed to exhibit bistability when induced by an artificial inducer, TMG. Here we investigate conditions under which bistability might be observed in response to lactose. The aim of our study is to establish whether the natural system exhibits bistability, as is often assumed despite the lack of experimental support.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. Control of Bistability in a Delayed Duffing Oscillator

    Directory of Open Access Journals (Sweden)

    Mustapha Hamdi

    2012-01-01

    Full Text Available The effect of a high-frequency excitation on nontrivial solutions and bistability in a delayed Duffing oscillator with a delayed displacement feedback is investigated in this paper. We use the technique of direct partition of motion and the multiple scales method to obtain the slow dynamic of the system and its slow flow. The analysis of the slow flow provides approximations of the Hopf and secondary Hopf bifurcation curves. As a result, this study shows that increasing the delay gain, the system undergoes a secondary Hopf bifurcation. Further, it is indicated that as the frequency of the excitation is increased, the Hopf and secondary Hopf bifurcation curves overlap giving birth in the parameter space to small regions of bistability where a stable trivial steady state and a stable limit cycle coexist. Numerical simulations are carried out to validate the analytical finding.

  5. 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)

  6. 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.

  7. 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.

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

    Science.gov (United States)

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

    2014-09-01

    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.

  10. Interface dynamics and domain growth in thermally bistable fluids

    International Nuclear Information System (INIS)

    Shaviv, N.J.; Regev, O.

    1994-01-01

    Domain growth kinetics in a thermally bistable fluid with heat diffusion is studied. The time evolution of interfaces between the stable phases is calculated numerically in two dimensions and compared to some general results derived analytically. The qualitative behavior is found to be similar to the previously studied cases where fluid dynamics was neglected. There are, however, several important differences such as the value of the dynamical exponent, which determines the power law of the system's correlation length growth. The introduction of fluid motion into the model introduces additional properties, unfamiliar to previously studied systems, like the change of the pressure or the size of the system. This behavior is due to the advection of mass. The present model may have general relevance to any system modeled by a real Ginzburg-Landau-type equation coupled to fluid dynamical conservation equations. In particular, it is a step forward on the way to a faithful modeling of thermally bistable cloudy astrophysical media

  11. 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.

  12. 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.

  13. Bistability threshold inside hysteresis loop of nonlinear fiber Bragg gratings.

    Science.gov (United States)

    Yosia, Yosia; Ping, Shum; Chao, Lu

    2005-06-27

    We show the Cross Phase Modulation (XPM) effect between CW probe that operates in bistability region and strong Gaussian pump in a Fiber Bragg Grating (FBG) by Implicit 4th Order Runge-Kutta Method. The XPM effect results in three unique nonlinear switching behaviors of the probe transmission depending on the pump peak intensity and its Full Width Half Maximum (FWHM) value. From this observation, we offer the FBG three potential nonlinear switching applications in all-optical signal processing domain as: a step-up all-optical switching, an all-optical inverter, and an all-optical limiter. The bistability threshold that determines the nonlinear switching behaviors of probe transmission after Gaussian pump injection is defined numerically and shown to be equivalent to the unstable state inside hysteresis loop.

  14. Stochastic sensitivity of a bistable energy model for visual perception

    Science.gov (United States)

    Pisarchik, Alexander N.; Bashkirtseva, Irina; Ryashko, Lev

    2017-01-01

    Modern trends in physiology, psychology and cognitive neuroscience suggest that noise is an essential component of brain functionality and self-organization. With adequate noise the brain as a complex dynamical system can easily access different ordered states and improve signal detection for decision-making by preventing deadlocks. Using a stochastic sensitivity function approach, we analyze how sensitive equilibrium points are to Gaussian noise in a bistable energy model often used for qualitative description of visual perception. The probability distribution of noise-induced transitions between two coexisting percepts is calculated at different noise intensity and system stability. Stochastic squeezing of the hysteresis range and its transition from positive (bistable regime) to negative (intermittency regime) are demonstrated as the noise intensity increases. The hysteresis is more sensitive to noise in the system with higher stability.

  15. 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)

  16. Circular magnetic bistability in Co-rich amorphous microwires

    International Nuclear Information System (INIS)

    Chizhik, A; Gonzalez, J; Zhukov, A; Blanco, J M

    2003-01-01

    Circular magnetic bistability associated with a large Barkhausen jump between two states with opposite directions of circular magnetization have been observed by magneto-optical Kerr effect in nearly-zero magnetostrictive glass covered Co-rich amorphous microwire. The influence of external axial tensile stress on the circular switching field has been studied. Observed results have been related with a circular magneto-elastic anisotropy induced by a tensile stress in the outer transversally magnetized shell of the microwire

  17. 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.

  18. 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.

  19. Autocatalytic, bistable, oscillatory networks of biologically relevant organic reactions

    Science.gov (United States)

    Semenov, Sergey N.; Kraft, Lewis J.; Ainla, Alar; Zhao, Mengxia; Baghbanzadeh, Mostafa; Campbell, Victoria E.; Kang, Kyungtae; Fox, Jerome M.; Whitesides, George M.

    2016-09-01

    Networks of organic chemical reactions are important in life and probably played a central part in its origin. Network dynamics regulate cell division, circadian rhythms, nerve impulses and chemotaxis, and guide the development of organisms. Although out-of-equilibrium networks of chemical reactions have the potential to display emergent network dynamics such as spontaneous pattern formation, bistability and periodic oscillations, the principles that enable networks of organic reactions to develop complex behaviours are incompletely understood. Here we describe a network of biologically relevant organic reactions (amide formation, thiolate-thioester exchange, thiolate-disulfide interchange and conjugate addition) that displays bistability and oscillations in the concentrations of organic thiols and amides. Oscillations arise from the interaction between three subcomponents of the network: an autocatalytic cycle that generates thiols and amides from thioesters and dialkyl disulfides; a trigger that controls autocatalytic growth; and inhibitory processes that remove activating thiol species that are produced during the autocatalytic cycle. In contrast to previous studies that have demonstrated oscillations and bistability using highly evolved biomolecules (enzymes and DNA) or inorganic molecules of questionable biochemical relevance (for example, those used in Belousov-Zhabotinskii-type reactions), the organic molecules we use are relevant to metabolism and similar to those that might have existed on the early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable and oscillatory behaviour, we identify principles that explain the ways in which dynamic networks relevant to life could have developed. Modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks and of synthetic self-regulating and evolving

  20. 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

  1. 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.

  2. 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

  3. Optical Bistability For Optical Signal Processing And Computing

    Science.gov (United States)

    Peyghambarian, N.; Gibbs, H. M.

    1985-02-01

    In this paper we present the basic principles of optical bistability and summarize the current advances in semiconductor optical switching, with emphasis on recent results in GaAs, CuCI, InAs, InSb, CdS, ZnS, and ZnSe etalons. These devices have great potential for applications involving optical signal processing and computing. As an example, we discuss the use of arrays of bistable devices for parallel optical processing and for addressable spatial light modulators. The use of nonlinear etalons as optical gates is also illustrated. To date, GaAs devices have shown the most favorable characteristics for practical applications. They operate at room temperature with a few milliwatts of power using a laser diode as the only light source. Quasi-cw operation and optical fiber signal regeneration have also been demonstrated. A GaAs NOR gate operates in 1 ps with <3 pJ incident energy; this, of course, implies a 1 ps switch-on time for a bistable etalon.

  4. Bistability in spinal motoneurons in vivo: systematic variations in rhythmic firing patterns.

    Science.gov (United States)

    Lee, R H; Heckman, C J

    1998-08-01

    In the presence of the monoamines serotonin and norepinephrine, spinal motoneurons can exhibit bistable behavior, in which a brief period of excitatory input evokes prolonged self-sustained firing. A brief inhibitory input returns the cell to the quiescent state. To determine whether motoneurons differ in their capacity for bistable behavior, intracellular recordings were obtained in the decerebrate cat preparation. To enhance the likelihood of encountering bistable behavior, the noradrenergic alpha1 agonist methoxamine was applied to the ventral surface of the cord. The capacity of the cells to produce bistable behavior was assessed from the duration of self-sustained firing evoked by a brief (1.5 s) excitatory synaptic input from muscle spindle Ia afferents. About 35% (17 of 49) of the cells produced steady self-sustained firing for >3 s and were considered fully bistable. The other 32 cells ( approximately 65%) were partially bistable, with self-sustained firing lasting zero current, so that the ascending current threshold was positive while the descending current threshold was negative. This negative offset meant that fully bistable cells could exhibit tonic firing without depolarizing injected current. Partially bistable cells exhibited very different F-I characteristics. Firing rate acceleration was just as large as in fully bistable cells but did not occur until well above the current level needed to initiate rhythmic firing. F-I gain after acceleration was negative, there was little to no hysteresis between the ascending and descending firing thresholds, and both thresholds were above the zero current level. These properties of partially bistable cells suggest their functional role is in tasks requiring relatively brief, high forces. The low thresholds of fully bistable cells mean they will be readily recruited in low force tasks like posture, where their prolonged self-sustained firing would be advantageous.

  5. 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

  6. 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

  7. 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

  8. 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.

  9. Changes in the configuration of bistable centers in covalent semiconductors. Second-order phase transitions

    International Nuclear Information System (INIS)

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

    1989-01-01

    A new radiation defect with a bistable configuration was discovered in gallium arsenide. It differed from similar known defects by an inversion of states caused by variation of temperature. It is shown that configuration-bistable modifications of the structure can be regarded as second-order phase transitions

  10. 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

  11. Bistable traveling wave solutions in a competitive recursion system with Ricker nonlinearity

    Directory of Open Access Journals (Sweden)

    Shuxia Pan

    2014-03-01

    Full Text Available Using an abstract scheme of monotone semiflows, the existence of bistable traveling wave solutions of a competitive recursion system is established. From the viewpoint of population dynamics, the bistable traveling wave solutions describe the strong inter-specific actions between two competitive species.

  12. 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.

  13. 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.

  14. 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)

  15. Determinants of bistability in induction of the Escherichia coli lac operon.

    Science.gov (United States)

    Dreisigmeyer, D W; Stajic, J; Nemenman, I; Hlavacek, W S; Wall, M E

    2008-09-01

    The authors have developed a mathematical model of regulation of expression of the Escherichia coli lac operon, and have investigated bistability in its steady-state induction behaviour in the absence of external glucose. Numerical analysis of equations describing regulation by artificial inducers revealed two natural bistability parameters that can be used to control the range of inducer concentrations over which the model exhibits bistability. By tuning these bistability parameters, the authors found a family of biophysically reasonable systems that are consistent with an experimentally determined bistable region for induction by thio-methylgalactoside (TMG) (in Ozbudak et al. Nature, 2004, 427; p. 737). To model regulation by lactose, the authors developed similar equations in which allolactose, a metabolic intermediate in lactose metabolism and a natural inducer of lac, is the inducer. For biophysically reasonable parameter values, these equations yield no bistability in response to induction by lactose - only systems with an unphysically small permease-dependent export effect can exhibit small amounts of bistability for limited ranges of parameter values. These results cast doubt on the relevance of bistability in the lac operon within the natural context of E. coli, and help shed light on the controversy among existing theoretical studies that address this issue. The results also motivate a deeper experimental characterisation of permease-independent transport of lac inducers, and suggest an experimental approach to address the relevance of bistability in the lac operon within the natural context of E. coli. The sensitivity of lac bistability to the type of inducer emphasises the importance of metabolism in determining the functions of genetic regulatory networks.

  16. 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

  17. 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

  18. Spatial bistability generates hunchback expression sharpness in the Drosophila embryo.

    Directory of Open Access Journals (Sweden)

    Francisco J P Lopes

    2008-09-01

    Full Text Available During embryonic development, the positional information provided by concentration gradients of maternal factors directs pattern formation by providing spatially dependent cues for gene expression. In the fruit fly, Drosophila melanogaster, a classic example of this is the sharp on-off activation of the hunchback (hb gene at midembryo, in response to local concentrations of the smooth anterior-posterior Bicoid (Bcd gradient. The regulatory region for hb contains multiple binding sites for the Bcd protein as well as multiple binding sites for the Hb protein. Some previous studies have suggested that Bcd is sufficient for properly sharpened Hb expression, yet other evidence suggests a need for additional regulation. We experimentally quantified the dynamics of hb gene expression in flies that were wild-type, were mutant for hb self-regulation or Bcd binding, or contained an artificial promoter construct consisting of six Bcd and two Hb sites. In addition to these experiments, we developed a reaction-diffusion model of hb transcription, with Bcd cooperative binding and hb self-regulation, and used Zero Eigenvalue Analysis to look for multiple stationary states in the reaction network. Our model reproduces the hb developmental dynamics and correctly predicts the mutant patterns. Analysis of our model indicates that the Hb sharpness can be produced by spatial bistability, in which hb self-regulation produces two stable levels of expression. In the absence of self-regulation, the bistable behavior vanishes and Hb sharpness is disrupted. Bcd cooperative binding affects the position where bistability occurs but is not itself sufficient for a sharp Hb pattern. Our results show that the control of Hb sharpness and positioning, by hb self-regulation and Bcd cooperativity, respectively, are separate processes that can be altered independently. Our model, which matches the changes in Hb position and sharpness observed in different experiments, provides a

  19. 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....

  20. 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.

  1. 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

  2. Intercellular calcium waves in glial cells with bistable dynamics

    Science.gov (United States)

    Wei, Fang; Shuai, Jianwei

    2011-04-01

    A two-dimensional model is proposed for intercellular calcium (Ca2 +) waves with Ca2 +-induced IP3 regeneration and the diffusion of IP3 through gap junctions. Many experimental observations in glial cells, i.e. responding to local mechanical stimulation, glutamate application, mechanical stimulation followed by ACh application, and glutamate followed by mechanical stimulation, are reproduced and classified by the model. We show that a glial cell model with bistable dynamics, i.e. a Ca2 + oscillation state coexisting with a fixed point, can cause a prolonged plateau of Ca2 + signals in the cells nearby the stimulated cell when the cell network responds to the local mechanical stimulation.

  3. 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.

  4. Optical bistability of graphene in the terahertz range

    DEFF Research Database (Denmark)

    Peres, N. M. R.; Bludov, Yu V.; Santos, Jaime E.

    2014-01-01

    We use an exact solution of the relaxation-time Boltzmann equation in a uniform ac electric field to describe the nonlinear optical response of graphene in the terahertz (THz) range. The cases of monolayer, bilayer, and ABA-stacked trilayer graphene are considered, and the monolayer species...... is shown to be the most appropriate one to exploit the nonlinear free electron response. We find that a single layer of graphene shows optical bistability in the THz range, within the electromagnetic power range attainable in practice. The current associated with the third harmonic generation is also...

  5. Voltage-driven beam bistability in a reorientational uniaxial dielectric

    Directory of Open Access Journals (Sweden)

    Armando Piccardi

    2016-04-01

    Full Text Available We report on voltage controlled bistability of optical beams propagating in a nonlocal reorientational uniaxial dielectric, namely, nematic liquid crystals. In the nonlinear regime where spatial solitons can be generated, two stable states are accessible to a beam of given power in a finite interval of applied voltages, one state corresponding to linear diffraction and the other to self-confinement. We observe such a first-order transition and the associated hysteresis in a configuration when both the beam and the voltage reorientate the molecules beyond a threshold.

  6. A faster switching regime for zenithal bistable nematic displays

    International Nuclear Information System (INIS)

    Rudin, J.

    1997-01-01

    A simpler and faster switching regime for Zenithal Bistable Nematic displays is reported. A cell, based on homeotropic alignment of nematic liquid crystal over a continuous blazed monograting on one surface, can be switched using bipolar pulses an order of magnitude faster than monopolar pulses of the same voltage. We propose that this regime relies on simple dielectric coupling to drive the cell into a higher energy state with a long pulse time, and the relaxation into a lower energy state after the creation of surface defects from a shorter applied pulse. Although flexoelectric effects are observed, they do not form the basis of state selection as was proposed for the monopolar pulses

  7. Optical bistability in electrically coupled SOA-BJT devices

    Science.gov (United States)

    Costanzo-Caso, Pablo A.; Jin, Yiye; Gehl, Michael; Granieri, Sergio; Siahmakoun, Azad

    2010-06-01

    A novel optical bistable device based on an electrically coupled semiconductor optical amplifier (SOA) and a bipolar juncture transistor (BJT) is proposed and experimentally demonstrated. The measured switching time is about 0.9-1.0 us, mainly limited by the electrical capacitance of the SOA and the parasitic inductance of the electrical connections. However, the effects of parasitic components can be reduced employing current electronic-photonic integration circuits (EPIC). Numerical simulations confirm that for capacitance values in tens of femtofarads switching speed can reach tens of GHz.

  8. Bistability in a complementary metal oxide semiconductor inverter circuit.

    Science.gov (United States)

    Carroll, Thomas L

    2005-09-01

    Radiofrequency signals can disrupt the operation of low frequency circuits. A digital inverter circuit would seem to be immune to such disruption, because its output state usually jumps abruptly between 0 and 5 V. Nevertheless, when driven with a high frequency signal, the inverter can have two coexisting stable states (which are not at 0 and 5 V). Slow switching between these states (by changing the rf signal) will produce a low frequency signal. I demonstrate the bistability in a circuit experiment and in a simple model of the circuit.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Magnetic actuation and transition shapes of a bistable spherical cap

    Directory of Open Access Journals (Sweden)

    E.G. Loukaides

    2014-10-01

    Full Text Available Multistable shells have been proposed for a variety of applications; however, their actuation is almost exclusively addressed through embedded piezoelectric patches. Additional actuation techniques are needed for applications requiring high strains or where remote actuation is desirable. Part of the reason for the lack of research in this area is the absence of appropriate models describing the detailed deformation and energetics of such shells. This work presents a bistable spherical cap made of iron carbonyl-infused polydimethylsiloxane. The magnetizable structure can be actuated remotely through permanent magnets while the transition is recorded with a high-speed camera. Moreover, the experiment is reproduced in a finite element (FE dynamic model for comparison with the physical observations. High-speed footage of the physical cap inversion together with the FE modeling gives valuable insight on preferable intermediate geometries. Both methods return similar values for the magnetic field strength required for the snap-through. High-strain multistable spherical cap transformation is demonstrated, based on informed material selection. We discover that non-axisymmetric transition shapes are preferred in intermediate geometries by bistable spherical caps. We develop the methods for design and analysis of such actuators, including the feasibility of remote actuation methods for multistable shells.

  14. Boolean models can explain bistability in the lac operon.

    Science.gov (United States)

    Veliz-Cuba, Alan; Stigler, Brandilyn

    2011-06-01

    The lac operon in Escherichia coli has been studied extensively and is one of the earliest gene systems found to undergo both positive and negative control. The lac operon is known to exhibit bistability, in the sense that the operon is either induced or uninduced. Many dynamical models have been proposed to capture this phenomenon. While most are based on complex mathematical formulations, it has been suggested that for other gene systems network topology is sufficient to produce the desired dynamical behavior. We present a Boolean network as a discrete model for the lac operon. Our model includes the two main glucose control mechanisms of catabolite repression and inducer exclusion. We show that this Boolean model is capable of predicting the ON and OFF steady states and bistability. Further, we present a reduced model which shows that lac mRNA and lactose form the core of the lac operon, and that this reduced model exhibits the same dynamics. This work suggests that the key to model qualitative dynamics of gene systems is the topology of the network and Boolean models are well suited for this purpose.

  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. 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.

  17. Optical bi-stable shutter development/improvement

    Science.gov (United States)

    Lizon, J. L.; Haddad, N.; Castillo, R.

    2012-09-01

    Two of the VLT instruments (Giraffe and VIMOS) are using the large magnetic E/150 from Prontor (with an aperture diameter of 150 mm). As we were facing an unacceptable number of failures with this component some improvement plan was discussed already in 2004. The final decision for starting this program was conditioned by the decision from the constructor to stop the production. The opportunity was taken to improve the design building a fully bi-stable mechanism in order to reduce the thermal dissipation. The project was developed in collaboration between the two main ESO sites doing the best use of the manpower and of the technical capability available at the two centers. The project took advantage of the laser Mask Manufacturing Unit and the invar sheets used to prepare the VIMOS MOS mask to fabricate the shutter petals. Our paper describes the development including the intensive and long optimization period. To conclude this optimization we proceed with a long life test on two units. These units have demonstrate a very high level of reliability (up to 100 000 cycles without failure which can be estimated to an equivalent 6 years of operation of the instrument) A new bi-stable shutter driver and controller have also been developed. Some of the highlights of this unit are the fully configurable coil driving parameters, usage of braking strategy to dump mechanical vibration and reduce mechanical wearing, configurable usage of OPEN and CLOSE sensors, non volatile storage of parameters, user friendly front panel interface.

  18. 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)

  19. 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)

  20. 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)

  1. 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.

  2. 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

  3. 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)

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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

  9. 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

    , while light reflected from the other side has its polarization unchanged. Using the nonlinear transfer matrix calculations in the frequency domain, it is demonstrated that defect resonances in the nonlinear reflection spectra undergo bending, resulting in polarization bistability of reflected light....... This bistability is shown to result in abrupt switching between linear polarization of the output reflected light when the input intensity is varied. This switching is confirmed in finite-difference time-domain simulations, and its hysteresis character is established....

  10. 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

  11. Cramps: a sign of motoneurone 'bistability' in a human patient.

    Science.gov (United States)

    Baldissera, F; Cavallari, P; Dworzak, F

    1991-12-09

    In a patient suffering from severe long-lasting cramps, cramps were triggered in the triceps surae by volleys in homonymous Ia afferents (elicited by electrical stimulation or by tendon taps) and were interrupted by antidromic invasion and Renshaw inhibition of triceps surae motoneurones (evoked by a single maximal stimulation of motor axons). This result suggests that the mechanisms which generate the cramps are intrinsic to alpha-motoneurone somata. A similar on-off switching of a self-sustained motor discharge has been observed in the decerebrate cat and recognized to depend on 'bistability' of the motoneuronal membrane. We propose that the same mechanism may be at the origin of the cramp discharge.

  12. 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.

  13. 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.

  14. Bistability of flight states for heavy falling plates

    Science.gov (United States)

    Lau, Edwin; Huang, Wei-Xi

    2017-11-01

    Interactions of falling flat plates in two-dimensional flows is presented through direct numerical simulation and immersed boundary method. The transition from steady falling to tumbling flight for heavy plates is presented. At steep angles of release, the plates undergo a period of amplitude increasing fluttering motion before developing to tumble. For the same fluid-solid system of Reynolds number Re and moment of inertia I*, shallow angles of release develop to a state of steady falling after a period of diminishing fluttering amplitude. Simulations further construct a mapping of this bistable region. Relationships among Re, I*, and the critical angles of release separating the two flight states are also provided. The inclusion of this finding on the mapping of flight states suggests fluttering motion as a transitional state before the onset of tumble. National Natural Science Foundation of China or NSFC (Grant No. 11322221).

  15. 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.

  16. 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.

  17. 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)

  18. 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

  19. 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.

  20. 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.

  1. Melanopsin bistability: a fly's eye technology in the human retina.

    Directory of Open Access Journals (Sweden)

    Ludovic S Mure

    Full Text Available In addition to rods and cones, the human retina contains light-sensitive ganglion cells that express melanopsin, a photopigment with signal transduction mechanisms similar to that of invertebrate rhabdomeric photopigments (IRP. Like fly rhodopsins, melanopsin acts as a dual-state photosensitive flip-flop in which light drives both phototransduction responses and chromophore photoregeneration that bestows independence from the retinoid cycle required by rods and cones to regenerate photoresponsiveness following bleaching by light. To explore the hypothesis that melanopsin in humans expresses the properties of a bistable photopigment in vivo we used the pupillary light reflex (PLR as a tool but with methods designed to study invertebrate photoreceptors. We show that the pupil only attains a fully stabilized state of constriction after several minutes of light exposure, a feature that is consistent with typical IRP photoequilibrium spectra. We further demonstrate that previous exposure to long wavelength light increases, while short wavelength light decreases the amplitude of pupil constriction, a fundamental property of IRP difference spectra. Modelling these responses to invertebrate photopigment templates yields two putative spectra for the underlying R and M photopigment states with peaks at 481 nm and 587 nm respectively. Furthermore, this bistable mechanism may confer a novel form of "photic memory" since information of prior light conditions is retained and shapes subsequent responses to light. These results suggest that the human retina exploits fly-like photoreceptive mechanisms that are potentially important for the modulation of non-visual responses to light and highlights the ubiquitous nature of photoswitchable photosensors across living organisms.

  2. 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.

  3. 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

  4. 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)

  5. Low power consumption O-band VCSEL sources for upstream channels in PON systems

    DEFF Research Database (Denmark)

    Vegas Olmos, Juan José; Rodes Lopez, Roberto; Tafur Monroy, Idelfonso

    2012-01-01

    This paper presents an experimental validation of a low power optical network unit employing vertical-cavity surface-emitting lasers as upstream sources for passive optical networks with an increased power budget, enabling even larger splitting ratios....

  6. Atomic Interferometry, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Vertical cavity surface emitting lasers (VCSELs) is a new technology which can be used for developing high performance laser components for atom-based sensors...

  7. 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

  8. Determining the bistability parameter ranges of artificially induced lac operon using the root locus method.

    Science.gov (United States)

    Avcu, N; Alyürük, H; Demir, G K; Pekergin, F; Cavas, L; Güzeliş, C

    2015-06-01

    This paper employs the root locus method to conduct a detailed investigation of the parameter regions that ensure bistability in a well-studied gene regulatory network namely, lac operon of Escherichia coli (E. coli). In contrast to previous works, the parametric bistability conditions observed in this study constitute a complete set of necessary and sufficient conditions. These conditions were derived by applying the root locus method to the polynomial equilibrium equation of the lac operon model to determine the parameter values yielding the multiple real roots necessary for bistability. The lac operon model used was defined as an ordinary differential equation system in a state equation form with a rational right hand side, and it was compatible with the Hill and Michaelis-Menten approaches of enzyme kinetics used to describe biochemical reactions that govern lactose metabolism. The developed root locus method can be used to study the steady-state behavior of any type of convergent biological system model based on mass action kinetics. This method provides a solution to the problem of analyzing gene regulatory networks under parameter uncertainties because the root locus method considers the model parameters as variable, rather than fixed. The obtained bistability ranges for the lac operon model parameters have the potential to elucidate the appearance of bistability for E. coli cells in in vivo experiments, and they could also be used to design robust hysteretic switches in synthetic biology. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Morphing of Bistable Composite Laminates Using Distributed Piezoelectric Actuators

    Directory of Open Access Journals (Sweden)

    Marie-Laure Dano

    2012-01-01

    Full Text Available The use of bistable unsymmetric cross-ply laminates for morphing application has received growing attention in the last few years. So far, most studies use large rectangular piezoelectric Macro Fiber Composite (MFC patches bonded at the center of the laminate to induce snap-through. However, the use of large rectangular MFC patches bonded in the center of the laminates significantly influences the shape of the laminate by greatly reducing the curvature at the midsection of the laminate where the MFC patches are bonded. This paper presents a study where narrow cocured MFC strips distributed over the entire surface are used to induce snap-through of unsymmetric cross-ply laminates. This MFC configuration allows having a more uniform curvature in the laminate. Since the strips are bonded on both sides, reverse snap-through should be obtained. The study was both theoretical and experimental. A finite element nonlinear analysis was used to predict the two stable cylindrical configurations and the snap-through induced by MFC actuation. For the experimental study, a laminate-MFC structure was manufactured and tested. The shapes were measured using a 3D image correlation system as a function of applied voltage. Good correlations for the cylindrical shape and displacement field were observed.

  15. Piezoelectrically strained bistable laminates with macro fiber composites

    Science.gov (United States)

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

    2017-04-01

    The bistability and snap through capability of an unsymmetric laminate consisting of only Macro Fiber Composites (MFC) are investigated. The non-linear analysis predicts two cylindrically stable configurations when strain anisotropy is piezoelectrically induced within a [0MFC/90MFC]T laminate. This is achieved by bonding two MFCs in their actuated states and releasing the voltage post cure to create in-plane residual stresses. The minimization of total potential energy with the Rayleigh-Ritz method are used to analytically model the resulting laminate. A finite element analysis is conducted in MSC Nastran using the piezoelectric-thermal analogy approach to verify the analytical results. The effects of adhesive properties, bonding cure cycles, MFC layup, and its geometry on the curvatures, displacements, and bifurcation voltages are characterized. Finally, the snap through and reverse snap through capabilities with piezoelectric actuation are demonstrated. This adaptive laminate functions as both the actuator and the primary structure and allows large deformations under a non-continuous energy input. Its snap through capability allows full configuration control necessary in morphing applications.

  16. Ultralong relaxation times in bistable hybrid quantum systems.

    Science.gov (United States)

    Angerer, Andreas; Putz, Stefan; Krimer, Dmitry O; Astner, Thomas; Zens, Matthias; Glattauer, Ralph; Streltsov, Kirill; Munro, William J; Nemoto, Kae; Rotter, Stefan; Schmiedmayer, Jörg; Majer, Johannes

    2017-12-01

    Nonlinear systems, whose outputs are not directly proportional to their inputs, are well known to exhibit many interesting and important phenomena that have profoundly changed our technological landscape over the last 50 years. Recently, the ability to engineer quantum metamaterials through hybridization has allowed us to explore these nonlinear effects in systems with no natural analog. We investigate amplitude bistability, which is one of the most fundamental nonlinear phenomena, in a hybrid system composed of a superconducting resonator inductively coupled to an ensemble of nitrogen-vacancy centers. One of the exciting properties of this spin system is its long spin lifetime, which is many orders of magnitude longer than other relevant time scales of the hybrid system. This allows us to dynamically explore this nonlinear regime of cavity quantum electrodynamics and demonstrate a critical slowing down of the cavity population on the order of several tens of thousands of seconds-a time scale much longer than observed so far for this effect. Our results provide a foundation for future quantum technologies based on nonlinear phenomena.

  17. Fabrication Processes for Surface-Emitting via External 45-DEGREE Reflectors, High-Power via Arrayed Ridge - Single-Mode Phase-Locked Aluminum Gallium Arsenide/gallium Arsenide Semiconductor Laser Sources.

    Science.gov (United States)

    Porkolab, Gyorgy Arpad

    The fabrication of monolithically integrated configurations of semiconductor lasers incorporating multiple functions is still an open issue today in engineering. A useful set of functions to integrate are: surface-emitting, high -power, phase-locked, single-mode, and collimated laser beam output. In this work new materials and advanced fabrication processes are developed for integrating the first four of the five functions listed. The interest in semiconductor lasers is due to their greater than 90% internal quantum efficiency in converting current-flux to photon-flux, their small size and weight, and their wavelength range from 400 to 1,550 nm. Multitudes of applications are possible for semiconductor laser sources ranging from the low-volume market of satellite-based communications systems to the high-volume market of image display screens. Semimetallic amorphous carbon (SMAC) thin film is introduced as an etch mask for chemically assisted ion beam etching (CAIBE) resulting in smooth etched facets in AlGaAs/GaAs at normal- and 45-degrees- incidence angles. A self-aligned etch technique is introduced using 4 separate photoresist selector-masks on top of a fixed SMAC master -mask on top of the AlGaAs/GaAs substrate to perform 4 separate CAIBE etches at 3 different angles and to 3 different depths to create self-aligned 3-dimensional microstructures of 1.3-μm deep ridge waveguides (RWG), 6-μm deep laser facets, and 11- μm long back-to-back 45-degree reflectors arranged in 3 by 100 arrays. Trenches on topside and underside of laser facets are introduced to deflect current away from laser facets. Silicon-rich nitro-oxide thin film is introduced as triple-use encapsulation to provide chemical passivation of AlGaAs/GaAs, optical anti-reflection coating by being refractive-index matched to AlGaAs/GaAs, and electrical insulation. A pincer-action sample-holder for CAIBE is introduced allowing samples to heat up by ion beam heating. Various surface preparations

  18. 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.

  19. 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.

  20. 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.

  1. Optical bistability and four-wave mixing in a hybrid optomechanical system

    Science.gov (United States)

    Jiang, Lei; Yuan, Xiaorong; Cui, Yuanshun; Chen, Guibin; Zuo, Fen; Jiang, Cheng

    2017-10-01

    We explore theoretically the optical bistability and four-wave mixing (FWM) in a hybrid optomechanical system, where the mechanical resonator is simultaneously coupled to a cavity field and a two-level system (qubit). We can use a strong control field driving the cavity to control the bistable behavior of the steady-state photon number, phonon number, and the population inversion. The impact of qubit-resonator coupling strength on the bistable behavior is discussed. Furthermore, the two-level system can significantly modify the output fields of the cavity, leading to double optomechanically induced transparency (OMIT) and the enhancement of the FWM intensity. We find that the distance between the two peaks in the FWM spectrum can be controlled by the qubit-resonator coupling strength, and the peak value of the FWM intensity can be adjusted by the Rabi frequency of the control field.

  2. 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.

  3. 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.

  4. 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

  5. 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)

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Effect of second-order coupling on optical bistability in a hybrid optomechanical system

    Science.gov (United States)

    Asghari Nejad, Ali; Baghshahi, Hamid R.; Askari, Hassan R.

    2017-11-01

    We theoretically investigate an optomechanical system consisting of two coupled cavities, a bare optomechanical cavity and a traditional one. An optical parametric amplifier (OPA) is placed inside the traditional cavity. Optomechanical cavity has an oscillating mirror and a fixed one. In addition to the first order coupling between mechanical resonator of the system and the radiation pressure of optomechanical cavity, we consider a second order interaction between them. The evaluation of the system's behavior shows bistability in the mean photon number of optomechanical cavity. Our results show that, the second order coupling leads to degenerate solutions for the equation of mean photon number of optomechanical cavity. We see that the strength of SOC can change the domain of bistability region of optomechanical cavity. Also, properties of the field driving OPA have remarkable effects on the stability of optomechanical cavity. Moreover, we show that the domain of bistability region can be modified by changing of optical properties of the system.

  14. Optical bistability and optical response of an infrared quantum dot hybridized to VO2 nanoparticle

    Science.gov (United States)

    Zamani, Naser; Hatef, Ali; Nadgaran, Hamid; Keshavarz, Alireza

    2017-08-01

    In this work, we theoretically investigate optical bistability and optical response of a hybrid system consisting of semiconductor quantum dot (SQD) coupled with a vanadium dioxide nanoparticle (VO2NP) in the infrared (IR) regime. The VO2 material exists in semiconductor and metallic phases below and above the critical temperature, respectively where the particle optical properties dramatically change during this phase transition. In our calculations a filling fraction factor controls the VO2NP phase transition when the hybrid system interacts with a laser field. We demonstrate that the switch-up threshold for optical bistability is strongly controlled by filling fraction without changing the structure of the hybrid system. Also, it is shown that, the threshold of optical bistability increases when the VO2NP phases changes from semiconductor to metallic phase. The presented results have the potential to be applied in designing optical switching and optical storage.

  15. 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.

  16. Bias-dependent interface roughening and its effect on electric bistability of organic devices

    International Nuclear Information System (INIS)

    Zeng, Q.; Ye, F. F.; Li, W. B.; Chen, X. Q.; Yu, H. M.; Yang, X. J.; Hou, X. Y.; You, Y. T.

    2014-01-01

    Atomic force microscopy (AFM), field-emission scanning electron microscopy, and energy dispersive X-Ray spectroscopy are used to study morphological and compositional variations of metal-organic interfaces in organic bistable devices. The results show that bias voltage causes rougher interfaces with new protrusions, and the switching phenomena origins from the evolution of these protrusions under external electric field. In order to exclude other possible factors, three types of bistable devices are designed and examined. In addition, metal-coated AFM probes are utilized to simulate the switching process, which yields similar results and corroborates our conclusion

  17. Bias-dependent interface roughening and its effect on electric bistability of organic devices

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Q.; Ye, F. F.; Li, W. B.; Chen, X. Q.; Yu, H. M.; Yang, X. J.; Hou, X. Y., E-mail: xyhou@fudan.edu.cn [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education) and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433 (China); You, Y. T. [State Key Laboratory of ASIC and System, Department of Microelectronics, SIST, Fudan University, Shanghai 200433 (China)

    2014-01-06

    Atomic force microscopy (AFM), field-emission scanning electron microscopy, and energy dispersive X-Ray spectroscopy are used to study morphological and compositional variations of metal-organic interfaces in organic bistable devices. The results show that bias voltage causes rougher interfaces with new protrusions, and the switching phenomena origins from the evolution of these protrusions under external electric field. In order to exclude other possible factors, three types of bistable devices are designed and examined. In addition, metal-coated AFM probes are utilized to simulate the switching process, which yields similar results and corroborates our conclusion.

  18. 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

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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 a slider. The kinematic analysis of this new mechanism is studied, using nonlinear Elastica buckling beam theory, the PRBM of a large deflecting cantilever beam, the vector loop closure equations, and numerically solving nonlinear algebraic equations. A design method of the bistable mechanism...

  5. 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.

  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. 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.

  8. Random telegraphic voltage noise due to thermal bi-stability in a superconducting weak link

    Science.gov (United States)

    Biswas, Sourav; Kumar, Nikhil; Winkelmann, C. B.; Courtois, Herve; Gupta, Anjan K.

    2016-05-01

    We investigated the random telegraphic voltage noise signal in the hysteretic bi-stable state of a superconducting weak link device. Fluctuation induced random switching between zero voltage state and non-zero-voltage state gives rise to a random telegraphic voltage signal in time domain. This telegraphic noise is used to find the mean lifetime of each of the two states. The mean life time in the zero voltage state is found to decrease with increasing bias current while that of resistive state increases and thus the two cross at certain bias current. We qualitatively discuss this observed switching behavior as arising from the bi-stable nature.

  9. Thermodynamic limit of a nonequilibrium steady state: Maxwell-type construction for a bistable biochemical system.

    Science.gov (United States)

    Ge, Hao; Qian, Hong

    2009-10-02

    We show that the thermodynamic limit of a bistable phosphorylation-dephosphorylation cycle has a selection rule for the "more stable" macroscopic steady state. The analysis is akin to the Maxwell construction. Based on the chemical master equation approach, it is shown that, except at a critical point, bistability disappears in the stochastic model when fluctuation is sufficiently low but unneglectable. Onsager's Gaussian fluctuation theory applies to the unique macroscopic steady state. With an initial state in the basin of attraction of the "less stable" steady state, the deterministic dynamics obtained by the law of mass action is a metastable phenomenon. Stability and robustness in cell biology are emergent stochastic concepts.

  10. 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.

  11. Bistability in the chemical master equation for dual phosphorylation cycles

    Science.gov (United States)

    Bazzani, Armando; Castellani, Gastone C.; Giampieri, Enrico; Remondini, Daniel; Cooper, Leon N.

    2012-06-01

    Dual phospho/dephosphorylation cycles, as well as covalent enzymatic-catalyzed modifications of substrates are widely diffused within cellular systems and are crucial for the control of complex responses such as learning, memory, and cellular fate determination. Despite the large body of deterministic studies and the increasing work aimed at elucidating the effect of noise in such systems, some aspects remain unclear. Here we study the stationary distribution provided by the two-dimensional chemical master equation for a well-known model of a two step phospho/dephosphorylation cycle using the quasi-steady state approximation of enzymatic kinetics. Our aim is to analyze the role of fluctuations and the molecules distribution properties in the transition to a bistable regime. When detailed balance conditions are satisfied it is possible to compute equilibrium distributions in a closed and explicit form. When detailed balance is not satisfied, the stationary non-equilibrium state is strongly influenced by the chemical fluxes. In the last case, we show how the external field derived from the generation and recombination transition rates, can be decomposed by the Helmholtz theorem, into a conservative and a rotational (irreversible) part. Moreover, this decomposition allows to compute the stationary distribution via a perturbative approach. For a finite number of molecules there exists diffusion dynamics in a macroscopic region of the state space where a relevant transition rate between the two critical points is observed. Further, the stationary distribution function can be approximated by the solution of a Fokker-Planck equation. We illustrate the theoretical results using several numerical simulations.

  12. Perceptual memory drives learning of retinotopic biases for bistable stimuli.

    Directory of Open Access Journals (Sweden)

    Aidan Peter Murphy

    2014-02-01

    Full Text Available The visual system exploits past experience at multiple timescales to resolve perceptual ambiguity in the retinal image. For example, perception of a bistable stimulus can be biased towards one interpretation over another when preceded by a brief presentation of a disambiguated version of the stimulus (positive priming or through intermittent presentations of the ambiguous stimulus (stabilization. Similarly, prior presentations of unambiguous stimuli can be used to explicitly train a long-lasting association between a percept and a retinal location (perceptual association. These phenonema have typically been regarded as independent processes, with short-term biases attributed to perceptual memory and longer-term biases described as associative learning. Here we tested for interactions between these two forms of experience-dependent perceptual bias and demonstrate that short-term processes strongly influence long-term outcomes. We first demonstrate that the establishment of long-term perceptual contingencies does not require explicit training by unambiguous stimuli, but can arise spontaneously during the periodic presentation of brief, ambiguous stimuli. Using rotating Necker cube stimuli, we observed enduring, retinotopically specific perceptual biases that were expressed from the outset and remained stable for up to forty minutes, consistent with the known phenomenon of perceptual stabilization. Further, bias was undiminished after a break period of five minutes, but was readily reset by interposed periods of continuous, as opposed to periodic, ambiguous presentation. Taken together, the results demonstrate that perceptual biases can arise naturally and may principally reflect the brain’s tendency to favor recent perceptual interpretation at a given retinal location. Further, they suggest that an association between retinal location and perceptual state, rather than a physical stimulus, is sufficient to generate long-term biases in perceptual

  13. 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)

  14. 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.

  15. Intrinsic optical bistability of thin films of linear molecular aggregates : The two-exciton approximation

    NARCIS (Netherlands)

    Klugkist, Joost; Malyshev, Victor; Knoester, Jasper

    2008-01-01

    We generalize our recent work on the optical bistability of thin films of molecular aggregates [J. A. Klugkist et al., J. Chem. Phys. 127, 164705 (2007)] by accounting for the optical transitions from the one-exciton manifold to the two-exciton manifold as well as the exciton-exciton annihilation of

  16. 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.

  17. 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.

  18. Serotonin‐induced bistability of turtle motoneurones caused by a nifedipine‐sensitive calcium plateau potential

    DEFF Research Database (Denmark)

    Hounsgaard, J.; Kiehn, O.

    1989-01-01

    between two stable states by brief depolarizing and hyperpolarizing current pulses. As an expression of this bistable firing behaviour, the frequency‐current relation in response to a triangular current injection was counter‐clockwise in serotonin while clockwise in normal medium. 3. The delay to onset...

  19. Bistable switching in supercritical n+-n-n+GaAs transferred electron devices

    DEFF Research Database (Denmark)

    Jøndrup, Peter; Jeppesen, Palle; Jeppson, Bert

    1976-01-01

    Bistable switching in supercritically doped n+-n-n+GaAs transferred electron devices (TED's) is investigated experimentally and interpreted in computer simulations, for which details of the computer program are given. Three switching modes all leading to stable anode domains are discussed, namely...

  20. 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.

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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…

  9. 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....

  10. 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.

  11. 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...

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. A micromachined silicon valve driven by a miniature bi-stable electro-magnetic actuator

    NARCIS (Netherlands)

    Bohm, S.; Burger, G.J.; Burger, G.J.; Korthorst, M.T.; Roseboom, F.

    2000-01-01

    In this paper a novel combination of a micromachined silicon valve with low dead volume and a bi-stable electromagnetic actuator produced by conventional machining is presented. The silicon valve part, 7×7×1 mm3 in dimensions, is a sandwich construction of two KOH etched silicon wafers with a layer

  17. 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.

  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. Control of optical bistability and third-order nonlinearity via tunneling induced quantum interference in triangular quantum dot molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Si-Cong, E-mail: tiansicong@ciomp.ac.cn; Tong, Cun-Zhu, E-mail: tongcz@ciomp.ac.cn; Zhang, Jin-Long; Shan, Xiao-Nan; Fu, Xi-Hong; Zeng, Yu-Gang; Qin, Li; Ning, Yong-Qiang [State Key laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Wan, Ren-Gang [School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China)

    2015-06-15

    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.

  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. 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

  4. 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

  5. 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.

  6. 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.

  7. 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))

  8. Bistable Behavior of the Lac Operon in E. Coli When Induced with a Mixture of Lactose and TMG

    OpenAIRE

    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 concentrat...

  9. 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.

  10. Thermal bistability-based method for real-time optimization of ultralow-threshold whispering gallery mode microlasers.

    Science.gov (United States)

    Lin, Guoping; Candela, Y; Tillement, O; Cai, Zhiping; Lefèvre-Seguin, V; Hare, J

    2012-12-15

    A method based on thermal bistability for ultralow-threshold microlaser optimization is demonstrated. When sweeping the pump laser frequency across a pump resonance, the dynamic thermal bistability slows down the power variation. The resulting line shape modification enables a real-time monitoring of the laser characteristic. We demonstrate this method for a functionalized microsphere exhibiting a submicrowatt laser threshold. This approach is confirmed by comparing the results with a step-by-step recording in quasi-static thermal conditions.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  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. 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.

  5. 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.

  6. 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.

  7. Static alignment states in a bistable azimuthal nematic device with blazed grating sidewalls

    Energy Technology Data Exchange (ETDEWEB)

    Evans, C R; Brown, C V [School of Science and Technology, Nottingham Trent University, Erasmus Darwin Building, Clifton Lane, Clifton, Nottingham, NG11 8NS (United Kingdom); Davidson, A J; Mottram, N J, E-mail: carl.brown@ntu.ac.u [Department of Mathematics and Statistics, University of Strathclyde, Livingstone Tower, 26 Richmond Street, Glasgow G1 1XH (United Kingdom)

    2010-12-15

    Bistable azimuthal alignment has been produced in channels of homogeneous nematic liquid crystal with periodic grating sidewalls. The grating morphologies included a symmetric triangular profile (blaze/pitch (b/p) = 0), an asymmetric highly blazed sawtooth profile (b/p = 0.5) and profiles with different amounts of blaze asymmetry between these two extremes. The observed optical textures and the trend in the relative frequency of occurrence of the two stable states as a function of the asymmetry were in agreement with the predictions of n-director-based Frank-Oseen nematic continuum theory. A sidewall grating morphology with an intermediate degree of blaze asymmetry, b/p = 0.3, gave the highest optical contrast between the bistable states.

  8. 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

  9. Bistability and low-frequency fluctuations in semiconductor lasers with optical feedback: a theoretical analysis

    DEFF Research Database (Denmark)

    Mørk, Jesper; Tromborg, Bjarne; Christiansen, Peter Leth

    1988-01-01

    Near-threshold operation of a semiconductor laser exposed to moderate optical feedback may lead to low-frequency fluctuations. In the same region, a kink is observed in the light-current characteristic. Here it is demonstrated that these nonlinear phenomena are predicted by a noise driven multimode...... traveling-wave model. The dynamics of the low-frequency fluctuations are explained qualitatively in terms of bistability through an iterative description...

  10. Influence of catabolite repression and inducer exclusion on the bistable behavior of the lac operon.

    Science.gov (United States)

    Santillán, Moisés; Mackey, Michael C

    2004-03-01

    A mathematical model of the lac operon which includes all of the known regulatory mechanisms, including external-glucose-dependent catabolite repression and inducer exclusion, as well as the time delays inherent to transcription and translation, is presented. With this model we investigate the influence of external glucose, by means of catabolite repression and the regulation of lactose uptake, on the bistable behavior of this system.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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)

  1. 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.

  2. On square-wave-driven stochastic resonance for energy harvesting in a bistable system

    Directory of Open Access Journals (Sweden)

    Dongxu Su

    2014-11-01

    Full Text Available 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. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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).

  11. 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.

  12. 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.

  13. Signal denoising using stochastic resonance and bistable circuit for acoustic emission-based structural health monitoring

    Science.gov (United States)

    Kim, Jinki; Harne, Ryan L.; Wang, K. W.

    2017-04-01

    Noise is unavoidable and ever-present in measurements. As a result, signal denoising is a necessity for many scientific and engineering disciplines. In particular, structural health monitoring applications aim to detect often weak anomaly responses generated by incipient damage (such as acoustic emission signals) from background noise that contaminates the signals. Among various approaches, stochastic resonance has been widely studied and adopted for denoising and weak signal detection to enhance the reliability of structural heath monitoring. On the other hand, many of the advancements have been focused on detecting useful information from the frequency domain generally in a postprocessing environment, such as identifying damage-induced frequency changes that become more prominent by utilizing stochastic resonance in bistable systems, rather than recovering the original time domain responses. In this study, a new adaptive signal conditioning strategy is presented for on-line signal denoising and recovery, via utilizing the stochastic resonance in a bistable circuit sensor. The input amplitude to the bistable system is adaptively adjusted to favorably activate the stochastic resonance based on the noise level of the given signal, which is one of the few quantities that can be readily assessed from noise contaminated signals in practical situations. Numerical investigations conducted by employing a theoretical model of a double-well Duffing analog circuit demonstrate the operational principle and confirm the denoising performance of the new method. This study exemplifies the promising potential of implementing the new denoising strategy for enhancing on-line acoustic emission-based structural health monitoring.

  14. 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.

  15. Thermal Effect on Bistable Behaviour of T700/3234 Anti-symmetric Cylindrical Shells

    Directory of Open Access Journals (Sweden)

    ZHANG Zheng

    2016-10-01

    Full Text Available The temperature effects on the bi-stable characteristics of T700/3234 anti-symmetric carbon-fiber composite structure were studied. Three different layup specimens were prepared through composite molding process.The two points loading method was used in the experiment. The modified experimental testing machine (the experimental testing machine could be used to induce the bistable composite shell to snap between the two stable shapes, and continually capture the data in the experimental process. was related to tensile testing machine at present. The load-displacement curvatures under the temperature of 20℃,40℃,60℃ and 80℃ were given. The snap load was recorded and the photos were taken in the experimental process. After the experiment, the detailed data of curvature and twisting curvature were obtained by image processing technology. The variation law of the coiled-up radius, out-of-plane displacement, maximum snap-through and snap-back loads were analyzed. The effect on the composite structure was also discussed.The result shows that the thermal effect is vital to the bistable snaps process, and corresponding influence trends to the snap through and snap back process are given.

  16. Transcriptional Infidelity Promotes Heritable Phenotypic Change in a Bistable Gene Network

    Science.gov (United States)

    Gordon, Alasdair J. E; Halliday, Jennifer A; Blankschien, Matthew D; Burns, Philip A; Yatagai, Fumio; Herman, Christophe

    2009-01-01

    Bistable epigenetic switches are fundamental for cell fate determination in unicellular and multicellular organisms. Regulatory proteins associated with bistable switches are often present in low numbers and subject to molecular noise. It is becoming clear that noise in gene expression can influence cell fate. Although the origins and consequences of noise have been studied, the stochastic and transient nature of RNA errors during transcription has not been considered in the origin or modeling of noise nor has the capacity for such transient errors in information transfer to generate heritable phenotypic change been discussed. We used a classic bistable memory module to monitor and capture transient RNA errors: the lac operon of Escherichia coli comprises an autocatalytic positive feedback loop producing a heritable all-or-none epigenetic switch that is sensitive to molecular noise. Using single-cell analysis, we show that the frequency of epigenetic switching from one expression state to the other is increased when the fidelity of RNA transcription is decreased due to error-prone RNA polymerases or to the absence of auxiliary RNA fidelity factors GreA and GreB (functional analogues of eukaryotic TFIIS). Therefore, transcription infidelity contributes to molecular noise and can effect heritable phenotypic change in genetically identical cells in the same environment. Whereas DNA errors allow genetic space to be explored, RNA errors may allow epigenetic or expression space to be sampled. Thus, RNA infidelity should also be considered in the heritable origin of altered or aberrant cell behaviour. PMID:19243224

  17. Bistability in a hybrid optomechanical system: effect of a gain medium

    Science.gov (United States)

    Asghari Nejad, A.; Baghshahi, H. R.; Askari, H. R.

    2017-11-01

    In this paper, we investigate the optical bistability of a hybrid optomechanical system consisting of two coupled cavities: a bare optomechanical cavity (with an oscillating mirror at one end) and a traditional one. The traditional cavity is filled with an optical parametric amplifier (OPA), and an input pump laser is applied to it. The Hamiltonian of the system is written in a rotating frame. The dynamics of the system is driven by the quantum Langevin equations of motion. We demonstrate that the presence of an OPA can dramatically affect the type of stability of the optomechanical cavity. We show that it is possible to create a proper optical bistability for the optomechanical cavity by changing the gain coefficient of the OPA. Also, it is shown that changing the phase of the field driving the OPA has two different effects on the bistability region of the optomechanical cavity. Moreover, we show that by choosing a proper value for the detuning of the traditional cavity it is possible to observe a tristable behavior in the optomechanical cavity.

  18. 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.

  19. 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.

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

    Directory of Open Access Journals (Sweden)

    Gray D. Davidson

    2014-08-01

    Full Text Available 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 (~200ms 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 (~400ms, 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 RN component (aRN was evident at ~170ms post-stimulus over bilateral fronto-central scalp locations. An auditory LPC component (aLPC was evident at subsequent latencies (~350ms, 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 versus visual bistable perception.

  1. 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)

  2. 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.

  3. Bistability of the lac operon during growth of Escherichia coli on lactose and lactose+glucose.

    Science.gov (United States)

    Narang, Atul; Pilyugin, Sergei S

    2008-05-01

    The lac operon of Escherichia coli can exhibit bistability. Early studies showed that bistability occurs during growth on TMG/succinate and lactose+glucose, but not during growth on lactose. More recently, studies with lacGFP-transfected cells show bistability during growth on TMG/succinate, but not during growth on lactose and lactose+glucose. In the literature, these results are invariably attributed to variations in the destabilizing effect of the positive feedback generated by induction. Specifically, during growth on TMG/succinate, lac induction generates strong positive feedback because the permease stimulates the accumulation of intracellular TMG, which in turn, promotes the synthesis of even more permease. This positive feedback is attenuated during growth on lactose because hydrolysis of intracellular lactose by beta-galactosidase suppresses the stimulatory effect of the permease. It is attenuated even more during growth on lactose + glucose because glucose inhibits the uptake of lactose. But it is clear that the stabilizing effect of dilution also changes dramatically as a function of the medium composition. For instance, during growth on TMG/succinate, the dilution rate of lac permease is proportional to its activity, e, because the specific growth rate is independent of e (it is completely determined by the concentration of succinate). However, during growth on lactose, the dilution rate of the permease is proportional to e2 because the specific growth rate is proportional to the specific lactose uptake rate, which in turn, proportional to e. We show that: (a) This dependence on e2 creates such a strong stabilizing effect that bistability is virtually impossible during growth on lactose, even in the face of the intense positive feedback generated by induction. (b) This stabilizing effect is weakened during growth on lactose+glucose because the specific growth rate on glucose is independent of e, so that the dilution rate once again contains a term that

  4. Bi-stable wave propagation and early afterdepolarization-mediated cardiac arrhythmias.

    Science.gov (United States)

    Chang, Marvin G; Sato, Daisuke; de Lange, Enno; Lee, Jong-Hwan; Karagueuzian, Hrayr S; Garfinkel, Alan; Weiss, James N; Qu, Zhilin

    2012-01-01

    In normal atrial and ventricular tissue, the electrical wavefronts are mediated by the fast sodium current (I(Na)), whereas in sinoatrial and atrioventricular nodal tissue, conduction is mediated by the slow L-type calcium current (I(Ca,L)). However, it has not been shown whether the same tissue can exhibit both the I(Na)-mediated and the I(Ca,L)-mediated conduction. This study sought to test the hypothesis that bi-stable cardiac wave conduction, mediated by I(Na) and I(Ca,L), respectively, can occur in the same tissue under conditions promoting early afterdepolarizations (EADs), and to study how this novel wave dynamics is related to the mechanisms of EAD-mediated arrhythmias. Computer models of two-dimensional (2D) tissue with a physiologically detailed action potential model were used to study the bi-stable wave dynamics. Theoretical predictions were tested experimentally by optical mapping in neonatal rat ventricular myocyte monolayers. In the same 2D homogeneous tissue, we could induce spiral waves that are mediated by either I(Na) or I(Ca,L) under conditions in which the action potential model exhibited EADs. This bi-stable wave propagation behavior was similar to bi-stability shown in many other nonlinear systems. Because the bi-stable states are also excitable, we call this novel behavior bi-excitability. In a 2D heterogeneous tissue, the I(Ca,L)-mediated spiral wave meanders, giving rise to a twisting electrocardiographic QRS axis, resembling torsades de pointes, whereas the coexistence and interplay between the I(Na)-mediated wavefronts and I(Ca,L)-mediated wavefronts give rise to polymorphic ventricular tachycardia. We also present experimental evidence for bi-excitability under EAD-promoting conditions in neonatal rat ventricular myocyte monolayers exposed to BayK8644 and isoproterenol. Under EAD-prone conditions, both I(Na)-mediated conduction and I(Ca,L)-mediated conduction can occur in the same tissue. These novel wave dynamics may be responsible for

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Activation of Transducin by Bistable Pigment Parapinopsin in the Pineal Organ of Lower Vertebrates.

    Directory of Open Access Journals (Sweden)

    Emi Kawano-Yamashita

    Full Text Available 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

  14. Frustrated bistability as a means to engineer oscillations in biological systems.

    Science.gov (United States)

    Krishna, S; Semsey, S; Jensen, M H

    2009-05-21

    Oscillations play an important physiological role in a variety of biological systems. For example, respiration and carbohydrate synthesis are coupled to the circadian clock in cyanobacteria (Ishiura et al 1998 Science 281 1519) and ultradian oscillations with time periods of a few hours have been observed in immune response (NF-kappaB, Hoffmann et al 2002 Science 298 1241, Neson et al 2004 Science 306 704), apoptosis (p53, Lahav et al 2004 Nat. Genet. 36 53), development (Hes, Hirata et al 2002 Science 298 840) and growth hormone secretion (Plotsky and Vale 1985 Science 230 461, Zeitler et al 1991 Proc. Natl. Acad. Sci. USA 88 8920). Here we discuss how any bistable system can be 'frustrated' to produce oscillations of a desired nature--we use the term frustration, in analogy to frustrated spins in antiferromagnets, to refer to the addition of a negative feedback loop that destabilizes the bistable system. We show that the molecular implementation can use a wide variety of methods ranging from translation regulation, using small non-coding RNAs, to targeted protein modification to transcriptional regulation. We also introduce a simple graphical method for determining whether a particular implementation will produce oscillations. The shape of the resulting oscillations can be readily tuned to produce spiky and asymmetric oscillations--quite different from the shapes produced by synthetic oscillators (Elowitz and Leibler 2000 Nature 403 335, Fung et al 2005 Nature 435 118). The time period and amplitude can also be manipulated and these oscillators are easy to reset or switch on and off using a tunable external input. The mechanism of frustrated bistability could thus prove to be an easily implementable way to synthesize flexible, designable oscillators.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Competition of elasticity and flexoelectricity for bistable alignment of nematic liquid crystals on patterned substrates.

    Science.gov (United States)

    Atherton, T J; Adler, J H

    2012-10-01

    We show that patterned surfaces can promote bistable configurations of nematics for reasons other than the symmetry of the surface. Numerical and analytical calculations reveal that a nematic liquid crystal in contact with a striped surface is subject to the competing aligning influences of elastic anisotropy, differing energy cost of various types of deformation, and flexoelectricity, curvature-induced spontaneous polarization. These effects favor opposing ground states where the azimuthal alignment is, respectively, parallel or perpendicular to the stripes. Material parameters for which the effect might be observed lie within the range measured for bent-core nematogens.

  5. Competition of Elasticity and Flexoelectricity for bistable alignment of nematics on patterned substrates

    Science.gov (United States)

    Atherton, Timothy; Adler, James

    2013-03-01

    We show that patterned surfaces can promote bistable configurations of nematics for reasons other than the symmetry of the surface. Numerical and analytical calculations reveal that a nematic liquid crystal in contact with a striped surface is subject to the competing aligning influences of elastic anisotropy, differing energy cost of various types of deformation, and flexoelectricity, curvature-induced spontaneous polarization. These effects favor opposing ground states where the azimuthal alignment is, respectively, parallel or perpendicular to the stripes. Material parameters for which the effect might be observed lie within the range measured for bent-core nematogens.

  6. Competition of elasticity and flexoelectricity for bistable alignment of nematic liquid crystals on patterned substrates

    Science.gov (United States)

    Atherton, T. J.; Adler, J. H.

    2012-10-01

    We show that patterned surfaces can promote bistable configurations of nematics for reasons other than the symmetry of the surface. Numerical and analytical calculations reveal that a nematic liquid crystal in contact with a striped surface is subject to the competing aligning influences of elastic anisotropy, differing energy cost of various types of deformation, and flexoelectricity, curvature-induced spontaneous polarization. These effects favor opposing ground states where the azimuthal alignment is, respectively, parallel or perpendicular to the stripes. Material parameters for which the effect might be observed lie within the range measured for bent-core nematogens.

  7. 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)

  8. Soliton creation, propagation, and annihilation in aeromechanical arrays of one-way coupled bistable elements

    Science.gov (United States)

    Rosenberger, Tessa; Lindner, John F.

    We study the dynamics of mechanical arrays of bistable elements coupled one-way by wind. Unlike earlier hydromechanical unidirectional arrays, our aeromechanical one-way arrays are simpler, easier to study, and exhibit a broader range of phenomena. Soliton-like waves propagate in one direction at speeds proportional to wind speeds. Periodic boundaries enable solitons to annihilate in pairs in even arrays where adjacent elements are attracted to opposite stable states. Solitons propagate indefinitely in odd arrays where pairing is frustrated. Large noise spontaneously creates soliton- antisoliton pairs, as predicted by prior computer simulations. Soliton annihilation times increase quadratically with initial separations, as expected for random walk models of soliton collisions.

  9. Bistable flow occurrence in the 2D model of a steam turbine valve

    Science.gov (United States)

    Pavel, Procházka; Václav, Uruba

    2017-09-01

    The internal flow inside a steam turbine valve was investigated experimentally using PIV measurement. The valve model was proposed to be two-dimensional. The model was connected to the blow-down wind tunnel. The flow conditions were set by the different position of the valve plug. Several angles of the diffuser by diverse radii were investigated concerning flow separation and flow dynamics. It was found that the flow takes one of two possible bistable modes. The first regime is characterized by a massive flow separation just at the beginning of the diffuser section on the one side. The second regime is axisymmetric and the flow separation is not detected at all.

  10. 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.

  11. 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.

  12. Bistability and Asynchrony in a Boolean Model of the L-arabinose Operon in Escherichia coli.

    Science.gov (United States)

    Jenkins, Andy; Macauley, Matthew

    2017-08-01

    The lactose operon in Escherichia coli was the first known gene regulatory network, and it is frequently used as a prototype for new modeling paradigms. Historically, many of these modeling frameworks use differential equations. More recently, Stigler and Veliz-Cuba proposed a Boolean model that captures the bistability of the system and all of the biological steady states. In this paper, we model the well-known arabinose operon in E. coli with a Boolean network. This has several complex features not found in the lac operon, such as a protein that is both an activator and repressor, a DNA looping mechanism for gene repression, and the lack of inducer exclusion by glucose. For 11 out of 12 choices of initial conditions, we use computational algebra and Sage to verify that the state space contains a single fixed point that correctly matches the biology. The final initial condition, medium levels of arabinose and no glucose, successfully predicts the system's bistability. Finally, we compare the state space under synchronous and asynchronous update and see that the former has several artificial cycles that go away under a general asynchronous update.

  13. Bistable behavior in a model of the lac operon in Escherichia coli with variable growth rate.

    Science.gov (United States)

    Santillán, M

    2008-03-15

    This work is a continuation from another study previously published in this journal. Both the former and the present works are dedicated to investigating the bistable behavior of the lac operon in Escherichia coli from a mathematical modeling point of view. In the previous article, we developed a detailed mathematical model that accounts for all of the known regulatory mechanisms in this system, and studied the effect of inducing the operon with lactose instead of an artificial inducer. In this article, the model is improved to account, in a more detailed way, for the interaction of the repressor molecules with the three lac operators. A recently discovered cooperative interaction between the CAP molecule (an activator of the lactose operon) and Operator 3 (which influences DNA folding) is also included in this new version of the model. The growth rate dependence on the rate of energy entering the bacteria (in the form of transported glucose molecules and of metabolized lactose molecules) is also considered. A large number of numerical experiments is carried out with this improved model. The results are discussed in regard to the bistable behavior of the lactose operon. Special attention is paid to the effect that a variable growth rate has on the system dynamics.

  14. 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.

  15. 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.

  16. 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.

  17. 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)

  18. 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

  19. 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.

  20. 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.