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Sample records for antihypertrophic molecular switch

  1. Molecular Rotors as Switches

    Directory of Open Access Journals (Sweden)

    Kang L. Wang

    2012-08-01

    Full Text Available The use of a functional molecular unit acting as a state variable provides an attractive alternative for the next generations of nanoscale electronics. It may help overcome the limits of conventional MOSFETd due to their potential scalability, low-cost, low variability, and highly integratable characteristics as well as the capability to exploit bottom-up self-assembly processes. This bottom-up construction and the operation of nanoscale machines/devices, in which the molecular motion can be controlled to perform functions, have been studied for their functionalities. Being triggered by external stimuli such as light, electricity or chemical reagents, these devices have shown various functions including those of diodes, rectifiers, memories, resonant tunnel junctions and single settable molecular switches that can be electronically configured for logic gates. Molecule-specific electronic switching has also been reported for several of these device structures, including nanopores containing oligo(phenylene ethynylene monolayers, and planar junctions incorporating rotaxane and catenane monolayers for the construction and operation of complex molecular machines. A specific electrically driven surface mounted molecular rotor is described in detail in this review. The rotor is comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly-doped P+ Si. This electrically driven sandwich-type monolayer molecular rotor device showed an on/off ratio of approximately 104, a read window of about 2.5 V, and a retention time of greater than 104 s. The rotation speed of this type of molecular rotor has been reported to be in the picosecond timescale, which provides a potential of high switching speed applications. Current-voltage spectroscopy (I-V revealed a temperature-dependent negative differential resistance (NDR associated with the device. The analysis of the device

  2. Molecular current switch

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Sworakowski, J.

    Brno : Faculty of Chemistry, Brno University of Technology, 2002 - (Schauer, F.), s. 89-96 ISBN 80-214-2265-3. [Seminar on Physics and Chemistry of Molecular Systems /7./. Brno (CZ), 13.12.2001] R&D Projects: GA AV ČR IAA1050901; GA ČR GA202/01/0518 Institutional research plan: CEZ:AV0Z4050913 Keywords : current switch * local states * dipolar species Subject RIV: BM - Solid Matter Physics ; Magnetism

  3. A Novel Molecular Switch

    OpenAIRE

    Daber, Robert; Lewis, Mitchell

    2009-01-01

    Transcriptional regulation is a fundamental process for regulating the flux of all metabolic pathways. For the last several decades, the lac operon has served as a valuable model for studying transcription. More recently, the switch that controls the operon has also been successfully adapted to function in mammalian cells. Here we describe how, using directed evolution, we have created a novel switch that recognizes an asymmetric operator sequence. The new switch has a repressor with altered ...

  4. The Smallest Molecular Switch

    OpenAIRE

    Emberly, Eldon G.; Kirczenow, George

    2003-01-01

    Ab-initio total energy calculations reveal benzene-dithiolate (BDT) molecules on a gold surface, contacted by a monoatomic gold STM tip to have two classes of low energy conformations with differing symmetries. Lateral motion of the tip or excitation of the molecule cause it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity these Au/BDT/Au nanowires are shown to be electrical...

  5. Switching in molecular systems

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Wang, Geng; Sworakowski, J.

    Lanškroun : IMAPS, Brno University of Technology, 2004 - (Šikula, J.), s. 215-220 ISBN 80-239-2835-X. [European Microelectronics and Packaging Symposium /3./. Prague (CZ), 16.06.2004-18.06.2004] R&D Projects: GA MŠk OC D14.30 Institutional research plan: CEZ:AV0Z4050913 Keywords : poly[3,4-(ethylenedioxy)thiophene] * electrical conductivity * charge carrier transport Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  6. Transcriptional regulation of cardiac genes balance pro- and anti-hypertrophic mechanisms in hypertrophic cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Nina Gennebäck

    2012-06-01

    Full Text Available Hypertrophic cardiomyopathy (HCM is characterized by unexplained left ventricular hypertrophy. HCM is often hereditary, but our knowledge of the mechanisms leading from mutation to phenotype is incomplete. The transcriptional expression patterns in the myocar - dium of HCM patients may contribute to understanding the mechanisms that drive and stabilize the hypertrophy. Cardiac myectomies/biopsies from 8 patients with hypertrophic obstructive cardiomyopathy (HOCM and 5 controls were studied with whole genome Illumina microarray gene expression (detecting 18 189 mRNA. When comparing HOCM myocardium to controls, there was significant transcriptional down-regulation of the MYH6, EGR1, APOB and FOS genes, and significant transcriptional up-regulation of the ACE2, JAK2, NPPA (ANP, APOA1 and HDAC5 genes. The transcriptional regulation revealed both pro- and anti-hypertrophic mechanisms. The pro-hypertrophic response was explained by the transcriptional down-regulation of MYH6, indicating that the switch to the fetal gene program is maintained, and the transcriptional up-regulation of JAK2 in the JAK-STAT pathway. The anti-hypertrophic response was seen as a transcriptional down-regulation of the immediate early genes (IEGs, FOS and EGR1, and a transcriptional up-regulation of ACE2 and HDAC5. This can be interpreted as a transcriptional endogenous protection system in the heart of the HOCM patients, neither growing nor suppressing the already hypertrophic myocardium.

  7. Remotely Controlled Isomer Selective Molecular Switching.

    Science.gov (United States)

    Schendel, Verena; Borca, Bogdana; Pentegov, Ivan; Michnowicz, Tomasz; Kraft, Ulrike; Klauk, Hagen; Wahl, Peter; Schlickum, Uta; Kern, Klaus

    2016-01-13

    Nonlocal addressing-the "remote control"-of molecular switches promises more efficient processing for information technology, where fast speed of switching is essential. The surface state of the (111) facets of noble metals, a confined two-dimensional electron gas, provides a medium that enables transport of signals over large distances and hence can be used to address an entire ensemble of molecules simultaneously with a single stimulus. In this study we employ this characteristic to trigger a conformational switch in anthradithiophene (ADT) molecules by injection of hot carriers from a scanning tunneling microscope (STM) tip into the surface state of Cu(111). The carriers propagate laterally and trigger the switch in molecules at distances as far as 100 nm from the tip location. The switching process is shown to be long-ranged, fully reversible, and isomer selective, discriminating between cis and trans diastereomers, enabling maximum control. PMID:26619213

  8. Self-consistent theory of molecular switching

    OpenAIRE

    Pistolesi, F; Blanter, Ya. M.; Martin, I.

    2008-01-01

    International audience We study the model of a molecular switch comprised of a molecule with a soft vibrational degree of freedom coupled to metallic leads. In the presence of strong electron-ion interaction, different charge states of the molecule correspond to substantially different ionic configurations, which can lead to very slow switching between energetically close configurations (Franck-Condon blockade). Application of transport voltage, however, can drive the molecule far out of t...

  9. Light-driven molecular current switch

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Toman, Petr; Sworakowski, J.; Lipinski, J.

    Seoul: Yonsei University, 2002, s. 279-291. ISBN 89-88706-43-9. [Multilateral Symposium between the Korean Academy of Science and Technology and the Foreign Academies. Seoul (KR), 08.05.2002-10.05.2002] R&D Projects: GA AV ČR IAA1050901 Institutional research plan: CEZ:AV0Z4050913 Keywords : molecular switch * molecular electronics * charge transport Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  10. A nanoplasmonic switch based on molecular machines

    KAUST Repository

    Zheng, Yue Bing

    2009-06-01

    We aim to develop a molecular-machine-driven nanoplasmonic switch for its use in future nanophotonic integrated circuits (ICs) that have applications in optical communication, information processing, biological and chemical sensing. Experimental data show that an Au nanodisk array, coated with rotaxane molecular machines, switches its localized surface plasmon resonances (LSPR) reversibly when it is exposed to chemical oxidants and reductants. Conversely, bare Au nanodisks and disks coated with mechanically inert control compounds, do not display the same switching behavior. Along with calculations based on time-dependent density functional theory (TDDFT), these observations suggest that the nanoscale movements within surface-bound "molecular machines" can be used as the active components in plasmonic devices. ©2009 IEEE.

  11. Light-driven molecular current switch

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Toman, Petr; Sworakowski, J.; Lipinski, J.

    2002-01-01

    Roč. 2, č. 4 (2002), s. 299-304. ISSN 1567-1739. [Multilateral Symposium between the Korean Academy of Science and Technology and the Foreign Academies. Seoul, 08.05.2002-10.05.2002] R&D Projects: GA AV ČR IAA1050901 Grant ostatní: GA-(PL) 4T09A 13222 Institutional research plan: CEZ:AV0Z4050913 Keywords : molecular switch * molecular electronics * charge transport Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.117, year: 2002

  12. Active Molecular Plasmonics: Controlling Plasmon Resonances with Molecular Switches

    KAUST Repository

    Zheng, Yue Bing

    2009-02-11

    A gold nanodisk array, coated with bistable, redox-controllable [2]rotaxane molecules, when exposed to chemical oxidants and reductants, undergoes switching of its plasmonic properties reversibly. By contrast, (i) bare gold nanodisks and (ii) disks coated with a redox-active, but mechanically inert, control compound do not display surface-plasmon-based switching. Along with calculations based on time-dependent density functional theory, these experimental observations suggest that the nanoscale movements within surface-bound “molecular machines” can be used as the active components in plasmonic devices.

  13. Molecular machines: stimulation of cation motion in molecular switches

    International Nuclear Information System (INIS)

    The theoretical aspects of the mechanism of the motion of cations and ligands in molecular machines referred to as redox switches are presented. The interrelated properties of cations - the energetic, electrochemical, spectral, and magnetic properties; their propensity to form either covalent or ionic bonds; and the relative softness and hardness of cations and ligands - stimulate molecular motion. These properties determine the thermal stability and stability to destruction caused by electrochemical processes and, eventually, the maximal number of transformation cycles. The maximal efficiency of redox switches is attained when the redox reaction involves a cation with a half-filled (d5, f7) or complete (d10, f14) electronic shell. The role of the Jahn-Teller effect is considered: it is responsible for geometry distortion, which stimulates cation motion. The properties of nd- and 4f-block cations are compared from the standpoint of their use for designing redox switches. In switches constructed on the basis of supramolecular compounds containing hard and soft moieties, softer cations (Fe2+, Co2+, Cu+, etc.) prefer to coordinate to soft ligands and harder cations (Fe3+, Co3+, Cu2+, etc.) prefer to coordinate to hard ligands. A cation moves due to the soft-hard change of its coordination sphere in the course of the redox reaction. Design of redox switches based on solid compounds with a cation in mixed oxidation state is shown to be promising. Cations can change their oxidation state with a change in temperature or pressure. The possibility of designing magnetic switches is considered

  14. Tunneling Nanoelectromechanical Switches Based on Compressible Molecular Thin Films.

    Science.gov (United States)

    Niroui, Farnaz; Wang, Annie I; Sletten, Ellen M; Song, Yi; Kong, Jing; Yablonovitch, Eli; Swager, Timothy M; Lang, Jeffrey H; Bulović, Vladimir

    2015-08-25

    Abrupt switching behavior and near-zero leakage current of nanoelectromechanical (NEM) switches are advantageous properties through which NEMs can outperform conventional semiconductor electrical switches. To date, however, typical NEMs structures require high actuation voltages and can prematurely fail through permanent adhesion (defined as stiction) of device components. To overcome these challenges, in the present work we propose a NEM switch, termed a "squitch," which is designed to electromechanically modulate the tunneling current through a nanometer-scale gap defined by an organic molecular film sandwiched between two electrodes. When voltage is applied across the electrodes, the generated electrostatic force compresses the sandwiched molecular layer, thereby reducing the tunneling gap and causing an exponential increase in the current through the device. The presence of the molecular layer avoids direct contact of the electrodes during the switching process. Furthermore, as the layer is compressed, the increasing surface adhesion forces are balanced by the elastic restoring force of the deformed molecules which can promote zero net stiction and recoverable switching. Through numerical analysis, we demonstrate the potential of optimizing squitch design to enable large on-off ratios beyond 6 orders of magnitude with operation in the sub-1 V regime and with nanoseconds switching times. Our preliminary experimental results based on metal-molecule-graphene devices suggest the feasibility of the proposed tunneling switching mechanism. With optimization of device design and material engineering, squitches can give rise to a broad range of low-power electronic applications. PMID:26244821

  15. Switching Molecular Orientation of Individual Fullerene at Room Temperature

    OpenAIRE

    Liu, Lacheng; Liu, Shuyi; Chen, Xiu; Li, Chao; Ling, Jie; Liu, Xiaoqing; Cai, Yingxiang; Wang, Li

    2013-01-01

    Reversible molecular switches with molecular orientation as the information carrier have been achieved on individual fullerene molecules adsorbed on Si (111) surface at room temperature. Scanning tunneling microscopy imaging directly demonstrates that the orientation of individual fullerene with an adsorption geometry of 5-6 bond is rotated by integral times as 30 degree after a pulse bias is applied between the STM tip and the molecule. Dependences of the molecular rotation probability on th...

  16. Monitoring Gene Expression In Vivo with Nucleic Acid Molecular Switches

    Energy Technology Data Exchange (ETDEWEB)

    David C. Ward; Patricia Bray-Ward

    2005-01-26

    The overall objectives of this project were (1) to develop allosteric ribozymes capable of acting as molecular switches for monitoring the levels of both wild-type and mutant mRNA species in living cells and whole animals and (2) to develop highly efficient reagents to deliver nucleic acid molecular switches into living cells, tissues and animals with the ultimate goal of expression profiling specific mRNAs of diagnostic or prognostic value within tumors in animals. During the past year, we have moved our laboratory to Nevada and in the moving process we have lost electronic and paper copies of prior progress reports concerning the construction and biological properties of the molecular switches. Since there was minimal progress during the last year on molecular switches, we are relying on past project reports to provide a summary of our data on this facet of the grant. Here we are summarizing the work done on the delivery reagents and their application to inducing mutations in living cells, which will include work done during the no cost extension.

  17. Single-walled carbon nanotube based molecular switch tunnel junctions.

    Science.gov (United States)

    Diehl, Michael R; Steuerman, David W; Tseng, Hsian-Rong; Vignon, Scott A; Star, Alexander; Celestre, Paul C; Stoddart, J Fraser; Heath, James R

    2003-12-15

    This article describes two-terminal molecular switch tunnel junctions (MSTJs) which incorporate a semiconducting, single-walled carbon nanotube (SWNT) as the bottom electrode. The nanotube interacts noncovalently with a monolayer of bistable, nondegenerate [2]catenane tetracations, self-organized by their supporting amphiphilic dimyristoylphosphatidyl anions which shield the mechanically switchable tetracations from a two-micrometer wide metallic top electrode. The resulting 0.002 micron 2 area tunnel junction addresses a nanometer wide row of approximately 2000 molecules. Active and remnant current-voltage measurements demonstrated that these devices can be reconfigurably switched and repeatedly cycled between high and low current states under ambient conditions. Control compounds, including a degenerate [2]catenane, were explored in support of the mechanical origin of the switching signature. These SWNT-based MSTJs operate like previously reported silicon-based MSTJs, but differently from similar devices incorporating bottom metal electrodes. The relevance of these results with respect to the choice of electrode materials for molecular electronics devices is discussed. PMID:14714382

  18. Simple technique for sequential Q-switching of molecular lasers.

    Science.gov (United States)

    Lucht, R. A.; Allario, F.; Jarrett, O., Jr.

    1972-01-01

    A simple technique for sequentially Q-switching molecular lasers is discussed in which an optical scanner is used as an optical folding element in a laser cavity consisting of a stationary diffraction grating and partially reflecting mirror. Sequential Q-switching of a conventional CO2 laser is demonstrated in which over sixty-two transitions between 9.2 and 10.8 microns are observed. Rapid repetition rates (200 Hz) and narrow laser pulses (less than 5 microsec) allow conventional signal processing techniques to be used with this multiwavelength laser source which is a versatile tool for laser propagation studies, absorption spectroscopy, and gain measurements. Results of a preliminary experiment demonstrating the utility of measuring selective absorption of CO2 laser wavelengths by C2H4 are shown.

  19. Light-Triggered Control of Plasmonic Refraction and Group Delay by Photochromic Molecular Switches

    DEFF Research Database (Denmark)

    Großmann, Malte; Klick, Alwin; Lemke, Christoph; Falke, Julian; Black, Maximilian; Fiutowski, Jacek; Goszczak, Arkadiusz Jaroslaw; Sobolewska, Elzbieta; Zillohu, Ahnaf Usman; Hedayati, Mehdi Keshavarz; Rubahn, Horst-Günter; Faupel, Franz; Elbahri, Mady; Bauer, Michael

    2015-01-01

    An interface supporting plasmonic switching is prepared from a gold substrate coated with a polymerfilm doped with photochromic molecular switches. A reversible light-induced change in the surface plasmon polariton dispersion curve of the interface is experimentally demonstrated, evidencing...

  20. Charge mobilities in molecular materials reversibly modified by light: towards a molecular switch

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Sworakowski, J.; Wang, Geng; Toman, Petr; Bartkowiak, W.; Combellas, C.

    Arcachon : University of Bordeaux, 2004. s. P111. [International Symposium on Photochromism /4./. 12.09.2004-15.09.2004, Arcachon] R&D Projects: GA MŠk OC D14.30 Keywords : molecular switch * charge mobility * photochromism Subject RIV: BM - Solid Matter Physics ; Magnetism

  1. Nonmechanical Conductance Switching in a Molecular Tunnel Junction.

    Science.gov (United States)

    Baratz, Adva; Baer, Roi

    2012-02-16

    We present a molecular junction composed of a donor (polyacetylene strands) and an acceptor (malononitrile) connected together via a benzene ring and coupled weakly to source and drain electrodes on each side, for which a gate electrode induces intramolecular charge transfer, switching reversibly the character of conductance. Using a new brand of density functional theory, for which orbital energies are similar to the quasiparticle energies, we show that the junction displays a single, gate-tunable differential conductance channel in a wide energy range. The gate field must align parallel to the displacement vector between donors and acceptor to affect their potential difference; for strong enough fields, spontaneous intramolecular electron transfer occurs. This event radically affects conductance, reversing the charge of carriers, enabling a spin-polarized current channel. We discuss the physical principles controlling the operation of the junction and find interplay of quantum interference, charging, Coulomb blockade, and electron-hole binding energy effects. We expect that this switching behavior is a generic property for similar donor-acceptor systems of sufficient stability. PMID:26286054

  2. Symmetry as a new element to control molecular switches.

    Science.gov (United States)

    Schweighauser, Luca; Häussinger, Daniel; Neuburger, Markus; Wegner, Hermann A

    2014-06-01

    The isomerization properties of an azocarbazole macrocycle in solution were investigated utilizing NMR spectroscopy with in situ irradiation in combination with DFT calculations. It was demonstrated that the position of azo units in a rigid macrocyclic system influences the photoisomerization pathway even if the initial all-E isomer is highly symmetric. Furthermore, the effect of ring strain on lowering the rates of thermal isomerization was demonstrated and a mechanism via an inversion-rotation proposed. The herein presented results and methods give new insights into the general nature of the azobenzene unit. In particular we illustrate the effect of symmetry changes due to macrocyclic arrangement on the photochemical and thermal isomerization properties, which will stimulate future development towards multinary molecular switches. PMID:24691779

  3. Electronic Transport Properties of a Naphthopyran-Based Optical Molecular Switch:an ab initio Study

    Institute of Scientific and Technical Information of China (English)

    XIA Cai-Juan; LIU De-Sheng; ZHANG Ying-Tang

    2011-01-01

    The electronic transport properties of a. Naphthopyran-based molecular optical switch are investigated by using the nonequilibrium Green's Function formalism combined with first-principles density functional theory. The molecule that comprises the switch can convert between its open and closed forms upon photoexcitation. Theoretical results show that the current through the open form is significantly larger than that through the closed form, which is different from other optical switches based on ring-opening reactions of the molecular bridge. The maximum on-off ratio (about 90) can be obtained at 1.4 V. The physical origin of the switching behavior is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap. Our result shows that the naphthopyran-based molecule is a good candidate for optical molecular switches and will be useful in the near future.%@@ ronic transport properties of a naphthopyran-based molecular optical switch are investigated by using the nonequilibrium Green's function formalism combined with first-principles density functional theory.The molecule that comprises the switch can convert between its open and closed forms upon photoexcitation.Theoretical results show that the current through the open form is significantly larger than that through the closed form,which is different from other optical switches based on ring-opening reactions of the molecular bridge.The maximum on-off ratio(about 90)can be obtained at 1.4 V.The physical origin of the switching behavior is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap.Our result shows that the naphthopyran-based molecule is a good candidate for optical molecular switches and will be useful in the near future.

  4. Switching dynamics in reaction networks induced by molecular discreteness

    International Nuclear Information System (INIS)

    To study the fluctuations and dynamics in chemical reaction processes, stochastic differential equations based on the rate equation involving chemical concentrations are often adopted. When the number of molecules is very small, however, the discreteness in the number of molecules cannot be neglected since the number of molecules must be an integer. This discreteness can be important in biochemical reactions, where the total number of molecules is not significantly larger than the number of chemical species. To elucidate the effects of such discreteness, we study autocatalytic reaction systems comprising several chemical species through stochastic particle simulations. The generation of novel states is observed; it is caused by the extinction of some molecular species due to the discreteness in their number. We demonstrate that the reaction dynamics are switched by a single molecule, which leads to the reconstruction of the acting network structure. We also show the strong dependence of the chemical concentrations on the system size, which is caused by transitions to discreteness-induced novel states

  5. A biomimetic molecular switch at work: coupling photoisomerization dynamics to peptide structural rearrangement.

    Science.gov (United States)

    García-Iriepa, Cristina; Gueye, Moussa; Léonard, Jérémie; Martínez-López, David; Campos, Pedro J; Frutos, Luis Manuel; Sampedro, Diego; Marazzi, Marco

    2016-03-01

    In spite of considerable interest in the design of molecular switches towards photo-controllable (bio)materials, few studies focused on the major influence of the surrounding environment on the switch photoreactivities. We present a combined experimental and computational study of a retinal-like molecular switch linked to a peptide, elucidating the effects on the photoreactivity and on the α-helix secondary structure. Temperature-dependent, femtosecond UV-vis transient absorption spectroscopy and high-level hybrid quantum mechanics/molecular mechanics methods were applied to describe the photoisomerization process and the subsequent peptide rearrangement. It was found that the conformational heterogeneity of the ground state peptide controls the excited state potential energy surface and the thermally activated population decay. Still, a reversible α-helix to α-hairpin conformational change is predicted, paving the way for a fine photocontrol of different secondary structure elements, hence (bio)molecular functions, using retinal-inspired molecular switches. PMID:26876376

  6. STM investigation of imine-based molecular switches on Au(111)

    Energy Technology Data Exchange (ETDEWEB)

    Mielke, Johannes; Grill, Leonhard [Institut fuer Experimentalphysik, Freie Universitaet Berlin (Germany); Luo, Ying; Haag, Rainer [Institut fuer Chemie und Biochemie - Organische Chemie, Freie Universitaet Berlin (Germany)

    2009-07-01

    In the field of molecular electronics, molecular switches are highly relevant because they can control the conductance. Switches based on azobenzene molecules have attracted large interest in the last years. A very similar molecular switch can be created by replacing the functional azo group by an imine group, which does not considerably alter the electronic structure of the molecule and conserves the capability of undergoing a reversible trans-cis isomerisation. Such processes have already been studied in solution and the gas phase but not on surfaces. In this work, imine molecules with four tert-butyl groups were adsorbed on Au(111) and their adsorption and switching behaviour were studied using a low temperature STM. The molecules were found to form two types of ordered islands and an interesting irreversible switching behaviour was observed when looking at their temperature dependence, because the number of trans isomers was reduced upon heating of the sample.

  7. Magnesium coordination controls the molecular switch function of DNA mismatch repair protein MutS

    NARCIS (Netherlands)

    J.H.G. Lebbink (Joyce); A. Fish (Alexander); A. Reumer (Annet); G. Natrajan; H.H.K. Winterwerp (Herrie); T.K. Sixma (Titia)

    2010-01-01

    textabstractThe DNA mismatch repair protein MutS acts as a molecular switch. It toggles between ADP and ATP states and is regulated by mismatched DNA. This is analogous to G-protein switches and the regulation of their "on" and "off" states by guanine exchange factors. Although GDP release in monome

  8. A pH-Sensitive Peptide-Containing Lasso Molecular Switch

    OpenAIRE

    Karine Fournel-Marotte; Caroline Clavel; Frédéric Coutrot

    2013-01-01

    The synthesis of a peptide-containing lasso molecular switch by a self-entanglement strategy is described. The interlocked [1] rotaxane molecular machine consists of a benzometaphenylene[25]crown-8 (BMP25C8) macrocycle surrounding a molecular axle. This molecular axle contains a tripeptidic sequence and two molecular stations: a N-benzyltriazolium and a pH-sensitive anilinium station. The tripeptide is located between the macrocycle and the triazolium station, so that its conformation can be ...

  9. Electronic transport properties of a molecular switch with carbon nanotube electrodes: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P., E-mail: ss_zhaop@ujn.edu.c [School of Science, University of Jinan, Jinan 250022 (China); School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Wang, P.J.; Zhang, Z. [School of Science, University of Jinan, Jinan 250022 (China); Liu, D.S. [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Department of Physics, Jining University, Qufu 273155 (China)

    2010-01-01

    We have studied the electronic transport properties of a new kind of optical molecular switch with two single-walled carbon nanotube (SWCNT) electrodes using first-principles transport calculations. It is shown that the enol form shows an overall higher conductance than the keto form at low-bias voltage, which is independent of the SWCNTs' chirality. Meantime, it is possible to tune the conductance of the molecular switch by changing the chirality of the SWCNTs.

  10. Laser Field Alignment of Organic Molecules on Semiconductor Surfaces: Toward Ultrafast Molecular Switches

    International Nuclear Information System (INIS)

    An ultrafast, nanoscale molecular switch is proposed, based on extension of the concept of nonadiabatic alignment to surface-adsorbed molecules. The switch consists of a conjugated organic molecule adsorbed onto a semiconducting surface and placed near a scanning tunneling microscope tip. A low-frequency, polarized laser field is used to switch the system by orienting the molecule with the field polarization axis, enabling conductance through the junction. Enhancement and spatial localization of the incident field by the metallic tip allow operation at low intensities. The principles of nonadiabatic alignment lead to switch on and off time scales far below rotational time scales

  11. Asymmetric Stochastic Switching Driven by Intrinsic Molecular Noise

    OpenAIRE

    David Frigola; Laura Casanellas; Sancho, José M.; Marta Ibañes

    2012-01-01

    Low-copy-number molecules are involved in many functions in cells. The intrinsic fluctuations of these numbers can enable stochastic switching between multiple steady states, inducing phenotypic variability. Herein we present a theoretical and computational study based on Master Equations and Fokker-Planck and Langevin descriptions of stochastic switching for a genetic circuit of autoactivation. We show that in this circuit the intrinsic fluctuations arising from low-copy numbers, which are i...

  12. Molecular modeling and molecular dynamics simulation of the polarization switching phenomena in the ferroelectric polymers PVDF at the nanoscale

    International Nuclear Information System (INIS)

    The molecular modeling and molecular dynamics of polarization switching for the ferroelectric films model of polyvinylidene fluoride (PVDF) are investigated at the nanoscale. We consider a molecular model of PVDF film, consisting of two and four a chains [–CH2–CF2–]n limited by n=6 elementary units. The first-principle approach is applied to the switching and kinetics of these models. Two types of behavior were established for PVDF chains: simultaneous and sequential rotation in high and low electric fields. Kinetics of sequential polarization switching shows a homogeneous critical behavior in the low electric field with a critical point at Landau–Ginzburg–Devonshire (LGD) coercive field E=EC. This type of kinetics demonstrates a kink-like behavior for polarization solitary wave propagation. The simultaneous type of kinetics demonstrates the total domain-like polarization switching, corresponding to exponential behavior of switching time in high electric field as for bulk samples. Corresponding LGD intrinsic coercive field for a two-chain and four-chains model is EC∼2.0 GV/m with revealing size effect. Obtained results show common quantum nature of PVDF chains switching phenomena—the quantum interaction of the PVDF molecular orbitals under applied electric field at the nanoscale level. The results obtained are compared with experimental data

  13. Insight into the molecular switch mechanism of human Rab5a from molecular dynamics simulations

    International Nuclear Information System (INIS)

    Rab5a is currently a most interesting target because it is responsible for regulating the early endosome fusion in endocytosis and possibly the budding process. We utilized longtime-scale molecular dynamics simulations to investigate the internal motion of the wild-type Rab5a and its A30P mutant. It was observed that, after binding with GTP, the global flexibility of the two proteins is increasing, while the local flexibility in their sensitive sites (P-loop, switch I and II regions) is decreasing. Also, the mutation of Ala30 to Pro30 can cause notable flexibility variations in the sensitive sites. However, this kind of variations is dramatically reduced after binding with GTP. Such a remarkable feature is mainly caused by the water network rearrangements in the sensitive sites. These findings might be of use for revealing the profound mechanism of the displacements of Rab5a switch regions, as well as the mechanism of the GDP dissociation and GTP association.

  14. X-ray Analyses of the Ribosomal A-Site Molecular Switches

    Science.gov (United States)

    Kondo, Jiro

    The aminoacyl-tRNA decoding site (A-site) on the small ribosomal subunit is an RNA molecular switch guaranteeing high translation fidelity. Due to the similarity of the secondary structure of the A-site, it has long been believed that the functional characteristics and tertiary structure of the A-site molecular switch are basically conserved in three main cell types, bacteria, mitochondria and eukaryotic cytoplasm. However, these three cell types are noticeably different in their biological properties such as life cycle, genome size, structural component of ribosome and number of tRNA species. In our structural studies, we have shown how a small difference of nucleotide sequences affects the dynamics of the A-site molecular switches underlying the decoding mechanism adapted to their biological properties and environments. The observed structural insights into the decoding process allowed us to understand molecular mechanisms of non-syndromic hearing loss and toxicity mechanism of aminoglycoside antibiotics.

  15. The stochastic behavior of a molecular switching circuit with feedback

    Directory of Open Access Journals (Sweden)

    Smith Eric

    2007-05-01

    Full Text Available Abstract Background Using a statistical physics approach, we study the stochastic switching behavior of a model circuit of multisite phosphorylation and dephosphorylation with feedback. The circuit consists of a kinase and phosphatase acting on multiple sites of a substrate that, contingent on its modification state, catalyzes its own phosphorylation and, in a symmetric scenario, dephosphorylation. The symmetric case is viewed as a cartoon of conflicting feedback that could result from antagonistic pathways impinging on the state of a shared component. Results Multisite phosphorylation is sufficient for bistable behavior under feedback even when catalysis is linear in substrate concentration, which is the case we consider. We compute the phase diagram, fluctuation spectrum and large-deviation properties related to switch memory within a statistical mechanics framework. Bistability occurs as either a first-order or second-order non-equilibrium phase transition, depending on the network symmetries and the ratio of phosphatase to kinase numbers. In the second-order case, the circuit never leaves the bistable regime upon increasing the number of substrate molecules at constant kinase to phosphatase ratio. Conclusion The number of substrate molecules is a key parameter controlling both the onset of the bistable regime, fluctuation intensity, and the residence time in a switched state. The relevance of the concept of memory depends on the degree of switch symmetry, as memory presupposes information to be remembered, which is highest for equal residence times in the switched states. Reviewers This article was reviewed by Artem Novozhilov (nominated by Eugene Koonin, Sergei Maslov, and Ned Wingreen.

  16. Arylazopyrazoles as Light-Responsive Molecular Switches in Cyclodextrin-Based Supramolecular Systems.

    Science.gov (United States)

    Stricker, Lucas; Fritz, Eva-Corinna; Peterlechner, Martin; Doltsinis, Nikos L; Ravoo, Bart Jan

    2016-04-01

    A simple and high yield synthesis of water-soluble arylazopyrazoles (AAPs) featuring superior photophysical properties is reported. The introduction of a carboxylic acid allows the diverse functionalization of AAPs. Based on structural modifications of the switching unit the photophysical properties of the AAPs could be tuned to obtain molecular switches with favorable photostationary states. Furthermore, AAPs form stable and light-responsive host-guest complexes with β-cyclodextrin (β-CD). Our most efficient AAP shows binding affinities comparable to azobenzenes, but more effective switching and higher thermal stability of the Z-isomer. As a proof-of-principle, we investigated two CD-based supramolecular systems, containing either cyclodextrin vesicles (CDVs) or cyclodextrin-functionalized gold nanoparticles (CDAuNPs), which revealed excellent reversible, light-responsive aggregation and dispersion behavior. To conclude, AAPs have great potential to be incorporated as molecular switches in highly demanding and multivalent photoresponsive systems. PMID:26972671

  17. Nanoscale switch based on interacting molecular dipoles: Cooperativity can improve the device characteristics

    Science.gov (United States)

    Mafé, , Salvador; Manzanares, , José A.; Reiss, Howard

    2011-02-01

    We propose a nanoscale switch, giving a nonlinear function with two conductive states separated by a sharp transition region, on the basis of an array of molecular dipoles. We show theoretically that the local interactions between dipoles result in cooperative phenomena that can significantly improve the switching characteristics. We demonstrate the general validity of the concept in the cases of (i) an electrical switch robust to the finite size and variability effects inherent to the nanoscale and (ii) a sensing layer based on the voltage and ligand concentration dependence of the dipole array conductance.

  18. Synthetic molecular machines and polymer/monomer size switches that operate through dynamic and non-dynamic covalent changes.

    Science.gov (United States)

    Stadler, Adrian-Mihail; Ramírez, Juan

    2012-01-01

    The present chapter is focused on how synthetic molecular machines (e.g. shuttles, switches and molecular motors) and size switches (conversions between polymers and their units, i.e., conversions between relatively large and small molecules) can function through covalent changes. Amongst the interesting examples of devices herein presented are molecular motors and size switches based on dynamic covalent chemistry which is an area of constitutional dynamic chemistry. PMID:22169959

  19. Molecular Epigenetic Switches in Neurodevelopment in Health and Disease

    Directory of Open Access Journals (Sweden)

    Dietmar Spengler

    2015-05-01

    Full Text Available Epigenetic mechanisms encode information above and beyond DNA sequence and play a critical role in brain development and the long-lived effects of environmental cues on the pre- and postnatal brain. Switch-like, rather than graded changes, illustrate par excellence how epigenetic events perpetuate altered activity states in the absence of the initial cue. They occur from early neural development to maturation and can give rise to distinct diseases upon deregulation. Many neurodevelopmental genes harbor bivalently marked chromatin domains, states of balanced inhibition, which guide dynamic ‘ON or OFF’ decisions once the balance is tilted in response to developmental or environmental cues. Examples discussed in this review include neuronal differentiation of embryonic stem cells into progenitors and beyond, activation of Kiss1 at puberty onset, and early experience-dependent programming of Avp, a major stress gene. At the genome-scale, genomic imprinting can be epigenetically switched on or off at select genes in a tightly controlled temporospatial manner and provides a versatile mechanism for dosage regulation of genes with important roles in stem cell quiescence or differentiation. Moreover, retrotransposition in neural progenitors provides an intriguing example of an epigenetic-like switch, which is stimulated by bivalently marked neurodevelopmental genes and possibly results in increased genomic flexibility regarding unprecedented challenge. Overall, we propose that epigenetic switches illuminate the catalyzing function of epigenetic mechanisms in guiding dynamic changes in gene expression underpinning robust transitions in cellular and organismal phenotypes as well as in the mediation between dynamically changing environments and the static genetic blueprint.

  20. Light controlled charge carrier mobilities on polymer chains. Towards a molecular switch

    Czech Academy of Sciences Publication Activity Database

    Sworakowski, J.; Nešpůrek, Stanislav; Wang, Geng; Weiter, M.

    Saclay: Atomic Energy Research Centre, Saclay, 2003. s. 131. [European Conference on Molecular Electronics /7./. 10.09.2003-14.09.2003, Avignon] R&D Projects: GA MŠk OC D14.30 Grant ostatní: Polish State Committee for Sci. Res.(PL) T09A 132 22 Institutional research plan: CEZ:AV0Z4050913 Keywords : molecular switch * molecular wire * poly[methyl-(phenyl)silylene] Subject RIV: BM - Solid Matter Physics ; Magnetism

  1. Molecular circuits, biological switches, and nonlinear dose-response relationships.

    OpenAIRE

    Andersen, Melvin E.; Yang, Raymond S.H.; French, C. Tenley; Chubb, Laura S; Dennison, James E

    2002-01-01

    Signaling motifs (nuclear transcriptional receptors, kinase/phosphatase cascades, G-coupled protein receptors, etc.) have composite dose-response behaviors in relation to concentrations of protein receptors and endogenous signaling molecules. "Molecular circuits" include the biological components and their interactions that comprise the workings of these signaling motifs. Many of these molecular circuits have nonlinear dose-response behaviors for endogenous ligands and for exogenous toxicants...

  2. Two-terminal nanoelectromechanical bistable switches based on molybdenum-sulfur-iodine molecular wire bundles

    Science.gov (United States)

    Andzane, J.; Prikulis, J.; Dvorsek, D.; Mihailovic, D.; Erts, D.

    2010-03-01

    We demonstrate the application of Mo6S3I6 molecular wire bundles for electrically controllable two-terminal on-off switches. We investigate how changes in the contact electrode material and geometry influence the device characteristics, hysteretic switching behavior and device stability. We also determine the device operating parameters, particularly the Young's moduli (40-270 GPa), operating current densities (3.2 × 105-7 × 106 A m - 2) and force constants. Although qualitatively, the properties of Mo6S3I6 nanowires in nanoelectromechanical (NEM) switches are similar to those of carbon nanotubes (CNTs), their lower friction coefficient, higher mechanical stability and higher operation voltages give specific advantages in terms of smaller differences in on-off operating potentials, higher switching speeds and lower energy consumption than CNTs, which are critical for applications in NEM devices.

  3. Two-terminal nanoelectromechanical bistable switches based on molybdenum-sulfur-iodine molecular wire bundles

    International Nuclear Information System (INIS)

    We demonstrate the application of Mo6S3I6 molecular wire bundles for electrically controllable two-terminal on-off switches. We investigate how changes in the contact electrode material and geometry influence the device characteristics, hysteretic switching behavior and device stability. We also determine the device operating parameters, particularly the Young's moduli (40-270 GPa), operating current densities (3.2 x 105-7 x 106 A m-2) and force constants. Although qualitatively, the properties of Mo6S3I6 nanowires in nanoelectromechanical (NEM) switches are similar to those of carbon nanotubes (CNTs), their lower friction coefficient, higher mechanical stability and higher operation voltages give specific advantages in terms of smaller differences in on-off operating potentials, higher switching speeds and lower energy consumption than CNTs, which are critical for applications in NEM devices.

  4. Hydrochromic molecular switches for water-jet rewritable paper

    Science.gov (United States)

    Sheng, Lan; Li, Minjie; Zhu, Shaoyin; Li, Hao; Xi, Guan; Li, Yong-Gang; Wang, Yi; Li, Quanshun; Liang, Shaojun; Zhong, Ke; Zhang, Sean Xiao-An

    2014-01-01

    The days of rewritable paper are coming, printers of the future will use water-jet paper. Although several kinds of rewritable paper have been reported, practical usage of them is rare. Herein, a new rewritable paper for ink-free printing is proposed and demonstrated successfully by using water as the sole trigger to switch hydrochromic dyes on solid media. Water-jet prints with various colours are achieved with a commercial desktop printer based on these hydrochromic rewritable papers. The prints can be erased and rewritten dozens of times with no significant loss in colour quality. This rewritable paper is promising in that it can serve an eco-friendly information display to meet the increasing global needs for environmental protection.

  5. Infrared spectroscopic characterization of [2]rotaxane molecular switch tunnel junction devices.

    Science.gov (United States)

    DeIonno, Erica; Tseng, Hsian-Rong; Harvey, Desmond D; Stoddart, J Fraser; Heath, James R

    2006-04-20

    Langmuir-Blodgett monolayers of a bistable [2]rotaxane were prepared at packing densities of 118, 73, and 54 A(2)/molecule. The monolayers were both characterized via infrared spectroscopy before and after evaporation of a 2 nm film of titanium and incorporated into molecular switch tunnel junction devices. The study suggests that the evaporation process primarily affects portions of the molecule exposed to the metal atom source. Thus, in tightly packed monolayers (73 and 54 A(2)/molecule), only the portions of the [2]rotaxane that are present at the molecule/air interface are clearly affected, leaving key functionality necessary for switching intact. Monolayers transferred at a lower pressure (118 A(2)/molecule) exhibit nonspecific damage and poor switching behavior following Ti deposition. These results indicate that tightly packed monolayers and sacrificial functionality displayed at the molecule/air interface are important design principles for molecular electronic devices. PMID:16610848

  6. Deciphering mechanism of the 'myristoyl switch' with classical and accelerated molecular dynamics

    Czech Academy of Sciences Publication Activity Database

    Magarkar, Aniket; Kohagen, Miriam; Jungwirth, Pavel

    2015-01-01

    Roč. 44, Suppl 1 (2015), S169. ISSN 0175-7571. [EBSA European Biophysics Congress /10./. 18.07.2015-22.07.2015, Dresden] Institutional support: RVO:61388963 Keywords : molecular dynamics * myristoyl switch * calcium ion binding Subject RIV: CF - Physical ; Theoretical Chemistry

  7. Chemical Talking with Living Systems: Molecular Switches Steer Quorum Sensing in Bacteria.

    Science.gov (United States)

    Schweighauser, Luca; Wegner, Hermann A

    2015-08-17

    New avenues in bacterial engineering: An azobenzene molecular switch has been incorporated into an autoinducer for quorum sensing (QS) in bacteria. The authors demonstrated that irradiation with different wavelengths of light influences the QS system thereby controlling gene expression as well as the phenotype, as exemplified by pyocyanin production. PMID:26078043

  8. Understanding and Controlling Regime Switching in Molecular Diffusion

    OpenAIRE

    Hallerberg, S.; de Wijn, A. S.

    2013-01-01

    Diffusion can be strongly affected by ballistic flights (long jumps) as well as long-lived sticking trajectories (long sticks). Using statistical inference techniques in the spirit of Granger causality, we investigate the appearance of long jumps and sticks in molecular-dynamics simulations of diffusion in a prototype system, a benzene molecule on a graphite substrate. We find that specific fluctuations in certain, but not all, internal degrees of freedom of the molecule can be linked to eith...

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

    International Nuclear Information System (INIS)

    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

  10. Adsorption and switching properties of a N-benzylideneaniline based molecular switch on a Au(111) surface

    International Nuclear Information System (INIS)

    High resolution electron energy loss spectroscopy has been employed to analyze the adsorption geometry and the photoisomerization ability of the molecular switch carboxy-benzylideneaniline (CBA) adsorbed on Au(111). CBA on Au(111) adopts a planar (trans) configuration in the first monolayer (ML) as well as for higher coverages (up to 6 ML), in contrast to the strongly nonplanar geometry of the molecule in solution. Illumination with UV light of CBA in direct contact with the Au(111) surface (≤1 ML) caused no changes in the vibrational structure, whereas at higher coverages (>1 ML) pronounced modifications of vibrational features were observed, which we assign to a trans→cis isomerization. Thermal activation induced the back reaction to trans-CBA. We propose that the photoisomerization is driven by a direct (intramolecular) electronic excitation of the adsorbed CBA molecules in the second ML (and above) analogous to CBA in the liquid phase.

  11. Investigation of a metal-organic interface. Realization and understanding of a molecular switch

    Energy Technology Data Exchange (ETDEWEB)

    Neucheva, Olga [Forschungszentrum Juelich (DE). Institute of Bio- and Nanosystems (IBN), Functional Nanostructures at Surfaces (IBN-3)

    2010-07-01

    The field of molecular organic electronics is an emerging and very dynamic area. The continued trend to miniaturisation, combined with increasing complexity and cost of production in conventional semiconductor electronics, forces companies to turn their attention to alternatives that promise the next levels of scale at significantly lower cost. After consumer electronic devices based on organic transistors, such as TVs and book readers, have already been presented, molecular electronics is expected to offer the next breakthrough in feature size. Unfortunately, most of the organic/metal interfaces contain intrinsic defects that break the homogeneity of the interface properties. In this thesis, the electronic and structural properties of such defects were examined in order to understand the influence of the inhomogeneities on the quality of the interface layer. However, the main focus of this work was the investigation of the local properties of a single molecule. Taking advantage of the Scanning Tunnelling Microscope's (STM's) ability to act as a local probe, a single molecular switch was realized and studied. Moreover, in close collaboration with theory groups, the underlying mechanism driving the switching process was identified and described. Besides the investigation of the switching process, the ability of the STM to build nanostructures of different shapes from large organic molecules was shown. Knowing the parameters for realization and control of the switching process and for building the molecular corrals, the results of this investigation enable the reconstruction of the studied molecular ensemble and its deployment in electric molecular circuits, constituting a next step towards further miniaturization of electronic devices. (orig.)

  12. Quantum current of a molecular photo-switch between two graphene sheets

    Science.gov (United States)

    Brivio, G. P.; Motta, C.; Trioni, M. I.; Sebastian, K. L.

    2011-03-01

    Light responsive materials that reversibly change shape under alternate UV and visible irradiation have attracted much interest because they can be used as optical switches, since the isomers show different features in the dimension, HOMO-LUMO gap and transmission spectrum. In view to integrate the photo-switch in the carbon based electronics devices, the conductance of a system constituted by a photochromic molecule between two graphene electrodes is investigated. In this work the conductance of the junction formed by diarylperfluorocyclopentene between two semi-infinite graphene sheets was computed using the non-equilibrium Green's function method combined with density functional theory via the TranSiesta code. The results emphasize the role of the graphene and the molecular electronic states in the switching behaviour of this hybrid system.

  13. The importance of the rotor in hydrazone-based molecular switches

    Directory of Open Access Journals (Sweden)

    Xin Su

    2012-06-01

    Full Text Available The pH-activated E/Z isomerization of a series of hydrazone-based systems having different functional groups as part of the rotor (R = COMe, CN, Me, H, was studied. The switching efficiency of these systems was compared to that of a hydrazone-based molecular switch (R = COOEt whose E/Z isomerization is fully reversible. It was found that the nature of the R group is critical for efficient switching to occur; the R group should be a moderate H-bond acceptor in order to (i provide enough driving force for the rotor to move upon protonation, and (ii stabilize the obtained Z configuration, to achieve full conversion.

  14. Single Molecule Switches and Molecular Self-Assembly: Low Temperature STM Investigations and Manipulations

    International Nuclear Information System (INIS)

    This dissertation is devoted to single molecule investigations and manipulations of two porphyrin-based molecules, chlorophyll-a and Co-popphyrin. The molecules are absorbed on metallic substrates and studied at low temperatures using a scanning tunneling microscope. The electronic, structural and mechanical properties of the molecules are investigated in detail with atomic level precision. Chlorophyll-a is the key ingredient in photosynthesis processes while Co-porphyrin is a magnetic molecule that represents the recent emerging field of molecular spintronics. Using the scanning tunneling microscope tip and the substrate as electrodes, and the molecules as active ingredients, single molecule switches made of these two molecules are demonstrated. The first switch, a multiple and reversible mechanical switch, is realized by using chlorophyll-a where the energy transfer of a single tunneling electron is used to rotate a C-C bond of the molecule's tail on a Au(111) surface. Here, the det

  15. Ab initio theory for current-induced molecular switching: Melamine on Cu(001)

    KAUST Repository

    Ohto, Tatsuhiko

    2013-05-28

    Melamine on Cu(001) is mechanically unstable under the current of a scanning tunneling microscope tip and can switch among configurations. However, these are not equally accessible, and the switching critical current depends on the bias polarity. In order to explain such rich phenomenology, we have developed a scheme to evaluate the evolution of the reaction paths and activation barriers as a function of bias, which is rooted in the nonequilibrium Green\\'s function method implemented within density functional theory. This, combined with the calculation of the inelastic electron tunneling spectroscopy signal, allows us to identify the vibrational modes promoting the observed molecular conformational changes. Finally, once our ab initio results are used within a resonance model, we are able to explain the details of the switching behavior, such as its dependence on the bias polarity, and the noninteger power relation between the reaction rate constants and both the bias voltage and the electric current. © 2013 American Physical Society.

  16. Understanding and controlling regime switching in molecular diffusion

    Science.gov (United States)

    Hallerberg, S.; de Wijn, A. S.

    2014-12-01

    Diffusion can be strongly affected by ballistic flights (long jumps) as well as long-lived sticking trajectories (long sticks). Using statistical inference techniques in the spirit of Granger causality, we investigate the appearance of long jumps and sticks in molecular-dynamics simulations of diffusion in a prototype system, a benzene molecule on a graphite substrate. We find that specific fluctuations in certain, but not all, internal degrees of freedom of the molecule can be linked to either long jumps or sticks. Furthermore, by changing the prevalence of these predictors with an outside influence, the diffusion of the molecule can be controlled. The approach presented in this proof of concept study is very generic and can be applied to larger and more complex molecules. Additionally, the predictor variables can be chosen in a general way so as to be accessible in experiments, making the method feasible for control of diffusion in applications. Our results also demonstrate that data-mining techniques can be used to investigate the phase-space structure of high-dimensional nonlinear dynamical systems.

  17. Single molecular switch based on thiol tethered iron(II)clathrochelate on gold

    International Nuclear Information System (INIS)

    Molecular electronics has been associated with high density nano-electronic devices. Developments of molecular electronic devices were based on reversible switching of molecules between the two conductive states. In this paper, self-assembled monolayers of dodecanethiol (DDT) and thiol tethered iron(II)clathrochelate (IC) have been prepared on gold film. The electrochemical and electronic properties of IC molecules inserted into the dodecanethiol monolayer (IC-DDT SAM) were investigated using voltammetric, electrochemical impedance spectroscopy (EIS), scanning tunneling microscopy (STM) and cross-wire tunneling measurements. The voltage triggered switching behaviour of IC molecules on mixed SAM was demonstrated. Deposition of polyaniline on the redox sites of IC-DDT SAM using electrochemical polymerization of aniline was performed in order to confirm that this monolayer acts as nano-patterned semiconducting electrode surface.

  18. The Limiting Dynamics of a Bistable Molecular Switch With and Without Noise

    OpenAIRE

    Mackey, Michael C.; Tyran-Kaminska, Marta

    2015-01-01

    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 s...

  19. Research Update: Molecular electronics: The single-molecule switch and transistor

    Directory of Open Access Journals (Sweden)

    Kai Sotthewes

    2014-01-01

    Full Text Available In order to design and realize single-molecule devices it is essential to have a good understanding of the properties of an individual molecule. For electronic applications, the most important property of a molecule is its conductance. Here we show how a single octanethiol molecule can be connected to macroscopic leads and how the transport properties of the molecule can be measured. Based on this knowledge we have realized two single-molecule devices: a molecular switch and a molecular transistor. The switch can be opened and closed at will by carefully adjusting the separation between the electrical contacts and the voltage drop across the contacts. This single-molecular switch operates in a broad temperature range from cryogenic temperatures all the way up to room temperature. Via mechanical gating, i.e., compressing or stretching of the octanethiol molecule, by varying the contact's interspace, we are able to systematically adjust the conductance of the electrode-octanethiol-electrode junction. This two-terminal single-molecule transistor is very robust, but the amplification factor is rather limited.

  20. 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. PMID:26692266

  1. Age-associated Cognitive Decline: Insights into Molecular Switches and Recovery Avenues

    Science.gov (United States)

    Konar, Arpita; Singh, Padmanabh; Thakur, Mahendra K.

    2016-01-01

    Age-associated cognitive decline is an inevitable phenomenon that predisposes individuals for neurological and psychiatric disorders eventually affecting the quality of life. Scientists have endeavored to identify the key molecular switches that drive cognitive decline with advancing age. These newly identified molecules are then targeted as recovery of cognitive aging and related disorders. Cognitive decline during aging is multi-factorial and amongst several factors influencing this trajectory, gene expression changes are pivotal. Identifying these genes would elucidate the neurobiological underpinnings as well as offer clues that make certain individuals resilient to withstand the inevitable age-related deteriorations. Our laboratory has focused on this aspect and investigated a wide spectrum of genes involved in crucial brain functions that attribute to senescence induced cognitive deficits. We have recently identified master switches in the epigenome regulating gene expression alteration during brain aging. Interestingly, these factors when manipulated by chemical or genetic strategies successfully reverse the age-related cognitive impairments. In the present article, we review findings from our laboratory and others combined with supporting literary evidences on molecular switches of brain aging and their potential as recovery targets.

  2. Photocontrolled Reversible Luminescent Lanthanide Molecular Switch Based on a Diarylethene-Europium Dyad.

    Science.gov (United States)

    Cheng, Hong-Bo; Hu, Guo-Fei; Zhang, Zhan-Hui; Gao, Liang; Gao, Xingfa; Wu, Hai-Chen

    2016-08-15

    A new europium complex coordinated between a Eu(III) ion and an unsymmetrical diarylperfluorocyclopentene yields a light-controlled diarylethene-europium dyad, DAE@TpyEu(tta)3, whose photophysical properties can be reversibly switched by optical stimuli. When DAE@TpyEu(tta)3 is exposed to 365 nm UV light, an efficient intramolecular photochromic fluorescence resonance energy transfer (pc-FRET) occurs between the emission of the Eu(3+) donor (D) and the absorption of the diarylethene acceptor (A) in closed-form DAE@TpyEu(tta)3 accompanied by luminescence quenching. However, the pc-FRET process could be effectively inhibited by visible light (λ > 600 nm) irradiation, and the lanthanide emission of DAE@TpyEu(tta)3 is rapidly recovered. Furthermore, this luminescent lanthanide molecular switch could serve as a highly reliable and sensitive "turn on" fluorescent marker in living cells irradiated by red light without any optical interference. PMID:27447742

  3. 'Molecular switch' vectors for hypoxia- and radiation-mediated gene therapy of cancer

    International Nuclear Information System (INIS)

    Intratumoral areas of low oxygen concentration are known to be refractive to radiotherapy treatment. However, this physiological condition can be exploited for selective cancer gene therapy. We have developed a series of synthetic promoters selectively responsive to both hypoxia and ionizing radiation (IR). These promoters contain hypoxia regulatory elements (HREs) from the erythropoietin (Epo), the phosphoglycerate kinase1(PGK1) and vascular endothelial growth factor (VEGF) genes, and/or IR-responsive CArG elements from the Early Growth Response 1 (Egr1) gene. The HRE and CArG promoters were able to regulate expression of reporter and suicide genes in human tumor cells, following corresponding stimulation with hypoxia (0.1% O2) or X-irradiation (5Gy) [Greco et al, 2002, Gene Therapy 9:1403]. Furthermore, the chimeric HRE + CArG promoters could be activated by these stimuli independently or even more significantly when given in combination, with the Epo HRE/CArG promoter proving to be the most responsive and robust. In order to amplify and maintain transgene expression even following withdrawal of the triggering stimuli, we have developed a 'molecular switch' system [Scott et al, 2000, Gene Therapy 7:1121]. This 'switch' system has now been engineered as a single vector molecule, containing HRE and CArG promoters. This new series of HRE/CArG switch vectors have been tested in a herpes simplex thymidine kinase (HSVtk)/ganciclovir (GCV) suicide gene assay. Results indicate that a) higher and more selective tumor cell kill is achieved with the switch when compared with the HRE and CArG promoters directly driving HSVtk expression and b) the Epo HRE/CArG switch vectors appear to function as efficiently as the strong constitutive cytomegalovirus (CMV) promoter construct

  4. Transient photocurrent in molecular junctions: singlet switching on and triplet blocking.

    Science.gov (United States)

    Petrov, E G; Leonov, V O; Snitsarev, V

    2013-05-14

    The kinetic approach adapted to describe charge transmission in molecular junctions, is used for the analysis of the photocurrent under conditions of moderate light intensity of the photochromic molecule. In the framework of the HOMO-LUMO model for the single electron molecular states, the analytic expressions describing the temporary behavior of the transient and steady state sequential (hopping) as well as direct (tunnel) current components have been derived. The conditions at which the current components achieve their maximal values are indicated. It is shown that if the rates of charge transmission in the unbiased molecular diode are much lower than the intramolecular singlet-singlet excitation/de-excitation rate, and the threefold degenerated triplet excited state of the molecule behaves like a trap blocking the charge transmission, a possibility of a large peak-like transient switch-on photocurrent arises. PMID:23676066

  5. Novel tailor-made externally triggerable single-molecular switches for molecular electronics

    OpenAIRE

    Harzmann, Gero

    2015-01-01

    Molecular electronics marks a highly interdisciplinary scientific field, in which physicists, chemists, and biologist jointly investigate electronic phenomena on a molecular level. Herein, the foremost task of the chemist is the design and synthesis of novel, tailor-made model compounds bearing externally addressable or controllable functions, which are predominantly of electronic nature. This present PhD thesis mainly focusses on the synthetic aspects towards innovative metalorga...

  6. A molecular beacon-based DNA switch for reversible pH sensing in vesicles and live cells.

    Science.gov (United States)

    Narayanaswamy, Nagarjun; Nair, Raji R; Suseela, Y V; Saini, Deepak Kumar; Govindaraju, T

    2016-07-01

    In this Communication, a molecular beacon-based DNA switch (LMB) is developed as an efficient and reversible pH sensing probe. Remarkably, LMB exhibited reversible structural transition between the closed (molecular beacon) and open (A-motif) states very efficiently in synthetic vesicles and live cells without the need for any transfection agents. PMID:27338808

  7. Electron induced conformational changes of imine-based molecular switches on a Au(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Lotze, Christian; Pascual, Jose Ignacio [Inst. f. Experimentalphysik, Freie Universitaet Berlin (Germany); Luo, Ying; Haag, Rainer [Inst. f. Organische Chemie, Freie Universitaet Berlin (Germany)

    2010-07-01

    Organic molecules exhibiting controllable reversible transitions between isomeric states on surfaces promise an enormous potential in the field of molecular electronics. The reversible cis-trans isomerization of azobenzene-like molecules is often hindered by a strong interaction of the nitrogen lone-pair electrons of the di-azo bridge (-N=N-) with the substrate. In order to improve the isomerization capabilities, the di-azo bridge is substituted by an imine-group (-N=CH-). Here, we use low-temperature scanning tunneling microscopy to investigate a sub-monolayer of the newly designed imine-based molecular switch NPCI on a Au(111) surface. Its carboxylic termination mediates the formation of hydrogen-bonded dimers, which align in rows along the herringbone reconstruction. We were able to induce reversible conformational changes with the tunneling electrons from the STM tip and determine its efficiency as a function of electron energy.

  8. Ferroelectric molecular field-switch based on double proton transfer process: Static and dynamical simulations

    Science.gov (United States)

    Rode, Michał F.; Jankowska, Joanna; Sobolewski, Andrzej L.

    2016-04-01

    In this work, we present a reversible ferroelectric molecular switch controlled by an external electric field. The studied (2Z)-1-(6-((Z)-2-hydroxy-2-phenylvinyl)pyridin-3-yl)-2-(pyridin-2(1H)-ylidene)ethanone (DSA) molecule is polarized by two uniaxial intramolecular hydrogen bonds. Two protons can be transferred along hydrogen bonds upon an electric field applied along the main molecular axis. The process results in reversion of the dipole moment of the system. Static ab initio and on-the-fly dynamical simulations of the DSA molecule placed in an external electric field give insight into the mechanism of the double proton transfer (DPT) in the system and allow for estimation of the time scale of this process. The results indicate that with increasing strength of the electric field, the step-wise mechanism of DPT changes into the downhill barrierless process in which the synchronous and asynchronous DPTs compete with each other.

  9. Simultaneous and coordinated rotational switching of all molecular rotors in a network.

    Science.gov (United States)

    Zhang, Y; Kersell, H; Stefak, R; Echeverria, J; Iancu, V; Perera, U G E; Li, Y; Deshpande, A; Braun, K-F; Joachim, C; Rapenne, G; Hla, S-W

    2016-08-01

    A range of artificial molecular systems has been created that can exhibit controlled linear and rotational motion. In the further development of such systems, a key step is the addition of communication between molecules in a network. Here, we show that a two-dimensional array of dipolar molecular rotors can undergo simultaneous rotational switching when applying an electric field from the tip of a scanning tunnelling microscope. Several hundred rotors made from porphyrin-based double-decker complexes can be simultaneously rotated when in a hexagonal rotor network on a Cu(111) surface by applying biases above 1 V at 80 K. The phenomenon is observed only in a hexagonal rotor network due to the degeneracy of the ground-state dipole rotational energy barrier of the system. Defects are essential to increase electric torque on the rotor network and to stabilize the switched rotor domains. At low biases and low initial rotator angles, slight reorientations of individual rotors can occur, resulting in the rotator arms pointing in different directions. Analysis reveals that the rotator arm directions are not random, but are coordinated to minimize energy via crosstalk among the rotors through dipolar interactions. PMID:27159740

  10. Molecular and Supramolecular Information Processing From Molecular Switches to Unconventional Computing

    CERN Document Server

    Katz, Evgeny

    2012-01-01

    Edited by a renowned and much cited chemist, this book covers the whole span of molecular computers that are based on non-biological systems. The contributions by all the major scientists in the field provide an excellent overview of the latest developments in this rapidly expanding area. A must-have for all researchers working on this very hot topic. Perfectly complements Biomolecular Information Processing, also by Prof. Katz, and available as a two-volume set.

  11. Photoisomerization dynamics of a rhodopsin-based molecule (potential molecular switch) with high quantum yields

    Science.gov (United States)

    Allen, Roland; Jiang, Chen-Wei; Zhang, Xiu-Xing; Fang, Ai-Ping; Li, Hong-Rong; Xie, Rui-Hua; Li, Fu-Li

    2015-03-01

    It is worthwhile to explore the detailed reaction dynamics of various candidates for molecular switches, in order to understand, e.g., the differences in quantum yields and switching times. Here we report density-functional-based simulations for the rhodopsin-based molecule 4-[4-Methylbenzylidene]-5-p-tolyl-3,4-dihydro-2H-pyrrole (MDP), synthesized by Sampedro et al. We find that the photoisomerization quantum yields are remarkably high: 82% for cis-to-trans, and 68% for trans-to-cis. The lifetimes of the S1 excited state in cis-MDP in our calculations are in the range of 900-1800 fs, with a mean value of 1270 fs, while the range of times required for full cis-to-trans isomerization are 1100-2000 fs, with a mean value of 1530 fs. In trans-MDP, the calculated S1 excited state lifetimes are 860-2140 fs, with a mean value of 1330 fs, and with the full trans-to-cis isomerization completed about 200 fs later. In both cases, the dominant reaction mechanism is rotation around the central C =C bond (connected to the pyrroline ring), and de-excitation occurs at an avoided crossing between the ground state and the lowest singlet state, near the midpoint of the rotational pathway. Research Fund for the Doctoral Program of Higher Education of China; Fundamental Research Funds for the Central Universities; Robert A. Welch Foundation; National Natural Science Foundation of China.

  12. Selective detection of fenaminosulf via a molecularly imprinted fluorescence switch and silver nano-film amplification.

    Science.gov (United States)

    Li, Shuhuai; Yin, Guihao; Zhang, Qun; Li, Chunli; Luo, Jinhui; Xu, Zhi; Qin, Anli

    2015-09-15

    A novel fluorescence switch sensor was constructed for detecting the fungicide fenaminosulf (FM), based on a dye-doped molecularly imprinted polymer (MIP) and silver nanofilm amplification. The MIP was prepared by electropolymerization of hydroquinone doped with neutral red on the silver nanofilm modified electrode. A fluorescence signal was produced by the neutral red and the fluorescence intensity was diminished by the ion pair that formed via electrostatic forces between FM and the dye. Therefore, elution and adsorption of FM by the MIP acted as a switch to control the fluorescence intensity, which was effectively amplified by the silver nanofilm. The decrease in fluorescence intensity was linear with the FM concentration, establishing a new method for FM detection. Under optimal conditions, good linear correlation was obtained for FM concentrations over the range from 2.0 × 10(-10) to 4.0 × 10(-8)mol/L, with a detection limit of 1.6 × 10(-11)mol/L. This method was utilized to determine residual FM in vegetable samples, and recoveries ranging from 92.0% to 110% were obtained. PMID:25930004

  13. Photoinduced reversible switching of porosity in molecular crystals based on star-shaped azobenzene tetramers

    Science.gov (United States)

    Baroncini, Massimo; D'Agostino, Simone; Bergamini, Giacomo; Ceroni, Paola; Comotti, Angiolina; Sozzani, Piero; Bassanetti, Irene; Grepioni, Fabrizia; Hernandez, Taylor M.; Silvi, Serena; Venturi, Margherita; Credi, Alberto

    2015-08-01

    The development of solid materials that can be reversibly interconverted by light between forms with different physico-chemical properties is of great interest for separation, catalysis, optoelectronics, holography, mechanical actuation and solar energy conversion. Here, we describe a series of shape-persistent azobenzene tetramers that form porous molecular crystals in their E-configuration, the porosity of which can be tuned by changing the peripheral substituents on the molecule. Efficient E→Z photoisomerization of the azobenzene units takes place in the solid state and converts the crystals into a non-porous amorphous melt phase. Crystallinity and porosity are restored upon Z→E isomerization promoted by visible light irradiation or heating. We demonstrate that the photoisomerization enables reversible on/off switching of optical properties such as birefringence as well as the capture of CO2 from the gas phase. The linear design, structural versatility and synthetic accessibility make this new family of materials potentially interesting for technological applications.

  14. Photodynamic activation as a molecular switch to promote osteoblast cell differentiation via AP-1 activation.

    Science.gov (United States)

    Kushibiki, Toshihiro; Tu, Yupeng; Abu-Yousif, Adnan O; Hasan, Tayyaba

    2015-01-01

    In photodynamic therapy (PDT), cells are impregnated with a photosensitizing agent that is activated by light irradiation, thereby photochemically generating reactive oxygen species (ROS). The amounts of ROS produced depends on the PDT dose and the nature of the photosensitizer. Although high levels of ROS are cytotoxic, at physiological levels they play a key role as second messengers in cellular signaling pathways, pluripotency, and differentiation of stem cells. To investigate further the use of photochemically triggered manipulation of such pathways, we exposed mouse osteoblast precursor cells and rat primary mesenchymal stromal cells to low-dose PDT. Our results demonstrate that low-dose PDT can promote osteoblast differentiation via the activation of activator protein-1 (AP-1). Although PDT has been used primarily as an anti-cancer therapy, the use of light as a photochemical "molecular switch" to promote differentiation should expand the utility of this method in basic research and clinical applications. PMID:26279470

  15. Contribution of the metal/SiO2 interface potential to photoinduced switching in molecular single-electron tunneling junctions

    International Nuclear Information System (INIS)

    Photoinduced switching of the Coulomb staircase in molecular single-electron tunneling junctions was previously observed. These junctions consisted of evaporated SiO2 insulator (∼5 nm), with tetrakis-3,5-di-t-butylphenyl-porphyrin (H2-TBPP) molecules as Coulomb islands, sandwiched between top and bottom electrodes. The reversible response and the relaxation time of the photoinduced switching suggest that this phenomenon depends on the properties of the metal/SiO2 interface rather than those of the H2-TBPP molecule or SiO2 tunneling layer. We analyzed the photoinduced switching according to the theory of single-electron tunneling taking into account the discrete molecular energy states and the metal/SiO2 interfacial electrostatic phenomena. We conclude that the main contributor to the photoinduced shift was the electrostatic potential formed through the space-charge exchange at the metal/SiO2 interface

  16. Mucosal transmissibility, disease induction and coreceptor switching of R5 SHIVSF162P3N molecular clones in rhesus macaques

    OpenAIRE

    Ren Wuze; Mumbauer Alexandra; Zhuang Ke; Harbison Carole; Knight Heather; Westmoreland Susan; Gettie Agegnehu; Blanchard James; Cheng-Mayer Cecilia

    2013-01-01

    Abstract Background Mucosally transmissible and pathogenic CCR5 (R5)-tropic simian-human immunodeficiency virus (SHIV) molecular clones are useful reagents to identity neutralization escape in HIV-1 vaccine experiments and to study the envelope evolutionary process and mechanistic basis for coreceptor switch during the course of natural infection. Results We observed progression to AIDS in rhesus macaques infected intrarectally with molecular clones of the pathogenic R5 SHIVSF162P3N isolate. ...

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

    NARCIS (Netherlands)

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

    2003-01-01

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

  18. A dynamic view of molecular switch behavior at serotonin receptors: implications for functional selectivity.

    Science.gov (United States)

    Martí-Solano, Maria; Sanz, Ferran; Pastor, Manuel; Selent, Jana

    2014-01-01

    Functional selectivity is a property of G protein-coupled receptors that allows them to preferentially couple to particular signaling partners upon binding of biased agonists. Publication of the X-ray crystal structure of serotonergic 5-HT1B and 5-HT2B receptors in complex with ergotamine, a drug capable of activating G protein coupling and β-arrestin signaling at the 5-HT1B receptor but clearly favoring β-arrestin over G protein coupling at the 5-HT2B subtype, has recently provided structural insight into this phenomenon. In particular, these structures highlight the importance of specific residues, also called micro-switches, for differential receptor activation. In our work, we apply classical molecular dynamics simulations and enhanced sampling approaches to analyze the behavior of these micro-switches and their impact on the stabilization of particular receptor conformational states. Our analysis shows that differences in the conformational freedom of helix 6 between both receptors could explain their different G protein-coupling capacity. In particular, as compared to the 5-HT1B receptor, helix 6 movement in the 5-HT2B receptor can be constrained by two different mechanisms. On the one hand, an anchoring effect of ergotamine, which shows an increased capacity to interact with the extracellular part of helices 5 and 6 and stabilize them, hinders activation of a hydrophobic connector region at the center of the receptor. On the other hand, this connector region in an inactive conformation is further stabilized by unconserved contacts extending to the intracellular part of the 5-HT2B receptor, which hamper opening of the G protein binding site. This work highlights the importance of considering receptor capacity to adopt different conformational states from a dynamic perspective in order to underpin the structural basis of functional selectivity. PMID:25313636

  19. A dynamic view of molecular switch behavior at serotonin receptors: implications for functional selectivity.

    Directory of Open Access Journals (Sweden)

    Maria Martí-Solano

    Full Text Available Functional selectivity is a property of G protein-coupled receptors that allows them to preferentially couple to particular signaling partners upon binding of biased agonists. Publication of the X-ray crystal structure of serotonergic 5-HT1B and 5-HT2B receptors in complex with ergotamine, a drug capable of activating G protein coupling and β-arrestin signaling at the 5-HT1B receptor but clearly favoring β-arrestin over G protein coupling at the 5-HT2B subtype, has recently provided structural insight into this phenomenon. In particular, these structures highlight the importance of specific residues, also called micro-switches, for differential receptor activation. In our work, we apply classical molecular dynamics simulations and enhanced sampling approaches to analyze the behavior of these micro-switches and their impact on the stabilization of particular receptor conformational states. Our analysis shows that differences in the conformational freedom of helix 6 between both receptors could explain their different G protein-coupling capacity. In particular, as compared to the 5-HT1B receptor, helix 6 movement in the 5-HT2B receptor can be constrained by two different mechanisms. On the one hand, an anchoring effect of ergotamine, which shows an increased capacity to interact with the extracellular part of helices 5 and 6 and stabilize them, hinders activation of a hydrophobic connector region at the center of the receptor. On the other hand, this connector region in an inactive conformation is further stabilized by unconserved contacts extending to the intracellular part of the 5-HT2B receptor, which hamper opening of the G protein binding site. This work highlights the importance of considering receptor capacity to adopt different conformational states from a dynamic perspective in order to underpin the structural basis of functional selectivity.

  20. A novel colorimetric triple-helix molecular switch aptasensor for ultrasensitive detection of tetracycline.

    Science.gov (United States)

    Ramezani, Mohammad; Mohammad Danesh, Noor; Lavaee, Parirokh; Abnous, Khalil; Mohammad Taghdisi, Seyed

    2015-08-15

    Detection methods of antibiotic residues in blood serum and animal derived foods are of great interest. In this study a colorimetric aptasensor was designed for sensitive, selective and fast detection of tetracycline based on triple-helix molecular switch (THMS) and gold nanoparticles (AuNPs). As a biosensor, THMS shows distinct advantages including high stability, sensitivity and preserving the selectivity and affinity of the original aptamer. In the absence of tetracycline, THMS is stable, leading to the aggregation of AuNPs by salt and an obvious color change from red to blue. In the presence of tetracycline, aptamer binds to its target, signal transduction probe (STP) leaves the THMS and adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a red color. The presented aptasensor showed high selectivity toward tetracyclines with a limit of detection as low as 266 pM for tetracycline. The designed aptasensor was successfully applied to detect tetracycline in serum and milk. PMID:25814407

  1. Molecular switch for tuning ions across nanopores by an external electric field

    International Nuclear Information System (INIS)

    Active control of ion transport in nanoscale channels is attracting increasing attention. Recently, experimental and theoretical results have verified that depending on the charged surface of nanopores, the solution inside nanopores can contain either negative or positive ions, which does not happen in macroscale channels. However, the control of the surface chemistry of synthetic nanopores is difficult and the design of nanotubes with novel recognition mechanisms that regulate the ionic selectivity of negative and positive charges remains a challenge. We present here a design for an ion-selective nanopore that is controllable by external charges. Our molecular dynamics simulations show that this remarkable selectivity can be switched from predominantly negative to positive ions and that the magnitude of the ionic flux can be varied by changing the distance of the external charges. The results suggest that the hydration structures around ions play a prominent role in the selectivity process, which is tuned by the external charge. These studies may be useful for developing ways to control the behavior, properties and chemical composition of liquids and provide possible technical applications for nanofluidic field effect transistors. (paper)

  2. Electrospun Nanofibers from a Tricyanofuran-Based Molecular Switch for Colorimetric Recognition of Ammonia Gas.

    Science.gov (United States)

    Khattab, Tawfik A; Abdelmoez, Sherif; Klapötke, Thomas M

    2016-03-14

    A chromophore based on tricyanofuran (TCF) with a hydrazone (H) recognition moiety was developed. Its molecular-switching performance is reversible and has differential sensitivity towards aqueous ammonia at comparable concentrations. Nanofibers were fabricated from the TCF-H chromophore by electrospinning. The film fabricated from these nanofibers functions as a solid-state optical chemosensor for probing ammonia vapor. Recognition of ammonia vapor occurs by proton transfer from the hydrazone fragment of the chromophore to the ammonia nitrogen atom and is facilitated by the strongly electron withdrawing TCF fragment. The TCF-H chromophore was added to a solution of poly(acrylic acid), which was electrospun to obtain a nanofibrous sensor device. The morphology of the nanofibrous sensor was determined by SEM, which showed that nanofibers with a diameter range of 200-450 nm formed a nonwoven mat. The resultant nanofibrous sensor showed very good sensitivity in ammonia-vapor detection. Furthermore, very good reversibility and short response time were also observed. PMID:26864701

  3. Temperature control of molecular circuit switch responsible for virulent phenotype expression in uropathogenic Escherichia coli

    Science.gov (United States)

    Samoilov, Michael

    2010-03-01

    The behavior and fate of biological organisms are to a large extent dictated by their environment, which can be often viewed as a collection of features and constraints governed by physics laws. Since biological systems comprise networks of molecular interactions, one such key physical property is temperature, whose variations directly affect the rates of biochemical reactions involved. For instance, temperature is known to control many gene regulatory circuits responsible for pathogenicity in bacteria. One such example is type 1 fimbriae (T1F) -- the foremost virulence factor in uropathogenic E. coli (UPEC), which accounts for 80-90% of all community-acquired urinary tract infections (UTIs). The expression of T1F is randomly `phase variable', i.e. individual cells switch between virulent/fimbriate and avirulent/afimbriate phenotypes, with rates regulated by temperature. Our computational investigation of this process, which is based on FimB/FimE recombinase-mediated inversion of fimS DNA element, offers new insights into its discrete-stochastic kinetics. In particular, it elucidates the logic of T1F control optimization to the host temperature and contributes further understanding toward the development of novel therapeutic approaches to UPEC-caused UTIs.

  4. Ultrafast quantum spin-state switching in the Co-octaethylporphyrin molecular magnet with a terahertz pulsed magnetic field

    Science.gov (United States)

    Farberovich, Oleg V.; Mazalova, Victoria L.

    2016-05-01

    Molecular spin crossover switches are the objects of intense theoretical and experimental studies in recent years. This interest is due to the fact that these systems allow one to control their spin state by applying an external photo-, thermo-, piezo-, or magnetic stimuli. The greatest amount of research is currently devoted to the study of the effect of the photoexcitation on the bi-stable states of spin crossover single molecular magnets (SMMs). The main limitation of photo-induced bi-stable states is their short lifetime. In this paper we present the results of a study of the spin dynamics of the Co-octaethylporphyrin (CoOEP) molecule in the Low Spin (LS) state and the High Spin (HS) state induced by applying the magnetic pulse of 36.8 T. We show that the spin switching in case of the HS state of the CoOEP molecule is characterized by a long lifetime and is dependent on the magnitude and duration of the applied field. Thus, after applying an external stimuli the system in the LS state after the spin switching reverts to its ground state, whereas the system in the HS state remains in the excited state for a long time. We found that the temperature dependency of magnetic susceptibility shows an abrupt thermal spin transition between two spin states at 40 K. Here the proposed theoretical approach opens the way to create modern devices for spintronics with the controllable spin switching process.

  5. Isomerization of Orthogonal Molecular Switches Encapsulated within Micelles Solubilizing Carbon Nanotubes

    DEFF Research Database (Denmark)

    Kreft, Stefanie K.; Petersen, Michael Åxman; Nielsen, Mogens Brøndsted;

    2015-01-01

    We study the effects of the proximity of the orthogonal dipole-switching moiety dihydroazulene/vinylheptafulvene (DHA/VHF) to carbon nanotubes (CNTs). The switches are introduced into a micelle surrounding the CNTs, thereby achieving very close proximity between the molecules and the CNTs for the...... first time. The change of the molecules' configuration is not hindered by its encapsulation: We report the reversible switching of molecules inside CNT surrounding micelles. The orthogonality of the switch also allows us for the first time to observe the effect of the molecule on the emission spectra of...

  6. Study on Triplex DNA by Use of Molecular "Light Switch" Complex of Ru(phen)2(dppx)2+

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new method for the study of triplex DNA is established according the fluorescence enhancement of molecular "Light Switch" complex of Ru(phen)2(dppx)2+ when it intercalate into triplex DNA. Because the fluorescence intensity of Ru(phen)2(dppx)2+ bonded to triplex DNA is in the case higher than that bonded to duplex DNA in certain range of DNA concentration, the method is much more sensitive than other methods reported previously.

  7. Identification of the molecular switch that regulates access of 5α-DHT to the androgen receptor.

    OpenAIRE

    Penning, Trevor M.; Bauman, David R.; Jin, Yi; Rizner, Tea Lanisik

    2007-01-01

    Pairs of hydroxysteroid dehydrogenases (HSDs) govern ligand access to steroid receptors in target tissues and act as molecular switches. By acting as reductases or oxidases, HSDs convert potent ligands into their cognate inactive metabolites or vice-versa. This pre-receptor regulation of steroid hormone action may have profound effects on hormonal response. We have identified the HSDs responsible for regulating ligand access to the androgen receptor (AR) in human prostate. Type 3 3α-hydroxyst...

  8. A Redox-Controllable Molecular Switch Based on Weak Recognition of BPX26C6 at a Diphenylurea Station

    Directory of Open Access Journals (Sweden)

    Jia-Cheng Chang

    2015-01-01

    Full Text Available The Na+ ion–assisted recognition of urea derivatives by BPX26C6 has allowed the construction of a redox-controllable [2]rotaxane-type molecular switch based on two originally very weakly interacting host/guest systems. Using NOBF4 to oxidize the triarylamine terminus into a corresponding radical cation attracted the macrocyclic component toward its adjacent carbamate station; subsequent addition of Zn powder moved the macrocyclic component back to its urea station.

  9. Preparing and regulating a bi-stable molecular switch by atomic manipulation

    International Nuclear Information System (INIS)

    We present a scanning tunneling microscopy (STM) investigation into the influence of the STM tip on the adsorption site switching of polychlorinatedbiphenyl (PCB) molecules on the Si(111)-7 × 7 surface at room temperature. From an initially stable adsorption configuration, atomic manipulation by charge injection from the STM tip prepared a new bi-stable configuration that switched between two bonding arrangements. No switching rate bias dependence was found for + 1.0 to + 2.2 V. Assuming a thermally driven switching process we find that the measured energy barriers to switching are influenced by the exact location of the STM tip by more than 10%. We propose that this energy difference is due the dispersion interaction between the tip and the molecule.

  10. Aptamer contained triple-helix molecular switch for rapid fluorescent sensing of acetamiprid.

    Science.gov (United States)

    Liu, Xin; Li, Ying; Liang, Jing; Zhu, Wenyue; Xu, Jingyue; Su, Ruifang; Yuan, Lei; Sun, Chunyan

    2016-11-01

    In this study, an aptamer-based fluorescent sensing platform using triple-helix molecular switch (THMS) was developed for the pesticide screening represented by acetamiprid. The THMS was composed of two tailored DNA probes: a label-free central target specific aptamer sequence flanked by two arm segments acting as a recognition probe; a hairpin-shaped structure oligonucleotide serving as a signal transduction probe (STP), labeled with a fluorophore and a quencher at the 3' and 5'-end, respectively. In the absence of acetamiprid, complementary bindings of two arm segments of the aptamers with the loop sequence of STP enforce the formation of THMS with the "open" configuration of STP, and the fluorescence of THMS is on. In the presence of target acetamiprid, the aptamer-target binding results in the formation of a structured aptamer/target complex, which disassembles the THMS and releases the STP. The free STP is folded to a stem loop structure, and the fluorescence is quenched. The quenched fluorescence intensity was proportional to the concentration of acetamiprid in the range from 100 to 1200nM, with the limit of detection (LOD) as low as 9.12nM. In addition, this THMS-based method has been successfully used to test and quantify acetamiprid in Chinese cabbage with satisfactory recoveries, and the results were in full agreement with those from LC-MS. The aptamer-based THMS presents distinct advantages, including high stability, remarkable sensitivity, and preservation of the affinity and specificity of the original aptamer. Most importantly, this strategy is convenient and generalizable by virtue of altering the aptamer sequence without changing the triple-helix structure. So, it is expected that this aptamer-based fluorescent assay could be extensively applied in the field of food safety inspection. PMID:27591592

  11. Molecular phylogeny of beetle associated diplogastrid nematodes suggests host switching rather than nematode-beetle coevolution

    Directory of Open Access Journals (Sweden)

    Sommer Ralf J

    2009-08-01

    diplogastrid nematodes and their beetle hosts. Instead, frequent host switching is observed. The molecular phylogeny of the Diplogastridae provides a framework for further examinations of the evolution of these associations, for the study of interactions within the ecosystems, and for investigations of diplogastrid genome evolution.

  12. Cyclic Zinc(II) Bisporphyrin-Based Molecular Switches: Supramolecular Control of Complexation-Mediated Conformational Switching and Photoinduced Electron Transfer.

    Science.gov (United States)

    Mondal, Pritam; Rath, Sankar Prasad

    2016-04-11

    A cyclic zinc(II) bisporphyrin with flexible linker was employed as a dynamic molecular switch under the regulation of π-acceptors (tetracyanoquinodimethane, trinitrofluorenone, 9-dicyanomethylenefluorene) and bidentate N-donor ligands (1,4-diazabicyclo[2.2.2]octane, pyrazine, 4,4'-bipyridine). The cyclic bisporphyrin host can efficiently encapsulate the π-acceptor guests through the strong π-π interaction, which can be replaced again by using a bidentate N-donor ligand, which coordinates strongly with the metal centers. The open conformation of the bisporphyrin can be efficiently recovered by removing the bidentate ligands using Cu(+) ion. During the process, two porphyrin rings also reversibly change their relative orientation between perpendicular and parallel. The behavior of the cyclic bisporphyrin was followed by using UV/Vis, (1) H NMR, fluorescence, and electrochemical analyses along with X-ray structure determination of the complexes. Moreover, control of photoinduced electron transfer (PET "ON-OFF") is also achieved by the use of guest exchange. Association constants for the host-guest binding were very high, which further explains the robust nature of such assemblies in solution. The experimental evidence is supported by DFT calculations. Such controllable dynamic features can constitute a new step towards "smart" adaptive molecular devices and the emergence of such systems is of significant interest in supramolecular chemistry. PMID:27062017

  13. A theoretical study of magnetoelectronic and switching properties of molecular magnetic tunnel junctions

    Science.gov (United States)

    Soti, V.; Ravan, B. Abedi

    2016-01-01

    Electronic transport and switching properties of molecule-based magnetic tunnel junctions are investigated using the first-principles density functional theory and non-equilibrium Green function methods. As a result of being sandwiched between the ferromagnetic electrodes, a spin-polarization is induced in the nonmagnetic organic atoms. Magnitudes of the spin-polarizations in the trans-polyacetylene, cis-polyacetylene, terphenyl and pentacene chains are calculated and it is suggested that among these the pentacene molecules, because of showing a relatively higher magnetization can theoretically be more appropriate for utilization in spintronic devices. Furthermore, electrical switching capabilities of the junctions are studied and the results reveal that the pentacene junction due to having a larger ON/OFF ratio shows a better switching behavior. Finally, magnetoresistive properties are studied and it is shown that applying torsion can be an effective method to enhance and also adjust magnitudes of the magnetoresistances of the junctions.

  14. Single electron bipolar conductance switch driven by the molecular Aharonov-Bohm effect.

    Science.gov (United States)

    Lee, Joonhee; Tallarida, Nicholas; Rios, Laura; Perdue, Shawn M; Apkarian, Vartkess Ara

    2014-06-24

    We demonstrate a conductance switch controlled by the spin-vibronic density of an odd electron on a single molecule. The junction current is modulated by the spin-flip bistability of the electron. Functional images are provided as wiring diagrams for control of the switch's frequency, amplitude, polarity, and duty-cycle. The principle of operation relies on the quantum mechanical phase associated with the adiabatic circulation of a spin-aligned electron around a conical intersection. The functional images quantify the governing vibronic Hamiltonian. PMID:24824563

  15. Voltage Regulated Uptake and Release of L-Glutamate from a Molecularly Selective Switch for Physiological Applications

    Science.gov (United States)

    Fuchs, Kathrin; Hauff, Elizabeth von; Parisi, Jürgen; Weiler, Reto

    2009-12-01

    In this paper results are presented on the development of a device demonstrating the uptake and release of L-glutamate in solutions with neutral pH. A device which selectively regulates the concentration of biomolecules, such as the primary neural transmitter L-glutamate, could be useful for many biological and medical applications. In the literature it has been demonstrated that polypyrrole (PPy) is a promising material for the recognition basis of molecularly selective devices [1, 2]. In this study we investigated the feasibility of the PPy based "glutamate switch" for the voltage dependent uptake and release of L-glutamate for physiological applications

  16. Memory effect of photoinduced conductivity switching controlled by pulsed voltages in a molecular conductor

    Energy Technology Data Exchange (ETDEWEB)

    Iimori, Toshifumi; Ohta, Nobuhiro [Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020 (Japan); Naito, Toshio, E-mail: nohta@es.hokudai.ac.j [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2009-02-01

    Transient photoresponses of the electrical conductivity in single crystals of an organic conductor alpha-(BEDT-TTF){sub 2}I{sub 3} are studied in the charge-ordered insulating phase. Electrical conductivity switching is observed in the presence of pulsed voltages and synchronous irradiation of nanosecond laser pulse. Current in the photoirradiated crystal as a function of applied voltages shows a bistability in a certain range of voltage. For the initial triggering of the conductivity switching, not only pulsed voltages but also photoirradiation is necessary. A high conductivity state produced by the switching can be repeatedly recovered by applying the pulsed voltages without further photoirradiation even after the current has been reduced to zero. This observation indicates a memory effect of the photoinduced conductivity switching. The appearance of the memory effect depends on the temporal width of the pulsed voltages, which are applied at a rate of approximately 8 Hz. In the measurement using short pulse widths, the memory effect is not observed. This controllability of the memory effect with the pulse width is related to the bistability of the current with respect to the photoirradiation intensity. The shape of the hysteresis loop appearing in the current versus photoirradiation intensity curve can be varied by changing the pulse width.

  17. Electrochemical control of quantum interference in anthraquinone-based molecular switches

    DEFF Research Database (Denmark)

    Markussen, Troels; Schiøtz, Jakob; Thygesen, Kristian Sommer

    2010-01-01

    absent in the hydroquinone molecular bridge. A simple explanation of the interference effect is achieved by transforming the frontier molecular orbitals into localized molecular orbitals thereby obtaining a minimal tight-binding model describing the transport in the relevant energy range in terms of...

  18. Multilayered proteomics reveals molecular switches dictating ligand-dependent EGFR trafficking

    DEFF Research Database (Denmark)

    Francavilla, Chiara; Papetti, Moreno; Rigbolt, Kristoffer T G;

    2016-01-01

    , we devised an integrated multilayered proteomics approach (IMPA). We analyzed dynamic changes in the receptor interactome, ubiquitinome, phosphoproteome, and late proteome in response to both ligands in human cells by quantitative MS and identified 67 proteins regulated at multiple levels. We...... identified RAB7 phosphorylation and RCP recruitment to EGFR as switches for EGF and TGF-α outputs, controlling receptor trafficking, signaling duration, proliferation, and migration. By manipulating RCP levels or phosphorylation of RAB7 in EGFR-positive cancer cells, we were able to switch a TGF......-α-mediated response to an EGF-like response or vice versa as EGFR trafficking was rerouted. We propose IMPA as an approach to uncover fine-tuned regulatory mechanisms in cell signaling....

  19. Extrapolative Analysis of Fast-Switching Free Energy Estimates in a Molecular System

    OpenAIRE

    Zuckerman, Daniel M.; Woolf, Thomas B.

    2001-01-01

    We perform an extrapolative analysis of "fast-growth" free-energy-difference (DF) estimates of a computer-modeled, fully-solvated ethanemethanol transformation. The results suggest that extrapolation can greatly reduce the systematic error in DF estimated from a small number of very fast switches. Our extrapolation procedure uses block-averages of finite-data estimates, and appears to be particularly useful for broad, non-Gaussian distributions of data which produce substantial systematic err...

  20. First principle calculations of molecular polarization switching in P(VDF-TrFE) ferroelectric thin Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    This paper reports first principle calculations and analysis of the molecular mechanism of the polarization switching in polyvinylidene fluoride and its copolymer with trifluoroethylene (P(VDF-TrFE)) using semi-empirical and ab initio quantum chemical methods based on the HyperChem 7.5 and Gaussian98 programs. The simulations were performed for different copolymer contents in P(VDF-TrFE)-(70:30), (60:40) and pure PVDF. The calculated values of the dipole moment and average polarization of the molecular chains show a clear hysteresis under varying electric field with polarization saturated at ∼0.1-0.14 C m-2. The calculated coercive fields (corresponding to the rotation of molecular chains to opposite orientation) are consistent (within an order of magnitude) with experimental data obtained for thin films (Ec = 5-18 MV cm-1). In the absence of external electric fields, the interactions between several molecular chains lead to the orientation of all dipole moments along one direction parallel to the chain plane. This model corresponds to the PVDF layer on the dielectric surface. For the electric field in the perpendicular direction, all chains are rotated along this direction corresponding to the model of conductive substrate

  1. Molecular phylogeny of the bivalve superfamily Galeommatoidea (Heterodonta, Veneroida reveals dynamic evolution of symbiotic lifestyle and interphylum host switching

    Directory of Open Access Journals (Sweden)

    Goto Ryutaro

    2012-09-01

    Full Text Available Abstract Background Galeommatoidea is a superfamily of bivalves that exhibits remarkably diverse lifestyles. Many members of this group live attached to the body surface or inside the burrows of other marine invertebrates, including crustaceans, holothurians, echinoids, cnidarians, sipunculans and echiurans. These symbiotic species exhibit high host specificity, commensal interactions with hosts, and extreme morphological and behavioral adaptations to symbiotic life. Host specialization to various animal groups has likely played an important role in the evolution and diversification of this bivalve group. However, the evolutionary pathway that led to their ecological diversity is not well understood, in part because of their reduced and/or highly modified morphologies that have confounded traditional taxonomy. This study elucidates the taxonomy of the Galeommatoidea and their evolutionary history of symbiotic lifestyle based on a molecular phylogenic analysis of 33 galeommatoidean and five putative galeommatoidean species belonging to 27 genera and three families using two nuclear ribosomal genes (18S and 28S ribosomal DNA and a nuclear (histone H3 and mitochondrial (cytochrome oxidase subunit I protein-coding genes. Results Molecular phylogeny recovered six well-supported major clades within Galeommatoidea. Symbiotic species were found in all major clades, whereas free-living species were grouped into two major clades. Species symbiotic with crustaceans, holothurians, sipunculans, and echiurans were each found in multiple major clades, suggesting that host specialization to these animal groups occurred repeatedly in Galeommatoidea. Conclusions Our results suggest that the evolutionary history of host association in Galeommatoidea has been remarkably dynamic, involving frequent host switches between different animal phyla. Such an unusual pattern of dynamic host switching is considered to have resulted from their commensalistic lifestyle, in

  2. Mucosal transmissibility, disease induction and coreceptor switching of R5 SHIVSF162P3N molecular clones in rhesus macaques

    Directory of Open Access Journals (Sweden)

    Ren Wuze

    2013-01-01

    Full Text Available Abstract Background Mucosally transmissible and pathogenic CCR5 (R5-tropic simian-human immunodeficiency virus (SHIV molecular clones are useful reagents to identity neutralization escape in HIV-1 vaccine experiments and to study the envelope evolutionary process and mechanistic basis for coreceptor switch during the course of natural infection. Results We observed progression to AIDS in rhesus macaques infected intrarectally with molecular clones of the pathogenic R5 SHIVSF162P3N isolate. Expansion to CXCR4 usage was documented in one diseased macaque that mounted a neutralizing antibody response and in another that failed to do so, with the latter displaying a rapid progressor phenotype. V3 loop envelop glycoprotein gp120 sequence changes that are predictive of a CXCR4 (X4-using phenotype in HIV-1 subtype B primary isolates, specifically basic amino acid substations at positions 11 (S11R, 24 (G24R and 25 (D25K of the loop were detected in the two infected macaques. Functional assays showed that envelopes with V3 S11R or D25K mutation were dual-tropic, infecting CD4+ target cells that expressed either the CCR5 or CXCR4 coreceptor. And, consistent with findings of coreceptor switching in macaques infected with the pathogenic isolate, CXCR4-using variant was first detected in the lymph node of the chronically infected rhesus monkey several weeks prior to its presence in peripheral blood. Moreover, X4 emergence in this macaque coincided with persistent peripheral CD4+ T cell loss and a decline in neutralizing antibody titer that are suggestive of immune deterioration, with macrophages as the major virus-producing cells at the end-stage of disease. Conclusions The data showed that molecular clones derived from the R5 SHIVSF162P3N isolate are mucosally transmissible and induced disease in a manner similar to that observed in HIV-1 infected individuals, providing a relevant and useful animal infection model for in-depth analyses of host selection

  3. Voltage-Induced Switching Dynamics of a Coupled Spin Pair in a Molecular Junction.

    Science.gov (United States)

    Saygun, T; Bylin, J; Hammar, H; Fransson, J

    2016-04-13

    Molecular spintronics is made possible by the coupling between electronic configuration and magnetic polarization of the molecules. For control and application of the individual molecular states, it is necessary to both read and write their spin states. Conventionally, this is achieved by means of external magnetic fields or ferromagnetic contacts, which may change the intentional spin state and may present additional challenges when downsizing devices. Here, we predict that coupling magnetic molecules together opens up possibilities for all electrical control of both the molecular spin states as well as the current flow through the system. By tuning between the regimes of ferromagnetic and antiferromagnetic exchange interaction, the current can be at least an order of magnitude enhanced or reduced. The effect is susceptible to the tunnel coupling and molecular level alignment that can be used to achieve current rectification. PMID:27010805

  4. Molecular current switch: principles and photoelectronic characterization of the model system

    Czech Academy of Sciences Publication Activity Database

    Vala, M.; Weiter, M.; Nešpůrek, Stanislav

    2005-01-01

    Roč. 15, č. 3 (2005), s. 28. ISSN 1210-7409 Institutional research plan: CEZ:AV0Z40500505 Keywords : molecular electronics * photochromism * charge transport Subject RIV: CD - Macromolecular Chemistry

  5. Deep molecular responses achieved in patients with CML-CP who are switched to nilotinib after long-term imatinib.

    Science.gov (United States)

    Hughes, Timothy P; Lipton, Jeffrey H; Spector, Nelson; Cervantes, Francisco; Pasquini, Ricardo; Clementino, Nelma Cristina D; Dorlhiac Llacer, Pedro Enrique; Schwarer, Anthony P; Mahon, Francois-Xavier; Rea, Delphine; Branford, Susan; Purkayastha, Das; Collins, LaTonya; Szczudlo, Tomasz; Leber, Brian

    2014-07-31

    Patients in complete cytogenetic response (CCyR) with detectable BCR-ABL1 after ≥2 years on imatinib were randomized to nilotinib (400 mg twice daily, n = 104) or continued imatinib (n = 103) in the Evaluating Nilotinib Efficacy and Safety in clinical Trials-Complete Molecular Response (ENESTcmr) trial. By 1 and 2 years, confirmed undetectable BCR-ABL1 was achieved by 12.5% vs 5.8% (P = .108) and 22.1% vs 8.7% of patients in the nilotinib and imatinib arms, respectively (P = .0087). Among patients without molecular response 4.5 (BCR-ABL1(IS) ≤0.0032%; MR(4.5)) and those without major molecular response at study start, MR(4.5) by 2 years was achieved by 42.9% vs 20.8% and 29.2% vs 3.6% of patients in the nilotinib and imatinib arms, respectively. No patient in the nilotinib arm lost CCyR, vs 3 in the imatinib arm. Adverse events were more common in the nilotinib arm, as expected with the introduction of a new drug vs remaining on a well-tolerated drug. The safety profile of nilotinib was consistent with other reported studies. In summary, switching to nilotinib enabled more patients with chronic myeloid leukemia in chronic phase (CML-CP) to sustain lower levels of disease burden vs remaining on imatinib. This trial was registered at www.clinicaltrials.gov as #NCT00760877. PMID:24948656

  6. Voltage induced switching dynamics of a coupled spin pair in a molecular junction

    OpenAIRE

    Saygun, T.; Bylin, J.; Hammar, H.; J. Fransson

    2016-01-01

    Molecular spintronics is made possible by the coupling between electronic configuration and magnetic po- larization of the molecules. For control and application of the individual molecular states it is necessary to both read and write their spin states. Conventionally, this is achieved by means of external magnetic fields or ferromagnetic contacts, which may change the intentional spin state and may present additional challenges when downsizing devices. Here, we predict that coupling magneti...

  7. A solid-state electrochemiluminescence biosensing switch for detection of DNA hybridization based on ferrocene-labeled molecular beacon

    International Nuclear Information System (INIS)

    A solid-state electrochemiluminescence (ECL) biosensing switch incorporating quenching of ECL of ruthenium(II) tris-(bipyridine) (Ru(bpy)32+) by ferrocene (Fc) has been successfully developed for DNA hybridization detection. The important issue for this biosensing system is based on the ferrocene-labeled molecular beacon (Fc-MB), i.e. using the special Fc-MB to react with the target DNA and then change its structure, resulting in an ECL intensity change. Under the optimal conditions, the difference of ECL intensity before and after the hybridization reaction (ΔIECL) was linearly related to the concentration of the complementary sequence in the range of 10 fM-10 pM and the detection limit was down to 1.0 fM.

  8. Current-induced forces: a new mechanism to induce negative differential resistance and current-switching effect in molecular junctions

    Science.gov (United States)

    Gu, Lei; Fu, Hua-Hua

    2015-12-01

    Current-induced forces can excite molecules, polymers and other low-dimensional materials, which in turn leads to an effective gate voltage through Holstein interaction. Here, by taking a short asymmetric DNA junction as an example, and using the Langevin approach, we find that when suppression of charge transport by the effective gate voltage surpasses the current increase from an elevated voltage bias, the current-voltage (I-V) curves display strong negative differential resistance (NDR) and perfect current-switching characteristics. The asymmetric DNA chain differs in mechanical stability under inverse voltages and the I-V curve is asymmetric about inverse biases, which can be used to understand recent transport experiments on DNA chains, and meanwhile provides a new strategy to realize NDR in molecular junctions and other low-dimensional quantum systems.

  9. Fast transient current response to switching events in short chains of molecular islands

    Czech Academy of Sciences Publication Activity Database

    Kalvová, Anděla; Špička, Václav; Velický, B.

    2013-01-01

    Roč. 26, č. 4 (2013), s. 773-777. ISSN 1557-1939 R&D Projects: GA ČR GAP204/12/0897 Institutional support: RVO:68378271 Keywords : nonequilibrium * molecular islands * initial correlations * transient currents Subject RIV: BE - Theoretical Physics Impact factor: 0.930, year: 2013

  10. Molecular weight distribution broadening of polypropylene by periodic switching of hydrogen and catalyst additions

    OpenAIRE

    Ali, M. Al-Haj; Stroomer, J.; Betlem, B.; Weickert, G.; Roffel, B.

    2008-01-01

    This study presents a feasibility study of the broadening of the polypropylene molecular weight distribution produced using a multisite Ziegler-Natta catalyst in a continuous liquid-pool polymerization reactor. The broadening is achieved by operating the reactor under periodic forcing of both hydrogen and catalyst feed flows. Model-based dynamic optimization is used to determine the cycle period and peak width for these inputs. Through simulation it is shown that limited widening (similar to ...

  11. Electron induced conformational changes of an imine-based molecular switch on a Au(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Lotze, Christian; Henningsen, Nils; Franke, Katharina; Schulze, Gunnar; Pascual, Jose Ignacio [Inst. f. Experimentalphysik, Freie Universitaet Berlin (Germany); Luo, Ying; Haag, Rainer [Inst. f. Organische Chemie, Freie Universitaet Berlin (Germany)

    2009-07-01

    Azobenzene-based molecules exhibit a cis-trans configurational photoisomerisation in solution. Recently, the adsorption properties of azobenzene derivatives have been investigated on different metal surfaces in order to explore the possible changes in the film properties induced by external stimuli. In azobenzene, the diazo-bridge is a key group for the isomerization process. Its interaction with a metal surface is dominated through the N lone-pair electrons, which reduces the efficiency of the conformational change. In order to reduce the molecule-surface interaction, we explore an alternative molecular architecture by substituting the diazo-bridge (-N=N-) of azobenzene by an imine-group (-N=CH-). We have investigated the imine-based compound para-carboxyl-di-benzene-imine (PCI) adsorbed on a Au(111) surface. The carboxylic terminations mediates the formation of strongly bonded molecular dimers, which align in ordered rows preferentially following the fcc regions of the Au(111) herringbone reconstruction. Low temperature scanning tunneling microscopy was used to induce conformational changes between trans and cis state of individual molecules in a molecular monolayer.

  12. Interplay of Oct4 with Sox2 and Sox17: a molecular switch from stem cell pluripotency to specifying a cardiac fate.

    OpenAIRE

    Stefanovic, Sonia; Abboud, Nesrine; Désilets, Stéphanie; Nu, David; Cowan, Chad; Pucéat, Michel

    2009-01-01

    Oct4 exerts a dose-dependent dual action, as both a gatekeeper for stem cell pluripotency and in driving cells toward specific lineages. Here, we identify the molecular mechanism underlying this dual function. BMP2- or transgene-induced Oct4 up-regulation drives human embryonic and induced pluripotent stem cells to become cardiac progenitors. When embryonic stem cell pluripotency is achieved, Oct4 switches from the Sox2 to the Sox17 promoter. This switch allows the cells to turn off the pluri...

  13. The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs.

    Science.gov (United States)

    Sandoval, Angelica; Eichler, Stefanie; Madathil, Sineej; Reeves, Philip J; Fahmy, Karim; Böckmann, Rainer A

    2016-07-12

    The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the bovine photoreceptor rhodopsin, this is accompanied by proton uptake at Glu(134) in the class-conserved D(E)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed in this study by molecular dynamics (MD) simulations on TM3 model peptides in a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We show that protonation of the conserved glutamic acid alters the peptide insertion depth in the membrane, its side-chain rotamer preferences, and stabilizes the C-terminal helical structure. These factors contribute to the rise of the side-chain pKa (> 6) and to reduced polarity around the TM3 C terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved Fourier transform infrared (FTIR) spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu(134)- and Gln(134)-containing bovine opsin mutants and demonstrates that the D(E)RY motif is a hydrated microdomain. The function of the D(E)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface. PMID:27410736

  14. A Molecular Switch Abrogates Glycoprotein 100 (gp100) T-cell Receptor (TCR) Targeting of a Human Melanoma Antigen*

    Science.gov (United States)

    Bianchi, Valentina; Bulek, Anna; Fuller, Anna; Lloyd, Angharad; Attaf, Meriem; Rizkallah, Pierre J.; Dolton, Garry; Sewell, Andrew K.; Cole, David K.

    2016-01-01

    Human CD8+ cytotoxic T lymphocytes can mediate tumor regression in melanoma through the specific recognition of HLA-restricted peptides. Because of the relatively weak affinity of most anti-cancer T-cell receptors (TCRs), there is growing emphasis on immunizing melanoma patients with altered peptide ligands in order to induce strong anti-tumor immunity capable of breaking tolerance toward these self-antigens. However, previous studies have shown that these immunogenic designer peptides are not always effective. The melanocyte differentiation protein, glycoprotein 100 (gp100), encodes a naturally processed epitope that is an attractive target for melanoma immunotherapies, in particular peptide-based vaccines. Previous studies have shown that substitutions at peptide residue Glu3 have a broad negative impact on polyclonal T-cell responses. Here, we describe the first atomic structure of a natural cognate TCR in complex with this gp100 epitope and highlight the relatively high affinity of the interaction. Alanine scan mutagenesis performed across the gp100280–288 peptide showed that Glu3 was critically important for TCR binding. Unexpectedly, structural analysis demonstrated that the Glu3 → Ala substitution resulted in a molecular switch that was transmitted to adjacent residues, abrogating TCR binding and T-cell recognition. These findings help to clarify the mechanism of T-cell recognition of gp100 during melanoma responses and could direct the development of altered peptides for vaccination. PMID:26917722

  15. A metal-ion-responsive adhesive material via switching of molecular recognition properties

    Science.gov (United States)

    Nakamura, Takashi; Takashima, Yoshinori; Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira

    2014-08-01

    Common adhesives stick to a wide range of materials immediately after they are applied to the surfaces. To prevent indiscriminate sticking, smart adhesive materials that adhere to a specific target surface only under particular conditions are desired. Here we report a polymer hydrogel modified with both β-cyclodextrin (βCD) and 2,2‧-bipyridyl (bpy) moieties (βCD-bpy gel) as a functional adhesive material responding to metal ions as chemical stimuli. The adhesive property of βCD-bpy gel based on interfacial molecular recognition is expressed by complexation of metal ions to bpy that controlled dissociation of supramolecular cross-linking of βCD-bpy. Moreover, adhesion of βCD-bpy gel exhibits selectivity on the kinds of metal ions, depending on the efficiency of metal-bpy complexes in cross-linking. Transduction of two independent chemical signals (metal ions and host-guest interactions) is achieved in this adhesion system, which leads to the development of highly orthogonal macroscopic joining of multiple objects.

  16. A molecular switch driving inactivation in the cardiac K+ channel HERG.

    Directory of Open Access Journals (Sweden)

    David A Köpfer

    Full Text Available K(+ channels control transmembrane action potentials by gating open or closed in response to external stimuli. Inactivation gating, involving a conformational change at the K(+ selectivity filter, has recently been recognized as a major K(+ channel regulatory mechanism. In the K(+ channel hERG, inactivation controls the length of the human cardiac action potential. Mutations impairing hERG inactivation cause life-threatening cardiac arrhythmia, which also occur as undesired side effects of drugs. In this paper, we report atomistic molecular dynamics simulations, complemented by mutational and electrophysiological studies, which suggest that the selectivity filter adopts a collapsed conformation in the inactivated state of hERG. The selectivity filter is gated by an intricate hydrogen bond network around residues S620 and N629. Mutations of this hydrogen bond network are shown to cause inactivation deficiency in electrophysiological measurements. In addition, drug-related conformational changes around the central cavity and pore helix provide a functional mechanism for newly discovered hERG activators.

  17. Towards single molecule switches.

    Science.gov (United States)

    Zhang, Jia Lin; Zhong, Jian Qiang; Lin, Jia Dan; Hu, Wen Ping; Wu, Kai; Xu, Guo Qin; Wee, Andrew T S; Chen, Wei

    2015-05-21

    The concept of using single molecules as key building blocks for logic gates, diodes and transistors to perform basic functions of digital electronic devices at the molecular scale has been explored over the past decades. However, in addition to mimicking the basic functions of current silicon devices, molecules often possess unique properties that have no parallel in conventional materials and promise new hybrid devices with novel functions that cannot be achieved with equivalent solid-state devices. The most appealing example is the molecular switch. Over the past decade, molecular switches on surfaces have been intensely investigated. A variety of external stimuli such as light, electric field, temperature, tunneling electrons and even chemical stimulus have been used to activate these molecular switches between bistable or even multiple states by manipulating molecular conformations, dipole orientations, spin states, charge states and even chemical bond formation. The switching event can occur either on surfaces or in break junctions. The aim of this review is to highlight recent advances in molecular switches triggered by various external stimuli, as investigated by low-temperature scanning tunneling microscopy (LT-STM) and the break junction technique. We begin by presenting the molecular switches triggered by various external stimuli that do not provide single molecule selectivity, referred to as non-selective switching. Special focus is then given to selective single molecule switching realized using the LT-STM tip on surfaces. Single molecule switches operated by different mechanisms are reviewed and discussed. Finally, molecular switches embedded in self-assembled monolayers (SAMs) and single molecule junctions are addressed. PMID:25757483

  18. How Ligands Throw the Molecular Switch in an Ion Channel: What >Patch-Clamping can Reveal.

    Science.gov (United States)

    Tibbs, Gareth R.

    1998-03-01

    Ion channels are integral membrane proteins with two distinctive characteristics: they are gated (opened and closed) by specific signals such as membrane voltage or the direct binding of chemical ligands and, once open, they conduct ions across the cell membrane at very high rates (>10^7 s-1). Although analysis of the atomic structure of membrane proteins presents a daunting challenge, the relatively large currents carried by ion channels enable their active (open) state(s) to be readily distinguished from their inactive (closed) state(s). Coupled with the use of molecular biological techniques, this permits us to 1. Obtain details of kinetically distinguishable states of the channel, 2. Identify and characterize the functional roles of specific domains of the protein, and 3. Explore the thermodynamic contribution of domains or individual bonds to activation. I shall present data that explores such structure-function relationships within the cyclic nucleotide-gated (CNG) channel branch of the voltage-gated (VG) channel superfamily. Like the closely related VG K+ channels, the CNG channels are tetramers with each subunit having six putative transmembrane helices and cytoplasmic N and C termini. By measuring the amplitude of the current flowing through single chimeric channels we have demonstrated that the loop between the fifth and sixth helices is the major determinant of the ion-conducting pore. Guided by homology to cyclic nucleotide-binding (CNB) proteins whose crystal structure is known, it has been established that an 120 amino acid sequence within the C-terminus of each subunit forms a CNB site. By making selective mutations within this pocket and measuring the affinity and ability of bound agonist to activate the channel, it has been possible to establish whether the free energy of specific channel-agonist bonds contributes to activation of the protein or stabilization of ligand in the binding pocket. Finally, we have measured the ability of the channel to

  19. Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: A molecule-to-lattice energy transfer

    Directory of Open Access Journals (Sweden)

    A. Marino

    2016-03-01

    Full Text Available We combine ultrafast optical spectroscopy with femtosecond X-ray absorption to study the photo-switching dynamics of the [Fe(PM-AzA2(NCS2] spin-crossover molecular solid. The light-induced excited spin-state trapping process switches the molecules from low spin to high spin (HS states on the sub-picosecond timescale. The change of the electronic state (<50 fs induces a structural reorganization of the molecule within 160 fs. This transformation is accompanied by coherent molecular vibrations in the HS potential and especially a rapidly damped Fe-ligand breathing mode. The time-resolved studies evidence a delayed activation of coherent optical phonons of the lattice surrounding the photoexcited molecules.

  20. Synthesis, molecular structure, spectroscopic investigations and computational study of a potential molecular switch of 2-([1,1'-biphenyl]-4-yl)-2-methyl-6-(4-nitrophenyl)-4-phenyl-1,3 diazabicyclo [3.1.0]hex-3-ene

    Indian Academy of Sciences (India)

    AYOUB KANAANI; DAVOOD AJLOO; HAMZEH I KIYAN; FRESHTE SHAHERI; MAJID AMIRI

    2016-08-01

    This work presents a combined experimental and theoretical study on a photochromic compound, 2-([1,1'-biphenyl]-4-yl)-2-methyl-6-(4-nitrophenyl)-4-phenyl-1,3 diazabicyclo [3.1.0]hex-3-ene, existing in closed form (‘A’) and open form (‘B’). The spectroscopic properties of the title compound have beeninvestigated by using IR, UV–Vis and ¹H NMR techniques. The molecular geometry and spectroscopic data of the title compound have been calculated by using the density functional method (B3LYP) invoking 6-311G(d,p) basis set. UV-Vis spectra of the two forms were recorded. The excitation energies, oscillator strength, etc., were calculated by time-dependent density functional theory (TD-DFT). Furthermore, molecular electrostatic potential map (MEP), frontier molecular orbital analysis (HOMO–LUMO), total density of state (TDOS) and reactivity descriptors were found and discussed. We applied a first-principles computational approach to study a light-sensitive molecular switch. We find that the conductance of the two isomers varies dramatically, which suggests that this system has potential use as a molecular switch.

  1. New structure of three-terminal GaAs p(+)-n(-)-delta(p+)-n(-)-n(+) switching device prepared by molecular beam epitaxy

    Science.gov (United States)

    Wang, Y. H.; Yarn, K. F.; Chang, C. Y.; Jame, M. S.

    1987-08-01

    A new three-terminal GaAs p(+)-n(-)-delta(p+)-n(-)-n(+), voltage-controlled switching device grown by molecular beam epitaxy is presented. A simple method to contact the third terminal is employed by applying the Au-Zn to the delta(p+) barrier using the B-groove etching technique, in which the delta(p+) barrier height can be directly modulated by the external voltage. The device may be more effective than other voltage-controlled devices due to the direct barrier modulation.

  2. Electronic transport properties of indolyl spirooxazine/merooxazine-based light-driven molecular switch: The effect of amino/nitro substituents

    Science.gov (United States)

    Zhao, H.; Xu, Y. Q.; Zhao, W. K.; Gao, K.; Liu, D. S.

    2014-03-01

    By applying non-equilibrium Green's function formulation combined with first-principles density functional theory, we explore the electronic transport properties of indolinospironaphthoxazine (SO)/indolinomeronaphthoxazine (MO). The results indicate that the MO allows a far larger current than the SO. The substituent group can cause shifts of the energy levels. Higher ON/OFF current ratio can be obtained if either amino or nitro substituent is placed at the position of naphthalene moiety. Our results suggest that such molecular wires can generally display switching function and the efficiency can be increased by adding certain substituent groups to the molecules.

  3. Realization of a four-step molecular switch in scanning tunneling microscope manipulation of single chlorophyll-a molecules

    OpenAIRE

    Iancu, Violeta; Hla, Saw-Wai

    2006-01-01

    Single chlorophyll-a molecules, a vital resource for the sustenance of life on Earth, have been investigated by using scanning tunneling microscope manipulation and spectroscopy on a gold substrate at 4.6 K. Chlorophyll-a binds on Au(111) via its porphyrin unit while the phytyl-chain is elevated from the surface by the support of four CH3 groups. By injecting tunneling electrons from the scanning tunneling microscope tip, we are able to bend the phytyl-chain, which enables the switching of fo...

  4. Photoelectron spectroscopy of self-assembled monolayers of molecular switches on noble metal surfaces; Photoelektronenspektroskopie selbstorganisierter Adsorbatschichten aus molekularen Schaltern auf Edelmetalloberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Nils

    2012-09-12

    Self-assembled monolayers (SAMs) of butanethiolate (C4) on single crystalline Au(111) surfaces were prepared by adsorption from solution. The thermally activated desorption behaviour of the C4 molecules from the gold substrate was examined by qualitative thermal desorption measurements (TDM), through this a desorption temperature T{sub Des}=473 K could be determined. With this knowledge, it was possible to produce samples of very good surface quality, by thermal treatment T{sub Sample}molecular switch 3-(4-(4-Hexyl-phenylazo)-phenoxy)-propane-1-thiol (ABT), deposited by self-assembly from solution on Au(111), was examined using laser-based photoelectron spectroscopy. Differences in the molecular dipole moment characteristic for the trans and the cis isomer of ABT were observed via changes in the sample work function, accessible by detection of the threshold energy for photoemission. A quantitative

  5. New concepts in molecular imaging: non-invasive MRI spotting of proteolysis using an Overhauser effect switch.

    Directory of Open Access Journals (Sweden)

    Philippe Mellet

    Full Text Available BACKGROUND: Proteolysis, involved in many processes in living organisms, is tightly regulated in space and time under physiological conditions. However deregulation can occur with local persistent proteolytic activities, e.g. in inflammation, cystic fibrosis, tumors, or pancreatitis. Furthermore, little is known about the role of many proteases, hence there is a need of new imaging methods to visualize specifically normal or disease-related proteolysis in intact bodies. METHODOLOGY/PRINCIPAL FINDINGS: In this paper, a new concept for non invasive proteolysis imaging is proposed. Overhauser-enhanced Magnetic Resonance Imaging (OMRI at 0.2 Tesla was used to monitor the enzymatic hydrolysis of a nitroxide-labeled protein. In vitro, image intensity switched from 1 to 25 upon proteolysis due to the associated decrease in the motional correlation time of the substrate. The OMRI experimental device used in this study is consistent with protease imaging in mice at 0.2 T without significant heating. Simulations show that this enzymatic-driven OMRI signal switch can be obtained at lower frequencies suitable for larger animals or humans. CONCLUSIONS/SIGNIFICANCE: The method is highly sensitive and makes possible proteolysis imaging in three dimensions with a good spatial resolution. Any protease could be targeted specifically through the use of taylor-made cleavable macromolecules. At short term OMRI of proteolysis may be applied to basic research as well as to evaluate therapeutic treatments in small animal models of experimental diseases.

  6. Sensitive and selective detection of uracil-DNA glycosylase activity with a new pyridinium luminescent switch-on molecular probe.

    Science.gov (United States)

    Lu, Yu-Jing; Hu, Dong-Ping; Deng, Qiang; Wang, Zheng-Ya; Huang, Bao-Hua; Fang, Yan-Xiong; Zhang, Kun; Wong, Wing-Leung

    2015-09-01

    Uracil-deoxyribonucleic acid glycosylase (UDG) is known to function as an important base-excision repair enzyme and eliminate uracil from DNA molecules to maintain genomic integrity. A new small organic molecule (DID-VP) with interesting structural properties was synthesized as a G-quadruplex selective ligand and was demonstrated to be a sensitive luminescent switch-on probe in a convenient luminescent assay specifically for UDG detection in fetal bovine serum samples under rapid and simple conditions. This newly developed analytical method is based on the UDG enzymatic activity to unwind a duplex DNA substrate, and comprises a G-quadruplex-forming sequence (ON1) and uracil-containing DNA strand (ON2) to generate a remarkable fluorescence signal through the specific interaction of DID-VP with ON1. This luminescent switch-on assay is able to achieve high sensitivity and specificity for UDG over other enzymes. The application range of the present analytical system is found to be 0.05 to 1.00 U mL(-1) UDG with a very low detection limit of 0.005 U mL(-1). The recovery study of UDG in real samples gave a very good performance with 75.05%-102.7% recovery. In addition, an extended application of the assay in screening of UDG inhibitors is demonstrated. A good dose-dependence of the luminescence response with respect to the concentration of UDG inhibitors in samples was observed. PMID:26185800

  7. Femtosecond Laser Spectroscopy of the Rhodopsin Photochromic Reaction: A Concept for Ultrafast Optical Molecular Switch Creation (Ultrafast Reversible Photoreaction of Rhodopsin

    Directory of Open Access Journals (Sweden)

    Olga Smitienko

    2014-11-01

    Full Text Available Ultrafast reverse photoreaction of visual pigment rhodopsin in the femtosecond time range at room temperature is demonstrated. Femtosecond two-pump probe experiments with a time resolution of 25 fs have been performed. The first рump pulse at 500 nm initiated cis-trans photoisomerization of rhodopsin chromophore, 11-cis retinal, which resulted in the formation of the primary ground-state photoproduct within a mere 200 fs. The second pump pulse at 620 nm with a varying delay of 200 to 3750 fs relative to the first рump pulse, initiated the reverse phototransition of the primary photoproduct to rhodopsin. The results of this photoconversion have been observed on the differential spectra obtained after the action of two pump pulses at a time delay of 100 ps. It was found that optical density decreased at 560 nm in the spectral region of bathorhodopsin absorption and increased at 480 nm, where rhodopsin absorbs. Rhodopsin photoswitching efficiency shows oscillations as a function of the time delay between two рump pulses. The quantum yield of reverse photoreaction initiated by the second pump pulse falls within the range 15% ± 1%. The molecular mechanism of the ultrafast reversible photoreaction of visual pigment rhodopsin may be used as a concept for the development of an ultrafast optical molecular switch.

  8. Photoinduced switching to metallic states in the two-dimensional organic Mott insulator dimethylphenazine-tetrafluorotetracyanoquinodimethane with anisotropic molecular stacks

    Science.gov (United States)

    Matsuzaki, Hiroyuki; Ohkura, Masa-aki; Ishige, Yu; Nogami, Yoshio; Okamoto, Hiroshi

    2015-06-01

    A photoinduced phase transition was investigated in an organic charge-transfer (CT) complex M2P -TCNQ F4 , [M2P : 5,10-dihydro-5,10-dimethylphenazine, donor (D) molecule; TCNQ F4 : 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, acceptor (A) molecule] by means of femtosecond pump-probe reflection spectroscopy. This is an ionic compound and has a peculiar two-dimensional (2D) molecular arrangement; the same A (or D) molecules arrange along the [100] direction, and A and D molecules alternately arrange along the [111] direction. It results in a strongly anisotropic two-dimensional electronic structure. This compound shows a structural and magnetic phase transition at 122 K below which the two neighboring molecules are dimerized along both the [100] and [111] directions. We demonstrate that two kinds of photoinduced phase transitions occur by irradiation of a femtosecond laser pulse; in the high-temperature lattice-uniform phase, a quasi-one-dimensional (1D) metallic state along the AA(DD) stack is generated, and in the low-temperature lattice-dimerized phase, a quasi-2D metallic state is initially produced and molecular dimerizations are subsequently released. Mixed-stack CT compounds consisting of DA stacks are generally insulators or semiconductors in the ground state. Here, such a dynamical metallization in the DA stack is demonstrated. The release of the dimerizations drives several kinds of coherent oscillations which play an important role in the stabilization of the lattice-dimerized phase. The mechanisms of those photoinduced phase transitions are discussed in terms of the magnitudes of the anisotropic bandwidths and molecular dimerizations along two different directions of the molecular stacks.

  9. Molecular Structures and Dynamics of the Stepwise Activation Mechanism of a Matrix Metalloproteinase Zymogen: Challenging the Cysteine Switch Dogma

    International Nuclear Information System (INIS)

    Activation of matrix metalloproteinase zymogen (pro-MMP) is a vital homeostatic process, yet its molecular basis remains unresolved. Using stopped-flow X-ray spectroscopy of the active site zinc ion, we determined the temporal sequence of pro-MMP-9 activation catalyzed by tissue kallikrein protease in milliseconds to several minutes. The identity of three intermediates seen by X-ray spectroscopy was corroborated by molecular dynamics simulations and quantum mechanics/molecular mechanics calculations. The cysteine-zinc interaction that maintains enzyme latency is disrupted via active-site proton transfers that mediate transient metal-protein coordination events and eventual binding of water. Unexpectedly, these events ensue as a direct result of complexation of pro-MMP-9 and kallikrein and occur before proteolysis and eventual dissociation of the pro-peptide from the catalytic site. Here we demonstrate the synergism among long-range protein conformational transitions, local structural rearrangements, and fine atomic events in the process of zymogen activation.

  10. Molecular Structures and Dynamics of the Stepwise Activation Mechanism of a Matrix Metalloproteinase Zymogen: Challenging the Cysteine Switch Dogma

    Energy Technology Data Exchange (ETDEWEB)

    Rosenblum,G.; Meroueh, S.; Toth, M.; Fisher, J.; Fridman, R.; Mobashery, S.; Sagi, I.

    2007-01-01

    Activation of matrix metalloproteinase zymogen (pro-MMP) is a vital homeostatic process, yet its molecular basis remains unresolved. Using stopped-flow X-ray spectroscopy of the active site zinc ion, we determined the temporal sequence of pro-MMP-9 activation catalyzed by tissue kallikrein protease in milliseconds to several minutes. The identity of three intermediates seen by X-ray spectroscopy was corroborated by molecular dynamics simulations and quantum mechanics/molecular mechanics calculations. The cysteine-zinc interaction that maintains enzyme latency is disrupted via active-site proton transfers that mediate transient metal-protein coordination events and eventual binding of water. Unexpectedly, these events ensue as a direct result of complexation of pro-MMP-9 and kallikrein and occur before proteolysis and eventual dissociation of the pro-peptide from the catalytic site. Here we demonstrate the synergism among long-range protein conformational transitions, local structural rearrangements, and fine atomic events in the process of zymogen activation.

  11. Role of accelerated segment switch in exons to alter targeting (ASSET in the molecular evolution of snake venom proteins

    Directory of Open Access Journals (Sweden)

    Kini R Manjunatha

    2009-06-01

    Full Text Available Abstract Background Snake venom toxins evolve more rapidly than other proteins through accelerated changes in the protein coding regions. Previously we have shown that accelerated segment switch in exons to alter targeting (ASSET might play an important role in its functional evolution of viperid three-finger toxins. In this phenomenon, short sequences in exons are radically changed to unrelated sequences and hence affect the folding and functional properties of the toxins. Results Here we analyzed other snake venom protein families to elucidate the role of ASSET in their functional evolution. ASSET appears to be involved in the functional evolution of three-finger toxins to a greater extent than in several other venom protein families. ASSET leads to replacement of some of the critical amino acid residues that affect the biological function in three-finger toxins as well as change the conformation of the loop that is involved in binding to specific target sites. Conclusion ASSET could lead to novel functions in snake venom proteins. Among snake venom serine proteases, ASSET contributes to changes in three surface segments. One of these segments near the substrate binding region is known to affect substrate specificity, and its exchange may have significant implications for differences in isoform catalytic activity on specific target protein substrates. ASSET therefore plays an important role in functional diversification of snake venom proteins, in addition to accelerated point mutations in the protein coding regions. Accelerated point mutations lead to fine-tuning of target specificity, whereas ASSET leads to large-scale replacement of multiple functionally important residues, resulting in change or gain of functions.

  12. Pseudospark switches

    International Nuclear Information System (INIS)

    The pseudospark discharge is bound to a geometrical structure which is particularly well suited for switching high currents and voltages at high power levels. This type of discharge offers the potential for improvement in essentially all areas of switching operation: peak current and current density, current rise, stand-off voltage, reverse current capability, cathode life, and forward drop. The first pseudospark switch was built at CERN at 1981. Since then, the basic switching characteristics of pseudospark chambers have been studied in detail. The main feature of a pseudospark switch is the confinement of the discharge plasma to the device axis. The current transition to the hollow electrodes is spread over a rather large surface area. Another essential feature is the easy and precise triggering of the pseudospark switch from the interior of the hollow electrodes, relatively far from the main discharge gap. Nanosecond delay and jitter values can be achieved with trigger energies of less than 0.1 mJ, although cathode heating is not required. Pseudospark gaps may cover a wide range of high-voltage, high-current, and high-pulse-power switching at repetition rates of many kilohertz. This report reviews the basic researh on pseudospark switches which has been going on at CERN. So far, applications have been developed in the range of thyratron-like medium-power switches at typically 20 to 40 kV and 0.5 to 10 kA. High-current pseudospark switches have been built for a high-power 20 kJ pulse generator which is being used for long-term tests of plasma lenses developed for the future CERN Antiproton Collector (ACOL). The high-current switches have operated for several hundred thousand shots, with 20 to 50 ns jitter at 16 kV charging voltage and more than 100 kA peak current amplitude. (orig.)

  13. CIRCUIT SWITCHING VERSUS PACKET SWITCHING

    OpenAIRE

    Sneps-Sneppe, Manfred

    2015-01-01

    Communication specialists around the world are facing the same problem: shifting from circuit switching (CS) to packet switching (CS). Communication service providers are favoring “All-over-IP” technologies hoping to boost their profits by providing multimedia services. The main stakeholder in this field of the paradigm shift is the industry itself: packet switching hardware manufacturers are going to earn billions of dollars and thus pay engineers and journalists many millions for the promot...

  14. Optical switches and switching methods

    Energy Technology Data Exchange (ETDEWEB)

    Doty, Michael

    2008-03-04

    A device and method for collecting subject responses, particularly during magnetic imaging experiments and testing using a method such as functional MRI. The device comprises a non-metallic input device which is coupled via fiber optic cables to a computer or other data collection device. One or more optical switches transmit the subject's responses. The input device keeps the subject's fingers comfortably aligned with the switches by partially immobilizing the forearm, wrist, and/or hand of the subject. Also a robust nonmetallic switch, particularly for use with the input device and methods for optical switching.

  15. Discovery of a regioselectivity switch in nitrating P450s guided by molecular dynamics simulations and Markov models

    Science.gov (United States)

    Dodani, Sheel C.; Kiss, Gert; Cahn, Jackson K. B.; Su, Ye; Pande, Vijay S.; Arnold, Frances H.

    2016-05-01

    The dynamic motions of protein structural elements, particularly flexible loops, are intimately linked with diverse aspects of enzyme catalysis. Engineering of these loop regions can alter protein stability, substrate binding and even dramatically impact enzyme function. When these flexible regions are unresolvable structurally, computational reconstruction in combination with large-scale molecular dynamics simulations can be used to guide the engineering strategy. Here we present a collaborative approach that consists of both experiment and computation and led to the discovery of a single mutation in the F/G loop of the nitrating cytochrome P450 TxtE that simultaneously controls loop dynamics and completely shifts the enzyme's regioselectivity from the C4 to the C5 position of L-tryptophan. Furthermore, we find that this loop mutation is naturally present in a subset of homologous nitrating P450s and confirm that these uncharacterized enzymes exclusively produce 5-nitro-L-tryptophan, a previously unknown biosynthetic intermediate.

  16. Discovery of a regioselectivity switch in nitrating P450s guided by molecular dynamics simulations and Markov models.

    Science.gov (United States)

    Dodani, Sheel C; Kiss, Gert; Cahn, Jackson K B; Su, Ye; Pande, Vijay S; Arnold, Frances H

    2016-05-01

    The dynamic motions of protein structural elements, particularly flexible loops, are intimately linked with diverse aspects of enzyme catalysis. Engineering of these loop regions can alter protein stability, substrate binding and even dramatically impact enzyme function. When these flexible regions are unresolvable structurally, computational reconstruction in combination with large-scale molecular dynamics simulations can be used to guide the engineering strategy. Here we present a collaborative approach that consists of both experiment and computation and led to the discovery of a single mutation in the F/G loop of the nitrating cytochrome P450 TxtE that simultaneously controls loop dynamics and completely shifts the enzyme's regioselectivity from the C4 to the C5 position of L-tryptophan. Furthermore, we find that this loop mutation is naturally present in a subset of homologous nitrating P450s and confirm that these uncharacterized enzymes exclusively produce 5-nitro-L-tryptophan, a previously unknown biosynthetic intermediate. PMID:27102675

  17. An acidic loop and cognate phosphorylation sites define a molecular switch that modulates ubiquitin charging activity in Cdc34-like enzymes.

    Directory of Open Access Journals (Sweden)

    Elena Papaleo

    2011-05-01

    Full Text Available E2 ubiquitin-conjugating enzymes are crucial mediators of protein ubiquitination, which strongly influence the ultimate fate of the target substrates. Recently, it has been shown that the activity of several enzymes of the ubiquitination pathway is finely tuned by phosphorylation, an ubiquitous mechanism for cellular regulation, which modulates protein conformation. In this contribution, we provide the first rationale, at the molecular level, of the regulatory mechanism mediated by casein kinase 2 (CK2 phosphorylation of E2 Cdc34-like enzymes. In particular, we identify two co-evolving signature elements in one of the larger families of E2 enzymes: an acidic insertion in β4α2 loop in the proximity of the catalytic cysteine and two conserved key serine residues within the catalytic domain, which are phosphorylated by CK2. Our investigations, using yeast Cdc34 as a model, through 2.5 µs molecular dynamics simulations and biochemical assays, define these two elements as an important phosphorylation-controlled switch that modulates opening and closing of the catalytic cleft. The mechanism relies on electrostatic repulsions between a conserved serine phosphorylated by CK2 and the acidic residues of the β4α2 loop, promoting E2 ubiquitin charging activity. Our investigation identifies a new and unexpected pivotal role for the acidic loop, providing the first evidence that this loop is crucial not only for downstream events related to ubiquitin chain assembly, but is also mandatory for the modulation of an upstream crucial step of the ubiquitin pathway: the ubiquitin charging in the E2 catalytic cleft.

  18. Glucosidase II β-subunit, a novel substrate for caspase-3-like activity in rice, plays as a molecular switch between autophagy and programmed cell death.

    Science.gov (United States)

    Cui, Jing; Chen, Bing; Wang, Hongjuan; Han, Yue; Chen, Xi; Zhang, Wei

    2016-01-01

    Endoplasmic reticulum (ER) stress activates unfolded protein response (UPR) and autophagy. However, prolonged, severe stresses activate programmed cell death (PCD) in both animal and plant cells. Compared to the well-studied UPR pathway, the molecular mechanisms of ER-stress-induced PCD are less understood. Here, we report the identification of Gas2, the glucosidase II β subunit in the ER, as a potential switch between PCD and autophagy in rice. MS analysis identified Gas2, GRP94, and HSP40 protein in a purified caspase-3-like activity from heat stressed rice cell suspensions. The three corresponding genes were down-regulated under DTT-induced ER stress. Gas2 and GRP94 were localized to the ER, while HSP40 localized to the cytoplasm. Compared to wild-type, a Gas2 RNAi cell line was much sensitive to DTT treatment and had high levels of autophagy. Both caspase-3 and heat-stressed cell suspension lysate could cleave Gas2, producing a 14 kDa N-terminal fragment. Conditional expression of corresponding C-terminal fragment resulted in enhanced caspase-3-like activity in the protoplasts under heat stress. We proposed that mild ER stress causes down-regulation of Gas2 and induces autophagy, while severe stress results in Gas2 cleavage by caspase-3-like activity and the cleavage product amplifies this activity, possibly participating in the initiation of PCD. PMID:27538481

  19. Cellular Dichotomy Between Anchorage-Independent Growth Responses to bFGF and TA Reflects Molecular Switch in Commitment to Carcinogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Waters, Katrina M.; Tan, Ruimin; Opresko, Lee K.; Quesenberry, Ryan D.; Bandyopadhyay, Somnath; Chrisler, William B.; Weber, Thomas J.

    2009-11-01

    We have investigated gene expression patterns underlying reversible and irreversible anchorage-independent growth (AIG) phenotypes to identify more sensitive markers of cell transformation for studies directed at interrogating carcinogenesis responses. In JB6 mouse epidermal cells, basic fibroblast growth factor (bFGF) induces an unusually efficient and reversible AIG response, relative to 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced AIG which is irreversible. The reversible and irreversible AIG phenotypes are characterized by largely non-overlapping global gene expression profiles. However, a subset of differentially expressed genes were identified as common to reversible and irreversible AIG phenotypes, including genes regulated in a reciprocal fashion. Hepatic leukemia factor (HLF) and D-site albumin promoter-binding protein (DBP) were increased in both bFGF and TPA soft agar colonies and selected for functional validation. Ectopic expression of human HLF and DBP in JB6 cells resulted in a marked increase in TPA- and bFGF-regulated AIG responses. HLF and DBP expression were increased in soft agar colonies arising from JB6 cells exposed to gamma radiation and in a human basal cell carcinoma tumor tissue, relative to paired non-tumor tissue. Subsequent biological network analysis suggests that many of the differentially expressed genes that are common to bFGF- and TPA-dependent AIG are regulated by c-Myc, SP-1 and HNF-4 transcription factors. Collectively, we have identified a potential molecular switch that mediates the transition from reversible to irreversible AIG.

  20. A novel transcription factor-like gene SbSDR1 acts as a molecular switch and confers salt and osmotic endurance to transgenic tobacco.

    Science.gov (United States)

    Singh, Vijay Kumar; Mishra, Avinash; Haque, Intesaful; Jha, Bhavanath

    2016-01-01

    A salt- and drought-responsive novel gene SbSDR1 is predominantly localised to the nucleus, up-regulated under abiotic stresses and is involved in the regulation of metabolic processes. SbSDR1 showed DNA-binding activity to genomic DNA, microarray analysis revealed the upregulation of host stress-responsive genes and the results suggest that SbSDR1 acts as a transcription factor. Overexpression of SbSDR1 did not affect the growth and yield of transgenic plants in non-stress conditions. Moreover, the overexpression of SbSDR1 stimulates the growth of plants and enhances their physiological status by modulating the physiology and inhibiting the accumulation of reactive oxygen species under salt and osmotic stress. Transgenic plants that overexpressed SbSDR1 had a higher relative water content, membrane integrity and concentration of proline and total soluble sugars, whereas they showed less electrolyte leakage and lipid peroxidation than wild type plants under stress conditions. In field conditions, SbSDR1 plants recovered from stress-induced injuries and could complete their life cycle. This study suggests that SbSDR1 functions as a molecular switch and contributes to salt and osmotic tolerance at different growth stages. Overall, SbSDR1 is a potential candidate to be used for engineering salt and drought tolerance in crops without adverse effects on growth and yield. PMID:27550641

  1. Trimethylamine-N-oxide switches from stabilizing nature: A mechanistic outlook through experimental techniques and molecular dynamics simulation.

    Science.gov (United States)

    Rani, Anjeeta; Jayaraj, Abhilash; Jayaram, B; Pannuru, Venkatesu

    2016-01-01

    In adaptation biology of the discovery of the intracellular osmolytes, the osmolytes are found to play a central role in cellular homeostasis and stress response. A number of models using these molecules are now poised to address a wide range of problems in biology. Here, a combination of biophysical measurements and molecular dynamics (MD) simulation method is used to examine the effect of trimethylamine-N-oxide (TMAO) on stem bromelain (BM) structure, stability and function. From the analysis of our results, we found that TMAO destabilizes BM hydrophobic pockets and active site as a result of concerted polar and non-polar interactions which is strongly evidenced by MD simulation carried out for 250 ns. This destabilization is enthalpically favourable at higher concentrations of TMAO while entropically unfavourable. However, to the best of our knowledge, the results constitute first detailed unambiguous proof of destabilizing effect of most commonly addressed TMAO on the interactions governing stability of BM and present plausible mechanism of protein unfolding by TMAO. PMID:27025561

  2. A molecular switch between the outer and the inner vestibule of the voltage-gated Na+ channel

    International Nuclear Information System (INIS)

    conformational change of the inner vestibule generates the IUS state. In order to explain the involvement of both the outer and the inner vestibule in ultra-slow inactivation, we proposed a model in which the mutation K1237E produces a conformational change of the outer vestibule which is transmitted to the internal vestibule through the DIV- S6 segment. The resulting conformational change of the internal vestibule gives rise to the extremely stable IUS state. If this molecular mechanism holds true, then mutations at the location of interaction between the selectivity filter and the adjacent S6 segment should substantially modulate the ultra-slow inactivated state. A homology model of the voltage-gated Na+ channel, based on the crystal structure of the KcsA channel places the domain IV-S6 segment in close proximity to the domain III P-loop (containing the site 1237 which is essential for the generation of IUS). In order to search for experimental evidence for an interaction site between the domain III P-loop and the internal vestibule we generated serial alanine and cysteine replacements of amino acids of the domain DIV- S6 segment in the background of the mutation K1237E. We find that mutations only at the site 1575 substantially decrease the likelihood of entry into IUS or significantly accelerate recovery from IUS, suggesting that this residue represents an interaction site between the domain III p-loop and the domain IV- S6 segment. For the first time these functional data confirm a molecular model in which the turn of the domain III P-loop is in close relationship with the domain IV- S6 segment at the level of I1575. (author)

  3. Magnetic switching

    International Nuclear Information System (INIS)

    Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented. 12 refs., 8 figs., 1 tab

  4. Fatores e mecanismos envolvidos na hipertrofia ventricular esquerda e o papel anti-hipertrófico do óxido nítrico Factors and mechanisms involved in left ventricular hypertrophy and the anti-hypertrophic role of nitric oxide

    Directory of Open Access Journals (Sweden)

    José Antonio Dias Garcia

    2008-06-01

    , regulating transcription, and will finally determine the genic expression that induces LVH. The LVH is characterized by structural alterations due to the increase in the cardiomyocyte dimensions, the proliferation of the interstitial connective tissue and the rarefaction of the coronary microcirculation. Recently, nitric oxide (•NO has appeared as an important regulator of cardiac remodeling, specifically recognized as an anti-hypertrophic mediator. Some studies have demonstrated the cellular targets, the anti-hypertrophic signaling pathways and the functional role of •NO. Thus, the LVH seems to develop as a result of the loss of the balance between the pro and the anti-hypertrophic signaling pathways. This new knowledge about the pro and anti-hypertrophic signaling pathways will allow the development of new strategies in the treatment of pathological LVH.

  5. 8-Quinolineboronic acid as a potential phosphorescent molecular switch for the determination of alpha-fetoprotein variant for the prediction of primary hepatocellular carcinoma

    International Nuclear Information System (INIS)

    8-Quinolineboronic acid phosphorescent molecular switch (8-QBA-PMS) in the 'off' state emitted weak room temperature phosphorescence (RTP) of 8-QBA on the acetylcellulose membrane (ACM) with the perturbation of Pb2+. When 8-QBA-PMS was used to label concanavalin agglutinin (Con A) to form 8-QBA-PMS-Con A based on the reaction between -OH of 8-QBA-PMS and -COOH of Con A, 8-QBA-PMS turned 'on' automatically due to its structure change, and RTP of the system increased 2.7 times. Besides, -NH2 of 8-QBA-PMS-Con A could carry out affinity adsorption (AA) reaction with the -COOH of alpha-fetoprotein variant (AFP-V) to form the product Con A-AFP-V-Con A-8-QBA-PMS containing -NH-CO- bond, causing the RTP of the system to further increase. Moreover, the amount of AFP-V was linear to the ΔIp of the system in the range of 0.012-2.40 (fg spot-1). Thus, a new affinity sensitive adsorption solid substrate room temperature phosphorimetry using 8-QBA-PMS as labelling reagent (8-QBA-PMS-AASSRTP) for the determination of AFP-V was proposed with the detection limit (LD) of 9 x 10-15 g mL-1. It had been used to determine AFP-V in human serum with the results agreeing with enzyme-link immunoassay (ELISA), showing promise for the prediction of PHC due to the intimate association between AFP-V and primary hepatocellular carcinoma (PHC). The mechanism of the promethod was also discussed.

  6. The Molecular Switch of Telomere Phages: High Binding Specificity of the PY54 Cro Lytic Repressor to a Single Operator Site.

    Science.gov (United States)

    Hammerl, Jens Andre; Roschanski, Nicole; Lurz, Rudi; Johne, Reimar; Lanka, Erich; Hertwig, Stefan

    2015-06-01

    Temperate bacteriophages possess a molecular switch, which regulates the lytic and lysogenic growth. The genomes of the temperate telomere phages N15, PY54 and ɸKO2 harbor a primary immunity region (immB) comprising genes for the prophage repressor, the lytic repressor and a putative antiterminator. The roles of these products are thought to be similar to those of the lambda proteins CI, Cro and Q, respectively. Moreover, the gene order and the location of several operator sites in the prototype telomere phage N15 and in ɸKO2 are also reminiscent of lambda-like phages. By contrast, in silico analyses revealed the presence of only one operator (O\\(_{\\rm{R}}\\)3) in PY54. The purified PY54 Cro protein was used for EMSA studies demonstrating that it exclusively binds to a 16-bp palindromic site (O\\(_{\\rm{R}}\\)3) upstream of the prophage repressor gene. The O\\(_{\\rm{R}}\\)3 operator sequences of PY54 and ɸKO2/N15 only differ by their peripheral base pairs, which are responsible for Cro specificity. PY54 cI and cro transcription is regulated by highly active promoters initiating the synthesis of a homogenious species of leaderless mRNA. The location of the PY54 Cro binding site and of the identified promoters suggests that the lytic repressor suppresses cI transcription but not its own synthesis. The results indicate an unexpected diversity of the growth regulation mechanisms in lambda-related phages. PMID:26043380

  7. The Molecular Switch of Telomere Phages: High Binding Specificity of the PY54 Cro Lytic Repressor to a Single Operator Site

    Directory of Open Access Journals (Sweden)

    Jens Andre Hammerl

    2015-06-01

    Full Text Available Temperate bacteriophages possess a molecular switch, which regulates the lytic and lysogenic growth. The genomes of the temperate telomere phages N15, PY54 and ɸKO2 harbor a primary immunity region (immB comprising genes for the prophage repressor, the lytic repressor and a putative antiterminator. The roles of these products are thought to be similar to those of the lambda proteins CI, Cro and Q, respectively. Moreover, the gene order and the location of several operator sites in the prototype telomere phage N15 and in ɸKO2 are also reminiscent of lambda-like phages. By contrast, in silico analyses revealed the presence of only one operator (O\\(_{\\rm{R}}\\3 in PY54. The purified PY54 Cro protein was used for EMSA studies demonstrating that it exclusively binds to a 16-bp palindromic site (O\\(_{\\rm{R}}\\3 upstream of the prophage repressor gene. The O\\(_{\\rm{R}}\\3 operator sequences of PY54 and ɸKO2/N15 only differ by their peripheral base pairs, which are responsible for Cro specificity. PY54 cI and cro transcription is regulated by highly active promoters initiating the synthesis of a homogenious species of leaderless mRNA. The location of the PY54 Cro binding site and of the identified promoters suggests that the lytic repressor suppresses cI transcription but not its own synthesis. The results indicate an unexpected diversity of the growth regulation mechanisms in lambda-related phages.

  8. Molecular Electronics

    OpenAIRE

    Heath, James R.

    2009-01-01

    Molecular electronics describes the field in which molecules are utilized as the active (switching, sensing, etc.) or passive (current rectifiers, surface passivants) elements in electronic devices. This review focuses on experimental aspects of molecular electronics that researchers have elucidated over the past decade or so and that relate to the fabrication of molecular electronic devices in which the molecular components are readily distinguished within the electronic properties of the de...

  9. Nanoelectromechanical contact switches

    Science.gov (United States)

    Loh, Owen Y.; Espinosa, Horacio D.

    2012-05-01

    Nanoelectromechanical (NEM) switches are similar to conventional semiconductor switches in that they can be used as relays, transistors, logic devices and sensors. However, the operating principles of NEM switches and semiconductor switches are fundamentally different. These differences give NEM switches an advantage over semiconductor switches in some applications -- for example, NEM switches perform much better in extreme environments -- but semiconductor switches benefit from a much superior manufacturing infrastructure. Here we review the potential of NEM-switch technologies to complement or selectively replace conventional complementary metal-oxide semiconductor technology, and identify the challenges involved in the large-scale manufacture of a representative set of NEM-based devices.

  10. Determination of trace alkaline phosphatase by affinity adsorption solid substrate room temperature phosphorimetry based on wheat germ agglutinin labeled with 8-quinolineboronic acid phosphorescent molecular switch and prediction of diseases

    Science.gov (United States)

    Liu, Jia-Ming; Gao, Hui; Li, Fei-Ming; Shi, Xiu-Mei; Lin, Chang-Qing; Lin, Li-Ping; Wang, Xin-Xing; Li, Zhi-Ming

    2010-09-01

    The 8-quinolineboronic acid phosphorescent molecular switch (abbreviated as PMS-8-QBA. Thereinto, 8-QBA is 8-quinolineboronic acid, and PMS is phosphorescent molecular switch) was found for the first time. PMS-8-QBA, which was in the "off" state, could only emit weak room temperature phosphorescence (RTP) on the acetyl cellulose membrane (ACM). However, PMS-8-QBA turned "on" automatically for its changed structure, causing that the RTP of 8-QBA in the system increased, after PMS-8-QBA-WGA (WGA is wheat germ agglutinin) was formed by reaction between -OH of PMS-8-QBA and -COOH of WGA. More interesting is that the -NH 2 of PMS-8-QBA-WGA could react with the -COOH of alkaline phosphatase (AP) to form the affinity adsorption (AA) product WGA-AP-WGA-8-QBA-PMS (containing -NH-CO- bond), which caused RTP of the system to greatly increase. Thus, affinity adsorption solid substrate room temperature phosphorimetry using PMS-8-QBA as labelling reagent (PMS-8-QBA-AA-SSRTP) for the determination of trace AP was established. The method had many advantages, such as high sensitivity (the detection limit (LD) was 2.5 zg spot -1. For sample volume of 0.40 μl spot -1, corresponding concentration was 6.2 × 10 -18 g ml -1), good selectivity (the allowed concentration of coexisting material was higher, when the relative error was ±5%), high accuracy (applied to detection of AP content in serum samples, the result was coincided with those obtained by enzyme-linked immunoassay), which was suitable for the detection of trace AP content in serum samples and the forecast of human diseases. Meanwhile, the mechanism of PMS-8-QBA-AASSRTP was discussed. The new field of analytical application and clinic diagnosis technique of molecule switch are exploited, based on the phosphorescence characteristic of PMS-8-QBA, the AA reaction between WGA and AP, as well as the relation between AP content and human diseases. The research results promote the development and interpenetrate among molecule

  11. Volatile and nonvolatile selective switching of a photo-assisted initialized atomic switch

    International Nuclear Information System (INIS)

    A photo-assisted atomic switch, which has a photoconductive molecular layer in a gap of about 20 nm between an Ag2S electrode and a Pt electrode, is set to a conventional gap-type atomic switch operation mode by light irradiation with the application of a small bias that precipitates Ag atoms from an Ag2S electrode. After this initialization, the switch operates only with application of a bias. In this study, we also found that after the set-operation a photo-assisted initialized atomic switch shows different switching modes depending on the bias range, i.e., volatile switching when the applied bias is smaller than the threshold bias, and nonvolatile switching when the applied bias is larger than the threshold bias. These characteristics can be useful in reconfiguring a circuit such as in neural computing systems. (paper)

  12. Switched on!

    CERN Multimedia

    2008-01-01

    Like a star arriving on stage, impatiently followed by each member of CERN personnel and by millions of eyes around the world, the first beam of protons has circulated in the LHC. After years in the making and months of increasing anticipation, today the work of hundreds of people has borne fruit. WELL DONE to all! Successfully steered around the 27 kilometres of the world’s most powerful particle accelerator at 10:28 this morning, this first beam of protons circulating in the ring marks a key moment in the transition from over two decades of preparation to a new era of scientific discovery. "It’s a fantastic moment," said the LHC project leader Lyn Evans, "we can now look forward to a new era of understanding about the origins and evolution of the universe". Starting up a major new particle accelerator takes much more than flipping a switch. Thousands of individual elements have to work in harmony, timings have to be synchronize...

  13. Photochromic switching of spiropyran in polymer matrices

    Czech Academy of Sciences Publication Activity Database

    Janus, K.; Wierzchowiec, P.; Sworakowski, J.; Nešpůrek, Stanislav

    Poznan : Institute of Molecular Physics Polish Academy of Sciences, 2004. s. 40. [Conference on New Concepts and Materials for Molecular Electronics and Nanotechnology. 11.09.2004-15.09.2004, Puszczykovwo near Poznan] R&D Projects: GA ČR GA202/01/0518 Keywords : photochromism * switching * spiropyran Subject RIV: BM - Solid Matter Physics ; Magnetism

  14. An acidic loop and cognate phosphorylation sites define a molecular switch that modulates ubiquitin charging activity in Cdc34-like enzymes

    DEFF Research Database (Denmark)

    Papaleo, Elena; Ranzani, Valeria; Tripodi, Farida; Vitriolo, Alessandro; Cirulli, Claudia; Fantucci, Piercarlo; Alberghina, Lilia; Vanoni, Marco; De Gioia, Luca; Coccetti, Paola

    2011-01-01

    mechanism for cellular regulation, which modulates protein conformation. In this contribution, we provide the first rationale, at the molecular level, of the regulatory mechanism mediated by casein kinase 2 (CK2) phosphorylation of E2 Cdc34-like enzymes. In particular, we identify two co-evolving signature...... elements in one of the larger families of E2 enzymes: an acidic insertion in β4α2 loop in the proximity of the catalytic cysteine and two conserved key serine residues within the catalytic domain, which are phosphorylated by CK2. Our investigations, using yeast Cdc34 as a model, through 2.5 µs molecular...

  15. An Acidic Loop and Cognate Phosphorylation Sites Define a Molecular Switch That Modulates Ubiquitin Charging Activity in Cdc34-Like Enzymes

    OpenAIRE

    Papaleo, Elena; Ranzani, Valeria; Tripodi, Farida; Vitriolo, Alessandro; Cirulli, Claudia; Fantucci, Piercarlo; Alberghina, Lilia; Vanoni, Marco; De Gioia, Luca; Coccetti, Paola

    2011-01-01

    E2 ubiquitin-conjugating enzymes are crucial mediators of protein ubiquitination, which strongly influence the ultimate fate of the target substrates. Recently, it has been shown that the activity of several enzymes of the ubiquitination pathway is finely tuned by phosphorylation, an ubiquitous mechanism for cellular regulation, which modulates protein conformation. In this contribution, we provide the first rationale, at the molecular level, of the regulatory mechanism mediated by casein kin...

  16. Adenylyl cyclase-5 in the dorsal striatum function as a molecular switch for the generation of behavioral preferences for cue-directed food choices

    OpenAIRE

    Kim, Hannah; Kim, Tae-Kyung; KIM, Ji-Eun; Park, Jin-Young; Lee, Yunjin; Kang, Minkyung; Kim, Kyoung-Shim; Han, Pyung-Lim

    2014-01-01

    Background Behavioral choices in habits and innate behaviors occur automatically in the absence of conscious selection. These behaviors are not easily modified by learning. Similar types of behaviors also occur in various mental illnesses including drug addiction, obsessive-compulsive disorder, schizophrenia, and autism. However, underlying mechanisms are not clearly understood. In the present study, we investigated the molecular mechanisms regulating unconditioned preferred behaviors in food...

  17. Heat Switches for ADRs

    Science.gov (United States)

    DiPirro, M. J.; Shirron, P. J.

    2014-01-01

    Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper.

  18. Controller Architectures for Switching

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik; Poulsen, Niels Kjølstad

    2009-01-01

    This paper investigate different controller architectures in connection with controller switching. The controller switching is derived by using the Youla-Jabr-Bongiorno-Kucera (YJBK) parameterization. A number of different architectures for the implementation of the YJBK parameterization are...... described and applied in connection with controller switching. An architecture that does not include inversion of the coprime factors is introduced. This architecture will make controller switching particular simple....

  19. Switching mode power supplies

    OpenAIRE

    Beard, David W.

    1980-01-01

    The subject of switching mode power supplies was examined. A comparison between linear regulators and switching mode power supplies was made to show the options available for the various types of convertors. Two switching mode power supplies were constructed and tested. The operating efficiency of both systems was found to be more than eighty percent over the specified input voltage and load current conditions. The switching mode power supply circuits required additional ...

  20. MOSFET as a Switch

    OpenAIRE

    Dhaval Agrawal

    2014-01-01

    s as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as ...

  1. Optical packet switched networks

    DEFF Research Database (Denmark)

    Hansen, Peter Bukhave

    1999-01-01

    Optical packet switched networks are investigated with emphasis on the performance of the packet switch blocks. Initially, the network context of the optical packet switched network is described showing that a packet network will provide transparency, flexibility and bridge the granularity gap...... between the electrical switched layer and the WDM transport layer. Analytical models are implemented to determine the signal quality ghrough the switch blocks in terms of power penalty and to assess the traffic performance of different switch block architectures. Further, a computer simulation model...... in interferometric wavelength converters is investigated showing that a 10 Gbit/s 19 4x4 swich blocks can be cascaded at a BER of 10-14. An analytical traffic model enables the calculation of the traffice performance of a WDM packet network. Hereby the importance of WDM and wavelegth conversion in the switch blocks...

  2. Binding properties of ruthenium(II) complexes [Ru(bpy)2(ppn)](2+) and [Ru(phen)2(ppn)](2+) with triplex RNA: As molecular "light switches" and stabilizers for poly(U)·poly(A)*poly(U) triplex.

    Science.gov (United States)

    Li, Jia; Sun, Yanmei; Zhu, Zhiyuan; Zhao, Hong; Tan, Lifeng

    2016-08-01

    Stable RNA triplexes play key roles in many biological processes, while triplexes are thermodynamically less stable than the corresponding duplexes due to the Hoogsteen base pairing. To understand the factors affecting the stabilization of RNA triplexes by octahedral ruthenium(II) complexes, the binding of [Ru(bpy)2(ppn)](2+) (1, bpy=2,2'-bipyridine, ppn=2,4-diaminopyrimido[5,6-b]dipyrido[2,3-f:2',3'-h]quinoxaline) and [Ru(phen)2(ppn)](2+) (2, phen=1,10-phenanthroline) to poly(U)·poly(A)*poly(U) (· denotes the Watson-Crick base pairing and * denotes the Hoogsteen base pairing) has been investigated. The main results obtained here suggest that complexes 1 and 2 can serve as molecular "light switches" and stabilizers for poly(U)·poly(A)*poly(U), while the effectiveness of complex 2 are more marked, suggesting that the hydrophobicity of ancillary ligands has a significant effect on the two Ru(II) complexes binding to poly(U)·poly(A)*poly(U). This study further advances our knowledge on the binding of RNA triplexes with metal complexes, particularly with octahedral ruthenium polypyridyl complexes. PMID:27287059

  3. Light-Induced Switching of Tunable Single-Molecule Junctions

    KAUST Repository

    Sendler, Torsten

    2015-04-16

    A major goal of molecular electronics is the development and implementation of devices such as single-molecular switches. Here, measurements are presented that show the controlled in situ switching of diarylethene molecules from their nonconductive to conductive state in contact to gold nanoelectrodes via controlled light irradiation. Both the conductance and the quantum yield for switching of these molecules are within a range making the molecules suitable for actual devices. The conductance of the molecular junctions in the opened and closed states is characterized and the molecular level E 0, which dominates the current transport in the closed state, and its level broadening Γ are identified. The obtained results show a clear light-induced ring forming isomerization of the single-molecule junctions. Electron withdrawing side-groups lead to a reduction of conductance, but do not influence the efficiency of the switching mechanism. Quantum chemical calculations of the light-induced switching processes correlate these observations with the fundamentally different low-lying electronic states of the opened and closed forms and their comparably small modification by electron-withdrawing substituents. This full characterization of a molecular switch operated in a molecular junction is an important step toward the development of real molecular electronics devices.

  4. A Nonvolatile Plasmonic Switch Employing Photochromic Molecules

    International Nuclear Information System (INIS)

    We demonstrate a surface plasmon-polariton (SPP) waveguide all-optical switch that combines the unique physical properties of small molecules and metallic (plasmonic) nanostructures. The switch consists of a pair of gratings defined in an aluminum film coated with a 65 nm thick layer of photochromic (PC) molecules. The first grating couples a signal beam consisting of free space photons to SPPs that interact effectively with the PC molecules. These molecules can reversibly be switched between transparent and absorbing states using a free space optical pump. In the transparent (signal 'on') state, the SPPs freely propagate through the molecular layer, and in the absorbing (signal 'off') state, the SPPs are strongly attenuated. The second grating serves to decouple the SPPs back into a free space optical beam, enabling measurement of the modulated signal with a far-field detector. In a preliminary study, the switching behavior of the PC molecules themselves was confirmed and quantified by surface plasmon resonance spectroscopy. The excellent (16%) overlap of the SPP mode profile with the thin layer of switching molecules enabled efficient switching with power densities of ∼6.0 mW/cm2 in 1.5 (micro)m x 8 (micro) m devices, resulting in plasmonic switching powers of 0.72 nW per device. Calculations further showed that modulation depths in access of 20 dB can easily be attained in optimized designs. The quantitative experimental and theoretical analysis of the nonvolatile switching behavior in this letter guides the design of future nanoscale optically or electrically pumped optical switches.

  5. The magnetoelectrochemical switch.

    Science.gov (United States)

    Popa, Petru Lunca; Kemp, Neil T; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

    2014-07-22

    In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 10(3). The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

  6. Introduction to Optical Burst Switching

    OpenAIRE

    KERNÁCS János; SZILÁGYI Szabolcs

    2010-01-01

    Optical Burst Switching (OBS) isconsidered a popular switching paradigm for therealization of all-optical networks due to the balance itoffers between the coarse-grained Optical CircuitSwitching (OSC) and fine-grained Optical PacketSwitching (OPS). Given that the data are switched allopticallyat the burst level, Optical Burst Switchingcombines the transparency of Optical CircuitSwitching with the benefits of statistical multiplexingin Optical Packet Switching.

  7. Saturated Switching Systems

    CERN Document Server

    Benzaouia, Abdellah

    2012-01-01

    Saturated Switching Systems treats the problem of actuator saturation, inherent in all dynamical systems by using two approaches: positive invariance in which the controller is designed to work within a region of non-saturating linear behaviour; and saturation technique which allows saturation but guarantees asymptotic stability. The results obtained are extended from the linear systems in which they were first developed to switching systems with uncertainties, 2D switching systems, switching systems with Markovian jumping and switching systems of the Takagi-Sugeno type. The text represents a thoroughly referenced distillation of results obtained in this field during the last decade. The selected tool for analysis and design of stabilizing controllers is based on multiple Lyapunov functions and linear matrix inequalities. All the results are illustrated with numerical examples and figures many of them being modelled using MATLAB®. Saturated Switching Systems will be of interest to academic researchers in con...

  8. Emergence of phenotype switching through continuous and discontinuous evolutionary transitions.

    Science.gov (United States)

    Patra, Pintu; Klumpp, Stefan

    2015-07-01

    Bacterial persistence (phenotypic tolerance to antibiotics) provides a prime example of bet-hedging, where normally growing cells generate slow-growing but antibiotic-tolerant persister cells to survive through periods of exposure to antibiotics. The population dynamics of persistence is explained by a phenotype switching mechanism that allows individual cells to switch between these different cellular states with different environmental sensitivities. Here, we perform a theoretical study based on an exact solution for the case of a periodic variation of the environment to address how phenotype switching emerges and under what conditions switching is or is not beneficial for long-time growth. Specifically we report a bifurcation through which a fitness maximum and minimum emerge above a threshold in the duration of exposure to the antibiotic. Only above this threshold, the optimal phenotype switching rates are adjusted to the time scales of the environment, as emphasized by previous theoretical studies, while below the threshold a non-switching population is fitter than a switching one. The bifurcation can be of different type, depending on how the phenotype switching rates are allowed to vary. If the switching rates for both directions of the switch are coupled, the transition is discontinuous and results in evolutionary hysteresis, which we confirm with a stochastic simulation. If the switching rates vary individually, a continuous transition is obtained and no hysteresis is found. We discuss how both scenarios can be linked to changes in the underlying molecular networks. PMID:26020274

  9. FreeSWITCH Cookbook

    CERN Document Server

    Minessale, Anthony

    2012-01-01

    This is a problem-solution approach to take your FreeSWITCH skills to the next level, where everything is explained in a practical way. If you are a system administrator, hobbyist, or someone who uses FreeSWITCH on a regular basis, this book is for you. Whether you are a FreeSWITCH expert or just getting started, this book will take your skills to the next level.

  10. Atomic Scale Plasmonic Switch

    OpenAIRE

    Emboras, A.; Niegemann, J.; Ma, P; Haffner, C; Pedersen, A.; Luisier, M.; Hafner, C; Schimmel, T.; Leuthold, J.

    2016-01-01

    The atom sets an ultimate scaling limit to Moore’s law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocat...

  11. Switched Networks and Complementarity

    OpenAIRE

    Camlıbel, M.K.; Heemels, W.P.M.H; Schaft, van der, A.J.; Schumacher, J.M.

    2003-01-01

    A modeling framework is proposed for circuits that are subject both to externally induced switches (time events) and to state events. The framework applies to switched networks with linear and piecewise-linear elements, including diodes. We show that the linear complementarity formulation, which already has proved effective for piecewise-linear networks, can be extended in a natural way to also cover switching circuits. To achieve this, we use a generalization of the linear complementarity pr...

  12. Stochastic Switching Circuit Synthesis

    OpenAIRE

    Wilhelm, Daniel; Bruck, Jehoshua

    2009-01-01

    Shannon in his 1938 Masterpsilas Thesis demonstrated that any Boolean function can be realized by a switching relay circuit, leading to the development of deterministic digital logic. Here, we replace each classical switch with a probabilistic switch (pswitch). We present algorithms for synthesizing circuits closed with a desired probability, including an algorithm that generates optimal size circuits for any binary fraction. We also introduce a new duality property for series-parallel stocha...

  13. Asymmetrical Switch Costs in Children

    Science.gov (United States)

    Ellefson, Michelle R.; Shapiron, Laura R.; Chater, Nick

    2006-01-01

    Switching between tasks produces decreases in performance as compared to repeating the same task. Asymmetrical switch costs occur when switching between two tasks of unequal difficulty. This asymmetry occurs because the cost is greater when switching to the less difficult task than when switching to the more difficult task. Various theories about…

  14. Multidimensional set switching.

    Science.gov (United States)

    Hahn, Sowon; Andersen, George J; Kramer, Arthur F

    2003-06-01

    The present study examined the organization of preparatory processes that underlie set switching and, more specifically, switch costs. On each trial, subjects performed one of two perceptual judgment tasks, color or shape discrimination. Subjects also responded with one of two different response sets. The task set and/or the response set switched from one to the other after 2-6 repeated trials. Response set, task set, and double set switches were performed in both blocked and randomized conditions. Subjects performed with short (100-msec) and long (800-msec) preparatory intervals. Task and response set switches had an additive effect on reaction times (RTs) in the blocked condition. Such a pattern of results suggests a serial organization of preparatory processes when the nature of switches is predictable. However, task and response set switches had an underadditive effect on RTs in the random condition when subjects performed with a brief cue-to-target interval. This pattern of results suggests overlapping task and response set preparation. These findings are discussed in terms of strategic control of preparatory processes in set switching. PMID:12921431

  15. Single Atom Plasmonic Switch

    CERN Document Server

    Emboras, Alexandros; Ma, Ping; Haffner, Christian; Luisier, Mathieu; Hafner, Christian; Schimmel, Thomas; Leuthold, Juerg

    2015-01-01

    The atom sets an ultimate scaling limit to Moores law in the electronics industry. And while electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling-similar to electronics-is only limited by the atom. More precisely, we introduce an electrically controlled single atom plasmonic switch. The switch allows for fast and reproducible switching by means of the relocation of an individual or at most - a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ration of 10 dB and operation at room temperature with femtojoule (fJ) power consumption for a single switch operation. This demonstration of a CMOS compatible, integrated quantum device allowing to control photons at the single-atom level opens intriguing perspectives for a fully i...

  16. Switch on, switch off: stiction in nanoelectromechanical switches

    KAUST Repository

    Wagner, Till J W

    2013-06-13

    We present a theoretical investigation of stiction in nanoscale electromechanical contact switches. We develop a mathematical model to describe the deflection of a cantilever beam in response to both electrostatic and van der Waals forces. Particular focus is given to the question of whether adhesive van der Waals forces cause the cantilever to remain in the \\'ON\\' state even when the electrostatic forces are removed. In contrast to previous studies, our theory accounts for deflections with large slopes (i.e. geometrically nonlinear). We solve the resulting equations numerically to study how a cantilever beam adheres to a rigid electrode: transitions between \\'free\\', \\'pinned\\' and \\'clamped\\' states are shown to be discontinuous and to exhibit significant hysteresis. Our findings are compared to previous results from linearized models and the implications for nanoelectromechanical cantilever switch design are discussed. © 2013 IOP Publishing Ltd.

  17. Bipolar Conductance Switching of Single Anthradithiophene Molecules.

    Science.gov (United States)

    Borca, Bogdana; Schendel, Verena; Pétuya, Rémi; Pentegov, Ivan; Michnowicz, Tomasz; Kraft, Ulrike; Klauk, Hagen; Arnau, Andrés; Wahl, Peter; Schlickum, Uta; Kern, Klaus

    2015-12-22

    Single molecular switches are basic device elements in organic electronics. The pentacene analogue anthradithiophene (ADT) shows a fully reversible binary switching between different adsorption conformations on a metallic surface accompanied by a charge transfer. These transitions are activated locally in single molecules in a low-temperature scanning tunneling microscope . The switching induces changes between bistable orbital structures and energy level alignment at the interface. The most stable geometry, the "off" state, which all molecules adopt upon evaporation, corresponds to a short adsorption distance at which the electronic interactions of the acene rings bend the central part of the molecule toward the surface accompanied by a significant charge transfer from the metallic surface to the ADT molecules. This leads to a shift of the lowest unoccupied molecular orbital down to the Fermi level (EF). In the "on" state the molecule has a flat geometry at a larger distance from the surface; consequently the interaction is weaker, resulting in a negligible charge transfer with an orbital structure resembling the highest occupied molecular orbital when imaged close to EF. The potential barrier between these two states can be overcome reversibly by injecting charge carriers locally into individual molecules. Voltage-controlled current traces show a hysteresis characteristic of a bipolar switching behavior. The interpretation is supported by first-principles calculations. PMID:26580569

  18. Light-Controlled Conductance Using Molecular Switches

    NARCIS (Netherlands)

    Kudernác, Tibor

    2007-01-01

    A great challenge to present-day applied science is to develop electronic devices at the nanometer scale based on molecules. Diarylethenes are promising synthetic photoswitchable (photochromic) molecules because of the outstanding fatigue-resistant light-induced reversible transformation as they und

  19. Orientation of KRb molecules in a switched electrostatic field

    International Nuclear Information System (INIS)

    We theoretically investigate the orientation of the cold KRb molecules induced in a switched electrostatic field by numerically solving the full time-dependent Schrödinger equation. The results show that the periodic field-free molecular orientation can be realized for the KRb molecules by rapidly switching off the electrostatic field. Meanwhile, by varying the switching times of the electrostatic field, the adiabatic and nonadiabatic interactions of the molecules with the applied field can be realized. Moreover, the influences of the electrostatic field strength and the rotational temperature to the degree of the molecular orientation are studied. The investigations show that increasing the electrostatic field will increase the degree of the molecular orientation, both in the constant-field regime and in the field-free regime, while the increasing of the rotational temperature of the cold molecules will greatly decrease the degree of the molecular orientation. (atomic and molecular physics)

  20. Optical packet switching

    Science.gov (United States)

    Shekel, Eyal; Ruschin, Shlomo; Majer, Daniel; Levy, Jeff; Matmon, Guy; Koenigsberg, Lisa; Vecht, Jacob; Geron, Amir; Harlavan, Rotem; Shfaram, Harel; Arbel, Arnon; McDermott, Tom; Brewer, Tony

    2005-02-01

    We report here a scalable, multichassis, 6.3 terabit core router, which utilizes our proprietary optical switch. The router is commercially available and deployed in several customer sites. Our solution combines optical switching with electronic routing. An internal optical packet switching network interconnects the router"s electronic line cards, where routing and buffering functions take place electronically. The system architecture and performance will be described. The optical switch is based on Optical Phased Array (OPA) technology. It is a 64 x 64, fully non-blocking, optical crossbar switch, capable of switching in a fraction of a nanosecond. The basic principles of operation will be explained. Loss and crosstalk results will be presented, as well as the results of BER measurements of a 160 Gbps transmission through one channel. Basic principles of operation and measured results will be presented for the burst-mode-receivers, arbitration algorithm and synchronization. Finally, we will present some of our current research work on a next-generation optical switch. The technological issues we have solved in our internal optical packet network can have broad applicability to any global optical packet network.

  1. JUNOS Enterprise Switching

    CERN Document Server

    Reynolds, Harry

    2009-01-01

    JUNOS Enterprise Switching is the only detailed technical book on Juniper Networks' new Ethernet-switching EX product platform. With this book, you'll learn all about the hardware and ASIC design prowess of the EX platform, as well as the JUNOS Software that powers it. Not only is this extremely practical book a useful, hands-on manual to the EX platform, it also makes an excellent study guide for certification exams in the JNTCP enterprise tracks. The authors have based JUNOS Enterprise Switching on their own Juniper training practices and programs, as well as the configuration, maintenanc

  2. SPARK GAP SWITCH

    Science.gov (United States)

    Neal, R.B.

    1957-12-17

    An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.

  3. A Metabolic Switch

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    Our muscles are metabolically flexible, i.e., they are capable of `switching' between two types of oxidation: (1) when fasting, a predominantly lipid oxidation with high rates of fatty acid uptake, and (2) when fed, suppression of lipid oxidation in favour of increased glucose uptake, oxidation and...... storage, in response to insulin. One of the many manifestations of obesity and Type 2 diabetes is an insulin resistance of the skeletal muscles, which suppresses this metabolic switch. This talk describes recent development of a low-dimensional system of ODEs that model the metabolic switch, displaying a...

  4. Switch mode power supply

    International Nuclear Information System (INIS)

    This book concentrates on switch mode power supply. It has four parts, which are introduction of switch mode power supply with DC-DC converter such as Buck converter boost converter, Buck-boost converter and PWM control circuit, explanation for SMPS with DC-DC converter modeling and power mode control, resonance converter like resonance switch, converter, multi resonance converter and series resonance and parallel resonance converters, basic test of SMPS with PWM control circuit, Buck converter, Boost converter, flyback converter, forward converter and IC for control circuit.

  5. Switched linear differential systems

    OpenAIRE

    Mayo Maldonado, Jonathan

    2015-01-01

    In this thesis we study systems with switching dynamics and we propose new mathematical tools to analyse them. We show that the postulation of a global state space structure in current frameworks is restrictive and lead to potential difficulties that limit its use for the analysis of new emerging applications. In order to overcome such shortcomings, we reformulate the foundations in the study of switched systems by developing a trajectory-based approach, where we allow the use of models that ...

  6. Photonics in switching

    CERN Document Server

    Midwinter, John E; Kelley, Paul

    1993-01-01

    Photonics in Switching provides a broad, balanced overview of the use of optics or photonics in switching, from materials and devices to system architecture. The chapters, each written by an expert in the field, survey the key technologies, setting them in context and highlighting their benefits and possible applications. This book is a valuable resource for those working in the communications industry, either at the professional or student level, who do not have extensive background knowledge or the underlying physics of the technology.

  7. uv preilluminated gas switches

    International Nuclear Information System (INIS)

    We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 1012 amps/sec with 1 ns jitter. Twenty such modules will be used on the Nova Inertial Confinement Fusion Laser System for plasma retropulse shutters

  8. uv preilluminated gas switches

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, L.P.; Orham, E.L.; Stowers, I.F.; Braucht, J.R.

    1980-06-03

    We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 10/sup 12/ amps/sec with 1 ns jitter. Twenty such modules will be used on the Nova Inertial Confinement Fusion Laser System for plasma retropulse shutters.

  9. Switching to Photonics

    OpenAIRE

    Hinton, Harvard S.

    1992-01-01

    The use of hardware that exploits the interplay of photons and electrons to switch voice, data, and video is discussed. The two directions being taken by current research-guided-wave and free-space photonics-are examined. Photonic time-slot interchanges are described. Multidivisional fabrics, based on a combination of space-division and time-division multiplexing, are considered, as is the wavelength-division-based photonic packet switch, another kind of multidimensional fabric. The use of se...

  10. Switch Attention to Listen

    OpenAIRE

    Dhamani, Imran; Leung, Johahn; Carlile, Simon; Sharma, Mridula

    2013-01-01

    The aim of this research was to evaluate the ability to switch attention and selectively attend to relevant information in children (10–15 years) with persistent listening difficulties in noisy environments. A wide battery of clinical tests indicated that children with complaints of listening difficulties had otherwise normal hearing sensitivity and auditory processing skills. Here we show that these children are markedly slower to switch their attention compared to their age-matched peers. T...

  11. Ferroelectric switching of elastin

    OpenAIRE

    Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; WANG, YUNJIE; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; SHARMA, PRADEEP; Zhang, Yanhang; Li, Jiangyu

    2014-01-01

    Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present, to our knowledge, the first macroscopic observation of ferroelectric switching in a biological system, and we elucidate the origin and mechanism underpinning ferroelectric switching of elastin. It is discovered that the polarization in elastin is intrinsic at the monomer level, analogous to the unit cell level polarizatio...

  12. Understanding and Supporting Window Switching

    NARCIS (Netherlands)

    Tak, S.

    2011-01-01

    Switching between windows on a computer is a frequent activity, but finding and switching to the target window can be inefficient. This thesis aims to better un-derstand and support window switching. It explores two issues: (1) the lack of knowledge of how people currently interact with and switch b

  13. Optical switching systems using nanostructures

    DEFF Research Database (Denmark)

    Stubkjær, Kristian

    2004-01-01

    High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems.......High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems....

  14. Orientation of KRb molecules in a switched electrostatic field

    Institute of Scientific and Technical Information of China (English)

    Huang Yun-Xia; Xu Shu-Wu; Yang Xiao-Hua

    2013-01-01

    We theoretically investigate the orientation of the cold KRb molecules induced in a switched electrostatic field by numerically solving the full time-dependent Schr(o)dinger equation.The results show that the periodic field-free molecular orientation can be realized for the KRb molecules by rapidly switching off the electrostatic field.Meanwhile,by varying the switching times of the electrostatic field,the adiabatic and nonadiabatic interactions of the molecules with the applied field can be realized.Moreover,the influences of the electrostatic field strength and the rotational temperature to the degree of the molecular orientation are studied.The investigations show that increasing the electrostatic field will increase the degree of the molecular orientation,both in the constant-field regime and in the field-free regime,while the increasing of the rotational temperature of the cold molecules will greatly decrease the degree of the molecular orientation.

  15. Switching Power Universality in Unipolar Resistive Switching Memories

    Science.gov (United States)

    Kim, Jongmin; Jung, Kyooho; Kim, Yongmin; Jo, Yongcheol; Cho, Sangeun; Woo, Hyeonseok; Lee, Seongwoo; Inamdar, A. I.; Hong, Jinpyo; Lee, Jeon-Kook; Kim, Hyungsang; Im, Hyunsik

    2016-04-01

    We investigate the resistive switching power from unipolar resistive switching current-voltage characteristics in various binary metal oxide films sandwiched by different metal electrodes, and find a universal feature (the so-called universality) in the switching power among these devices. To experimentally derive the switching power universality, systematic measurements of the switching voltage and current are performed, and neither of these correlate with one another. As the switching resistance (R) increases, the switching power (P) decreases following a power law P ∝ R‑β, regardless of the device configurations. The observed switching power universality is indicative of the existence of a commonly applicable switching mechanism. The origin of the power universality is discussed based on a metallic filament model and thermo-chemical reaction.

  16. Atomic Scale Plasmonic Switch.

    Science.gov (United States)

    Emboras, Alexandros; Niegemann, Jens; Ma, Ping; Haffner, Christian; Pedersen, Andreas; Luisier, Mathieu; Hafner, Christian; Schimmel, Thomas; Leuthold, Juerg

    2016-01-13

    The atom sets an ultimate scaling limit to Moore's law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocation of an individual or, at most, a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ratio of 9.2 dB and operation at room temperature up to MHz with femtojoule (fJ) power consumption for a single switch operation. This demonstration of an integrated quantum device allowing to control photons at the atomic level opens intriguing perspectives for a fully integrated and highly scalable chip platform, a platform where optics, electronics, and memory may be controlled at the single-atom level. PMID:26670551

  17. On stability of switched linear systems with perturbed switching paths

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper addresses the stability issue of switched linear systems with perturbed switching paths. First,by introducing thenotions of child-path and parent-path, we are able to define the distance between two switching paths by means of their switching matrices chains. Next, we present the nice properties of the defined distance. Then, a stability criterion is presented for a class of switched linear systems with perturbed switching paths. Finally, an illustrative example is presented to verify the effectiveness of the approach.

  18. Energy reversible switching from amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-08-01

    We report observation of energy reversible switching from amorphous metal based nanoelectromechanical (NEM) switch. For ultra-low power electronics, NEM switches can be used as a complementary switching element in many nanoelectronic system applications. Its inherent zero power consumption because of mechanical detachment is an attractive feature. However, its operating voltage needs to be in the realm of 1 volt or lower. Appropriate design and lower Young\\'s modulus can contribute achieving lower operating voltage. Therefore, we have developed amorphous metal with low Young\\'s modulus and in this paper reporting the energy reversible switching from a laterally actuated double electrode NEM switch. © 2013 IEEE.

  19. Cooperative Switching in Nanofibers of Azobenzene Oligomers.

    Science.gov (United States)

    Weber, Christopher; Liebig, Tobias; Gensler, Manuel; Zykov, Anton; Pithan, Linus; Rabe, Jürgen P; Hecht, Stefan; Bléger, David; Kowarik, Stefan

    2016-01-01

    Next-generation molecular devices and machines demand the integration of molecular switches into hierarchical assemblies to amplify the response of the system from the molecular level to the meso- or macro-scale. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via intermolecular interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. We find that the photoisomerization rate from the Z-isomer to the E-isomer depends on the fraction of Z-azobenzene in the nanofibers, and is increased by more than a factor of 4 in Z-rich fibers when compared to E-rich fibers. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency in the solid state with potential relevance for actuation and sensing. PMID:27161608

  20. Cooperative Switching in Nanofibers of Azobenzene Oligomers

    Science.gov (United States)

    Weber, Christopher; Liebig, Tobias; Gensler, Manuel; Zykov, Anton; Pithan, Linus; Rabe, Jürgen P.; Hecht, Stefan; Bléger, David; Kowarik, Stefan

    2016-01-01

    Next-generation molecular devices and machines demand the integration of molecular switches into hierarchical assemblies to amplify the response of the system from the molecular level to the meso- or macro-scale. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via intermolecular interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. We find that the photoisomerization rate from the Z-isomer to the E-isomer depends on the fraction of Z-azobenzene in the nanofibers, and is increased by more than a factor of 4 in Z-rich fibers when compared to E-rich fibers. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency in the solid state with potential relevance for actuation and sensing. PMID:27161608

  1. Lineage tracing of human B cells reveals the in vivo landscape of human antibody class switching.

    Science.gov (United States)

    Horns, Felix; Vollmers, Christopher; Croote, Derek; Mackey, Sally F; Swan, Gary E; Dekker, Cornelia L; Davis, Mark M; Quake, Stephen R

    2016-01-01

    Antibody class switching is a feature of the adaptive immune system which enables diversification of the effector properties of antibodies. Even though class switching is essential for mounting a protective response to pathogens, the in vivo patterns and lineage characteristics of antibody class switching have remained uncharacterized in living humans. Here we comprehensively measured the landscape of antibody class switching in human adult twins using antibody repertoire sequencing. The map identifies how antibodies of every class are created and delineates a two-tiered hierarchy of class switch pathways. Using somatic hypermutations as a molecular clock, we discovered that closely related B cells often switch to the same class, but lose coherence as somatic mutations accumulate. Such correlations between closely related cells exist when purified B cells class switch in vitro, suggesting that class switch recombination is directed toward specific isotypes by a cell-autonomous imprinted state. PMID:27481325

  2. An automatic electronic switch

    International Nuclear Information System (INIS)

    The paper describes an electronic switch which, on the order of a single pulse, successively selects a given number of channels. The switching time for all channels may be the same, or may vary according to channel; one or more positions may be maintained by external control for an indefinite length of time. This circuit is very flexible in programming; it can if necessary act as a counter and as a pulse generator. It is convenient to limit the number of switched channels to ten, but this can be greatly increased by a general extension of the system. Applications of an apparatus for transferring the contents of decimal scalers to a printing machine are described; this machine employs the sequential series method and with a binary-decimal scale converter which operates by summing the weights of the different binary digits. (author)

  3. Optical computer switching network

    Science.gov (United States)

    Clymer, B.; Collins, S. A., Jr.

    1985-01-01

    The design for an optical switching system for minicomputers that uses an optical spatial light modulator such as a Hughes liquid crystal light valve is presented. The switching system is designed to connect 80 minicomputers coupled to the switching system by optical fibers. The system has two major parts: the connection system that connects the data lines by which the computers communicate via a two-dimensional optical matrix array and the control system that controls which computers are connected. The basic system, the matrix-based connecting system, and some of the optical components to be used are described. Finally, the details of the control system are given and illustrated with a discussion of timing.

  4. Photonics in Switching

    OpenAIRE

    Hinton, Harvard S.

    1992-01-01

    One of the keys to the future of telecommunications companies will be their ability to provide new broadband services to both the business community and residential customers. With the new services will come the need for the equivalent of a broadband switching office. Such a system could require the capability of supporting in excess of 10000 users with broadband channel bit rates exceeding 100 Mb/s. This implies a switching fabric the aggregate bit rate of which could be greater than 1 Tb/s....

  5. Laboratory Switching Power Supply

    OpenAIRE

    Slezák, Jakub

    2009-01-01

    This bachelor’s thesis is concerned with design switching power supply based on forward converter with output voltage regulated in the range of 3 to 30V and load current to 1 A. First of all, it discusses the theoretical solution of basic types of converters and switching power supply problems. Followed by a proposal of various parts source, which was first established in the test version on the test board. Then was proposed printed circuit board and complete mechanical solutions. Source is a...

  6. mutL Gene:a Spontaneous Molecular Switch to Regulate Bacterial Genetic Stability%mutL基因:自发调节细菌遗传稳定性的分子开关

    Institute of Scientific and Technical Information of China (English)

    陈芳; 刘树林

    2008-01-01

    MutL is one of the core proteins involved in mismatch repair(MMR).It is a weak AT-Pase and binds nonspecifically to DNA.It has been deemed a"matchmaker"as it interacts with.and in some cases stimulates,the activity of a large number of proteins,such as MutS,MutH,UwD and B clamp.Defects in mutL gene result in significantly increased rates of spontaneous mutation and horncologous recombi_nation in bacteria.Recently,we have identified a deletion of one of three tandem 6 bp repeats within mutL(6 bp AmutL)in Salmonella typhimurium LT7.This defect is associated with genome diversification of LT7 and contributed greatly to genetic instability.As the conversion between mutL and 6 bp △mutL could take place spontaneously,we propose that the mutL gene may play a role as a molecular switch to regulate the function of MMR and,especially,the genetic stability of bacteria in adaptation to changing environments.%MutL是错配修复(mismatch repair,MMR)系统的关键组分之一,它具有较弱的AT-Pase活性并能非特异性结合DNA.由于MutL与其他MMR蛋白如MutS、MutH、UvrD及B clamp等之间存在广泛的相互作用,并能在一定程度上刺激它们活性.因此,MutL被广泛认为是MMR过程中关键的分子媒娘.mutL基因缺陷的菌株具有显著增高的自发突变率和同源重组频率.最近,我们在鼠伤寒沙门菌m高变异株的mutL基因中发现一个6碱基串联重复序列的缺失,这种缺陷型mutL(6h·p△mutL)基因可大大促进细菌基因结构的多样化和遗传的不稳定性,并能与mutL自发相互转化.因此,我们认为,mutL可通过这种转化适时而精确地调控MMR系统功能,从而在细菌进化过程充当自发调控遗传稳定性的分子开关.

  7. High-speed switching characteristics of integrated optoelectronic crossbar switch

    Science.gov (United States)

    Gouin, Francois L.; Almeida, Carlos; Callender, Claire L.; Robitaille, Lucie; Noad, Julian P.

    1999-04-01

    Optoelectronic (OE) switching is a promising approach for routing signals in fiber optic networks. Recently, the integration of a 4 X 4 MSM array with optical surface waveguides has been reported. This technique greatly simplifies the packaging of an OE switch. The on-chip polyimide optical waveguides perform the optical signal distribution to a matrix of MSMs which are responsible for the switching operation itself. Photoresponse bandwidths exceeding 4 GHz have been demonstrated. Another important characteristic of a switch is the switching speed since it determines the reconfiguration time. Mechanical and thermal optical waveguide switches offer switching speeds of the order of milliseconds which is sufficient for network traffic management but too slow for packet switching. We report measurements on the switching characteristics of a 4 X 4 optoelectronic switch performed in both the frequency and time domain. In the time domain, the individual crosspoints exhibit a rise time of 3 ns. However, a sizeable overshoot and ringing settles only after 35 ns. This constitutes the reconfiguration time at present. This is confirmed by measurements in the frequency domain of the electrical transmission from control line to output line. The 3-dB switching bandwidth is a few hundred megahertz. The 35 ns reconfiguration time indicates that it is already suitable for packet switching in a 10 Mb/s network. Switching speed measurements on individual MSMs suggests that modifications to the switch circuit could improve the switching time. The switch could also find application as a component in the wavelength conversion circuit of a WDM fiber optic network.

  8. Optical Packet Switching Demostrator

    DEFF Research Database (Denmark)

    Mortensen, Brian Bach; Berger, Michael Stübert

    2002-01-01

    In the IST project DAVID (data and voice integration over DWDM) work is carried out defining possible architectures of future optical packet switched networks. The feasibility of the architecture is to be verified in a demonstration set-up. This article describes the demonstrator set-up and the...

  9. Ultrafast gas switching experiments

    International Nuclear Information System (INIS)

    We describe recent experiments which studied the physics of ultrafast gas breakdown under the extreme overvoltages which occur when a high pressure gas switch is pulse charged to hundreds of kV in 1 ns or less. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes Khz at > 100 kV/m E field

  10. Language Switching and Language Competition

    Science.gov (United States)

    Macizo, Pedro; Bajo, Teresa; Paolieri, Daniela

    2012-01-01

    This study examined the asymmetrical language switching cost in a word reading task (Experiment 1) and in a categorization task (Experiment 2 and 3). In Experiment 1, Spanish-English bilinguals named words in first language (L1) and second language (L2) in a switching paradigm. They were slower to switch from their weaker L2 to their more dominant…

  11. Job Switching and Wage Growth

    OpenAIRE

    Faberman, R. Jason; Justiniano, Alejandro

    2015-01-01

    This article shows a remarkably strong relationship between job switching and nominal wage growth. We also find a fairly strong relationship between job switching and the cyclical component of inflation. Furthermore, job switching seems to be predictive of both wage growth and inflation.

  12. Biochemical switching device: how to turn on (off) the switch.

    Science.gov (United States)

    Okamoto, M; Sakai, T; Hayashi, K

    1989-01-01

    We previously showed with computer simulations that cyclic enzyme systems have the reliability of ON-OFF types of operation (McCulloch-Pitts' neuronic equation) and the applicability for a switching circuit in a biocomputer. The switching time was inevitably determined in accordance with the difference in amount between two inputs of the system. This characteristic is, however, a disadvantage for practical use of a switching device; we need to improve the system in order for the switching time to optionally be changed. We shall present here how to turn on (off) the switch independently of the modes of two inputs. By introducing pulse perturbation, we could optionally set up the switching time of a cyclic enzyme system (biochemical switching device). PMID:2720139

  13. Synchronization Between Two Different Switched Chaotic Systems By Switching Control

    Directory of Open Access Journals (Sweden)

    Du Li Ming

    2016-01-01

    Full Text Available This paper is concerned with the synchronization problem of two different switched chaotic systems, considering the general case that the master-slave switched chaotic systems have uncertainties. Two basic problems are considered: one is projective synchronization of switched chaotic systems under arbitrary switching; the other is projective synchronization of switched chaotic systems by design of switching when synchronization cannot achieved by using any subsystems alone. For the two problems, common Lyapunov function method and multiple Lyapunov function method are used respectively, an adaptive control scheme has been presented, some sufficient synchronization conditions are attainted, and the switching signal is designed. Finally, the numerical simulation is provide to show the effectiveness of our method.

  14. Molecular sensors and molecular logic gates

    International Nuclear Information System (INIS)

    Full text: The rapid grow of nanotechnology field extended the concept of a macroscopic device to the molecular level. Because of this reason the design and synthesis of (supra)-molecular species capable of mimicking the functions of macroscopic devices are currently of great interest. Molecular devices operate via electronic and/or nuclear rearrangements and, like macroscopic devices, need energy to operate and communicate between their elements. The energy needed to make a device work can be supplied as chemical energy, electrical energy, or light. Luminescence is one of the most useful techniques to monitor the operation of molecular-level devices. This fact determinates the synthesis of novel fluorescence compounds as a considerable and inseparable part of nanoscience development. Further miniaturization of semiconductors in electronic field reaches their limit. Therefore the design and construction of molecular systems capable of performing complex logic functions is of great scientific interest now. In semiconductor devices the logic gates work using binary logic, where the signals are encoded as 0 and 1 (low and high current). This process is executable on molecular level by several ways, but the most common are based on the optical properties of the molecule switches encoding the low and high concentrations of the input guest molecules and the output fluorescent intensities with binary 0 and 1 respectively. The first proposal to execute logic operations at the molecular level was made in 1988, but the field developed only five years later when the analogy between molecular switches and logic gates was experimentally demonstrated by de Silva. There are seven basic logic gates: AND, OR, XOR, NOT, NAND, NOR and XNOR and all of them were achieved by molecules, the fluorescence switching as well. key words: fluorescence, molecular sensors, molecular logic gates

  15. Design, Synthesis, and Dynamics of a Green Fluorescent Protein Fluorophore Mimic with an Ultrafast Switching Function.

    Science.gov (United States)

    Paolino, Marco; Gueye, Moussa; Pieri, Elisa; Manathunga, Madushanka; Fusi, Stefania; Cappelli, Andrea; Latterini, Loredana; Pannacci, Danilo; Filatov, Michael; Léonard, Jérémie; Olivucci, Massimo

    2016-08-10

    While rotary molecular switches based on neutral and cationic organic π-systems have been reported, structurally homologous anionic switches providing complementary properties have not been prepared so far. Here we report the design and preparation of a molecular switch mimicking the anionic p-HBDI chromophore of the green fluorescent protein. The investigation of the mechanism and dynamics of the E/Z switching function is carried out both computationally and experimentally. The data consistently support axial rotary motion occurring on a sub-picosecond time scale. Transient spectroscopy and trajectory simulations show that the nonadiabatic decay process occurs in the vicinity of a conical intersection (CInt) between a charge transfer state and a covalent/diradical state. Comparison of our anionic p-HBDI-like switch with the previously reported cationic N-alkyl indanylidene pyrrolinium switch mimicking visual pigments reveals that these similar systems translocate, upon vertical excitation, a similar net charge in the same axial direction. PMID:27322488

  16. Practical switching power supply design

    CERN Document Server

    Brown, Martin C

    1990-01-01

    Take the ""black magic"" out of switching power supplies with Practical Switching Power Supply Design! This is a comprehensive ""hands-on"" guide to the theory behind, and design of, PWM and resonant switching supplies. You'll find information on switching supply operation and selecting an appropriate topology for your application. There's extensive coverage of buck, boost, flyback, push-pull, half bridge, and full bridge regulator circuits. Special attention is given to semiconductors used in switching supplies. RFI/EMI reduction, grounding, testing, and safety standards are also deta

  17. Switched Matrix Accelerator

    International Nuclear Information System (INIS)

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm-wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We provide also an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392. GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high-power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium

  18. Python Switch Statement

    Directory of Open Access Journals (Sweden)

    2008-06-01

    Full Text Available The Python programming language does not have a built in switch/case control structure as found in many other high level programming languages. It is thought by some that this is a deficiency in the language, and the control structure should be added. This paper demonstrates that not only is the control structure not needed, but that the methods available in Python are more expressive than built in case statements in other high level languages.

  19. Magnetic Cellular Switches

    OpenAIRE

    Overby, Darryl R.; Alenghat, Francis J.; Montoya-Zavala, Martín; Bei, HuCheng; Oh, Philmo; Karavitis, John; Ingber, Donald E.

    2004-01-01

    This paper focuses on the development of magnetic cellular switches to enable magnetic control of intracellular functions in living mammalian cells, including receptor signal transduction and gene transcription. Our approach takes advantage of the mechanosensitivity of adenosine 3′,5′-monophosphate (cAMP) induction and downstream transcription controlled by the cAMP regulatory element (CRE) to engineer gene constructs that optically report gene expression in living cells. We activate transcri...

  20. MCT/MOSFET Switch

    Science.gov (United States)

    Rippel, Wally E.

    1990-01-01

    Metal-oxide/semiconductor-controlled thyristor (MCT) and metal-oxide/semiconductor field-effect transistor (MOSFET) connected in switching circuit to obtain better performance. Offers high utilization of silicon, low forward voltage drop during "on" period of operating cycle, fast turnon and turnoff, and large turnoff safe operating area. Includes ability to operate at high temperatures, high static blocking voltage, and ease of drive.

  1. STM-induced switching of the hydrogen molecule in naphthalocyanine

    International Nuclear Information System (INIS)

    The switching induced by the scanning tunneling microscope (STM) current of an adsorbed hydrogen molecule in the cavity of a naphthalocyanine molecule between two perpendicular orientations is studied. We regard such a system as a good candidate for a molecular size electronic logic gate since it causes a well observed change in the STM tunneling current. To investigate the switching phenomenon theoretically, a dynamical model is proposed in this study. Our suggested model is a three-level system, with the switching as a rotation induced by tunneling electrons considered as a second-order time dependent perturbation, where the electrons tunnel from the STM-tip to the naphthalocyanine molecule then to the metal substrate. The tunneled electrons will excite the hydrogen molecule rotational modes to jump over a potential barrier and then the switching will occur. To verify the model, the probability of the switching is calculated and plotted against the bias voltage at different temperatures using first-principles calculated parameters to fit fairly with experimental observations. In the light of our model and the DFT results, we explain the energy level (highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and LUMO+1 orbitals) deviations with different substrates (NaCl and RbI) and the charge density distributions of these orbitals in different cases.

  2. Thermoelectric properties of molecular nanostructures

    OpenAIRE

    Ermakov, Vladimir N.; Kruchinin, Sergei P.; Kim, Hyun Taki; Pruschke, Thomas

    2011-01-01

    We use the concept of resonant tunneling to calculate the thermopower of molecular nanosystems. It turns out that the sign of the thermovoltage under resonant tunneling conditions depends sensitively on the participating molecular orbital, and one finds a sign change when the transport channel switches from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. Comparing our results to recent experimental data obtained for a BDT molecule contacted with an STM tip, ...

  3. Bistable organic materials in optoelectrical switches: Two-electrode devices vs. organic field effect transistors

    CERN Document Server

    Sworakowski, Juliusz

    2011-01-01

    The paper presents a short overview of research into properties of organic materials and structures that could be used in optoelectrical switches, i.e., switches in which changes in electrical properties are triggered by light of appropriate wavelengths. In particular, described are the structures acting by virtue of reversible photochemical reactions occurring in photochromic molecular materials.

  4. Bistability in a Metabolic Network Underpins the De Novo Evolution of Colony Switching in Pseudomonas fluorescens

    DEFF Research Database (Denmark)

    Gallie, Jenna; Libby, Eric; Bertels, Frederic;

    2015-01-01

    central metabolism (carB) generates such a striking phenotype. We show that colony switching is underpinned by ON/OFF expression of capsules consisting of a colanic acid-like polymer. We use molecular genetics, biochemical analyses, and experimental evolution to establish that capsule switching results...

  5. Bistability in a metabolic network underpins the de novo evolution of colony switching in Pseudomonas fluorescens

    NARCIS (Netherlands)

    Gallie, J.; Libby, E.; Bertels, F.; Jendresen, C.B.; Martinussen, J.; Kilstrup, M.; Desprat, N.; Buffing, M.F.; Sauer, U.; Beaumont, H.J.E.; Rainey, P.B.

    2015-01-01

    Phenotype switching is commonly observed in nature. This prevalence has allowed the elucidation of a number of underlying molecular mechanisms. However, little is known about how phenotypic switches arise and function in their early evolutionary stages. The first opportunity to provide empirical ins

  6. Research Progress on Multimode Interference Switches

    Institute of Scientific and Technical Information of China (English)

    GAO Qing; SHENG Zhi-rui; JIANG Xiao-qing; WANG Ming-hua

    2005-01-01

    Optical switches are key components for constructing optical communication networks, so it is necessary to design optical switches and optical switch arrays with high performance and low cost. As one type of optical switches, the multimode interference(MMI) switches have received considerable attention due to their unique merits. The structures and operation principles of various types of MMI switches are introduced,and the recent progresses of MMI switches are also discussed.

  7. The economics of lamp switching

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-09-01

    The effect of switching off fluorescent lamps, in terms of electricity cost, was discussed. Fluorescent lamps are designed to burn for thousands of hours. Initially, it was believed that turning them off was not economical. However, with new fluorescent lamps available today, this no longer holds true. It was shown that as energy costs increase, it is advantageous to switch lamps off in office buildings during lunch, coffee breaks and other non-essential periods. Also, as labour and lamp costs increase it becomes even more economical to turn lamps on only when needed in some areas such as washrooms, stockrooms, etc. Inexpensive photo-electric and time-switch controls are readily available for automatic switching to eliminate the `human error` of forgetting to turn light off when they are not required. Over time, the energy saved would offset the cost of the switch controllers and the reduction in lamp life caused by repeated switching. 4 tabs., 2 figs.

  8. Circuit model of Rimfire switch

    International Nuclear Information System (INIS)

    A cascade gaps circuit model for Rimfire switch has been developed. The circuit model includes all stray capacitances and spark channel on-state conduction characteristics. It can not only describe the behavior of Rimfire switch, but also allow analysis of the time varying voltage and current at each part of the switch, describing the internal characters of the switch. PSpice was used to implement the cascade gaps circuit model and simulate a 700 kV Rimfire switch. The simulation shows that, the voltage of the whole switch will be higher than 700 kV when the laser triggered section has broken down but all cascade gaps keep dielectric, and the voltage of all gaps attenuates with high frequency oscillation. (authors)

  9. Photochromic systems as models for opto-electrical switches

    Czech Academy of Sciences Publication Activity Database

    Lutsyk, P.; Sworakowski, J.; Janus, K.; Nešpůrek, Stanislav; Kochalska, Anna

    2010-01-01

    Roč. 522, - (2010), s. 511-528. ISSN 1542-1406 R&D Projects: GA AV ČR KAN401770651 Institutional research plan: CEZ:AV0Z40500505 Keywords : charge carrier transport * molecular material * opto-electrical switch Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.543, year: 2010

  10. Experimental approaches for the study of hemoglobin switching

    Energy Technology Data Exchange (ETDEWEB)

    Stamatoyannopoulos, G.; Neinhuis, A.W.

    1985-01-01

    This book contains papers divided among the following sections: Overview; Globin Gene Structure and Function; Mutations that Influence Hb F Production; Cell Lines Useful for Analysis of Gene Expression; Globin Gene Transfer and Expression; Molecular and Cell Biology of Hematopoiesis; Cell Biology of Switching.

  11. Recent developments in switching theory

    CERN Document Server

    Mukhopadhyay, Amar

    2013-01-01

    Electrical Science Series: Recent Developments in Switching Theory covers the progress in the study of the switching theory. The book discusses the simplified proof of Post's theorem on completeness of logic primitives; the role of feedback in combinational switching circuits; and the systematic procedure for the design of Lupanov decoding networks. The text also describes the classical results on counting theorems and their application to the classification of switching functions under different notions of equivalence, including linear and affine equivalences. The development of abstract har

  12. Noise-induced coherent switch

    Institute of Scientific and Technical Information of China (English)

    YUAN ZhanJiang; ZHANG Jiadun; ZHOU TianShou

    2008-01-01

    Taking the famous genetic toggle switch as an example, we numerically investigated the effect of noise on bistability. We found that extrinsic noise resulting from stochastic fluctuations in synthesis and degradation rates and from the environmental fluctuation in gene regulatory processes can induce coherent switch, and that there is an optimal noise intensity such that the noise not only can induce this switch, but also can amplify a weak input signal. In addition, we found that the intrinsic noise introduced through the Poisson τ-leap algorithm cannot induce such a switch.

  13. Noise-induced coherent switch

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Taking the famous genetic toggle switch as an example,we numerically investigated the effect of noise on bistability.We found that extrinsic noise resulting from stochastic fluctuations in synthesis and degradation rates and from the environmental fluctuation in gene regulatory processes can induce coherent switch,and that there is an optimal noise intensity such that the noise not only can induce this switch,but also can amplify a weak input signal.In addition,we found that the intrinsic noise introduced through the Poisson τ-leap algorithm cannot induce such a switch.

  14. Neuromorphic atomic switch networks.

    Directory of Open Access Journals (Sweden)

    Audrius V Avizienis

    Full Text Available Efforts to emulate the formidable information processing capabilities of the brain through neuromorphic engineering have been bolstered by recent progress in the fabrication of nonlinear, nanoscale circuit elements that exhibit synapse-like operational characteristics. However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks. Here we demonstrate the physical realization of a self-assembled neuromorphic device which implements basic concepts of systems neuroscience through a hardware-based platform comprised of over a billion interconnected atomic-switch inorganic synapses embedded in a complex network of silver nanowires. Observations of network activation and passive harmonic generation demonstrate a collective response to input stimulus in agreement with recent theoretical predictions. Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks. These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system.

  15. Data center coolant switch

    Science.gov (United States)

    Iyengar, Madhusudan K.; Parida, Pritish R.; Schultz, Mark D.

    2015-10-06

    A data center cooling system is operated in a first mode; it has an indoor portion wherein heat is absorbed from components in the data center, and an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid (e.g., water) present in at least the outdoor heat exchanger portion of the cooling system during the first mode. The first heat transfer fluid is a relatively high performance heat transfer fluid (as compared to the second fluid), and has a first heat transfer fluid freezing point. A determination is made that an appropriate time has been reached to switch from the first mode to a second mode. Based on this determination, the outdoor heat exchanger portion of the data cooling system is switched to a second heat transfer fluid, which is a relatively low performance heat transfer fluid, as compared to the first heat transfer fluid. It has a second heat transfer fluid freezing point lower than the first heat transfer fluid freezing point, and the second heat transfer fluid freezing point is sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.

  16. Hybrid switch for resonant power converters

    Science.gov (United States)

    Lai, Jih-Sheng; Yu, Wensong

    2014-09-09

    A hybrid switch comprising two semiconductor switches connected in parallel but having different voltage drop characteristics as a function of current facilitates attainment of zero voltage switching and reduces conduction losses to complement reduction of switching losses achieved through zero voltage switching in power converters such as high-current inverters.

  17. LCT protective dump-switch tests

    International Nuclear Information System (INIS)

    Each of the six coils in the Large Coil Task (LCT) has a separate power supply, dump resistor, and switching circuit. Each switching circuit contains five switches, two of which are redundant. The three remaining switches perform separate duties in an emergency dump situation. These three switches were tested to determine their ability to meet the LCT conditions

  18. Multistable decision switches for flexible control of epigenetic differentiation.

    Directory of Open Access Journals (Sweden)

    Raúl Guantes

    2008-11-01

    Full Text Available It is now recognized that molecular circuits with positive feedback can induce two different gene expression states (bistability under the very same cellular conditions. Whether, and how, cells make use of the coexistence of a larger number of stable states (multistability is however largely unknown. Here, we first examine how autoregulation, a common attribute of genetic master regulators, facilitates multistability in two-component circuits. A systematic exploration of these modules' parameter space reveals two classes of molecular switches, involving transitions in bistable (progression switches or multistable (decision switches regimes. We demonstrate the potential of decision switches for multifaceted stimulus processing, including strength, duration, and flexible discrimination. These tasks enhance response specificity, help to store short-term memories of recent signaling events, stabilize transient gene expression, and enable stochastic fate commitment. The relevance of these circuits is further supported by biological data, because we find them in numerous developmental scenarios. Indeed, many of the presented information-processing features of decision switches could ultimately demonstrate a more flexible control of epigenetic differentiation.

  19. Understanding the conductance switching of permethyloligosilanes: A theoretical approach

    Science.gov (United States)

    Pramanik, Anup; Sarkar, Pranab

    2015-09-01

    On the basis of ab initio density functional theory coupled with non-equilibrium Green's function technique, we have presented a molecular level understanding on the stereoelectronic switching of conducting properties of oligosilane molecules. Su et al. [Nat. Chem. 7, 215-220 (2015)] demonstrated that these types of oligosilane molecules exhibit three stereoconformers which show two distinct conducting profiles. On the basis of break-junction technique, the authors show that manipulating a specific dihedral angle and thereby controlling the length of the molecular contact, it is possible to switch the conducting states minutely. However, their discussions scarce the proper energy level alignment upon which the molecule-lead tunneling amplitude depends. On the basis of electronic structure and non-equilibrium electron transport calculations, we interpret such switching behavior and thus quantify the switching parameter demonstrating how the metal-molecule contact geometry along with the electronic energy level alignment is responsible for such kind of junction process. We also provide the variation of switching parameter and the type of majority carrier with the conjugation length of the oligosilanes.

  20. A Single-Molecule Switch and Memory Element

    International Nuclear Information System (INIS)

    The mechanically controllable break-junction technique enables us to investigate charge-carrier transport through an individually contacted and addressed molecule. Using a statistical measurement and analysis approach, we acquire simultaneously current-voltage curves during the repeated formation and breaking of a molecular junction. Thereby, a reversible and controllable switching between two distinct conductive states of a single-molecule system was investigated. Voltage pulses are used to switch from a low to a high conductive ''on'' state, and, furthermore, to reset the switch again to the ''off'' state. On this single-molecule level, collective phenomena can be excluded and therefore the observed switching mechanism has a truly molecular origin. Both conductive states are stable and accessible via non-destructive reading. Combined with the ability to reset the switch, this opens the way to employ this single-molecule as a memory element which is demonstrated by repeated write-read-erase-read cycles with non-destructive read-outs

  1. Understanding the conductance switching of permethyloligosilanes: A theoretical approach

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Anup; Sarkar, Pranab, E-mail: pranab.sarkar@visva-bharati.ac.in [Department of Chemistry, Visva-Bharati University, Santiniketan 731235 (India)

    2015-09-21

    On the basis of ab initio density functional theory coupled with non-equilibrium Green’s function technique, we have presented a molecular level understanding on the stereoelectronic switching of conducting properties of oligosilane molecules. Su et al. [Nat. Chem. 7, 215–220 (2015)] demonstrated that these types of oligosilane molecules exhibit three stereoconformers which show two distinct conducting profiles. On the basis of break-junction technique, the authors show that manipulating a specific dihedral angle and thereby controlling the length of the molecular contact, it is possible to switch the conducting states minutely. However, their discussions scarce the proper energy level alignment upon which the molecule-lead tunneling amplitude depends. On the basis of electronic structure and non-equilibrium electron transport calculations, we interpret such switching behavior and thus quantify the switching parameter demonstrating how the metal-molecule contact geometry along with the electronic energy level alignment is responsible for such kind of junction process. We also provide the variation of switching parameter and the type of majority carrier with the conjugation length of the oligosilanes.

  2. Convertible resistive switching characteristics between memory switching and threshold switching in a single ferritin-based memristor.

    Science.gov (United States)

    Zhang, Chaochao; Shang, Jie; Xue, Wuhong; Tan, Hongwei; Pan, Liang; Yang, Xi; Guo, Shanshan; Hao, Jian; Liu, Gang; Li, Run-Wei

    2016-04-01

    A bio-memristor fabricated with ferritin exhibits novel resistive switching characteristics wherein memory switching and threshold switching are made steadily coexistent and inter-convertible through controlling the magnitude of compliance current presets. PMID:26967024

  3. Design and Simulation of a Soft Switched Dc Boost Converter for Switched Reluctance Motor

    OpenAIRE

    X. F. Joseph; Kumar, S. P.

    2012-01-01

    Problem statement: This study presents the design and simulation of a soft switched boost converter for a switched reluctance motor with a closed loop controller. A soft switching scheme is proposed in the converter with minimum components, which reduces the switching loss and stress across the switch so that the harmonic generation is reduced in the output. The switch used in this converter switched ON at zero current and switched OFF at zero voltage. Approach: Most of the research was done ...

  4. Task Switching: A PDP Model

    Science.gov (United States)

    Gilbert, Sam J.; Shallice, Tim

    2002-01-01

    When subjects switch between a pair of stimulus-response tasks, reaction time is slower on trial N if a different task was performed on trial N--1. We present a parallel distributed processing (PDP) model that simulates this effect when subjects switch between word reading and color naming in response to Stroop stimuli. Reaction time on "switch…

  5. Battery switch for downhole tools

    Science.gov (United States)

    Boling, Brian E.

    2010-02-23

    An electrical circuit for a downhole tool may include a battery, a load electrically connected to the battery, and at least one switch electrically connected in series with the battery and to the load. The at least one switch may be configured to close when a tool temperature exceeds a selected temperature.

  6. Switching Costs in Accounting Services

    OpenAIRE

    Fatih Koç; Nisa Kıymet Şahin

    2015-01-01

    Switching cost is defined as possible costs that customers may encounter when they want to change the firm they buy service, and an important subject in terms of accounting services. Particularly, small business entrepreneurs’ not having knowledge about accounting procedures, and sharing private information with accounting firms make switching costs more important for accounting services. Thus, the aim of this study is...

  7. Topology optimized RF MEMS switches

    DEFF Research Database (Denmark)

    Philippine, M. A.; Zareie, H.; Sigmund, Ole; Rebeiz, G. M.; Kenny, T. W.

    optimization for an RF MEM capacitive switch. Extensive experimental data confirms that the switches perform as designed by the optimizations, and that our simulation models are accurate. A subset of measurements are presented here. Broader results have been submitted in full journal format....

  8. Circuit switched optical networks

    DEFF Research Database (Denmark)

    Kloch, Allan

    2003-01-01

    Some of the most important components required for enabling optical networking are investigated through both experiments and modelling. These all-optical components are the wavelength converter, the regenerator and the space switch. When these devices become "off-the-shelf" products, optical cross......-connects can substitute the electrical nodes that today connect the installed optical fibres. This substitution will enable a massive increase in capacity since the bandwidth of the individual wavelength channels can be increased drastically when the electronic bit processing can be omitted. Furthermore, it is...... expected that the optical solution will offer an economical benefit for hight bit rate networks. This thesis begins with a discussion of the expected impact on communications systems from the rapidly growing IP traffic, which is expected to become the dominant source for traffic. IP traffic has some...

  9. Experiments in magnetic switching

    International Nuclear Information System (INIS)

    Magnetic switching offers an alternative to overcoming the rep-rate and life limitations of the spark gaps in the ETA/ATA induction accelerators. The principle has been applied for many years to radar modulators but at much lower power levels and longer pulse lengths. Comparatively recent developments in magnetic materials together with some optimal circuits have made it possible to go well beyond the state of the art. A magnetic modulator has been built which steps up and compresses a 25 kV, 5 μs pulse into a 250 kV, 50 ns pulse. A second magnetic modulator has been built and installed to replace four Blumleins and spark gaps in order to provide triggers for the complete ETA injector and accelerator. The paper outlines some practical and theoretical considerations affecting the design of the magnetic pulse generator

  10. Amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-04-01

    Nanoelectromechanical (NEM) switch is an interesting ultra-low power option which can operate in the harsh environment and can be a complementary element in complex digital circuitry. Although significant advancement is happening in this field, report on ultra-low voltage (pull-in) switch which offers high switching speed and area efficiency is yet to be made. One key challenge to achieve such characteristics is to fabricate nano-scale switches with amorphous metal so the shape and dimensional integrity are maintained to achieve the desired performance. Therefore, we report a tungsten alloy based amorphous metal with fabrication process development of laterally actuated dual gated NEM switches with 100 nm width and 200 nm air-gap to result in <5 volts of actuation voltage (Vpull-in). © 2013 IEEE.

  11. Macroscopic switches constructed through host-guest chemistry.

    Science.gov (United States)

    Sun, Yue; Ma, Junkai; Tian, Demei; Li, Haibing

    2016-03-17

    Molecular switch systems, having been extensively studied in the solution phase, have the ability to perform with good controllability and rapid-responsiveness, making them ideally suited for the design of molecular devices for drug delivery, and information or sensing functions. Inspired by a wide range of objects with visual changes, like Mimosa pudica towards external stimuli, in order to understand molecular switches well, they must be interfaced with the macroscopic world so that they can be directly realized by visual detectable changes even observed by the naked eye. This can be critical for fabricating intelligent microfluidics and laboratory-on-chip devices, that may have wide applications in the fields of biology and materials science. But to realize this objective, especially for fabricating macroscopic surface switches, unveiling host-guest weak interactions to achieve visual phenomena is still the greatest thrill. Thankfully, surface contact angles provide us with a wonderful method to further investigate the microscopic origin of the macroscopic changes. Therefore, interfacial modification becomes a paramount process. Macrocyclic compounds, encompassing an innovative concept to deal with reversible noncovalent interactions between macrocyclic hosts and suitable guests, are good candidates for surface functionalization. In this feature article, we discuss recent developments in macroscopic contact angle switches formed by different macrocyclic hosts and highlight the properties of these new functional surfaces and their potential applications. PMID:26905834

  12. Self-assembled switches based on electroactuated multiwalled nanotubes

    Science.gov (United States)

    Dujardin, E.; Derycke, V.; Goffman, M. F.; Lefèvre, R.; Bourgoin, J. P.

    2005-11-01

    A fabrication process for nanoelectromechanical systems (NEMS) based on multiwalled carbon nanotubes (CNTs) suspended across metallic trenches is described. The process is versatile and allows the production of CNT-NEMS with singly or doubly clamped nanotubes at an adjustable height above a bottom electrode. When a voltage bias is applied between the nanotube and the bottom electrode, the devices act as very efficient electrical switches. Surface functionalization of the bottom electrode with a self-assembled monolayer is implemented to improve the switching reversibility. Moreover, it opens opportunities to use these CNT-NEMS as a vertical cross-bar junction for molecular electronics studies.

  13. Supramolecular Antibiotic Switches: A Potential Strategy for Combating Drug Resistance.

    Science.gov (United States)

    Bai, Haotian; Lv, Fengting; Liu, Libing; Wang, Shu

    2016-08-01

    Bacterial infectious disease is a serious public health concern throughout the world. Pathogen drug resistance, arising from both rational use and abuse/misuse of germicides, complicates the situation. Aside from developing novel antibiotics and antimicrobial agents, molecular approaches have become another significant method to overcome the problem of pathogen drug resistance. Established supramolecular systems, the antibiotic properties of which can be switched "on" and "off" through host-guest interactions, show great potential in combating issues regarding antibiotic resistance in the long term, as indicated by several recent studies. In this Concept, recently developed strategies for antibacterial regulation are summarized and further directions for research into antibiotic switches are proposed. PMID:27312106

  14. The ion beam opening switch

    International Nuclear Information System (INIS)

    Plasma opening switches (POS's) have shown excellent characteristics in pulsed power applications. Proposed POS scaling predicts that the fastest opening time for a given conducted current should occur using a high-velocity low-density plasma as the switch medium. The ion beam opening switch (IBOS) uses a charge-neutral ion beam of 100-300 kV, ≤ 120 A/cm/sup 2/ as the switch ''plasma''. Its velocity of up to 600 cm/μs and density of -- 10/sup 12//cm/sup 3/ make this a very fast low-density plasma compared with typical 10 cm/μs and 10/sup 13//cm/sup 3/ POS plasmas. The IBOS has conducted ≥ 70 kA flowing in a parallel-plate transmission line driven by a 4-Ω pulser. IBOS opening time is load dependent, being ≤4 ns into a 15-nH load and about twice as long into a 4-Ω electron diode load. However, switch impedance is not zero during the entire conduction time, rising to ≥ 3 Ω by the time of peak current. Peak current conducted before opening does not vary linearly with either injected ion current or switch axial length. Instead, the conduction current scales with plasma density in the switch, and is nearly independent of switch area until the area is restricted to a narrow (-- 1 cm) strip. In this experimental geometry, replacing the IBOS with a standard POS gave essentially identical behavior, except first, an order of magnitude less injected flux was required to conduct a given current with the POS than with IBOS, corresponding to similar injected plasma densities for the two types of switches; second, clear evidence of J X B motion of the POS plasma was seen, while none was evident with IBOS

  15. The Allosteric Switching Mechanism in Bacteriophage MS2

    CERN Document Server

    Perkett, Matthew R

    2015-01-01

    In this article we use all-atom simulations to elucidate the mechanisms underlying conformational switching and allostery within the coat protein of the bacteriophage MS2. Assembly of most icosahedral virus capsids requires that the capsid protein adopt different conformations at precise locations within the capsid. It has been shown that a 19 nucleotide stem loop (TR) from the MS2 genome acts as an allosteric effector, guiding conformational switching of the coat protein during capsid assembly. Since the principal conformational changes occur far from the TR binding site, it is important to understand the molecular mechanism underlying this allosteric communication. To this end, we use all-atom simulations with explicit water combined with a path sampling technique to sample the MS2 coat protein conformational transition, in the presence and absence of TR-binding. The calculations find that TR binding strongly alters the transition free energy profile, leading to a switch in the favored conformation. We disc...

  16. Electrically switched ion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Lilga, M.A. [Pacific Northwest National Lab., Richland, WA (United States); Schwartz, D.T.; Genders, D.

    1997-10-01

    A variety of waste types containing radioactive {sup 137}Cs are found throughout the DOE complex. These waste types include water in reactor cooling basins, radioactive high-level waste (HLW) in underground storage tanks, and groundwater. Safety and regulatory requirements and economics require the removal of radiocesium before these wastes can be permanently disposed of. Electrically Switched Ion Exchange (ESIX) is an approach for radioactive cesium separation that combines IX and electrochemistry to provide a selective, reversible, and economic separation method that also produces little or no secondary waste. In the ESIX process, an electroactive IX film is deposited electrochemically onto a high-surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. For cesium, the electroactive films under investigation are ferrocyanides, which are well known to have high selectivities for cesium in concentrated sodium solutions. When a cathode potential is applied to the film, Fe{sup +3} is reduced to the Fe{sup +2} state, and a cation must be intercalated into the film to maintain charge neutrality (i.e., Cs{sup +} is loaded). Conversely, if an anodic potential is applied, a cation must be released from the film (i.e., Cs{sup +} is unloaded). Therefore, to load the film with cesium, the film is simply reduced; to unload cesium, the film is oxidized.

  17. Wide Bandgap Extrinsic Photoconductive Switches

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, James S. [State Univ. of New York (SUNY), Plattsburgh, NY (United States); Univ. of California, Davis, CA (United States)

    2012-01-20

    Photoconductive semiconductor switches (PCSS) have been investigated since the late 1970s. Some devices have been developed that withstand tens of kilovolts and others that switch hundreds of amperes. However, no single device has been developed that can reliably withstand both high voltage and switch high current. Yet, photoconductive switches still hold the promise of reliable high voltage and high current operation with subnanosecond risetimes. Particularly since good quality, bulk, single crystal, wide bandgap semiconductor materials have recently become available. In this chapter we will review the basic operation of PCSS devices, status of PCSS devices and properties of the wide bandgap semiconductors 4H-SiC, 6H-SiC and 2H-GaN.

  18. Industry switching in developing countries

    DEFF Research Database (Denmark)

    Newman, Carol; Rand, John; Tarp, Finn

    2013-01-01

    Firm turnover (i.e., firm entry and exit) is a well-recognized source of sector-level productivity growth. In contrast, the role and importance of firms that switch activities from one sector to another is not well understood. Firm switchers are likely to be unique, differing from both newly esta...... of switching merits attention in the future design of firm surveys across developing countries and in associated analytical studies....... established entrants and exiting firms that are closing down operations. In this study, we develop an empirical model that examines switching behavior using data from Vietnamese manufacturing firms during the 2001–2008 period. The diagnostic shows that switching firms exhibit different characteristics and...

  19. Electron collisions in gas switches

    International Nuclear Information System (INIS)

    Many technologies rely on the conduction/insulation properties of gaseous matter for their successful operation. Many others (e.g., pulsed power technologies) rely on the rapid change (switching or modulation) of the properties of gaseous matter from an insulator to a conductor and vice versa. Studies of electron collision processes in gases aided the development of pulsed power gas switches, and in this paper we shall briefly illustrate the kind of knowledge on electron collision processes which is needed to optimize the performance of such switching devices. To this end, we shall refer to three types of gas switches: spark gap closing, self-sustained diffuse discharge closing, and externally-sustained diffuse discharge opening. 24 refs., 15 figs., 2 tabs

  20. Product choice and product switching

    OpenAIRE

    Andrew B. Bernard; Redding, Stephen; Peter K. Schott

    2003-01-01

    This paper develops a model of endogenous product selection by firms. The theory is motivated by new evidence we present on the importance of product switching by U.S. manufacturers. Two-thirds of continuing firms change their product mix every five years, and product switches involve more than 40% of firm output and almost half of existing products. The theoretical model incorporates heterogeneous firms, heterogeneous products, and ongoing entry and exit. In equilibrium, firm productivity is...

  1. Microwatt Switched Capacitor Circuit Design

    OpenAIRE

    Vittoz, E.

    1982-01-01

    The micropower CMOS implementation of the three basic components of switched capacitor circuits is discussed. Switches must be carefully designed to allow low voltage operation and compensation of clock feed-through by dummy transistors. Matched capacitors can be implemented in single polysilicon technologies primarily designed for digital micropower circuits. Excellent micropower amplifiers are realized by using simple one-stage circuits which take advantage of the special behaviour of MOS t...

  2. Statistical switching kinetics in ferroelectrics

    OpenAIRE

    Lou, X. J.

    2008-01-01

    By assuming a more realistic nucleation and polarization reversal scenario we build a new statistical switching model for ferroelectrics, which is different from either the Kolmogorov-Avrami-Ishibashi (KAI) model or the Nucleation-Limited-Switching (NLS) model. After incorporating a time-dependent depolarization field this model gives a good description about the retardation behavior in polycrystalline thin films at medium or low fields, which can not be described by the traditional KAI model...

  3. Superannuation: Switching and Roulette Wheels

    OpenAIRE

    Michael E. Drew

    2007-01-01

    The introduction of choice has resulted in Australia’s superannuation system providing unprecedented flexibility (through increased investment options and the timing choices) for members to optimise their expected benefits. This paper examines the impact of switching between investment options using a normalised ranked return or “roulette wheel” approach developed by Bauer and Dahlquist (2001) for the Australian setting. The paper tests various switching strategies for both single-sector and ...

  4. Working Memory Costs of Task Switching

    Science.gov (United States)

    Liefooghe, Baptist; Barrouillet, Pierre; Vandierendonck, Andre; Camos, Valerie

    2008-01-01

    Although many accounts of task switching emphasize the importance of working memory as a substantial source of the switch cost, there is a lack of evidence demonstrating that task switching actually places additional demands on working memory. The present study addressed this issue by implementing task switching in continuous complex span tasks…

  5. Magnetic-fluid-based smart centrifugal switch

    International Nuclear Information System (INIS)

    A new type of centrifugal switch, which we call 'smart centrifugal switch' is designed and developed utilizing the novel properties of magnetic fluid. No mechanical movement is involved in the sensing and switching operations of this centrifugal switch and both these operations are achieved in a smart way. The performance of the switch is studied. This switch has several important advantages over conventional centrifugal switches like smart and non-contact type operation, sparkless and hence explosion proof working and inertia-less simple structure

  6. Functionalized molecules studied by STM: motion, switching and reactivity

    International Nuclear Information System (INIS)

    Functionalized molecules represent the central issue of molecular nanotechnology. Scanning tunnelling microscopy (STM) is a powerful method to investigate such molecules, because it allows us to image them with sub-molecular resolution when adsorbed on a surface and can be used at the same time as a tool to manipulate single molecules in a controlled way. Such studies permit deep insight into the conformational, mechanical and electronic structure and thus functionalities of the molecules. In this review, recent experiments on specially designed molecules, acting as model systems for molecular nanotechnology, are reviewed. The presented studies focus on key functionalities: lateral rolling and hopping motion on a supporting surface, the switching behaviour of azobenzene derivatives by using the STM tip and the controlled reactivity of molecular side groups, which enable the formation of covalently bound molecular nanoarchitectures. (topical review)

  7. Comparative Study of Hard Switching and Soft Switching Boost Converter Fed from a PV Source

    Directory of Open Access Journals (Sweden)

    B. Angeline Jerusha, S. Anu Vadhana, A. Arrul Dhana Mathy, R. Ramaprabha

    2013-09-01

    Full Text Available This paper presents a comparative study of hard switching and soft switching boost converter for interfacing photovoltaic (PV systems. This paper mainly focuses on the minimization of switching loss by adopting soft switching technology when compared to hard switching.

  8. Fluctuation-induced switching and the switching path distribution.

    Science.gov (United States)

    Dykman, Mark

    2009-03-01

    Fluctuation-induced switching is at the root of diverse phenomena currently studied in Josephson junctions, nano-mechanical systems, nano-magnets, and optically trapped atoms. In a fluctuation leading to switching the system must overcome an effective barrier, making switching events rare, for low fluctuation intensity. We will provide an overview of the methods of finding the switching barrier for systems away from thermal equilibrium. Generic features of the barrier, such as scaling with the system parameters, will be discussed. We will also discuss the motion of the system in switching and the ways of controlling it. Two major classes of systems will be considered: dynamical systems, where fluctuations are induced by noise, and birth-death systems. Even though the motion during switching is random, the paths followed in switching form a narrow tube in phase space of the system centered at the most probable path. The paths distribution is generally Gaussian and has specific features, which have been seen in the experiment [1]. Finding the most probable path itself can be reduced to solving a problem of Hamiltonian dynamics of an auxiliary noise-free system. The solution also gives the switching barrier. The barrier can be found explicitly close to parameter values where the number of stable states of the system changes and the dynamics is controlled by a slow variable. The scaling of the barrier height depends on the type of the corresponding bifurcation. We show that, both for birth-death and for Gaussian noise driven systems, the presence of even weak non-Gaussian noise can strongly modify the switching rate. The effect is described in a simple explicit form [2,3]. Weak deviations of the noise statistics from Gaussian can be sensitively detected using balanced dynamical bridge, where this deviation makes the populations of coexisting stable states different from each other; a realization of such a bridge will be discussed. We will also discuss the sharp

  9. Experimental Realization of an NMR Quantum Switch

    OpenAIRE

    Tsai, I. M.; Kuo, S. Y.; Huang, S. L.; Lin, Y. C.; Chen, T. T.

    2004-01-01

    In this paper, we report an experimental realization of quantum switch using nuclear spins and magnetic resonant pulses. The nuclear spins of H and C in carbon-13 labelled chloroform are used to carry the information, then nuclear magnetic resonance pulses are applied to perform either bypass or cross function to achieve the switching. Compared with a traditional space or time domain switch, this switching architecture is much more scalable, therefore a high throughput switching device can be...

  10. Stability of Markov regenerative switched linear systems

    OpenAIRE

    Ogura, Masaki; Preciado, Victor M.

    2015-01-01

    In this paper, we give a necessary and sufficient condition for mean stability of switched linear systems having a Markov regenerative process as its switching signal. This class of switched linear systems, which we call Markov regenerative switched linear systems, contains Markov jump linear systems and semi-Markov jump linear systems as special cases. We show that a Markov regenerative switched linear system is $m$th mean stable if and only if a particular matrix is Schur stable, under the ...

  11. Principles of broadband switching and networking

    CERN Document Server

    Liew, Soung C

    2010-01-01

    An authoritative introduction to the roles of switching and transmission in broadband integrated services networks Principles of Broadband Switching and Networking explains the design and analysis of switch architectures suitable for broadband integrated services networks, emphasizing packet-switched interconnection networks with distributed routing algorithms. The text examines the mathematical properties of these networks, rather than specific implementation technologies. Although the pedagogical explanations in this book are in the context of switches, many of the fundamenta

  12. Ultrafast Surface Plasmonic Switch in Non-Plasmonic Metals

    OpenAIRE

    Bévillon, E.; Colombier, J. P.; Recoules, V.; Zhang, H.; Li, C.; Stoian, R

    2015-01-01

    We demonstrate that ultrafast carrier excitation can drastically affect electronic structures and induce brief surface plasmonic response in non-plasmonic metals, potentially creating a plasmonic switch. Using first-principles molecular dynamics and Kubo-Greenwood formalism for laser-excited tungsten we show that carrier heating mobilizes d electrons into collective inter and intraband transitions leading to a sign flip in the imaginary optical conductivity, activating plasmonic properties fo...

  13. Electro-optical switching by liquid-crystal controlled metasurfaces.

    Science.gov (United States)

    Decker, Manuel; Kremers, Christian; Minovich, Alexander; Staude, Isabelle; Miroshnichenko, Andrey E; Chigrin, Dmitry; Neshev, Dragomir N; Jagadish, Chennupati; Kivshar, Yuri S

    2013-04-01

    We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-crystal reorientation. PMID:23571978

  14. Electro-optical switching by liquid-crystal controlled metasurfaces

    OpenAIRE

    Decker, Manuel; Kremers, Christian; Minovich, Alexander; Staude, Isabelle; Miroshnichenko, Andrey E.; Chigrin, Dmitry; Neshev, Dragomir N.; Jagadish, Chennupati; Kivshar, Yuri S.

    2013-01-01

    We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-cry...

  15. Electro-optical switching by liquid-crystal controlled metasurfaces

    CERN Document Server

    Decker, Manuel; Minovich, Alexander; Staude, Isabelle; Miroshnichenko, Andrey E; Chigrin, Dmitry; Neshev, Dragomir N; Jagadish, Chennupati; Kivshar, Yuri S

    2013-01-01

    We study the optical response of a metamaterial surface created by a lattice of split-ring resonators covered with a nematic liquid crystal and demonstrate millisecond timescale switching between electric and magnetic resonances of the metasurface. This is achieved due to a high sensitivity of liquid-crystal molecular reorientation to the symmetry of the metasurface as well as to the presence of a bias electric field. Our experiments are complemented by numerical simulations of the liquid-crystal reorientation.

  16. Improvement on Switching Characteristics and Switching Losses of IGBT by ZVS—PWM①

    Institute of Scientific and Technical Information of China (English)

    ZHANGChunjiang; GUHerong; 等

    1997-01-01

    The principle of ZVS-PWM inverting circuit is first described by means of inverting welder supply.The contrastive study is made on switching characteristics and switching losses of IGBT between ZVS-PWM and hard-switching.

  17. Wide Bandgap Extrinsic Photoconductive Switches

    Science.gov (United States)

    Sullivan, James Stephen

    Wide Bandgap Extrinsic Photoconductive Switches Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6H-SiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators. The successful development of a vanadium compensated, 6H-SiC extrinsic photoconductive switch for use as a closing switch for compact accelerator applications was realized by improvements made to the vanadium, nitrogen and boron impurity densities. The changes made to the impurity densities were based on the physical intuition outlined and simple rate equation models. The final 6H-SiC impurity 'recipe' calls for vanadium, nitrogen and boron densities of 2.5 e17 cm-3, 1.25e17 cm-3 and ≤ 1e16 cm-3, respectively. This recipe was originally developed to maximize the quantum efficiency of the vanadium compensated 6H-SiC, while maintaining a thermally stable semi-insulating material. The rate equation models indicate that, besides increasing the quantum efficiency, the impurity recipe should be expected to also increase the carrier recombination time. Three generations of 6H-SiC materials were tested. The

  18. IGBT: A solid state switch

    International Nuclear Information System (INIS)

    A Copper Vapor Laser Power Supply has been designed using a solid state switch consisting in eighteen Isolated Gate Bipolar Transistors (IGBT), 1,200 volts, 400 Amps, each, in parallel. This paper presents the Isolated Gate Bipolar Transistor (IGBTs) replaced in the Power Electronic components evolution, and describes the IGBT conduction mechanism, presents the parallel association of IGBTs, and studies the application of these components to a Copper Vapor Laser Power Supply. The storage capacitor voltage is 820 Volts, the peak current of the solid state switch is 17,000 Amps. The switch is connected on the primary of a step-up transformer, followed by a magnetic modulator. The reset of the magnetic modulator is provided by part of the laser reflected energy with a patented circuit. The charging circuit is a resonant circuit with a charge controlled by an IGBT switch. When the switch is open, the inductance energy is free-wheeled by an additional winding and does not extend the charging phase of the storage capacitor. The design allows the storage capacitor voltage to be very well regulated. This circuit is also patented. The electric pulse in the laser has 30,000 Volt peak voltage, 2,000 Amp peak current, and is 200 nanoseconds long, for a 200 Watt optical power Copper Vapor Laser

  19. IGBT: a solid state switch

    International Nuclear Information System (INIS)

    A Copper Vapour Laser Power Supply has been designed using a solid state switch consisting in eighteen Isolated Gate Bipolar Transistors (IGBT), -1200 volts, 400 Amps, each-in parallel. This paper presents the Isolated Gate Bipolar Transistor (IGBTs) replaced in the Power Electronic components evolution, and describes the IGBT conduction mechanism, presents the parallel association of IGBTs, and studies the application of these components to a Copper Vapour Laser Power Supply. The storage capacitor voltage is 820 volts, the peak current of the solid state switch is 17.000 Amps. The switch is connected on the primary of a step-up transformer, followed by a magnetic modulator. The reset of the magnetic modulator is provided by part of the laser reflected energy with a patented circuit. The charging circuit is a resonant circuit with a charge controlled by an IGBT switch. When the switch is open, the inductance energy is free-wheeled by an additional winding and does not extend the charging phase of the storage capacitor. The design allows the storage capacitor voltage to be very well regulated. This circuit is also patented. The electric pulse in the laser has 30.000 Volt peak voltage, 2000 Amp peak current, and is 200 nanoseconds long, for a 200 Watt optical power Copper Vapour Laser

  20. Current-induced switching of PTCDA on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Neucheva, Olga; Weiss, Christian; Temirov, Ruslan; Tautz, Frank Stefan [Institut fuer Bio- und Nanosysteme (IBN-3), Forschungszentrum Juelich, 52425 Juelich (Germany); JARA-Fundamental of Future Information Technology, Forschungszentrum Juelich, 52425 Juelich (Germany)

    2009-07-01

    A low temperature scanning tunneling microscope (LT-STM) has been used to investigate electron transport through a single PTCDA molecule on Ag(111). Under certain conditions, one of the carboxylic oxygen atoms of the PTCDA molecule establishes a chemical bond with the STM tip, forming a covalently bound single molecular junction. In this contribution, we investigate the process of contact formation as a function of parameters such as distance, bias voltage and electrical current through the molecular junction. In a narrow distance and voltage interval, bistable switching of the oxygen atom between a high- and low-conductance state is observed. The implications of this observation are discussed.

  1. EMT and MET as paradigms for cell fate switching

    Institute of Scientific and Technical Information of China (English)

    Jiekai Chen; Qingkai Han; Duanqing Pei

    2012-01-01

    Cell fate determination is a major unsolved problem in cell and developmental biology,The discovery of reprogramming by pluripotent factors offers a rational system to investigate the molecular mechanisms associated with cell fate decisions.The idea that reprogramming of fibroblasts starts with a mesenchymal-epithelial transition (MET) suggests that the process is perhaps a reversal of epithelial to mesenchymal transition (EMT) found frequently during early embryogenesis,As such,we believe that investigations into MET-EMT may yield detailed molecular insights into cell fate decisions,not only for the switching between epithelial and mesenchymal cells,but also other cell types.

  2. Packet switching in 1990's

    Science.gov (United States)

    Rybczynski, A.

    The author assesses wide-area networking end-user needs as they evolve into the 1990s. He then turns to the network operator environment, both public and private, by examining service evolution trends. The author concludes with an assessment of how packet switching services and technologies are evolving to continue to match the identified market requirements, with specific emphasis on Northern Telecom's DPN Data Networking System. Key evolving DPN capabilities include the introduction of the high-end DPN100 30-kb/s switch, a variety of access options including ISDN (integrated services digital network) packet mode services, higher throughput virtual circuits, megabit trunking for improved network throughput and end-user transit delay, and SNA session switching, the latter being an example of adding value to packet networking through communication processing.

  3. Easy axis switching in magnetite

    International Nuclear Information System (INIS)

    The easy magnetic axis switching in magnetite is investigated. Magnetization data confirmed activation character of the process with activation energy of the same order as that of the Verwey transition, suggesting common origin. On the other hand this activation energy rises with pressure (up to 1.2GPa), unlike TV. The axis switching is clearly reflected in field dependence of resistivity and the direct structural data showed that it is simultaneous with the reorganization of structure. Thus, control of the structure can be possible with the application of magnetic field, as in shape memory materials. Finally, NMR showed that all, possibly decoupled entities: lattice distortion and charge and orbital orderings, change simultaneously while the axis switching occurs.

  4. PROMOTION, SWITCHING BARRIERS, AND LOYALTY

    Directory of Open Access Journals (Sweden)

    Gu-Shin Tung

    2011-06-01

    Full Text Available This paper investigates the causal relationships among promotion effects, switching barriers, and loyalty in the department stores. The relationship between switching barriers and loyalty reveals partially the same results as the switching barriers theory of Jones et al. (2000. The reasons arise from “too often” and “too similar” sales promotion programs of competitive department stores in Taiwan, leading the promotion effects to not contribute to the attractiveness of competitors. The promotion effects have a positive and significant influence on loyalty, which is consistent with the prior literature. Promotion effects are also the most important weight to loyalty in our tested model but it reveals a seeming loyalty, because the loyalty depends on the reward of promotion. The negative relationship between promotion effects and attractiveness of alternative supports the promotion effects, which can lower the attractiveness of competitors, but these similar promotion plans are not attributed to interpersonal relationships.

  5. Conformational switching of porphyrin derivatives on Au(111) by heating and STM manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Mielke, Johannes; Grill, Leonhard [Institut fuer Experimentalphysik, Freie Universitaet Berlin (Germany); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Dyer, Matthew; Persson, Mats [Department of Chemistry, University of Liverpool (United Kingdom); Hecht, Stefan [Institut fuer Chemie, Humboldt-Universitaet Berlin (Germany); Martinez-Blanco, Jesus; Horn, Karsten [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany)

    2010-07-01

    Molecular switches, which exhibit at least two stable states with characteristic properties, could play an important role in future applications of molecular electronics for the control of the conductance or the implementation of logic functions. Although such molecules have been investigated intensely in solution, the knowledge about their switching properties when being adsorbed on a solid surface is still scarce. We have studied functionalised porphyrin molecules on a Au(111) surface at different temperatures. In STM images, two stable conformations can be distinguished by their characteristic appearance. When applying voltage pulses with the STM tip to single molecules at low temperatures (around 7 K), it is possible to switch the molecules reversibly from one conformation to the other, whereas the voltage thresholds turn out to be characteristic. On the other hand, thermal switching is observed at elevated temperatures of around 300 K. The high number of switching events in the regime of thermal switching can be used to gain detailed insight in the dependence of the switching process on the atomic-scale environment of the molecule.

  6. Enhanced resistive switching effect in Ag nanoparticle embedded BaTiO3 thin films

    International Nuclear Information System (INIS)

    Ag nanoparticle (NP) embedded BaTiO3 (BTO) thin films on SrRuO3-coated SrTiO3 (STO) substrates are prepared by the integrated nanocluster beam deposition and laser-molecular beam epitaxy. Enhanced resistive switching, up to an ON/OFF ration of 104, has been achieved at low switching voltage (less than 1 V) without a forming voltage. These characteristics make such nanocomposite film very promising for application of low voltage non-volatile random access memory. The enhanced resistive switching effect may be attributed to the charge storage effect of the Ag nanoparticles and easy formation of Ag filament inside the BTO film

  7. What makes the lac-pathway switch: identifying the fluctuations that trigger phenotype switching in gene regulatory systems.

    Science.gov (United States)

    Bhogale, Prasanna M; Sorg, Robin A; Veening, Jan-Willem; Berg, Johannes

    2014-10-01

    Multistable gene regulatory systems sustain different levels of gene expression under identical external conditions. Such multistability is used to encode phenotypic states in processes including nutrient uptake and persistence in bacteria, fate selection in viral infection, cell-cycle control and development. Stochastic switching between different phenotypes can occur as the result of random fluctuations in molecular copy numbers of mRNA and proteins arising in transcription, translation, transport and binding. However, which component of a pathway triggers such a transition is generally not known. By linking single-cell experiments on the lactose-uptake pathway in E. coli to molecular simulations, we devise a general method to pinpoint the particular fluctuation driving phenotype switching and apply this method to the transition between the uninduced and induced states of the lac-genes. We find that the transition to the induced state is not caused only by the single event of lac-repressor unbinding, but depends crucially on the time period over which the repressor remains unbound from the lac-operon. We confirm this notion in strains with a high expression level of the lac-repressor (leading to shorter periods over which the lac-operon remains unbound), which show a reduced switching rate. Our techniques apply to multistable gene regulatory systems in general and allow to identify the molecular mechanisms behind stochastic transitions in gene regulatory circuits. PMID:25245949

  8. Topology optimized RF MEMS switches

    DEFF Research Database (Denmark)

    Philippine, M. A.; Zareie, H.; Sigmund, Ole;

    2013-01-01

    Topology optimization is a rigorous and powerful method that should become a standard MEMS design tool - it can produce unique and non-intuitive designs that meet complex objectives and can dramatically improve the performance and reliability of MEMS devices. We present successful uses of topology...... optimization for an RF MEM capacitive switch. Extensive experimental data confirms that the switches perform as designed by the optimizations, and that our simulation models are accurate. A subset of measurements are presented here. Broader results have been submitted in full journal format....

  9. Statistical switching kinetics in ferroelectrics

    CERN Document Server

    Lou, X J

    2008-01-01

    By assuming a more realistic nucleation and polarization reversal scenario we build a new statistical switching model for ferroelectrics, which is different from either the Kolmogorov-Avrami-Ishibashi (KAI) model or the Nucleation-Limited-Switching (NLS) model. After incorporating a time-dependent depolarization field this model gives a good description about the retardation behavior in polycrystalline thin films at medium or low fields, which can not be described by the traditional KAI model. This model predicts correctly n=1 for polycrystalline thin films at high Eappl or ceramic bulks in the ideal case.

  10. STABILITY OF SWITCHED POLYNOMIAL SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Zhiqiang LI; Yupeng QIAO; Hongsheng QI; Daizhan CHENG

    2008-01-01

    This paper investigates the stability of (switched) polynomial systems. Using semi-tensor product of matrices, the paper develops two tools for testing the stability of a (switched) polynomial system. One is to convert a product of multi-variable polynomials into a canonical form, and the other is an easily verifiable sufficient condition to justify whether a multi-variable polynomial is positive definite. Using these two tools, the authors construct a polynomial function as a candidate Lyapunov function and via testing its derivative the authors provide some sufficient conditions for the global stability of polynomial systems.

  11. CMOS integrated switching power converters

    CERN Document Server

    Villar-Pique, Gerard

    2011-01-01

    This book describes the structured design and optimization of efficient, energy processing integrated circuits. The approach is multidisciplinary, covering the monolithic integration of IC design techniques, power electronics and control theory. In particular, this book enables readers to conceive, synthesize, design and implement integrated circuits with high-density high-efficiency on-chip switching power regulators. Topics covered encompass the structured design of the on-chip power supply, efficiency optimization, IC-compatible power inductors and capacitors, power MOSFET switches and effi

  12. Switching in electrical transmission and distribution systems

    CERN Document Server

    Smeets, René; Kapetanovic, Mirsad; Peelo, David F; Janssen, Anton

    2014-01-01

    Switching in Electrical Transmission and Distribution Systems presents the issues and technological solutions associated with switching in power systems, from medium to ultra-high voltage. The book systematically discusses the electrical aspects of switching, details the way load and fault currents are interrupted, the impact of fault currents, and compares switching equipment in particular circuit-breakers. The authors also explain all examples of practical switching phenomena by examining real measurements from switching tests. Other highlights include: up to date commentary on new develo

  13. One-cycle control of switching converters

    OpenAIRE

    Smedley, Keyue M.; Ćuk, Slobodan

    1995-01-01

    A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-cycle control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects swit...

  14. Lineage tracing of human B cells reveals the in vivo landscape of human antibody class switching

    Science.gov (United States)

    Horns, Felix; Vollmers, Christopher; Croote, Derek; Mackey, Sally F; Swan, Gary E; Dekker, Cornelia L; Davis, Mark M; Quake, Stephen R

    2016-01-01

    Antibody class switching is a feature of the adaptive immune system which enables diversification of the effector properties of antibodies. Even though class switching is essential for mounting a protective response to pathogens, the in vivo patterns and lineage characteristics of antibody class switching have remained uncharacterized in living humans. Here we comprehensively measured the landscape of antibody class switching in human adult twins using antibody repertoire sequencing. The map identifies how antibodies of every class are created and delineates a two-tiered hierarchy of class switch pathways. Using somatic hypermutations as a molecular clock, we discovered that closely related B cells often switch to the same class, but lose coherence as somatic mutations accumulate. Such correlations between closely related cells exist when purified B cells class switch in vitro, suggesting that class switch recombination is directed toward specific isotypes by a cell-autonomous imprinted state. DOI: http://dx.doi.org/10.7554/eLife.16578.001 PMID:27481325

  15. Multiserver switch scheduling for high speed optical switches

    Science.gov (United States)

    Golla, Prasad; Blanton, John; Damm, Gerard

    2003-10-01

    A switch matrix implemented as an optical crossbar using semiconductor optical amplifiers is able to accommodate extreme concentrations of data traffic. Due to the need to reduce optical guard band overhead it is beneficial to switch fixed size bursts of data cells on a time slot basis. The high capacity of the optical matrix supports multiple optical ports per burst card, and the implementation of multiple queue servers per burst card helps make better use of the multiplicity of ports. Problems associated with arbitrating multiple ports and multiple servers per burst card have been resolved by extending the operation of existing iterative, single server scheduling algorithms. The multiserver arbitration time will be in proportion to the number of servers -- corresponding to the channels of DWDM link -- unless a reconciliation stage is used after each iteration when an arbiter per server is used. The reconciliation stage sets the problem of broken data dependencies between server arbitrations in this case. Further, to address the time limitations for computing the scheduling solution, parallel arbiter implementations have been developed and tested against single arbiter designs. Again, the broken dependencies between iterations of an arbitration are addressed through the use of a grant reconciliation stage. The use of multiple queue servers per burst card also resolves some of the data loss problems related to polarized traffic. Simulations of the multiple server and parallel arbiter implementations have demonstrated their efficiency compared to previous implementations. Compounded to this problem is maintaining high throughput of the switch matrix while observing data transit time limits. This involves balancing two contradictory requirements; switch or line card efficiency and data transit times. To improve efficiency it is desirable to transmit only full packets. However, to prevent loss of data due to timeout it will be necessary to transmit some incomplete

  16. Semiconductor Switching Devices. .Future Trends

    Directory of Open Access Journals (Sweden)

    S. Ahmad

    1998-01-01

    Full Text Available A variety of semiconductor devices and circuits have been successfully developed usingconduction properties of electrons and holes in a number of elemental and compound semiconductors.Carriers confinement in a potential well, formed out of a thin layer of lower band gap materialsandwitched between two layers of a higher band gap material, has been extended from one to two andthree dimensions. Resultant of two-dimensional carrier sheet, quantum wire and quantum dot havingdiscrete energy levels arising out of quantisation are being presently explored for possible device applications. A number of devices have been fabricated using resonant tunneling across a thin potentialbarrier. This has opened up several newer possibilities of using such structures for various electronicand optoelectronic devices and circuits applications as tunneling is relatively faster than conductionprocess. While looking into the interband tunneling between two quantum dots, possibility of a singleelectron switching has also been examined carefully. The idea of a single electron switching isconceptually being extended from quantl,lm dots to molecules and atoms ultimately. Simulations basedon transmission of electrons through a chain of molecules and atoms have shown that tens of THz speed and functional device density 1012 devices/mm2 are possible with such schemes. Devices basedon atom relay transistor (ART will be ultimate in its performance of switching speed. A brief onpresent-day situation followed by future proposals of fast switching devices for informationelectronics has been discussed.

  17. Intrinsic nanofilamentation in resistive switching

    KAUST Repository

    Wu, Xing

    2013-03-15

    Resistive switching materials are promising candidates for nonvolatile data storage and reconfiguration of electronic applications. Intensive studies have been carried out on sandwiched metal-insulator-metal structures to achieve high density on-chip circuitry and non-volatile memory storage. Here, we provide insight into the mechanisms that govern highly reproducible controlled resistive switching via a nanofilament by using an asymmetric metal-insulator-semiconductor structure. In-situ transmission electron microscopy is used to study in real-time the physical structure and analyze the chemical composition of the nanofilament dynamically during resistive switching. Electrical stressing using an external voltage was applied by a tungsten tip to the nanosized devices having hafnium oxide (HfO2) as the insulator layer. The formation and rupture of the nanofilaments result in up to three orders of magnitude change in the current flowing through the dielectric during the switching event. Oxygen vacancies and metal atoms from the anode constitute the chemistry of the nanofilament.

  18. Robust Stability of Switched Systems

    DEFF Research Database (Denmark)

    Sloth, Christoffer; Wisniewski, Rafael

    This paper presents a linear programming-based method for finding Lyapunov functions of switched systems with polynomial vector fields and parametric uncertainties. We propose to utilize a certificate of positivity in the Bernstein basis to find a Lyapunov function. A certificate of positivity in...

  19. Wide Bandgap Extrinsic Photoconductive Switches

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, James S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-07-03

    Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6HSiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators.

  20. Switching Costs in Accounting Services

    Directory of Open Access Journals (Sweden)

    Fatih Koç

    2015-06-01

    Full Text Available Switching cost is defined as possible costs that customers may encounter when they want to change the firm they buy service, and an important subject in terms of accounting services. Particularly, small business entrepreneurs’ not having knowledge about accounting procedures, and sharing private information with accounting firms make switching costs more important for accounting services. Thus, the aim of this study is to investigate the concept of switching costs (relational cost, procedural cost and financial cost, its determinants (perceived service quality, service importance, and service failures, and consequences (re-purchasing, and recommen ding to others. Theresearch was conducted on small business entrepreneurs in down-town of Balıkesir in Turkey. Total 405 small business entrepreneur owners were interviewed. According to results of the study, perceived service quality positively affects all dimensions of switching costs, significance of service positively affects procedural and relational costs, and service failures negatively affect procedural and relational costs. The results showed that while procedural and relational costs positively affect re-purchasing and recommending to others variables, financial cost did not have any effect on these variables.

  1. Industry Switching in Developing Countries

    DEFF Research Database (Denmark)

    Newman, Carol; Rand, John; Tarp, Finn

    as compared to entry and exit firms. They tend, inter alia, to be labour-intensive and seek out competitive opportunities in labour-intensive sectors in response to changes in the market environment. We also show that resource reallocations resulting from switching form an important component of...

  2. Multiuser switched diversity scheduling schemes

    KAUST Repository

    Shaqfeh, Mohammad

    2012-09-01

    Multiuser switched-diversity scheduling schemes were recently proposed in order to overcome the heavy feedback requirements of conventional opportunistic scheduling schemes by applying a threshold-based, distributed, and ordered scheduling mechanism. The main idea behind these schemes is that slight reduction in the prospected multiuser diversity gains is an acceptable trade-off for great savings in terms of required channel-state-information feedback messages. In this work, we characterize the achievable rate region of multiuser switched diversity systems and compare it with the rate region of full feedback multiuser diversity systems. We propose also a novel proportional fair multiuser switched-based scheduling scheme and we demonstrate that it can be optimized using a practical and distributed method to obtain the feedback thresholds. We finally demonstrate by numerical examples that switched-diversity scheduling schemes operate within 0.3 bits/sec/Hz from the ultimate network capacity of full feedback systems in Rayleigh fading conditions. © 2012 IEEE.

  3. Optimal switching using coherent control

    DEFF Research Database (Denmark)

    Kristensen, Philip Trøst; Heuck, Mikkel; Mørk, Jesper

    2013-01-01

    We introduce a general framework for the analysis of coherent control in coupled optical cavity-waveguide systems. Within this framework, we use an analytically solvable model, which is validated by independent numerical calculations, to investigate switching in a micro cavity and demonstrate that...

  4. Coherent switching of semiconductor resonator solitons

    OpenAIRE

    Taranenko, V. B.; Ahlers, F. -J.; Pierz, K.

    2002-01-01

    We demonstrate switching on and off of spatial solitons in a semiconductor microresonator by injection of light coherent with the background illumination. Evidence results that the formation of the solitons and their switching does not involve thermal processes.

  5. Ultrafast Beam Switching Using Coupled VCSELs

    Science.gov (United States)

    Ning, Cun-Zheng; Goorjian, Peter

    2001-01-01

    We propose a new approach to performing ultrafast beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The strategy is demonstrated by numerical simulation, showing a beam switching of 10 deg at 42 GHz.

  6. A Demonstration of Automatically Switched Optical Network

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We build an automatically switched optical network (ASON) testbed with four optical cross-connect nodes. Many fundamental ASON features are demonstrated, which is implemented by control protocols based on generalized multi-protocol label switching (GMPLS) framework.

  7. Digital Switching in the Quantum Domain

    CERN Document Server

    Tsai, I M

    2002-01-01

    In this paper, we present an architecture and implementation algorithm such that digital data can be switched in the quantum domain. First we define the connection digraph which can be used to describe the behavior of a switch at a given time, then we show how a connection digraph can be implemented using elementary quantum gates. The proposed mechanism supports unicasting as well as multicasting, and is strict-sense non-blocking. It can be applied to perform either circuit switching or packet switching. Compared with a traditional space or time domain switch, the proposed switching mechanism is more scalable. Assuming an n-by-n quantum switch, the space consumption grows linearly, i.e. O(n), while the time complexity is O(1) for unicasting, and O(log n) for multicasting. Based on these advantages, a high throughput switching device can be built simply by increasing the number of I/O ports.

  8. Conformational switching of modified guest chains in polymer brushes

    Science.gov (United States)

    Romeis, D.; Sommer, J.-U.

    2013-07-01

    Using a numerical quasi off-lattice self-consistent field method which describes heterogeneous chains of spherical monomers we study the case of a densely grafted polymer brush with a fraction of free chain ends being replaced by a modified end-group differing in size and solvent selectivity. We can confirm the observation from molecular dynamics simulations that upon changing the solvent conditions, a switching in location of end-groups which are bigger than monomers from a state "exposed" to the solvent (on the top of the brush) to a "hidden" state (inside the brush) takes place. Our numerical method allows a detailed study of the switching effect as a function of the relevant parameters, such as grafting density, chain length, size of end-groups and their volume fraction. We find that the switching effect is enhanced for long chains, low fractions of modified chains, and big end-groups. We consider the case of low fraction of modified chains in more detail using a test chain method. Here, we explore the optimal grafting density as a function of the size of the end-groups, where the switching is most sensitive. These values can be in the experimental range for end-groups which are at least 3-4 times bigger than the monomers. The end-groups can be realized by attaching nano-particles to the last monomer of a brush-chain.

  9. The stability of a stochastic CaMKII switch: dependence on the number of enzyme molecules and protein turnover.

    Directory of Open Access Journals (Sweden)

    Paul Miller

    2005-04-01

    Full Text Available Molecular switches have been implicated in the storage of information in biological systems. For small structures such as synapses, these switches are composed of only a few molecules and stochastic fluctuations are therefore of importance. Such fluctuations could potentially lead to spontaneous switch reset that would limit the lifetime of information storage. We have analyzed a model of the calcium/calmodulin-dependent protein kinase II (CaMKII switch implicated in long-term memory in the nervous system. The bistability of this switch arises from autocatalytic autophosphorylation of CaMKII, a reaction that is countered by a saturable phosphatase-1-mediated dephosphorylation. We sought to understand the factors that control switch stability and to determine the functional relationship between stability and the number of molecules involved. Using Monte Carlo simulations, we found that the lifetime of states of the switch increase exponentially with the number of CaMKII holoenzymes. Switch stability requires a balance between the kinase and phosphatase rates, and the kinase rate must remain high relative to the rate of protein turnover. Thus, a critical limit on switch stability is set by the observed turnover rate (one per 30 h on average. Our computational results show that, depending on the timescale of fluctuations in enzyme numbers, for a switch composed of about 15 CaMKII holoenzymes, the stable persistent activation can span from a few years to a human lifetime.

  10. The Stability of a Stochastic CaMKII Switch: Dependence on the Number of Enzyme Molecules and Protein Turnover

    Directory of Open Access Journals (Sweden)

    Miller Paul

    2005-01-01

    Full Text Available Molecular switches have been implicated in the storage of information in biological systems. For small structures such as synapses, these switches are composed of only a few molecules and stochastic fluctuations are therefore of importance. Such fluctuations could potentially lead to spontaneous switch reset that would limit the lifetime of information storage. We have analyzed a model of the calcium/calmodulin-dependent protein kinase II (CaMKII switch implicated in long-term memory in the nervous system. The bistability of this switch arises from autocatalytic autophosphorylation of CaMKII, a reaction that is countered by a saturable phosphatase-1-mediated dephosphorylation. We sought to understand the factors that control switch stability and to determine the functional relationship between stability and the number of molecules involved. Using Monte Carlo simulations, we found that the lifetime of states of the switch increase exponentially with the number of CaMKII holoenzymes. Switch stability requires a balance between the kinase and phosphatase rates, and the kinase rate must remain high relative to the rate of protein turnover. Thus, a critical limit on switch stability is set by the observed turnover rate (one per 30 h on average. Our computational results show that, depending on the timescale of fluctuations in enzyme numbers, for a switch composed of about 15 CaMKII holoenzymes, the stable persistent activation can span from a few years to a human lifetime.

  11. Spark gap switch with spiral gas flow

    Science.gov (United States)

    Brucker, John P.

    1989-01-01

    A spark gap switch having a contaminate removal system using an injected gas. An annular plate concentric with an electrode of the switch defines flow paths for the injected gas which form a strong spiral flow of the gas in the housing which is effective to remove contaminates from the switch surfaces. The gas along with the contaminates is exhausted from the housing through one of the ends of the switch.

  12. Pinning Synchronization of Switched Complex Dynamical Networks

    OpenAIRE

    Liming Du; Feng Qiao; Fengying Wang

    2015-01-01

    Network topology and node dynamics play a key role in forming synchronization of complex networks. Unfortunately there is no effective synchronization criterion for pinning synchronization of complex dynamical networks with switching topology. In this paper, pinning synchronization of complex dynamical networks with switching topology is studied. Two basic problems are considered: one is pinning synchronization of switched complex networks under arbitrary switching; the other is pinning synch...

  13. Degree of Conversational Code-Switching Enhances Verbal Task Switching in Cantonese-English Bilinguals

    Science.gov (United States)

    Yim, Odilia; Bialystok, Ellen

    2012-01-01

    The study examined individual differences in code-switching to determine the relationship between code-switching frequency and performance in verbal and non-verbal task switching. Seventy-eight Cantonese-English bilinguals completed a semi-structured conversation to quantify natural code-switching, a verbal fluency task requiring language…

  14. A gain-coefficient switched Alexandrite laser

    OpenAIRE

    Lee, Chris J.; van der Slot, Peter J. M.; Boller, Klaus-J.

    2012-01-01

    We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.

  15. A gain-coefficient switched Alexandrite laser

    NARCIS (Netherlands)

    Lee, C. J.; van der Slot, P. J. M.; Boller, K. J.

    2013-01-01

    We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ

  16. The increased importance of sector switching

    DEFF Research Database (Denmark)

    Frederiksen, Anders; Hansen, Jesper Rosenberg

    2014-01-01

    Sector switching is an important phenomenon that casts light on public–private differences. Yet our knowledge about its prevalence and trends is limited. We study sector switching using unique Danish register-based employer–employee data covering more than 25 years. We find that sector switching...

  17. A Bilingual Advantage in Task Switching

    Science.gov (United States)

    Prior, Anat; MacWhinney, Brian

    2010-01-01

    This study investigated the possibility that lifelong bilingualism may lead to enhanced efficiency in the ability to shift between mental sets. We compared the performance of monolingual and fluent bilingual college students in a task-switching paradigm. Bilinguals incurred reduced switching costs in the task-switching paradigm when compared with…

  18. Switch for serial or parallel communication networks

    Science.gov (United States)

    Crosette, D.B.

    1994-07-19

    A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination. 9 figs.

  19. Mechanism of single atom switch on silicon

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Stokbro, Kurt; Thirstrup, C.;

    1998-01-01

    We demonstrate single atom switch on silicon which operates by displacement of a hydrogen atom on the silicon (100) surface at room temperature. We find two principal effects by which the switch is controlled: a pronounced maximum of the switching probability as function of sample bias and a...

  20. Bootstrapped Low-Voltage Analog Switches

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1999-01-01

    Novel low-voltage constant-impedance analog switch circuits are proposed. The switch element is a single MOSFET, and constant-impedance operation is obtained using simple circuits to adjust the gate and bulk voltages relative to the switched signal. Low-voltage (1-volt) operation is made feasible...

  1. Notch activity in the nervous system: to switch or not switch?

    Directory of Open Access Journals (Sweden)

    Blader Patrick

    2009-10-01

    Full Text Available Abstract The Notch pathway is instrumental for cell fate diversification during development. Pioneer studies conducted in Drosophila and more recent work performed in vertebrates have shown that in the nervous system, Notch is reiteratively employed when cells choose between two alternative fates, a process referred to as a binary fate decision. While the early (neural versus epidermal fate decisions mainly involve an inhibitory effect of Notch on the neural fate, late fate decisions (choice between different subtypes of neural cells have been proposed to involve a binary switch activity whereby Notch would be instructive for one fate and inhibitory for the other. We re-examine this binary switch model in light of two recent findings made in the vertebrate nervous system. First, in the zebrafish epiphysis, Notch is required to resolve a mixed identity through the inhibition of one specific fate. Second, in the murine telencephalon, Notch regulates the competence of neural progenitors to respond to the JAK/STAT pathway, thereby allowing for the induction of an astrocyte fate. In neither case is Notch instructive for the alternative fate, but rather cooperates with another signalling pathway to coordinate binary fate choices. We also review current knowledge on the molecular cascades acting downstream of Notch in the context of neural subtype diversification, a crucial issue if one is to determine Notch function as an instructive, permissive or inhibitory signal in the various cellular contexts where it is implicated. Finally, we speculate as to how such a 'non-switch' activity could contribute to the expansion of neuronal subtype diversity.

  2. Multistate Switches: Ruthenium Alkynyl-Dihydroazulene/Vinylheptafulvene Conjugates.

    Science.gov (United States)

    Vlasceanu, Alexandru; Andersen, Cecilie L; Parker, Christian R; Hammerich, Ole; Morsing, Thorbjørn J; Jevric, Martyn; Lindbaek Broman, Søren; Kadziola, Anders; Nielsen, Mogens Brøndsted

    2016-05-23

    Multimode molecular switches incorporating distinct and independently addressable functional components have potential applications as advanced switches and logic gates for molecular electronics and memory storage devices. Herein, we describe the synthesis and characterization of four switches based on the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermoswitch pair functionalized with the ruthenium-based Cp*(dppe)Ru ([Ru*]) metal complex (dppe=1,2-bis(diphenylphosphino)ethane; Cp*=pentamethylcyclopentadienyl). The [Ru*]-DHA conjugates can potentially exist in six different states accessible by alternation between DHA/VHF, Ru(II) /Ru(III) , and alkynyl/vinylidene, which can be individually stimulated by using light/heat, oxidation/reduction, and acid/base. Access to the full range of states was found to be strongly dependent on the electronic communication between the metal center and the organic photoswitch in these [Ru*]-DHA conjugates. Detailed electrochemical, spectroscopic (UV/Vis, IR, NMR), and X-ray crystallographic studies indeed reveal significant electronic interactions between the two moieties. When in direct conjugation, the ruthenium metal center was found to quench the photochemical ring-opening of DHA, which in one case could be restored by protonation or oxidation, allowing conversion to the VHF state. PMID:27114110

  3. The allosteric switching mechanism in bacteriophage MS2

    Science.gov (United States)

    Perkett, Matthew R.; Mirijanian, Dina T.; Hagan, Michael F.

    2016-07-01

    We use all-atom simulations to elucidate the mechanisms underlying conformational switching and allostery within the coat protein of the bacteriophage MS2. Assembly of most icosahedral virus capsids requires that the capsid protein adopts different conformations at precise locations within the capsid. It has been shown that a 19 nucleotide stem loop (TR) from the MS2 genome acts as an allosteric effector, guiding conformational switching of the coat protein during capsid assembly. Since the principal conformational changes occur far from the TR binding site, it is important to understand the molecular mechanism underlying this allosteric communication. To this end, we use all-atom simulations with explicit water combined with a path sampling technique to sample the MS2 coat protein conformational transition, in the presence and absence of TR-binding. The calculations find that TR binding strongly alters the transition free energy profile, leading to a switch in the favored conformation. We discuss changes in molecular interactions responsible for this shift. We then identify networks of amino acids with correlated motions to reveal the mechanism by which effects of TR binding span the protein. We find that TR binding strongly affects residues located at the 5-fold and quasi-sixfold interfaces in the assembled capsid, suggesting a mechanism by which the TR binding could direct formation of the native capsid geometry. The analysis predicts amino acids whose substitution by mutagenesis could alter populations of the conformational substates or their transition rates.

  4. Bistability in a metabolic network underpins the de novo evolution of colony switching in Pseudomonas fluorescens.

    Directory of Open Access Journals (Sweden)

    Jenna Gallie

    2015-03-01

    Full Text Available Phenotype switching is commonly observed in nature. This prevalence has allowed the elucidation of a number of underlying molecular mechanisms. However, little is known about how phenotypic switches arise and function in their early evolutionary stages. The first opportunity to provide empirical insight was delivered by an experiment in which populations of the bacterium Pseudomonas fluorescens SBW25 evolved, de novo, the ability to switch between two colony phenotypes. Here we unravel the molecular mechanism behind colony switching, revealing how a single nucleotide change in a gene enmeshed in central metabolism (carB generates such a striking phenotype. We show that colony switching is underpinned by ON/OFF expression of capsules consisting of a colanic acid-like polymer. We use molecular genetics, biochemical analyses, and experimental evolution to establish that capsule switching results from perturbation of the pyrimidine biosynthetic pathway. Of central importance is a bifurcation point at which uracil triphosphate is partitioned towards either nucleotide metabolism or polymer production. This bifurcation marks a cell-fate decision point whereby cells with relatively high pyrimidine levels favour nucleotide metabolism (capsule OFF, while cells with lower pyrimidine levels divert resources towards polymer biosynthesis (capsule ON. This decision point is present and functional in the wild-type strain. Finally, we present a simple mathematical model demonstrating that the molecular components of the decision point are capable of producing switching. Despite its simple mutational cause, the connection between genotype and phenotype is complex and multidimensional, offering a rare glimpse of how noise in regulatory networks can provide opportunity for evolution.

  5. Intrinsic ferroelectric switching from first principles

    Science.gov (United States)

    Liu, Shi; Grinberg, Ilya; Rappe, Andrew M.

    2016-06-01

    The existence of domain walls, which separate regions of different polarization, can influence the dielectric, piezoelectric, pyroelectric and electronic properties of ferroelectric materials. In particular, domain-wall motion is crucial for polarization switching, which is characterized by the hysteresis loop that is a signature feature of ferroelectric materials. Experimentally, the observed dynamics of polarization switching and domain-wall motion are usually explained as the behaviour of an elastic interface pinned by a random potential that is generated by defects, which appear to be strongly sample-dependent and affected by various elastic, microstructural and other extrinsic effects. Theoretically, connecting the zero-kelvin, first-principles-based, microscopic quantities of a sample with finite-temperature, macroscopic properties such as the coercive field is critical for material design and device performance; and the lack of such a connection has prevented the use of techniques based on ab initio calculations for high-throughput computational materials discovery. Here we use molecular dynamics simulations of 90° domain walls (separating domains with orthogonal polarization directions) in the ferroelectric material PbTiO3 to provide microscopic insights that enable the construction of a simple, universal, nucleation-and-growth-based analytical model that quantifies the dynamics of many types of domain walls in various ferroelectrics. We then predict the temperature and frequency dependence of hysteresis loops and coercive fields at finite temperatures from first principles. We find that, even in the absence of defects, the intrinsic temperature and field dependence of the domain-wall velocity can be described with a nonlinear creep-like region and a depinning-like region. Our model enables quantitative estimation of coercive fields, which agree well with experimental results for ceramics and thin films. This agreement between model and experiment suggests

  6. On the stabilization of switched linear stochastic systems with unobservable switching laws

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper is concerned with the stabilization problem of switched linear stochastic systems with unobservable switching laws. In this paper the system switches among a finite family of linear stochastic systems. Since there are noise perturbations, the switching laws can not be identified in any finite time horizon. We prove that if each individual subsystem is controllable and the switching duration uniformly has a strict positive lower bound, then the system can be stabilized by using a controller that uses online state estimation.

  7. Ultrafast all-optical switching in bacteriorhodopsin

    Science.gov (United States)

    Roy, Sukhdev; Singh, C. P.; Reddy, K. P. J.

    2001-04-01

    All-optical switching has been demonstrated in bacteriorhodopsin based on excited-state nonlinear absorption. A probe laser beam at 640 nm corresponding to the O-state absorption maximum is switched due to a strong pulsed pump laser beam at 570 nm, that corresponds to the maximum ground state absorption. We have studied the effect of variation in pulse width and in small signal absorption coefficient on the switching characteristics. The switching time decreases as the pulse width of the pump beam decreases and the small signal absorption coefficient increases. The switching contrast depends mainly on the peak pumping intensity.

  8. Secure videoconferencing equipment switching system and method

    Science.gov (United States)

    Hansen, Michael E.

    2009-01-13

    A switching system and method are provided to facilitate use of videoconference facilities over a plurality of security levels. The system includes a switch coupled to a plurality of codecs and communication networks. Audio/Visual peripheral components are connected to the switch. The switch couples control and data signals between the Audio/Visual peripheral components and one but nor both of the plurality of codecs. The switch additionally couples communication networks of the appropriate security level to each of the codecs. In this manner, a videoconferencing facility is provided for use on both secure and non-secure networks.

  9. Switched control of a nonholonomic mobile robot

    Science.gov (United States)

    Sankaranarayanan, V.; Mahindrakar, Arun D.

    2009-05-01

    We present a switched control algorithm to stabilize a car-like mobile robot which possesses velocity level nonholonomic constraint. The control approach rests on splitting the system into several second-order subsystems and then stabilizing the system sequentially using finite-time controllers, finally resulting in the mobile robot being moved from one point to another point. State dependent switching control is employed in which the controllers switches on a thin surface in the state-space. Robustness analysis is presented by redefining the switching signal using relaxed switching surface. Both, non-robust and robust controllers are validated through numerical simulation.

  10. Negation switching invariant signed graphs

    Directory of Open Access Journals (Sweden)

    Deepa Sinha

    2014-04-01

    Full Text Available A signed graph (or, $sigraph$ in short is a graph G in which each edge x carries a value $\\sigma(x \\in \\{-, +\\}$ called its sign. Given a sigraph S, the negation $\\eta(S$ of the sigraph S is a sigraph obtained from S by reversing the sign of every edge of S. Two sigraphs $S_{1}$ and $S_{2}$ on the same underlying graph are switching equivalent if it is possible to assign signs `+' (`plus' or `-' (`minus' to vertices of $S_{1}$ such that by reversing the sign of each of its edges that has received opposite signs at its ends, one obtains $S_{2}$. In this paper, we characterize sigraphs which are negation switching invariant and also see for what sigraphs, S and $\\eta (S$ are signed isomorphic.

  11. Frascati Tokamak transformer switching system

    International Nuclear Information System (INIS)

    Plasma ionization and heating, in the Frascati Tokamak, is obtained generating an emf along the plasma column, by switching the dc current flowing in the Tokamak transformer. 30 kA flowing in the 60 mH transformer inductance must be commutated into a resistance to generate 40 kV across the transformer itself. Studies and tests to solve this problem have been conducted, on different types of breakers, in cooperation between Tecnomasio Italiano Brown Boveri, Milan and Laboratori Gas Ionizzati, Frascati. Satisfactory results have finally been obtained using a DLF commercial air blast breaker in a chopper type circuit. A capacitor bank in parallel to the breaker is discharged immediately after the contacts separation and the arc in the switching element is extinguished at the first current zero. A saturable reactance in series with the breaker reduces the current decay rate to allow sufficient deionization time

  12. Shape memory thermal conduction switch

    Science.gov (United States)

    Vaidyanathan, Rajan (Inventor); Krishnan, Vinu (Inventor); Notardonato, William U. (Inventor)

    2010-01-01

    A thermal conduction switch includes a thermally-conductive first member having a first thermal contacting structure for securing the first member as a stationary member to a thermally regulated body or a body requiring thermal regulation. A movable thermally-conductive second member has a second thermal contacting surface. A thermally conductive coupler is interposed between the first member and the second member for thermally coupling the first member to the second member. At least one control spring is coupled between the first member and the second member. The control spring includes a NiTiFe comprising shape memory (SM) material that provides a phase change temperature <273 K, a transformation range <40 K, and a hysteresis of <10 K. A bias spring is between the first member and the second member. At the phase change the switch provides a distance change (displacement) between first and second member by at least 1 mm, such as 2 to 4 mm.

  13. Pinning Synchronization of Switched Complex Dynamical Networks

    Directory of Open Access Journals (Sweden)

    Liming Du

    2015-01-01

    Full Text Available Network topology and node dynamics play a key role in forming synchronization of complex networks. Unfortunately there is no effective synchronization criterion for pinning synchronization of complex dynamical networks with switching topology. In this paper, pinning synchronization of complex dynamical networks with switching topology is studied. Two basic problems are considered: one is pinning synchronization of switched complex networks under arbitrary switching; the other is pinning synchronization of switched complex networks by design of switching when synchronization cannot achieved by using any individual connection topology alone. For the two problems, common Lyapunov function method and single Lyapunov function method are used respectively, some global synchronization criteria are proposed and the designed switching law is given. Finally, simulation results verify the validity of the results.

  14. Energy storage, compression, and switching. Vol. 2

    International Nuclear Information System (INIS)

    This book is a compilation of papers presented at the Second International Conference on Energy Storage, Compression, and Switching, which was held in order to assemble active researchers with a major interest in plasma physics, electron beams, electric and magnetic energy storage systems, high voltage and high current switches, free-electron lasers, and pellet implosion plasma focus. Topics covered include: Slow systems: 50-60 Hz machinery, homopolar generators, slow capacitors, inductors, and solid state switches; Intermediate systems: fast capacitor banks; superconducting storage and switching; gas, vacuum, and dielectric switching; nonlinear (magnetic) switching; imploding liners capacitors; explosive generators; and fuses; and Fast systems: Marx, Blumlein, oil, water, and pressurized water dielectrics; switches; magnetic insulation; electron beams; and plasmas

  15. Synchronization in complex networks with switching topology

    International Nuclear Information System (INIS)

    This Letter investigates synchronization issues of complex dynamical networks with switching topology. By constructing a common Lyapunov function, we show that local and global synchronization for a linearly coupled network with switching topology can be evaluated by the time average of second smallest eigenvalues corresponding to the Laplacians of switching topology. This result is quite powerful and can be further used to explore various switching cases for complex dynamical networks. Numerical simulations illustrate the effectiveness of the obtained results in the end. -- Highlights: → Synchronization of complex networks with switching topology is investigated. → A common Lyapunov function is established for synchronization of switching network. → The common Lyapunov function is not necessary to monotonically decrease with time. → Synchronization is determined by the second smallest eigenvalue of its Laplacian. → Synchronization criterion can be used to investigate various switching cases.

  16. Polychromatic polariton laser selector switch

    OpenAIRE

    Grosso, G; Trebaol, S.; Wouters, M.; Morier-Genoud, F; Portella-Oberli, M. T.; Deveaud, B.

    2013-01-01

    Integration of optical elements into scalable chips has been at the center of a large effort in recent years. Concurrently, the separation between the diverse functions, namely switches, detectors or emitters increases significantly the final number of components on chip. Such technical limitations may be overcome by introducing agile devices able, for example, to simultaneously detect, process and emit a coherent signal. Such a pathway has been explored with different approaches that bear ad...

  17. Switch for Good Community Program

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Tabitha; Amran, Martha

    2013-11-19

    Switch4Good is an energy-savings program that helps residents reduce consumption from behavior changes; it was co-developed by Balfour Beatty Military Housing Management (BB) and WattzOn in Phase I of this grant. The program was offered at 11 Navy bases. Three customer engagement strategies were evaluated, and it was found that Digital Nudges (a combination of monthly consumption statements with frequent messaging via text or email) was most cost-effective.

  18. Correlated randomness and switching phenomena

    Science.gov (United States)

    Stanley, H. E.; Buldyrev, S. V.; Franzese, G.; Havlin, S.; Mallamace, F.; Kumar, P.; Plerou, V.; Preis, T.

    2010-08-01

    One challenge of biology, medicine, and economics is that the systems treated by these serious scientific disciplines have no perfect metronome in time and no perfect spatial architecture-crystalline or otherwise. Nonetheless, as if by magic, out of nothing but randomness one finds remarkably fine-tuned processes in time and remarkably fine-tuned structures in space. Further, many of these processes and structures have the remarkable feature of “switching” from one behavior to another as if by magic. The past century has, philosophically, been concerned with placing aside the human tendency to see the universe as a fine-tuned machine. Here we will address the challenge of uncovering how, through randomness (albeit, as we shall see, strongly correlated randomness), one can arrive at some of the many spatial and temporal patterns in biology, medicine, and economics and even begin to characterize the switching phenomena that enables a system to pass from one state to another. Inspired by principles developed by A. Nihat Berker and scores of other statistical physicists in recent years, we discuss some applications of correlated randomness to understand switching phenomena in various fields. Specifically, we present evidence from experiments and from computer simulations supporting the hypothesis that water’s anomalies are related to a switching point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell), and that the bubbles in economic phenomena that occur on all scales are not “outliers” (another Gladwell immortalization). Though more speculative, we support the idea of disease as arising from some kind of yet-to-be-understood complex switching phenomenon, by discussing data on selected examples, including heart disease and Alzheimer disease.

  19. Electrical switching of an antiferromagnet

    Czech Academy of Sciences Publication Activity Database

    Wadley, P.; Howells, B.; Železný, J.; Andrews, C.; Hills, V.; Campion, R. P.; Novák, Vít; Olejník, Kamil; Maccherozzi, F.; Dhesi, S.S.; Martin, S.Y.; Wagner, T.; Wunderlich, Joerg; Freimuth, F.; Mokrousov, Y.; Kuneš, Jan; Chauhan, J.S.; Grzybowski, M.J.; Rushforth, A.W.; Edmonds, K. W.; Gallagher, B. L.; Jungwirth, Tomáš

    2016-01-01

    Roč. 351, č. 6273 (2016), 587-590. ISSN 0036-8075 R&D Projects: GA MŠk(CZ) LM2011026; GA ČR GB14-37427G EU Projects: European Commission(XE) 268066 - 0MSPIN Institutional support: RVO:68378271 Keywords : spintronics * antiferromagnets * current induced switching Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 33.611, year: 2014

  20. Switching strategies to optimize search

    Science.gov (United States)

    Shlesinger, Michael F.

    2016-03-01

    Search strategies are explored when the search time is fixed, success is probabilistic and the estimate for success can diminish with time if there is not a successful result. Under the time constraint the problem is to find the optimal time to switch a search strategy or search location. Several variables are taken into account, including cost, gain, rate of success if a target is present and the probability that a target is present.

  1. Ultrafast photonic crystal optical switching

    Institute of Scientific and Technical Information of China (English)

    GONG Qi-huang; HU Xiao-yong

    2006-01-01

    Photonic crystal,a novel and artificial photonic material with periodic dielectric distribution,possesses photonic bandgap and can control the propagation states of photons.Photonic crystal has been considered to be a promising candidate for the future integrated photonic devices.The properties and the fabrication method of photonic crystal are expounded.The progresses of the study of ultrafast photonic crystal optical switching are discussed in detail.

  2. EMI Prediction of Switching Converters

    OpenAIRE

    Trinchero, Riccardo; Stievano, Igor Simone; Canavero, Flavio

    2015-01-01

    This paper addresses the simulation of the conducted electromagnetic interference produced by circuits with periodically switching elements. The proposed method allows for the computation of their steady-state responses by means of augmented linear time-invariant equivalents built from circuit inspection only, and standard tools for circuit analysis. The approach is demonstrated on a real dc-dc boost converter by comparing simulation results with real measurements

  3. Static Switching Dynamic Buffer Circuit

    OpenAIRE

    Pandey, A. K.; R. A. Mishra; R. K. Nagaria

    2013-01-01

    We proposed footless domino logic buffer circuit. It minimizes redundant switching at the dynamic and the output nodes. The proposed circuit avoids propagation of precharge pulse to the output node and allows the dynamic node which saves power consumption. Simulation is done using 0.18 µm CMOS technology. We have calculated the power consumption, delay, and power delay product of the proposed circuit and compared the results with the existing circuits for different logic function, loading co...

  4. Molecular Thin Films: a New Type of Magnetic Switch

    OpenAIRE

    Heutz, S. M.; Mitra, C.; Wu, W.; Fisher, A J; Kerridge, A.; Stoneham, A. M.; Harker, A. H.; Gardener, J; Tseng, Hsiang-Han; Jones, T. S.; Renner, C.; Aeppli, G.

    2008-01-01

    The design and fabrication of materials that exhibit both semiconducting and magnetic properties for spintronics and quantum computing has proven difficult. Important starting points are high-purity thin films as well as fundamental theoretical understanding of the magnetism. Here we show that small molecules have great potential in this area, due to ease of insertion of localised spins in organic frameworks and both chemical and structural purity. In particular, we demonstrate that archetypa...

  5. Molecular current switch: principles and characterization of the model system

    Czech Academy of Sciences Publication Activity Database

    Weiter, M.; Vala, M.; Nešpůrek, Stanislav; Toman, Petr

    Brno : Brno University of Technology, 2005, s. 95-99. ISBN 80-214-3085-0. [International Conference Nenamat. Brno (CZ), 08.11.2005-10.11.2005] R&D Projects: GA ČR GP203/03/D133; GA AV ČR KJB1050301 Institutional research plan: CEZ:AV0Z40500505 Keywords : photoconductivity * photochromism * charge transport Subject RIV: BJ - Thermodynamics

  6. The recombinase protein is a torque sensitive molecular switch

    CERN Document Server

    Atwell, Scott; Migliozzi, Daniel; Viovy, Jean-Louis; Cappello, Giovanni

    2016-01-01

    How a nano-searcher finds its nano-target is a general problem in non-equilibrium statistical physics. It becomes vital when the searcher is a damaged DNA fragment trying to find its counterpart on the intact homologous chromosome. If the two copies are paired, that intact homologous sequence serves as a template to reconstitute the damaged DNA sequence, enabling the cell to survive without genetic mutations. To succeed, the search must stop only when the perfect homology is found. The biological process that ensures such a genomic integrity is called Homologous Recombination and is promoted by the Recombinase proteins. In this article, we use torque-sensitive magnetic tweezers to measure the free-energy landscape of the human Recombinase hRad51 protein assembled a DNA fragment. Based on our measurements we model the hRad51/DNA complex as an out-of-equilibrium two-state system and provide a thermodynamical description of Homologous Recombination. With this dynamical two-state model, we suggest a mechanism by ...

  7. Upstream open reading frames: Molecular switches in (patho)physiology

    OpenAIRE

    Wethmar, Klaus; Smink, Jeske J.; Leutz, Achim

    2010-01-01

    Conserved upstream open reading frames (uORFs) are found within many eukaryotic transcripts and are known to regulate protein translation. Evidence from genetic and bioinformatic studies implicates disturbed uORF-mediated translational control in the etiology of human diseases. A genetic mouse model has recently provided proof-of-principle support for the physiological relevance of uORF-mediated translational control in mammals. The targeted disruption of the uORF initiation codon within the ...

  8. Upstream open reading frames: Molecular switches in (patho)physiology

    Science.gov (United States)

    Wethmar, Klaus; Smink, Jeske J; Leutz, Achim

    2010-01-01

    Conserved upstream open reading frames (uORFs) are found within many eukaryotic transcripts and are known to regulate protein translation. Evidence from genetic and bioinformatic studies implicates disturbed uORF-mediated translational control in the etiology of human diseases. A genetic mouse model has recently provided proof-of-principle support for the physiological relevance of uORF-mediated translational control in mammals. The targeted disruption of the uORF initiation codon within the transcription factor CCAAT/enhancer binding protein β (C/EBPβ) gene resulted in deregulated C/EBPβ protein isoform expression, associated with defective liver regeneration and impaired osteoclast differentiation. The high prevalence of uORFs in the human transcriptome suggests that intensified search for mutations within 5′ RNA leader regions may reveal a multitude of alterations affecting uORFs, causing pathogenic deregulation of protein expression. PMID:20726009

  9. Symmetry as a new element to control molecular switches

    OpenAIRE

    Schweighauser, Luca; Häussinger, Daniel; Neuburger, Markus; Wegner, Hermann A.

    2014-01-01

    The isomerization properties of an azocarbazole macrocycle in solution were investigated utilizing NMR spectroscopy with in situ irradiation in combination with DFT calculations. It was demonstrated that the position of azo units in a rigid macrocyclic system influences the photoisomerization pathway even if the initial all-E isomer is highly symmetric. Furthermore, the effect of ring strain on lowering the rates of thermal isomerization was demonstrated and a mechanism via an inversion-rotat...

  10. Molecular switches in carbon-rich organometallic compounds: Theoretical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Costuas, Karine, E-mail: kcostuas@univ-rennes1.fr [Sciences chimiques de Rennes, UMR 6226 CNRS - Université de Rennes 1, Avenue du Général Leclerc F-35042 Rennes (France)

    2015-01-22

    Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties.

  11. Molecular switches in carbon-rich organometallic compounds: Theoretical aspects

    International Nuclear Information System (INIS)

    Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties

  12. Receptor Tyrosine Kinases: Molecular Switches Regulating CNS Axon Regeneration

    Directory of Open Access Journals (Sweden)

    Vasanthy Vigneswara

    2012-01-01

    Full Text Available The poor or lack of injured adult central nervous system (CNS axon regeneration results in devastating consequences and poor functional recovery. The interplay between the intrinsic and extrinsic factors contributes to robust inhibition of axon regeneration of injured CNS neurons. The insufficient or lack of trophic support for injured neurons is considered as one of the major obstacles contributing to their failure to survive and regrow their axons after injury. In the CNS, many of the signalling pathways associated with neuronal survival and axon regeneration are regulated by several classes of receptor tyrosine kinases (RTK that respond to a variety of ligands. This paper highlights and summarises the most relevant recent findings pertinent to different classes of the RTK family of molecules, with a particular focus on elucidating their role in CNS axon regeneration.

  13. Coating possibilities for magnetic switches

    International Nuclear Information System (INIS)

    High average power magnetic pulse compression systems are now being considered for use in several applications such as the High Power Radiation Source (HiPoRS) project. Such systems will require high reliability magnetic switches (saturable inductors) that are very efficient and have long lifetimes. One of the weakest components in magnetic switches is their interlaminar insulation. Considerations related to dielectric breakdown, thermal management of compact designs, and economical approaches for achieving these needs must be addressed. Various dielectric insulation and coating materials have been applied to Metglas foil in an attempt to solve the complex technical and practical problems associated with large magnetic switch structures. This work reports various needs, studies, results, and proposals in selecting and evaluating continuous coating approaches for magnetic foil. Techniques such as electrophoretic polymer deposition and surface chemical oxidation are discussed. We also propose continuous photofabrication processes for applying dielectric ribs or spacers to the foil which permit circulation of dielectric liquids for cooling during repetitive operation. 10 refs., 8 figs., 11 tabs

  14. Brownian molecular rotors: Theoretical design principles and predicted realizations

    OpenAIRE

    Schönborn, Jan Boyke; Herges, Rainer; Hartke, Bernd

    2009-01-01

    We propose simple design concepts for molecular rotors driven by Brownian motion and external photochemical switching. Unidirectionality and efficiency of the motion is measured by explicit simulations. Two different molecular scaffolds are shown to yield viable molecular rotors when decorated with suitable substituents.

  15. Design and Simulation of Routing-switching Protocol Based on Optical Switch Array

    Institute of Scientific and Technical Information of China (English)

    HE Wei; MAO You-ju; LIU Jiang

    2004-01-01

    An optical routing- switching technology based on optical switch array is proposed. The characteristics of the blocking and nonblocking networks are analyzed and compared, odd- even sorting network is used to realize optical routing- switching, relative routing- switching protocol is designed.Simulation test under load shows that it can reduce a blocking effectively and enhance an efficiency of switching. Further, it can transfer the processing and switching within parallel computer from electric domain to optical domain. It can make parallel computer coordinating computing and processing at much more higher speed, storing and transmitting even more efficiently.

  16. Optical switching of electric charge transfer pathways in porphyrin: a light-controlled nanoscale current router.

    Science.gov (United States)

    Thanopulos, Ioannis; Paspalakis, Emmanuel; Yannopapas, Vassilios

    2008-11-01

    We introduce a novel molecular junction based on a thiol-functionalized porphyrin derivative with two almost energetically degenerate equilibrium configurations. We show that each equilibrium structure defines a pathway of maximal electric charge transfer through the molecular junction and that these two conduction pathways are spatially orthogonal. We further demonstrate computationally how to switch between the two equilibrium structures of the compound by coherent light. The optical switching mechanism is presented in the relevant configuration subspace of the compound, and the corresponding potential and electric dipole surfaces are obtained by ab initio methods. The laser-induced isomerization takes place in two steps in tandem, while each step is induced by a two-photon process. The effect of metallic electrodes on the electromagnetic irradiation driving the optical switching is also investigated. Our study demonstrates the potential for using thiol-functionalized porphyrin derivatives for the development of a light-controlled nanoscale current router. PMID:21832723

  17. Optical switching of electric charge transfer pathways in porphyrin: a light-controlled nanoscale current router

    International Nuclear Information System (INIS)

    We introduce a novel molecular junction based on a thiol-functionalized porphyrin derivative with two almost energetically degenerate equilibrium configurations. We show that each equilibrium structure defines a pathway of maximal electric charge transfer through the molecular junction and that these two conduction pathways are spatially orthogonal. We further demonstrate computationally how to switch between the two equilibrium structures of the compound by coherent light. The optical switching mechanism is presented in the relevant configuration subspace of the compound, and the corresponding potential and electric dipole surfaces are obtained by ab initio methods. The laser-induced isomerization takes place in two steps in tandem, while each step is induced by a two-photon process. The effect of metallic electrodes on the electromagnetic irradiation driving the optical switching is also investigated. Our study demonstrates the potential for using thiol-functionalized porphyrin derivatives for the development of a light-controlled nanoscale current router.

  18. To Switch or Not to Switch: Examine the Code-switching Practices of Teachers of Non-English Majors

    OpenAIRE

    Xu, Qing

    2010-01-01

    The paper analyzes the factors of teachers’ English/Chinese code-switching in EFL teaching for non-English majors. It also interprets the collected data so as to raise EFL teachers’ awareness of their actual use of code-switching in classroom and help them develop an appropriate attitude towards its role in EFL teaching.
    Key words: code-switching; function; classroom discourse; EFL teachers

  19. Components of attentional set-switching.

    Science.gov (United States)

    Rushworth, M F S; Passingham, R E; Nobre, A C

    2005-01-01

    A series of distinct event-related potentials (ERPs) have been recorded from the scalp of human subjects as they switch from one task to another. It is possible that task switching may depend on different mechanisms depending on whether the switch requires a change in attentional set, in other words the redirecting of attention to different aspects of a sensory stimulus, or whether it requires a change in intentional set, in others words a change in the way that responses are selected. To address this issue, the current study recorded ERPs while subjects switched between attentional sets and the results were compared with those of a previous investigation in which subjects switched between intentional sets. Subjects selected stimuli according to two conflicting attentional sets, each emphasizing one visual stimulus dimension (colour, shape). Pairs of stimuli, only one of which was to be attended, were presented for between eight and seventeen trials then either a switch or a stay cue was shown. The switch cue instructed subjects to switch from the current attentional set to the other set, while the stay cue instructed subjects to maintain the current set. Comparing ERPs time-locked to the switch and stay cues revealed neural correlates of the initiation of a task switch. Comparing the ERPs time locked to the first stimuli after either stay or switch cues identified neural correlates of the implementation of a task switch. A similar modulation over parietal electrodes was seen when subjects were switching between either attentional or intentional sets. While an intentional set switch began with a medial frontal modulation, attentional set switching began with a lateral frontal modulation. Implementing a new attentional set was associated with modulation of relatively early visual potentials, while implementing a new intentional set was associated with modulation of later response-related potentials. The results confirm that task switching consists of a number of

  20. Dichotomous noise models of gene switches

    Science.gov (United States)

    Potoyan, Davit. A.; Wolynes, Peter. G.

    2015-11-01

    Molecular noise in gene regulatory networks has two intrinsic components, one part being due to fluctuations caused by the birth and death of protein or mRNA molecules which are often present in small numbers and the other part arising from gene state switching, a single molecule event. Stochastic dynamics of gene regulatory circuits appears to be largely responsible for bifurcations into a set of multi-attractor states that encode different cell phenotypes. The interplay of dichotomous single molecule gene noise with the nonlinear architecture of genetic networks generates rich and complex phenomena. In this paper, we elaborate on an approximate framework that leads to simple hybrid multi-scale schemes well suited for the quantitative exploration of the steady state properties of large-scale cellular genetic circuits. Through a path sum based analysis of trajectory statistics, we elucidate the connection of these hybrid schemes to the underlying master equation and provide a rigorous justification for using dichotomous noise based models to study genetic networks. Numerical simulations of circuit models reveal that the contribution of the genetic noise of single molecule origin to the total noise is significant for a wide range of kinetic regimes.

  1. Dichotomous noise models of gene switches

    International Nuclear Information System (INIS)

    Molecular noise in gene regulatory networks has two intrinsic components, one part being due to fluctuations caused by the birth and death of protein or mRNA molecules which are often present in small numbers and the other part arising from gene state switching, a single molecule event. Stochastic dynamics of gene regulatory circuits appears to be largely responsible for bifurcations into a set of multi-attractor states that encode different cell phenotypes. The interplay of dichotomous single molecule gene noise with the nonlinear architecture of genetic networks generates rich and complex phenomena. In this paper, we elaborate on an approximate framework that leads to simple hybrid multi-scale schemes well suited for the quantitative exploration of the steady state properties of large-scale cellular genetic circuits. Through a path sum based analysis of trajectory statistics, we elucidate the connection of these hybrid schemes to the underlying master equation and provide a rigorous justification for using dichotomous noise based models to study genetic networks. Numerical simulations of circuit models reveal that the contribution of the genetic noise of single molecule origin to the total noise is significant for a wide range of kinetic regimes

  2. Dichotomous noise models of gene switches

    Energy Technology Data Exchange (ETDEWEB)

    Potoyan, Davit A., E-mail: potoyan@rice.edu; Wolynes, Peter G., E-mail: pwolynes@rice.edu [Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005 (United States)

    2015-11-21

    Molecular noise in gene regulatory networks has two intrinsic components, one part being due to fluctuations caused by the birth and death of protein or mRNA molecules which are often present in small numbers and the other part arising from gene state switching, a single molecule event. Stochastic dynamics of gene regulatory circuits appears to be largely responsible for bifurcations into a set of multi-attractor states that encode different cell phenotypes. The interplay of dichotomous single molecule gene noise with the nonlinear architecture of genetic networks generates rich and complex phenomena. In this paper, we elaborate on an approximate framework that leads to simple hybrid multi-scale schemes well suited for the quantitative exploration of the steady state properties of large-scale cellular genetic circuits. Through a path sum based analysis of trajectory statistics, we elucidate the connection of these hybrid schemes to the underlying master equation and provide a rigorous justification for using dichotomous noise based models to study genetic networks. Numerical simulations of circuit models reveal that the contribution of the genetic noise of single molecule origin to the total noise is significant for a wide range of kinetic regimes.

  3. The role of inhibitory control in task switching

    OpenAIRE

    Yang, Violet Hye-Won

    2010-01-01

    Previous research on task switching has been confounded by inhibitory control mechanism and there has been debate on the source of switch costs and how and when the inhibitory control occurs during task switching. In order to circumvent this problem, the thesis aimed to investigate the role of inhibition in task switching by examining switch costs, alternating switch costs and congruency effect in three tasks when two preparation intervals (short and long) are given. Task switching experiment...

  4. Ultra High-Speed Radio Frequency Switch Based on Photonics

    OpenAIRE

    Jia Ge; Fok, Mable P.

    2015-01-01

    Microwave switches, or Radio Frequency (RF) switches have been intensively used in microwave systems for signal routing. Compared with the fast development of microwave and wireless systems, RF switches have been underdeveloped particularly in terms of switching speed and operating bandwidth. In this paper, we propose a photonics based RF switch that is capable of switching at tens of picoseconds speed, which is hundreds of times faster than any existing RF switch technologies. The high-speed...

  5. Know-How on design of switching regulator

    International Nuclear Information System (INIS)

    This book introduces switching regulator from base to application, which deals with fundamentals of switching regulator such as the reason of boom about switching regulator, understanding simple circuit without electric transformer and decision of circuit type with input voltage and output voltage, configuration and characteristic of switching regulator, a concrete design of switching regulator, pulse width control circuit and protection circuit, concrete circuit examples of switching power and the point of switching regulator.

  6. Switching control of an R/C hovercraft: stabilization and smooth switching.

    Science.gov (United States)

    Tanaka, K; Iwasaki, M; Wang, H O

    2001-01-01

    This paper presents stable switching control of an radio-controlled (R/C) hovercraft that is a nonholonomic (nonlinear) system. To exactly represent its nonlinear dynamics, more importantly, to maintain controllability of the system, we newly propose a switching fuzzy model that has locally Takagi-Sugeno (T-S) fuzzy models and switches them according to states, external variables, and/or time. A switching fuzzy controller is constructed by mirroring the rule structure of the switching fuzzy model of an R/C hovercraft. We derive linear matrix inequality (LMI) conditions for ensuring the stability of the closed-loop system consisting of a switching fuzzy model and controller. Furthermore, to guarantee smooth switching of control input at switching boundaries, we also derive a smooth switching condition represented in terms of LMIs. A stable switching fuzzy controller satisfying the smooth switching condition is designed by simultaneously solving both of the LMIs. The simulation and experimental results for the trajectory control of an R/C hovercraft show the validity of the switching fuzzy model and controller design, particularly, the smooth switching condition. PMID:18244851

  7. Topological Nanocolloids with Facile Electric Switching of Plasmonic Properties

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Ye; Smalyukh, Ivan I.

    2015-12-01

    Combining topology and plasmonics paradigms in nanocolloidal systems may enable new means of pre-engineering desired composite material properties. Here we design and realize orientationally ordered assemblies of noble metal nanoparticles with genus-one topology and unusual long-range ordering mediated by their interactions with the surrounding nematic fluid host. Facile electric switching of these composites is reminiscent of that of pristine liquid crystals (LCs), but provides a means of reconfiguring the nanoparticle assembly and thus also the ensuing composite medium's optical properties. Our findings may lead to formation of new molecular-colloidal soft matter phases with unusual optical properties, as well as optical metamaterials.

  8. Attraction or Repulsion? London Dispersion Forces Control Azobenzene Switches.

    Science.gov (United States)

    Schweighauser, Luca; Strauss, Marcel A; Bellotto, Silvia; Wegner, Hermann A

    2015-11-01

    Large substituents are commonly seen as entirely repulsive through steric hindrance. Such groups have additional attractive effects arising from weak London dispersion forces between the neutral atoms. Steric interactions are recognized to have a strong influence on isomerization processes, such as in azobenzene-based molecular switches. Textbooks indicate that steric hindrance destabilizes the Z isomers. Herein, we demonstrate that increasing the bulkiness of electronically equal substituents in the meta-position decreases the thermal reaction rates from the Z to the E isomers. DFT computations revealed that attractive dispersion forces essentially lower the energy of the Z isomers. PMID:26350759

  9. Topological nanocolloids with facile electric switching of plasmonic properties.

    Science.gov (United States)

    Yuan, Ye; Smalyukh, Ivan I

    2015-12-01

    Combining topology and plasmonics paradigms in nanocolloidal systems may enable new means of pre-engineering desired composite material properties. Here we design and realize orientationally ordered assemblies of noble metal nanoparticles with genus-one topology and unusual long-range ordering mediated by their interactions with the surrounding nematic fluid host. Facile electric switching of these composites is reminiscent of that of pristine liquid crystals (LCs), but provides a means of reconfiguring the nanoparticle assembly and thus also the ensuing composite medium's optical properties. Our findings may lead to formation of new molecular-colloidal soft matter phases with unusual optical properties, as well as optical metamaterials. PMID:26625068

  10. MEMS switches having non-metallic crossbeams

    Science.gov (United States)

    Scardelletti, Maximillian C (Inventor)

    2009-01-01

    A RF MEMS switch comprising a crossbeam of SiC, supported by at least one leg above a substrate and above a plurality of transmission lines forming a CPW. Bias is provided by at least one layer of metal disposed on a top surface of the SiC crossbeam, such as a layer of chromium followed by a layer of gold, and extending beyond the switch to a biasing pad on the substrate. The switch utilizes stress and conductivity-controlled non-metallic thin cantilevers or bridges, thereby improving the RF characteristics and operational reliability of the switch. The switch can be fabricated with conventional silicon integrated circuit (IC) processing techniques. The design of the switch is very versatile and can be implemented in many transmission line mediums.

  11. Pulse switching for high energy lasers

    Science.gov (United States)

    Laudenslager, J. B.; Pacala, T. J. (Inventor)

    1981-01-01

    A saturable inductor switch for compressing the width and sharpening the rise time of high voltage pulses from a relatively slow rise time, high voltage generator to an electric discharge gas laser (EDGL) also provides a capability for efficient energy transfer from a high impedance primary source to an intermediate low impedance laser discharge network. The switch is positioned with respect to a capacitive storage device, such as a coaxial cable, so that when a charge build-up in the storage device reaches a predetermined level, saturation of the switch inductor releases or switches energy stored in the capactive storage device to the EDGL. Cascaded saturable inductor switches for providing output pulses having rise times of less than ten nanoseconds and a technique for magnetically biasing the saturable inductor switch are disclosed.

  12. High voltage, magnetically switched pulsed power systems

    International Nuclear Information System (INIS)

    The principles of magnetic switching are briefly described. Then the results of experiments on the following substantive topics for magnetic switching are presented: material properties and how they relate to switch performance, risetime limitations, and core insulation. Magnetic switching is then evaluated from a system perspective. An idealized pulse power system with 200 kJ or stored energy and a 40 ns output pulse is examined. The multi-megavolt electrical insulation requirements impose limitations on the switches. The cost of the magnetically switched system exceeds the cost of the conventional superpower generator system by up to 75%. The potential for reliability, reproducibility, and repetitive pulse capability must be evaluated for each application to offset the increased cost

  13. Exponential stabilization of switched stochastic dynamical networks

    International Nuclear Information System (INIS)

    A switched stochastic dynamical network (SSDN) model will firstly be formulated in this paper, which considers two mutually independent switching signals including individual node switching and network topology switching. In the proposed SSDN model, the stochastic perturbation is described by multi-dimensional Brownian motion, and the switching signals are arbitrary under the constraint of the average dwell time. A multiple Lyapunov function is utilized to cope with the switching problem. A single controller is then designed for the exponential mean square stabilization for SSDNs. The coupling matrix of the SSDN can be assumed to be irreducible symmetric or irreducible asymmetric. The obtained criteria are given in terms of linear matrix inequalities, which can be solved efficiently by standard software packages. Numerical examples, including small-world and scale-free networks, are exploited to illustrate the effectiveness of the theoretical results. It can be observed from the examples that our results are also applicable to large-scale dynamical networks

  14. Switched steerable multiple beam antenna system

    Science.gov (United States)

    Iwasaki, Richard S.

    1988-09-01

    A steerable multibeam five element cross-feed cluster antenna system is described. The feed power is divided into five branches. Each branch includes a switching network comprised of a plurality of time delay elements each individually controlled by a respective electromagnetic latching switch. Frequency independent individual two-dimensional beam steering at intermediate (IF) scanning frequencies is thereby provided wherein discrete incremental time delays are introduced by the switching networks into each branch and the signals recombined thereafter to form each beam. The electromagnetic latched switching reduces power consumption and permits higher power switching and reciprocal coincident tranmsit and receive operation. Frequency independence due to incremental time delay switching permits coincident reciprocal operation and steering for transmit-receive signal paths carrying different transmit-receive frequencies. Diagonal quarter wave plates in the waveguides alter polarization from the circular to orthogonal linear to provide transmitter-receiver isolation.

  15. Multiprocessor switch with selective pairing

    Energy Technology Data Exchange (ETDEWEB)

    Gara, Alan; Gschwind, Michael K; Salapura, Valentina

    2014-03-11

    System, method and computer program product for a multiprocessing system to offer selective pairing of processor cores for increased processing reliability. A selective pairing facility is provided that selectively connects, i.e., pairs, multiple microprocessor or processor cores to provide one highly reliable thread (or thread group). Each paired microprocessor or processor cores that provide one highly reliable thread for high-reliability connect with a system components such as a memory "nest" (or memory hierarchy), an optional system controller, and optional interrupt controller, optional I/O or peripheral devices, etc. The memory nest is attached to a selective pairing facility via a switch or a bus

  16. Designing bistable [2]rotaxanes for molecular electronic devices.

    Science.gov (United States)

    Dichtel, William R; Heath, James R; Stoddart, J Fraser

    2007-06-15

    The development of molecular electronic components has been accelerated by the promise of increased circuit densities and reduced power consumption. Bistable rotaxanes have been assembled into nanowire crossbar devices, where they may be switched between low- and high-conductivity states, forming the basis for a molecular memory. These memory devices have been scaled to densities of 10(11) bits cm(-2), the 2020 node for memory of the International Technology Roadmap for Semiconductors. Investigations of the kinetics and thermodynamics associated with the electromechanical switching processes of several bistable [2]rotaxane derivatives in solution, self-assembled monolayers on gold, polymer electrolyte gels and in molecular switch tunnel junction devices are consistent with a single, universal switching mechanism whose speed is dependent largely on the environment, as well as on the structure of the switching molecule. X-ray reflectometry studies of the bistable rotaxanes assembled into Langmuir monolayers also lend support to an oxidatively driven mechanical switching process. Structural information obtained from Fourier transform reflection absorption infrared spectroscopy of rotaxane monolayers taken before and after evaporation of a Ti top electrode confirmed that the functionality responsible for switching is not affected by the metal deposition process. All the considerable experimental data, taken together with detailed computational work, support the hypothesis that the tunnelling current hysteresis, which forms the basis of memory operation, is a direct result of the electromechanical switching of the bistable rotaxanes. PMID:17430812

  17. AIR LOAD BREAK SWITCH DESIGN PARAMETERS

    OpenAIRE

    Støa-Aanensen, Nina Sasaki

    2015-01-01

    Current interruption is vital in the power system, as this makes it possible to control the use of different loads, change the grid configuration, and minimize damage when faults occur. This thesis presents a study of the different switch design and test circuit parameters involved in medium voltage air load break switching and how they affect the thermal interrupting capability. Mediumvoltage load break switches are common in the distribution grid, and are a cheaper option ...

  18. Redox-Dependent Conformational Switching of Diphenylacetylenes

    Directory of Open Access Journals (Sweden)

    Ian M. Jones

    2014-07-01

    Full Text Available Herein we describe the design and synthesis of a redox-dependent single-molecule switch. Appending a ferrocene unit to a diphenylacetylene scaffold gives a redox-sensitive handle, which undergoes reversible one-electron oxidation, as demonstrated by cyclic voltammetry analysis. 1H-NMR spectroscopy of the partially oxidized switch and control compounds suggests that oxidation to the ferrocenium cation induces a change in hydrogen bonding interactions that results in a conformational switch.

  19. Qubit decoherence due to detector switching

    OpenAIRE

    Serban, I.; Wilhelm, F.K.

    2009-01-01

    We provide insight into the qubit measurement process involving a switching type of detector. We study the switching-induced decoherence during escape events. We present a simple method to obtain analytical results for the qubit dephasing and bit-flip errors, which can be easily adapted to various systems. Within this frame we investigate potential of switching detectors for a fast but only weakly invasive type of detection. We show that the mechanism that leads to strong dephasing, and thus ...

  20. COMMITMENT AND SWITCHING INTENTIONS: CUSTOMERS AND BRANDS

    OpenAIRE

    Juliana Werneck Rodrigues; Jorge Ferreira da Silva; Jorge Brantes Ferreira; Luis Fernando Hor-Meyll

    2012-01-01

    This study aims to evaluate the relationship between a customer’s brand switching intentions and his commitment to a brand. Based on a literature review, constructs related to customer brand commitment were identified (affective and continuance commitment, trust, satisfaction, switching costs and alternative attractiveness) and their roles in the formation of brand switching intentions hypothesized. Through a cross-sectional survey, a sample of 201 smartphone users was collected to test the p...

  1. AN ANALYTICAL STUDY OF SWITCHING TRACTION MOTORS

    Directory of Open Access Journals (Sweden)

    V. M. Bezruchenko

    2010-03-01

    Full Text Available The analytical study of switching of the tractive engines of electric locomotives is conducted. It is found that the obtained curves of change of current of the sections commuted correspond to the theory of average rectilinear switching. By means of the proposed method it is possible on the stage of design of tractive engines to forecast the quality of switching and to correct it timely.

  2. Switched reluctance drives for electric vehicle applications

    OpenAIRE

    Andrada Gascón, Pedro; Torrent Burgués, Marcel; Blanqué Molina, Balduino; Perat Benavides, Josep Ignasi

    2003-01-01

    Electric vehicles are the only alternative for a clean, efficient and environmentally friendly urban transport system. With the increasing interest in electric drives for electric vehicle propulsion. This paper first tries to explain why the switched reluctance drive is a strong candidate for electric vehicle applications. It then gives switched reluctance drive design guidelines for battery or fuel cell operated electric vehicles. Finally, it presents the design and simulation of a switched ...

  3. Biomolecular engineering of intracellular switches in eukaryotes

    OpenAIRE

    Pastuszka, M.K.; Mackay, J.A.

    2010-01-01

    Tools to selectively and reversibly control gene expression are useful to study and model cellular functions. When optimized, these cellular switches can turn a protein's function “on” and “off” based on cues designated by the researcher. These cues include small molecules, drugs, hormones, and even temperature variations. Here we review three distinct areas in gene expression that are commonly targeted when designing cellular switches. Transcriptional switches target gene expression at the l...

  4. Simplified design of switching power supplies

    CERN Document Server

    Lenk, John

    1996-01-01

    Simplified Design of Switching Power Supplies is an all-inclusive, one-stop guide to switching power-supply design. Step-by-step instructions and diagrams render this book essential for the student and the experimenter, as well as the design professional.Simplified Design of Switching Power Supplies concentrates on the use of IC regulators. All popular forms of switching supplies, including DC-DC converters, inverters, buck, boost, buck-boost, pulse frequency modulation, pulse width modulation, current-mode control and pulse skipping, are described in detail. The design examples may

  5. A Heat Switch for Space Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Various planned NASA missions require heat switches for active thermal control. As an example cryocoolers, including redundant coolers are incorporated on select...

  6. A Thermal Switch for Space Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Various planned NASA missions require thermal switches for active thermal control. As an example cryocoolers, including redundant coolers are incorporated on select...

  7. Oscillatory Dynamical Switching System of Bulk Ferroelectrics

    Directory of Open Access Journals (Sweden)

    M. N.A. Halif

    2005-01-01

    Full Text Available This study gives a detailed account of calculation of the bulk ferroelectric (FE oscillatory dynamical system switching to first and second-order phase transition, respectively. All the formalism is delineated in the framework of Landau free-energy expansion and Landau-Khalatnikov (LK equation of motion where the effect of external energy may affray FE atoms similar to the spring damped oscillatory system. Here we scrutinized the switching properties from free-energy expansion and hysteresis loop. The polarization and current switching appropriate to the estimated complete switching time, changing of temperature, electric field and damping are scrutinized and discussed.

  8. Clocking Scheme for Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed.......A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed....

  9. Simplified design of switching power supplies

    CERN Document Server

    Lenk, John

    1995-01-01

    * Describes the operation of each circuit in detail * Examines a wide selection of external components that modify the IC package characteristics * Provides hands-on, essential information for designing a switching power supply Simplified Design of Switching Power Supplies is an all-inclusive, one-stop guide to switching power-supply design. Step-by-step instructions and diagrams render this book essential for the student and the experimenter, as well as the design professional. Simplified Design of Switching Power Supplies concentrates on the use of IC regulators. All popular forms of swit

  10. Low-Voltage Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Bidari, E.; Keskin, M.; Maloberti, F.; Moon, U.; Steensgaard-Madsen, Jesper; Temes, G.C.

    Switched-capacitor stages are described which can function with very low (typically 1 V) supply voltages, without using voltage boosting or switched op-amps. Simulations indicate that high performance may be achieved using these circuits in filter or data converter applications.......Switched-capacitor stages are described which can function with very low (typically 1 V) supply voltages, without using voltage boosting or switched op-amps. Simulations indicate that high performance may be achieved using these circuits in filter or data converter applications....

  11. Modified Embedded Switched Inductor Z Source Inverter

    Directory of Open Access Journals (Sweden)

    V. Saravanan

    2014-05-01

    Full Text Available A novel modified embedded switched inductor Z-source inverter is proposed by inserting the photovoltaic panels at various locations to improve the output voltage boosting performance. The proposed inverter have the concepts of embedded and switched inductor Z source network to have better features in terms of increased voltage boost inversion ability, continuous input current, reduced voltage stress on the switches/capacitors. Simulations are carried out by employing (120° pulse width modulation scheme. Hardware implementation of the proposed topology of rating 150 W, 60 V is made and the results are experimentally verified. Switch device power and reliability evaluation of the proposed inverter are also calculated.

  12. Multipath packet switch using packet bundling

    DEFF Research Database (Denmark)

    Berger, Michael Stubert

    The basic concept of packet bundling is to group smaller packets into larger packets based on, e.g., quality of service or destination within the packet switch. This paper presents novel applications of bundling in packet switching. The larger packets created by bundling are utilized to extend...... switching capacity by use of parallel switch planes. During the bundling operation, packets will experience a delay that depends on the actual implementation of the bundling and scheduling scheme. Analytical results for delay bounds and buffer size requirements are presented for a specific scheduling...

  13. Digital switching noise as a stochastic process

    Science.gov (United States)

    Boselli, Giorgio; Trucco, Gabriella; Liberali, Valentino

    2007-06-01

    Switching activity of logic gates in a digital system is a deterministic process, depending on both circuit parameters and input signals. However, the huge number of logic blocks in a digital system makes digital switching a cognitively stochastic process. Switching activity is the source of the so-called "digital noise", which can be analyzed using a stochastic approach. For an asynchronous digital network, we can model digital switching currents as a shot noise process, deriving both its amplitude distribution and its power spectral density. From spectral distribution of digital currents, we can also calculate the spectral distribution and the power of disturbances injected into the on-chip power supply lines.

  14. Development of high precision switching power supply

    International Nuclear Information System (INIS)

    A high precision switching power supply was developed for the PFN modulator of RIKEN SACLA. The maximum output voltage is 50 kV, and the maximum repetition rate is 120 pps. The switching power supply consists of main and sub switching circuits. In the sub circuit, the pulse-width-modulation (PWM) method was used in order to obtain high precision charging voltage stability ( < 100 ppm–pp). The switching power supply was tested, and a charging voltage stability of 1 Vpp (20 ppm–pp) and a repetition rate of 120 pps were achieved. (author)

  15. Clocking Scheme for Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1998-01-01

    A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed.......A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed....

  16. Atomic origin of ultrafast resistance switching in nanoscale electrometallization cells

    Science.gov (United States)

    Onofrio, Nicolas; Guzman, David; Strachan, Alejandro

    2015-04-01

    Nanoscale resistance-switching cells that operate via the electrochemical formation and disruption of metallic filaments that bridge two electrodes are among the most promising devices for post-CMOS electronics. Despite their importance, the mechanisms that govern their remarkable properties are not fully understood, especially for nanoscale devices operating at ultrafast rates, limiting our ability to assess the ultimate performance and scalability of this technology. We present the first atomistic simulations of the operation of conductive bridging cells using reactive molecular dynamics with a charge equilibration method extended to describe electrochemical reactions. The simulations predict the ultrafast switching observed in these devices, with timescales ranging from hundreds of picoseconds to a few nanoseconds for devices consisting of Cu active electrodes and amorphous silica dielectrics and with dimensions corresponding to their scaling limit (cross-sections below 10 nm). We find that single-atom-chain bridges often form during device operation but that they are metastable, with lifetimes below a nanosecond. The formation of stable filaments involves the aggregation of ions into small metallic clusters, followed by a progressive chemical reduction as they become connected to the cathode. Contrary to observations in larger cells, the nanoscale conductive bridges often lack crystalline order. An atomic-level mechanistic understanding of the switching process provides guidelines for materials optimization for such applications and the quantitative predictions over an ensemble of devices provide insight into their ultimate scaling and performance.

  17. Radically enhanced molecular recognition

    KAUST Repository

    Trabolsi, Ali

    2009-12-17

    The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of host-guest chemistry, extending its practice beyond the traditional reliance on neutral and charged guests and hosts. In particular, transporting the concept of radical dimerization into the field of mechanically interlocked molecules introduces a higher level of control within molecular switches and machines. Herein, we report that bistable and tristable [2]rotaxanes can be switched by altering electrochemical potentials. In a tristable [2]rotaxane composed of a cyclobis(paraquat-p-phenylene) ring and a dumbbell with tetrathiafulvalene, dioxynaphthalene and bipyridinium recognition sites, the position of the ring can be switched. On oxidation, it moves from the tetrathiafulvalene to the dioxynaphthalene, and on reduction, to the bipyridinium radical cation, provided the ring is also reduced simultaneously to the diradical dication. © 2010 Macmillan Publishers Limited. All rights reserved.

  18. Implementation of a Novel Soft-Switching Topology for Switched Reluctance Motor Drives

    OpenAIRE

    Yadlapalli, Naveen

    1999-01-01

    The purpose of this thesis is to design, develop, implement and test a novel soft-switching inverter topology suitable for switched reluctance motor drives. Present research being done in the field of switched reluctance motor drive inverters, including soft-switching inverters, is discussed. The novel topology is presented and the principle of operation is described in detail. The validity of the topology is verified through simulation. The various components of the system are designed and t...

  19. A novel zero-current soft-switching converter for switched reluctance motor drives

    OpenAIRE

    Ching, TW; Chan, CC; Chan, MSW; Chau, KT

    1998-01-01

    A new zero-current-transition (ZCT) power converter for switched reluctance motor drive applications is presented. The proposed ZCT power converter possesses the definite advantages that both the main and auxiliary switches are operating with zero-current switching (ZCS), as well as minimum current and voltage stresses. It has a simple circuit topology, minimum component count and low cost. The ZCT technique can significantly reduce the switch-on or -off losses by forcing the current to zero ...

  20. The Application of High Temperature Superconducting Materials to Power Switches

    CERN Document Server

    March, S A; Ballarino, A

    2009-01-01

    Superconducting switches may find application in superconducting magnet systems that require energy extraction. Such superconducting switches could be bypass-switches that are operated in conjunction with a parallel resistor or dump-switches where all of the energy is dissipated in the switch itself. Bypass-switches are more suited to higher energy circuits as a portion of the energy can be dissipated in the external dump resistor. Dump- switches require less material and triggering energy as a lower switch resistance is needed to achieve the required total dump resistance. Both superconducting bypass-switches and superconducting dump-switches can be ther- mally activated. Switching times that are comparable to those obtained with mechanical bypass-switch systems can be achieved using a co-wound heater that is powered by a ca- pacitor discharge. Switches that have fast thermal diffusion times through the insulation can be modelled as a lumped system whereas those with slow thermal diffusion times were modelle...

  1. Simultaneous ultraviolet laser triggering of two multimegavolt gas switches

    International Nuclear Information System (INIS)

    The output from a low-beam-divergence KrF ultraviolet laser has been used to simultaneously trigger two multimegavolt gas-filled switches emersed in a water dielectric. Focusing 55 mJ of laser energy into the interelectrode gap of each switch has produced simultaneity jitter of < or =1.7 ns for closure of both 2.40-MV self-breakdown voltage (SBV) switches. Both switches have displayed essentially identical switching behavior, with individual switch jitter < or approx. =2.3 ns. The triggering delay to switch closure after laser irradiation of the switch has exhibited linear dependence upon switch voltage in the 60%--90% SBV region

  2. Loss comparison of different nine-switch and twelve-switch energy conversion systems

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Loh, Poh Chiang; Qin, Zian;

    2014-01-01

    answer only available after performing a thorough analysis. For that, it is the intention now to compare the nine-switch and twelve-switch converters when they are used in ac-ac, ac-dc, dc-ac or dc-dc energy conversion systems. Their losses will be compared to identify when the nine-switch converter will...

  3. Modeling and control of switching max-plus-linear systems with random and deterministic switching

    NARCIS (Netherlands)

    Van den Boom, T.J.J.; De Schutter, B.

    2012-01-01

    Switching max-plus-linear (SMPL) systems are discrete-event systems that can switch between different modes of operation. In each mode the system is described by a max-plus-linear state equation and a max-plus-linear output equation, with different system matrices for each mode. The switching may de

  4. Sequential Effects in Deduction: Cost of Inference Switch

    Science.gov (United States)

    Milan, Emilio G.; Moreno-Rios, Sergio; Espino, Orlando; Santamaria, Carlos; Gonzalez-Hernandez, Antonio

    2010-01-01

    The task-switch paradigm has helped psychologists gain insight into the processes involved in changing from one activity to another. The literature has yielded consistent results about switch cost reconfiguration (abrupt offset in regular task-switch vs. gradual reduction in random task-switch; endogenous and exogenous components of switch cost;…

  5. Implementasi Sistem Step By Step Switching Menggunakan Komponen Terintegrasi

    OpenAIRE

    Suherman

    2009-01-01

    Sentral yang menggunakan sistem step by step switching telah lama ditinggalkan. Teknologi telah beralih ke sistem switching digital common control, bahkan berbasis packet switching khususnya penggunaan IP based Network. Namun demikian, teknologi switching step by step yang dahulu berbasis sistem mekanis masih dapat diperbaharui dengan memanfaatkan komponen terintegrasi (integrates cicuit, IC). Sistem switching step by step dengan komponen terintegrasi ini dapat dimanfaatkan untuk membentuk...

  6. Switching tests for the LCTF protective dump circuit

    International Nuclear Information System (INIS)

    Each of the six coils in the Large Coil Test Facility (LCTF) has a separate power supply, dump resistor, and switching circuit. Each switching circuit contains five switches, two of which are redundant. The three remaining switches perform separate duties in an emergency dump situation. These three switches were tested to determine their ability to meet the LCTF conditions

  7. A Comparison of High-Voltage Switches

    Energy Technology Data Exchange (ETDEWEB)

    Chu, K.W.; Scott, G.L.

    1999-02-01

    This report summarizes our work on high-voltage switches during the past few years. With joint funding from the Department of Energy (DOE) and the Department of Defense (DOD), we tested a wide variety of switches to a common standard. This approach permitted meaningful comparisons between disparate switches. Most switches were purchased from commercial sources, though some were experimental devices. For the purposes of this report, we divided the switches into three generic types (gas, vacuum, and semiconductor) and selected data that best illustrates important strengths and weaknesses of each switch type. Test techniques that indicate the state of health of the switches are emphasized. For example, a good indicator of residual gas in a vacuum switch is the systematic variation of the switching delay in response to changes in temperature and/or operating conditions. We believe that the presentation of this kind of information will help engineers to select and to test switches for their particular applications. Our work was limited to switches capable of driving slappers. Also known as exploding-foil initiators, slappers are detonators that initiate a secondary explosive by direct impact with a small piece of matter moving at the detonation velocity (several thousands of meters per second). A slapper is desirable for enhanced safety (no primary explosive), but it also places extra demands on the capacitor-discharge circuit to deliver a fast-rising current pulse (greater than 10 A/ns) of several thousand amperes. The required energy is substantially less than one joule; but this energy is delivered in less than one microsecond, taking the peak power into the megawatt regime. In our study, the switches operated in the 1 kV to 3 kV range and were physically small, roughly 1 cm{sup 3} or less. Although a fuze functions only once in actual use, multiple-shot capability is important for production testing and for research work. For this reason, we restricted this report

  8. Molecular physics

    CERN Document Server

    Williams, Dudley

    2013-01-01

    Methods of Experimental Physics, Volume 3: Molecular Physics focuses on molecular theory, spectroscopy, resonance, molecular beams, and electric and thermodynamic properties. The manuscript first considers the origins of molecular theory, molecular physics, and molecular spectroscopy, as well as microwave spectroscopy, electronic spectra, and Raman effect. The text then ponders on diffraction methods of molecular structure determination and resonance studies. Topics include techniques of electron, neutron, and x-ray diffraction and nuclear magnetic, nuclear quadropole, and electron spin reson

  9. The combination of positive and negative feedback loops confers exquisite flexibility to biochemical switches

    International Nuclear Information System (INIS)

    A wide range of cellular processes require molecular regulatory pathways to convert a graded signal into a discrete response. One prevalent switching mechanism relies on the coexistence of two stable states (bistability) caused by positive feedback regulations. Intriguingly, positive feedback is often supplemented with negative feedback, raising the question of whether and how these two types of feedback can cooperate to control discrete cellular responses. To address this issue, we formulate a canonical model of a protein–protein interaction network and analyze the dynamics of a prototypical two-component circuit. The appropriate combination of negative and positive feedback loops can bring a bistable circuit close to the oscillatory regime. Notably, sharply activated negative feedback can give rise to a bistable regime wherein two stable fixed points coexist and may collide pairwise with two saddle points. This specific type of bistability is found to allow for separate and flexible control of switch-on and switch-off events, for example (i) to combine fast and reversible transitions, (ii) to enable transient switching responses and (iii) to display tunable noise-induced transition rates. Finally, we discuss the relevance of such bistable switching behavior, and the circuit topologies considered, to specific biological processes such as adaptive metabolic responses, stochastic fate decisions and cell-cycle transitions. Taken together, our results suggest an efficient mechanism by which positive and negative feedback loops cooperate to drive the flexible and multifaceted switching behaviors arising in biological systems

  10. Design and Simulation of a Soft Switched Dc Boost Converter for Switched Reluctance Motor

    Directory of Open Access Journals (Sweden)

    X. F. Joseph

    2012-01-01

    Full Text Available Problem statement: This study presents the design and simulation of a soft switched boost converter for a switched reluctance motor with a closed loop controller. A soft switching scheme is proposed in the converter with minimum components, which reduces the switching loss and stress across the switch so that the harmonic generation is reduced in the output. The switch used in this converter switched ON at zero current and switched OFF at zero voltage. Approach: Most of the research was done on the power converter circuit of the SRM to control the speed. But in the proposed system a soft switched boost converter was designed to regulate the input voltage to SRM for any line variations and a power converter is used to control the speed of SRM. The PI controller was used as closed loop controllers, which improves the speed control of the switched reluctance motor for any load and regulates the input voltage to SRM for any line variations. The duty cycle of the switch is controlled by PI controller using PWM technique. A 500W/50KHz PWM based soft switched boost converter was designed and simulated for 6/4 pole 3 phase SRM with variable loads. The results were simulated using MATLAB SIMULINK. Results: The output of the soft switched dc converter gives a constant output voltage for any line variations, so that the input voltage to SRM is constant. The output speed of the SRM is controlled using PI controller and rotor current. Conclusion: The soft switched dc converter regulates the input supply and a power converter control the speed of Switched reluctance motor simultaneously.

  11. Wholly Synthetic Molecular Machines.

    Science.gov (United States)

    Cheng, Chuyang; Stoddart, J Fraser

    2016-06-17

    The past quarter of a century has witnessed an increasing engagement on the part of physicists and chemists in the design and synthesis of molecular machines de novo. This minireview traces the development of artificial molecular machines from their prototypes in the form of shuttles and switches to their emergence as motors and pumps where supplies of energy in the form of chemical fuel, electrochemical potential and light activation become a minimum requirement for them to function away from equilibrium. The challenge facing this rapidly growing community of scientists and engineers today is one of putting wholly synthetic molecules to work, both individually and as collections. Here, we highlight some of the recent conceptual and practical advances relating to the operation of wholly synthetic rotary and linear motors. PMID:26833859

  12. A sub-1-volt nanoelectromechanical switching device

    Science.gov (United States)

    Lee, Jeong Oen; Song, Yong-Ha; Kim, Min-Wu; Kang, Min-Ho; Oh, Jae-Sub; Yang, Hyun-Ho; Yoon, Jun-Bo

    2013-01-01

    Nanoelectromechanical (NEM) switches have received widespread attention as promising candidates in the drive to surmount the physical limitations currently faced by complementary metal oxide semiconductor technology. The NEM switch has demonstrated superior characteristics including quasi-zero leakage behaviour, excellent density capability and operation in harsh environments. However, an unacceptably high operating voltage (4-20 V) has posed a major obstacle in the practical use of the NEM switch in low-power integrated circuits. To utilize the NEM switch widely as a core device component in ultralow power applications, the operation voltage needs to be reduced to 1 V or below. However, sub-1 V actuation has not yet been demonstrated because of fabrication difficulties and irreversible switching failure caused by surface adhesion. Here, we report the sub-1 V operation of a NEM switch through the introduction of a novel pipe clip device structure and an effective air gap fabrication technique. This achievement is primarily attributed to the incorporation of a 4-nm-thick air gap, which is the smallest reported so far for a NEM switch generated using a `top-down' approach. Our structure and process can potentially be utilized in various nanogap-related applications, including NEM switch-based ultralow-power integrated circuits, NEM resonators, nanogap electrodes for scientific research and sensors.

  13. Learner Code-Switching versus English Only

    Science.gov (United States)

    Sampson, Andrew

    2012-01-01

    This article describes a study into the functions of code-switching in EFL classes at a Colombian language school. It was undertaken to decide whether the official "English-only" policy in place in this and other classrooms is pedagogically justified. The results suggest that code-switching may not necessarily be connected to ability level and…

  14. Proceedings of the switched power workshop

    International Nuclear Information System (INIS)

    These proceedings contain most of the presentations given at a workshop on the current state of research in techniques for switched power acceleration. The proceedings are divided, as was the workshop itself, into two parts. Part 1, contains the latest results from a number of groups active in switched power research. The major topic here is a method for switching externally supplied power onto a transmission line. Advocates for vacuum photodiode switching, solid state switching, gas switching, and synthetic pulse generation are all presented. Other important areas of research described in this section concern: external electrical and laser pulsing systems; the properties of the created electromagnetic pulse; structures used for transporting the electromagnetic pulse to the region where the electron beam is located; and possible applications. Part 2 of the proceedings considers the problem of designing a high brightness electron gun using switched power as the power source. This is an important first step in demonstrating the usefulness of switched power techniques for accelerator physics. In addition such a gun could have immediate practical importance for advanced acceleration studies since the brightness could exceed that of present sources by several orders of magnitude. I would like to take this opportunity to thank Kathleen Tuohy and Patricia Tuttle for their assistance in organizing and running the workshop. Their tireless efforts contribute greatly to a very productive meeting

  15. Ultrafast Directional Beam Switching in Coupled VCSELs

    Science.gov (United States)

    Ning, Cun-Zheng; Goorjian, Peter

    2001-01-01

    We propose a new approach to performing ultrafast directional beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The proposed strategy is demonstrated for two VCSELs of 5.6 microns in diameter placed about 1 micron apart from the edges, showing a switching speed of 42 GHz with a maximum far-field angle span of about 10 degrees.

  16. Ultrafast pulse generation in photoconductive switches

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Dykaar, D. R.

    1996-01-01

    Carrier and field dynamics in photoconductive switches are investigated by electrooptic sampling and voltage-dependent reflectivity measurements. We show that the nonuniform field distribution due to the two-dimensional nature of coplanar photoconductive switches, in combination with the large di...

  17. Stability of stochastic switched SIRS models

    Science.gov (United States)

    Meng, Xiaoying; Liu, Xinzhi; Deng, Feiqi

    2011-11-01

    Stochastic stability problems of a stochastic switched SIRS model with or without distributed time delay are considered. By utilizing the Lyapunov methods, sufficient stability conditions of the disease-free equilibrium are established. Stability conditions about the subsystem of the stochastic switched SIRS systems are also obtained.

  18. Internal Backpressure for Terabit Switch Fabrics

    DEFF Research Database (Denmark)

    Fagertun, Anna Manolova; Ruepp, Sarah Renée; Rytlig, Andreas; Berger, Michael Stübert; Wessing, Henrik; Dittmann, Lars

    2012-01-01

    This paper proposes and analyzes the efficiency of novel backpressure schemes for Terabit switch fabrics. The proposed schemes aim at buffer optimization under uniform traffic distribution with Bernoulli packet arrival process. Results show that a reduction of the needed maximum buffer capacity...... with up to 47% can be achieved with switch-internal backpressure mechanisms at the expense of a small control overhead....

  19. Code switching for college students on campus

    Institute of Scientific and Technical Information of China (English)

    张勇

    2015-01-01

    <正>I.Introduction In linguistics,code-switching is the concurrent use of more than one language,or language variety,in discourse.Code-switching is a worldwide linguistic phenomenon existing in bilingual or multilingual communities.College students in China,after years of English learning,are bilingually competent underlying codeswitching between Chinese and English.Studies or research

  20. Low-Voltage Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Bidari, E.; Keskin, M.; Maloberti, F.;

    1999-01-01

    Switched-capacitor stages are described which can function with very low (typically 1 V) supply voltages, without using voltage boosting or switched op-amps. Simulations indicate that high performance may be achieved using these circuits in filter or data converter applications....

  1. Efficiency switching-mode power supply

    International Nuclear Information System (INIS)

    A switching-mode, blocking oscillator based power supply employs proportional base drive and an improved design of rise-time suppression to improve effeciency and reliability. Current limiting elements cooperate with pass transistor control circuits to provide abrupt and power-efficient primary circuit switching

  2. On formalism and stability of switched systems

    DEFF Research Database (Denmark)

    Leth, John-Josef; Wisniewski, Rafal

    2012-01-01

    In this paper, we formulate a uniform mathematical framework for studying switched systems with piecewise linear partitioned state space and state dependent switching. Based on known results from the theory of differential inclusions, we devise a Lyapunov stability theorem suitable for this class...

  3. Proceedings of the switched power workshop

    Energy Technology Data Exchange (ETDEWEB)

    Fernow, R.C. (ed.)

    1988-01-01

    These proceedings contain most of the presentations given at a workshop on the current state of research in techniques for switched power acceleration. The proceedings are divided, as was the workshop itself, into two parts. Part 1, contains the latest results from a number of groups active in switched power research. The major topic here is a method for switching externally supplied power onto a transmission line. Advocates for vacuum photodiode switching, solid state switching, gas switching, and synthetic pulse generation are all presented. Other important areas of research described in this section concern: external electrical and laser pulsing systems; the properties of the created electromagnetic pulse; structures used for transporting the electromagnetic pulse to the region where the electron beam is located; and possible applications. Part 2 of the proceedings considers the problem of designing a high brightness electron gun using switched power as the power source. This is an important first step in demonstrating the usefulness of switched power techniques for accelerator physics. In addition such a gun could have immediate practical importance for advanced acceleration studies since the brightness could exceed that of present sources by several orders of magnitude. I would like to take this opportunity to thank Kathleen Tuohy and Patricia Tuttle for their assistance in organizing and running the workshop. Their tireless efforts contribute greatly to a very productive meeting.

  4. Integrated photonic switches for nanosecond packet-switched optical wavelength conversion

    Science.gov (United States)

    Fidaner, Onur; Demir, Hilmi Volkan; Sabnis, Vijit A.; Zheng, Jun-Fei; Harris, James S., Jr.; Miller, David A. B.

    2006-01-01

    We present a multifunctional photonic switch that monolithically integrates an InGaAsP/InP quantum well electroabsorption modulator and an InGaAs photodiode as a part of an on-chip, InP optoelectronic circuit. The optical multifunctionality of the switch offers many configurations to allow for different optical network functions on a single chip. Here we experimentally demonstrate GHz-range optical wavelength-converting switching with only ~10 mW of absorbed input optical power, electronically controlled packet switching with a reconfiguration time of switching in <300 ps.

  5. Transcriptional regulation of cardiac genes balance pro- and anti-hypertrophic mechanisms in hypertrophic cardiomyopathy

    OpenAIRE

    Nina Gennebäck; Gerhard Wikström; Urban Hellman; Jane-Lise Samuel; Anders Waldenström; Stellan Mörner

    2012-01-01

    Hypertrophic cardiomyopathy (HCM) is characterized by unexplained left ventricular hypertrophy. HCM is often hereditary, but our knowledge of the mechanisms leading from mutation to phenotype is incomplete. The transcriptional expression patterns in the myocar - dium of HCM patients may contribute to understanding the mechanisms that drive and stabilize the hypertrophy. Cardiac myectomies/biopsies from 8 patients with hypertrophic obstructive cardiomyopathy (HOCM) and 5 controls were studied ...

  6. Electrical switching of an antiferromagnet

    Science.gov (United States)

    Wadley, P.; Howells, B.; Železný, J.; Andrews, C.; Hills, V.; Campion, R. P.; Novák, V.; Olejník, K.; Maccherozzi, F.; Dhesi, S. S.; Martin, S. Y.; Wagner, T.; Wunderlich, J.; Freimuth, F.; Mokrousov, Y.; Kuneš, J.; Chauhan, J. S.; Grzybowski, M. J.; Rushforth, A. W.; Edmonds, K. W.; Gallagher, B. L.; Jungwirth, T.

    2016-02-01

    Antiferromagnets are hard to control by external magnetic fields because of the alternating directions of magnetic moments on individual atoms and the resulting zero net magnetization. However, relativistic quantum mechanics allows for generating current-induced internal fields whose sign alternates with the periodicity of the antiferromagnetic lattice. Using these fields, which couple strongly to the antiferromagnetic order, we demonstrate room-temperature electrical switching between stable configurations in antiferromagnetic CuMnAs thin-film devices by applied current with magnitudes of order 106 ampere per square centimeter. Electrical writing is combined in our solid-state memory with electrical readout and the stored magnetic state is insensitive to and produces no external magnetic field perturbations, which illustrates the unique merits of antiferromagnets for spintronics.

  7. Pressure-induced conformational switch of an interfacial protein.

    Science.gov (United States)

    Johnson, Quentin R; Lindsay, Richard J; Nellas, Ricky B; Shen, Tongye

    2016-06-01

    A special class of proteins adopts an inactive conformation in aqueous solution and activates at an interface (such as the surface of lipid droplet) by switching their conformations. Lipase, an essential enzyme for breaking down lipids, serves as a model system for studying such interfacial proteins. The underlying conformational switch of lipase induced by solvent condition is achieved through changing the status of the gated substrate-access channel. Interestingly, a lipase was also reported to exhibit pressure activation, which indicates it is drastically active at high hydrostatic pressure. To unravel the molecular mechanism of this unusual phenomenon, we examined the structural changes induced by high hydrostatic pressures (up to 1500 MPa) using molecular dynamics simulations. By monitoring the width of the access channel, we found that the protein undergoes a conformational transition and opens the access channel at high pressures (>100 MPa). Particularly, a disordered amphiphilic α5 region of the protein becomes ordered at high pressure. This positive correlation between the channel opening and α5 ordering is consistent with the early findings of the gating motion in the presence of a water-oil interface. Statistical analysis of the ensemble of conformations also reveals the essential collective motions of the protein and how these motions contribute to gating. Arguments are presented as to why heightened sensitivity to high-pressure perturbation can be a general feature of switchable interfacial proteins. Further mutations are also suggested to validate our observations. Proteins 2016; 84:820-827. © 2016 Wiley Periodicals, Inc. PMID:26967808

  8. Asymmetric switching in a homodimeric ABC transporter: a simulation study.

    Directory of Open Access Journals (Sweden)

    Jussi Aittoniemi

    2010-04-01

    Full Text Available ABC transporters are a large family of membrane proteins involved in a variety of cellular processes, including multidrug and tumor resistance and ion channel regulation. Advances in the structural and functional understanding of ABC transporters have revealed that hydrolysis at the two canonical nucleotide-binding sites (NBSs is co-operative and non-simultaneous. A conserved core architecture of bacterial and eukaryotic ABC exporters has been established, as exemplified by the crystal structure of the homodimeric multidrug exporter Sav1866. Currently, it is unclear how sequential ATP hydrolysis arises in a symmetric homodimeric transporter, since it implies at least transient asymmetry at the NBSs. We show by molecular dynamics simulation that the initially symmetric structure of Sav1866 readily undergoes asymmetric transitions at its NBSs in a pre-hydrolytic nucleotide configuration. MgATP-binding residues and a network of charged residues at the dimer interface are shown to form a sequence of putative molecular switches that allow ATP hydrolysis only at one NBS. We extend our findings to eukaryotic ABC exporters which often consist of two non-identical half-transporters, frequently with degeneracy substitutions at one of their two NBSs. Interestingly, many residues involved in asymmetric conformational switching in Sav1866 are substituted in degenerate eukaryotic NBS. This finding strengthens recent suggestions that the interplay of a consensus and a degenerate NBS in eukaroytic ABC proteins pre-determines the sequence of hydrolysis at the two NBSs.

  9. Environmental Qualification of an Actuator Torque Switch

    International Nuclear Information System (INIS)

    Environmental qualification testing was performed on a modified Limitorque torque switch for the torque switch safety functions in the Limitorque type SMB actuators located inside and outside containment in a nuclear power plant. The torque switch specimen was installed in a Limitorque SMB-1 electric actuator mounted on an 8'' Velan gate valve and operated with a customized programmable logic controller to allow normal torque switch behaviour to be observed. The present paper describes the qualification testing performed. The modified torque switch was aged to a 30-year service life at the normal service conditions for both inside and outside containment. Aging included radiation, thermal and cycle aging. A seismic test and then a combined Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) steam accident simulation were followed. After each stage of aging, functional tests were done to confirm normal insulation resistance, normal contact resistance and normal operation. (authors)

  10. Commentary on strategies for switching antipsychotics

    Directory of Open Access Journals (Sweden)

    Leucht Stefan

    2008-06-01

    Full Text Available Abstract Both the new generation of antipsychotics and the more traditional antipsychotic drugs produce an important and meaningful improvement in patients with schizophrenia, but most patients are neither cured nor free of symptoms. As a consequence, it is common to switch from one drug to another in the hope of obtaining a better response. All antipsychotic drugs produce some side effects, so switching can also be a tolerance issue. There are reports in the literature on the tactics of switching: abrupt discontinuation, cross tapering, starting a patient on a new drug while continuing with the old drug until the new drug has reached a steady state, or some variation on these tactics. In this issue, Ganguli et al. have carried out a randomized switching study, the data from which indicates the tactics that might be optimal. We put this paper into context, provide a critique and describe indications for switching.

  11. Nanoscale resistive switching devices: mechanisms and modeling.

    Science.gov (United States)

    Yang, Yuchao; Lu, Wei

    2013-11-01

    Resistive switching devices (also termed memristive devices or memristors) are two-terminal nonlinear dynamic electronic devices that can have broad applications in the fields of nonvolatile memory, reconfigurable logic, analog circuits, and neuromorphic computing. Current rapid advances in memristive devices in turn demand better understanding of the switching mechanism and the development of physics-based as well as simplified device models to guide future device designs and circuit-level applications. In this article, we review the physical processes behind resistive switching (memristive) phenomena and discuss the experimental and modeling efforts to explain these effects. In this article three categories of devices, in which the resistive switching effects are driven by cation migration, anion migration, and electronic effects, will be discussed. The fundamental driving forces and the stochastic nature of resistive switching will also be discussed. PMID:24057010

  12. Switched-capacitor isolated LED driver

    Energy Technology Data Exchange (ETDEWEB)

    Sanders, Seth R.; Kline, Mitchell

    2016-03-22

    A switched-capacitor voltage converter which is particularly well-suited for receiving a line voltage from which to drive current through a series of light emitting diodes (LEDs). Input voltage is rectified in a multi-level rectifier network having switched capacitors in an ascending-bank configuration for passing voltages in uniform steps between zero volts up to full received voltage V.sub.DC. A regulator section, operating on V.sub.DC, comprises switched-capacitor stages of H-bridge switching and flying capacitors. A current controlled oscillator drives the states of the switched-capacitor stages and changes its frequency to maintain a constant current to the load. Embodiments are described for isolating the load from the mains, utilizing an LC tank circuit or a multi-primary-winding transformer.

  13. Microwave switching power divider. [antenna feeds

    Science.gov (United States)

    Stockton, R. J.; Johnson, R. W. (Inventor)

    1981-01-01

    A pair of parallel, spaced-apart circular ground planes define a microwave cavity with multi-port microwave power distributing switching circuitry formed on opposite sides of a thin circular dielectric substrate disposed between the ground planes. The power distributing circuitry includes a conductive disk located at the center of the substrate and connected to a source of microwave energy. A high speed, low insertion loss switching diode and a dc blocking capacitor are connected in series between the outer end of a transmission line and an output port. A high impedance, microwave blocking dc bias choke is connected between each switching diode and a source of switching current. The switching source forward biases the diodes to couple microwave energy from the conductive disk to selected output ports and, to associated antenna elements connected to the output ports to form a synthesized antenna pattern.

  14. Code Switching in the Lexical Corpora of Children

    OpenAIRE

    B. A. Mahalakshmi Prasad; Prema K. S. Rao

    2011-01-01

    Code switching is the hallmark of communication in a multilingual society. Code switching occurs in everyday speech at words, morphemes sentence and discourse levels. There are varied perspectives on the phenomenon of code switching where linguists have viewed code switching as inevitable in a plurilingual situation. Few believe that code switching helps to express meanings more precisely, others believe that code switching vitiates a language, rather than enhance the communication between in...

  15. Design & Implementation of Zero Voltage Switching Buck Converter

    OpenAIRE

    A.Suresh Kumar; P.Krishna Reddy

    2014-01-01

    Zero voltage switching (ZVS) buck converter is more preferable over hard switched buck converter for low power, high frequency DC-DC conversion applications. In Zero voltage switching converter, turn on & turn off of a switch occurs at zero voltage that results in lower switching losses. In this converter soft switching is achieved by using resonant components. The optimal values of resonant components are determined by using electric functions derived from circuit configurati...

  16. Stabilization of a class of switched nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The stabilization of a class of switched nonlinear systems is investigated in the paper. The systems concerned are of (generalized) switched Byrnes-Isidori canonical form, which has all switched models in (generalized) ByrnesIsidori canonical form. First, a stability result of switched systems is obtained. Then it is used to solve the stabilization problem of the switched nonlinear control systems. In addition, necessary and sufficient conditions are obtained for a switched affine nonlinear system to be feedback equivalent to (generalized) switched Byrnes-Isidori canonical systems are presented.Finally, as an application the stability of switched lorenz systems is investigated.

  17. Global exponential synchronization criterion for switched linear coupled dynamic networks

    International Nuclear Information System (INIS)

    We in this paper develop a global exponential synchronization stability criterion for switched linear coupled network. By introducing a switching symmetric matrix, we prove that the stability of global exponential synchronization is governed by the largest eigenvalue of this switching symmetric matrix and the largest switching coupling strength. Meanwhile, we give the threshold of switching coupling strength which can make the switched linear network reach global exponential synchronization. Because the proposed criterion is on the basis of the original synchronization definition and the largest eigenvalue of the switching symmetric matrix, therefore, it is convenient to use in verifying global exponential synchronization of dynamic network with switching linear couplings.

  18. Bipolar resistive switching based on bis(8-hydroxyquinoline) cadmium complex: Mechanism and non-volatile memory application

    Science.gov (United States)

    Wang, Ying; Yang, Ting; Xie, Ji-Peng; Lü, Wen-Li; Fan, Guo-Ying; Liu, Su

    2013-07-01

    Stable and persistent bipolar resistive switching was observed in an organic diode with the structure of indium-tin oxide (ITO)/bis(8-hydroxyquinoline) cadmium (Cdq2)/Al. Aggregate formation and electric field driven trapping and de-trapping of charge carriers in the aggregate states that lie in the energy gap of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the organic molecule were proposed as the mechanism of the observed bipolar resistive switching, and this was solidly supported by the results of AFM investigations. Repeatedly set, read, and reset measurements demonstrated that the device is potentially applicable in non-volatile memories.

  19. Bipolar resistive switching based on bis(8-hydroxyquinoline) cadmium complex: Mechanism and non-volatile memory application

    International Nuclear Information System (INIS)

    Stable and persistent bipolar resistive switching was observed in an organic diode with the structure of indium-tin oxide (ITO)/bis(8-hydroxyquinoline) cadmium (Cdq2)/Al. Aggregate formation and electric field driven trapping and de-trapping of charge carriers in the aggregate states that lie in the energy gap of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the organic molecule were proposed as the mechanism of the observed bipolar resistive switching, and this was solidly supported by the results of AFM investigations. Repeatedly set, read, and reset measurements demonstrated that the device is potentially applicable in non-volatile memories

  20. Resistance switching memory in perovskite oxides

    International Nuclear Information System (INIS)

    The resistance switching behavior has recently attracted great attentions for its application as resistive random access memories (RRAMs) due to a variety of advantages such as simple structure, high-density, high-speed and low-power. As a leading storage media, the transition metal perovskite oxide owns the strong correlation of electrons and the stable crystal structure, which brings out multifunctionality such as ferroelectric, multiferroic, superconductor, and colossal magnetoresistance/electroresistance effect, etc. The existence of rich electronic phases, metal–insulator transition and the nonstoichiometric oxygen in perovskite oxide provides good platforms to insight into the resistive switching mechanisms. In this review, we first introduce the general characteristics of the resistance switching effects, the operation methods and the storage media. Then, the experimental evidences of conductive filaments, the transport and switching mechanisms, and the memory performances and enhancing methods of perovskite oxide based filamentary RRAM cells have been summarized and discussed. Subsequently, the switching mechanisms and the performances of the uniform RRAM cells associating with the carrier trapping/detrapping and the ferroelectric polarization switching have been discussed. Finally, the advices and outlook for further investigating the resistance switching and enhancing the memory performances are given

  1. Reluctance motor employing superconducting magnetic flux switches

    International Nuclear Information System (INIS)

    This paper reports that superconducting flux switches controlling the magnetic flux in the poles of a motor will enable the implementation of a reluctance motor using one central single phase winding. A superconducting flux switch consists of a ring of superconducting material surrounding a ferromagnetic pole of the motor. When in the superconducting state the switch will block all magnetic flux attempting to flow in the ferromagnetic core. When switched to the normal state the superconducting switch will allow the magnetic flux to flow freely in that pole. By using one high turns-count coil as a flux generator, and selectively channeling flux among the various poles using the superconducting flux switch, 3-phase operation can be emulated with a single-hase central AC source. The motor will also operate when the flux generating coil is driven by a DC current, provided the magnetic flux switches see a continuously varying magnetic flux. Rotor rotation provides this varying flux due to the change in stator pole inductance it produces

  2. Switching from natalizumab to fingolimod

    Science.gov (United States)

    Radue, Ernst-Wilhelm; Comi, Giancarlo; Montalban, Xavier; Butzkueven, Helmut; Wiendl, Heinz; Giovannoni, Gavin; Hartung, Hans-Peter; Derfuss, Tobias; Naegelin, Yvonne; Sprenger, Till; Mueller-Lenke, Nicole; Griffiths, Sarah; von Rosenstiel, Philipp; Gottschalk, Rebecca; Zhang, Ying; Dahlke, Frank; Tomic, Davorka

    2015-01-01

    Objective: To investigate the effect of different natalizumab washout (WO) periods on recurrence of MRI and clinical disease activity in patients switching from natalizumab to fingolimod. Methods: In this multicenter, double-blind, placebo-controlled trial (TOFINGO), patients with relapsing-remitting multiple sclerosis (RRMS) were randomized 1:1:1 to 8-, 12-, or 16-week WO followed by fingolimod treatment over 32 weeks from last natalizumab infusion (LNI). Brain MRI was performed at baseline and weeks 8, 12, 16, 20, and 24. Results: Of 142 enrolled and randomized patients, 112 (78.9%) completed the study (8 weeks, n = 41/50; 12 weeks, n = 31/42; 16 weeks, n = 40/50). Number (95% confidence interval [CI]) of active (new/newly enlarged T2) lesions from LNI through 8 weeks of fingolimod treatment (primary outcome) was similar in the 8-week (2.1 [1.7–2.6]) and 12-week WO groups (1.7 [1.3–2.2]) and higher in the 16-week WO group (8.2 [7.3–9.1]). During the WO period only, the number (95% CI) of active lesions increased with increasing WO duration (8 weeks, 0.4 [0.2–0.6]; 12 weeks, 2.1 [1.6–2.6]; 16 weeks, 3.6 [3.0–4.2]). Over the 24 weeks from LNI, gadolinium-enhancing T1 lesion counts were lower in the 8-week WO group (14.1 [5.67–22.53]) than in the 12-week (21.3 [1.41–41.19]) or 16-week (18.5 [8.40–28.60]) WO groups. More patients were relapse-free in the 8-week (88%) and 12-week (91%) WO groups than the 16-week WO group (84%). Sixty-eight percent of patients experienced adverse events (mostly mild/moderate), with similar incidence across groups. No unusually severe relapses or opportunistic infections occurred. Conclusions: Initiating fingolimod therapy 8–12 weeks after natalizumab discontinuation is associated with a lower risk of MRI and clinical disease reactivation than initiation after 16-week WO. Classification of evidence: This study provides Class II evidence that for patients with RRMS switching from natalizumab to fingolimod, shorter

  3. 160-Gb/s Silicon All-Optical Packet Switch for Buffer-less Optical Burst Switching

    DEFF Research Database (Denmark)

    Hu, Hao; Ji, Hua; Pu, Minhao;

    2015-01-01

    We experimentally demonstrate a 160-Gb/s Ethernet packet switch using an 8.6-mm-long silicon nanowire for optical burst switching, based on cross phase modulation in silicon. One of the four packets at the bit rate of 160 Gb/s is switched by an optical control signal using a silicon based 1 × 1 all......-optical packet switch. Error free performance (BER <1E-9) is achieved for the switched packet. The use of optical burst switching protocols could eliminate the need for optical buffering in silicon packet switch based optical burst switching, which might be desirable for high-speed interconnects within a short...

  4. Consumer poaching, brand switching, and price transparency

    DEFF Research Database (Denmark)

    Schultz, Christian

    2014-01-01

    This paper addresses price transparency on the consumer side in markets with behavioral price discrimination which feature welfare reducing brand switching. When long-term contracts are not available, an increase in transparency intensifies competition, lowers prices and profits, reduces brand...... switching and benefits consumers and welfare. With long-term contracts, an increase in transparency reduces the use of long-term contracts, leading to more brand switching and a welfare loss. Otherwise, the results are the same as without long-term contracts....

  5. Design of a switched reluctance generator

    Energy Technology Data Exchange (ETDEWEB)

    Heese, T.; Pyrhoenen, J.

    1996-12-31

    This report presents the design of a low voltage switched reluctance generator for variable speed applications showing the design of its construction and commutation unit. For the realisation of the control system the control strategy is presented. The principle and the theory of switched reluctance generators are described in this context. Also an overview of existing generator technology for these applications is given. The results gained suggest that switched reluctance machines can also advantageously be used as generators if the generating operation is considered within the design process. Compared with the existing technology a higher output power and efficiency is reached over the whole speed range. (orig.)

  6. Active plasmonics in WDM traffic switching applications

    DEFF Research Database (Denmark)

    Papaioannou, S.; Kalavrouziotis, D.; Vyrsokinos, K.;

    2012-01-01

    introduce active plasmonics into Wavelength Division Multiplexed (WDM) switching applications, using the smallest TO DLSPP-based Mach-Zehnder interferometric switch reported so far and showing its successful performance in 4310 Gb/s low-power and fast switching operation. The demonstration of the WDM......-enabling characteristics of active plasmonic circuits with an ultra-low power 3 response time product represents a crucial milestone in the development of active plasmonics towards real telecom and datacom applications, where low-energy and fast TO operation with small-size circuitry is targeted....

  7. Electromagnetically induced switching of ferroelectric thin films

    International Nuclear Information System (INIS)

    We analyze the interaction of an electromagnetic spike (one cycle) with a thin layer of ferroelectric medium with two equilibrium states. The model is the set of Maxwell equations coupled to the undamped Landau-Khalatnikov equation, where we do not assume slowly varying envelopes. From linear-scattering theory, we show that low-amplitude pulses can be completely reflected by the medium. Large-amplitude pulses can switch the ferroelectric. Using numerical simulations and analysis, we study this switching for long and short pulses, estimate the switching times, and provide useful information for experiments

  8. Quantum cryptography without switching of measurement basis

    International Nuclear Information System (INIS)

    Full text: Quantum cryptography is a form of secret communication between two parties that guarantees absolute security. The original quantum cryptography scheme was developed in 1984 which utilised discrete variables while a continuous variable version was conceived in 1999. One common step of both these protocols involves the random switching of measurement bases by one party. We present a new continuous variable quantum cryptography protocol that does not require random switching. Furthermore we show that the elimination of switching results in a significantly higher secret key rate than any other known quantum cryptographic protocol. Copyright (2005) Australian Institute of Physics

  9. Switching to a Mac For Dummies

    CERN Document Server

    Reinhold, Arnold

    2011-01-01

    Learn how to make the switch from PC to Mac a completely smooth transition The number of Mac users continues to increase significantly each year. If you are one of those people and are eager but also anxious about making the switch, then fear not! This friendly guide skips the jargon to deliver you an easy-to-read, understandable introduction to the Macintosh computer. Computer guru Arnold Reinhold walks you through the Mac OS, user interface, and icons. You'll learn how to set up your Mac, move your files from your PC to your Mac, switch applications, get your Mac online, network your Mac, se

  10. Digital Switching in the Quantum Domain

    OpenAIRE

    Tsai, I. M.; Kuo, S.Y.

    2002-01-01

    In this paper, we present an architecture and implementation algorithm such that digital data can be switched in the quantum domain. First we define the connection digraph which can be used to describe the behavior of a switch at a given time, then we show how a connection digraph can be implemented using elementary quantum gates. The proposed mechanism supports unicasting as well as multicasting, and is strict-sense non-blocking. It can be applied to perform either circuit switching or packe...

  11. Optically switchable molecular device using microsphere based junctions

    Science.gov (United States)

    Faramarzi, V.; Raimondo, C.; Reinders, F.; Mayor, M.; Samorı, P.; Doudin, B.

    2011-12-01

    Metallic planar electrodes are bridged using microspheres coated with chemisorbed azobenzene self-assembled monolayers. The circuit exhibits light-induced switching, with reproducibility over 90%, as statistically determined and compared to junctions incorporating photo-insensitive alkanethiol layers. Microsphere interconnects provide direct access to molecular transport properties, with reliability and stability, making multifunctional molecular electronics devices possible.

  12. The role of phenotypic switching in the basic biology and pathogenesis of Candida albicans

    Directory of Open Access Journals (Sweden)

    David R. Soll

    2014-01-01

    Full Text Available The “white-opaque” transition in Candida albicans was discovered in 1987. For the next fifteen years, a significant body of knowledge accumulated that included differences between the cell types in gene expression, cellular architecture and virulence in cutaneous and systemic mouse models. However, it was not until 2002 that we began to understand the role of switching in the life history of this pathogen, the role of the mating type locus and the molecular pathways that regulated it. Then in 2006, both the master switch locus WORI and the pheromone-induced white cell biofilm were discovered. Since that year, a number of new observations on the regulation and biology of switching have been made that have significantly increased the perceived complexity of this fascinating phenotypic transition.

  13. Resistive switching behaviour of highly epitaxial CeO2 thin film for memory application

    International Nuclear Information System (INIS)

    We report on the remarkable potential of highly epitaxial and pure (001)-oriented CeO2 thin films grown on conducting Nb-doped SrTiO3 (NSTO) substrates by laser molecular beam epitaxy for nonvolatile memory application. Resistive switching (RS) devices with the structure of Au/epi-CeO2/NSTO exhibit reversible and steady bipolar RS behaviour with large high/low resistance ratio and a narrow dispersion of the resistance values. Detailed analysis of the conduction mechanisms reveals that the trapping/detrapping processes and oxygen vacancies migration play important roles in the switching behaviour. In the light of XPS measurement results, the CeO2/NSTO interface with oxygen vacancies or defects is responsible for the RS effect. Furthermore, a model is proposed to explain this resistance switching behaviour. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Final report: Photochromism as a switching mechanism for electronically active organic materials

    Energy Technology Data Exchange (ETDEWEB)

    Pollagi, T.P.; Sinclair, M.B. [Sandia National Labs., Albuquerque, NM (United States). Electronic and Optical Materials Dept.; Jacobs, S.J. [Texas Instruments Inc., Dallas, TX (United States)

    1997-07-01

    Recent discoveries in the field of conjugated polymers in environmental stability, regiochemical regularity, and electrical conductivity, particularly of polythiophene and polyaniline, have intensified interest in device applications. Present or anticipated applications include development of electrical circuitry on a molecular scale, as well as conducting and semiconducting materials for a variety of applications including thin film transistors and batteries. The authors have investigated a series of compounds comprising conjugated segments coupled to photochromic elements. The photochromic reaction in these compounds reversibly alters the conjugation length and provides a mechanism for switching both the electrical and optical properties of these materials. The authors are currently investigating the nature and scope of this switching mechanism and preparing extended materials that take advantage of this novel form of switching behavior. Preparation and photochromic behavior of several of these materials are described.

  15. Plasma opening switch conduction scaling

    International Nuclear Information System (INIS)

    Plasma opening switch (POS) experiments performed on the Hawk generator [Commisso et al., Phys. Fluids B 4, 2368 (1992)] (750 kA, 1.2 μs) determine the dependence of the conduction current and conduction time on plasma density, electrode dimensions, and current rise rate. The experiments indicate that for a range of parameters, conduction is controlled by magnetohydrodynamic (MHD) distortion of the plasma, resulting in a low density region where opening can occur, possibly by erosion. The MHD distortion corresponds to an axial translation of the plasma center-of-mass by half the initial plasma length, leading to a simple scaling relation between the conduction current and time, and the injected plasma density and POS electrode dimensions that is applicable to a large number of POS experiments. For smaller currents and conduction times, the Hawk data suggest a non-MHD conduction limit that may correspond to electromagnetohydrodynamic (EMH) field penetration through the POS plasma. copyright 1995 American Institute of Physics

  16. PERFORMANCE COMPARISON OF CELL-BASED AND PACKET-BASED SWITCHING SCHEMES FOR SHARED MEMORY SWITCHES

    Institute of Scientific and Technical Information of China (English)

    Xi Kang; Ge Ning; Feng Chongxi

    2004-01-01

    Shared Memory (SM) switches are widely used for its high throughput, low delay and efficient use of memory. This paper compares the performance of two prominent switching schemes of SM packet switches: Cell-Based Switching (CBS) and Packet-Based Switching (PBS).Theoretical analysis is carried out to draw qualitative conclusion on the memory requirement,throughput and packet delay of the two schemes. Furthermore, simulations are carried out to get quantitative results of the performance comparison under various system load, traffic patterns,and memory sizes. Simulation results show that PBS has the advantage of shorter time delay while CBS has lower memory requirement and outperforms in throughput when the memory size is limited. The comparison can be used for tradeoff between performance and complexity in switch design.

  17. Frequency-dependence of the switching voltage in electronic switching of Pt-dispersed SiO2 thin films

    Science.gov (United States)

    Choi, Byung Joon; Chen, I.-Wei

    2016-06-01

    The switching time-voltage dependence of electronic resistive switching was studied for understanding the switching dynamics in Pt-dispersed SiO2 thin film devices. Trapezoidal voltage pulses with opposite polarities were consecutively introduced and thereby transient on-switching and offswitching were examined. A prior on-switching voltage determines the off-switching voltage regardless of the sweeping rate of the pulse for the prior on-switching. However, the off-switching voltage was sensitive to the sweeping rate of the subsequent pulses for off-switching. The frequencydependent impedance of both the device and the surrounding circuit element are thought to result in the variation of the off-switching voltage; otherwise, the switching voltage is independent of time.

  18. Nano- and micro-electromechanical switch dynamics

    International Nuclear Information System (INIS)

    This paper reports theoretical analysis and experimental results on the dynamics of piezoelectric MEMS mechanical logic relays. The multiple degree of freedom analytical model, based on modal decomposition, utilizes modal parameters obtained from finite element analysis and an analytical model of piezoelectric actuation. The model accounts for exact device geometry, damping, drive waveform variables, and high electric field piezoelectric nonlinearity. The piezoelectrically excited modal force is calculated directly and provides insight into design optimization for switching speed. The model accurately predicts the propagation delay dependence on actuation voltage of mechanically distinct relay designs. The model explains the observed discrepancies in switching speed of these devices relative to single degree of freedom switching speed models and suggests the strong potential for improved switching speed performance in relays designed for mechanical logic and RF circuits through the exploitation of higher order vibrational modes. (paper)

  19. Protection Switching and Rerouting in MPLS

    Directory of Open Access Journals (Sweden)

    S. Veni

    2012-01-01

    Full Text Available Multi-protocol Label Switching (MPLS has become an attractive technology of choice for Internet backbone service providers. MPLS recovery mechanisms are increasing in popularity because they can guarantee fast restoration and high QoS assurance. To provide dependable services MPLS networks make use of a set of procedures (detection, notification and fault recovery which seek to ensure appropriate protection for the traffic carried in the label switched paths (LSPs. When a fault happens in the active LSP, the recovery scheme must re-direct the traffic to a recovery path (the protection LSP or recovery LSP which bypasses the fault. The two basic recovery models used to redirect traffic are rerouting and protection switching. Protection switching is faster than rerouting but cannot handle simultaneous faults in the active and the recovery path. On the other hand, rerouting is generally slow, and cannot offer QoS guaranties upon failure, but can use resources in a more efficient way

  20. Implementation of Middleware Switch ASIC Processor

    Directory of Open Access Journals (Sweden)

    S. Montenegro

    2012-11-01

    Full Text Available The new spacecraft area network (SCAN system for internal satellite communication provides data transfer between different satellite components. The satellite components have their own communication protocols, which are translated by middleware (MW switch processor into a universal middleware protocol, understandable for the satellite operating system. The MW switch processor is the main part of a new proposed approach. Instead of current board computer based systems, the new data transfer approach based on network provides a more reliable solution. The processor is fabricated in the 250 nm IHP technology. This paper introduces a description of MW switch architecture, a comparison between possible architecture approaches and the characteristics of the implemented MW Switch processor.

  1. Multistate resistive switching in silver nanoparticle films

    Science.gov (United States)

    Sandouk, Eric J.; Gimzewski, James K.; Stieg, Adam Z.

    2015-08-01

    Resistive switching devices have garnered significant consideration for their potential use in nanoelectronics and non-volatile memory applications. Here we investigate the nonlinear current-voltage behavior and resistive switching properties of composite nanoparticle films comprising a large collective of metal-insulator-metal junctions. Silver nanoparticles prepared via the polyol process and coated with an insulating polymer layer of tetraethylene glycol were deposited onto silicon oxide substrates. Activation required a forming step achieved through application of a bias voltage. Once activated, the nanoparticle films exhibited controllable resistive switching between multiple discrete low resistance states that depended on operational parameters including the applied bias voltage, temperature and sweep frequency. The films’ resistance switching behavior is shown here to be the result of nanofilament formation due to formative electromigration effects. Because of their tunable and distinct resistance states, scalability and ease of fabrication, nanoparticle films have a potential place in memory technology as resistive random access memory cells.

  2. Delayed switching applied to memristor neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Frank Z.; Yang Xiao; Lim Guan [Future Computing Group, School of Computing, University of Kent, Canterbury (United Kingdom); Helian Na [School of Computer Science, University of Hertfordshire, Hatfield (United Kingdom); Wu Sining [Xyratex, Havant (United Kingdom); Guo Yike [Department of Computing, Imperial College, London (United Kingdom); Rashid, Md Mamunur [CERN, Geneva (Switzerland)

    2012-04-01

    Magnetic flux and electric charge are linked in a memristor. We reported recently that a memristor has a peculiar effect in which the switching takes place with a time delay because a memristor possesses a certain inertia. This effect was named the ''delayed switching effect.'' In this work, we elaborate on the importance of delayed switching in a brain-like computer using memristor neural networks. The effect is used to control the switching of a memristor synapse between two neurons that fire together (the Hebbian rule). A theoretical formula is found, and the design is verified by a simulation. We have also built an experimental setup consisting of electronic memristive synapses and electronic neurons.

  3. Controllable Passively Q-Switched Laser

    Institute of Scientific and Technical Information of China (English)

    YANG Cheng-Wei; HUO Yu-Jing; HE Shu-Fang; YIN Xiao-Dong; ZHANG Bao-Shun

    2005-01-01

    @@ We present a novel kind of pulsed laser named controllable passively Q-switched laser (CPQL). A CPQL of Nd:YVO4 with Cr:YAG as saturable absorber was demonstrated and studied as an example of the kind of pulsed lasers. In CPQL, as the actively controlling signal, a diode laser beam was focused onto the saturable absorber in the resonant cavity of the passively Q-switched laser (PQL) and was absorbed by the absorber to realize the active control of the CPQL. The characters of the CPQL output laser pulses, such as generation time, repetition rate, pulse width, peak power and energy per pulse, can be controlled by the operator. The CPQLs possess the advantages of both passively Q-switched laser and actively Q-switched 1aser. Because of their compactness, low cost and controllability, the CPQLs will find wide applications in many fields.

  4. Intrinsic noise in systems with switching environments

    Science.gov (United States)

    Hufton, Peter G.; Lin, Yen Ting; Galla, Tobias; McKane, Alan J.

    2016-05-01

    We study individual-based dynamics in finite populations, subject to randomly switching environmental conditions. These are inspired by models in which genes transition between on and off states, regulating underlying protein dynamics. Similarly, switches between environmental states are relevant in bacterial populations and in models of epidemic spread. Existing piecewise-deterministic Markov process approaches focus on the deterministic limit of the population dynamics while retaining the randomness of the switching. Here we go beyond this approximation and explicitly include effects of intrinsic stochasticity at the level of the linear-noise approximation. Specifically, we derive the stationary distributions of a number of model systems, in good agreement with simulations. This improves existing approaches which are limited to the regimes of fast and slow switching.

  5. Titanium Oxide Intelligent "Optical Switch" Surface

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Bio-mimic\tsuper-hydrophobic\tand super-hydrophilic switches were highly concerned because of their extensive application perspectives in gene transfers,non-loss liquid transportation,micro fluid,gene chips,and slow released drug.

  6. Operation principle of microsecond plasma opening switches

    International Nuclear Information System (INIS)

    Closing and breaking of current in microsecond megaampere plasma opening switches are considered. Conductivity current scaling in the switch due to plasma acceleration by a magnetic piston is discussed and compared with experimental data. Two ways of determining the width of a current channel are taken up. This channel results from the diffusion of the magnetic field in the plane of the piston followed by the convective ejection of the field frozen in the accelerated plasma flow behind the shock wave into the bridge. Based on experimental data, a scaling law for the voltage on the switch according to the switch parameters is derived. The problem of reverse closing, which limits the efficiency of storage energy extraction into the load, is considered

  7. Threshold switching induced by joule heating

    International Nuclear Information System (INIS)

    The work contained in this thesis is an experimental and theoretical one on thin film threshold switching devices. The used active, semiconductor layers were amorphous boron and polycrystalline and amorphous vanadium dioxide. The static current-voltage characteristics were particularly investigated, the key parameter being the ambient temperature. The quantitative study of the resistive region before the threshold and also of the parameters of the threshold permit a better knowledge of the origins of the phenomena. The comparison of these results and of these published on amorphous chalcogenides permit to give some general conclusions about switching phenomena. Concerning the conducting state obtained after the threshold was reached, it was interpreted in terms of filamentary conduction. Direct observations allowed me to plot electrical parameters versus filament width and to drive conclusions about the filamentary temperature profile in the semi-conductor. I have made a list of applications of switching devices: solid state switch, temperature detector, integrated bistable and oscillating circuits. (author)

  8. Delayed switching applied to memristor neural networks

    International Nuclear Information System (INIS)

    Magnetic flux and electric charge are linked in a memristor. We reported recently that a memristor has a peculiar effect in which the switching takes place with a time delay because a memristor possesses a certain inertia. This effect was named the ''delayed switching effect.'' In this work, we elaborate on the importance of delayed switching in a brain-like computer using memristor neural networks. The effect is used to control the switching of a memristor synapse between two neurons that fire together (the Hebbian rule). A theoretical formula is found, and the design is verified by a simulation. We have also built an experimental setup consisting of electronic memristive synapses and electronic neurons.

  9. Analysis of Switched-Rigid Floating Oscillator

    Directory of Open Access Journals (Sweden)

    Prabhakar R. Marur

    2009-01-01

    Full Text Available In explicit finite element simulations, a technique called deformable-to-rigid (D2R switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.

  10. Impedance spectroscopy analysis of the switching mechanism of reduced graphene oxide resistive switching memory

    Science.gov (United States)

    Ho, Nhu Thuy; Senthilkumar, V.; Kim, Yong Soo

    2014-04-01

    In this study, we investigated the resistive switching behavior of pristine graphene oxide and thermally reduced GO. Impedance spectroscopy and current-voltage analysis were used to verify the possible physical mechanism of the switching operation. Our observations demonstrated that, the switching operation originates from the oxidation/reduction at the top interface of Al electrode and oxygen migration inside the active layer. Reversible redox reaction Al+1 + xO-2 ↔ AlOx is ground for the conduction electrons.

  11. Error rate degradation due to switch crosstalk in large modular switched optical networks

    DEFF Research Database (Denmark)

    Saxtoft, Christian; Chidgey, P.

    1993-01-01

    A theoretical model of an optical network incorporating wavelength selective elements, amplifiers, couplers and switches is presented. The model is used to evaluate a large modular switch optical network that provides the capability of adapting easily to changes in network traffic requirements. The...... network dimensions are shown to be limited by the optical crosstalk in the switch matrices and by the polarization dependent loss in the optical components...

  12. Power consumption evaluation of circuit-switched versus packet-switched optical backbone networks

    OpenAIRE

    Van Heddeghem W.; Lannoo B.; Colle D.; Pickavet M.; Musumeci F.; Pattavina A.; Idzikowski F.

    2013-01-01

    While telecommunication networks have historically been dominated by a circuit-switched paradigm, the last decades have seen a clear trend towards packet-switched networks. In this paper we evaluate how both paradigms perform in optical backbone networks from a power consumption point of view, and whether the general agreement of circuit switching being more power-efficient holds. We consider artificially generated topologies of various sizes, mesh degrees and not yet previously explored in t...

  13. Torque control of switched reluctance motors

    OpenAIRE

    Moron Fernandez, Carlos; Garcia Garcia, Alfonso; Tremps Guerra, Enrique; Somolinos Sanchez, Jose Andres

    2011-01-01

    This paper presents the performance of an instantaneous torque control method. The simulation and experimental results illustrate the capability of Switched Reluctance Motors (SRM) being used in the motor drive industry. Based on experimental data, the advantages of this control method and its disadvantages in practical implementation were studied. The model used in the simulation is the linear magnetic model which has the 12/8 structure, the same structure as the experimental switched re...

  14. The Robustness of Stochastic Switching Networks

    OpenAIRE

    Loh, Po-Ling; Zhou, Hongchao; Bruck, Jehoshua

    2009-01-01

    Many natural systems, including chemical and biological systems, can be modeled using stochastic switching circuits. These circuits consist of stochastic switches, called pswitches, which operate with a fixed probability of being open or closed. We study the effect caused by introducing an error of size ∈ to each pswitch in a stochastic circuit. We analyze two constructions – simple series-parallel and general series-parallel circuits – and prove that simple series-parallel circuits are robus...

  15. Teachers' Code Switching in EFL Classroom

    Institute of Scientific and Technical Information of China (English)

    张素敏

    2007-01-01

    In theory, language teaching today should be entirely monolingual-using target language as the medium of instruction.ciency' (Brice 2000). This paper is devoted to exploring the theoretical justification for the existence of code switching and the pedagogical purposes for the use of it in EFL classroom, with a hope to raise EFT teachers' awareness of the actual use of code switching in classroom and help them develop an appropriate attitude towards its role in EFL teaching.

  16. United assembly algorithm for optical burst switching

    Institute of Scientific and Technical Information of China (English)

    Jinhui Yu(于金辉); Yijun Yang(杨教军); Yuehua Chen(陈月华); Ge Fan(范戈)

    2003-01-01

    Optical burst switching (OBS) is a promising optical switching technology. The burst assembly algorithm controls burst assembly, which significantly impacts performance of OBS network. This paper provides a new assembly algorithm, united assembly algorithm, which has more practicability than conventional algorithms. In addition, some factors impacting selections of parameters of this algorithm are discussed and the performance of this algorithm is studied by computer simulation.

  17. Multiple-product firms and product switching

    OpenAIRE

    Andrew B. Bernard; Redding, Stephen; Peter K. Schott

    2010-01-01

    This paper examines the frequency, pervasiveness, and determinants of product switching by US manufacturing firms. We find that one-half of firms alter their mix of five-digit SIC products every five years, that product switching is correlated with both firm- and firm-product attributes, and that product adding and dropping induce large changes in firm scope. The behavior we observe is consistent with a natural generalization of existing theories of industry dynamics that incorporates endogen...

  18. Portfolio Selection with Jumps under Regime Switching

    Directory of Open Access Journals (Sweden)

    Lin Zhao

    2010-01-01

    Full Text Available We investigate a continuous-time version of the mean-variance portfolio selection model with jumps under regime switching. The portfolio selection is proposed and analyzed for a market consisting of one bank account and multiple stocks. The random regime switching is assumed to be independent of the underlying Brownian motion and jump processes. A Markov chain modulated diffusion formulation is employed to model the problem.

  19. Oscillatory Dynamical Switching System of Bulk Ferroelectrics

    OpenAIRE

    M. N.A. Halif; S. Daud; Junaidah Osman

    2005-01-01

    This study gives a detailed account of calculation of the bulk ferroelectric (FE) oscillatory dynamical system switching to first and second-order phase transition, respectively. All the formalism is delineated in the framework of Landau free-energy expansion and Landau-Khalatnikov (LK) equation of motion where the effect of external energy may affray FE atoms similar to the spring damped oscillatory system. Here we scrutinized the switching properties from free-energy expansion and hysteresi...

  20. Software for monitoring switching sistem performance

    OpenAIRE

    Kalan, Blaž

    2011-01-01

    Statistical control and overview of a particular switching system's operating status play an important role in the modern development of switching systems. The Performance and Quality Monitoring System (PQMS) is one of the numerous Iskratel's products, and is used to monitor the network performance and the quality of service. This product enables the collection and mediation (transformation) of files with call detail records. By using the stored data, this product makes it possible to easily ...

  1. ADAPTIVE GENERALIZED PREDICTIVE CONTROL OF SWITCHED SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    WANG Yi-jing; WANG Long

    2005-01-01

    The problem of adaptive generalized predictive control which consists of output prediction errors for a class of switched systems is studied. The switching law is determined by the output predictive errors of a finite number of subsystems. For the single subsystem and multiple subsystems cases, it is proved that the given direct algorithm of generalized predictive control guarantees the global convergence of the system. This algorithm overcomes the inherent drawbacks of the slow convergence and large transient errors for the conventional adaptive control.

  2. Understanding Markov-switching rational expectations models

    OpenAIRE

    Roger E.A. Farmer; Daniel F. Waggoner; Zha, Tao

    2009-01-01

    We develop a set of necessary and sufficient conditions for equilibria to be determinate in a class of forward-looking Markov-switching rational expectations models, and we develop an algorithm to check these conditions in practice. We use three examples, based on the new Keynesian model of monetary policy, to illustrate our technique. Our work connects applied econometric models of Markov switching with forward-looking rational expectations models and allows an applied researcher to construc...

  3. Measuring and modeling switched Ethernet networks

    OpenAIRE

    2003-01-01

    Switched Ethernet is a dominating technology in local area networks, and a strong contender in system area networks. This thesis describes measurements on switched Ethernets, in the context of high speed system area networks with real time requirements. One such system is the ATLAS level 2 trigger, which formed the basis of the measurements. Further on the thesis describes the design, implementation and results from a simulation model of the measured devic...

  4. New pulse modulator with low switching frequency

    OpenAIRE

    Golub V. S.

    2014-01-01

    The author presents an integrating pulse modulator (analog signal converter) with the pulse frequency and duration modulation similar to sigma-delta modulation (with low switching frequency), without quantization. The modulator is characterized by the absence of the quantization noise inherent in sigma-delta modulator, and a low switching frequency, unlike the pulse-frequency modulator. The modulator is recommended, in particular, to convert signals at the input of the class D power amplifier.

  5. Energy Switching Threshold for Climatic Benefits

    Science.gov (United States)

    Zhang, X.; Cao, L.; Caldeira, K.

    2013-12-01

    Climate change is one of the great challenges facing humanity currently and in the future. Its most severe impacts may still be avoided if efforts are made to transform current energy systems (1). A transition from the global system of high Greenhouse Gas (GHG) emission electricity generation to low GHG emission energy technologies is required to mitigate climate change (2). Natural gas is increasingly seen as a choice for transitions to renewable sources. However, recent researches in energy and climate puzzled about the climate implications of relying more energy on natural gas. On one hand, a shift to natural gas is promoted as climate mitigation because it has lower carbon per unit energy than coal (3). On the other hand, the effect of switching to natural gas on nuclear-power and other renewable energies development may offset benefits from fuel-switching (4). Cheap natural gas is causing both coal plants and nuclear plants to close in the US. The objective of this study is to measure and evaluate the threshold of energy switching for climatic benefits. We hypothesized that the threshold ratio of energy switching for climatic benefits is related to GHGs emission factors of energy technologies, but the relation is not linear. A model was developed to study the fuel switching threshold for greenhouse gas emission reduction, and transition from coal and nuclear electricity generation to natural gas electricity generation was analyzed as a case study. The results showed that: (i) the threshold ratio of multi-energy switching for climatic benefits changes with GHGs emission factors of energy technologies. (ii)The mathematical relation between the threshold ratio of energy switching and GHGs emission factors of energies is a curved surface function. (iii) The analysis of energy switching threshold for climatic benefits can be used for energy and climate policy decision support.

  6. Anticompetitive Marketing in a Pharmaceutical Switching Context

    OpenAIRE

    Domeij, Bengt

    2012-01-01

    The article deals with the intersection between competition law rules on abuse of a dominant position and switching strategies employed by pharmaceutical originator companies. Switching is also known as ever-greening, product hopping or product life cycle strategies. It is one of the most topical issues in the patent-antitrust intersection today and consists in launching a slightly modified, second generation pharmaceutical, 1-2 years before the patent exclusivity expires for a first generati...

  7. Theory of circuit block switch-off

    OpenAIRE

    S. Henzler; J. Berthold; G. Georgakos; Schmitt-Landsiedel, D.

    2005-01-01

    Switching-off unused circuit blocks is a promising approach to supress static leakage currents in ultra deep sub-micron CMOS digital systems. Basic performance parameters of Circuit Block Switch-Off (CBSO) schemes are defined and their dependence on basic circuit parameters is estimated. Therefore the design trade-off between strong leakage suppression in idle mode and adequate dynamic performance in active mode can be supported by simple analytic investigations. Additionally, a guideline for...

  8. White-opaque switching in Candida albicans

    OpenAIRE

    Lohse, Matthew B.; Johnson, Alexander D.

    2009-01-01

    The human commensal yeast Candida albicans undergoes an epigenetic switch between two distinct types of cells, referred to as white and opaque. These two cell types differ in many respects, including their cell and colony morphologies, their metabolic states, their mating behaviors, their preferred niches in the host, and their interactions with the host immune system. Each of the two cell types is heritable for many generations and switching between them appears stochastic; however, environm...

  9. A microcomputer for a packet switched network

    International Nuclear Information System (INIS)

    The Bubble Chamber Research Group of the Rutherford and Appleton Laboratory has a large film analysis facility. This comprises 16 digitising tables used for the measurement of bubble chamber film. Each of these tables has an associated microcomputer. These microcomputers are linked by a star structured packet switched local area network (LAN) to a VAX 11/780. The LAN, and in particular a microcomputer of novel architecture designed to act as the central switch of the network, is described. (author)

  10. Ultrafast nanomagnetic toggle switching of vortex cores

    OpenAIRE

    Hertel, R.; Gliga, S.; Fähnle, M.; Schneider, C. M.

    2007-01-01

    We present an ultrafast route for a controlled, toggle switching of magnetic vortex cores with ultrashort unipolar magnetic field pulses. The switching process is found to be largely insensitive to extrinsic parameters, like sample size and shape, and it is faster than any field-driven magnetization reversal process previously known from micromagnetic theory. Micromagnetic simulations demonstrate that the vortex core reversal is mediated by a rapid sequence of vortex-antivortex pair creation ...

  11. Multiple output zero-current switching switched-capacitor bidirectional dc-dc converter

    Science.gov (United States)

    Lee, Yuang-Shung; Ko, Yi-Pin; Chi, Chien-An

    2010-08-01

    The proposed circuit is a multiple output quasi-resonant (QR) zero-current switching (ZCS) switched-capacitor (SC) converter with a bidirectional power flow control conversion scheme. The principles of the proposed multiple output QR ZCS SC bidirectional dc-dc converter are described using a detailed circuit model for analysis. Simulation and experimental results are carried out to verify the validity and the soft switching performance of the proposed converter. The maximum efficiency achievable is about 94 and 92% for the forward and reverse power flow control schemes, respectively. The output voltage can be regulated by changing the switching frequency for the designed compensated closed-loop controller.

  12. On The Snubber Influence To The Switching And Conduction Losses In A Converter Using Switched Capacitor

    Directory of Open Access Journals (Sweden)

    Viorel DUGAN

    2002-12-01

    Full Text Available The paper deals to design and to compute the snubber parameters influence on the switching and conduction losses of the transistors (IGBT used as bidirectional switches in a converter with switched capacitor. The converter was modelled with difference equations, and the transistors during turn-on and turn-off processes were simulated by dynamically varying resistance models. The energy loss per switching, commutation time, the variation of the transistor voltage etc. and the influence of snubber parameters in each of these cases are shown in the context of a converter used as a 50Hz reactive power controller unit

  13. Atomistic simulations of electrochemical metallization cells: mechanisms of ultra-fast resistance switching in nanoscale devices

    Science.gov (United States)

    Onofrio, Nicolas; Guzman, David; Strachan, Alejandro

    2016-07-01

    We describe a new method that enables reactive molecular dynamics (MD) simulations of electrochemical processes and apply it to study electrochemical metallization cells (ECMs). The model, called EChemDID, extends the charge equilibration method to capture the effect of external electrochemical potential on partial atomic charges and describes its equilibration over connected metallic structures, on-the-fly, during the MD simulation. We use EChemDID to simulate resistance switching in nanoscale ECMs; these devices consist of an electroactive metal separated from an inactive electrode by an insulator and can be reversibly switched to a low-resistance state by the electrochemical formation of a conducting filament between electrodes. Our structures use Cu as the active electrode and SiO2 as the dielectric and have dimensions at the foreseen limit of scalability of the technology, with a dielectric thickness of approximately 1 nm. We explore the effect of device geometry on switching timescales and find that nanowires with an electroactive shell, where ions migrate towards a smaller inactive electrode core, result in faster switching than planar devices. We observe significant device-to-device variability in switching timescales and intermittent switching for these nanoscale devices. To characterize the evolution in the electronic structure of the dielectric as dissolved metallic ions switch the device, we perform density functional theory calculations on structures obtained from an EChemDID MD simulation. These results confirm the appearance of states around the Fermi energy as the metallic filament bridges the electrodes and show that the metallic ions and not defects in the dielectric contribute to the majority of those states.

  14. Atomistic simulations of electrochemical metallization cells: mechanisms of ultra-fast resistance switching in nanoscale devices.

    Science.gov (United States)

    Onofrio, Nicolas; Guzman, David; Strachan, Alejandro

    2016-08-01

    We describe a new method that enables reactive molecular dynamics (MD) simulations of electrochemical processes and apply it to study electrochemical metallization cells (ECMs). The model, called EChemDID, extends the charge equilibration method to capture the effect of external electrochemical potential on partial atomic charges and describes its equilibration over connected metallic structures, on-the-fly, during the MD simulation. We use EChemDID to simulate resistance switching in nanoscale ECMs; these devices consist of an electroactive metal separated from an inactive electrode by an insulator and can be reversibly switched to a low-resistance state by the electrochemical formation of a conducting filament between electrodes. Our structures use Cu as the active electrode and SiO2 as the dielectric and have dimensions at the foreseen limit of scalability of the technology, with a dielectric thickness of approximately 1 nm. We explore the effect of device geometry on switching timescales and find that nanowires with an electroactive shell, where ions migrate towards a smaller inactive electrode core, result in faster switching than planar devices. We observe significant device-to-device variability in switching timescales and intermittent switching for these nanoscale devices. To characterize the evolution in the electronic structure of the dielectric as dissolved metallic ions switch the device, we perform density functional theory calculations on structures obtained from an EChemDID MD simulation. These results confirm the appearance of states around the Fermi energy as the metallic filament bridges the electrodes and show that the metallic ions and not defects in the dielectric contribute to the majority of those states. PMID:27218609

  15. Reversible switching in self-assembled monolayers of azobenzene thiolates on Au (111) probed by threshold photoemission

    International Nuclear Information System (INIS)

    Highlights: ► Photoelectron spectroscopy of liquid phase prepared SAMs of azobenzene derivative. ► Photo-induced reversible switching in densely packed SAM is monitored. ► Maximum density of switched molecules in SAM is derived from photoemission data. ► Switching reaction only enabled at defects sites within the molecular layer. - Abstract: The reversible photo- and thermally activated isomerization of the molecular switch 3-(4-(4-Hexyl-phenylazo)-phenoxy)-propane-1-thiol (ABT, short for AzoBenzeneThiol) deposited by self-assembly from solution on Au (111) was studied using laser-based photoelectron spectroscopy. Differences in the molecular dipole moment characteristic for the trans and the cis isomer of ABT were monitored via changes in the sample work function, accessible by detection of the threshold energy for photoemission. A quantitative analysis of our data shows that the fraction of molecules within the densely packed monolayer that undergoes a switching process is of the order of 1%. This result indicates the relevance of substrate and film defects required to overcome the steric or electronic hindrance of the isomerization reaction in a densely packed monolayer.

  16. Switching system for the FXR accelerator

    International Nuclear Information System (INIS)

    A switching system has been designed for a 20 MeV flash x-ray linear induction accelerator which is being built at Lawrence Livermore Laboratory. The switching system fans out a single command pulse and amplifies it to obtain the voltage necessary for reliable, low-jitter triggering of the accelerator components. This system consists of two major subsystems: (1) the Blumlein Charging Subsystem which first triggers thirteen Marx generators, and then charges 54 water-filled Blumleins, and (2) the Blumlein Triggering Subsystem which triggers the already-charged Blumleins to produce a 90 nanosecond, 400 kV pulse in each of 54 ferrite-loaded accelerator modules. The first subsystem consists of charged high voltage cabling with two parallel switch gaps either of which will trigger the Marx generators. The major components of the second subsystem are three stages of switch gaps along with the necessary high voltage cabling. Two parallel first stage switch gaps trigger thirteen second stage gaps, which in turn trigger 54 third stage Blumlein switch gaps synchronous with the passage of the electron beam pulse. These spark gaps are operated at a voltage of 150 to 350 kV with a 1/3 hertz repetition rate. Varying the cable lengths creates the actual delay times in the triggering of each component. Redundancy is built into the system to insure the high reliability which is essential for the flash radiography application

  17. 49 CFR 236.817 - Switch, electro-pneumatic.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Switch, electro-pneumatic. 236.817 Section 236.817 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Switch, electro-pneumatic. A switch operated by an electro-pneumatic switch-and-lock movement....

  18. SWITCHED-CAPACITOR BASED STEP-DOWN RESONANT CONVERTERS

    Institute of Scientific and Technical Information of China (English)

    Y.P.B.Yeung; K.W.E.Cheng; K.K.Law

    2001-01-01

    A family of switched-capacitor based resonant converters is present.All converters are in step-downmode.By adding different number of switched-capacitor cells,different output voltage conversion ratio can beobtained.All switching devices in the converters operate under zero-current switching.Both high frequencyoperations and high efficiency are possible.

  19. Comparing Switch Costs: Alternating Runs and Explicit Cuing

    Science.gov (United States)

    Altmann, Erik M.

    2007-01-01

    The task-switching literature routinely conflates different operational definitions of switch cost, its predominant behavioral measure. This article is an attempt to draw attention to differences between the two most common definitions, alternating-runs switch cost (ARS) and explicit-cuing switch cost (ECS). ARS appears to include both the costs…

  20. 47 CFR 32.2211 - Non-digital switching.

    Science.gov (United States)

    2010-10-01

    ... switching. (a) This account shall include: (1) Original cost of stored program control analog circuit-switching and associated equipment. (2) Cost of remote analog electronic circuit switches. (3) Original cost... 47 Telecommunication 2 2010-10-01 2010-10-01 false Non-digital switching. 32.2211 Section...