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Osama R Bilal, André Foehr, Chiara Daraio
The realization of acoustic devices analogous to electronic systems, like diodes, transistors, and logic elements, suggests the potential use of elastic vibrations (i.e., phonons) in information processing, for example, in advanced computational systems, smart actuators, and programmable materials. Previous experimental realizations of acoustic diodes and mechanical switches have used nonlinearities to break transmission symmetry. However, existing solutions require operation at different frequencies or involve signal conversion in the electronic or optical domains...
April 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
Felix Tabbert, Christian Schelte, Mustapha Tlidi, Svetlana V Gurevich
We report on the dynamics of localized structures in an inhomogeneous Swift-Hohenberg model describing pattern formation in the transverse plane of an optical cavity. This real order parameter equation is valid close to the second-order critical point associated with bistability. The optical cavity is illuminated by an inhomogeneous spatial Gaussian pumping beam and subjected to time-delayed feedback. The Gaussian injection beam breaks the translational symmetry of the system by exerting an attracting force on the localized structure...
March 2017: Physical Review. E
C Nicolis, G Nicolis
The classical setting of stochastic resonance is extended to account for parameter variations leading to transitions between a unique stable state, bistability, and multistability regimes, across singularities of various kinds. Analytic expressions for the amplitude and the phase of the response in terms of key parameters are obtained. The conditions for optimal responses are derived in terms of the bifurcation parameter, the driving frequency, and the noise strength.
March 2017: Physical Review. E
Farshid Jafarpour, Tommaso Biancalani, Nigel Goldenfeld
The origin of homochirality, the observed single-handedness of biological amino acids and sugars, has long been attributed to autocatalysis, a frequently assumed precursor for early life self-replication. However, the stability of homochiral states in deterministic autocatalytic systems relies on cross-inhibition of the two chiral states, an unlikely scenario for early life self-replicators. Here we present a theory for a stochastic individual-level model of autocatalytic prebiotic self-replicators that are maintained out of thermal equilibrium...
March 2017: Physical Review. E
Gonzalo Hernandez-Hernandez, Jesse Myers, Enrique Alvarez-Lacalle, Yohannes Shiferaw
Signal transduction within biological cells is governed by networks of interacting proteins. Communication between these proteins is mediated by signaling molecules which bind to receptors and induce stochastic transitions between different conformational states. Signaling is typically a cooperative process which requires the occurrence of multiple binding events so that reaction rates have a nonlinear dependence on the amount of signaling molecule. It is this nonlinearity that endows biological signaling networks with robust switchlike properties which are critical to their biological function...
March 2017: Physical Review. E
Michael Turelli, Nicholas H Barton
A novel strategy for controlling the spread of arboviral diseases such as dengue, Zika and chikungunya is to transform mosquito populations with virus-suppressing Wolbachia. In general, Wolbachia transinfected into mosquitoes induce fitness costs through lower viability or fecundity. These maternally inherited bacteria also produce a frequency-dependent advantage for infected females by inducing cytoplasmic incompatibility (CI), which kills the embryos produced by uninfected females mated to infected males...
April 11, 2017: Theoretical Population Biology
Hoa Phan, Jeremy J Hrudka, Dilyara Igimbayeva, Latévi M Lawson Daku, Michael Shatruk
We propose a simple method for predicting the spin state of homoleptic complexes of the Fe(II) d6 ion with chelating diimine ligands. The approach is based on the analysis of a single metric parameter within a free (non-coordinated) ligand - the interatomic separation between the N-donor metal-binding sites. An extensive analysis of existing complexes allows the determination of critical N···N distances that dictate the regions of stability for the high-spin and low-spin complexes, as well as the intermediate range in which the magnetic bistability (spin crossover) can be observed...
April 12, 2017: Journal of the American Chemical Society
Jiong-Peng Zhao, Jian Xu, Song-De Han, Qing-Lun Wang, Xian-He Bu
Multiple switchable physical properties have been demonstrated in one single niccolite structural metal-organic framework, [(CH3 CH2 )2 NH2 ][Fe(III) Fe(II) (HCOO)6 ] (1), including (i) a reversible ferroelastic phase transition triggered by freezing the disordered (CH3 CH2 )2 NH2(+) cations, (ii) a thermally switchable dielectric constant transition accompanied by phase transition, and (iii) thermal and positive magnetic field driven magnetic poles reversal at low temperatures, attributed to different responses of the magnetization of Fe(II) and Fe(III) sublattices to external stimuli...
April 12, 2017: Advanced Materials
Daniel Navarro-Urrios, Néstor E Capuj, Martín F Colombano, P David García, Marianna Sledzinska, Francesc Alzina, Amadeu Griol, Alejandro Martínez, Clivia M Sotomayor-Torres
Optical nonlinearities, such as thermo-optic mechanisms and free-carrier dispersion, are often considered unwelcome effects in silicon-based resonators and, more specifically, optomechanical cavities, since they affect, for instance, the relative detuning between an optical resonance and the excitation laser. Here, we exploit these nonlinearities and their intercoupling with the mechanical degrees of freedom of a silicon optomechanical nanobeam to unveil a rich set of fundamentally different complex dynamics...
April 11, 2017: Nature Communications
Xiuli Cen, Zhilan Feng, Yiqiang Zheng, Yulin Zhao
Antibiotic-resistant bacteria have posed a grave threat to public health by causing a number of nosocomial infections in hospitals. Mathematical models have been used to study transmission dynamics of antibiotic-resistant bacteria within a hospital and the measures to control antibiotic resistance in nosocomial pathogens. Studies presented in Lipstich et al. (Proc Natl Acad Sci 97(4):1938-1943, 2000) and Lipstich and Bergstrom (Infection control in the ICU environment. Kluwer, Boston, 2002) have provided valuable insights in understanding the transmission of antibiotic-resistant bacteria in a hospital...
April 10, 2017: Journal of Mathematical Biology
Soroush Kamrava, Davood Mousanezhad, Hamid Ebrahimi, Ranajay Ghosh, Ashkan Vaziri
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...
April 7, 2017: Scientific Reports
Jun Guo, Leyong Jiang, Yue Jia, Xiaoyu Dai, Yuanjiang Xiang, Dianyuan Fan
Optical bistability of graphene surface plasmon is investigated numerically, using grating coupling method at normal light incidence. The linear surface plasmon resonance is strongly dependent on Femi-level of graphene, hence it can be tuned in a large wavelength range. Due to the field enhancement of graphene surface plasmon resonance and large third-order nonlinear response of graphene, a low-threshold optical hysteresis has been observed. The threshold value with 20MW/cm<sup>2</sup> and response time with 1...
March 20, 2017: Optics Express
Aparupa Kar, Nabamita Goswami, Ardhendu Saha
A proposal on optical bistability at ultralow switching threshold and lower Fermi-level of graphene around 2 THz is implemented analytically through the proposed long-range surface plasmon resonance configuration by employing local field enhancement effects owing to the excitation of a graphene symmetric mode within graphene sheets. Reported threshold intensity for the optical bistability to date is 1.6  kW/cm<sup>2</sup> within the terahertz region and 1.83  MW/cm<sup>2</sup> at near-IR range...
March 10, 2017: Applied Optics
A Asghari Nejad, H R Askari, H R Baghshahi
We theoretically investigate optical bistability for a hybrid optomechanical system, where two cavities (an optomechanical cavity and a traditional one) are coupled together. A Kerr medium is inserted in the optomechanical cavity and there is an ultra-cold atomic gas inside the other. Dynamics of the system is described by Heisenberg-Langevin equations of motion in the steady-state regime. Bistability is observed in intracavity intensity for the optomechanical cavity, and the response of this phenomenon to optical parameters of the system is investigated...
April 1, 2017: Applied Optics
Maria Fumanal, Juan Novoa, Jordi Ribas
One of the most remarkable bistable materials so far reported is made of π-dimers of a butyl-substituted spiro-biphenalenyl boron radical (butyl-SBP). The phase transition of this material, which is accompanied by changes in its optical, conductive and magnetic properties, occurs with a hysteretic loop 25-K wide and is centered at 335 K. Here, we present a computational study aimed at deciphering the origin of this hysteresis. We show that the phase transition of butyl-SBP consists of a spin transition of their constituent π-dimers coupled with an order-disorder transition involving the butyl chains linked to the N atoms of the superimposed phenalenyl rings of the π-dimer...
March 31, 2017: Chemistry: a European Journal
François Delavat, Ryo Miyazaki, Nicolas Carraro, Nicolas Pradervand, Jan Roelof van der Meer
Integrative and conjugative elements (ICEs) are widespread mobile DNA that transmit both vertically, in a host-integrated state, and horizontally, through excision and transfer to new recipients. Different families of ICEs have been discovered with more or less restricted host ranges, which operate by similar mechanisms but differ in regulatory networks, evolutionary origin and the types of variable genes they contribute to the host. Based on reviewing recent experimental data, we propose a general model of ICE life style that explains the transition between vertical and horizontal transmission as a result of a bistable decision in the ICE-host partnership...
March 25, 2017: FEMS Microbiology Reviews
Irene Otero-Muras, Pencho Yordanov, Joerg Stelling
Bistability has important implications in signaling pathways, since it indicates a potential cell decision between alternative outcomes. We present two approaches developed in the framework of the Chemical Reaction Network Theory for easy and efficient search of multiple steady state behavior in signaling networks (both with and without mass conservation), and apply them to search for sources of bistability at different levels of the interferon signaling pathway. Different type I interferon subtypes and/or doses are known to elicit differential bioactivities (ranging from antiviral, antiproliferative to immunomodulatory activities)...
April 2017: PLoS Computational Biology
Peter A White
It has been argued that there is a "subjective present" or "experienced moment" of about 3 seconds in duration, involving automatic binding of events into perceptual units on that time scale. Research on topics that have been taken as relevant to this proposal is reviewed. The topics include accuracy in reproduction of stimulus durations, synchronization of behavior with a regular beat, mental rhythmization of a regular beat, time units in behavior, segmentation of observed behavior into meaningful units, time scale of reversals of perception with bistable ambiguous figures, time scale of inhibition of return in visual search, and EEG responses to deviant stimuli in series of repeating stimuli...
April 3, 2017: Psychological Bulletin
Sudarshan A Shetty, Floor Hugenholtz, Leo Lahti, Hauke Smidt, Willem M de Vos
High individuality, large complexity and limited understanding of the mechanisms underlying human intestinal microbiome function remain the major challenges for designing beneficial modulation strategies. Exemplified by the analysis of intestinal bacteria in a thousand Western adults, we discuss key concepts of the human intestinal microbiome landscape, i.e. the compositional and functional 'core', the presence of community types and the existence of alternative stable states. Genomic investigation of core taxa revealed functional redundancy, which is expected to stabilize the ecosystem, as well as taxa with specialized functions that have the potential to shape the microbiome landscape...
March 1, 2017: FEMS Microbiology Reviews
Tian Chen, Jochen Mueller, Kristina Shea
Multi-material 3D printing has created new opportunities for fabricating deployable structures. We design reversible, deployable structures that are fabricated flat, have defined load bearing capacity, and multiple, predictable activated geometries. These structures are designed with a hierarchical framework where the proposed bistable actuator serves as the base building block. The actuator is designed to maximise its stroke length, with the expansion ratio approaching one when serially connected. The activation force of the actuator is parameterised through its joint material and joint length...
March 31, 2017: Scientific Reports
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