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Sample records for charge pump clock

  1. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  2. Pump trials for charged liquids

    International Nuclear Information System (INIS)

    The pumps intended for the circulation of charged and radioactive liquids have particular qualities. The choice of such a pump has called for endurance tests with various types of equipment: a Goodyear volumetric screw pumps, and RICHIER, Klein and SCHABAVER centrifugal pumps. The latter, fitted with a special oakum, gave the best results. (authors)

  3. Charge Pump Clock Generation PLL for the Data Output Block of the Upgraded ATLAS Pixel Front-End in 130 nm CMOS

    CERN Document Server

    Kruth, A; Arutinov, D; Barbero, M; Gronewald, M; Hemperek, T; Karagounis, M; Krueger, H; Wermes, N; Fougeron, D; Menouni, M; Beccherle, R; Dube, S; Ellege, D; Garcia-Sciveres, M; Gnani, D; Mekkaoui, A; Gromov, V; Kluit, R; Schipper, J

    2009-01-01

    FE-I4 is the 130 nm ATLAS pixel IC currently under development for upgraded Large Hadron Collider (LHC) luminosities. FE-I4 is based on a low-power analog pixel array and digital architecture concepts tuned to higher hit rates [1]. An integrated Phase Locked Loop (PLL) has been developed that locally generates a clock signal for the 160 Mbit/s output data stream from the 40 MHz bunch crossing reference clock. This block is designed for low power, low area consumption and recovers quickly from loss of lock related to single-event transients in the high radiation environment of the ATLAS pixel detector. After a general introduction to the new FE-I4 pixel front-end chip, this work focuses on the FE-I4 output blocks and on a first PLL prototype test chip submitted in early 2009. The PLL is nominally operated from a 1.2V supply and consumes 3.84mW of DC power. Under nominal operating conditions, the control voltage settles to within 2% of its nominal value in less than 700 ns. The nominal operating frequency for t...

  4. Pressure charged airlift pump

    Science.gov (United States)

    Campbell, Gene K.

    1983-01-01

    A pumping system is described for pumping fluids, such as water with entrained mud and small rocks, out of underground cavities such as drilled wells, which can effectively remove fluids down to a level very close to the bottom of the cavity and which can operate solely by compressed air pumped down through the cavity. The system utilizes a subassembly having a pair of parallel conduit sections (44, 46) adapted to be connected onto the bottom of a drill string utilized for drilling the cavity, the drill string also having a pair of coaxially extending conduits. The subassembly includes an upper portion which has means for connection onto the drill string and terminates the first conduit of the drill string in a plenum (55). A compressed air-driven pump (62) is suspended from the upper portion. The pump sucks fluids from the bottom of the cavity and discharges them into the second conduit. Compressed air pumped down through the first conduit (46) to the plenum powers the compressed air-driven pump and aerates the fluid in the second conduit to lift it to the earth's surface.

  5. Piston-assisted charge pumping

    CERN Document Server

    Kaur, D; Mourokh, L

    2015-01-01

    We examine charge transport through a system of three sites connected in series in the situation when an oscillating charged piston modulates the energy of the middle site. We show that with an appropriate set of parameters, charge can be transferred against an applied voltage. In this scenario, when the oscillating piston shifts away from the middle site, the energy of the site decreases and it is populated by a charge transferred from the lower energy site. On the other hand, when the piston returns to close proximity, the energy of the middle site increases and it is depopulated by the higher energy site. Thus through this process, the charge is pumped against the potential gradient. Our results can explain the process of proton pumping in one of the mitochondrial enzymes, Complex I. Moreover, this mechanism can be used for electron pumping in semiconductor nanostructures.

  6. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P.; Christenson, Todd R.

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  7. Charge Pump for LCD Driver Used in Cell Phone

    Institute of Scientific and Technical Information of China (English)

    郁海蓉; 陈志良

    2002-01-01

    A charge pump design is presented to operate at 10 kHz with 100 μA in a liquid crystal display (LCD) driver for cell phone. Optimal channel widths are designed by estimating the power consumption of the Fibonacci-like charge pump. An optimal frequency is a compromise between the rise time and the dynamic power dissipation. The optimization of the two-phase nonoverlapping clock generator circuit improves the efficiency. Simulation results based on 1.2 μm complementary metal-oxide-semiconductor (CMOS) technology parameters verify the efficiency of the design.

  8. Charge domain filter operating up to 20 MHz clock frequency

    OpenAIRE

    Gal, R.A.J.; Wallinga, H.

    1983-01-01

    An analog sampled data low pass third order Butterworth filter has been realised in a buried channel CCD technology. This Charge Domain Filter, composed of transversal and recursive CCD filter sections, has been tested at clock frequencies up to 20 MHz.

  9. 50V All-PMOS Charge Pumps Using Low-Voltage Capacitors

    KAUST Repository

    Emira, Ahmed

    2012-10-06

    In this work, two high-voltage charge pumps are introduced. In order to minimize the area of the pumping capacitors, which dominates the overall area of the charge pump, high density capacitors have been utilized. Nonetheless, these high density capacitors suffer from low breakdown voltage which is not compatible with the targeted high voltage application. To circumvent the breakdown limitation, a special clocking scheme is used to limit the maximum voltage across any pumping capacitor. The two charge pump circuits were fabricated in a 0:6m CMOS technology with poly0-poly1 capacitors. The output voltage of the two charge pumps reached 42:8V and 51V while the voltage across any capacitor did not exceed the value of the input voltage. Compared to other designs reported in the literature, the proposed charge pump provides the highest output voltage which makes it more suitable for tuning MEMS devices.

  10. A new clocking method for a charge coupled device

    International Nuclear Information System (INIS)

    We propose and demonstrate a new clocking method for a charge-coupled device (CCD). When a CCD is used for a photon counting detector of X-rays, its weak point is a limitation of its counting rate, because high counting rate makes non-negligible pile-up of photons. In astronomical usage, this pile-up is especially severe for an observation of a bright point-like object. One typical idea to reduce the pile-up is a parallel sum (P-sum) mode. This mode completely loses one-dimensional information. Our new clocking method, panning mode, provides complementary properties between the normal mode and the P-sum mode. We performed a simple simulation in order to investigate a pile-up probability and compared the simulated result and actual obtained event rates. Using this simulation and the experimental results, we compared the pile-up tolerance of various clocking modes including our new method and also compared their other characteristics

  11. Transient analysis of charging system with centrifugal charging pumps

    International Nuclear Information System (INIS)

    The CARD (CVCS Analysis for Design) code has been developed for the transient analysis of the letdown and charging system of Korea Standard Nuclear Power Plant. The computer code has been already verified and validated by comparing with actual test results. Analyzed in this paper are the flow and pressure transients in the charging line. The sensitivity studies are performed to select the acceptable control parameters of charging line backpressure controller and seal injection flow controller. In addition, the seal injection system transient is evaluated for the pressurizer auxiliary spray operation. It is shown that the charging line backpressure controller control parameters yield a significant effect on the charging system stability. The results obtained from this study will be used to verify the system design and to select the optimum control parameters for the charging system with centrifugal charging pumps

  12. Testing spatial α-variation with optical atomic clocks based on highly charged ions

    International Nuclear Information System (INIS)

    We review recent works illustrating the potential use of highly charged ions as the basis of optical atomic clocks of exceptional accuracy and very high sensitivity to variation of the fine structure constant, α. The tendency towards large transition energies in highly charged ions can be overcome using level crossings, which allow transitions between different orbitals to be within the range of usual lasers. We present simple scaling laws that demonstrate reduced systematics that could be realised in highly charged ion clocks. Such clocks could allow us to corroborate astronomical studies that suggest a spatial gradient in values of α across the Universe. (authors)

  13. Testing spatial α-variation with optical atomic clocks based on highly charged ions

    Directory of Open Access Journals (Sweden)

    Berengut J. C.

    2013-08-01

    Full Text Available We review recent works illustrating the potential use of highly charged ions as the basis of optical atomic clocks of exceptional accuracy and very high sensitivity to variation of the fine structure constant, α. The tendency towards large transition energies in highly charged ions can be overcome using level crossings, which allow transitions between different orbitals to be within the range of usual lasers. We present simple scaling laws that demonstrate reduced systematics that could be realised in highly charged ion clocks. Such clocks could allow us to corroborate astronomical studies that suggest a spatial gradient in values of α across the Universe.

  14. A charge-driven molecular water pump.

    Science.gov (United States)

    Gong, Xiaojing; Li, Jingyuan; Lu, Hangjun; Wan, Rongzheng; Li, Jichen; Hu, Jun; Fang, Haiping

    2007-11-01

    Understanding and controlling the transport of water across nanochannels is of great importance for designing novel molecular devices, machines and sensors and has wide applications, including the desalination of seawater. Nanopumps driven by electric or magnetic fields can transport ions and magnetic quanta, but water is charge-neutral and has no magnetic moment. On the basis of molecular dynamics simulations, we propose a design for a molecular water pump. The design uses a combination of charges positioned adjacent to a nanopore and is inspired by the structure of channels in the cellular membrane that conduct water in and out of the cell (aquaporins). The remarkable pumping ability is attributed to the charge dipole-induced ordering of water confined in the nanochannels, where water can be easily driven by external fields in a concerted fashion. These findings may provide possibilities for developing water transport devices that function without osmotic pressure or a hydrostatic pressure gradient. PMID:18654410

  15. Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

    Institute of Scientific and Technical Information of China (English)

    Aiying Yang; Yunan Sun

    2008-01-01

    @@ 40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.

  16. Apparatus for fermion atomic clock, atom interferometry and quantum pumping experiments

    Science.gov (United States)

    Ivory, M. K.; Ziltz, A.; Field, J.; Aubin, S.

    2010-03-01

    We present the current state of an apparatus designed to create and manipulate ultracold bosonic and fermionic Rb and K isotopes for a fermion atomic clock, atom interferometry, microwave trapping, and quantum pumping experiments. Quantum pumping is a phenomenon which can precisely control bias-less flow of single electrons in a circuit. Using ultracold atoms on atom chips, we can test theoretical predictions which have not yet been verified due to experimental difficulties in solid state systems. The apparatus design consists of a magneto-optical trap, magnetic transport system, atom chip, and optical dipole trap. We have demonstrated basic laser cooling and trapping and are working towards transport of the collected atoms to the atom chip for cooling to quantum degeneracy. Once quantum degeneracy is achieved at the chip, micro-magnetic reservoirs of ultracold atoms connected by a 1D ``wire'' create a circuit for various quantum pumping schemes. These schemes are also more broadly applicable to atomtronics experiments.

  17. Analysis and Design of Charge Pumps for Telecommunication Applications

    OpenAIRE

    Kalenteridis, Vassilis; Papathanasiou, Konstantinos; Siskos, Stylianos

    2010-01-01

    This chapter addresses modern telecommunication integrated circuits from the synthesizer focal point; in particular it concentrates at the analysis and the design of integrated charge pump circuit blocks. It presents an overview of charge pump topologies in addition to a coherent analysis of the associated benefits and shortcomings of all circuit alternatives. Moreover a novel favorable charge pump combining current steering techniques with well utilized unity gain buffers in a novel, noisele...

  18. Testing of high-vacuum pumps for charged particle accelerators

    International Nuclear Information System (INIS)

    To study a possibility of employing different types of pumps in charged-particle accelerators the following pumps have been tested: electric-arc, turbomolecular and cryogenic. The research has been carried out on a test bench which made it possible to determine the pumping-out rate for different gases (constant-volume methods), measure their limiting pressure and study the spectra of different gases by using mass spectrometers. It was possible also to warm up the pumps and pumped-out volumes. From these tests it was concluded that: (1) the electric-arc pump does not meet the accelerator pumping-out requirements; (2) the turbomolecular pump with a nitrogen-sorption trap can be recommended for pumping-out accelerators but requires modification of the supply unit; (3) the cryogenic pump can be recommended for pumpimg-out of accelerators but requires modification of the automatic system for replenishment of the cryogenic fluid

  19. Testing spatial α-variation with optical atomic clocks based on highly charged ions

    OpenAIRE

    Berengut J. C.; Flambaum V. V.; Ong A.

    2013-01-01

    We review recent works illustrating the potential use of highly charged ions as the basis of optical atomic clocks of exceptional accuracy and very high sensitivity to variation of the fine structure constant, α. The tendency towards large transition energies in highly charged ions can be overcome using level crossings, which allow transitions between different orbitals to be within the range of usual lasers. We present simple scaling laws that demonstrate reduced systematics that could be re...

  20. Single-parameter adiabatic charge pumping in carbon nanotube resonators

    OpenAIRE

    Perroni, C. A.; Nocera, A.; Cataudella, V.

    2013-01-01

    Single-parameter adiabatic charge pumping, induced by a nearby radio-frequency antenna, is achieved in suspended carbon nanotubes close to the mechanical resonance. The charge pumping is due to an important dynamic adjustment of the oscillating motion to the antenna signal and it is different from the mechanism active in the two-parameter pumping. Finally, the second harmonic oscillator response shows an interesting relationship with the first harmonic that should be experimentally observed.

  1. A Calibrated Charge Pump for Mismatch Reduction in PLL

    Directory of Open Access Journals (Sweden)

    Jianhui Wu

    2012-12-01

    Full Text Available An improved charge pump (CP for phase locked loop (PLL applications is presented. The proposed charge pump circuitry employs a variable current source in its sink path, which realizes feedback network for calibration. This scheme of charge pump minimizes mismatch between the sourcing current and the sinking current efficiently. The circuit is simulated in 0.18um CMOS technology and the simulation results show that good current matching characteristics can be achieved. The mismatch between the sourcing current and the sinking current can be reduced to less than 0.01% and the range of charge pump output voltage varies from 0.3V to 1.5V.

  2. High-precision atomic clocks with highly charged ions: nuclear spin-zero $f^{12}$-shell ions

    OpenAIRE

    Dzuba, V. A.; Derevianko, A; Flambaum, V. V.

    2012-01-01

    Optical atomic clocks using highly-charged ions hold an intriguing promise of metrology at the 19th significant figure. Here we study transitions within the $4f^{12}$ ground-state electronic configuration of highly charged ions. We consider isotopes lacking hyperfine structure and show that the detrimental effects of coupling of electronic quadrupole moments to gradients of trapping electric field can be effectively reduced by using specially chosen virtual clock transitions. The estimated sy...

  3. A charge pump for driving CMOS active pixel reset

    Institute of Scientific and Technical Information of China (English)

    XU Jiang-tao; LI Bin-qiao; YAO Su-ying; SUN Zhong-yan

    2009-01-01

    To overcome the limitation of low image signal swing range and long reset time in four transistor CMOS active pixel image sensor, a charge pump circuit is presented to improve the pixel reset performance. The charge pump circuit consists of two stage switch capacitor serial voltage doubler. Cross-coupled MOSFET switch structure with well close and open perfor-mance is used in the second stage of the charge pump. The pixel reset transistor with gate voltage driven by output of the pump works in linear region, which can accelerate reset process and complete reset is achieved. The simulation results show that output of the charge pump is enhanced from 1.2 to 4.2 V with voltage tipple lower than 6 inV. The pixel reset time is reduced to 1.14 ns in dark. Image smear due to non-completely reset is eliminated and the image signal swing range is enlarged. The charge pump is successfully embedded in a CMOS image sensor chip with 0.3 ~ 106 pixeis.

  4. Highly charged ions for atomic clocks and search for variation of the fine structure constant

    CERN Document Server

    Dzuba, V A

    2015-01-01

    We review a number of highly charged ions which have optical transitions suitable for building extremely accurate atomic clocks. This includes ions from Hf$^{12+}$ to U$^{34+}$, which have the $4f^{12}$ configuration of valence electrons, the Ir$^{17+}$ ion, which has a hole in almost filled $4f$ subshell, the Ho$^{14+}$, Cf$^{15+}$, Es$^{17+}$ and Es$^{16+}$ ions. Clock transitions in most of these ions are sensitive to variation of the fine structure constant, $\\alpha$ ($\\alpha = e^2/\\hbar c$). E.g., californium and einsteinium ions have largest known sensitivity to $\\alpha$-variation while holmium ion looks as the most suitable ion for experimental study. We study the spectra of the ions and their features relevant to the use as frequency standards.

  5. Topological charge pump by surface acoustic waves

    Science.gov (United States)

    Yi, Zheng; Shi-Ping, Feng; Shi-Jie, Yang

    2016-06-01

    Quantized electron pumping by the surface acoustic wave across barriers created by a sequence of split metal gates is interpreted from the viewpoint of topology. The surface acoustic wave serves as a one-dimensional periodical potential whose energy spectrum possesses the Bloch band structure. The time-dependent phase plays the role of an adiabatic parameter of the Hamiltonian which induces a geometrical phase. The pumping currents are related to the Chern numbers of the filled bands below the Fermi energy. Based on this understanding, we predict a novel effect of quantized but non-monotonous current plateaus simultaneously pumped by two homodromous surface acoustic waves. Project supported by the National Natural Science Foundation of China (Grant No. 11374036) and the National Basic Research Program of China (Grant No. 2012CB821403).

  6. Search for Effects of an Electrostatic Potential on Clocks in the Frame of Reference of a Charged Particle

    Science.gov (United States)

    Ringermacher, Harry I.; Conradi, Mark S.; Cassenti, Brice

    2005-01-01

    Results of experiments to confirm a theory that links classical electromagnetism with the geometry of spacetime are described. The theory, based on the introduction of a Torsion tensor into Einstein s equations and following the approach of Schroedinger, predicts effects on clocks attached to charged particles, subject to intense electric fields, analogous to the effects on clocks in a gravitational field. We show that in order to interpret this theory, one must re-interpret all clock changes, both gravitational and electromagnetic, as arising from changes in potential energy and not merely potential. The clock is provided naturally by proton spins in hydrogen atoms subject to Nuclear Magnetic Resonance trials. No frequency change of clocks was observed to a resolution of 6310(exp -9). A new "Clock Principle" was postulated to explain the null result. There are two possible implications of the experiments: (a) The Clock Principle is invalid and, in fact, no metric theory incorporating electromagnetism is possible; (b) The Clock Principle is valid and it follows that a negative rest mass cannot exist.

  7. Study of laser-pumped double-resonance clock signals using a microfabricated cell

    International Nuclear Information System (INIS)

    We present our microwave spectroscopic studies on laser-microwave double-resonance (DR) signals obtained from a micro-fabricated Rb vapor cell. This study focuses on the characteristics and systematic shifts of the ground-state 'clock transition' in 87Rb (| Fg = 1,mF = 0) → | Fg = 2, mF = 0)) used in Rb atomic clocks, and represents a first step toward a miniature atomic clock based on the DR scheme. A short-term clock instability below 2 × 1011τ-1/2 is demonstrated, staying below 10-11 up to τ = 104 s.

  8. Refrigerant charge management in a heat pump water heater

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jie; Hampton, Justin W.

    2016-07-05

    Heat pumps that heat or cool a space and that also heat water, refrigerant management systems for such heat pumps, and methods of managing refrigerant charge. Various embodiments remove idle refrigerant from a heat exchanger that is not needed for transferring heat by opening a refrigerant recovery valve and delivering the idle refrigerant from the heat exchanger to an inlet port on the compressor. The heat exchanger can be isolated by closing an electronic expansion valve, actuating a refrigerant management valve, or both. Refrigerant charge can be controlled by controlling how much refrigerant is drawn from the heat exchanger, by letting some refrigerant back into the heat exchanger, or both. Heat pumps can be operated in different modes of operation, and various components can be interconnected with refrigerant conduit. Some embodiments deliver refrigerant gas to the heat exchanger and drive liquid refrigerant out prior to isolating the heat exchanger.

  9. Charge pumping at radio frequencies [MOSFET device interface state density measurement

    OpenAIRE

    Sasse, G.T.; Vries, de, P.M.; Schmitz, J

    2005-01-01

    In this work, for the first time, charge pump results are shown that are obtained at frequencies in the GHz range. A comparison is made with charge pump results at lower frequencies. A very good agreement is seen between the low frequency charge pump data and the RF charge pump data. Measurement results on dielectrics that suffer from a high leakage current show that a charge pump current can be measured at frequencies above 500 MHz. At lower frequencies the charge pump current is completely ...

  10. Reliability characteristics of microfabricated Rb mini-lamps for optical pumping in miniature atomic clocks and magnetometers

    Science.gov (United States)

    Venkatraman, Vinu; Pétremand, Yves; de Rooij, Nico; Shea, Herbert

    2013-03-01

    With the rising need for microfabricated chip-scale atomic clocks to enable high precision timekeeping in portable applications, there has been active interest in developing miniature (pumping in double-resonance clocks. We reported in 2012 a first microfabricated chip-scale Rubidium dielectric barrier discharge lamp. The device's preliminary results indicated its high potential for optical pumping applications and wafer-scale batch fabrication. The chip-scale plasma light sources were observed to be robust with no obvious performance change after thousands of plasma ignitions, and with no electrode erosion from plasma discharges since the electrodes are external. However, as atomic clocks have strict lamp performance requirements including less than 0.1% sub-second optical power fluctuations, power consumption less than 20 mW and a device lifetime of at least several years, it is important to understand the long-term reliability of these Rb planar mini-lamps, and identify the operating conditions where these devices can be most reliable and stable. In this paper, we report on the reliability of such microfabricated lamps including a continuous several month run of the lamp where the optical power, electrical power consumption and temperature stability were continuously monitored. We also report on the effects of temperature, rf-power and the lamp-drive parasitics on the optical power stability and discuss steps that could be taken to further improve the device's performance and reliability.

  11. Pump trials for charged liquids; Essais de pompes pour liquides charges

    Energy Technology Data Exchange (ETDEWEB)

    Moroni, J.C.; Niver, A. [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

    1964-07-01

    The pumps intended for the circulation of charged and radioactive liquids have particular qualities. The choice of such a pump has called for endurance tests with various types of equipment: a Goodyear volumetric screw pumps, and RICHIER, Klein and SCHABAVER centrifugal pumps. The latter, fitted with a special oakum, gave the best results. (authors) [French] Les pompes destinees a vehiculer des liquides charges et radioactifs doivent posseder des qualites particulieres. Le choix d'une telle pompe a necessite des essais d'endurance avec divers types de materiel: pompe a vis volumetrique GOODYEAR, pompes centrifuges RICHIER, KLEIN et SCHABAVER. Cette derniere, equipee d'un presse etoupe special, a donne les meilleurs resultats. (auteurs)

  12. Charge pumping due to triplet vector chirality in ferromagnet/triplet superconductor junctions

    OpenAIRE

    Yokoyama, Takehito

    2011-01-01

    We investigate charge pumping in ferromagnet/triplet superconductor junctions where the magnetization of the ferromagnet is inhomogeneous and dynamical. It is shown that charge current is pumped due to the coupling of the localized spin with triplet vector spin chirality, vector spin chirality formed by the triplet vector of Cooper pairing. Physical mechanism of the charge pumping is also discussed.

  13. Research and design of a novel current mode charge pump

    Institute of Scientific and Technical Information of China (English)

    Li Xianrui; Lai Xinquan; Li Yushan; Ye Qiang

    2009-01-01

    To meet the demands for a number of LEDs, a novel charge pump circuit with current mode control is proposed. Regulation is achieved by operating the current mirrors and the output current of the operational transcon ductance amplifier. In the steady state, the input current from power voltage retains constant, so reducing the noise induced on the input voltage source and improving the output voltage ripple. The charge pump small-signal model is used to describe the device's dynamic behavior and stability. Analytical predictions were verified by Hspice sim ulation and testing. Load driving is up to 800 mA with a power voltage of 3.6 V, and the output voltage ripple is less than 45 mV. The output response time is less than 8 μs, and the load current jumps from 400 to 800 mA.

  14. Research and design of a novel current mode charge pump

    International Nuclear Information System (INIS)

    To meet the demands for a number of LEDs, a novel charge pump circuit with current mode control is proposed. Regulation is achieved by operating the current mirrors and the output current of the operational transconductance amplifier. In the steady state, the input current from power voltage retains constant, so reducing the noise induced on the input voltage source and improving the output voltage ripple. The charge pump small-signal model is used to describe the device's dynamic behavior and stability. Analytical predictions were verified by Hspice simulation and testing. Load driving is up to 800 mA with a power voltage of 3.6 V, and the output voltage ripple is less than 45 mV. The output response time is less than 8 μs, and the load current jumps from 400 to 800 mA.

  15. Recent progress in optically-pumped cesium beam clock at Peking University

    Science.gov (United States)

    Liu, C.; Zhou, S.; Wan, J.; Wang, S.; Wang, Y.

    2016-06-01

    A compact, long-life, and low-drift cesium beam clock is investigated at Peking University, where the atoms are magnetic-state selected and optically detected. Stability close to that of the best commercial cesium clocks has been achieved from 10 to 105 s. As previously shown, the short-term stability is determined by atomic shot noise or laser frequency noise. The stabilizations of microwave power and C-field improve the long-term stability, with the help of a digital servo system based on field-programmable gate array.

  16. A CMOS AC/DC charge pump for a wireless sensor network

    International Nuclear Information System (INIS)

    An AC/DC charge pump implemented with MOS FETs has been presented for wireless sensor network applications. The proposed AC/DC charge pump can generate a stable output with low power dissipation and high pumping efficiency, which has been implemented in 0.13 μm CMOS technology. The proposed charge pump employs MOSFET diodes with low thresholds, and improves the conversion efficiency. The analytical model of the voltage multiplier, the simulation results, and the chip testing results are presented.

  17. Clocking molecular fragmentation of N2 with XUV pump-probe experiments

    International Nuclear Information System (INIS)

    The dynamics of multi-photon induced fragmentation of N2 has been investigated in XUV-pump/XUV-probe experiments at the Free-Electron Laser in Hamburg (FLASH) by recording the ion kinetic energy release(KER) and angular distributions for various dissociation- and Coulomb-explosion channels as a function of the pump-probe delay-time.

  18. Design of a CMOS Adaptive Charge Pump with Dynamic Current Matching

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel structure for a charge pump circuit is proposed, in which the charge-pump (CP) current can adaptively regulated according to phase-locked loops (PLL) frequency synthesis demand. The current follow technology is used to make perfect current matching characteristics, and the two differential inverters are implanted to increase the speed of charge pump and decrease output spur due to theory of low voltage difference signal. Simulation results, with 1st silicon 0.25 μm 2.5 V complementary metal-oxide-semiconductor (CMOS) mixed-signal process, show the good current matching characteristics regardless of the charge pump output voltages.

  19. Design and implementation of a clock recovery circuit for fast Ethernet applications

    Institute of Scientific and Technical Information of China (English)

    朱全庆; 邹雪城; 沈绪榜

    2004-01-01

    A circuit architechure to realize clock recovery for fast Ethernet applications is presented, whick includies system architecture, modified Mueller Muller algorithm for 100BASE-TX, phase detector for 100BASE-TX and multiple output charge pump PLL. The clock recovery circuit is verified by TSMC 0.35um 1P5M CMOS process. The results show that this clock recovery circuit exactly extracts the timing information. It has advantages over others for simple and easy implementation.

  20. Clocking ultrafast wave packet dynamics in H2 by using UV pump - UV probe schemes

    International Nuclear Information System (INIS)

    We theoretically investigate the use of UV pump - UV probe schemes with two identical pulses to excite and ionize the hydrogen molecule. The nuclear wave packet (NWP) generated in excited states of neutral molecules is traced by analyzing the asymmetry of the electron angular distributions resulting from dissociative ionization. The mapped NWP can be later used to selectively launch the ionization process into different channels.

  1. Equation of motion approach to non-adiabatic quantum charge pumping

    OpenAIRE

    Agarwal, Amit; Sen, Diptiman

    2006-01-01

    We use the equations of motion of non-interacting electrons in a one-dimensional system to numerically study different aspects of charge pumping. We study the effects of the pumping frequency, amplitude, band filling and finite bias on the charge pumped per cycle, and the Fourier transforms of the charge and energy currents in the leads. Our method works for all values of parameters, and gives the complete time-dependences of the current and charge at any site of the system. Our results agree...

  2. Charge pumping in a quantum wire driven by a series of local time-periodic potentials

    OpenAIRE

    Wang, ZD; Zhu, SL

    2002-01-01

    We develop a method to calculate electronic transport properties through a mesoscopic scattering region in the presence of a series of time-periodic potentials. Using the method, the quantum charge pumping driven by time-periodic potentials is studied. Jumps in the pumped current are observed at the peak positions of the Wigner delay time. Our main results in both the weak pumping and strong pumping regimes are consistent with experimental results. More interestingly, we also observed the non...

  3. Design of a high performance CMOS charge pump for phase-locked loop synthesizers

    International Nuclear Information System (INIS)

    A new high performance charge pump circuit is designed and realized in 0.18 μm CMOS process. A wide input ranged rail-to-rail operational amplifier and self-biasing cascode current mirror are used to enable the charge pump current to be well matched in a wide output voltage range. Furthermore, a method of adding a precharging current source is proposed to increase the initial charge current, which will speed up the settling time of CPPLLs. Test results show that the current mismatching can be less than 0.4% in the output voltage range of 0.4 to 1.7 V, with a charge pump current of 100 μA and a precharging current of 70 μA. The average power consumption of the charge pump in the locked condition is around 0.9 mW under a 1.8 V supply voltage. (semiconductor integrated circuits)

  4. Design of a high performance CMOS charge pump for phase-locked loop synthesizers

    Science.gov (United States)

    Zhiqun, Li; Shuangshuang, Zheng; Ningbing, Hou

    2011-07-01

    A new high performance charge pump circuit is designed and realized in 0.18 μm CMOS process. A wide input ranged rail-to-rail operational amplifier and self-biasing cascode current mirror are used to enable the charge pump current to be well matched in a wide output voltage range. Furthermore, a method of adding a precharging current source is proposed to increase the initial charge current, which will speed up the settling time of CPPLLs. Test results show that the current mismatching can be less than 0.4% in the output voltage range of 0.4 to 1.7 V, with a charge pump current of 100 μA and a precharging current of 70 μA. The average power consumption of the charge pump in the locked condition is around 0.9 mW under a 1.8 V supply voltage.

  5. Orbital dependent ultrafast charge transfer dynamics of ferrocenyl-functionalized SAMs on gold studied by core-hole clock spectroscopy

    International Nuclear Information System (INIS)

    Understanding the charge transport properties in general of different molecular components in a self-assembled monolayer (SAM) is of importance for the rational design of SAM molecular structures for molecular electronics. In this study, we study an important aspect of the charge transport properties, i.e. the charge transfer (CT) dynamics between the active molecular component (in this case, the ferrocenyl moieties of a ferrocenyl-n-alkanethiol SAM) and the electrode using synchrotron-based core-hole clock (CHC) spectroscopy. The characteristic CT times are found to depend strongly on the character of the ferrocenyl-derived molecular orbitals (MOs) which mediate the CT process. Furthermore, by systemically shifting the position of the ferrocenyl moiety in the SAM, it is found that the CT characteristics of the ferrocenyl MOs display distinct dependence on its distance to the electrode. These results demonstrate experimentally that the efficiency and rate of charge transport through the molecular backbone can be modulated by resonant injection of charge carriers into specific MOs. (paper)

  6. Quantum spin and charge pumping through double quantum dots with ferromagnetic leads

    International Nuclear Information System (INIS)

    The pumping of electrons through double quantum dots (DQDs) attached to ferromagnetic leads have been theoretically investigated by using the nonequilibrium Green's function method. It is found that an oscillating electric field applied to the quantum dot may give rise to the pumped charge and spin currents. In the case that both leads are ferromagnet, a pure spin current can be generated in the antiparallel magnetization configuration, where no net charge current exists. The possibility of manipulating the pumped spin current is explored by tuning the dot level and the ac field. By making use of various tunings, the magnitude and direction of the pumped spin current can be well controlled. For the case that only one lead is ferromagnetic, both of the charge and spin currents can be pumped and flow in opposite directions on the average. The control of the magnitude and direction of the pumped charge and spin currents is also discussed by means of the magnetic flux threading through the DQD ring. -- Highlights: → We theoretically investigate the pumping of electrons through double quantum dots attached to ferromagnetic leads. → An oscillating electric field applied to the quantum dot may give rise to the pumped charge and spin currents. → When both leads are ferromagnet, a pure spin current can be generated in the antiparallel magnetization configuration. → By making use of various tunings, the magnitude and direction of the pumped spin current can be well controlled. → When only one lead is ferromagnetic, both of the charge and spin currents can be pumped and flow in opposite directions.

  7. The use of charge-pumping for characterizing irradiated power MOSFETs

    International Nuclear Information System (INIS)

    A charge-pumping technique is proposed for characterizing radiation-induced interface traps in vertical power MOSFETs. An original setup allowing measurements on these 3-contact devices is presented. The first experimental results before and after irradiation are discussed

  8. Experimental Determination of the Berry Phase in a Superconducting Charge Pump

    OpenAIRE

    Möttönen, Mikko; Vartiainen, Juha J.; Pekola, Jukka P.

    2008-01-01

    We present the first measurements of the Berry phase in a superconducting Cooper pair pump. A fixed amount of Berry phase is accumulated to the quantum-mechanical ground state in each adiabatic pumping cycle, which is determined by measuring the charge passing through the device. The dynamic and geometric phases are identified and measured quantitatively from their different response when pumping in opposite directions. Our observations, in particular, the dependencies of the dynamic and geom...

  9. Subtleties of the clock retardation

    OpenAIRE

    Redzic, D. V.

    2015-01-01

    For a simple electromagnetic model of a clock introduced by Jefimenko (clock $\\#$ 1 in 1996 {\\it Am. J. Phys.} {\\bf 64} 812), a change of the rate of the clock when it is set in uniform motion is calculated exactly, employing the correct equation of motion of a charged particle in the electromagnetic field and the universal boostability assumption. Thus, for the clock under consideration, a dynamical content of the clock retardation is demonstrated. Somewhat surprisingly, the analysis present...

  10. The determination of Si-SiO2 interface trap density in irradiated four-terminal VDMOSFETS using charge pumping

    International Nuclear Information System (INIS)

    The utility of charge pumping to measure Si-SiO2 interface trap density in irradiated four-terminal VDMOSFETs is demonstrated. A modification of the conventional charge pumping approach is employed, where recombination of charge through interface traps in the neck region is measured in the drain. Three components of drain current resulting from the charge pumping measurement are identified. When the device is properly biased, charge pumping current can be separated from the other components of drain current and modeled over a wide range of interface trap densities using standard charge pumping theory. When sources of error are accounted for, radiation-induced interface trap densities measured with charge pumping are in good quantitative agreement with those estimated with the midgap charge separation and subthreshold hump techniques

  11. Defect diagnosis and root cause analysis for thrust roller bearing of centrifugal charging pump

    International Nuclear Information System (INIS)

    The centrifugal charging pump is one of the most important equipment for Nuclear power plant which requires very high reliability, during C9 fuel-cycle, the continuous high level vibration alarm happened on the centrifugal charging pump B, we diagnosed its faults correctly and selected the right operation mode and right time to dismantle it which ensure the safety and economic benefits of Nuclear power plant, and through deeply analysis the root causes of thrust bearing defaults, we can learn much from it especially for the diagnosis and analysis to the bearing faults which is common for rotating equipment. (author)

  12. Development of Discrete Power Supply with Charge Pump Method for High Powered Sonar System

    Directory of Open Access Journals (Sweden)

    Kristian Ismail

    2012-07-01

    Full Text Available Power supply is one of the electronic devices that can provide electric energy for electronic systems or other systems. There are several types of power supplies that can be applied depend on the requirement and functions. One example is the use of power supply for sonar systems. Sonar system is a device which can be used to detect a target under water. The sonar system is an electronic circuit that requires a power supply with specific characteristics when the sonar functions as a transmitter and a receiver in the specific span time (when on and the specific lag time (when off. This paper discusses the design of power supply for high-powered sonar systems with discrete methods in which high power supply is only applied when the acoustic waves radiated under water. Charge pump was used to get the appropriate output voltage from lower input voltage. Charge pump utilized a combination of series and parallel connections of capacitors. The working mode of this power supply used the lag time as the calculation of time to charge charge pump capacitors in parallel while the span time was used for the calculation of discharging the charge pump capacitors in series.

  13. Application and discussion of charging pump decontamination for pressurized water reactor nuclear power station

    International Nuclear Information System (INIS)

    This paper reports the process of charging pump decontamination during the refueling outage of nuclear power station. The phenomena and results of Martensite stainless steel decontamination were discussed and analyzed. By summarizing the successful experience of decontamination, some suggestions for future work were offered. (authors)

  14. Subterahertz acoustical pumping of electronic charge in a resonant tunneling device.

    Science.gov (United States)

    Young, E S K; Akimov, A V; Henini, M; Eaves, L; Kent, A J

    2012-06-01

    We demonstrate that controlled subnanosecond bursts of electronic charge can be transferred through a resonant tunneling diode by successive picosecond acoustic pulses. The effect exploits the nonlinear current-voltage characteristics of the device and its asymmetric response to the compressive and tensile components of the strain pulse. This acoustoelectronic pump opens new possibilities for the control of quantum phenomena in nanostructures. PMID:23003634

  15. Effect of clocking position of inducer on hydraulic characteristics of centrifugal pump%诱导轮时序位置对离心泵水力性能的影响

    Institute of Scientific and Technical Information of China (English)

    卢金玲; 邓佳; 徐益荣; 冯建军; 罗兴锜

    2015-01-01

    Different circumferential positions of stator/stator, rotor/rotor, stator /rotor have different wake vortex, which has different effects on the downstream blade boundary. This phenomenon is called clocking effect. The clocking effect has been widely used in the radial and axial pneumatic machinery, and the aerodynamic performance has been greatly improved. However, clocking effect is rarely used in hydraulic machinery, especially for hydraulic machinery with inducer. For the viscosity of the water is much larger than that of most gases, large trail vortex may occur at the downstream of vanes of hydraulic machinery, even at low flow velocity. When entering the impeller, this kind of vortex may further develop and mix with each other in the impeller. New vortex may be brought out downstream of the impeller, resulting in a greater impact on overall performance. Thus, the clocking effects may play a more important role in hydraulic machinery than pneumatic machinery. In order to study the influence of clocking effect on centrifugal pump, a single-stage centrifugal pump was selected as the study object, and three-dimensional unsteady viscous numerical method was applied to simulate inner flow in the centrifugal pump at 3 different clocking positions of inducer relative to impeller. The pump mainly consisted of inlet pipe, inducer, impeller, diffuser and outlet pipe. When the angle between reference blade of inducer and reference blade of impeller was 53°, the relative circumferential position was called clocking position 0, named CL0; the clocking position number increased by 1 every increase of 40° clockwise. External characteristics, cavitation characteristics and vibration characteristics were analyzed. It was found that the external characteristics of centrifugal pump were greatly influenced by clocking effects. With the change of clocking position, the head and efficiency of pump first increased and then decreased; the head and efficiency were the highest at CL1

  16. Non-adiabatic quantized charge pumping with tunable-barrier quantum dots: a review of current progress

    OpenAIRE

    Kaestner, Bernd; Kashcheyevs, Vyacheslavs

    2014-01-01

    Precise manipulation of individual charge carriers in nanoelectronic circuits underpins practical applications of their most basic quantum property --- the universality and invariance of the elementary charge. A charge pump generates a net current from periodic external modulation of parameters controlling a nanostructure connected to source and drain leads; in the regime of quantized pumping the current varies in steps of $q_e f$ as function of control parameters, where $q_e$ is the electron...

  17. Mono-parametric quantum charge pumping: Interplay between spatial interference and photon-assisted tunneling

    International Nuclear Information System (INIS)

    We analyze quantum charge pumping in an open ring with a dot embedded in one of its arms. We show that cyclic driving of the dot levels by a single parameter leads to a pumped current when a static magnetic flux is simultaneously applied to the ring. Based on the computation of the Floquet-Green's functions, we show that for low driving frequencies ω0, the interplay between the spatial interference through the ring plus photon-assisted tunneling gives an average direct current (dc) which is proportional to ω02. (author)

  18. Non-adiabatic quantized charge pumping with tunable-barrier quantum dots: a review of current progress

    Science.gov (United States)

    Kaestner, Bernd; Kashcheyevs, Vyacheslavs

    2015-10-01

    Precise manipulation of individual charge carriers in nanoelectronic circuits underpins practical applications of their most basic quantum property—the universality and invariance of the elementary charge. A charge pump generates a net current from periodic external modulation of parameters controlling a nanostructure connected to source and drain leads; in the regime of quantized pumping the current varies in steps of {{q}\\text{e}} f as function of control parameters, where {{q}\\text{e}} is the electron charge and f is the frequency of modulation. In recent years, robust and accurate quantized charge pumps have been developed based on semiconductor quantum dots with tunable tunnel barriers. These devices allow modulation of charge exchange rates between the dot and the leads over many orders of magnitude and enable trapping of a precise number of electrons far away from equilibrium with the leads. The corresponding non-adiabatic pumping protocols focus on understanding of separate parts of the pumping cycle associated with charge loading, capture and release. In this report we review realizations, models and metrology applications of quantized charge pumps based on tunable-barrier quantum dots.

  19. Non-adiabatic quantized charge pumping with tunable-barrier quantum dots: a review of current progress.

    Science.gov (United States)

    Kaestner, Bernd; Kashcheyevs, Vyacheslavs

    2015-10-01

    Precise manipulation of individual charge carriers in nanoelectronic circuits underpins practical applications of their most basic quantum property--the universality and invariance of the elementary charge. A charge pump generates a net current from periodic external modulation of parameters controlling a nanostructure connected to source and drain leads; in the regime of quantized pumping the current varies in steps of [Formula: see text] as function of control parameters, where [Formula: see text] is the electron charge and f is the frequency of modulation. In recent years, robust and accurate quantized charge pumps have been developed based on semiconductor quantum dots with tunable tunnel barriers. These devices allow modulation of charge exchange rates between the dot and the leads over many orders of magnitude and enable trapping of a precise number of electrons far away from equilibrium with the leads. The corresponding non-adiabatic pumping protocols focus on understanding of separate parts of the pumping cycle associated with charge loading, capture and release. In this report we review realizations, models and metrology applications of quantized charge pumps based on tunable-barrier quantum dots. PMID:26394066

  20. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump

    Directory of Open Access Journals (Sweden)

    Yixing Chu

    2016-03-01

    Full Text Available This paper presents a novel digital closed loop microelectromechanical system (MEMS accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg.

  1. On-chip high-voltage generator design design methodology for charge pumps

    CERN Document Server

    Tanzawa, Toru

    2016-01-01

    This book provides various design techniques for switched-capacitor on-chip high-voltage generators, including charge pump circuits, regulators, level shifters, references, and oscillators.  Readers will see these techniques applied to system design in order to address the challenge of how the on-chip high-voltage generator is designed for Flash memories, LCD drivers, and other semiconductor devices to optimize the entire circuit area and power efficiency with a low voltage supply, while minimizing the cost.  This new edition includes a variety of useful updates, including coverage of power efficiency and comprehensive optimization methodologies for DC-DC voltage multipliers, modeling of extremely low voltage Dickson charge pumps, and modeling and optimum design of AC-DC switched-capacitor multipliers for energy harvesting and power transfer for RFID.

  2. Charge pumping and noise in a one-dimensional wire with weak electron-electron interactions

    OpenAIRE

    Devillard, Pierre; Gasparian, Vladimir; Martin, Thierry

    2008-01-01

    We consider the adiabatic pumping of charge through a mesoscopic one dimensional wire in the presence of electron-electron interactions. A two-delta potential model is used to describe the wire, which allows to obtain exactly the scattering matrix coefficients, which are renormalized by the interactions. Two periodic drives, shifted one from another, are applied at two locations of the wire in order to drive a current through it in the absence of bias. Analytical expressions are obtained for ...

  3. Novel charge pump converter with Tunnel FET devices for ultra-low power energy harvesting sources

    OpenAIRE

    Nunes Cavalheiro, David Manuel; Moll Echeto, Francisco de Borja; Valtchev, Stanimir

    2015-01-01

    Compared to conventional technologies, the superior electrical characteristics of III-V Tunnel FET (TFET) devices can highly improve the process of energy harvesting conversion at ultra-low input voltage operation (sub-0.25V). In order to extend the input voltage/power range of operation in conventional charge pump topologies with TFET devices, it is of the major importance to reduce the band-to-band tunneling current when the transistor is under reverse bias conditions. This paper p...

  4. A dual mode charge pump with adaptive output used in a class G audio power amplifier

    International Nuclear Information System (INIS)

    A dual mode charge pump to produce an adaptive power supply for a class G audio power amplifier is presented. According to the amplitude of the input signals, the charge pump has two level output voltage rails available to save power. It operates both in current mode at high output load and in pulse frequency modulation (PFM) at light load to reduce the power dissipation. Also, dynamic adjustment of the power stage transistor size based on load current at the PFM mode is introduced to reduce the output voltage ripple and prevent the switching frequency from audio range. The prototype is implemented in 0.18 μm 3.3 V CMOS technology. Experimental results show that the maximum power efficiency of the charge pump is 79.5% - 0.5x mode and 83.6% - 1x mode. The output voltage ripple is less than 15 mV while providing 120 mA of the load current at PFM control and less than 18 mV while providing 300 mA of the load current at current mode control. An analytical model for ripple voltage and efficiency calculation of the proposed PFM control demonstrates reasonable agreement with measured results. (semiconductor integrated circuits)

  5. A dual mode charge pump with adaptive output used in a class G audio power amplifier

    Science.gov (United States)

    Yong, Feng; Zhenfei, Peng; Shanshan, Yang; Zhiliang, Hong; Yang, Liu

    2011-04-01

    A dual mode charge pump to produce an adaptive power supply for a class G audio power amplifier is presented. According to the amplitude of the input signals, the charge pump has two level output voltage rails available to save power. It operates both in current mode at high output load and in pulse frequency modulation (PFM) at light load to reduce the power dissipation. Also, dynamic adjustment of the power stage transistor size based on load current at the PFM mode is introduced to reduce the output voltage ripple and prevent the switching frequency from audio range. The prototype is implemented in 0.18 μm 3.3 V CMOS technology. Experimental results show that the maximum power efficiency of the charge pump is 79.5% @ 0.5x mode and 83.6% @ 1x mode. The output voltage ripple is less than 15 mV while providing 120 mA of the load current at PFM control and less than 18 mV while providing 300 mA of the load current at current mode control. An analytical model for ripple voltage and efficiency calculation of the proposed PFM control demonstrates reasonable agreement with measured results.

  6. Adiabatic and non-adiabatic charge pumping in a single-level molecular motor

    International Nuclear Information System (INIS)

    We propose a design for realizing quantum charge pump based on a recent proposal for a molecular motor (Seldenthuis J S et al 2010 ACS Nano 4 6681). Our design is based on the presence of a moiety with a permanent dipole moment which can rotate, thereby modulating the couplings to metallic contacts at both ends of the molecule. Using the non-equilibrium Keldysh Green’s function formalism (NEGF), we show that our design indeed generates a pump current. In the non-interacting pump, the variation of frequency from adiabatic to non-adiabatic regime, can be used to control the direction as well as the amplitude of the average current. The effect of Coulomb interaction is considered within the first- and the second- order perturbation. The numerical implementation of the scheme is quite demanding, and we develop an analytical approximation to obtain a speed-up giving results within a reasonable time. We find that the amplitude of the average pumped current can be controlled by both the driving frequency and the Coulomb interaction. The direction of of pumped current is shown to be determined by the phase difference between left and right anchoring groups. (paper)

  7. Self-generating magnetometer with laser pumping employment in “end resonance” wall coated vapor cell atomic clocks

    Science.gov (United States)

    Baranov, A. A.; Ermak, S. V.; Smolin, R. V.; Semenov, V. V.

    2016-06-01

    This paper presents the results of two double resonance signals correlation investigation. These signals were observed synchronously in optically oriented Rb87 vapors with laser pumping in a dual scheme: low frequency Mx-magnetometer and microwave frequency discriminator. Analytical studies of the scalar and vector light shift components contribution to the frequency instability of the end resonance microwave transitions are presented. An experimental demonstration of the light shift components mutual compensation in optically pumped Rb87 atoms was provided. The results were processed in terms of Allan variance, which demonstrated an effect of decreasing frequency variation at averaging times more than 100 s for a joint scheme of the end resonance microwave transition and selfgenerating (Mx) magnetometer.

  8. Iodine laser pumped with light from a shock front produced by explosive charge detonation

    Energy Technology Data Exchange (ETDEWEB)

    Arzhanov, V.P.; Borovich, B.L.; Zuev, V.S.; Kazanskii, V.M.; Katulin, V.A.; Kirillov, G.A.; Kormer, S.B.; Kuratov, IU.V.; Kuriapin, A.I.; Nosach, O.IU. (VNII Eksperimental' noi Fiziki, Arzamas (Russian Federation) Fizicheskii Inst., Moscow (Russian Federation))

    1992-02-01

    The paper presents results of experimental research undertaken during 1965-1966 which concerned a pulsed photodissociation iodine laser using CF3I and C3F7I molecules pumped with light from a shock front produced by explosive charge detonation. These lasers are shown to feature a unique combination of the high energy and the high power of the radiation pulse. Two types of lasers were investigated, in one of which the active medium was pumped with light from the shock front in xenon, while in the other the shock wave propagated through a mixture of the active medium with a rare gas. The energy characteristics of the second type of laser substantially surpassed those of the first type of laser. 6 refs.

  9. On-site vibration fault diagnosis and solution measures of a centrifugal charging pump in nuclear power plant

    International Nuclear Information System (INIS)

    Vibration measurement of equipment during commissioning of nuclear power plants is one of important measures to ensure the plant safety. In this paper, through vibration measurement of the centrifugal charging pump during commission of a certain nuclear power plant, vibration fault of the pump is found. According to the signal features measured, faults of mass unbalance and uneven torque for the foundation bolts are diagnosed, and corresponding measures are implemented, which finally solve the vibration problem of this pump. The diagnosis process of the pump demonstrates that vibration faults of on-site equipment often have several causes, and even the same symptoms have different reasons. The vibration problem of the centrifugal charging pump in this paper is meaningful for solving practical engineering problems, and will provide important instructions and reference for disposing similar problems. (authors)

  10. Spatially resolved charge exchange flux calculations on the Toroidal Pumped Limiter of Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Marandet, Y., E-mail: yannick.marandet@piim.up.univ-mrs.f [PIIM, CNRS/Universite de Provence, Marseille (France); Tsitrone, E. [Association Euratom-CEA, CEA/DSM/DRFC CEA Cadarache (France); Boerner, P.; Reiter, D. [IEF-4 Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, TEC (Germany); Beaute, A.; Delchambre, E. [Association Euratom-CEA, CEA/DSM/DRFC CEA Cadarache (France); Escarguel, A. [PIIM, CNRS/Universite de Provence, Marseille (France); Brezinsek, S. [IEF-4 Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, TEC (Germany); Genesio, P. [PIIM, CNRS/Universite de Provence, Marseille (France); Gunn, J.; Monier-Garbet, P.; Mitteau, R.; Pegourie, B. [Association Euratom-CEA, CEA/DSM/DRFC CEA Cadarache (France)

    2009-06-15

    A spatially resolved calculation of the charge exchange particle and energy fluxes on the Toroidal Pumped Limiter (TPL) of Tore Supra is presented, as a first step towards a better understanding and modelling of carbon erosion, migration, as well as deuterium codeposition and bulk diffusion of deuterium in Tore Supra. The results are obtained with the EIRENE code run in a 3D geometry. Physical and chemical erosion maps on the TPL are calculated, and the contribution of neutrals to erosion, especially in the self-shadowed area, is calculated.

  11. Non-linear behaviour of charge-pump phase-locked loops

    OpenAIRE

    C. Wiegand; Hedayat, C.; U. Hilleringmann

    2010-01-01

    The analysis of the mixed analogue and digital structure of charge-pump phase-locked loops (CP-PLL) is a challenge in modelling and simulation. In most cases the system is designed and characterized using its continuous linear model or its discrete linear model neglecting its non-linear switching behaviour. I.e., the time-varying model is approximated by a time-invariant representation using its average dynamics. Depending on what kind of phase detector is used, the scopes o...

  12. Multi-frequency inversion-charge pumping for charge separation and mobility analysis in high-k/InGaAs metal-oxide-semiconductor field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Djara, V.; Cherkaoui, K.; Negara, M. A.; Hurley, P. K., E-mail: paul.hurley@tyndall.ie [Tyndall National Institute, University College Cork, Dyke Parade, Cork (Ireland)

    2015-11-28

    An alternative multi-frequency inversion-charge pumping (MFICP) technique was developed to directly separate the inversion charge density (N{sub inv}) from the trapped charge density in high-k/InGaAs metal-oxide-semiconductor field-effect transistors (MOSFETs). This approach relies on the fitting of the frequency response of border traps, obtained from inversion-charge pumping measurements performed over a wide range of frequencies at room temperature on a single MOSFET, using a modified charge trapping model. The obtained model yielded the capture time constant and density of border traps located at energy levels aligned with the InGaAs conduction band. Moreover, the combination of MFICP and pulsed I{sub d}-V{sub g} measurements enabled an accurate effective mobility vs N{sub inv} extraction and analysis. The data obtained using the MFICP approach are consistent with the most recent reports on high-k/InGaAs.

  13. Multi-frequency inversion-charge pumping for charge separation and mobility analysis in high-k/InGaAs metal-oxide-semiconductor field-effect transistors

    International Nuclear Information System (INIS)

    An alternative multi-frequency inversion-charge pumping (MFICP) technique was developed to directly separate the inversion charge density (Ninv) from the trapped charge density in high-k/InGaAs metal-oxide-semiconductor field-effect transistors (MOSFETs). This approach relies on the fitting of the frequency response of border traps, obtained from inversion-charge pumping measurements performed over a wide range of frequencies at room temperature on a single MOSFET, using a modified charge trapping model. The obtained model yielded the capture time constant and density of border traps located at energy levels aligned with the InGaAs conduction band. Moreover, the combination of MFICP and pulsed Id-Vg measurements enabled an accurate effective mobility vs Ninv extraction and analysis. The data obtained using the MFICP approach are consistent with the most recent reports on high-k/InGaAs

  14. Electrical detection of ferromagnetic resonance in single layers of permalloy: Evidence of magnonic charge pumping

    Science.gov (United States)

    Azevedo, A.; Cunha, R. O.; Estrada, F.; Alves Santos, O.; Mendes, J. B. S.; Vilela-Leão, L. H.; Rodríguez-Suárez, R. L.; Rezende, S. M.

    2015-07-01

    The generation of a DC voltage in single layers of permalloy (Ni81Fe19 ) when the magnetization is undergoing ferromagnetic resonance is investigated in a series of samples with thickness varying from 4.0 to 150 nm. By sweeping the external field at a fixed microwave frequency, we measure a DC voltage at the ends of the layer as a function of the in-plane angle for each sample. The asymmetric voltage signal generated at the resonance field is a superposition of symmetric Lorentzian and antisymmetric Lorentzian derivative line shapes. The in-plane dependence of both symmetric and antisymmetric signals cannot be explained as due to spin rectification (SRE) only. The results are well explained by a model that takes into account in addition to the SRE the contribution of the recent discovered effect of magnonic charge pumping that converts magnetization dynamics into charge current by means of the spin orbit coupling.

  15. Time-resolved HAXPES at SACLA: probe and pump pulse-induced space-charge effects

    International Nuclear Information System (INIS)

    Time-resolved hard x-ray photoelectron spectroscopy (trHAXPES) is established using the x-ray free-electron laser SACLA. The technique extends time-resolved photoemission into the hard x-ray regime and, as a core-level spectroscopy, combines element and atomic-site specificity and sensitivity to the chemical environment with femtosecond time resolution and bulk (sub-surface) sensitivity. The viability of trHAXPES using 8 keV x-ray free-electron-laser radiation is demonstrated by a systematic investigation of probe and pump pulse-induced vacuum space-charge effects on the V 1s emission of VO2 and the Ti 1s emission of SrTiO3. The time and excitation energy dependencies of the measured spectral shifts and broadenings are compared to the results of N-body numerical simulations and simple analytic (mean-field) models. Good agreement between the experimental and calculated results is obtained. In particular, the characteristic temporal evolution of the pump pulse-induced spectral shift is shown to provide an effective means to determine the temporal overlap of pump and probe pulses. trHAXPES opens a new avenue in the study of ultrafast atomic-site specific electron and chemical dynamics in materials and at buried interfaces. (paper)

  16. Design and noise analysis of a fully-differential charge pump for phase-locked loops

    International Nuclear Information System (INIS)

    A fully-differential charge pump (FDCP) with perfect current matching and low output current noise is realized for phase-locked loops (PLLs). An easily stable common-mode feedback (CMFB) circuit which can handle high input voltage swing is proposed. Current mismatch and current noise contribution from the CMFB circuit is minimized. In order to optimize PLL phase noise, the output current noise of the FDCP is analyzed in detail and calculated with the sampling principle. The calculation result agrees well with the simulation. Based on the noise analysis, many methods to lower output current noise of the FDCP are discussed. The fully-differential charge pump is integrated into a 1-2 GHz frequency synthesizer and fabricated in an SMIC CMOS 0.18 μm process. The measured output reference spur is -64 dBc to -69 dBc. The in-band and out-band phase noise is -95 dBc/Hz at 3 kHz frequency offset and -123 dBc/Hz at 1 MHz frequency offset respectively.

  17. A novel low ripple charge pump with a 2X/1.5X booster for PCM

    International Nuclear Information System (INIS)

    A low ripple switched capacitor charge pump applicable to phase change memory (PCM) is presented. For high power efficiency, the selected charge pump topology can automatically change the power conversion ratio between 2X/1.5X modes with the input voltage. For a low output ripple, a novel operation mode is used. Compared with the conventional switched capacitor charge pump, the flying capacitor of the proposed charge pump is charged to Vo − Vin during the charge phase (Vo is the prospective output voltage). In the discharge phase, the flying capacitor is placed in series with the Vin to transfer energy to the output, so the output voltage is regulated at Vo. A simulation was implemented for a DC input range of 1.6–2.1 V in on SMIC standard 40 nm CMOS process, the result shows that the new operation mode could regulate the output of about 2.5 V with a load condition from 0 to 10 mA, and the ripple voltage is lower than 4 mV. The maximum power efficiency reaches 91%. (semiconductor integrated circuits)

  18. A novel low ripple charge pump with a 2X/1.5X booster for PCM

    Institute of Scientific and Technical Information of China (English)

    Fu Cong; Song Zhitang; Chen Houpeng; Cai Daolin; Wang Qian; Hong Xiao; Ding Sheng; Li Xi

    2012-01-01

    A low ripple switched capacitor charge pump applicable to phase change memory (PCM) is presented.For high power efficiency,the selected charge pump topology can automatically change the power conversion ratio between 2X/1.5X modes with the input voltage.For a low output ripple,a novel operation mode is used.Compared with the conventional switched capacitor charge pump,the flying capacitor of the proposed charge pump is chargedc to Vo- Vin during the charge phase (Vo is the prospective output voltage).In the discharge phase,the flying capacitor is placed in series with the Vin to transfer energy to the output,so the output voltage is regulated at Vo.A simulation was implemented for a DC input range of 1.6-2.1V in on SMIC standard 40 nm CMOS process,the result shows that the new operation mode could regulate the output of about 2.5 V with a load condition from 0 to 10 mA,and the ripple voltage is lower than 4 mV.The maximum power efficiency reaches 91%.

  19. Non-linear behaviour of charge-pump phase-locked loops

    Science.gov (United States)

    Wiegand, C.; Hedayat, C.; Hilleringmann, U.

    2010-10-01

    The analysis of the mixed analogue and digital structure of charge-pump phase-locked loops (CP-PLL) is a challenge in modelling and simulation. In most cases the system is designed and characterized using its continuous linear model or its discrete linear model neglecting its non-linear switching behaviour. I.e., the time-varying model is approximated by a time-invariant representation using its average dynamics. Depending on what kind of phase detector is used, the scopes of validity of these approximations are different. Here, a preeminent characterization and simulation technique based on the systems event-driven feature is presented, merging the logical and analogue inherent characteristics of the system. In particular, the high-grade non-linear locking process and the dead-zone are analyzed.

  20. Analysis of electron capture process in charge pumping sequence using time domain measurements

    International Nuclear Information System (INIS)

    A method for analyzing the electron capture process in the charge pumping (CP) sequence is proposed and demonstrated. The method monitors the electron current in the CP sequence in time domain. This time-domain measurements enable us to directly access the process of the electron capture to the interface defects, which are obscured in the conventional CP method. Using the time-domain measurements, the rise time dependence of the capture process is systematically investigated. We formulate the capture process based on the rate equation and derive an analytic form of the current due to the electron capture to the defects. Based on the formula, the experimental data are analyzed and the capture cross section is obtained. In addition, the time-domain data unveil that the electron capture process completes before the electron channel opens, or below the threshold voltage in a low frequency range of the pulse

  1. GOTHIC Simulation of APR1400 Auxiliary Charging Pump room heat up

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Hui-Un; Heo, Sun [KHNP, Daejeon (Korea, Republic of)

    2014-10-15

    As a part of the Advanced Power Reactor 1400 (APR1400) U. S. Nuclear Regulatory Commission Design Certification (NRC DC) project, we have been investigating Auxiliary Charging Pump (ACP) room heat up. With reference to the design specification of the ACP room, we determined input information and developed a GOTHIC model of the APR1400 ACP room. This calculation model is described herein, and representative results from the calculation are presented as well. The results of the present paper are used to determine the integrity of ACP operating in the accident. APR 1400 GOTHIC model was developed for ACP room heat up calculation. Calculation results confirm that door opening is cooling the room properly. It is found that the difference due to the surface option of heat conductors is insignificant. Based on this result, further studies should be performed to confirm integrity of ACP.

  2. A low jitter supply regulated charge pump PLL with self-calibration

    Science.gov (United States)

    Min, Chen; Yuntao, Liu; Zhichao, Li; Jingbo, Xiao; Jie, Chen

    2016-01-01

    This paper describes a ring oscillator based low jitter charge pump PLL with supply regulation and digital calibration. In order to combat power supply noise, a low drop output voltage regulator is implemented. The VCO gain is tunable by using the 4 bit control self-calibration technique. So that the optimal VCO gain is automatically selected and the process/temperature variation is compensated. Fabricated in the 0.13 μm CMOS process, the PLL achieves a frequency range of 100-400 MHz and occupies a 190 × 200 μm2 area. The measured RMS jitter is 5.36 ps at a 400 MHz operating frequency. Project supported by the National Key Basic Research and Development Program of China (No. 2015CB352100).

  3. Reservoir induced topological order and quantized charge pumps in open lattice models with interactions

    Science.gov (United States)

    Linzner, Dominik; Koster, Malte; Grusdt, Fabian; Fleischhauer, Michael

    2016-05-01

    Since the discovery of the quantum Hall effect, topological states of matter have attracted the attention of scientists in many fields of physics. By now there is a rather good understanding of topological order in closed, non-interacting systems. In contrast the extension to open systems in particular with interactions is entirely in its infancy. Recently there have been advances in characterizing topology in reservoir driven systems without interactions, but the topological invariants introduced lack a clear physical interpretation and are restricted to non-interacting systems. We consider a one-dimensional interacting topological system whose dynamics is entirely driven by reservoir couplings. By slowly tuning these couplings periodically in time we realize an open-system analogue of the Thouless charge pump that proves to be robust against unitary and non-unitary perturbations. Making use of this Thouless pump we introduce a topological invariant, which is applicable to interacting systems. Finally we propose a conceptual detection scheme that translates the open-system topological invariant into the context of a well understood closed system.

  4. Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy

    Science.gov (United States)

    Oloff, L.-P.; Hanff, K.; Stange, A.; Rohde, G.; Diekmann, F.; Bauer, M.; Rossnagel, K.

    2016-06-01

    With the advent of ultrashort-pulsed extreme ultraviolet sources, such as free-electron lasers or high-harmonic-generation (HHG) sources, a new research field for photoelectron spectroscopy has opened up in terms of femtosecond time-resolved pump-probe experiments. The impact of the high peak brilliance of these novel sources on photoemission spectra, so-called vacuum space-charge effects caused by the Coulomb interaction among the photoemitted probe electrons, has been studied extensively. However, possible distortions of the energy and momentum distributions of the probe photoelectrons caused by the low photon energy pump pulse due to the nonlinear emission of electrons have not been studied in detail yet. Here, we systematically investigate these pump laser-induced space-charge effects in a HHG-based experiment for the test case of highly oriented pyrolytic graphite. Specifically, we determine how the key parameters of the pump pulse—the excitation density, wavelength, spot size, and emitted electron energy distribution—affect the measured time-dependent energy and momentum distributions of the probe photoelectrons. The results are well reproduced by a simple mean-field model, which could open a path for the correction of pump laser-induced space-charge effects and thus toward probing ultrafast electron dynamics in strongly excited materials.

  5. High-precision high-sensitivity clock recovery circuit for a mobile payment application

    International Nuclear Information System (INIS)

    This paper presents a fully integrated carrier clock recovery circuit for a mobile payment application. The architecture is based on a sampling-detection module and a charge pump phase locked loop. Compared with clock recovery in conventional 13.56 MHz transponders, this circuit can recover a high-precision consecutive carrier clock from the on/off keying (OOK) signal sent by interrogators. Fabricated by a SMIC 0.18-μm EEPROM CMOS process, this chip works from a single power supply as low as 1.5 V Measurement results show that this circuit provides 0.34% frequency deviation and 8 mV sensitivity. (semiconductor integrated circuits)

  6. A power management system for energy harvesting and wireless sensor networks application based on a novel charge pump circuit

    Science.gov (United States)

    Aloulou, R.; De Peslouan, P.-O. Lucas; Mnif, H.; Alicalapa, F.; Luk, J. D. Lan Sun; Loulou, M.

    2016-05-01

    Energy Harvesting circuits are developed as an alternative solution to supply energy to autonomous sensor nodes in Wireless Sensor Networks. In this context, this paper presents a micro-power management system for multi energy sources based on a novel design of charge pump circuit to allow the total autonomy of self-powered sensors. This work proposes a low-voltage and high performance charge pump (CP) suitable for implementation in standard complementary metal oxide semiconductor (CMOS) technologies. The CP design was implemented using Cadence Virtuoso with AMS 0.35μm CMOS technology parameters. Its active area is 0.112 mm2. Consistent results were obtained between the measured findings of the chip testing and the simulation results. The circuit can operate with an 800 mV supply and generate a boosted output voltage of 2.835 V with 1 MHz as frequency.

  7. Modeling Improvements for Air Source Heat Pumps using Different Expansion Devices at Varied Charge Levels Part II

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Bo [ORNL

    2011-01-01

    This paper describes steady-state performance simulations performed on a 3-ton R-22 split heat pump in heating mode. In total, 150 steady-state points were simulated, which covers refrigerant charge levels from 70 % to 130% relative to the nominal value, the outdoor temperatures at 17 F (-8.3 C), 35 F (1.7 C) and 47 F (8.3 C), indoor air flow rates from 60% to 150% of the rated air flow rate, and two types of expansion devices (fixed orifice and thermostatic expansion valve). A charge tuning method, which is to calibrate the charge inventory model based on measurements at two operation conditions, was applied and shown to improve the system simulation accuracy significantly in an extensive range of charge levels. In addition, we discuss the effects of suction line accumulator in modeling a heat pump system using either a fixed orifice or thermal expansion valve. Last, we identify the issue of refrigerant mass flow mal-distribution at low charge levels and propose an improved modeling approach.

  8. Body Clock

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2000-01-01

    “Body clocks” are biological methods of controling body activities.Every living thing has one. In humans, a body clock controls normal periods of sleeping and waking. It controls the time swhen you are most likely to feel pain.Eating, sleeping and exercising at about the same time each day will help keep body activities normal. But changes in your life, a new job, for example, destroy the balance and thus cause health problems.

  9. Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator: α -Sn Films

    Science.gov (United States)

    Rojas-Sánchez, J.-C.; Oyarzún, S.; Fu, Y.; Marty, A.; Vergnaud, C.; Gambarelli, S.; Vila, L.; Jamet, M.; Ohtsubo, Y.; Taleb-Ibrahimi, A.; Le Fèvre, P.; Bertran, F.; Reyren, N.; George, J.-M.; Fert, A.

    2016-03-01

    We present results on spin to charge current conversion in experiments of resonant spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) α -Sn. By angle-resolved photoelectron spectroscopy (ARPES), we first check that the Dirac cone (DC) at the α -Sn (0 0 1) surface subsists after covering Sn with Ag. Then we show that resonant spin pumping at room temperature from Fe through Ag into α -Sn layers induces a lateral charge current that can be ascribed to the inverse Edelstein effect by the DC states. Our observation of an inverse Edelstein effect length much longer than those generally found for Rashba interfaces demonstrates the potential of TIs for the conversion between spin and charge in spintronic devices. By comparing our results with data on the relaxation time of TI free surface states from time-resolved ARPES, we can anticipate the ultimate potential of the TI for spin to charge conversion and the conditions to reach it.

  10. Charge pumping in monolayer graphene driven by a series of time-periodic potentials

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhenhua, E-mail: zhwu@semi.ac.cn [SKLSM, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, 100083, Beijing (China); CAE Team, Semiconductor R and D Center, Samsung Electronics Co. Ltd., Gyeonggi-Do (Korea, Republic of); Li, J. [Department of Physics, Semiconductor Photonics Research Center, Xiamen University, Xiamen 361005 (China); Chan, K.S., E-mail: apkschan@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

    2012-02-27

    We applied the Floquet scattering-matrix formalism to studying the electronic transport properties in a mesoscopic Dirac system. Using the method, we investigate theoretically quantum pumping driven by a series of time-periodic potentials in graphene monolayer both in the adiabatic and non-adiabatic regimes. Our numerical results demonstrate that adding harmonic modulated potentials can break the time reversal symmetry when no voltage bias is applied to the graphene monolayer. Thus, when the system is pumped with proper dynamic parameters, these scatterers can produce a nonzero dc pumped current. We also find that the transmission is anisotropic as the incident angle is changed. -- Highlights: ► We applied the Floquet scattering-matrix formalism to Dirac-electron system. ► We investigated the quantum pumping both in adiabatic and non-adiabatic regimes. ► We evaluated the pumped dc current induced by harmonic modulated potentials.

  11. Atomic Clocks

    Science.gov (United States)

    Wynands, Robert

    Time is a strange thing. On the one hand it is arguably the most inaccessible physical phenomenon of all: both in that it is impossible to manipulate or modify—for all we know—and in that even after thousands of years mankind's philosophers still have not found a fully satisfying way to understand it. On the other hand, no other quantity can be measured with greater precision. Today's atomic clocks allow us to reproduce the length of the second as the SI unit of time with an uncertainty of a few parts in 1016—orders of magnitude better than any other quantity. In a sense, one can say [1

  12. Experimental Investigation of Refrigerant Charge Minimisation of a Small Capacity Heat Pump

    OpenAIRE

    Fernando, W. Primal D.

    2007-01-01

    Enormous quantities of heat are available in air, soil, water, exhaust air from buildings, and in waste water of any kind. However these heat sources are use-less for heating purposes since their temperatures are lower than the tempera-ture required for heating. Heat pumps can be used to extract heat from these sources with a small expenditure of additional energy and up-grade and deliver the energy as useful heat for room heating. The heat pump cycle employs the well-known vapour compression...

  13. A 1-GHz charge pump PLL frequency synthesizer for IEEE 1394b PHY

    DEFF Research Database (Denmark)

    Ji, J.; Liu, H.; Li, Q.

    2012-01-01

    This paper presents an implementation of multi-rate SerDes transceiver for IEEE 1394b applications. Simple and effective pre-emphasis and equalizer circuits are used at transmitter and receiver, respectively. A phase interpolator based clock and data recovery circuit with optimized linearity is...... also described. With an on-chip fully integrated phase locked loop, the transceiver works at data rates of 100Mb/s, 400Mb/s and 800Mb/s, supporting three different operating modes of S100b, S400b and S800b for IEEE 1394b. The chip has been fabricated using 0.13μm technology. The die area of transceiver...

  14. An asymmetric MOSFET-C band-pass filter with on-chip charge pump auto-tuning

    International Nuclear Information System (INIS)

    An asymmetric MOSFET-C band-pass filter (BPF) with on chip charge pump auto-tuning is presented. It is implemented in UMC (United Manufacturing Corporation) 0.18 μm CMOS process technology. The filter system with auto-tuning uses a master-slave technique for continuous tuning in which the charge pump outputs 2.663 V, much higher than the power supply voltage, to improve the linearity of the filter. The main filter with third order low-pass and second order high-pass properties is an asymmetric band-pass filter with bandwidth of 2.730-5.340 MHz. The in-band third order harmonic input intercept point (IIP3) is 16.621 dBm, with 50 Ω as the source impedance. The input referred noise is about 47.455 μVrms. The main filter dissipates 3.528 mW while the auto-tuning system dissipates 2.412 mW from a 1.8 V power supply. The filter with the auto-tuning system occupies 0.592 mm2 and it can be utilized in GPS (global positioning system) and Bluetooth systems. (semiconductor integrated circuits)

  15. Spin-orbit-coupling induced torque in ballistic domain walls: Equivalence of charge-pumping and nonequilibrium magnetization formalisms

    Science.gov (United States)

    Yuan, Zhe; Kelly, Paul J.

    2016-06-01

    To study the effect of spin-orbit coupling (SOC) on spin-transfer torque in magnetic materials, we have implemented two theoretical formalisms that can accommodate SOC. Using the "charge-pumping" formalism, we find two contributions to the out-of-plane spin-transfer torque parameter β in ballistic Ni domain walls (DWs). For short DWs, the nonadiabatic reflection of conduction electrons caused by the rapid spatial variation of the exchange potential results in an out-of-plane torque that increases rapidly with decreasing DW length. For long DWs, the Fermi level conduction channel anisotropy that gives rise to an intrinsic DW resistance in the presence of SOC leads to a linear dependence of β on the DW length. To understand this counterintuitive divergence of β in the long DW limit, we use the "nonequilibrium magnetization" formalism to examine the spatially resolved spin-transfer torque. The SOC-induced out-of-plane torque in ballistic DWs is found to be quantitatively consistent with the values obtained using the charge-pumping calculations, indicating the equivalence of the two theoretical methods.

  16. An asymmetric MOSFET-C band-pass filter with on-chip charge pump auto-tuning

    Energy Technology Data Exchange (ETDEWEB)

    Chen Fangxiong; Ma Heping; Jia Hailong; Shi Yin [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Lin Min [Suzhou-CAS Semiconductors Integrated Technology Research Center, Suzhou 215021 (China); Dai, Forster, E-mail: fxchen@semi.ac.c [Department of Electrical and Computer Engineering, Auburn University, AL 36849 (United States)

    2009-08-15

    An asymmetric MOSFET-C band-pass filter (BPF) with on chip charge pump auto-tuning is presented. It is implemented in UMC (United Manufacturing Corporation) 0.18 {mu}m CMOS process technology. The filter system with auto-tuning uses a master-slave technique for continuous tuning in which the charge pump outputs 2.663 V, much higher than the power supply voltage, to improve the linearity of the filter. The main filter with third order low-pass and second order high-pass properties is an asymmetric band-pass filter with bandwidth of 2.730-5.340 MHz. The in-band third order harmonic input intercept point (IIP3) is 16.621 dBm, with 50 {Omega} as the source impedance. The input referred noise is about 47.455 {mu}V{sub rms}. The main filter dissipates 3.528 mW while the auto-tuning system dissipates 2.412 mW from a 1.8 V power supply. The filter with the auto-tuning system occupies 0.592 mm{sup 2} and it can be utilized in GPS (global positioning system) and Bluetooth systems. (semiconductor integrated circuits)

  17. High-Q Tunable Filters and High Efficiency Charge Pumps Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The supply voltages of modern baseband digital integrated circuits are well below the required actuation voltages for the MEMS tunable filters. Therefore, a charge...

  18. DESIGN OF TWO-PHASE SINUSOIDAL POWER CLOCK AND CLOCKED TRANSMISSION GATE ADIABATIC LOGIC CIRCUIT

    Institute of Scientific and Technical Information of China (English)

    Wang Pengjun; Yu Junjun

    2007-01-01

    First the research is conducted on the design of the two-phase sinusoidal power clock generator in this paper. Then the design of the new adiabatic logic circuit adopting the two-phase sinusoidal power clocks-Clocked Transmission Gate Adiabatic Logic (CTGAL) circuit is presented. This circuit makes use of the clocked transmission gates to sample the input signals, then the output loads are charged and discharged in a fully adiabatic manner by using bootstrapped N-Channel Metal Oxide Semiconductor (NMOS) and Complementary Metal Oxide Semiconductor (CMOS) latch structure.Finally, with the parameters of Taiwan Semiconductor Manufacturing Company (TSMC) 0.25 μm CMOS device, the transient energy consumption of CTGAL, Bootstrap Charge-Recovery Logic (BCRL)and Pass-transistor Adiabatic Logic (PAL) including their clock generators is simulated. The simulation result indicates that CTGAL circuit has the characteristic of remarkably low energy consumption.

  19. Increasing nuclear safety and operational reliability by upgrading the charging pump mechanical sealing system

    International Nuclear Information System (INIS)

    For the Ringhals-2 nuclear power plant, three installed centrifugal pumps were designated to have a combined High Head Safety Injection function, as well as a Chemical Volume Control System function. The pumps were originally installed with rubber bellow type mechanical seals, which over time had demonstrated an unreliable sealing performance by displaying high leakages. In 2002, the Ringhals Maintenance engineers initiated to identify a more reliable and robust shaft sealing solution. In 2007, the project was launched and the installation of the first, new mechanical sealing solution took place in the autumn of 2011. In October 2014, these mechanical seals were dismantled and inspected. The inspection confirmed the expected reliability of the new solution.

  20. Increasing nuclear safety and operational reliability by upgrading the charging pump mechanical sealing system

    Energy Technology Data Exchange (ETDEWEB)

    Loenhout, Gerard van [Flowserve Corporation, Etten-Leur (Netherlands); Nilsson, Peter [Flowsys Technologies AB, Moelndal (Sweden); Jehander, Magnus [Ringhals AB, Vaeroebacka (Sweden)

    2016-07-01

    For the Ringhals-2 nuclear power plant, three installed centrifugal pumps were designated to have a combined High Head Safety Injection function, as well as a Chemical Volume Control System function. The pumps were originally installed with rubber bellow type mechanical seals, which over time had demonstrated an unreliable sealing performance by displaying high leakages. In 2002, the Ringhals Maintenance engineers initiated to identify a more reliable and robust shaft sealing solution. In 2007, the project was launched and the installation of the first, new mechanical sealing solution took place in the autumn of 2011. In October 2014, these mechanical seals were dismantled and inspected. The inspection confirmed the expected reliability of the new solution.

  1. Increasing nuclear safety and operational reliability by upgrading the charging pump mechanical sealing system

    Energy Technology Data Exchange (ETDEWEB)

    Loenhout, Gerard van [Flowserve Corporation, Etten-Leur (Netherlands); Nilsson, Peter [Flowsys Technologies AB, Moelndal (Sweden); Jehander, Magnus [Ringhals AB, Vaeroebacka (Sweden)

    2016-03-15

    For the Ringhals-2 nuclear power plant, three installed centrifugal pumps were designated to have a combined High Head Safety Injection function, as well as a Chemical Volume Control System function. The pumps were originally installed with rubber bellow type mechanical seals, which over time had demonstrated an unreliable sealing performance by displaying high leakages. In 2002, the Ringhals Maintenance engineers initiated to identify a more reliable and robust shaft sealing solution. In 2007, the project was launched and the installation of the first, new mechanical sealing solution took place in the autumn of 2011. In October 2014, these mechanical seals were dismantled and inspected. The inspection confirmed the expected reliability of the new solution.

  2. Oil Coking Prevention Using Electric Water Pump for Turbo-Charge Spark-Ignition Engines

    OpenAIRE

    2014-01-01

    Turbocharger has been widely implemented for internal combustion engine to increase an engine's power output and reduce fuel consumption. However, its operating temperature would rise to 340°C when engine stalls. This higher temperature may results in bearing wear, run-out, and stick, due to oil coking and insufficient lubrication. In order to overcome these problems, this paper employs Electric Water Pump (EWP) to supply cool liquid to turbocharger actively when the engine stalls. The system...

  3. A radiation-hardened-by-design technique for improving single-event transient tolerance of charge pumps in PLLs

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhenyu; Zhang Minxuan; Chen Shuming; Chen Jihua; Li Junfeng

    2009-01-01

    A radiation-hardened-by-design (RHBD) technique for phase-locked loops (PLLs) has been developed for single-event transient (SET) mitigation. By presenting a novel SET-resistant complementary current limiter (CCL) and implementing it between the charge pump (CP) and the loop filter (LPF), the PLL's single-event suscepti-bility is significantly decreased in the presence of SETs in CPs, whereas it has little impact on the loop parameters in the absence of SETs in CPs. Transistor-level simulation results show that the CCL circuit can significantly reduce the voltage perturbation on the input of the voltage-controlled oscillator (VCO) by up to 93.1% and reduce the recovery time of the PLL by up to 79.0%. Moreover, the CCL circuit can also accelerate the PLL recovery procedure from loss of lock due to phase or frequency shift, as well as a single-event strike.

  4. Design of improved CMOS phase-frequency detector and charge-pump for phase-locked loop

    International Nuclear Information System (INIS)

    Two essential blocks for the PLLs based on CP, a phase-frequency detector (PFD) and an improved current steering charge-pump (CP), are developed. The mechanisms for widening the phase error detection range and eliminating the dead zone are analyzed and applied in our design to optimize the proposed PFD. To obtain excellent current matching and minimum current variation over a wide output voltage range, an improved structure for the proposed CP is developed by fully utilizing many additional sub-circuits. Implemented in a standard 90-nm CMOS process, the proposed PFD achieves a phase error detection range from −354° to 354° and the improved CP demonstrates a current mismatch of less than 1.1% and a pump-current variation of 4% across the output voltage, swinging from 0.2 to 1.1 V, and the power consumption is 1.3 mW under a 1.2-V supply. (semiconductor integrated circuits)

  5. Lego clocks : building a clock from parts

    NARCIS (Netherlands)

    Brunner, Michael; Simons, Mirre J. P.; Merrow, Martha

    2008-01-01

    A new finding opens up speculation that the molecular mechanism of circadian clocks in Synechococcus elongatus is composed of multiple oscillator systems (Kitayama and colleagues, this issue, pp. 1513-1521), as has been described in many eukaryotic clock model systems. However, an alternative intepr

  6. Oil Coking Prevention Using Electric Water Pump for Turbo-Charge Spark-Ignition Engines

    Directory of Open Access Journals (Sweden)

    Han-Ching Lin

    2014-01-01

    Full Text Available Turbocharger has been widely implemented for internal combustion engine to increase an engine's power output and reduce fuel consumption. However, its operating temperature would rise to 340°C when engine stalls. This higher temperature may results in bearing wear, run-out, and stick, due to oil coking and insufficient lubrication. In order to overcome these problems, this paper employs Electric Water Pump (EWP to supply cool liquid to turbocharger actively when the engine stalls. The system layout, operating timing, and duration of EWP are investigated for obtaining optimal performance. The primarily experimental results show that the proposed layout and control strategy have a lower temperature of 100°C than the conventional temperature 225°C.

  7. High Performance Charge Pump Phase-Locked Loop with Low Current Mismatch

    Directory of Open Access Journals (Sweden)

    V. Sujatha

    2012-01-01

    Full Text Available In CMOS CPs, which have Up and Down switches made of p-channel and n-channel respectively, generates fluctuations in the VCO due to current mismatch occurs when dumping the charge to the loop filter and subsequently a large phase noise on the PLL output. This paper presents a new CP circuit after detailed analysis of the current mismatch problem. It combines an error amplifier with reference current sources to achieve good current matching characteristics and lower phase noises. Charge sharing can be eliminated by using charge removal transistors. In addition, a low-voltage cascode current mirror and gain-boosting circuit are used to enhance current matching over process corners and increase the output impedance of the CP. Good current matching characteristic is achieved with less than 0.1% difference of the Up/Down current and 1% over all process variations. The CP output compliance voltage range of 0.1-1.8 V is achieved for 1.8-V supply voltage. The circuit was designed using 0.18um TSMC CMOS technology and simulated by Spectre tools.

  8. A charge-pump 60kV modulator for the ISOLDE target extraction voltage

    CERN Document Server

    Barlow, R A; Fowler, A; Gaudillet, H; Gharsa, T; Schipper, J

    2015-01-01

    The ISOLDE facility at CERN provides radioactive ion beams to a number of experimental stations. These ions are produced by a metal target, floating at 60 kV, which is impacted by a 1.4 GeV high intensity proton beam. The ions are then accelerated by a grounded extraction electrode to 60 keV, before transport to the experimental area. During proton beam impact extremely high ionisation of the volume around the target gives rise to significant leakage current which results in loss of charge on the effective target capacitance of approximately 6 nF. If short life-time isotopes are to be studied, the 60 kV must be re-established within a maximum of 10 ms. Recharging the target capacitance to 60 kV and to the required stability of better than 10-4 precludes a direct charging system and an alternative method of re-establishing the 60 kV is used. The present system [1], in operation since 1991, employs a resonant circuit which is triggered 35 µs prior to beam impact. This circuit transfers the charge on the effec...

  9. Optical Clocks in Space

    CERN Document Server

    Schiller, S; Nevsky, A; Koelemeij, J C J; Wicht, A; Gill, P; Klein, H A; Margolis, H S; Mileti, G; Sterr, U; Riehle, F; Peik, E; Tamm, C; Ertmer, W; Rasel, E; Klein, V; Salomon, C; Tino, G M; Lemonde, P; Holzwarth, R; Hänsch, T W; Tamm, Chr.

    2007-01-01

    The performance of optical clocks has strongly progressed in recent years, and accuracies and instabilities of 1 part in 10^18 are expected in the near future. The operation of optical clocks in space provides new scientific and technological opportunities. In particular, an earth-orbiting satellite containing an ensemble of optical clocks would allow a precision measurement of the gravitational redshift, navigation with improved precision, mapping of the earth's gravitational potential by relativistic geodesy, and comparisons between ground clocks.

  10. A clock generator for a high-speed high-resolution pipelined A/D converter

    Institute of Scientific and Technical Information of China (English)

    Zhao Lei; Yang Yintang; Zhu Zhangming; Liu Lianxi

    2013-01-01

    A clock generator circuit for a high-speed high-resolution pipelined A/D converter is presented.The circuit is realized by a delay locked loop (DLL),and a new differential structure is used to improve the precision of the charge pump.Meanwhile,a dynamic logic phase detector and a three transistor NAND logic circuit are proposed to reduce the output jitter by improving the steepness of the clock transition.The proposed circuit,designed by SMIC 0.18 μm 3.3 V CMOS technology,is used as a clock generator for a 14 bit 100 MS/s pipelined ADC.The simulation results have shown that the duty cycle ranged from 10% to 90% and can be adjusted.The average duty cycle error is less than 1%.The lock-time is only 13 clock cycles.The active area is 0.05 mm2 and power consumption is less than 15 mW.

  11. A clock generator for a high-speed high-resolution pipelined A/D converter

    International Nuclear Information System (INIS)

    A clock generator circuit for a high-speed high-resolution pipelined A/D converter is presented. The circuit is realized by a delay locked loop (DLL), and a new differential structure is used to improve the precision of the charge pump. Meanwhile, a dynamic logic phase detector and a three transistor NAND logic circuit are proposed to reduce the output jitter by improving the steepness of the clock transition. The proposed circuit, designed by SMIC 0.18 μm 3.3 V CMOS technology, is used as a clock generator for a 14 bit 100 MS/s pipelined ADC. The simulation results have shown that the duty cycle ranged from 10% to 90% and can be adjusted. The average duty cycle error is less than 1%. The lock-time is only 13 clock cycles. The active area is 0.05 mm2 and power consumption is less than 15 mW. (semiconductor integrated circuits)

  12. The Glyoxal Clock Reaction

    Science.gov (United States)

    Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

    2007-01-01

    Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

  13. A low jitter PLL clock used for phase change memory

    Institute of Scientific and Technical Information of China (English)

    Hong Xiao; Chen Houpeng; Song Zhitang; Cai Daolin; Li Xi

    2013-01-01

    A fully integrated low-jitter,precise frequency CMOS phase-locked loop (PLL) clock for the phase change memory (PCM) drive circuit is presented.The design consists of a dynamic dual-reset phase frequency detector (PFD) with high frequency acquisition,a novel low jitter charge pump,a CMOS ring oscillator based voltage-controlled oscillator (VCO),a 2nd order passive loop filter,and a digital frequency divider.The design is fabricated in 0.35μm CMOS technology and consumes 20 mW from a supply voltage of 5 V.In terms of the PCM's program operation requirement,the output frequency range is from 1 to 140 MHz.For the 140 MHz output frequency,the circuit features a cycle-to-cycle jitter of 28 ps RMS and 250 ps peak-to-peak.

  14. Are extracellular osmolality and sodium concentration determined by Donnan effects of intracellular protein charges and of pumped sodium?

    Science.gov (United States)

    Kurbel, Sven

    2008-06-21

    Although we are used to attribute almost identical extracellular fluid (ECF) sodium concentrations in birds, amphibians, reptiles, and mammals to the composition of the primordial oceans in which, presumably, all life originated, this interpretation is not supported by geological data suggesting that the ocean salinity was never much lower than the present-day values, still four times higher than our plasma sodium. Here presented interpretation is that the similar ECF salt concentrations are dictated by the opposed Donnan effects on the cell membrane. The only way for the cell to reach the osmotic equilibrium is to alter cell volume, until concentration of nondiffusible intracellular ions (mainly charges on intracellular proteins) is equal to the ECF restricted ions (mainly Na+ ions, restricted by pumping out of cells). The achievement of electroneutrality requires that the sum of all anions equals concentration of positive ions in the cell (mainly K+). Negative charges on cytoplasmic proteins are the most stable component among ionized particles and other ions have to adapt to their concentration. Positive and negative soluble intracellular ions are all osmotically active and to achieve balance of osmotic forces on the cell membrane, the sum of their intracellular concentrations must equal the concentration of osmotically active extracellular particles. Since almost half the osmotically active ECF particles are sodium ions, the ECF sodium concentration seems related to concentration of charges on cytoplasmic proteins and concentration of intracellular phosphates. Our ancestors could not leave the salty ocean and move to brackish, or even fresh waters, without adequate regulation of their ECF sodium concentration and osmolality. Concentration of charges on cytoplasmic proteins or of intracellular phosphate buffers could not be altered, since this would compromise cell functioning. The remaining solution was to maintain the lowest ECF Na+ concentration effective in

  15. Optical lattice clock with Strontium atoms

    International Nuclear Information System (INIS)

    This thesis presents the latest achievements regarding the optical lattice clock with Strontium atoms developed at LNE-SYRTE. After a review of the different types of optical clocks that are currently under development, we stress on the concept of optical lattice clock which was first imagined for Sr87 using the 1S0 → 3P0 transition. We exhibit the features of this atom, in particular the concept of magic wavelength for the trap, and the achievable performances for this kind of clock. The second part presents the experimental aspects, insisting particularly on the ultra-stable laser used for the interrogation of the atoms which is a central part of the experiment. Among the latest improvements, an optical pumping phase and an interrogation phase using a magnetic field have been added in order to refine the evaluation of the Zeeman effect. Finally, the last part presents the experimental results. The last evaluation of the clock using Sr87 atoms allowed us to reach a frequency accuracy of 2.6*10-15 and a measurement in agreement with the one made at JILA (Tokyo university) at the 10-15 level. On another hand, thanks to recent theoretical proposals, we made a measurement using the bosonic isotope Sr88 by adapting the experimental setup. This measurement represents the first evaluation for this type of clock, with a frequency accuracy of 7*10-14. (author)

  16. 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....

  17. 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....

  18. Programmable Clock Waveform Generation for CCD Readout

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Castilla, J.; Martinez, G.; Marin, J.

    2006-07-01

    Charge transfer efficiency in CCDs is closely related to the clock waveform. In this paper, an experimental framework to explore different FPGA based clock waveform generator designs is described. Two alternative design approaches for controlling the rise/fall edge times and pulse width of the CCD clock signal have been implemented: level-control and time-control. Both approaches provide similar characteristics regarding the edge linearity and noise. Nevertheless, dissimilarities have been found with respect to the area and frequency range of application. Thus, while the time-control approach consumes less area, the level control approach provides a wider range of clock frequencies since it does not suffer capacitor discharge effect. (Author) 8 refs.

  19. Field-induced Gap and Quantized Charge Pumping in Nano-helix

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Xiao-Liang; /Stanford U., Phys. Dept. /Tsinghua U., Beijing; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-02-15

    We propose several novel physical phenomena based on nano-scale helical wires. Applying a static electric field transverse to the helical wire induces a metal to insulator transition, with the band gap determined by the applied voltage. Similar idea can be applied to 'geometrically' constructing one-dimensional systems with arbitrary external potential. With a quadrupolar electrode configuration, the electric field could rotate in the transverse plane, leading to a quantized dc charge current proportional to the frequency of the rotation. Such a device could be used as a new standard for the high precession measurement of the electric current. The inverse effect implies that passing an electric current through a helical wire in the presence of a transverse static electric field can lead to a mechanical rotation of the helix. This effect can be used to construct nano-scale electro-mechanical motors. Finally, our methodology also enables new ways of controlling and measuring the electronic properties of helical biological molecules such as the DNA.

  20. A double-stage start-up structure to limit the inrush current used in current mode charge pump

    Science.gov (United States)

    Cong, Liu; Xinquan, Lai; Hanxiao, Du; Yuan, Chi

    2016-06-01

    A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range, fixed output and multimode operation is presented in this paper. As a widely utilized power source implement, a Li-battery is always used as the power supply for chips. Due to the internal resistance, a potential drop will be generated at the input terminal of the chip with an input current. A false shut down with a low supply voltage will happen if the input current is too large, leading to the degradation of the Li-battery's service life. To solve this problem, the inrush current is limited by introducing a new start-up state. All of the circuits have been implemented with the NUVOTON 0.6 μm CMOS process. The measurement results show that the inrush current can be limited below 1 A within all input supply ranges, and the power efficiency is higher than the conventional structure. Project supported by the National Natural Science Foundation of China (No. 61106026).

  1. Precision Clock Evaluation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Tests and evaluates high-precision atomic clocks for spacecraft, ground, and mobile applications. Supports performance evaluation, environmental testing,...

  2. The charge pump PLL clock generator designed for the 1.56 ns bin size time-to-digital converter pixel array of the Timepix3 readout ASIC

    CERN Document Server

    Fu, Y et al.

    2014-01-01

    Timepix3 is a newly developed pixel readout chip which is expected to be operated in a wide range of gaseous and silicon detectors. It is made of 256×256 pixels organized in a square pixel-array with 55 µm pitch. Oscillators running at 640 MHz are distributed across the pixel-array and allow for a highly accurate measurement of the arrival time of a hit. This paper concentrates on a low-jitter phase locked loop (PLL) that is located in the chip periphery. This PLL provides a control voltage which regulates the actual frequency of the individual oscillators, allowing for compensation of process, voltage, and temperature variations.

  3. The quantum beat principles and applications of atomic clocks

    CERN Document Server

    Major, F

    2007-01-01

    This work attempts to convey a broad understanding of the physical principles underlying the workings of these quantum-based atomic clocks, with introductory chapters placing them in context with the early development of mechanical clocks and the introduction of electronic time-keeping as embodied in the quartz-controlled clocks. While the book makes no pretense at being a history of atomic clocks, it nevertheless takes a historical perspective in its treatment of the subject. Intended for nonspecialists with some knowledge of physics or engineering, The Quantum Beat covers a wide range of salient topics relevant to atomic clocks, treated in a broad intuitive manner with a minimum of mathematical formalism. Detailed descriptions are given of the design principles of the rubidium, cesium, hydrogen maser, and mercury ion standards; the revolutionary changes that the advent of the laser has made possible, such as laser cooling, optical pumping, the formation of "optical molasses," and the cesium "fountain" stand...

  4. Biological Clocks & Circadian Rhythms

    Science.gov (United States)

    Robertson, Laura; Jones, M. Gail

    2009-01-01

    The study of biological clocks and circadian rhythms is an excellent way to address the inquiry strand in the National Science Education Standards (NSES) (NRC 1996). Students can study these everyday phenomena by designing experiments, gathering and analyzing data, and generating new experiments. As students explore biological clocks and circadian…

  5. Design of Alarm Clock

    OpenAIRE

    Budík, Marek

    2015-01-01

    The goal of this thesis is to create alarm clock, which respect the functional, technical and aesthetic requirements of this device and attain an attractive design of this product. The final draft should be innovative, original and user attractive alarm clock.

  6. Active optical clock

    Institute of Scientific and Technical Information of China (English)

    CHEN JingBiao

    2009-01-01

    This article presents the principles and techniques of active optical clock, a special laser combining the laser physics of one-atom laser, bad-cavity gas laser, super-cavity stabilized laser and optical atomic clock together. As a simple example, an active optical clock based on thermal strontium atomic beam shows a quantum-limited linewidth of 0.51 Hz, which is insensitive to laser cavity-length noise, and may surpass the recorded narrowest 6.7 Hz of Hg ion optical clock and 1.5 Hz of very recent optical lattice clock. The estimated 0.1 Hz one-second instability and 0.27 Hz uncertainty are limited only by the rela-tivistic Doppler effect, and can be improved by cold atoms.

  7. On-chip clock error characterization for clock distribution system

    OpenAIRE

    Shan, Chuan; Galayko, Dimitri; Anceau, François

    2013-01-01

    In this paper, we investigate a test strategy for characterization of clock error statistics between two clock domains in high-speed clocking systems (gigahertz and more). The method allows an indirect measurement (not based on time interval measurement) of clock error distribution by observing the integrity of a periodic sequence transmitted between two clocking domains. The method is compatible with fully on-chip implementation, and the readout of result to off-chip signals is cadenced at l...

  8. Stable clocks and general relativity

    CERN Document Server

    Will, C M

    1995-01-01

    We survey the role of stable clocks in general relativity. Clock comparisons have provided important tests of the Einstein Equivalence Principle, which underlies metric gravity. These include tests of the isotropy of clock comparisons (verification of local Lorentz invariance) and tests of the homogeneity of clock comparisons (verification of local position invariance). Comparisons of atomic clocks with gravitational clocks test the Strong Equivalence Principle by bounding cosmological variations in Newton's constant. Stable clocks also play a role in the search for gravitational radiation: comparision of atomic clocks with the binary pulsar's orbital clock has verified gravitational-wave damping, and phase-sensitive detection of waves from inspiralling compact binaries using laser interferometric gravitational observatories will facilitate extraction of useful source information from the data. Stable clocks together with general relativity have found important practical applications in navigational systems s...

  9. Compact, Highly Stable Ion Atomic Clock

    Science.gov (United States)

    Prestage, John

    2008-01-01

    A mercury-ion clock now at the breadboard stage of development (see figure) has a stability comparable to that of a hydrogen-maser clock: In tests, the clock exhibited an Allan deviation of between 2 x 10(exp -13) and 3 x 10(exp -13) at a measurement time of 1 second, averaging to about 10(exp -15) at 1 day. However, the clock occupies a volume of only about 2 liters . about a hundredth of the volume of a hydrogen-maser clock. The ion-handling parts of the apparatus are housed in a sealed vacuum tube, wherein only a getter pump is used to maintain the vacuum. Hence, this apparatus is a prototype of a generation of small, potentially portable high-precision clocks for diverse ground- and space-based navigation and radio science applications. Furthermore, this new ion-clock technology is about 100 times more stable and precise than the rubidium atomic clocks currently in use in the NAV STAR GPS Earth-orbiting satellites. In this clock, mercury ions are shuttled between a quadrupole and a 16-pole linear radio-frequency trap. In the quadrupole trap, the ions are tightly confined and optical state selection from a Hg-202 radio-frequency-discharge ultraviolet lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions resonant at frequency of about 40.507 GHz are interrogated by use of a microwave beam at that frequency. The trapping of ions effectively eliminates the frequency pulling caused by wall collisions inherent to gas-cell clocks. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave- resonance process, so that each of these processes can be optimized independently of the other. The basic ion-shuttling, two-trap scheme as described thus far is not new: it has been the basis of designs of prior larger clocks. The novelty of the present development lies in major redesigns of its physics package (the ion traps and the vacuum and optical subsystems) to effect

  10. Charge pump design in 130 nm SiGe BiCMOS technology for low-noise fractional-N PLLs

    OpenAIRE

    M. Kucharski; Herzel, F.

    2015-01-01

    This paper presents a numerical comparison of charge pumps (CP) designed for a high linearity and a low noise to be used in a fractional-N phase-locked loop (PLL). We consider a PLL architecture, where two parallel CPs with DC offset are used. The CP for VCO fine tuning is biased at the output to keep the VCO gain constant. For this specific architecture, only one transistor per CP is relevant for phase detector linearity. This can be an nMOSFET, a pMOSFET or a SiGe HBT, dep...

  11. Two-photon assisted clock comparison to picosecond precision

    CERN Document Server

    Zhang, Shi-Wei; Yao, Yin-Ping; Wan, Ren-Gang; Zhang, Tong-Yi

    2015-01-01

    We have experimentally demonstrated a clock comparison scheme utilizing time-correlated photon pairs generated from the spontaneous parametric down conversion process of a laser pumped beta-barium borate crystal. The coincidence of two-photon events are analyzed by the cross correlation of the two time stamp sequences. Combining the coarse and fine part of the time differences at different resolutions, a 64 ps precision for clock synchronization has been realized. We also investigate the effects of hardware devices used in the system on the precision of clock comparison. The results indicate that the detector's time jitter and the background noise will degrade the system performance. With this method, comparison and synchronization of two remote clocks could be implemented with a precision at the level of a few tens of picoseconds.

  12. On clocks and clouds

    Directory of Open Access Journals (Sweden)

    M. K. Witte

    2013-09-01

    Full Text Available Cumulus clouds exhibit a life cycle that consists of: (a the growth phase (increasing size, most notably in the vertical direction; (b the mature phase (growth ceases; any precipitation that develops is strongest during this period; and (c the dissipation phase (cloud dissipates because of precipitation and/or entrainment; no more dynamical support. Although radar can track clouds over time and give some sense of the age of a cloud, most aircraft in situ measurements lack temporal context. We use large eddy simulations of trade wind cumulus cloud fields from cases during the Barbados Oceanographic and Meteorological Experiment (BOMEX and Rain In Cumulus over the Ocean (RICO campaigns to demonstrate a potential cumulus cloud "clock". We find that the volume-averaged total water mixing ratio rt is a useful cloud clock for the 12 clouds studied. A cloud's initial rt is set by the subcloud mixed-layer mean rt and decreases monotonically from the initial value due primarily to entrainment. The clock is insensitive to aerosol loading, environmental sounding and extrinsic cloud properties such as lifetime and volume. In some cases (more commonly for larger clouds, multiple pulses of buoyancy occur, which complicate the cumulus clock by replenishing rt. The clock is most effectively used to classify clouds by life phase.

  13. Low-power, miniature 171Yb ion clock using an ultra-small vacuum package

    International Nuclear Information System (INIS)

    We report a demonstration of a very small microwave atomic clock using the 12.6 GHz hyperfine transition of the trapped 171Yb ions inside a miniature, completely sealed-off 3 cm3 ion-trap vacuum package. In the ion clock system, all of the components are highly miniaturized with low power consumption except the 369 nm optical pumping laser still under development for miniaturization. The entire clock, including the control electronics, consumes + clock reaches the 10−14 range after a few days of integration.

  14. Optical atomic clocks

    International Nuclear Information System (INIS)

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today’s best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  15. Optical atomic clocks

    CERN Document Server

    Poli, N; Gill, P; Tino, G M

    2014-01-01

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femto-second optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in $10^{18}$. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  16. Optical atomic clocks

    Science.gov (United States)

    Poli, N.; Oates, C. W.; Gill, P.; Tino, G. M.

    2013-12-01

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  17. The circadian clock goes genomic

    OpenAIRE

    Staiger, D; Shin, J; Johansson, M; Davis, S

    2013-01-01

    Large-scale biology among plant species, as well as comparative genomics of circadian clock architecture and clock-regulated output processes, have greatly advanced our understanding of the endogenous timing system in plants.

  18. Decamp Clock Board Firmware

    International Nuclear Information System (INIS)

    Decamp (Dark Energy Survey Camera) is a new instrument designed to explore the universe aiming to reveal the nature of Dark Energy. The camera consists of 72 CCDs and 520 Mpixels. The readout electronics of DECam is based on the Monsoon system. Monsoon is a new image acquisition system developed by the NOAO (National Optical Astronomical Observatory) for the new generation of astronomical cameras. The Monsoon system uses three types of boards inserted in a Eurocard format based crate: master control board, acquisition board and clock board. The direct use of the Monsoon system for DECam readout electronics requires nine crates mainly due to the high number of clock boards needed. Unfortunately, the available space for DECam electronics is constrained to four crates at maximum. The major drawback to achieve such desired compaction degree resides in the clock board signal density. This document describes the changes performed at CIEMAT on the programmable logic of the Monsoon clock board aiming to meet such restricted space constraints. (Author) 5 refs

  19. Clock Reaction: Outreach Attraction

    Science.gov (United States)

    Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

    2010-01-01

    Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

  20. Decamp Clock Board Firmware

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Castilla, J.; Martinez, G.

    2007-09-27

    Decamp (Dark Energy Survey Camera) is a new instrument designed to explore the universe aiming to reveal the nature of Dark Energy. The camera consists of 72 CCDs and 520 Mpixels. The readout electronics of DECam is based on the Monsoon system. Monsoon is a new image acquisition system developed by the NOAO (National Optical Astronomical Observatory) for the new generation of astronomical cameras. The Monsoon system uses three types of boards inserted in a Eurocard format based crate: master control board, acquisition board and clock board. The direct use of the Monsoon system for DECam readout electronics requires nine crates mainly due to the high number of clock boards needed. Unfortunately, the available space for DECam electronics is constrained to four crates at maximum. The major drawback to achieve such desired compaction degree resides in the clock board signal density. This document describes the changes performed at CIEMAT on the programmable logic of the Monsoon clock board aiming to meet such restricted space constraints. (Author) 5 refs.

  1. Progress Toward a Compact, Highly Stable Ion Clock

    Science.gov (United States)

    Prestage, John; Chung, Sang

    2009-01-01

    There was an update on the subject of two previous NASA Tech Briefs articles: Compact, Highly Stable Ion Clock (NPO-43075), Vol. 32, No. 5 (May 2008), page 63; and Neon as a Buffer Gas for a Mercury-Ion Clock (NPO-42919), Vol. 32, No. 7 (July 2008), page 62. To recapitulate: A developmental miniature mercury-ion clock has stability comparable to that of a hydrogen-maser clock. The ion-handling components are housed in a sealed vacuum tube, wherein a getter pump maintains the partial vacuum, and the evacuated tube is backfilled with mercury vapor in a neon buffer gas. There was progress in the development of the clock, with emphasis on the design, fabrication, pump-down, and bake-out of the vacuum tube (based on established practice in the travelingwave- tube-amplifier industry) and the ability of the tube to retain a vacuum after a year of operation. Other developments include some aspects of the operation of mercury-vapor source (a small appendage oven containing HgO) so as to maintain the optimum low concentration of mercury vapor, and further efforts to miniaturize the vacuum and optical subsystems to fit within a volume of 2 L.

  2. Frequency ratios of Sr, Yb and Hg based optical lattice clocks and their applications

    CERN Document Server

    Takamoto, Masao; Das, Manoj; Nemitz, Nils; Ohkubo, Takuya; Yamanaka, Kazuhiro; Ohmae, Noriaki; Takano, Tetsushi; Akatsuka, Tomoya; Yamaguchi, Atsushi; Katori, Hidetoshi

    2015-01-01

    This article describes the recent progress of optical lattice clocks with neutral strontium ($^{87}$Sr), ytterbium ($^{171}$Yb) and mercury ($^{199}$Hg) atoms. In particular, we present frequency comparison between the clocks locally via an optical frequency comb and between two Sr clocks at remote sites using a phase-stabilized fibre link. We first review cryogenic Sr optical lattice clocks that reduce the room-temperature blackbody radiation shift by two orders of magnitude and serve as a reference in the following clock comparisons. Similar physical properties of Sr and Yb atoms, such as transition wavelengths and vapour pressure, have allowed our development of a compatible clock for both species. A cryogenic Yb clock is evaluated by referencing a Sr clock. We also report on a Hg clock, which shows one order of magnitude less sensitivity to blackbody radiation, while its large nuclear charge makes the clock sensitive to the variation of fine-structure constant. Connecting all three types of clocks by an o...

  3. Laser-pump/X-ray-probe experiments with electrons ejected from a Cu(111) target: space-charge acceleration.

    Science.gov (United States)

    Schiwietz, G; Kühn, D; Föhlisch, A; Holldack, K; Kachel, T; Pontius, N

    2016-09-01

    A comprehensive investigation of the emission characteristics for electrons induced by X-rays of a few hundred eV at grazing-incidence angles on an atomically clean Cu(111) sample during laser excitation is presented. Electron energy spectra due to intense infrared laser irradiation are investigated at the BESSY II slicing facility. Furthermore, the influence of the corresponding high degree of target excitation (high peak current of photoemission) on the properties of Auger and photoelectrons liberated by a probe X-ray beam is investigated in time-resolved pump and probe measurements. Strong electron energy shifts have been found and assigned to space-charge acceleration. The variation of the shift with laser power and electron energy is investigated and discussed on the basis of experimental as well as new theoretical results. PMID:27577771

  4. Adiabatic pumping through quantum dots

    International Nuclear Information System (INIS)

    A finite charge can be pumped through a mesoscopic system in the absence of an applied bias voltage by changing periodically in time some parameters of the system. If these parameters change slowly with respect to all internal time scales of the system, pumping is adiabatic. The scope of this work is to investigate adiabatic pumping through a quantum dot, in particular the influence of Coulomb interaction between electrons in the dot on the pumped charge. On one hand we develop a formalism based on Green's functions, in order to calculate the pumped charge from the weak-tunnel-coupling regime down to the Kondo regime. We extend our calculations to a system with a superconducting contact. On the other hand we use a systematic perturbation expansion for the calculation of the pumped charge, giving us the possibility to analyze processes which contribute to charge pumping and to highlight the important role of interaction-induced level renormalization. (orig.)

  5. Conveyor belt clock synchronization

    CERN Document Server

    Giovannetti, V; Maccone, L; Shapiro, J H; Wong, F N C; Giovannetti, Vittorio; Lloyd, Seth; Maccone, Lorenzo; Shapiro, Jeffrey H.; Wong, Franco N. C.

    2004-01-01

    A protocol for synchronizing distant clocks is proposed that does not rely on the arrival times of the signals which are exchanged, and an optical implementation based on coherent-state pulses is described. This protocol is not limited by any dispersion that may be present in the propagation medium through which the light signals are exchanged. Possible improvements deriving from the use of quantum-mechanical effects are also addressed.

  6. Synchronization of clocks

    International Nuclear Information System (INIS)

    In this report we recall the famous Huygens’ experiment which gave the first evidence of the synchronization phenomenon. We consider the synchronization of two clocks which are accurate (show the same time) but have pendula with different masses. It has been shown that such clocks hanging on the same beam can show the almost complete (in-phase) and almost antiphase synchronizations. By almost complete and almost antiphase synchronization we defined the periodic motion of the pendula in which the phase shift between the displacements of the pendula is respectively close (but not equal) to 0 or π. We give evidence that almost antiphase synchronization was the phenomenon observed by Huygens in XVII century. We support our numerical studies by considering the energy balance in the system and showing how the energy is transferred between the pendula via oscillating beam allowing the pendula’s synchronization. Additionally we discuss the synchronization of a number of different pendulum clocks hanging from a horizontal beam which can roll on the parallel surface. It has been shown that after a transient, different types of synchronization between pendula can be observed; (i) the complete synchronization in which all pendula behave identically, (ii) pendula create three or five clusters of synchronized pendula. We derive the equations for the estimation of the phase differences between phase synchronized clusters. The evidence, why other configurations with a different number of clusters are not observed, is given.

  7. Prediction of GNSS satellite clocks

    International Nuclear Information System (INIS)

    This thesis deals with the characterisation and prediction of GNSS-satellite-clocks. A prerequisite to develop powerful algorithms for the prediction of clock-corrections is the thorough study of the behaviour of the different clock-types of the satellites. In this context the predicted part of the IGU-clock-corrections provided by the Analysis Centers (ACs) of the IGS was compared to the IGS-Rapid-clock solutions to determine reasonable estimates of the quality of already existing well performing predictions. For the shortest investigated interval (three hours) all ACs obtain almost the same accuracy of 0,1 to 0,4 ns. For longer intervals the individual predictions results start to diverge. Thus, for a 12-hours- interval the differences range from nearly 10 ns (GFZ, CODE) until up to some 'tens of ns'. Based on the estimated clock corrections provided via the IGS Rapid products a simple quadratic polynomial turns out to be sufficient to describe the time series of Rubidium-clocks. On the other hand Cesium-clocks show a periodical behaviour (revolution period) with an amplitude of up to 6 ns. A clear correlation between these amplitudes and the Sun elevation angle above the orbital planes can be demonstrated. The variability of the amplitudes is supposed to be caused by temperature-variations affecting the oscillator. To account for this periodical behaviour a quadratic polynomial with an additional sinus-term was finally chosen as prediction model both for the Cesium as well as for the Rubidium clocks. The three polynomial-parameters as well as amplitude and phase shift of the periodic term are estimated within a least-square-adjustment by means of program GNSS-VC/static. Input-data are time series of the observed part of the IGU clock corrections. With the estimated parameters clock-corrections are predicted for various durations. The mean error of the prediction of Rubidium-clock-corrections for an interval of six hours reaches up to 1,5 ns. For the 12-hours

  8. Microchip-Based Trapped-Atom Clocks

    OpenAIRE

    Vuletic, Vladan; Leroux, Ian D.; Schleier-Smith, Monika H.

    2011-01-01

    This is a chapter of a recently published book entitled Atom Chips, edited by Jakob Reichel and Vladan Vuletic. The contents of this chapter include: Basic Principles; Atomic-Fountain versus Trapped-Atom Clocks; Optical-Transition Clocks versus Microwave Clocks; Clocks with Magnetically Trapped Atoms--Fundamental Limits and Experimental Demonstrations; Readout in Trapped-Atom Clocks; and Spin Squeezing.

  9. Geometrical pumping with a Bose-Einstein condensate

    OpenAIRE

    Lu, Hsin-I; Schemmer, Max; Aycock, Lauren M.; Genkina, Dina; Sugawa, Seiji; Spielman, Ian B.

    2015-01-01

    We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global -- topological -- properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits non-quantized charge pumping set by local -- geometrical -- properties of the band structure. Like topological charge p...

  10. Optical atomic clocks and metrology

    Science.gov (United States)

    Ludlow, Andrew

    2014-05-01

    The atomic clock has long demonstrated the capability to measure time or frequency with very high precision. Consequently, these clocks are used extensively in technological applications such as advanced synchronization or communication and navigation networks. Optical atomic clocks are next- generation timekeepers which reference narrowband optical transitions between suitable atomic states. Many optical time/frequency standards utilize state-of-the-art quantum control and precision measurement. Combined with the ultrahigh quality factors of the atomic resonances at their heart, optical atomic clocks have promised new levels of timekeeping precision, orders of magnitude higher than conventional atomic clocks based on microwave transitions. Such measurement capability enables and/or enhances many of the most exciting applications of these clocks, including the study of fundamental laws of physics through the measurement of time evolution. Here, I will highlight optical atomic clocks and their utility, as well as review recent advances in their development and performance. In particular, I will describe in detail the optical lattice clock and the realization of frequency measurement at the level of one part in 1018. To push the performance of these atomic timekeepers to such a level and beyond, several key advances are being explored worldwide. These will be discussed generally, with particular emphasis on our recent efforts at NIST in developing the optical lattice clock based on atomic ytterbium.

  11. A Light Clock Satisfying the Clock Hypothesis of Special Relativity

    Science.gov (United States)

    West, Joseph

    2007-01-01

    The design of the FMEL, a floor-mirrored Einstein-Langevin "light clock", is introduced. The clock provides a physically intuitive manner to calculate and visualize the time dilation effects for a spatially extended set of observers (an accelerated "frame") undergoing unidirectional acceleration or observers on a rotating cylinder of constant…

  12. Highly-charged ions as a basis of optical atomic clockwork of exceptional accuracy

    OpenAIRE

    Derevianko, Andrei; Dzuba, V. A.; Flambaum, V. V.

    2012-01-01

    We propose a novel class of atomic clocks based on highly charged ions. We consider highly-forbidden laser-accessible transitions within the $4f^{12}$ ground-state configurations of highly charged ions. Our evaluation of systematic effects demonstrates that these transitions may be used for building exceptionally accurate atomic clocks which may compete in accuracy with recently proposed nuclear clock.

  13. Simulating Future GPS Clock Scenarios with Two Composite Clock Algorithms

    Science.gov (United States)

    Suess, Matthias; Matsakis, Demetrios; Greenhall, Charles A.

    2010-01-01

    Using the GPS Toolkit, the GPS constellation is simulated using 31 satellites (SV) and a ground network of 17 monitor stations (MS). At every 15-minutes measurement epoch, the monitor stations measure the time signals of all satellites above a parameterized elevation angle. Once a day, the satellite clock estimates the station and satellite clocks. The first composite clock (B) is based on the Brown algorithm, and is now used by GPS. The second one (G) is based on the Greenhall algorithm. The composite clock of G and B performance are investigated using three ground-clock models. Model C simulates the current GPS configuration, in which all stations are equipped with cesium clocks, except for masers at USNO and Alternate Master Clock (AMC) sites. Model M is an improved situation in which every station is equipped with active hydrogen masers. Finally, Models F and O are future scenarios in which the USNO and AMC stations are equipped with fountain clocks instead of masers. Model F is a rubidium fountain, while Model O is more precise but futuristic Optical Fountain. Each model is evaluated using three performance metrics. The timing-related user range error having all satellites available is the first performance index (PI1). The second performance index (PI2) relates to the stability of the broadcast GPS system time itself. The third performance index (PI3) evaluates the stability of the time scales computed by the two composite clocks. A distinction is made between the "Signal-in-Space" accuracy and that available through a GNSS receiver.

  14. Geometrical Pumping with a Bose-Einstein Condensate

    Science.gov (United States)

    Lu, H.-I.; Schemmer, M.; Aycock, L. M.; Genkina, D.; Sugawa, S.; Spielman, I. B.

    2016-05-01

    We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global—topological—properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits nonquantized charge pumping set by local—geometrical—properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wave packet's position in each unit cell, i.e., the polarization.

  15. An alternative derivation of the gravitomagnetic clock effect

    International Nuclear Information System (INIS)

    The possibility of detecting the gravitomagnetic clock effect using artificial Earth satellites provides the incentive to develop a more intuitive approach to its derivation. We first consider two test electric charges moving on the same circular orbit but in opposite directions in orthogonal electric and magnetic fields and show that the particles take different times in describing a full orbit. The expression for the time difference is completely analogous to that of the general relativistic gravitomagnetic clock effect in the weak-field and slow-motion approximation. The latter is obtained by considering the gravitomagnetic force as a small classical non-central perturbation of the main central Newtonian monopole force. A general expression for the clock effect is given for a spherical orbit with an arbitrary inclination angle. This formula differs from the result of the general relativistic calculations by terms of order c-4

  16. Jitter impact on clock distribution in LHC experiments

    International Nuclear Information System (INIS)

    The LHC Bunch Clock is one of the most important accelerator signals delivered to the experiments. Being directly derived from the Radio Frequency driving the beams in the accelerator by a simple division of its frequency by a factor of 10, the Bunch Clock signal represents the frequency at which the bunches are crossing each other at each experiment. It is thus used to synchronize all the electronics systems in charge of event detection. Its frequency is around 40.079 MHz, but varies with beam parameters (energy, particle type, etc) by a few hundreds of Hz. The present paper discusses the quality of this Bunch Clock signal in terms of jitter. It is in particular compared to typical requirements of electronic components of the LHC detectors and put in perspective with the intrinsic jitter of the beam itself, to which this signal is related.

  17. Mapping Out Atom-Wall Interaction with Atomic Clocks

    International Nuclear Information System (INIS)

    We explore the feasibility of probing atom-wall interaction with atomic clocks based on atoms trapped in engineered optical lattices. Optical lattice is normal to the wall. By monitoring the wall-induced clock shift at individual wells of the lattice, one would measure the dependence of the atom-wall interaction on the atom-wall separation. We find that the induced clock shifts are large and observable at already experimentally demonstrated levels of accuracy. We show that this scheme may uniquely probe the long-range atom-wall interaction in all three qualitatively distinct regimes of the interaction: van der Waals (image-charge interaction), Casimir-Polder (QED vacuum fluctuations), and Lifshitz (thermal-bath fluctuations) regimes.

  18. Controllable clock circuit design in PEM system

    International Nuclear Information System (INIS)

    A high-precision synchronized clock circuit design will be presented, which can supply steady, reliable and anti-jamming clock signal for the data acquirement (DAQ) system of Positron Emission Mammography (PEM). This circuit design is based on the Single-Chip Microcomputer and high-precision clock chip, and can achieve multiple controllable clock signals. The jamming between the clock signals can be reduced greatly with the differential transmission. Meanwhile, the adoption of CAN bus control in the clock circuit can prompt the clock signals to be transmitted or masked simultaneously when needed. (authors)

  19. Circadian clock components in the rat neocortex

    DEFF Research Database (Denmark)

    Rath, Martin Fredensborg; Rohde, Kristian; Fahrenkrug, Jan;

    2013-01-01

    The circadian master clock of the mammalian brain resides in the suprachiasmatic nucleus (SCN) of the hypothalamus. At the molecular level, the clock of the SCN is driven by a transcriptional/posttranslational autoregulatory network with clock gene products as core elements. Recent investigations...... have shown the presence of peripheral clocks in extra-hypothalamic areas of the central nervous system. However, knowledge on the clock gene network in the cerebral cortex is limited. We here show that the mammalian clock genes Per1, Per2, Per3, Cry1, Cry2, Bmal1, Clock, Nr1d1 and Dbp are expressed...

  20. Pump application and maintenance

    International Nuclear Information System (INIS)

    Nuclear maintenance programs are typically organized by overall application, function, cost impact, and failure histories. Each maintenance program is uniquely tailored for each plant's specific goals and objectives. Most maintenance programs include pump maintenance within an application and/or a function. NMAC provides guidance on maintenance, troubleshooting, and applications of Deep Draft Vertical Centrifugal Pumps, Main Coolant Pump Seals, Feedwater Pumps, and Charging Pumps. Each maintenance guide includes a technical discussion of the design and operating issues which influence pump and component performance, reliability, and availability. The guides also discuss comprehensive inspection and corresponding repair Advisory groups consisting of utility, manufacturer, and regulatory representatives oversee the development of the NMAC guides, and review by utility personnel further augments the development process

  1. Circadian Clocks, Stress, and Immunity

    Science.gov (United States)

    Dumbell, Rebecca; Matveeva, Olga; Oster, Henrik

    2016-01-01

    In mammals, molecular circadian clocks are present in most cells of the body, and this circadian network plays an important role in synchronizing physiological processes and behaviors to the appropriate time of day. The hypothalamic–pituitary–adrenal endocrine axis regulates the response to acute and chronic stress, acting through its final effectors – glucocorticoids – released from the adrenal cortex. Glucocorticoid secretion, characterized by its circadian rhythm, has an important role in synchronizing peripheral clocks and rhythms downstream of the master circadian pacemaker in the suprachiasmatic nucleus. Finally, glucocorticoids are powerfully anti-inflammatory, and recent work has implicated the circadian clock in various aspects and cells of the immune system, suggesting a tight interplay of stress and circadian systems in the regulation of immunity. This mini-review summarizes our current understanding of the role of the circadian clock network in both the HPA axis and the immune system, and discusses their interactions. PMID:27199894

  2. Circadian clock, cell cycle and cancer

    OpenAIRE

    Cansu Özbayer; İrfan Değirmenci

    2011-01-01

    There are a few rhythms of our daily lives that we are under the influence. One of them is characterized by predictable changes over a 24-hour timescale called circadian clock. This cellular clock is coordinated by the suprachiasmatic nucleus in the anterior hypothalamus. The clock consist of an autoregulatory transcription-translation feedback loop compose of four genes/proteins; BMAL1, Clock, Cyrptochrome, and Period. BMAL 1 and Clock are transcriptional factors and Period and Cyrptochrome ...

  3. Gravitomagnetism and Relative Observer Clock Effects

    OpenAIRE

    Bini, Donato; Jantzen, Robert T; Mashhoon, Bahram

    2000-01-01

    The gravitomagnetic clock effect and the Sagnac effect for circularly rotating orbits in stationary axisymmetric spacetimes are studied from a relative observer point of view, clarifying their relationships and the roles played by special observer families. In particular Semer\\'ak's recent characterization of extremely accelerated observers in terms of the two-clock clock effect is shown to be complemented by a similarly special property of the single-clock clock effect.

  4. Variable molecular clocks in hominoids

    OpenAIRE

    Elango, Navin; Thomas, James W.; Yi, Soojin V.

    2006-01-01

    Generation time is an important determinant of a neutral molecular clock. There are several human-specific life history traits that led to a substantially longer generation time in humans than in other hominoids. Indeed, a long generation time is considered an important trait that distinguishes humans from their closest relatives. Therefore, humans may exhibit a significantly slower molecular clock as compared to other hominoids. To investigate this hypothesis, we performed a large-scale anal...

  5. The circadian clock in mammals

    OpenAIRE

    Zordan, Mauro; Kyriacou, Charalambos P

    2000-01-01

    The basic physiological and anatomical basis for circadian rhythms in mammalian behaviour and physiology is introduced. The pathways involved in photic entrainment of the circadian clock are discussed in relation of new findings that identify the molecules that are involved in signalling between the environment and the clock. The molecular basis of endogenous cycles is described in the mouse, and compared to the mechanism that is present in the fly. Finally we speculate on the relationship be...

  6. The circadian clock in mammals

    OpenAIRE

    Zordan, M. A.; Kyriacou, C P

    2005-01-01

    The basic physiological and anatomical basis for circadian rhythms in mammalian behaviour and physiology is introduced. The pathways involved in photic entrainment of the circadian clock are discussed in relation of new findings that identify the molecules that are involved in signalling between the environment and the clock. The molecular basis of endogenous cycles is described in the mouse, and compared to the mechanism that is present in the fly. Finally we speculate on the relationship be...

  7. Magic Wavelengths for a Lattice Trapped Rubidium Four-Level Active Optical Clock

    International Nuclear Information System (INIS)

    After being pumped from the 5s1/2 ground state to the 6p1/2 state, the population inversion between 6s1/2 and 5p1/2,3/2 can be established for a rubidium four-level active optical clock. We calculate the ac Stark shift due to lattice trapping laser which dominates the frequency shift of clock transition in a lattice trapped rubidium four-level active optical clock. Several magic wavelengths are found, which can form desired optical lattice trapping potential. By choosing a proper intensity and linewidth of the trapping laser, the fractional frequency uncertainty of clock transition due to the ac Stark shift of the trapping laser, is estimated to be below 10−18

  8. Atomic clock ensemble in space

    International Nuclear Information System (INIS)

    Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. Operated in the microgravity environment of the International Space Station, the ACES clocks, PHARAO and SHM, will generate a frequency reference reaching instability and inaccuracy at the 1 · 10−16 level. A link in the microwave domain (MWL) and an optical link (ELT) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. Space-to-ground and ground-to-ground comparisons of atomic frequency standards will be used to test Einstein's theory of general relativity including a precision measurement of the gravitational red-shift, a search for time variations of fundamental constants, and Lorentz Invariance tests. Applications in geodesy, optical time transfer, and ranging will also be supported. ACES has now reached an advanced technology maturity, with engineering models completed and successfully tested and flight hardware under development. This paper presents the ACES mission concept and the status of its main instruments.

  9. Circadian clocks, epigenetics, and cancer

    KAUST Repository

    Masri, Selma

    2015-01-01

    The interplay between circadian rhythm and cancer has been suggested for more than a decade based on the observations that shift work and cancer incidence are linked. Accumulating evidence implicates the circadian clock in cancer survival and proliferation pathways. At the molecular level, multiple control mechanisms have been proposed to link circadian transcription and cell-cycle control to tumorigenesis.The circadian gating of the cell cycle and subsequent control of cell proliferation is an area of active investigation. Moreover, the circadian clock is a transcriptional system that is intricately regulated at the epigenetic level. Interestingly, the epigenetic landscape at the level of histone modifications, DNA methylation, and small regulatory RNAs are differentially controlled in cancer cells. This concept raises the possibility that epigenetic control is a common thread linking the clock with cancer, though little scientific evidence is known to date.This review focuses on the link between circadian clock and cancer, and speculates on the possible connections at the epigenetic level that could further link the circadian clock to tumor initiation or progression.

  10. Quantum pumping in graphene with a perpendicular magnetic field

    OpenAIRE

    R. P. Tiwari; Blaauboer, M.

    2010-01-01

    We consider quantum pumping of Dirac fermions in a monolayer of graphene in the presence of a perpendicular magnetic field in the central pumping region. The two external pump parameters are electrical voltages applied to the graphene sheet on either side of the pumping region. We analyze this pump within scattering matrix formalism and calculate both pumped charge and spin currents. The predicted charge currents are of the order of 1000 nA, which is readily observable using current technology.

  11. Charge distribution in a 5 kW heat pump using propane as working fluid : Part II: Modelling of liquid hold-up

    OpenAIRE

    Samoteeva, Oxana; Fernando, Primal; Palm, Björn; Lundqvist, Per

    2001-01-01

    A theoretical model for prediction of the amount of refrigerant in condenser and evaporator of a 5kW capacity heat pump is developed. Condenser and evaporator of the experimental test rig are SWEP Brazed Plate Heat Exchangers (BPHE). Plate heat exchangers are widely used in refrigeration and heat pump applications today. However, the mechanisms of boiling and condensation in BPHE represent a difficult issue, for which only few models are developed and presented in published literature. The mo...

  12. Colloquium: Physics of optical lattice clocks

    International Nuclear Information System (INIS)

    Recently invented and demonstrated optical lattice clocks hold great promise for improving the precision of modern time keeping. These clocks aim at the 10-18 fractional accuracy, which translates into a clock that would neither lose nor gain a fraction of a second over an estimated age of the Universe. In these clocks, millions of atoms are trapped and interrogated simultaneously, dramatically improving clock stability. Here the principles of operation of these clocks are discussed and, in particular, a novel concept of magic trapping of atoms in optical lattices. Recently proposed microwave lattice clocks are also highlights and several applications that employ the optical lattice clocks as a platform for precision measurements and quantum information processing.

  13. Acting with the Clock: Clocking Practices in Early Childhood

    Science.gov (United States)

    Pacini-Ketchabaw, Veronica

    2012-01-01

    In this article, the author addresses intra-actions that take place among humans and non-human others--the physical world, the materials--in early childhood education's everyday practices. Her object of study is the clock. Specifically, she provides an example of what it might mean to account for the intra-activity of the material-discursive…

  14. Experimental Realization of a Quantum Spin Pump

    DEFF Research Database (Denmark)

    Watson, Susan; Potok, R.; M. Marcus, C.;

    2003-01-01

    We demonstrate the operation of a quantum spin pump based on cyclic radio-frequency excitation of a GaAs quantum dot, including the ability to pump pure spin without pumping charge. The device takes advantage of bidirectional mesoscopic fluctuations of pumped current, made spin-dependent by the...... application of an in-plane Zeeman field. Spin currents are measured by placing the pump in a focusing geometry with a spin-selective collector....

  15. Identifying Nonstationary Clock Noises in Navigation Systems

    OpenAIRE

    Patrizia Tavella; Lorenzo Galleani

    2008-01-01

    The stability of the atomic clocks on board the satellites of a navigation system should remain constant with time. In reality there are numerous physical phenomena that make the behavior of the clocks a function of time, and for this reason we have recently introduced the dynamic Allan variance (DAVAR), a measure of the time-varying stability of an atomic clock. In this paper we discuss the dynamic Allan variance for phase and frequency jumps, two common nonstationarities of atomic clocks. T...

  16. Single-transistor-clocked flip-flop

    Science.gov (United States)

    Zhao, Peiyi; Darwish, Tarek; Bayoumi, Magdy

    2005-08-30

    The invention provides a low power, high performance flip-flop. The flip-flop uses only one clocked transistor. The single clocked transistor is shared by the first and second branches of the device. A pulse generator produces a clock pulse to trigger the flip-flop. In one preferred embodiment the device can be made as a static explicit pulsed flip-flop which employs only two clocked transistors.

  17. 47 CFR 80.935 - Station clock.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Station clock. 80.935 Section 80.935... MARITIME SERVICES Compulsory Radiotelephone Installations for Small Passenger Boats § 80.935 Station clock. Each station subject to this subpart must have a working clock or timepiece readily available to...

  18. Collisionally induced atomic clock shifts and correlations

    International Nuclear Information System (INIS)

    We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature 87Sr 1S0 (F=9/2) atomic clock in a magic wavelength optical lattice are presented.

  19. Pocket pumped image analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kotov, I.V., E-mail: kotov@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973 (United States); O' Connor, P. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Murray, N. [Centre for Electronic Imaging, Open University, Milton Keynes, MK7 6AA (United Kingdom)

    2015-07-01

    The pocket pumping technique is used to detect small electron trap sites. These traps, if present, degrade CCD charge transfer efficiency. To reveal traps in the active area, a CCD is illuminated with a flat field and, before image is read out, accumulated charges are moved back and forth number of times in parallel direction. As charges are moved over a trap, an electron is removed from the original pocket and re-emitted in the following pocket. As process repeats one pocket gets depleted and the neighboring pocket gets excess of charges. As a result a “dipole” signal appears on the otherwise flat background level. The amplitude of the dipole signal depends on the trap pumping efficiency. This paper is focused on trap identification technique and particularly on new methods developed for this purpose. The sensor with bad segments was deliberately chosen for algorithms development and to demonstrate sensitivity and power of new methods in uncovering sensor defects.

  20. Charge exchange system

    Science.gov (United States)

    Anderson, Oscar A.

    1978-01-01

    An improved charge exchange system for substantially reducing pumping requirements of excess gas in a controlled thermonuclear reactor high energy neutral beam injector. The charge exchange system utilizes a jet-type blanket which acts simultaneously as the charge exchange medium and as a shield for reflecting excess gas.

  1. CLOCK and NPAS2 have overlapping roles in the suprachiasmatic circadian clock

    OpenAIRE

    DeBruyne, Jason P.; Weaver, David R.; Reppert, Steven M.

    2007-01-01

    Heterodimers of CLOCK and BMAL1, bHLH-PAS transcription factors, are believed to be the major transcriptional regulators of the circadian clock mechanism in mammals. However, a recent study shows that CLOCK-deficient mice continue to exhibit robust behavioral and molecular rhythms. Here we report that the transcription factor NPAS2 (MOP4) is able to functionally substitute for CLOCK in the master brain clock in mice to regulate circadian rhythmicity.

  2. Centrifugal pumps

    CERN Document Server

    Anderson, HH

    1981-01-01

    Centrifugal Pumps describes the whole range of the centrifugal pump (mixed flow and axial flow pumps are dealt with more briefly), with emphasis on the development of the boiler feed pump. Organized into 46 chapters, this book discusses the general hydrodynamic principles, performance, dimensions, type number, flow, and efficiency of centrifugal pumps. This text also explains the pumps performance; entry conditions and cavitation; speed and dimensions for a given duty; and losses. Some chapters further describe centrifugal pump mechanical design, installation, monitoring, and maintenance. The

  3. Detection of spin pumping from YIG by spin-charge conversion in a Au /Ni80Fe20 spin-valve structure

    Science.gov (United States)

    Vlietstra, N.; van Wees, B. J.; Dejene, F. K.

    2016-07-01

    Many experiments have shown the detection of spin currents driven by radio-frequency spin pumping from yttrium iron garnet (YIG), by making use of the inverse spin-Hall effect, which is present in materials with strong spin-orbit coupling, such as Pt. Here we show that it is also possible to directly detect the resonance-driven spin current using Au|permalloy (Py, Ni80Fe20 ) devices, where Py is used as a detector for the spins pumped across a YIG|Au interface. This detection mechanism is equivalent to the spin-current detection in metallic nonlocal spin-valve devices. By finite element modeling we compare the pumped spin current from a reference Pt strip with the detected signals from the Au|Py devices. We find that for one series of Au|Py devices the calculated spin pumping signals mostly match the measurements, within 20%, whereas for a second series of devices additional signals are present which are up to a factor 10 higher than the calculated signals from spin pumping. We also identify contributions from thermoelectric effects caused by the resonant (spin-related) and nonresonant heating of the YIG. Thermocouples are used to investigate the presence of these thermal effects and to quantify the magnitude of the spin-(dependent-)Seebeck effect. Several additional features are observed, which are also discussed.

  4. Clock Drawing in Developmental Dyslexia.

    Science.gov (United States)

    Eden, Guinevere F.; Wood, Frank B.; Stein, John F.

    2003-01-01

    A study involving 93 children (ages 10-12), 295 with poor reading skills, found many children with dyslexia and some garden-variety poor readers showed significant left neglect on the Clock Drawing Test. In poor readers with dyslexia, spatial construction deficits were observed like those of parents with acquired right-hemisphere lesions.…

  5. A quantum network of clocks

    Science.gov (United States)

    Komar, Peter; Kessler, Eric; Bishof, Michael; Jiang, Liang; Sorensen, Anders; Ye, Jun; Lukin, Mikhail

    2014-05-01

    Shared timing information constitutes a key resource for positioning and navigation with a direct correspondence between timing accuracy and precision in applications such as the Global Positioning System (GPS). By combining precision metrology and quantum networks, we propose here a quantum, cooperative protocol for the operation of a network consisting of geographically remote optical atomic clocks. Using non-local entangled states, we demonstrate an optimal utilization of the global network resources, and show that such a network can be operated near the fundamental limit set by quantum theory yielding an ultra-precise clock signal. Furthermore, the internal structure of the network, combined with basic techniques from quantum communication, guarantees security both from internal and external threats. Realization of such a global quantum network of clocks may allow construction of a real-time single international time scale (world clock) with unprecedented stability and accuracy. See also: Komar et al. arXiv:1310.6045 (2013) and Kessler et al. arXiv:1310.6043 (2013).

  6. Clock gene expression during development

    Czech Academy of Sciences Publication Activity Database

    Sumová, Alena; Bendová, Zdeňka; Sládek, Martin; Kováčiková, Zuzana; El-Hennamy, Rehab; Laurinová, Kristýna; Illnerová, Helena

    2007-01-01

    Roč. 191, Suppl.658 (2007), s. 18-18. ISSN 1748-1708. [Joint meeting of The Slovak Physiological Society, The Physiological Society and The Federation of European Physiological Societies. 11.09.2007-14.09.2007, Bratislava] Institutional research plan: CEZ:AV0Z50110509 Keywords : cpr1 * clock genes * suprachiasmatic nucleus * rat Subject RIV: FB - Endocrinology, Diabetology, Metabolism, Nutrition

  7. Automatic control of clock duty cycle

    Science.gov (United States)

    Feng, Xiaoxin (Inventor); Roper, Weston (Inventor); Seefeldt, James D. (Inventor)

    2010-01-01

    In general, this disclosure is directed to a duty cycle correction (DCC) circuit that adjusts a falling edge of a clock signal to achieve a desired duty cycle. In some examples, the DCC circuit may generate a pulse in response to a falling edge of an input clock signal, delay the pulse based on a control voltage, adjust the falling edge of the input clock signal based on the delayed pulse to produce an output clock signal, and adjust the control voltage based on the difference between a duty cycle of the output clock signal and a desired duty cycle. Since the DCC circuit adjusts the falling edge of the clock cycle to achieve a desired duty cycle, the DCC may be incorporated into existing PLL control loops that adjust the rising edge of a clock signal without interfering with the operation of such PLL control loops.

  8. Circadian clock, cell cycle and cancer

    Directory of Open Access Journals (Sweden)

    Cansu Özbayer

    2011-12-01

    Full Text Available There are a few rhythms of our daily lives that we are under the influence. One of them is characterized by predictable changes over a 24-hour timescale called circadian clock. This cellular clock is coordinated by the suprachiasmatic nucleus in the anterior hypothalamus. The clock consist of an autoregulatory transcription-translation feedback loop compose of four genes/proteins; BMAL1, Clock, Cyrptochrome, and Period. BMAL 1 and Clock are transcriptional factors and Period and Cyrptochrome are their targets. Period and Cyrptochrome dimerize in the cytoplasm to enter the nucleus where they inhibit Clock/BMAL activity.It has been demonstrate that circadian clock plays an important role cellular proliferation, DNA damage and repair mechanisms, checkpoints, apoptosis and cancer.

  9. Optical lattice clock with Strontium atoms; Horloge a reseau optique a atomes de strontium

    Energy Technology Data Exchange (ETDEWEB)

    Baillard, X

    2008-01-15

    This thesis presents the latest achievements regarding the optical lattice clock with Strontium atoms developed at LNE-SYRTE. After a review of the different types of optical clocks that are currently under development, we stress on the concept of optical lattice clock which was first imagined for Sr{sup 87} using the {sup 1}S{sub 0} {yields} {sup 3}P{sub 0} transition. We exhibit the features of this atom, in particular the concept of magic wavelength for the trap, and the achievable performances for this kind of clock. The second part presents the experimental aspects, insisting particularly on the ultra-stable laser used for the interrogation of the atoms which is a central part of the experiment. Among the latest improvements, an optical pumping phase and an interrogation phase using a magnetic field have been added in order to refine the evaluation of the Zeeman effect. Finally, the last part presents the experimental results. The last evaluation of the clock using Sr{sup 87} atoms allowed us to reach a frequency accuracy of 2.6*10{sup -15} and a measurement in agreement with the one made at JILA (Tokyo university) at the 10{sup -15} level. On another hand, thanks to recent theoretical proposals, we made a measurement using the bosonic isotope Sr{sup 88} by adapting the experimental setup. This measurement represents the first evaluation for this type of clock, with a frequency accuracy of 7*10{sup -14}. (author)

  10. Thermally reliable clocked non-volatile spin wave logic device

    Science.gov (United States)

    Dutta, Sourav; Nikonov, Dmitri; Manipatruni, Sasikanth; Young, Ian; Naeemi, Azad

    The possibility of utilizing spin waves for information transmission and computation has been an area of active research due to the unique ability to manipulate the amplitude and phase of the spin waves for building complex logic circuits. Here, we present a comprehensive scheme for building a thermally reliable clocked non-volatile spin wave logic device (SWLD) by introducing a charge-to-spin converter that translates information from electrical domain to spin domain, exploiting the magneto-electric effect for spin wave transmission, detection and non-volatile memory, utilizing the phase of the spin wave as information token, ensuring phase-dependent deterministic switching of the magnetoelectric spin wave detector in the presence of thermal noise via compensation of demagnetization and a novel clocking scheme that ensures sequential transmission of information in a cascaded SWLD and non- reciprocity

  11. Mitigating aliasing in atomic clocks

    Science.gov (United States)

    Uys, Hermann; Akhalwaya, Ismail; Sastrawan, Jarrah; Biercuk, Michael

    2015-05-01

    Passive atomic clocks periodically calibrate a classical local oscillator against an atomic quantum reference through feedback. The periodic nature of this correction leads to undesirable aliasing noise. The Dick Effect, is a special case of aliasing noise consisting of the down-conversion of clock noise at harmonics of the correction frequency to a frequency of zero. To combat the Dick effect and aliasing noise in general, we suggest an extension to the usual feedback protocol, in which we incorporate information from multiple past measurements into the correction after the most recent measurement, approximating a crude low pass anti-aliasing filter of the noise. An analytical frequency domain analysis of the approach is presented and supported by numerical time domain simulations.

  12. Hanle detection for optical clocks

    CERN Document Server

    Zhang, Xiaogang; Pan, Duo; Chen, Peipei; Xue, Xiaobo; Zhuang, Wei; Chen, Jingbiao

    2014-01-01

    Considering the strong inhomogeneous spatial polarization and intensity distribution of spontaneous decay fluorescence due to the Hanle effect, we propose and demonstrate a universe Hanle detection configuration of electron-shelving method for optical clocks. Experimental results from Ca atomic beam optical frequency standard with 423 nm electron-shelving method show that a designed Hanle detection geometry with optimized magnetic field direction, detection laser beam propagation and polarization direction, and detector position can improve the fluorescence collection rate by more than one order of magnitude comparing with that of inefficient geometry. With the fixed 423 nm fluorescence, the improved 657 nm optical frequency standard signal intensity is presented. And the potential application of the Hanle detection geometry designed for facilitating the fluorescence collection for optical lattice clock with a limited solid angle of the fluorescence collection has been discussed. This Hanle detection configur...

  13. Nonadiabatic pure spin pumping in zigzag graphene nanoribbons with proximity induced ferromagnetism

    OpenAIRE

    Cheraghchi, Hosein

    2015-01-01

    By combining Floquet theory with Green's function formalism, we present non-adiabatic quantum spin and charge pumping through a zigzag ferromagnetic graphene nanoribbon including a double-barriers structure driven weakly by two local $ac$ gate voltages operating with a phase-lag. Over a wide range of Fermi energies, interesting quantum pumping such as i) pure spin pumping with zero net charge pumping, ii) pure charge pumping and iii) fully spin polarized pumping can be achieved by tuning and ...

  14. Signal processing in cellular clocks

    OpenAIRE

    Forger, Daniel B.

    2011-01-01

    Many biochemical events within a cell need to be timed properly to occur at specific times of day, after other events have happened within the cell or in response to environmental signals. The cellular biochemical feedback loops that time these events have already received much recent attention in the experimental and modeling communities. Here, we show how ideas from signal processing can be applied to understand the function of these clocks. Consider two signals from the network s(t) and r(...

  15. Gaming in Combinatorial Clock Auctions

    OpenAIRE

    Janssen, Maarten; Karamychev, Vladimir

    2013-01-01

    textabstractIn recent years, Combinatorial Clock Auctions (CCAs) have been used around the world to allocate frequency spectrum for mobile telecom licenses. CCAs are claimed to significantly reduce the scope for gaming or strategic bidding. In this paper, we show, however, that CCAs significantly enhance the possibilities for strategic bidding. Real bidders in telecom markets are not only interested in the spectrum they win themselves and the price they pay for that, but also in the price com...

  16. Design principles underlying circadian clocks.

    OpenAIRE

    Rand, D.A.; Shulgin, B. V.; D. Salazar; Millar, A. J.

    2004-01-01

    A fundamental problem for regulatory networks is to understand the relation between form and function: to uncover the underlying design principles of the network. Circadian clocks present a particularly interesting instance, as recent work has shown that they have complex structures involving multiple interconnected feedback loops with both positive and negative feedback. While several authors have speculated on the reasons for this, a convincing explanation is still lacking.We analyse both t...

  17. Hanle Detection for Optical Clocks

    Directory of Open Access Journals (Sweden)

    Xiaogang Zhang

    2015-01-01

    Full Text Available Considering the strong inhomogeneous spatial polarization and intensity distribution of spontaneous decay fluorescence due to the Hanle effect, we propose and demonstrate a universe Hanle detection configuration of electron-shelving method for optical clocks. Experimental results from Ca atomic beam optical frequency standard with electron-shelving method show that a designed Hanle detection geometry with optimized magnetic field direction, detection laser beam propagation and polarization direction, and detector position can improve the fluorescence collection rate by more than one order of magnitude comparing with that of inefficient geometry. With the fixed 423 nm fluorescence, the improved 657 nm optical frequency standard signal intensity is presented. The potential application of the Hanle detection geometry designed for facilitating the fluorescence collection for optical lattice clock with a limited solid angle of the fluorescence collection has been discussed. The Hanle detection geometry is also effective for ion detection in ion optical clock and quantum information experiments. Besides, a cylinder fluorescence collection structure is designed to increase the solid angle of the fluorescence collection in Ca atomic beam optical frequency standard.

  18. Hanle detection for optical clocks.

    Science.gov (United States)

    Zhang, Xiaogang; Zhang, Shengnan; Pan, Duo; Chen, Peipei; Xue, Xiaobo; Zhuang, Wei; Chen, Jingbiao

    2015-01-01

    Considering the strong inhomogeneous spatial polarization and intensity distribution of spontaneous decay fluorescence due to the Hanle effect, we propose and demonstrate a universe Hanle detection configuration of electron-shelving method for optical clocks. Experimental results from Ca atomic beam optical frequency standard with electron-shelving method show that a designed Hanle detection geometry with optimized magnetic field direction, detection laser beam propagation and polarization direction, and detector position can improve the fluorescence collection rate by more than one order of magnitude comparing with that of inefficient geometry. With the fixed 423 nm fluorescence, the improved 657 nm optical frequency standard signal intensity is presented. The potential application of the Hanle detection geometry designed for facilitating the fluorescence collection for optical lattice clock with a limited solid angle of the fluorescence collection has been discussed. The Hanle detection geometry is also effective for ion detection in ion optical clock and quantum information experiments. Besides, a cylinder fluorescence collection structure is designed to increase the solid angle of the fluorescence collection in Ca atomic beam optical frequency standard. PMID:25734183

  19. Heat pumps

    CERN Document Server

    Macmichael, DBA

    1988-01-01

    A fully revised and extended account of the design, manufacture and use of heat pumps in both industrial and domestic applications. Topics covered include a detailed description of the various heat pump cycles, the components of a heat pump system - drive, compressor, heat exchangers etc., and the more practical considerations to be taken into account in their selection.

  20. The circadian clock coordinates ribosome biogenesis.

    Directory of Open Access Journals (Sweden)

    Céline Jouffe

    Full Text Available Biological rhythms play a fundamental role in the physiology and behavior of most living organisms. Rhythmic circadian expression of clock-controlled genes is orchestrated by a molecular clock that relies on interconnected negative feedback loops of transcription regulators. Here we show that the circadian clock exerts its function also through the regulation of mRNA translation. Namely, the circadian clock influences the temporal translation of a subset of mRNAs involved in ribosome biogenesis by controlling the transcription of translation initiation factors as well as the clock-dependent rhythmic activation of signaling pathways involved in their regulation. Moreover, the circadian oscillator directly regulates the transcription of ribosomal protein mRNAs and ribosomal RNAs. Thus the circadian clock exerts a major role in coordinating transcription and translation steps underlying ribosome biogenesis.

  1. Heat pumps

    CERN Document Server

    Brodowicz, Kazimierz; Wyszynski, M L; Wyszynski

    2013-01-01

    Heat pumps and related technology are in widespread use in industrial processes and installations. This book presents a unified, comprehensive and systematic treatment of the design and operation of both compression and sorption heat pumps. Heat pump thermodynamics, the choice of working fluid and the characteristics of low temperature heat sources and their application to heat pumps are covered in detail.Economic aspects are discussed and the extensive use of the exergy concept in evaluating performance of heat pumps is a unique feature of the book. The thermodynamic and chemical properties o

  2. Optical to microwave clock frequency ratios with a nearly continuous strontium optical lattice clock

    CERN Document Server

    Lodewyck, Jérôme; Bookjans, Eva; Robyr, Jean-Luc; Shi, Chunyan; Vallet, Grégoire; Targat, Rodolphe Le; Nicolodi, Daniele; Coq, Yann Le; Guéna, Jocelyne; Abgrall, Michel; Rosenbusch, Peter; Bize, Sébastien

    2016-01-01

    Optical lattice clocks are at the forefront of frequency metrology. Both the instability and systematic uncertainty of these clocks have been reported to be two orders of magnitude smaller than the best microwave clocks. For this reason, a redefinition of the SI second based on optical clocks seems possible in the near future. However, the operation of optical lattice clocks has not yet reached the reliability that microwave clocks have achieved so far. In this paper, we report on the operation of a strontium optical lattice clock that spans several weeks, with more than 80% uptime. We make use of this long integration time to demonstrate a reproducible measurement of frequency ratios between the strontium clock transition and microwave Cs primary and Rb secondary frequency standards.

  3. Atomic clocks: A mathematical physics perspective

    International Nuclear Information System (INIS)

    Full text: Accuracy of atomic clocks (since their introduction in 50's) is increasing by roughly one order per decade. A natural theoretical problem posed by this development is to seek the ultimate accuracy of atomic clocks and means to achieve it. This problem was indeed extensively studied and various bounds on the accuracy are well understood, e.g. shot noise limit. I would present a mathematical minded (but simple) model of atomic clocks and discuss accuracy bounds within the model. (author)

  4. The Square Light Clock and Special Relativity

    Science.gov (United States)

    Galli, J. Ronald; Amiri, Farhang

    2012-01-01

    A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45[degree] angle at each corner of a square of length L[subscript 0], shown in Fig. 1. Here we have shown the events as measured in the rest frame of the square light clock. By…

  5. Unraveling the circadian clock in Arabidopsis

    OpenAIRE

    Wang, Xiaoxue; Ma, Ligeng

    2012-01-01

    The circadian clock is an endogenous timing system responsible for coordinating an organism’s biological processes with its environment. Interlocked transcriptional feedback loops constitute the fundamental architecture of the circadian clock. In Arabidopsis, three feedback loops, the core loop, morning loop and evening loop, comprise a network that is the basis of the circadian clock. The components of these three loops are regulated in distinct ways, including transcriptional, post-transcri...

  6. Performance Evaluation of Clock Synchronization Algorithms

    OpenAIRE

    Anceaume, Emmanuelle; Puaut, Isabelle

    1998-01-01

    Clock synchronization algorithms ensure that physically dispersed processors have a common knowledge of time. This report proposes a survey of software fault-tolerant clock synchronization algorithms: deterministic, probabilistic and statistical ; internal and external ; and resilient from crash to Byzantine failures. Our survey is based on a classification of clock synchronization algorithms (according to their internal structure and to three orthogonal and independent basic building blocks ...

  7. Interaction of circadian clock proteins PER2 and CRY with BMAL1 and CLOCK

    OpenAIRE

    Bordon Alain; Tallone Tiziano; Langmesser Sonja; Rusconi Sandro; Albrecht Urs

    2008-01-01

    Abstract Background Circadian oscillation of clock-controlled gene expression is mainly regulated at the transcriptional level. Heterodimers of CLOCK and BMAL1 act as activators of target gene transcription; however, interactions of PER and CRY proteins with the heterodimer abolish its transcriptional activation capacity. PER and CRY are therefore referred to as negative regulators of the circadian clock. To further elucidate the mechanism how positive and negative components of the clock int...

  8. Classical and quantum pumping in closed systems

    OpenAIRE

    Cohen, Doron

    2002-01-01

    Pumping of charge (Q) in a closed ring geometry is not quantized even in the strict adiabatic limit. The deviation form exact quantization can be related to the Thouless conductance. We use Kubo formalism as a starting point for the calculation of both the dissipative and the adiabatic contributions to Q. As an application we bring examples for classical dissipative pumping, classical adiabatic pumping, and in particular we make an explicit calculation for quantum pumping in case of the simpl...

  9. Lasing and suppressed cavity-pulling effect of Cesium active optical clock

    CERN Document Server

    Xu, Zhichao; Chen, Jingbiao

    2014-01-01

    We experimentally demonstrate the collective emission behavior and suppressed cavity-pulling effect of four-level active optical clock with Cesium atoms. Thermal Cesium atoms in a glass cell velocity selective pumped with a 455.5 nm laser operating at 6S$_{1/2}$ to 7P$_{3/2}$ transition are used as lasing medium. Population inverted Cesium atoms between 7S$_{1/2}$ and 6P$_{3/2}$ levels are optical weakly coupled by a pair cavity mirrors working at deep bad-cavity regime with a finesse of 4.3, and the ratio between cavity bandwidth and gain bandwidth is approximately 45. With increased 455.5 nm pumping laser intensity, the output power of cesium active optical clock at 1469.9 nm from 7S$_{1/2}$ level to 6P$_{3/2}$ level shows a threshold and reach a power of 13 $\\mu$W. Active optical clock would dramatically improve the optical clock stability since the lasing frequency does not follow the cavity length variation exactly, but in a form of suppressed cavity pulling effect. In this letter the cavity pulling effe...

  10. Pumping life

    DEFF Research Database (Denmark)

    Sitsel, Oleg; Dach, Ingrid; Hoffmann, Robert Daniel

    2012-01-01

    The name PUMPKIN may suggest a research centre focused on American Halloween traditions or the investigation of the growth of vegetables – however this would be misleading. Researchers at PUMPKIN, short for Centre for Membrane Pumps in Cells and Disease, are in fact interested in a large family of...... membrane proteins: P-type ATPase pumps. This article takes the reader on a tour from Aarhus to Copenhagen, from bacteria to plants and humans, and from ions over protein structures to diseases caused by malfunctioning pump proteins. The magazine Nature once titled work published from PUMPKIN ‘Pumping ions......’. Here we illustrate that the pumping of ions means nothing less than the pumping of life....

  11. Centrifugal pumps

    CERN Document Server

    Gülich, Johann Friedrich

    2014-01-01

    This book gives an unparalleled, up-to-date, in-depth treatment of all kinds of flow phenomena encountered in centrifugal pumps including the complex interactions of fluid flow with vibrations and wear of materials. The scope includes all aspects of hydraulic design, 3D-flow phenomena and partload operation, cavitation, numerical flow calculations, hydraulic forces, pressure pulsations, noise, pump vibrations (notably bearing housing vibration diagnostics and remedies), pipe vibrations, pump characteristics and pump operation, design of intake structures, the effects of highly viscous flows, pumping of gas-liquid mixtures, hydraulic transport of solids, fatigue damage to impellers or diffusers, material selection under the aspects of fatigue, corrosion, erosion-corrosion or hydro-abrasive wear, pump selection, and hydraulic quality criteria. As a novelty, the 3rd ed. brings a fully analytical design method for radial impellers, which eliminates the arbitrary choices inherent to former design procedures. The d...

  12. Introduction: Finding new clock components; past and future

    OpenAIRE

    Takahashi, Joseph S.

    2004-01-01

    The molecular mechanism of circadian clocks has been unraveled primarily by the use of phenotype-driven (forward) genetic analysis in a number of model systems. We are now in a position to consider what constitutes a clock component, whether we can establish criteria for clock components, and whether we have found most of the primary clock components? This perspective discusses clock genes and how genetics, molecular biology and biochemistry have been used to find clock gene...

  13. Global synchronization of parallel processors using clock pulse width modulation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.

    2013-04-02

    A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

  14. Progress of the ~(87)Rb Fountain Clock

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zi-Chao; WEI Rong; SHI Chun-Yan; LV De-Sheng; LI Tang; WANG Yu-Zhu

    2009-01-01

    A fountain atomic clock based on cold ~(87)Rb atoms has been in operation in our laboratory for several months.We therefore report the design of the rubidium fountain clock including its physical package,optical system and daily operation.Ramsey fringes have been attained with the signal to noise ratio of about 100.

  15. Could Atomic clocks be affected by neutrinos?

    CERN Document Server

    Hanafi, Hanaa

    2016-01-01

    An atomic clock is a clock device that uses an electronic transition frequency of the electromagnetic spectrum of atoms as a frequency standard in order to derive a time standard since time is the reciprocal of frequency. If the electronic transition frequencies are in an "optical region", we are talking in this case about optical atomic clocks. If they are in an "microwave region" these atomic clocks are made of the metallic element cesium so they are called Cesium atomic clocks. Atomic clocks are the most accurate time and frequency standards known despite the different perturbations that can affect them, a lot of researches were made in this domain to show how the transitions can be different for different type of perturbations..Since atomic clocks are very sensitive devices, based on coherent states (A coherent state tends to loose coherence after interacting). One question can arise (from a lot of questions) which is why cosmic neutrinos are not affecting these clocks? The answer to this question requir...

  16. Fast Clock Recovery for Digital Communications

    Science.gov (United States)

    Tell, R. G.

    1985-01-01

    Circuit extracts clock signal from random non-return-to-zero data stream, locking onto clock within one bit period at 1-gigabitper-second data rate. Circuit used for synchronization in opticalfiber communications. Derives speed from very short response time of gallium arsenide metal/semiconductor field-effect transistors (MESFET's).

  17. Temperature influences in receiver clock modelling

    Science.gov (United States)

    Wang, Kan; Meindl, Michael; Rothacher, Markus; Schoenemann, Erik; Enderle, Werner

    2016-04-01

    In Precise Point Positioning (PPP), hardware delays at the receiver site (receiver, cables, antenna, …) are always difficult to be separated from the estimated receiver clock parameters. As a result, they are partially or fully contained in the estimated "apparent" clocks and will influence the deterministic and stochastic modelling of the receiver clock behaviour. In this contribution, using three years of data, the receiver clock corrections of a set of high-precision Hydrogen Masers (H-Masers) connected to stations of the ESA/ESOC network and the International GNSS Service (IGS) are firstly characterized concerning clock offsets, drifts, modified Allan deviations and stochastic parameters. In a second step, the apparent behaviour of the clocks is modelled with the help of a low-order polynomial and a known temperature coefficient (Weinbach, 2013). The correlations between the temperature and the hardware delays generated by different types of antennae are then analysed looking at daily, 3-day and weekly time intervals. The outcome of these analyses is crucial, if we intend to model the receiver clocks in the ground station network to improve the estimation of station-related parameters like coordinates, troposphere zenith delays and ambiguities. References: Weinbach, U. (2013) Feasibility and impact of receiver clock modeling in precise GPS data analysis. Dissertation, Leibniz Universität Hannover, Germany.

  18. "Molecular Clock" Analogs: A Relative Rates Exercise

    Science.gov (United States)

    Wares, John P.

    2008-01-01

    Although molecular clock theory is a commonly discussed facet of evolutionary biology, undergraduates are rarely presented with the underlying information of how this theory is examined relative to empirical data. Here a simple contextual exercise is presented that not only provides insight into molecular clocks, but is also a useful exercise for…

  19. Progress of the 87Rb Fountain Clock

    International Nuclear Information System (INIS)

    A fountain atomic clock based on cold 87 Rb atoms has been in operation in our laboratory for several months. We therefore report the design of the rubidium fountain clock including its physical package, optical system and daily operation. Ramsey fringes have been attained with the signal to noise ratio of about 100

  20. Network properties of the mammalian circadian clock

    NARCIS (Netherlands)

    Rohling, Johannes Hermanus Theodoor

    2009-01-01

    The biological clock regulates daily and seasonal rhythms in mammals. This clock is located in the suprachiasmatic nuclei (SCN), which are two small nuclei each consisting of 10,000 neurons. The neurons of the SCN endogenously generate a rhythm of approximately 24 hours. Under the influence of the l

  1. A colorful model of the circadian clock.

    Science.gov (United States)

    Reppert, Steven M

    2006-01-27

    The migration of the colorful monarch butterfly provides biologists with a unique model system with which to study the cellular and molecular mechanisms underlying a sophisticated circadian clock. The monarch circadian clock is involved in the induction of the migratory state and navigation over long distances, using the sun as a compass. PMID:16439193

  2. Internal Clock Drift Estimation in Computer Clusters

    Directory of Open Access Journals (Sweden)

    Hicham Marouani

    2008-01-01

    Full Text Available Most computers have several high-resolution timing sources, from the programmable interrupt timer to the cycle counter. Yet, even at a precision of one cycle in ten millions, clocks may drift significantly in a single second at a clock frequency of several GHz. When tracing the low-level system events in computer clusters, such as packet sending or reception, each computer system records its own events using an internal clock. In order to properly understand the global system behavior and performance, as reported by the events recorded on each computer, it is important to estimate precisely the clock differences and drift between the different computers in the system. This article studies the clock precision and stability of several computer systems, with different architectures. It also studies the typical network delay characteristics, since time synchronization algorithms rely on the exchange of network packets and are dependent on the symmetry of the delays. A very precise clock, based on the atomic time provided by the GPS satellite network, was used as a reference to measure clock drifts and network delays. The results obtained are of immediate use to all applications which depend on computer clocks or network time synchronization accuracy.

  3. Tectonic blocks and molecular clocks

    Science.gov (United States)

    2016-01-01

    Evolutionary timescales have mainly used fossils for calibrating molecular clocks, though fossils only really provide minimum clade age constraints. In their place, phylogenetic trees can be calibrated by precisely dated geological events that have shaped biogeography. However, tectonic episodes are protracted, their role in vicariance is rarely justified, the biogeography of living clades and their antecedents may differ, and the impact of such events is contingent on ecology. Biogeographic calibrations are no panacea for the shortcomings of fossil calibrations, but their associated uncertainties can be accommodated. We provide examples of how biogeographic calibrations based on geological data can be established for the fragmentation of the Pangaean supercontinent: (i) for the uplift of the Isthmus of Panama, (ii) the separation of New Zealand from Gondwana, and (iii) for the opening of the Atlantic Ocean. Biogeographic and fossil calibrations are complementary, not competing, approaches to constraining molecular clock analyses, providing alternative constraints on the age of clades that are vital to avoiding circularity in investigating the role of biogeographic mechanisms in shaping modern biodiversity. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325840

  4. Cold atom Clocks and Applications

    CERN Document Server

    Bize, S; Abgrall, M; Marion, H; Maksimovic, I; Cacciapuoti, L; Gruenert, J; Vian, C; Dos Santos, F P; Rosenbusch, P; Lemonde, P; Santarelli, G; Wolf, P; Clairon, A; Luiten, A; Tobar, M; Salomon, C

    2005-01-01

    This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the $^{133}$Cs and $^{87}$Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of $1.6\\times 10^{-14}\\tau^{-1/2}$ where $\\tau $ is the measurement time in seconds is measured. The second advance is a powerful method to control the frequency shift due to cold collisions. These two advances lead to a frequency stability of $2\\times 10^{-16}$ at $50,000s for the first time for primary standards. In addition, these clocks realize the SI second with an accuracy of $7\\times 10^{-16}$, one order of magnitude below that of uncooled devices. In a second part, we describe tests of possible variations of fundamental constants using $^{87}$Rb and $^{133}$Cs fountains. Finally we give an update on the cold atom space clock PHARAO developed in collaboration with CNES. This ...

  5. Single electron relativistic clock interferometer

    CERN Document Server

    Bushev, Pavel; Sholokhov, Dmitry; Kukharchyk, Nadezhda; Zych, Magdalena

    2016-01-01

    Although time is one of the fundamental notions in physics, it does not have a unique description. In quantum theory time is a parameter ordering the succession of the probability amplitudes of a quantum system, while according to relativity theory each system experiences in general a different proper time, depending on the system's world line, due to time to time dilation. It is therefore of fundamental interest to test the notion of time in the regime where both quantum and relativistic effects play a role, for example, when different amplitudes of a single quantum clock experience different magnitudes of time dilation. Here we propose a realization of such an experiment with a single electron in a Penning trap. The clock can be implemented in the electronic spin precession and its time dilation then depends on the radial (cyclotron) state of the electron. We show that coherent manipulation and detection of the electron can be achieved already with present day technology. A single electron in a Penning trap...

  6. A low maintenance Sr optical lattice clock

    CERN Document Server

    Hill, Ian R; Bowden, William; Bridge, Elizabeth M; Donnellan, Sean; Curtis, E Anne; Gill, Patrick

    2016-01-01

    We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation of cooling and trapping lasers. We highlight several measures to increase the reliability of the clock with a view towards the realisation of an optical time-scale. The clock contributed 502 hours of data over a 25 day period (84% uptime) in a recent measurement campaign with several uninterrupted periods of more than 48 hours. An instability of $2\\times10^{-17}$ was reached after $10^5$ s of averaging in an interleaved self-comparison of the clock.

  7. Investigations of laser pumped gas cell atomic frequency standard

    Science.gov (United States)

    Volk, C. H.; Camparo, J. C.; Fueholz, R. P.

    1982-01-01

    The performance characteristics of a rubidium gas cell atomic frequency standard might be improved by replacing the standard rubidium discharge lamp with a single mode laser diode. Aspects of the laser pumped gas cell atomic clock studied include effects due to laser intensity, laser detuning, and the choice of the particular atomic absorption line. Results indicate that the performance of the gas cell clock may be improved by judicious choice of the operating parameters of the laser diode. The laser diode also proved to be a valuable tool in investigating the operation of the conventional gas cell clock. Results concerning linewidths, the light shift effect and the effect of isotopic spin exchange in the conventional gas cell clock are reported.

  8. Topological Thouless pumping of ultracold fermions

    Science.gov (United States)

    Nakajima, Shuta; Tomita, Takafumi; Taie, Shintaro; Ichinose, Tomohiro; Ozawa, Hideki; Wang, Lei; Troyer, Matthias; Takahashi, Yoshiro

    2016-04-01

    An electron gas in a one-dimensional periodic potential can be transported even in the absence of a voltage bias if the potential is slowly and periodically modulated in time. Remarkably, the transferred charge per cycle is sensitive only to the topology of the path in parameter space. Although this so-called Thouless charge pump was first proposed more than thirty years ago, it has not yet been realized. Here we report the demonstration of topological Thouless pumping using ultracold fermionic atoms in a dynamically controlled optical superlattice. We observe a shift of the atomic cloud as a result of pumping, and extract the topological invariance of the pumping process from this shift. We demonstrate the topological nature of the Thouless pump by varying the topology of the pumping path and verify that the topological pump indeed works in the quantum regime by varying the speed and temperature.

  9. Nanoampere pumping of Cooper pairs

    OpenAIRE

    Vartiainen, Juha J.; Möttönen, Mikko; Pekola, Jukka P.; Kemppinen, Antti

    2007-01-01

    The authors have employed a tunable Cooper-pair transistor, the sluice, with radio frequency control to pump current over a resistive circuit. They find that the charge transferred per pumping cycle can be controlled with the resolution of a single Cooper pair up to hundreds of pairs. The achieved nanoampere current features more than an order of magnitude improvement over the previously reported results and it is close to the theoretical maximum value for the measured sample.

  10. Nanoampere pumping of Cooper pairs

    OpenAIRE

    Vartiainen, Juha J.; Mottonen, Mikko; Pekola, Jukka; Kemppinen, Antti

    2006-01-01

    We have employed a tunable Cooper-pair transistor, the sluice, with radio frequency control to pump current over a resistive circuit. We find that the charge transferred per pumping cycle can be controlled with the resolution of a single Cooper-pair up to hundreds of pairs. The achieved nanoampere current features more than an order of magnitude improvement over the previously reported results and it is close to the theoretical maximum value for the measured sample.

  11. Electrohydrodynamic inductively pumped heat pipe

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, A.S.

    1981-01-19

    The self-priming voltage controllable electrohydrodynamic inductively pumped heat pipe of the present invention greatly improves the maximum thermal throughout of heat pipes in low and medium temperature applications calling for the use of dielectric working fluids. An applied traveling potential wave induces a traveling wave of electrical charge in selected phase relation in the liquid phase of the dielectric working fluid providing an electrical traction which pumps the working fluid from the condensor to the evaporator.

  12. Quantum pumping in graphene nanoribbons at resonant transmission

    OpenAIRE

    Grichuk, E.; Manykin, E.

    2010-01-01

    Adiabatic quantum charge pumping in graphene nanoribbon double barrier structures with armchair and zigzag edges in the resonant transmission regime is analyzed. Using recursive Green's function method we numerically calculate the pumped charge for pumping contours encircling a resonance. We find that for armchair ribbons the whole resonance line contributes to the pumping of a single electron (ignoring double spin degeneracy) per cycle through the device. The case of zigzag ribbons is more i...

  13. On the possibility of gamma-laser pumping occurring at a charged particle counter motion and in density-modulated electron beams by a high frequency intensive radiation

    International Nuclear Information System (INIS)

    The given report deals with the problem of motion and radiation of relativistic electron in a field of opposite plane density-modulated relativistic electron beam. Physical essence of high-frequency intensive radiation origin could be explained, first by the additional Lorentz reduction of the electron beam modulation period (modulation period Λ in a laboratory co-ordinate system reduces by a factor γ as compared with the modulation period in a beam co-ordinate system) and, secondly, a simultaneous γ-fold increase of transverse components of relativistic electrons of the beam electric and magnetic fields. Such a moving modulated electron beam can be regarded as a dynamic micro-ondulator. Unlike static micro-ondulators we can observe here one more positive moment along with a small period Λ = Λ'/γ, i.e. the electric and magnetic fields in a transverse direction are changed according to the law of exp(-2πx/Λ'). It means that charged particle interaction with a dynamic micro-ondulator will be effective in a wide range of transverse distances, i.e., to get an intensive short wave radiation one can use charged particle beams with rather large apertures which leads to an additional radiation intensity increase. A discussion is given showing that the proposed dynamic modulator possesses some essential merits. A detailed calculation is presented. (author)

  14. Dilatation effect of ''quantum clocks''

    International Nuclear Information System (INIS)

    The relativistic dilatation effect of the life-time of unstable microparticles combined with quantum symmetry of their description results in the ''quantum-dilatation'' dilemma. It is due to the classical character of the relativity theory which here reveals itself in the classical world-line of the clock necessary in order to deduce the dilatation effect from the Lorentz transformation. It is shown how to solve this dilemma, basing on the relation continuum C4. Two types of measurements of time intervals, the direct and indirect one, are analyzed. The former type corresponds to the external space-time continuum, where any direct measurement takes place, and the latter, to the internal relation continuum C4, where the internal structures of isolated micro-systems are sunk. (author)

  15. Circadian clocks are designed optimally

    CERN Document Server

    Hasegawa, Yoshihiko

    2014-01-01

    Circadian rhythms are acquired through evolution to increase the chances for survival by synchronizing to the daylight cycle. Reliable synchronization is realized through two trade-off properties: regularity to keep time precisely, and entrainability to synchronize the internal time with daylight. Since both properties have been tuned through natural selection, their adaptation can be formalized in the framework of mathematical optimization. By using a succinct model, we found that simultaneous optimization of regularity and entrainability entails inherent features of the circadian mechanism irrespective of model details. At the behavioral level we discovered the existence of a dead zone, a time during which light pulses neither advance nor delay the clock. At the molecular level we demonstrate the role-sharing of two light inputs, phase advance and delay, as is well observed in mammals. We also reproduce the results of phase-controlling experiments and predict molecular elements responsible for the clockwork...

  16. Thermally Actuated Hydraulic Pumps

    Science.gov (United States)

    Jones, Jack; Ross, Ronald; Chao, Yi

    2008-01-01

    vessels. Heretofore, electrically actuated hydraulic pumps have been used for this purpose. By eliminating the demand for electrical energy for pumping, the use of the thermally actuated hydraulic pumps could prolong the intervals between battery charges, thus making it possible to greatly increase the durations of undersea exploratory missions.

  17. Chemically driven electron tunnelling pumps

    CERN Document Server

    Goychuk, I

    2006-01-01

    The simplest mechanism for molecular electron pumps is discussed which is based on nonadiabatic electron tunnelling and nonequilibrium conformational fluctuations. Such fluctuations can be induced, e.g. by random binding of negatively charged ATP molecules to the electron-transferring molecular complex, their subsequent hydrolysis and the products dissociation. The pumping rate can be controlled by the ATP concentration in solution. Depending on the model parameters there may exist a critical ATP concentration for the pump to function. Alternatively, nonequilibrium fluctuations can be induced by externally applied stochastic electric fields. For realistically chosen parameters, the mechanism is shown to be robust and highly efficient.

  18. Iterative quantum algorithm for distributed clock synchronization

    International Nuclear Information System (INIS)

    Clock synchronization is a well-studied problem with many practical and scientific applications. We propose an arbitrary accuracy iterative quantum algorithm for distributed clock synchronization using only three qubits. The n bits of the time difference Δ between two spatially separated clocks can be deterministically extracted by communicating only O(n) messages and executing the quantum iteration process n times based on the classical feedback and measurement operations. Finally, we also give the algorithm using only two qubits and discuss the success probability of the algorithm

  19. Using Atomic Clocks to Detect Gravitational Waves

    CERN Document Server

    Loeb, Abraham

    2015-01-01

    Atomic clocks have recently reached a fractional timing precision of $<10^{-18}$. We point out that an array of atomic clocks, distributed along the Earth's orbit around the Sun, will have the sensitivity needed to detect the time dilation effect of mHz gravitational waves (GWs), such as those emitted by supermassive black hole binaries at cosmological distances. Simultaneous measurement of clock-rates at different phases of a passing GW provides an attractive alternative to the interferometric detection of temporal variations in distance between test masses separated by less than a GW wavelength, currently envisioned for the eLISA mission.

  20. Jet Pump

    OpenAIRE

    Wærp, Nils Petter

    2010-01-01

    The aim of this project is to investigate how an artificial lift method in the oil industry works,and to compare its performance with other pump systems. Jet pumps are initially used in the oil industry for artificial lift and thus in order to do so one needs a good understanding of themechanics to predict the jet pumps’ performance. The project will begin with a review of how the jet pump operates, aiming to give the reader an insight and overview into the field of an artificial lift method....

  1. The circadian clock in cancer development and therapy

    Science.gov (United States)

    Most aspects of mammalian function display circadian rhythms driven by an endogenous clock. The circadian clock is operated by genes and comprises a central clock in the brain that responds to environmental cues and controls subordinate clocks in peripheral tissues via circadian output pathways. The...

  2. Transcripts from the Circadian Clock: Telling Time and Season

    NARCIS (Netherlands)

    K. Brand (Karl)

    2011-01-01

    textabstractWe all know it when we wake mere moments before an alarm clock is scheduled to wake us: our body clock made the alarm clock redundant. This phenomenon is driven by an endogenous timer known as the biological, or circadian clock. Each revolution of the Earth about its own axis produces pe

  3. The Chemical and Educational Appeal of the Orange Juice Clock

    Science.gov (United States)

    Kelter, Paul B.; Carr, James D.; Johnson, Tanya; Mauricio Castro-Acuña, Carlos

    1996-12-01

    The Orange Juice Clock, in which a galvanic cell is made from the combination of a magnesium strip, a copper strip, and juice in a beaker, has been a popular classroom, conference, and workshop demonstration for nearly 10 years. It is widely enjoyed because it shows visually how chemistry - or more precisely, electrochemistry - is responsible for the very common phenomenon of a clock ticking. The chemistry of the process can also be understood on a variety of levels, from middle school (simple electron flow in a circuit, Ohm's law) and high school (reduction/oxidation and standard cell potentials) to first-year college (cell potential at nonideal conditions) and graduate school courses (overpotential and charge transfer across interfaces.) The discussion that follows considers the recent history, chemistry, and educational uses of the demonstration. The History The demonstration was devised by one of us (PK) in 1986, after reading an activity in Hubert Alyea's 1947 compendium of chemical demonstrations from this Journal (1). In that activity, Alyea hooked a magnesium strip to the negative battery terminal of an electric bell and hooked a copper strip to the positive terminal. He placed the loose ends of the strips into a 1M 2SO4 solution and the bell rang. After trying the demonstration, it seemed to make sense to modify the electrolyte to orange juice because it is safe, readily available, and would be a mixture in which the magnesium would oxidize more slowly than in sulfuric acid. Further, a clock was substituted for the bell because a clock is easier on the ears than a bell. A video of the orange-juice clock setup is given as Figure 1. Figure 1.The orange juice clock set up. Video of orange juice clock was filmed and editted by Jerry Jacobson at the University of Wisconsin - Madison. The apparatus was presented in 1987 as part of a teacher workshop led by Irwin Talesnick, then of Queen's University in Canada. Talesnick, whose distinguished career has been

  4. Electromagnetic pump

    International Nuclear Information System (INIS)

    The present invention provides an electromagnetic pump suitable to a recycling pump for liquid sodium as coolants of an FBR type reactor. Namely, a stator module of the electromagnetic pump of the present invention comprises a plurality of outer laminate iron core units and outer stator modules stacked alternately in the axial direction. With such a constitution, even a long electromagnetic pump having a large number of outer stator coils can be manufactured without damaging electric insulation of the outer stator coils. In addition, the inner circumferential surface of the outer laminate iron cores is urged and brought into contact with the outer circumferential surface of the outer duct by an elastic material. With such a constitution, Joule loss heat generated in the outer stator coils and internal heat generated in the outer laminate iron cores can be released to an electroconductive fluid flowing the inner circumference of the outer duct by way of the outer duct. (I.S.)

  5. Pump impeller

    International Nuclear Information System (INIS)

    A mixed-flow pump impeller, which may be used, for example, as a primary pump for circulating sodium as the primary coolant in a fast nuclear reactor, is described which comprises an impeller with evenly-spaced blades. Some of the blades, which are symmetrically disposed around the axis of rotation of the impeller, extend beyond the ends of the other blades towards the suction side of the pump to form an inducer. The channels defined between the extensions of the extended blades follow helical paths parallel to the axis of rotation. The leading edges of the unextended blades are interposed between the extended blades in the region of divergence of flow from the axis of rotation. The provision of the inducer reduces the risk of cavitation in the pump, which could cause rapid wear of the impeller. A shroud may be provided for the unextended blades. (author)

  6. Electrokinetic pump

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Kamlesh D. (Dublin, CA)

    2007-11-20

    A method for altering the surface properties of a particle bed. In application, the method pertains particularly to an electrokinetic pump configuration where nanoparticles are bonded to the surface of the stationary phase to alter the surface properties of the stationary phase including the surface area and/or the zeta potential and thus improve the efficiency and operating range of these pumps. By functionalizing the nanoparticles to change the zeta potential the electrokinetic pump is rendered capable of operating with working fluids having pH values that can range from 2-10 generally and acidic working fluids in particular. For applications in which the pump is intended to handle highly acidic solutions latex nanoparticles that are quaternary amine functionalized can be used.

  7. Design and implementation of fast bipolar clock drivers for CCD imaging systems in space applications

    Science.gov (United States)

    Jayarajan, Jayesh; Kumar, Nishant; Verma, Amarnath; Thaker, Ramkrishna

    2016-05-01

    Drive electronics for generating fast, bipolar clocks, which can drive capacitive loads of the order of 5-10nF are indispensable for present day Charge Coupled Devices (CCDs). Design of these high speed bipolar clocks is challenging because of the capacitive loads that have to be driven and a strict constraint on the rise and fall times. Designing drive electronics circuits for space applications becomes even more challenging due to limited number of available discrete devices, which can survive in the harsh radiation prone space environment. This paper presents the design, simulations and test results of a set of such high speed, bipolar clock drivers. The design has been tested under a thermal cycle of -15 deg C to +55 deg C under vacuum conditions and has been designed using radiation hardened components. The test results show that the design meets the stringent rise/fall time requirements of 50+/-10ns for Multiple Vertical CCD (VCCD) clocks and 20+/-5ns for Horizontal CCD (HCCD) clocks with sufficient design margins across full temperature range, with a pixel readout rate of 6.6MHz. The full design has been realized in flexi-rigid PCB with package volume of 140x160x50 mm3.

  8. Simulation for signal charge transfer of charge coupled devices

    Institute of Scientific and Technical Information of China (English)

    Wang Zujun; Liu Yinong; Chen Wei; Tang Benqi; Xiao Zhigang; Huang Shaoyan; Liu Minbo; Zhang Yong

    2009-01-01

    Physical device models and numerical processing methods are presented to simulate a linear buried channel charge coupled devices (CCDs). The dynamic transfer process of CCD is carried out by a three-phase clock pulse driver. By using the semiconductor device simulation software MEDICI, dynamic transfer pictures of signal charges cells, electron concentration and electrostatic potential are presented. The key parameters of CCD such as charge transfer efficiency (CTE) and dark electrons are numerically simulated. The simulation results agree with the theoretic and experimental results.

  9. Draper Clock-Synchronization Protocol in SAL

    Data.gov (United States)

    National Aeronautics and Space Administration — In 1973, Daly, Hpokins, and McKenna (from Draper Lab.) presented a fault-tolerant digital clocking system at the FTCS conference. This is probably one of the first...

  10. The Mechanics of Mechanical Watches and Clocks

    CERN Document Server

    Du, Ruxu

    2013-01-01

    "The Mechanics of Mechanical Watches and Clocks" presents historical views and mathematical models of mechanical watches and clocks. Although now over six hundred years old, mechanical watches and clocks are still popular luxury items that fascinate many people around the world. However few have examined the theory of how they work as presented in this book. The illustrations and computer animations are unique and have never been published before. It will be of significant interest to researchers in mechanical engineering, watchmakers and clockmakers, as well as people who have an engineering background and are interested in mechanical watches and clocks. It will also inspire people in other fields of science and technology, such as mechanical engineering and electronics engineering, to advance their designs. Professor Ruxu Du works at the Chinese University of Hong Kong, China. Assistant Professor Longhan Xie works at the South China University of Technology, China.

  11. Entrainment of the Neurospora circadian clock

    NARCIS (Netherlands)

    Merrow, M; Boesl, C; Ricken, J; Messerschmitt, M; Goedel, M; Roenneberg, T

    2006-01-01

    Neurospora crassa has been systematically investigated for circadian entrainment behavior. Many aspects of synchronization can be investigated in this simple, cellular system, ranging from systematic entrainment and drivenness to masking. Clock gene expression during entrainment and entrainment with

  12. Micro Mercury Ion Clock (MMIC) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Demonstrate micro clock based on trapped Hg ions with more than 10x size reduction and power; Fractional frequency stability at parts per 1014 level, adequate for...

  13. High-Accuracy Microwave Atomic Clock via Magic Optical Lattice

    OpenAIRE

    Zhou, Xiaoji; Chen, Xuzong; Chen, Jingbiao

    2005-01-01

    A microwave atomic clock scheme based on Rb and Cs atoms trapped in optical lattice with magic wavelength for clock transition is proposed. The ac Stark shift of clock transition due to trapping laser can be canceled at some specific laser wavelengths. Comparing with in fountain clock, the cavity related shifts, the collision shift, and the Doppler effect are eliminated or suppressed dramatically in atomic clock when the magic optical lattice is exploited. By carefully analyzing various sourc...

  14. Automated Synthesis of Skew-Based Clock Distribution Networks

    OpenAIRE

    José Luis Neves; Eby G. Friedman

    1998-01-01

    In this paper a top-down methodology is presented for synthesizing clock distribution networks based on application-dependent localized clock skew. The methodology is divided into four phases: 1) determination of an optimal clock skew schedule for improving circuit performance and reliability; 2) design of the topology of the clock tree based on the circuit hierarchy and minimum clock path delays; 3) design of circuit structures to implement the delay values associated with the branches of th...

  15. Working around the clock: circadian rhythms and skeletal muscle

    OpenAIRE

    ZHANG, XIPING; Dube, Thomas J.; Esser, Karyn A.

    2009-01-01

    The study of the circadian molecular clock in skeletal muscle is in the very early stages. Initial research has demonstrated the presence of the molecular clock in skeletal muscle and that skeletal muscle of a clock-compromised mouse, Clock mutant, exhibits significant disruption in normal expression of many genes required for adult muscle structure and metabolism. In light of the growing association between the molecular clock, metabolism, and metabolic disease, it will also be important to ...

  16. Clock genes, hair growth and aging

    OpenAIRE

    Geyfman, Mikhail; Andersen, Bogi

    2010-01-01

    Hair follicles undergo continuous cycles of growth, involution and rest. This process, referred to as the hair growth cycle, has a periodicity of weeks to months. At the same time, skin and hair follicles harbor a functional circadian clock that regulates gene expression with a periodicity of approximately twenty four hours. In our recent study we found that circadian clock genes play a role in regulation of the hair growth cycle during synchronized hair follicle cycling, uncovering an unexpe...

  17. Expression of Clock Proteins in Developing Tooth

    OpenAIRE

    Zheng, Li; Papagerakis, Silvana; Schnell, Santiago D.; Hoogerwerf, Willemijntje A; Papagerakis, Petros

    2010-01-01

    Morphological and functional changes during ameloblast and odontoblast differentiation suggest that enamel and dentin formation is under circadian control. Circadian rhythms are endogenous self-sustained oscillations with periods of 24 hours that control diverse physiological and metabolic processes. Mammalian clock genes play a key role in synchronizing circadian functions in many organs. However, close to nothing is known on clock genes expression during tooth development. In this work, we ...

  18. Circadian Clock Proteins in Mood Regulation

    OpenAIRE

    Partonen, Timo

    2015-01-01

    Mood regulation is known to be affected by the change of seasons. Recent research findings have suggested that mood regulation may be influenced by the function of circadian clocks. In addition, the activity of brown adipocytes has been hypothesized to contribute to mood regulation. Here, the overarching link to mood disorders might be the circadian clock protein nuclear receptor subfamily 1, group D, member 1.

  19. Circadian clock proteins in mood regulation

    Directory of Open Access Journals (Sweden)

    Timo ePartonen

    2015-01-01

    Full Text Available Mood regulation is known to be affected by the change of seasons. Recent research findings have suggested that mood regulation may be influenced by the function of circadian clocks. In addition, the activity of brown adipocytes has been hypothesized to contribute to mood regulation. Here, the overarching link to mood disorders might be the circadian clock protein NR1D1 (nuclear receptor subfamily 1, group D, member 1.

  20. Reduced Kalman Filters for Clock Ensembles

    Science.gov (United States)

    Greenhall, Charles A.

    2011-01-01

    This paper summarizes the author's work ontimescales based on Kalman filters that act upon the clock comparisons. The natural Kalman timescale algorithm tends to optimize long-term timescale stability at the expense of short-term stability. By subjecting each post-measurement error covariance matrix to a non-transparent reduction operation, one obtains corrected clocks with improved short-term stability and little sacrifice of long-term stability.

  1. Avian Circadian Organization: A Chorus of Clocks

    OpenAIRE

    Cassone, Vincent M.

    2013-01-01

    In birds, biological clock function pervades all aspects of biology, controlling daily changes in sleep: wake, visual function, song, migratory patterns and orientation, as well as seasonal patterns of reproduction, song and migration. The molecular bases for circadian clocks are highly conserved, and it is likely the avian molecular mechanisms are similar to those expressed in mammals, including humans. The central pacemakers in the avian pineal gland, retinae and SCN dynamically interact to...

  2. Pumping potential wells

    Science.gov (United States)

    Hershkowitz, N.; Forest, C.; Wang, E. Y.; Intrator, T.

    1987-01-01

    Nonmonotonic plasma potential structures are a common feature of many double layers and sheaths. Steady state plasma potential wells separating regions having different plasma potentials are often found in laboratory experiments. In order to exist, such structures all must find a solution to a common problem. Ions created by charge exchange or ionization in the region of the potential well are electrostatically confined and tend to accumulate and fill up the potential well. The increase in positive charge should eliminate the well. Nevertheless, steady state structures are found in which the wells do not fill up. This means that it is important to take into account processes which 'pump' ions from the well. As examples of ion pumping of plasma wells, potential dips in front of a positively biased electro collecting anode in a relatively cold, low density multidipole plasma is considered. Pumping is provided by ion leaks from the edges of the potential dip or by oscillating the applied potential. In the former case the two dimensional character of the problem is shown to be important.

  3. A Novel High Step-up Boost Converter with Charge Pump Capacitor%一种带有泵升电容的新型高增益升压直流变换器

    Institute of Scientific and Technical Information of China (English)

    屈克庆; 梁晓霞; 赵晋斌; 李芬

    2014-01-01

    为了满足分布式发电系统中必须把太阳能、燃料电池和蓄电池输入的低压直流转换为高压的要求,在传统型升压直流变换器的基础上,提出了一种基于双电感和泵升电容的新型拓扑结构。该拓扑结构利用电感和电容的并联充电、串联放电特性,较好地实现了低占空比条件下高电压增益的目标。最后,分析了该拓扑结构在3种不同电感条件下的工作原理,并通过仿真验证了上述理论分析的正确性。%In order to meet the demands of the distributed generation system for converting low direct current (DC) input voltage from solar,fuel cell and battery to high output voltage,a novel Boost converter topology with a charge pump capacitor and double inductors based on the traditional Boost converter is proposed.The proposed converter realizes the high voltage gain under low duty cycle by charging through the inductors and capacitor in parallel and discharging through the inductors and capacitor in series.The operation principle and steady-state analysis are provided in three different inductance conditions. Finally,the results of the analysis are verified by simulation.

  4. Fermi liquid theory of resonant spin pumping

    OpenAIRE

    Moca, C. P.; Alex, A.; Shnirman, A.; Zarand, G.

    2013-01-01

    We study resonant all-electric adiabatic spin pumping through a quantum dot with two nearby levels by using a Fermi liquid approach in the strongly interacting regime, combined with a projective numerical renormalization group (NRG) theory. Due to spin-orbit coupling, a strong spin pumping resonance emerges at every charging transition, which allows for the transfer of a spin $~ \\hbar/2$ through the device in a single pumping cycle. Depending on the precise geometry of the device, controlled ...

  5. Reliability-Growth of Triplex Drilling Pump

    Institute of Scientific and Technical Information of China (English)

    Hou Yu; ZhaoZhong

    1996-01-01

    @@ Introduction to triplex pump The triplex pump widely used in oilfields is composed of power end assembly, fluid end assembly, piston-liner spraying system, lubrication system and charging system.The pump delivers mud into oil well. Through nozzles of drilling bit, the mud inside the drilling shaft comes to the annular space between drilling shaft and casing string and then returns to surface.

  6. A highly miniaturized vacuum package for a trapped ion atomic clock

    Science.gov (United States)

    Schwindt, Peter D. D.; Jau, Yuan-Yu; Partner, Heather; Casias, Adrian; Wagner, Adrian R.; Moorman, Matthew; Manginell, Ronald P.; Kellogg, James R.; Prestage, John D.

    2016-05-01

    We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm3 in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of 171Y b+. The fractional frequency stability of the clock was measured to be 2 × 10-11/τ1/2.

  7. Interaction of circadian clock proteins PER2 and CRY with BMAL1 and CLOCK

    Directory of Open Access Journals (Sweden)

    Bordon Alain

    2008-04-01

    Full Text Available Abstract Background Circadian oscillation of clock-controlled gene expression is mainly regulated at the transcriptional level. Heterodimers of CLOCK and BMAL1 act as activators of target gene transcription; however, interactions of PER and CRY proteins with the heterodimer abolish its transcriptional activation capacity. PER and CRY are therefore referred to as negative regulators of the circadian clock. To further elucidate the mechanism how positive and negative components of the clock interplay, we characterized the interactions of PER2, CRY1 and CRY2 with BMAL1 and CLOCK using a mammalian two-hybrid system and co-immunoprecipitation assays. Results Both PER2 and the CRY proteins were found to interact with BMAL1 whereas only PER2 interacts with CLOCK. CRY proteins seem to have a higher affinity to BMAL1 than PER2. Moreover, we provide evidence that PER2, CRY1 and CRY2 bind to different domains in the BMAL1 protein. Conclusion The regulators of clock-controlled transcription PER2, CRY1 and CRY2 differ in their capacity to interact with each single component of the BMAL1-CLOCK heterodimer and, in the case of BMAL1, also in their interaction sites. Our data supports the hypothesis that CRY proteins, especially CRY1, are stronger repressors than PER proteins.

  8. Insulin pumps.

    Science.gov (United States)

    Pickup, J

    2011-02-01

    The last year has seen a continued uptake of insulin pump therapy in most countries. The USA is still a leader in pump use, with probably some 40% of type 1 diabetic patients on continuous subcutaneous insulin infusion (CSII), but the large variation in usage within Europe remains, with relatively high use (> 15%) in, for example, Norway, Austria, Germany and Sweden and low use (companies or funding from national health services, the availability of sufficient diabetes nurse educators and dietitians trained in pump procedures, and clear referral pathways for the pump candidate from general practitioner or general hospital to specialist pump centre. There are now several comprehensive national guidelines on CSII use (see ATTD Yearbook 2009) but more work needs to be done in unifying uptake and ensuring all those who can benefit do so. Technology developments recently include increasing use of pumps with continuous glucose monitoring (CGM) connectivity (see elsewhere in this volume) and the emergence of numerous manufacturers developing so-called 'patch pumps', often for the type 2 diabetes market. Interestingly, the evidence base for CSII in this group is not well established, and for this reason the selected papers on CSII in this section include several in this area. The use of CSII in diabetic pregnancy is a long-established practice, in spite of the lack of evidence that it is superior to multiple daily injections (MDI), and few randomised controlled trials have been done in recent years. Several papers in this field this year continue the debate about the usefulness of CSII in diabetic pregnancy and are reviewed here. It is pleasing to see more research on the psychosocial aspects of CSII during the year, both from the point of view of how psychological beliefs influence outcomes on CSII (is there a type of patient who does particularly well or poorly on CSII?) and how CSII affects psychological factors like mood, behaviour and quality of life. Quality of

  9. DIFFUSION PUMP

    Science.gov (United States)

    Levenson, L.

    1963-09-01

    A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

  10. Microwave Atomic Clock in the Optical Lattice with Specific Frequency

    International Nuclear Information System (INIS)

    A scheme for a microwave atomic clock is proposed for Cs or Rb atoms trapped in a blue detuned optical lattice. The ac Stark shift of the clock transition due to a trapping laser is calculated. We analyze it at some specific laser wavelength. Compared with the case of the fountain clock, the cavity related shifts, the collision shift and the Doppler effect are eliminated or suppressed dramatically in an atomic lattice clock. By analyzing various sources of clock uncertainty, a microwave atomic lattice clock with a high accuracy and small volume is feasible

  11. Dual-wavelength active optical clock

    CERN Document Server

    Xu, Zhichao; Zhuang, Wei; Chen, Jingbiao

    2014-01-01

    We experimentally realize the dual-wavelength active optical clock for the first time. As the Cs cell temperature is kept between 118 $^{\\circ }C$ and 144 $^{\\circ }C$, both the 1359 nm and the 1470 nm stimulated emission output of Cs four-level active optical clock are detected. The 1470 nm output linewidth of each experimental setup of Cs four-level active optical clock is measured to be 590 Hz with the main cavity length unstabilized. To stabilize the cavity length of active optical clock, the experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical clock is proposed, where 633 nm and 1359 nm stimulated emission is working at good-cavity and bad-cavity regime respectively. The cavity length is stabilized by locking the 633 nm output frequency to a super-cavity with the Pound-Drever-Hall (PDH) technique. The frequency stability of 1359 nm bad-cavity stimulated emission output is then expected to be further improved by at least 1 order of magnitude than the 633 nm PDH system d...

  12. Circadian Clock Control of Liver Metabolic Functions.

    Science.gov (United States)

    Reinke, Hans; Asher, Gad

    2016-03-01

    The circadian clock is an endogenous biological timekeeping system that synchronizes physiology and behavior to day/night cycles. A wide variety of processes throughout the entire gastrointestinal tract and notably the liver appear to be under circadian control. These include various metabolic functions such as nutrient uptake, processing, and detoxification, which align organ function to cycle with nutrient supply and demand. Remarkably, genetic or environmental disruption of the circadian clock can cause metabolic diseases or exacerbate pathological states. In addition, modern lifestyles force more and more people worldwide into asynchrony between the external time and their circadian clock, resulting in a constant state of social jetlag. Recent evidence indicates that interactions between altered energy metabolism and disruptions in the circadian clock create a downward spiral that can lead to diabetes and other metabolic diseases. In this review, we provide an overview of rhythmic processes in the liver and highlight the functions of circadian clock genes under physiological and pathological conditions; we focus on their roles in regulation of hepatic glucose as well as lipid and bile acid metabolism and detoxification and their potential effects on the development of fatty liver and nonalcoholic steatohepatitis. PMID:26657326

  13. Direct laser cooling Al+ ions optical clocks

    CERN Document Server

    Zhang, J; Luo, J; Lu, Z H

    2016-01-01

    Al$^+$ ions optical clock is a very promising optical frequency standard candidate due to its extremely small blackbody radiation shift. It has been successfully demonstrated with indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of Al$^+$ ions optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al$^+$ ions traps are utilized. The first trap is used to trap a large number of Al$^+$ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al$^+$ ions to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167 nm laser. The expected clock laser stability can reach $9.0\\times10^{-17}/\\sqrt{\\tau}$. For the second trap, in addition to 167 nm laser Doppler cooling, a second stage pulsed ...

  14. Status of the atomic fountain clock at the National Research Council of Canada

    Science.gov (United States)

    Beattie, S.; Alcock, J.; Jian, B.; Gertsvolf, M.; Bernard, J.

    2016-06-01

    Despite the rapid advances in optical frequency standards, caesium fountain clocks retain a critical role as the most accurate primary frequency standards available. At the National Research Council Canada, we are working to develop a second generation caesium fountain clock. Work is currently underway to improve several systems of FCs1, such as the laser system and microwave local oscillator, which will be incorporated into its refurbished version, FCs2. In addition, we have added an optical pumping stage which has increased the detected atom number by over a factor of six. In collaboration with the National Physical Laboratory (NPL), we are planning on replacing the physics package of FCs1. We will report on several recent improvements to FCs1, along with our progress in the development of FCs2.

  15. Neon as a Buffer Gas for a Mercury-Ion Clock

    Science.gov (United States)

    Prestage, John; Chung, Sang

    2008-01-01

    A developmental miniature mercury-ion clock has stability comparable to that of a hydrogen-maser clock. The ion-handling components are housed in a sealed vacuum tube, wherein a getter pump is used to maintain the partial vacuum, and the evacuated tube is backfilled with mercury vapor in a buffer gas. Neon was determined to be the best choice for the buffer gas: The pressure-induced frequency pulling by neon was found to be only about two-fifths of that of helium. Furthermore, because neon diffuses through solids much more slowly than does helium, the operational lifetime of a tube backfilled with neon could be considerably longer than that of a tube backfilled with helium.

  16. Loading a fountain clock with an enhanced low-velocity intense source of atoms

    Science.gov (United States)

    Dobrev, G.; Gerginov, V.; Weyers, S.

    2016-04-01

    We present experimental work for improved atom loading in the optical molasses of a cesium fountain clock, employing a low-velocity intense source of atoms [Lu et al., Phys. Rev. Lett 77, 3331 (1996), 10.1103/PhysRevLett.77.3331], which we modify by adding a dark-state pump laser. With this modification the atom source has a mean flux of 4 ×108 atoms/s at a mean atom velocity of 8.6 m/s. Compared to fountain operation using background gas loading, we achieve a significant increase of the loaded and detected atom number by a factor of 40. Operating the fountain clock with a total number of detected atoms Nat=2.9 ×106 in the quantum projection noise-limited regime, a frequency instability σy(1 s ) =2.7 ×10-14 is demonstrated.

  17. Loading of a fountain clock with an enhanced Low-Velocity Intense Source of atoms

    CERN Document Server

    Dobrev, Georgi; Weyers, Stefan

    2016-01-01

    We present experimental work for improved atom loading in the optical molasses of a caesium fountain clock, employing a low-velocity intense source of atoms (LVIS) [Lu et al., Phys. Rev. Lett. 77, 3331 (1996)], which we modified by adding a "dark" state pump laser. With this modification the atom source has a mean flux of $4 \\times 10^{8}$ atoms/s at a mean atom velocity of $8.6$ m/s. Compared to fountain operation using background gas loading, we achieved a significant increase of the loaded and detected atom number by a factor of 40. Operating the fountain clock with a total number of detected atoms $N_{\\mathrm{at}}=2.9 \\times 10^6$ in the quantum projection noise-limited regime, a frequency instability $\\sigma_y\\left(1\\text{s}\\right)=2.7 \\times 10^{-14}$ was demonstrated.

  18. Whole blood pumping with a microthrottle pump

    OpenAIRE

    Davies, M J; Johnston, I. D.; Tan, C. K. L.; Tracey, M. C.

    2010-01-01

    We have previously reported that microthrottle pumps (MTPs) display the capacity to pump solid phase suspensions such as polystyrene beads which prove challenging to most microfluidic pumps. In this paper we report employing a linear microthrottle pump (LMTP) to pump whole, undiluted, anticoagulated, human venous blood at 200 μl min−1 with minimal erythrocyte lysis and no observed pump blockage. LMTPs are particularly well suited to particle suspension transport by virtue of their relatively ...

  19. Susceptibility of Redundant Versus Singular Clock Domains Implemented in SRAM-Based FPGA TMR Designs

    Science.gov (United States)

    Berg, Melanie D.; LaBel, Kenneth A.; Pellish, Jonathan

    2016-01-01

    We present the challenges that arise when using redundant clock domains due to their clock-skew. Radiation data show that a singular clock domain (DTMR) provides an improved TMR methodology for SRAM-based FPGAs over redundant clocks.

  20. Quantum clock: A critical discussion on spacetime

    Science.gov (United States)

    Burderi, Luciano; Di Salvo, Tiziana; Iaria, Rosario

    2016-03-01

    We critically discuss the measure of very short time intervals. By means of a Gedankenexperiment, we describe an ideal clock based on the occurrence of completely random events. Many previous thought experiments have suggested fundamental Planck-scale limits on measurements of distance and time. Here we present a new type of thought experiment, based on a different type of clock, that provide further support for the existence of such limits. We show that the minimum time interval Δ t that this clock can measure scales as the inverse of its size Δ r . This implies an uncertainty relation between space and time: Δ r Δ t >G ℏ/c4, where G , ℏ, and c are the gravitational constant, the reduced Planck constant, and the speed of light, respectively. We outline and briefly discuss the implications of this uncertainty conjecture.

  1. Which came first, spacetime or clocks?

    International Nuclear Information System (INIS)

    Emergent quantum mechanics seeks a deeper level theory, anticipating that such a theory will provide a clearer picture of the relation between the quantum and classical worlds. In this work we show that the quantum-classical divide is a manifestation of the transition from Newton's absolute time to relativity's path-dependent time. The prior theory in this case is that particles are intrinsic clocks. The emergence of separate classical and quantum behaviour is seen by considering different continuum limits in a single digital clock model. A continuum limit that constructs a continuous worldline provides a simple basis for Minkowski spacetime. An alternative limit in which the clock itself contains boost information leads to the Dirac equation.

  2. Quantum clock: A critical discussion on spacetime

    CERN Document Server

    Burderi, Luciano; Iaria, Rosario

    2016-01-01

    We critically discuss the measure of very short time intervals. By means of a Gedankenexperiment, we describe an ideal clock based on the occurrence of completely random events. Many previous thought experiments have suggested fundamental Planck-scale limits on measurements of distance and time. Here we present a new type of thought experiment, based on a different type of clock, that provide further support for the existence of such limits. We show that the minimum time interval $\\Delta t$ that this clock can measure scales as the inverse of its size $\\Delta r$. This implies an uncertainty relation between space and time: $\\Delta r$ $\\Delta t$ $> G \\hbar / c^4$; where G, $\\hbar$ and c are the gravitational constant, the reduced Planck constant, and the speed of light, respectively. We outline and briefly discuss the implications of this uncertainty conjecture.

  3. Models of the Primordial Standard Clock

    CERN Document Server

    Chen, Xingang; Wang, Yi

    2014-01-01

    Oscillating massive fields in the primordial universe can be used as Standard Clocks. The ticks of these oscillations induce features in the density perturbations, which directly record the time evolution of the scale factor of the primordial universe, thus if detected, provide a direct evidence for the inflation scenario or the alternatives. In this paper, we construct a full inflationary model of primordial Standard Clock and study its predictions on the density perturbations. This model provides a full realization of several key features proposed previously. We compare the theoretical predictions from inflation and alternative scenarios with the Planck 2013 temperature data on Cosmic Microwave Background (CMB), and identify a statistically marginal but interesting candidate. We discuss how future CMB temperature and polarization data, non-Gaussianity analysis and Large Scale Structure data may be used to further test or constrain the Standard Clock signals.

  4. The Deep Space Atomic Clock Mission

    Science.gov (United States)

    Ely, Todd A.; Koch, Timothy; Kuang, Da; Lee, Karen; Murphy, David; Prestage, John; Tjoelker, Robert; Seubert, Jill

    2012-01-01

    The Deep Space Atomic Clock (DSAC) mission will demonstrate the space flight performance of a small, low-mass, high-stability mercury-ion atomic clock with long term stability and accuracy on par with that of the Deep Space Network. The timing stability introduced by DSAC allows for a 1-Way radiometric tracking paradigm for deep space navigation, with benefits including increased tracking via utilization of the DSN's Multiple Spacecraft Per Aperture (MSPA) capability and full ground station-spacecraft view periods, more accurate radio occultation signals, decreased single-frequency measurement noise, and the possibility for fully autonomous on-board navigation. Specific examples of navigation and radio science benefits to deep space missions are highlighted through simulations of Mars orbiter and Europa flyby missions. Additionally, this paper provides an overview of the mercury-ion trap technology behind DSAC, details of and options for the upcoming 2015/2016 space demonstration, and expected on-orbit clock performance.

  5. Using a Breast Pump

    Science.gov (United States)

    ... you can relax and not be disturbed while pumping. If you have an electric pump, find an ... otherwise irritating your nipple or breast tissue. Begin Pumping If your pump is electric or battery-powered, ...

  6. Sample-Clock Phase-Control Feedback

    Science.gov (United States)

    Quirk, Kevin J.; Gin, Jonathan W.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    To demodulate a communication signal, a receiver must recover and synchronize to the symbol timing of a received waveform. In a system that utilizes digital sampling, the fidelity of synchronization is limited by the time between the symbol boundary and closest sample time location. To reduce this error, one typically uses a sample clock in excess of the symbol rate in order to provide multiple samples per symbol, thereby lowering the error limit to a fraction of a symbol time. For systems with a large modulation bandwidth, the required sample clock rate is prohibitive due to current technological barriers and processing complexity. With precise control of the phase of the sample clock, one can sample the received signal at times arbitrarily close to the symbol boundary, thus obviating the need, from a synchronization perspective, for multiple samples per symbol. Sample-clock phase-control feedback was developed for use in the demodulation of an optical communication signal, where multi-GHz modulation bandwidths would require prohibitively large sample clock frequencies for rates in excess of the symbol rate. A custom mixedsignal (RF/digital) offset phase-locked loop circuit was developed to control the phase of the 6.4-GHz clock that samples the photon-counting detector output. The offset phase-locked loop is driven by a feedback mechanism that continuously corrects for variation in the symbol time due to motion between the transmitter and receiver as well as oscillator instability. This innovation will allow significant improvements in receiver throughput; for example, the throughput of a pulse-position modulation (PPM) with 16 slots can increase from 188 Mb/s to 1.5 Gb/s.

  7. The development of clocks into the eighteenth century

    OpenAIRE

    Dugan, David

    2004-01-01

    The advantages of clocks with escapements over water clocks, that they can be miniaturized. The superb chronometers of the seventeenth century onwards, Harrison and others. The emergence of clockmakers and precise engineering. Superb luxury goods. Simon Schaffer explains.

  8. Caring around the Clock: rounding in practice.

    Science.gov (United States)

    Hutchings, Marie

    A large acute trust in the East Midlands looked to the US to inform its implementation of hourly rounding, otherwise known as intentional rounding. A combination of transformational leadership and meaningful interactions form the basis of a new approach to rounding--Caring around the Clock. The trust piloted the concept on 10 wards with results showing a 32% reduction in call lights. The successful change in practice required an investment in staff education to equip staff with the necessary skills. The trust is currently rolling out Caring around Hourly rounding can reducethe Clock to 79 inpatient wards. PMID:23342834

  9. Dynamics of a single-atom electron pump

    OpenAIRE

    van der Heijden, J.; Tettamanzi, G. C.; Rogge, S.

    2016-01-01

    Single-electron pumps based on isolated impurity atoms have recently been experimentally demonstrated. In these devices the Coulomb potential of an atom creates a localised electron state with a large charging energy and considerable orbital level spacings, enabling robust charge capturing processes. In these single-atom pumps, the confinement potential is hardly affected by the periodic driving of the system. This is in contrast to the often used gate-defined quantum dot pumps, for which a s...

  10. Entangling the lattice clock: Towards Heisenberg-limited timekeeping

    OpenAIRE

    Weinstein, Jonathan D.; Beloy, Kyle; Derevianko, Andrei

    2009-01-01

    We present a scheme for entangling the atoms of an optical lattice to reduce the quantum projection noise of a clock measurement. The divalent clock atoms are held in a lattice at a ``magic'' wavelength that does not perturb the clock frequency -- to maintain clock accuracy -- while an open-shell J=1/2 ``head'' atom is coherently transported between lattice sites via the lattice polarization. This polarization-dependent ``Archimedes' screw'' transport at magic wavelength takes advantage of th...

  11. 47 CFR 80.865 - Radiotelephone station clock.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Radiotelephone station clock. 80.865 Section 80.865 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES... W § 80.865 Radiotelephone station clock. A clock having a face of at least 12.7 cm (5 in.)...

  12. On synchronization of clocks in general space-times

    Directory of Open Access Journals (Sweden)

    M. R. H Khajehpour

    2005-09-01

    Full Text Available   Einstein and transport synchronizations of infinitesimally spaced and distant clocks are considered in a general Riemannian space-time. It is shown that infinitesimally spaced clocks can always be synchronized. In general one can not find observers for whom distant clock are Einstein synchronized but transport synchronized observers do always exit. Whenever both procedures are possible, they are equivalent.

  13. The peripheral clock regulates human pigmentation.

    Science.gov (United States)

    Hardman, Jonathan A; Tobin, Desmond J; Haslam, Iain S; Farjo, Nilofer; Farjo, Bessam; Al-Nuaimi, Yusur; Grimaldi, Benedetto; Paus, Ralf

    2015-04-01

    Although the regulation of pigmentation is well characterized, it remains unclear whether cell-autonomous controls regulate the cyclic on-off switching of pigmentation in the hair follicle (HF). As human HFs and epidermal melanocytes express clock genes and proteins, and given that core clock genes (PER1, BMAL1) modulate human HF cycling, we investigated whether peripheral clock activity influences human HF pigmentation. We found that silencing BMAL1 or PER1 in human HFs increased HF melanin content. Furthermore, tyrosinase expression and activity, as well as TYRP1 and TYRP2 mRNA levels, gp100 protein expression, melanocyte dendricity, and the number gp100+ HF melanocytes, were all significantly increased in BMAL1 and/or PER1-silenced HFs. BMAL1 or PER1 silencing also increased epidermal melanin content, gp100 protein expression, and tyrosinase activity in human skin. These effects reflect direct modulation of melanocytes, as BMAL1 and/or PER1 silencing in isolated melanocytes increased tyrosinase activity and TYRP1/2 expression. Mechanistically, BMAL1 knockdown reduces PER1 transcription, and PER1 silencing induces phosphorylation of the master regulator of melanogenesis, microphthalmia-associated transcription factor, thus stimulating human melanogenesis and melanocyte activity in situ and in vitro. Therefore, the molecular clock operates as a cell-autonomous modulator of human pigmentation and may be targeted for future therapeutic strategies. PMID:25310406

  14. Analytic clock frequency selection for global DVFS

    NARCIS (Netherlands)

    Gerards, Marco E.T.; Hurink, Johann L.; Hölzenspies, Philip K.F.; Kuper, Jan; Smit, Gerard J.M.

    2014-01-01

    Computers can reduce their power consumption by decreasing their speed using Dynamic Voltage and Frequency Scaling (DVFS). A form of DVFS for multicore processors is global DVFS, where the voltage and clock frequency is shared among all processor cores. Because global DVFS is efficient and cheap to

  15. Circadian Clock Regulates Bone Resorption in Mice.

    Science.gov (United States)

    Xu, Cheng; Ochi, Hiroki; Fukuda, Toru; Sato, Shingo; Sunamura, Satoko; Takarada, Takeshi; Hinoi, Eiichi; Okawa, Atsushi; Takeda, Shu

    2016-07-01

    The circadian clock controls many behavioral and physiological processes beyond daily rhythms. Circadian dysfunction increases the risk of cancer, obesity, and cardiovascular and metabolic diseases. Although clinical studies have shown that bone resorption is controlled by circadian rhythm, as indicated by diurnal variations in bone resorption, the molecular mechanism of circadian clock-dependent bone resorption remains unknown. To clarify the role of circadian rhythm in bone resorption, aryl hydrocarbon receptor nuclear translocator-like (Bmal1), a prototype circadian gene, was knocked out specifically in osteoclasts. Osteoclast-specific Bmal1-knockout mice showed a high bone mass phenotype due to reduced osteoclast differentiation. A cell-based assay revealed that BMAL1 upregulated nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 (Nfatc1) transcription through its binding to an E-box element located on the Nfatc1 promoter in cooperation with circadian locomotor output cycles kaput (CLOCK), a heterodimer partner of BMAL1. Moreover, steroid receptor coactivator (SRC) family members were shown to interact with and upregulate BMAL1:CLOCK transcriptional activity. Collectively, these data suggest that bone resorption is controlled by osteoclastic BMAL1 through interactions with the SRC family and binding to the Nfatc1 promoter. © 2016 American Society for Bone and Mineral Research. PMID:26841172

  16. The salient features of the clock

    DEFF Research Database (Denmark)

    Ebbesen, Toke Riis

    2005-01-01

    functional semiotics is explained in short terms and then further demonstrated in the analysis of a basic mechanical alarm clock. On this ground, the digital watch and digital design products in general are characterised and three possible avenues for the interpretation of the interactive possibilities of...

  17. An Iodine Fluorescence Quenching Clock Reaction

    Science.gov (United States)

    Weinberg, Richard B.; Muyskens, Mark

    2007-01-01

    Clock reactions based upon competing oxidation and reduction reactions of iodine and starch as the most popular type of chemistry example is presented to illustrate the redox phenomena, reaction kinetics, and principles of chemical titration. The examination of the photophysical principles underlying the iodine fluorescence quenching clock…

  18. On accelerated clocks and the quantum theory

    International Nuclear Information System (INIS)

    It is shown that the locality hypothesis of relativity breaks down for large proper accelerations which are relevant to semiclassical phenomena. A general modification for the rate of accelerated clocks incorporating the effect of proper acceleration is thus proposed. Connection is made with Caianiello's quantum line element

  19. Clock Synchronization for Multihop Wireless Sensor Networks

    Science.gov (United States)

    Solis Robles, Roberto

    2009-01-01

    In wireless sensor networks, more so generally than in other types of distributed systems, clock synchronization is crucial since by having this service available, several applications such as media access protocols, object tracking, or data fusion, would improve their performance. In this dissertation, we propose a set of algorithms to achieve…

  20. A New Pumping-Probing Scheme for the Optically Pumped Cesium Beam Frequency Standard

    Institute of Scientific and Technical Information of China (English)

    陈景标; 朱程锦; 王凤芝; 杨东海

    2001-01-01

    A new pumping-probing scheme for the optically pumped cesium beam frequency standard has been experimentally tested in our laboratory. The stability of the optically pumped cesium beam frequency standard was measured by comparing its 10 MHz output with an HP5071A commercial cesium atomic clock. The result shows that the frequency stability for the 1 s and 30000s sample times are 1.2 × 10-11 and 3.7 × 10-13, respectively. It was proved that the new pumping scheme works well.

  1. Suppression of clock shifts at field-insensitive transitions

    CERN Document Server

    Arnold, Kyle J

    2016-01-01

    We show that it is possible to significantly reduce quadrupole and tensor polarizability shifts of a clock transition by operating at a judiciously chosen field-insensitive point. In some cases shifts are almost completely eliminated making the transition an effective J = 0 to J = 0 candidate. This significantly improves the feasibility of a recent proposal for clock operation with large ion crystals. For such multi-ion clocks, geometric constraints and selection rules naturally divide clock operation into two categories based on the orientation of the magnetic field. We discuss the limitations imposed on each type and how calibrations might be carried out for clock operation.

  2. Atomic clocks: the atoms as primary time and frequency standards

    International Nuclear Information System (INIS)

    In this article, we present the atomic clock as time and frequency standard and as one of the peaceful uses of atoms for development. In the first part, we present the general principles of time and frequency metrology and the key role of the caesium atom in this field as well as the main applications of atomic clocks. In the second part we introduce the different clock technologies based on Ramsey method, with a focus on atomic beam clocks and atomic fountain clocks. (author)

  3. Next Generation JPL Ultra-Stable Trapped Ion Atomic Clocks

    Science.gov (United States)

    Burt, Eric; Tucker, Blake; Larsen, Kameron; Hamell, Robert; Tjoelker, Robert

    2013-01-01

    Over the past decade, trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on two directions: 1) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements, and 2) ultra-stable atomic clocks, usually for terrestrial applications emphasizing ultimate performance. In this paper we present a new ultra-stable trapped ion clock designed, built, and tested in the second category. The first new standard, L10, will be delivered to the Naval Research Laboratory for use in characterizing DoD space clocks.

  4. S-Wave Collisional Frequency Shift of a Fermion Clock

    CERN Document Server

    Hazlett, Eric L; Stites, Ronald W; Gibble, Kurt; O'Hara, Kenneth M

    2012-01-01

    We report an s-wave collisional frequency shift of an atomic clock based on fermions. In contrast to bosons, the fermion clock shift is insensitive to the population difference of the clock states, set by the first pulse area in Ramsey spectroscopy, \\theta_1. The fermion shift instead depends strongly on the second pulse area \\theta_2. It allows the shift to be canceled, nominally at \\theta_2 = \\pi/2, but correlations shift the null to slightly larger \\theta_2. The shift applies to optical lattice clocks and increases with the spatial inhomogeneity of the clock excitation field, naturally large at optical frequencies.

  5. Study on the Distribution of Networked Devices’ Clock Skew

    Directory of Open Access Journals (Sweden)

    Jiao Chengbo

    2011-08-01

    Full Text Available Clock skews of devices on the Internet are viewed as one way delay noise, but their distribution is unknown. We explore the distribution of clock skews to see the conflict probability. In this paper, we introduce an accurate clock skew estimation algorithm to filter inaccurate clock skew estimation by comparing the results between linear programming method and least square fitting. Delay jitter and other noises affect the estimation result. When the difference of two methods is large, the estimation result is unstable and inaccurate, so the estimation result should be dropped. Based on this algorithm, we use traces of real Internet measurements to collect 1825 accurate clock skews of different devices to establish a fingerprint database. Furthermore, we show the distribution of clock skews and comparing conflict probability with different number of devices. The distribution shows that clock skews are diverse, and most of clock skews are in the region of [-100, 100] PPM. The results indicate that when the number of devices is small (<5, clock skews won’t be conflict with each other, so clock skews are good tools to detect faked devices or NAT; When the number of devices increases, the conflict probability increases linearly, so clock skews of different devices can not distinguish each devices effectively.

  6. Clock distribution system for large high altitude air shower observatory

    International Nuclear Information System (INIS)

    In this paper, we report a clock distribution system for Water Cherenkov Detector Arrays (WCDAs) in Large High Altitude Air Shower Observatory (LHAASO) project. The designed electronics system is of high performance in implementing the clock distribution among detectors of a large scale of dimension. Based on Serializer/Deserializer (SerDes) and fiber transmission, the clock distribution system is the modules of central back end to distributed front end. The clock distribution system has been evaluated with a two modules system. While all the four SerDes candidates for clock transmission with jitters below 17 ps, the DS92LV16 has a fixed phase relationship between transmission clock and recovered clock, hence its use in LHAASO WCDAs. (authors)

  7. Satellite virtual atomic clock with pseudorange difference function

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Satellite atomic clocks are the basis of GPS for the control of time and frequency of navigation signals. In the Chinese Area Positioning System (CAPS), a satellite navigation system without the satellite atomic clocks onboard is successfully developed. Thus, the method of time synchronization based on satellite atomic clocks in GPS is not suitable. Satellite virtual atomic clocks are used to implement satellite navigation. With the satellite virtual atomic clocks, the time at which the signals are transmitted from the ground can be delayed into the time that the signals are transmitted from the satellites and the pseudorange measuring can be fulfilled as in GPS. Satellite virtual atomic clocks can implement the navigation, make a pseudorange difference, remove the ephemeris error, and improve the accuracy of navigation positioning. They not only provide a navigation system without satellite clocks, but also a navigation system with pseudorange difference.

  8. Entangling the lattice clock: Towards Heisenberg-limited timekeeping

    CERN Document Server

    Weinstein, Jonathan D; Derevianko, Andrei

    2009-01-01

    We present a scheme for entangling the atoms of an optical lattice to reduce the quantum projection noise of a clock measurement. The divalent clock atoms are held in a lattice at a ``magic'' wavelength that does not perturb the clock frequency -- to maintain clock accuracy -- while an open-shell J=1/2 ``head'' atom is coherently transported between lattice sites via the lattice polarization. This polarization-dependent ``Archimedes' screw'' transport at magic wavelength takes advantage of the vanishing vector polarizability of the scalar, J=0, clock states of bosonic isotopes of divalent atoms. The on-site interactions between the clock atoms and the head atom are used to engineer entanglement and for clock readout.

  9. Pump characteristics and applications

    CERN Document Server

    Volk, Michael

    2013-01-01

    Providing a wealth of information on pumps and pump systems, Pump Characteristics and Applications, Third Edition details how pump equipment is selected, sized, operated, maintained, and repaired. The book identifies the key components of pumps and pump accessories, introduces the basics of pump and system hydraulics as well as more advanced hydraulic topics, and details various pump types, as well as special materials on seals, motors, variable frequency drives, and other pump-related subjects. It uses example problems throughout the text, reinforcing the practical application of the formulae

  10. High-Voltage Clock Driver for Photon-Counting CCD Characterization

    Science.gov (United States)

    Baker, Robert

    2013-01-01

    A document discusses the CCD97 from e2v technologies as it is being evaluated at Goddard Space Flight Center's Detector Characterization Laboratory (DCL) for possible use in ultra-low background noise space astronomy applications, such as Terrestrial Planet Finder Coronagraph (TPF-C). The CCD97 includes a photoncounting mode where the equivalent output noise is less than one electron. Use of this mode requires a clock signal at a voltage level greater than the level achievable by the existing CCD (charge-coupled-device) electronics. A high-voltage waveform generator has been developed in code 660/601 to support the CCD97 evaluation. The unit generates required clock waveforms at voltage levels from -20 to +50 V. It deals with standard and arbitrary waveforms and supports pixel rates from 50 to 500 kHz. The system is designed to interface with existing Leach CCD electronics.

  11. Ionization and transient absorption control with a resonant attosecond clock

    International Nuclear Information System (INIS)

    Metastable states are important actors in the ionisation of atoms and molecules. Sub-femtosecond extreme ultraviolet pulses can coherently populate several transiently bound states at once, thus starting the attosecond clocks which are required to monitor and control ultrafast electronic evolution above the ionisation threshold. Here we illustrate, from a theoretical point of view, the effects coherent superpositions of 1Po doubly excited states in the helium atom have on channel-resolved photoelectron spectra as well as on the transient absorption spectrum of the atom in the extreme ultraviolet region, when they are created by a single-attosecond pulse in the presence of a strong few-cycle near-infrared/visible pulse which acts as a probe. Interference fringes varying rapidly with the pump-probe time delay are visible in both photoelectron and transient absorption spectra. From such fringes, the wave packet itself can conceivably be reconstructed. Conversely, all observables are modulated by the characteristic beating periods of the wave packet, so that control of partial ionisation yields, branching ratios, and light absorption or amplification can be achieved

  12. Optimal implementations for reliable circadian clocks.

    Science.gov (United States)

    Hasegawa, Yoshihiko; Arita, Masanori

    2014-09-01

    Circadian rhythms are acquired through evolution to increase the chances for survival through synchronizing with the daylight cycle. Reliable synchronization is realized through two trade-off properties: regularity to keep time precisely, and entrainability to synchronize the internal time with daylight. We find by using a phase model with multiple inputs that achieving the maximal limit of regularity and entrainability entails many inherent features of the circadian mechanism. At the molecular level, we demonstrate the role sharing of two light inputs, phase advance and delay, as is well observed in mammals. At the behavioral level, the optimal phase-response curve inevitably contains a dead zone, a time during which light pulses neither advance nor delay the clock. We reproduce the results of phase-controlling experiments entrained by two types of periodic light pulses. Our results indicate that circadian clocks are designed optimally for reliable clockwork through evolution. PMID:25238386

  13. Supporting Family Awareness with the Whereabouts Clock

    Science.gov (United States)

    Sellen, Abigail; Taylor, Alex S.; Kaye, Joseph ‘Jofish'; Brown, Barry; Izadi, Shahram

    We report the results of a field trial of a situated awareness device for families called the “Whereabouts Clock”. The Clock displays the location of family members using cellphone data as one of four privacy-preserving, deliberately coarse-grained categories ( HOME, WORK, SCHOOL or ELSEWHERE). The results show that awareness of others through the Clock supports not only family communication and coordination but also more emotive aspects of family life such as reassurance, connectedness, identity and social touch. We discuss how the term “awareness” means many things in practice and highlight the importance of designing not just for family activities, but in order to support the emotional, social and even moral aspects of family life.

  14. The suprachiasmatic nuclei as a seasonal clock.

    Science.gov (United States)

    Coomans, Claudia P; Ramkisoensing, Ashna; Meijer, Johanna H

    2015-04-01

    In mammals, the suprachiasmatic nucleus (SCN) contains a central clock that synchronizes daily (i.e., 24-h) rhythms in physiology and behavior. SCN neurons are cell-autonomous oscillators that act synchronously to produce a coherent circadian rhythm. In addition, the SCN helps regulate seasonal rhythmicity. Photic information is perceived by the SCN and transmitted to the pineal gland, where it regulates melatonin production. Within the SCN, adaptations to changing photoperiod are reflected in changes in neurotransmitters and clock gene expression, resulting in waveform changes in rhythmic electrical activity, a major output of the SCN. Efferent pathways regulate the seasonal timing of breeding and hibernation. In humans, seasonal physiology and behavioral rhythms are also present, and the human SCN has seasonally rhythmic neurotransmitter levels and morphology. In summary, the SCN perceives and encodes changes in day length and drives seasonal changes in downstream pathways and structures in order to adapt to the changing seasons. PMID:25451984

  15. The Large Built Water Clock Of Amphiaraeion.

    Science.gov (United States)

    Theodossiou, E.; Katsiotis, M.; Manimanis, V. N.; Mantarakis, P.

    A very well preserved ancient water clock was discovered during excavations at the Amphiaraeion, in Oropos, Greece. The Amphiaraeion, a famous religious and oracle center of the deified healer Amphiaraus, was active from the pre-classic period until the replacement of the ancient religion by Christianity in the 5th Century A.D.. The foretelling was supposedly done through dreams sent by the god to the believers sleeping in a special gallery. In these dreams the god suggesting to them the therapy for their illness or the solution to their problems. The patients, then threw coins into a spring of the sanctuary. In such a place, the measurement of time was a necessity. Therefore, time was kept with both a conical sundial and a water clock in the form of a fountain. According to archeologists, the large built structure that measured the time for the sanctuary dates from the 4th Century B.C.

  16. Laser-induced quantum pumping in graphene

    Energy Technology Data Exchange (ETDEWEB)

    San-Jose, Pablo [Instituto de Estructura de la Materia (IEM-CSIC), Serrano 123, 28006 Madrid (Spain); Prada, Elsa; Kohler, Sigmund [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Schomerus, Henning [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2012-10-08

    We investigate non-adiabatic electron pumping in graphene generated by laser irradiation with linear polarization parallel or perpendicular to the transport direction. Transport is dominated by the spatially asymmetric excitation of electrons from evanescent into propagating modes. For a laser with parallel polarization, the pumping response exhibits a subharmonic resonant enhancement which directly probes the Fermi energy; no such enhancement occurs for perpendicular polarization. The resonance mechanism relies on the chirality of charge carriers in graphene.

  17. Clock drawing performance in cognitively normal elderly

    OpenAIRE

    Hubbard, E J; Santini, V; Blankevoort, C.G.; Volkers, K.M.; Barrup, M.S.; Byerly, L; Chaisson, C.; Jefferson, A.L.; Kaplan, E; Green, R.C.; Stern, R. A.

    2008-01-01

    The Clock Drawing Test (CDT) is a common neuropsychological measure sensitive to cognitive changes and functional skills (e.g., driving test performance) among older adults. However, normative data have not been adequately developed. We report the distribution of CDT scores using three common scoring systems (Mendez, Ala, and Underwood, 1992; Freund, Gravenstein, Ferris, Burke, & Shaheen, 2005; and Cahn, Salmon, Monsch, Butters, Wiederholt, & Corey-Bloom, 1996), among 207 cognitively normal e...

  18. The circadian clock, reward and memory

    OpenAIRE

    Urs eAlbrecht

    2011-01-01

    During our daily activities, we experience variations in our cognitive performance, which is often accompanied by cravings for small rewards, such as consuming coffee or chocolate. This indicates that the time of day, cognitive performance, and reward may be related to one another. This review will summarize data that describe the influence of the circadian clock on addiction and mood-related behavior and put the data into perspective in relation to memory processes.

  19. Absolute clock synchronisation and special relativity paradoxes

    OpenAIRE

    Ciborowski, Jacek; Wlodarczyk, Marta

    2012-01-01

    Solving special relativity paradoxes requires rigorous analysis of event timing, due to relative simultaneity in consequence of the Lorentz transformation. Since clock synchronisation is a convention in special theory of relativity, instead of the Einstein's procedure one may choose such that offers absolute simultaneity. We present in short the corresponding formalism in one spatial dimension. We show that paradoxes do not arise with this choice of synchronisation and descriptions of these i...

  20. Molecular clock in neutral protein evolution

    Directory of Open Access Journals (Sweden)

    Wilke Claus O

    2004-08-01

    Full Text Available Abstract Background A frequent observation in molecular evolution is that amino-acid substitution rates show an index of dispersion (that is, ratio of variance to mean substantially larger than one. This observation has been termed the overdispersed molecular clock. On the basis of in silico protein-evolution experiments, Bastolla and coworkers recently proposed an explanation for this observation: Proteins drift in neutral space, and can temporarily get trapped in regions of substantially reduced neutrality. In these regions, substitution rates are suppressed, which results in an overall substitution process that is not Poissonian. However, the simulation method of Bastolla et al. is representative only for cases in which the product of mutation rate μ and population size Ne is small. How the substitution process behaves when μNe is large is not known. Results Here, I study the behavior of the molecular clock in in silico protein evolution as a function of mutation rate and population size. I find that the index of dispersion decays with increasing μNe, and approaches 1 for large μNe . This observation can be explained with the selective pressure for mutational robustness, which is effective when μNe is large. This pressure keeps the population out of low-neutrality traps, and thus steadies the ticking of the molecular clock. Conclusions The molecular clock in neutral protein evolution can fall into two distinct regimes, a strongly overdispersed one for small μNe, and a mostly Poissonian one for large μNe. The former is relevant for the majority of organisms in the plant and animal kingdom, and the latter may be relevant for RNA viruses.

  1. Regulated DNA Methylation and the Circadian Clock: Implications in Cancer

    Directory of Open Access Journals (Sweden)

    Tammy M. Joska

    2014-09-01

    Full Text Available Since the cloning and discovery of DNA methyltransferases (DNMT, there has been a growing interest in DNA methylation, its role as an epigenetic modification, how it is established and removed, along with the implications in development and disease. In recent years, it has become evident that dynamic DNA methylation accompanies the circadian clock and is found at clock genes in Neurospora, mice and cancer cells. The relationship among the circadian clock, cancer and DNA methylation at clock genes suggests a correlative indication that improper DNA methylation may influence clock gene expression, contributing to the etiology of cancer. The molecular mechanism underlying DNA methylation at clock loci is best studied in the filamentous fungi, Neurospora crassa, and recent data indicate a mechanism analogous to the RNA-dependent DNA methylation (RdDM or RNAi-mediated facultative heterochromatin. Although it is still unclear, DNA methylation at clock genes may function as a terminal modification that serves to prevent the regulated removal of histone modifications. In this capacity, aberrant DNA methylation may serve as a readout of misregulated clock genes and not as the causative agent. This review explores the implications of DNA methylation at clock loci and describes what is currently known regarding the molecular mechanism underlying DNA methylation at circadian clock genes.

  2. Photoperiodic plasticity in circadian clock neurons in insects

    Directory of Open Access Journals (Sweden)

    Sakiko eShiga

    2013-08-01

    Full Text Available Since Bünning’s observation of circadian rhythms and photoperiodism in the runner bean Phaseolus multiflorus in 1936, many studies have shown that photoperiodism is based on the circadian clock system. In insects, involvement of circadian clock genes or neurons has been recently shown in the photoperiodic control of developmental arrests, diapause. Based on molecular and neuronal studies in Drosophila melanogaster, photoperiodic changes have been reported for expression patterns of the circadian clock genes, subcellular distribution of clock proteins, fiber distribution, or the number of plausible clock neurons in different species. Photoperiod sets peaks of per or tim mRNA abundance at lights-off in Sarcophaga crassipalpis, Chymomyza costata and Protophormia terraenovae. Abundance of per and Clock mRNA changes by photoperiod in Pyrrhocoris apterus. Subcellular Per distribution in circadian clock neurons changes with photoperiod in P. terraenovae. Although photoperiodism is not known in Leucophaea maderae, under longer day length, more stomata and longer commissural fibers of circadian clock neurons have been found. These plastic changes in the circadian clock neurons could be an important constituent for photoperiodic clock mechanisms to integrate repetitive photoperiodic information and produce different outputs based on day length.

  3. Velocity Distribution of Effective Atoms in a Small Optically Pumped Cesium Beam Frequency Standard

    Institute of Scientific and Technical Information of China (English)

    CHEN Jingbiao; WANG Fengzhi; YANG Donghai; WANG YiQiu

    2001-01-01

    In this paper, the velocity distribution of effective atoms in a small optically pumped cesium beam frequency standard has been achieved from the Fourier transforms of the experimentally recorded Ramsey patterns. The result fits well with the theoretical calculation. The second order Doppler shift correction of the small cesium atomic clock is obtained from the velocity distribution of effective atoms.

  4. Clock drawing performance in cognitively normal elderly.

    Science.gov (United States)

    Hubbard, Emily J; Santini, Veronica; Blankevoort, Christiaan G; Volkers, Karin M; Barrup, Melissa S; Byerly, Laura; Chaisson, Christine; Jefferson, Angela L; Kaplan, Edith; Green, Robert C; Stern, Robert A

    2008-05-01

    The Clock Drawing Test (CDT) is a common neuropsychological measure sensitive to cognitive changes and functional skills (e.g., driving test performance) among older adults. However, normative data have not been adequately developed. We report the distribution of CDT scores using three common scoring systems [Mendez, M. F., Ala, T., & Underwood, K. L. (1992). Development of scoring criteria for the Clock Drawing Task in Alzheimer's Disease. Journal of the American Geriatrics Society, 40, 1095-1099; Cahn, D. A., Salmon, D. P., Monsch, A. U., Butters, N., Wiederholt, W. C., & Corey-Bloom, J. (1996). Screening for dementia of the Alzheimer type in the community: The utility of the Clock Drawing Test. Archives of Clinical Neuropsychology, 11(6), 529-539], among 207 cognitively normal elderly. The systems were well correlated, took little time to use, and had high inter-rater reliability. We found statistically significant differences in CDT scores based on age and WRAT-3 Reading score, a marker of education quality. We present means, standard deviations, and t- and z-scores based on these subgroups. We found that "normal" CDT performance includes a wider distribution of scores than previously reported. Our results may serve as useful comparisons for clinicians wishing to know whether their patients perform in the general range of cognitively normal elderly. PMID:18243644

  5. A microresonator frequency comb optical clock

    CERN Document Server

    Papp, Scott B; DelHaye, Pascal; Quinlan, Franklyn; Lee, Hansuek; Vahala, Kerry J; Diddams, Scott A

    2013-01-01

    Optical-frequency combs enable measurement precision at the 20th digit, and accuracy entirely commensurate with their reference oscillator. A new direction in experiments is the creation of ultracompact frequency combs by way of nonlinear parametric optics in microresonators. We refer to these as microcombs, and here we report a silicon-chip-based microcomb optical clock that phase-coherently converts an optical-frequency reference to a microwave signal. A low-noise comb spectrum with 25 THz span is generated with a 2 mm diameter silica disk and broadening in nonlinear fiber. This spectrum is stabilized to rubidium frequency references separated by 3.5 THz by controlling two teeth 108 modes apart. The optical clocks output is the electronically countable 33 GHz microcomb line spacing, which features an absolute stability better than the rubidium transitions by the expected factor of 108. Our work demonstrates the comprehensive set of tools needed for interfacing microcombs to state-of-the-art optical clocks.

  6. Quantum mechanics, matter waves, and moving clocks

    CERN Document Server

    Mueller, Holger

    2013-01-01

    This paper is divided into three parts. In the first (section 1), we demonstrate that all of quantum mechanics can be derived from the fundamental property that the propagation of a matter wave packet is described by the same gravitational and kinematic time dilation that applies to a clock. We will do so in several steps, first deriving the Schroedinger equation for a nonrelativistic particle without spin in a weak gravitational potential, and eventually the Dirac equation in curved space-time describing the propagation of a relativistic particle with spin in strong gravity. In the second part (sections 2-4), we present interesting consequences of the above quantum mechanics: that it is possible to use wave packets as a reference for a clock, to test general relativity, and to realize a mass standard based on a proposed redefinition of the international system of units, wherein the Planck constant would be assigned a fixed value. The clock achieved an absolute accuracy of 4 parts per billion (ppb). The exper...

  7. Atomic Clocks with Suppressed Blackbody Radiation Shift

    International Nuclear Information System (INIS)

    We develop a concept of atomic clocks where the blackbody radiation shift and its fluctuations can be suppressed by 1-3 orders of magnitude independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ν1 and ν2) which are exposed to the same thermal environment, there exists a 'synthetic' frequency νsyn ∝ (ν1-ε12ν2) largely immune to the blackbody radiation shift. For example, in the case of 171Yb+ it is possible to create a synthetic-frequency-based clock in which the fractional blackbody radiation shift can be suppressed to the level of 10-18 in a broad interval near room temperature (300±15 K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ν1 and ν2, where the frequency νsyn is generated as one of the components of the comb spectrum.

  8. Quantum Adiabatic Pumping by Modulating Tunnel Phase in Quantum Dots

    Science.gov (United States)

    Taguchi, Masahiko; Nakajima, Satoshi; Kubo, Toshihiro; Tokura, Yasuhiro

    2016-08-01

    In a mesoscopic system, under zero bias voltage, a finite charge is transferred by quantum adiabatic pumping by adiabatically and periodically changing two or more control parameters. We obtained expressions for the pumped charge for a ring of three quantum dots (QDs) by choosing the magnetic flux penetrating the ring as one of the control parameters. We found that the pumped charge shows a steplike behavior with respect to the variance of the flux. The value of the step heights is not universal but depends on the trajectory of the control parameters. We discuss the physical origin of this behavior on the basis of the Fano resonant condition of the ring.

  9. Heat pump technology

    CERN Document Server

    Von Cube, Hans Ludwig; Goodall, E G A

    2013-01-01

    Heat Pump Technology discusses the history, underlying concepts, usage, and advancements in the use of heat pumps. The book covers topics such as the applications and types of heat pumps; thermodynamic principles involved in heat pumps such as internal energy, enthalpy, and exergy; and natural heat sources and energy storage. Also discussed are topics such as the importance of the heat pump in the energy industry; heat pump designs and systems; the development of heat pumps over time; and examples of practical everyday uses of heat pumps. The text is recommended for those who would like to kno

  10. Optically pumped polarized H- ion source

    International Nuclear Information System (INIS)

    The current status and future prospects for the optically pumped polarized H- ion source are discussed. At the present time H- ion currents of 60 μA and with a polarization of 65% have been produced. The ion current and polarization can be increased significantly if the optically pumped Na charge exchange target density and polarization can be increased. Studies of wall surfaces that permit many bounces before depolarizing the Na electron spin and studies of radiation trapping in optically pumped Na indicate that the Na target density and polarization can be increased substantially. 27 refs., 6 figs., 2 tabs

  11. On the clock paradox in the case of circular motion of the moving clock

    International Nuclear Information System (INIS)

    Very often in many textbooks the formalism of the general theory of relativity is applied to gravitational problems. We think that it would be didactically useful to show how it can be adopted also for describing physical situations in accelerated frames of reference by working out in detail a particular case. This choice will also offer an opportunity to discuss a classical topic of relativistic physics. Indeed, we deal analytically with a version of the so-called clock paradox in which the moving clock performs a circular motion. The rest clock is denoted as (1), the rotating clock is (2), the inertial frame in which (1) is at rest and (2) moves is I and, finally, the accelerated frame in which (2) is at rest and (1) rotates is A. By using the general theory of relativity in order to describe the motion of (1) as seen in A we will show the following features. (I) A differential ageing between (1) and (2) occurs at their reunion and it has an absolute character, i.e. the proper time interval measured by a given clock is the same both in I and in A. (II) From a quantitative point of view, the magnitude of the differential ageing between (1) and (2) does depend on the kind of rotational motion performed by A. Indeed, if it is uniform there is no tangential force in the direction of motion of (2) but only normal to it. In this case, the proper time interval reckoned by (2) does depend only on its constant velocity v = rω. In contrast, if the rotational motion is uniformly accelerated, i.e. a constant force acts tangentially along the direction of motion, the proper time intervals do depend on the angular acceleration α. (III) Finally, in regard to the sign of the ageing, the moving clock (2) always measures a shorter interval of proper time with respect to (1)

  12. The Effects of Clock Drift on the Mars Exploration Rovers

    Science.gov (United States)

    Ali, Khaled S.; Vanelli, C. Anthony

    2012-01-01

    All clocks drift by some amount, and the mission clock on the Mars Exploration Rovers (MER) is no exception. The mission clock on both MER rovers drifted significantly since the rovers were launched, and it is still drifting on the Opportunity rover. The drift rate is temperature dependent. Clock drift causes problems for onboard behaviors and spacecraft operations, such as attitude estimation, driving, operation of the robotic arm, pointing for imaging, power analysis, and telecom analysis. The MER operations team has techniques to deal with some of these problems. There are a few techniques for reducing and eliminating the clock drift, but each has drawbacks. This paper presents an explanation of what is meant by clock drift on the rovers, its relationship to temperature, how we measure it, what problems it causes, how we deal with those problems, and techniques for reducing the drift.

  13. Synthetic Spin-Orbit Coupling in an Optical Lattice Clock

    Science.gov (United States)

    Wall, Michael L.; Koller, Andrew P.; Li, Shuming; Zhang, Xibo; Cooper, Nigel R.; Ye, Jun; Rey, Ana Maria

    2016-01-01

    We propose the use of optical lattice clocks operated with fermionic alkaline-earth atoms to study spin-orbit coupling (SOC) in interacting many-body systems. The SOC emerges naturally during the clock interrogation, when atoms are allowed to tunnel and accumulate a phase set by the ratio of the "magic" lattice wavelength to the clock transition wavelength. We demonstrate how standard protocols such as Rabi and Ramsey spectroscopy that take advantage of the sub-Hertz resolution of state-of-the-art clock lasers can perform momentum-resolved band tomography and determine SOC-induced s -wave collisions in nuclear-spin-polarized fermions. With the use of a second counterpropagating clock beam, we propose a method for engineering controlled atomic transport and study how it is modified by p - and s -wave interactions. The proposed spectroscopic probes provide clean and well-resolved signatures at current clock operating temperatures.

  14. Realization of a time-scale with an optical clock

    CERN Document Server

    Grebing, C; Dörscher, S; Häfner, S; Gerginov, V; Weyers, S; Lipphardt, B; Riehle, F; Sterr, U; Lisdat, C

    2015-01-01

    Optical clocks are not only powerful tools for prime fundamental research, but are also deemed for the re-definition of the SI base unit second as they surpass the performance of caesium atomic clocks in both accuracy and stability by more than an order of magnitude. However, an important obstacle in this transition has so far been the limited reliability of the optical clocks that made a continuous realization of a time-scale impractical. In this paper, we demonstrate how this dilemma can be resolved and that a time-scale based on an optical clock can be established that is superior to one based on even the best caesium fountain clocks. The paper also gives further proof of the international consistency of strontium lattice clocks on the $10^{-16}$ accuracy level, which is another prerequisite for a change in the definition of the second.

  15. Clock Auto-synchronizing Method for BES III ETOF Upgrade

    CERN Document Server

    Si-Yu, Wang; Shu-Bin, Liu; Qi, An

    2015-01-01

    An automatic clock synchronizing method implemented in field programmable gate array (FPGA) is proposed in this paper. It is developed for the clock system which will be applied in the end-cap time of flight (ETOF) upgrade of the Beijing Spectrometer (BESIII). In this design, an FPGA is used to automatically monitor the synchronization circuit and deal with signals coming from external clock synchronization circuit. By testing different delay time of the detection signal and analyzing state signals returned, the synchronization windows will be found automatically in FPGA. The new clock system not only retains low clock jitter which is less than 20ps root mean square (RMS), but also demonstrates automatic synchronization to the beam bunches. So far, the clock auto-synchronizing function has been working successfully under a series of tests. It will greatly simplify the system initialization and maintenance in the future.

  16. A clock network for geodesy and fundamental science

    CERN Document Server

    Lisdat, C; Quintin, N; Shi, C; Raupach, S M F; Grebing, C; Nicolodi, D; Stefani, F; Al-Masoudi, A; Dörscher, S; Häfner, S; Robyr, J -L; Chiodo, N; Bilicki, S; Bookjans, E; Koczwara, A; Koke, S; Kuhl, A; Wiotte, F; Meynadier, F; Camisard, E; Abgrall, M; Lours, M; Legero, T; Schnatz, H; Sterr, U; Denker, H; Chardonnet, C; Coq, Y Le; Santarelli, G; Amy-Klein, A; Targat, R Le; Lodewyck, J; Lopez, O; Pottie, P -E

    2015-01-01

    Leveraging the unrivaled performance of optical clocks in applications in fundamental physics beyond the standard model, in geo-sciences, and in astronomy requires comparing the frequency of distant optical clocks truthfully. Meeting this requirement, we report on the first comparison and agreement of fully independent optical clocks separated by 700 km being only limited by the uncertainties of the clocks themselves. This is achieved by a phase-coherent optical frequency transfer via a 1415 km long telecom fiber link that enables substantially better precision than classical means of frequency transfer. The fractional precision in comparing the optical clocks of three parts in $10^{17}$ was reached after only 1000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than with any other existing frequency transfer method. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optic...

  17. Electromagnetic synchronisation of clocks with finite separation in a rotating system

    International Nuclear Information System (INIS)

    For clocks on the vertices of a triangle, it is shown that clock synchronisation using electromagnetic signals between finitely spaced clocks in a rotating frame leads to the same synchronisation error as a closely spaced band of clocks along the same light path. In addition, the above result is generalised to n equally spaced clocks. (author)

  18. A Blind Circadian Clock in Cavefish Reveals that Opsins Mediate Peripheral Clock Photoreception

    OpenAIRE

    Cavallari, N; E.Frigato; Vallone, D.; N.Fröhlich; J.F. Lopez-Olmeda; A.Foà; R.De Berti; Sánchez-Vázquez, F. J.; C.Bertolucci; Foulkes, N S

    2011-01-01

    The circadian clock is a physiological timing mechanism that allows organisms to anticipate and adapt to the day-night cycle. Since it ticks with a period that is not precisely 24 h, it is vital that it is reset on a daily basis by signals such as light to ensure that it remains synchronized with the day-night cycle. The molecular mechanisms whereby light regulates the clock remain incompletely understood. Here we have studied a cavefish that has evolved for millions of years in the perpetual...

  19. Clock rates, clock settings and the physics of the space-time Lorentz transformation

    CERN Document Server

    Field, J H

    2006-01-01

    A careful study is made of the operational meaning of the time symbols appearing in the space-time Lorentz transformation. Four distinct symbols, with different physical meanings, are needed to describe reciprocal measurements involving stationary and uniformly-moving clocks. Physical predictions concern only the observed rate of a clock as a function of its relative speed, not its setting. How the failure to make this distinction leads to the conventional predictions of spurious `relativity of simultaneity' and `length contraction' effects in special relativity is explained.

  20. The circadian clock and cell cycle: Interconnected biological circuits

    OpenAIRE

    Masri, Selma; Cervantes, Marlene; Sassone-Corsi, Paolo

    2013-01-01

    The circadian clock governs biological timekeeping on a systemic level, helping to regulate and maintain physiological processes, including endocrine and metabolic pathways with a periodicity of 24-hours. Disruption within the circadian clock machinery has been linked to numerous pathological conditions, including cancer, suggesting that clock-dependent regulation of the cell cycle is an essential control mechanism. This review will highlight recent advances on the ‘gating’ controls of the ci...

  1. Atomic fountains and optical clocks at SYRTE: status and perspectives

    CERN Document Server

    Abgrall, M; De Sarlo, L; Guéna, J; Laurent, Ph; Coq, Y Le; Targat, R Le; Lodewyck, J; Lours, M; Rosenbusch, P; Rovera, D; Bize, S

    2015-01-01

    In this article, we report on the work done with the LNE-SYRTE atomic clock ensemble during the last 10 years. We cover progress made in atomic fountains and in their application to timekeeping. We also cover the development of optical lattice clocks based on strontium and on mercury. We report on tests of fundamental physical laws made with these highly accurate atomic clocks. We also report on work relevant to a future possible redefinition of the SI second.

  2. Clocks and dynamics in quantum models of gravity

    OpenAIRE

    Malkiewicz, Przemyslaw

    2016-01-01

    We investigate how the quantum dynamics of gravitational models depend on the clocks employed in quantization procedure. Our previous result demonstrates that almost all physical features of quantum cosmological bounces depend on the choice of clock. The vital question whether all the quantum (or, semiclassical) solutions admit, away from the quantum interaction region in the far past and future, invariant asymptotic limits irrespectively of the clock's choice is addressed herein. We analyze ...

  3. The Clock-Proxy Auction: A Practical Combinatorial Auction Design

    OpenAIRE

    Lawrence M. Ausubel; Peter Cramton; Paul Milgrom

    2004-01-01

    We propose the clock-proxy auction as a practical means for auctioning many related items. A clock auction phase is followed by a last-and-final proxy round. The approach combines the simple and transparent price discovery of the clock auction with the efficiency of the proxy auction. Linear pricing is maintained as long as possible, but then is abandoned in the proxy round to improve efficiency and enhance seller revenues. The approach has many advantages over the simultaneous ascending auct...

  4. Gated Clock Implementation of Arithmetic Logic Unit (ALU)

    OpenAIRE

    Dr. Neelam R. Prakash; Akash

    2013-01-01

    Low power design has emerged as one of the challenging area in today’s ASIC (Application specific integrated circuit) design. With continuous decrease in transistor size, power density is increasing and there is an urgent need for reduction in total power consumption. Clock gating is one most effective technique for low power synchronous circuit design. Clock gating technique in low power design is used to reduce the dynamic power consumption. Clock signal in a synchronous circuit is used for...

  5. Relativity theory and time perception: single or multiple clocks?

    Directory of Open Access Journals (Sweden)

    Catalin V Buhusi

    Full Text Available BACKGROUND: Current theories of interval timing assume that humans and other animals time as if using a single, absolute stopwatch that can be stopped or reset on command. Here we evaluate the alternative view that psychological time is represented by multiple clocks, and that these clocks create separate temporal contexts by which duration is judged in a relative manner. Two predictions of the multiple-clock hypothesis were tested. First, that the multiple clocks can be manipulated (stopped and/or reset independently. Second, that an event of a given physical duration would be perceived as having different durations in different temporal contexts, i.e., would be judged differently by each clock. METHODOLOGY/PRINCIPAL FINDINGS: Rats were trained to time three durations (e.g., 10, 30, and 90 s. When timing was interrupted by an unexpected gap in the signal, rats reset the clock used to time the "short" duration, stopped the "medium" duration clock, and continued to run the "long" duration clock. When the duration of the gap was manipulated, the rats reset these clocks in a hierarchical order, first the "short", then the "medium", and finally the "long" clock. Quantitative modeling assuming re-allocation of cognitive resources in proportion to the relative duration of the gap to the multiple, simultaneously timed event durations was used to account for the results. CONCLUSIONS/SIGNIFICANCE: These results indicate that the three event durations were effectively timed by separate clocks operated independently, and that the same gap duration was judged relative to these three temporal contexts. Results suggest that the brain processes the duration of an event in a manner similar to Einstein's special relativity theory: A given time interval is registered differently by independent clocks dependent upon the context.

  6. AMPK at the crossroads of circadian clocks and metabolism

    OpenAIRE

    Jordan, Sabine D.; Lamia, Katja A.

    2012-01-01

    Circadian clocks coordinate behavior and physiology with daily environmental cycles and thereby optimize the timing of metabolic processes such as glucose production and insulin secretion. Such circadian regulation of metabolism provides an adaptive advantage in diverse organisms. Mammalian clocks are primarily based on a transcription and translation feedback loop in which a heterodimeric complex of the transcription factors CLOCK (circadian locomotor output cycles kaput) and BMAL1 (brain an...

  7. A CPT-based Cs vapor cell atomic clock with a short-term fractional frequency stability of 3 x 10-13 τ-1/2

    Science.gov (United States)

    Abdel Hafiz, Moustafa; Liu, Xiaochi; Guérandel, Stéphane; De Clercq, Emeric; Boudot, Rodolphe

    2016-06-01

    This article reports on the development and short-term fractional frequency stability of a continuous-regime (CW) Cs vapor cell atomic clock based on coherent population trapping (CPT). The push-pull optical pumping technique is used to increase the number of atoms that participate to the clock transition, yielding a typical CPT resonance contrast of 25% for a CPT linewidth of about 450 Hz. The clock short-term fractional frequency stability is measured to be 3 x 10-13 τ-1/2 up to 100 seconds averaging time, in correct agreement with the signal-to-noise ratio limit. The mid-term frequency stability results are currently mainly limited by laser power effects. The detection of high-contrast narrow Raman-Ramsey fringes is demonstrated with this setup by making the atoms interact with a light pulse sequence.

  8. Power and Skew Aware Point Diffusion Clock Network

    Science.gov (United States)

    Jung, Gunok; Kim, Chunghee; Chae, Kyoungkuk; Park, Giho; Park, Sung Bae

    This letter presents point diffusion clock network (PDCN) with local clock tree synthesis (CTS) scheme. The clock network is implemented with ten times wider metal line space than typical mesh networks for low power and utilized to nine times smaller area CTS execution for minimized clock skew amount. The measurement results show that skew amount of PDCN with local CTS is reduced to 36% and latency is shrunk to 45% of the amount in a 4.81mm2 CortexA-8 core with 65nm Samsung process.

  9. Transcripts from the Circadian Clock: Telling Time and Season

    OpenAIRE

    Brand, Karl

    2011-01-01

    textabstractWe all know it when we wake mere moments before an alarm clock is scheduled to wake us: our body clock made the alarm clock redundant. This phenomenon is driven by an endogenous timer known as the biological, or circadian clock. Each revolution of the Earth about its own axis produces periods of light and dark which define what we all experience as a ‘day’. This profound cyclic variation in solar energy is responsible for driving the evolution of adaptive responses as early as 3.8...

  10. Real-time geopotentiometry with synchronously linked optical lattice clocks

    CERN Document Server

    Takano, Tetsushi; Ushijima, Ichiro; Ohmae, Noriaki; Akatsuka, Tomoya; Yamaguchi, Atsushi; Kuroishi, Yuki; Munekane, Hiroshi; Miyahara, Basara; Katori, Hidetoshi

    2016-01-01

    According to the Einstein's theory of relativity, the passage of time changes in a gravitational field. On earth, raising a clock by one centimetre increases its tick rate by 1.1 parts in 10$^{18}$, enabling optical clocks to perform precision geodesy. Here, we demonstrate geopotentiometry by determining the height difference of master and slave clocks separated by 15 km with uncertainty of 5 cm. The subharmonic of the master clock is delivered through a telecom fibre to phase-lock and synchronously interrogate the slave clock. This protocol rejects laser noise in the comparison of two clocks, which improves the stability of measuring the gravitational red shift. Such phase-coherently operated clocks facilitate proposals for linking clocks and interferometers. Over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be $1,652.9(5.9)\\times 10^{-18}$, or a height difference of 1,516(5) cm, consistent with an independent measurement by levelling and gravimetry. Ou...

  11. Temperature regulates transcription in the zebrafish circadian clock.

    Directory of Open Access Journals (Sweden)

    2005-11-01

    Full Text Available It has been well-documented that temperature influences key aspects of the circadian clock. Temperature cycles entrain the clock, while the period length of the circadian cycle is adjusted so that it remains relatively constant over a wide range of temperatures (temperature compensation. In vertebrates, the molecular basis of these properties is poorly understood. Here, using the zebrafish as an ectothermic model, we demonstrate first that in the absence of light, exposure of embryos and primary cell lines to temperature cycles entrains circadian rhythms of clock gene expression. Temperature steps drive changes in the basal expression of certain clock genes in a gene-specific manner, a mechanism potentially contributing to entrainment. In the case of the per4 gene, while E-box promoter elements mediate circadian clock regulation, they do not direct the temperature-driven changes in transcription. Second, by studying E-box-regulated transcription as a reporter of the core clock mechanism, we reveal that the zebrafish clock is temperature-compensated. In addition, temperature strongly influences the amplitude of circadian transcriptional rhythms during and following entrainment by light-dark cycles, a property that could confer temperature compensation. Finally, we show temperature-dependent changes in the expression levels, phosphorylation, and function of the clock protein, CLK. This suggests a mechanism that could account for changes in the amplitude of the E-box-directed rhythm. Together, our results imply that several key transcriptional regulatory elements at the core of the zebrafish clock respond to temperature.

  12. The role of the mechanical clock in medieval science.

    Science.gov (United States)

    Álvarez, Víctor Pérez

    2015-03-01

    The invention and spread of the mechanical clock is a complex and multifaceted historical phenomenon. Some of these facets, such as its social impact, have been widely studied, but their scientific dimensions have often been dismissed. The mechanical clock was probably born as a scientific instrument for driving a model of the universe, and not only natural philosophers but also kings, nobles and other members of the social elites showed an interest in clocks as scientific instruments. Public clocks later spread a new way of telling time based on equal hours, laying the foundations for changes in time consciousness that would accelerate scientific thinking. PMID:25802023

  13. A theoretical study of induction eletrohydrodynamic pumping in outer space

    Energy Technology Data Exchange (ETDEWEB)

    Seyed-Yagoobi, J. (Texas A and M Univ., College Station (USA))

    1990-11-01

    The challenge for designers of a space station is to meet requirements ofweight, reliability, power, and maintainability. Several new technologies must be developed to insure the success of the space station. Electrohydrodynamic (EHD) pumping may have an impact on the design of novel pumping devices for space stations or other space-related operations. The principal advantage of EHD pumping is that it is non-mechanical; therefore, it has neither moving mechanical parts nor the need for external pressure for operation. Typical applications of EHD pumping include cooling of underground cables, transformers and similar electrical equipment. An EHD pump uses electric fields acting on electric charges embedded in a fluid to move that fluid. One way of setting up the free charges is induction charging, based on establishing an electrical conductivity gradient perpendicular to the desired direction of fluid motion. This gradient perpendicular to the desired direction of fluid motion. This gradient can be established in the presence of a temperature gradient. There are two basic kinds of induction EHD pump: attraction (forward) and repulsion (backward) pumps. In the attraction pump, the pipe is cooled at the wall, giving a negative electric conductivity gradient. In the repulsion pump, the pipe is heated at the wall, causing a positive electric conductivity gradient. In the attraction pump, the fluid is pumped in the same direction as the traveling electric wave. In this mode, the fluid velocity is limited by the speed of the moving electric field (synchronous speed), which depends on frequency and on the spacing of the electrodes (wavelength) along the channel. Unlike the attraction pump, a repulsion pump has no velocity limit. In the repulsion mode, the fluid is pumped in the opposite direction to the traveling electric wave.

  14. Multiple pump housing

    Science.gov (United States)

    Donoho, II, Michael R.; Elliott; Christopher M.

    2010-03-23

    A fluid delivery system includes a first pump having a first drive assembly, a second pump having a second drive assembly, and a pump housing. At least a portion of each of the first and second pumps are located in the housing.

  15. Types of Breast Pumps

    Science.gov (United States)

    ... breast-shield. Some experts discourage the use of bicycle horn pumps because they may be difficult to clean and dry. Battery-Powered and Electric Pumps A powered breast pump uses batteries or a cord plugged into an electrical outlet to power a small motorized pump that ...

  16. Adiabatic quantum pump in a zigzag graphene nanoribbon junction

    Institute of Scientific and Technical Information of China (English)

    张林

    2015-01-01

    The adiabatic electron transport is theoretically studied in a zigzag graphene nanoribbon (ZGNR) junction with two time-dependent pumping electric fields. By modeling a ZGNR p–n junction and applying the Keldysh Green’s function method, we find that a pumped charge current is flowing in the device at a zero external bias, which mainly comes from the photon-assisted tunneling process and the valley selection rule in an even-chain ZGNR junction. The pumped charge current and its ON and OFF states can be efficiently modulated by changing the system parameters such as the pumping frequency, the pumping phase difference, and the Fermi level. A ferromagnetic ZGNR device is also studied to generate a pure spin current and a fully polarized spin current due to the combined spin pump effect and the valley valve effect. Our finding might pave the way to manipulate the degree of freedom of electrons in a graphene-based electronic device.

  17. The Space Optical Clocks Project: Development of high-performance transportable and breadboard optical clocks and advanced subsystems

    CERN Document Server

    Schiller, S; Nevsky, A; Alighanbari, S; Vasilyev, S; Abou-Jaoudeh, C; Mura, G; Franzen, T; Sterr, U; Falke, S; Lisdat, Ch; Rasel, E; Kulosa, A; Bize, S; Lodewyck, J; Tino, G M; Poli, N; Schioppo, M; Bongs, K; Singh, Y; Gill, P; Barwood, G; Ovchinnikov, Y; Stuhler, J; Kaenders, W; Braxmaier, C; Holzwarth, R; Donati, A; Lecomte, S; Calonico, D; Levi, F

    2012-01-01

    The use of ultra-precise optical clocks in space ("master clocks") will allow for a range of new applications in the fields of fundamental physics (tests of Einstein's theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 program of ESA, the "Space Optical Clocks" (SOC) project aims to install and to operate an optical lattice clock on the ISS towards the end of this decade, as a natural follow-on to the ACES mission, improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Undertaking a necessary step towards optical clocks in space, the EU-FP7-SPACE-2...

  18. Clocks underneath: the role of peripheral clocks in the timing of female reproductive physiology

    Directory of Open Access Journals (Sweden)

    MichaelTSellix

    2013-07-01

    Full Text Available The central circadian pacemaker in the suprachiasmatic nucleus (SCN is a critical component of the neuroendocrine circuit controlling gonadotropin secretion from the pituitary gland. The SCN conveys photic information to hypothalamic targets including the gonadotropin releasing hormone (GnRH neurons. Many of these target cells are also cell autonomous clocks. It has been suggested that, rather then being singularly driven by the SCN, the timing of gonadotropin secretion depends on the activity of multiple hypothalamic oscillators. While this view provides a novel twist to an old story, it does little to diminish the central role of rhythmic hypothalamic output in this system. It is now clear that the pituitary, ovary, uterus and oviduct have functional molecular clocks. Evidence supports the notion that the clocks in these tissues contribute to the timing of events in reproductive physiology. The goal of this review is to highlight the current evidence for molecular clock function in the peripheral components of the female hypothalamo-pituitary-gonadal (HPG axis as it relates to the timing of gonadotropin secretion, ovulation and parturition.

  19. An association between clock genes and clock-controlled cell cycle genes in murine colorectal tumors

    Czech Academy of Sciences Publication Activity Database

    Soták, Matúš; Polidarová, Lenka; Ergang, Peter; Sumová, Alena; Pácha, Jiří

    2013-01-01

    Roč. 132, č. 5 (2013), s. 1032-1041. ISSN 0020-7136 R&D Projects: GA MZd(CZ) NS9982 Institutional research plan: CEZ:AV0Z50110509 Keywords : cancer * circadian rhythm * peripheral circadian clock Subject RIV: FE - Other Internal Medicine Disciplines Impact factor: 5.007, year: 2013

  20. Performance analysis of a complete adiabatic logic system driven by the proposed power clock generator

    International Nuclear Information System (INIS)

    We analyze the energy performance of a complete adiabatic circuit/system including the Power Clock Generator (PCG) at the 90 nm CMOS technology node. The energy performance in terms of the conversion efficiency of the PCG is extensively carried out under the variations of supply voltage, process corner and the driver transistor's width. We propose an energy-efficient singe cycle control circuit based on the two-stage comparator for the synchronous charge recovery sinusoidal power clock generator (PCG). The proposed PCG is used to drive the 4-bit adiabatic Ripple Carry Adder (RCA) and their simulation results are compared with the adiabatic RCA driven by the reported PCG. We have also simulated the logically equivalent static CMOS RCA circuit to compare the energy saving of adiabatic and non-adiabatic logic circuits. In the clock frequency range from 25 MHz to 1GHz, the proposed PCG gives a maximum conversion efficiency of 56.48%. This research work shows how the design of an efficient PCG increases the energy saving of adiabatic logic. (semiconductor integrated circuits)

  1. Polarizabilities of the beryllium clock transition

    International Nuclear Information System (INIS)

    The polarizabilities of the three lowest states of the beryllium atom are determined from a large basis configuration interaction calculation. The polarizabilities of the 2s21Se ground state (37.73a03) and the 2s2p 3P0o metastable state (39.04a03) are found to be very similar in size and magnitude. This leads to an anomalously small blackbody radiation shift at 300 K of -0.018(4) Hz for the 2s21Se-2s2p 3P0o clock transition. Magic wavelengths for simultaneous trapping of the ground and metastable states are also computed.

  2. Grand-mother clocks and quiet lasers

    OpenAIRE

    Arnaud, Jacques; Chusseau, Laurent; Philippe, Fabrice

    2009-01-01

    7 pages Galileo noted in the 16th century that the period of oscillation of a pendulum is almost independent of the amplitude. However, such a pendulum is damped by air friction. The latter may be viewed as resulting from air molecules getting in contact with the pendulum. It follows that air friction, not only damps the oscillation, but also introduces randomness. In the so-called ``grand-mother'' clock, discovered by Huygens in the 18th century, damping is compensated for, on the average...

  3. A precise clock distribution network for MRPC-based experiments

    Science.gov (United States)

    Wang, S.; Cao, P.; Shang, L.; An, Q.

    2016-06-01

    In high energy physics experiments, the MRPC (Multi-Gap Resistive Plate Chamber) detectors are widely used recently which can provide higher-resolution measurement for particle identification. However, the application of MRPC detectors leads to a series of challenges in electronics design with large number of front-end electronic channels, especially for distributing clock precisely. To deal with these challenges, this paper presents a universal scheme of clock transmission network for MRPC-based experiments with advantages of both precise clock distribution and global command synchronization. For precise clock distributing, the clock network is designed into a tree architecture with two stages: the first one has a point-to-multipoint long range bidirectional distribution with optical channels and the second one has a fan-out structure with copper link inside readout crates. To guarantee the precision of clock frequency or phase, the r-PTP (reduced Precision Time Protocol) and the DDMTD (digital Dual Mixer Time Difference) methods are used for frequency synthesis, phase measurement and adjustment, which is implemented by FPGA (Field Programmable Gate Array) in real-time. In addition, to synchronize global command execution, based upon this clock distribution network, synchronous signals are coded with clock for transmission. With technique of encoding/decoding and clock data recovery, signals such as global triggers or system control commands, can be distributed to all front-end channels synchronously, which greatly simplifies the system design. The experimental results show that both the clock jitter (RMS) and the clock skew can be less than 100 ps.

  4. Dopamine receptor-mediated regulation of neuronal "clock" gene expression.

    Science.gov (United States)

    Imbesi, M; Yildiz, S; Dirim Arslan, A; Sharma, R; Manev, H; Uz, T

    2009-01-23

    Using a transgenic mice model (i.e. "clock" knockouts), clock transcription factors have been suggested as critical regulators of dopaminergic behaviors induced by drugs of abuse. Moreover, it has been shown that systemic administration of psychostimulants, such as cocaine and methamphetamine regulates the striatal expression of clock genes. However, it is not known whether dopamine receptors mediate these regulatory effects of psychostimulants at the cellular level. Primary striatal neurons in culture express dopamine receptors as well as clock genes and have been successfully used in studying dopamine receptor functioning. Therefore, we investigated the role of dopamine receptors on neuronal clock gene expression in this model using specific receptor agonists. We found an inhibitory effect on the expression of mClock and mPer1 genes with the D2-class (i.e. D2/D3) receptor agonist quinpirole. We also found a generalized stimulatory effect on the expression of clock genes mPer1, mClock, mNPAS2 (neuronal PAS domain protein 2), and mBmal1 with the D1-class (i.e. D1) receptor agonist SKF38393. Further, we tested whether systemic administration of dopamine receptor agonists causes similar changes in striatal clock gene expression in vivo. We found quinpirole-induced alterations in mPER1 protein levels in the mouse striatum (i.e. rhythm shift). Collectively, our results indicate that the dopamine receptor system may mediate psychostimulant-induced changes in clock gene expression. Using striatal neurons in culture as a model, further research is needed to better understand how dopamine signaling modulates the expression dynamics of clock genes (i.e. intracellular signaling pathways) and thereby influences neuronal gene expression, neuronal transmission, and brain functioning. PMID:19017537

  5. Quantum optics and nuclear clocks: a look at the 2012 physics nobel prize

    International Nuclear Information System (INIS)

    Pioneering researches in the field of quantum optics are presented. These have laid the foundation for photonics research, that has grasped the particle properties of light to create new technologies and deepen the understanding of the physical laws. The quantum computation and quantum clocks have been highlighted. Individual particles have managed to manipulate without losing its properties in quantum, using photons to immobilize atoms with electric charges (ions) and study their properties. Researches conducted by the French scientist Serge Haroche and American David Wineland nobel prize winners for Physics 2012, have been commented

  6. δ-electron spectroscopy and the atomic clock effect in heavy-ion collisions

    International Nuclear Information System (INIS)

    The properties of strongly bound electrons in superheavy quasimolecular systems with combined nuclear charge numbers Z = ZP + ZT ≥ 110 are investigated. The emission of δ-electrons may serve as an atomic clock for nuclear reactions which is associated with the large overlap of the electron probability density with the nuclear interior. Excitation and emission rates of inner-shell electrons in collisions of very heavy ions with beam energies at or above the nuclear Coulomb barrier depend explicitly on details of the nuclear dynamics. Theoretical and experimental results are reviewed. (orig.)

  7. Study of a low power dissipation, miniature laser-pumped rubidium frequency standard

    Institute of Scientific and Technical Information of China (English)

    Liu Guo-Bin; Zhao Feng; Gu Si-Hong

    2009-01-01

    This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping 87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line,it records a 5×10-11τ-1/2 (τ<500 s) frequency stability with a table-top system in a primary experiment.The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption,90 cm3 volume and 10-12τ- 1/2 short-term frequency stability.

  8. NPAS2 Compensates for Loss of CLOCK in Peripheral Circadian Oscillators

    OpenAIRE

    Landgraf, Dominic; Wang, Lexie L.; Diemer, Tanja; Welsh, David K.

    2016-01-01

    Heterodimers of CLOCK and BMAL1 are the major transcriptional activators of the mammalian circadian clock. Because the paralog NPAS2 can substitute for CLOCK in the suprachiasmatic nucleus (SCN), the master circadian pacemaker, CLOCK-deficient mice maintain circadian rhythms in behavior and in tissues in vivo. However, when isolated from the SCN, CLOCK-deficient peripheral tissues are reportedly arrhythmic, suggesting a fundamental difference in circadian clock function between SCN and periph...

  9. Differentially pumped dual linear quadrupole ion trap mass spectrometer

    Science.gov (United States)

    Owen, Benjamin C.; Kenttamaa, Hilkka I.

    2015-10-20

    The present disclosure provides a new tandem mass spectrometer and methods of using the same for analyzing charged particles. The differentially pumped dual linear quadrupole ion trap mass spectrometer of the present disclose includes a combination of two linear quadrupole (LQIT) mass spectrometers with differentially pumped vacuum chambers.

  10. Ca2+-Clock-Dependent Pacemaking in the Sinus Node Is Impaired in Mice with a Cardiac Specific Reduction in SERCA2 Abundance

    Science.gov (United States)

    Logantha, Sunil Jit R. J.; Stokke, Mathis K.; Atkinson, Andrew J.; Kharche, Sanjay R.; Parveen, Sajida; Saeed, Yawer; Sjaastad, Ivar; Sejersted, Ole M.; Dobrzynski, Halina

    2016-01-01

    Background: The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) pump is an important component of the Ca2+-clock pacemaker mechanism that provides robustness and flexibility to sinus node pacemaking. We have developed transgenic mice with reduced cardiac SERCA2 abundance (Serca2 KO) as a model for investigating SERCA2's role in sinus node pacemaking. Methods and Results: In Serca2 KO mice, ventricular SERCA2a protein content measured by Western blotting was 75% (P clock with 2 μM ryanodine induced bradycardia that was less pronounced in Serca2 KO preparations (9 ± 1% vs. 20 ± 3% in Serca2 FF; P clock. Mathematical modeling was used to dissect the effects of membrane- and Ca2+-clock components on Serca2 KO mouse heart rate and sinus node action potential. Computer modeling predicted a slowing of heart rate with SERCA2 downregulation and the heart rate slowing was pronounced at >70% reduction in SERCA2 activity. Conclusions: Serca2 KO mice show a disrupted Ca2+-clock-dependent pacemaker mechanism contributing to impaired sinus node and atrioventricular node function.

  11. Hierarchical clustering of ryanodine receptors enables emergence of a calcium clock in sinoatrial node cells.

    Science.gov (United States)

    Stern, Michael D; Maltseva, Larissa A; Juhaszova, Magdalena; Sollott, Steven J; Lakatta, Edward G; Maltsev, Victor A

    2014-05-01

    The sinoatrial node, whose cells (sinoatrial node cells [SANCs]) generate rhythmic action potentials, is the primary pacemaker of the heart. During diastole, calcium released from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyRs) interacts with membrane currents to control the rate of the heartbeat. This "calcium clock" takes the form of stochastic, partially periodic, localized calcium release (LCR) events that propagate, wave-like, for limited distances. The detailed mechanisms controlling the calcium clock are not understood. We constructed a computational model of SANCs, including three-dimensional diffusion and buffering of calcium in the cytosol and SR; explicit, stochastic gating of individual RyRs and L-type calcium channels; and a full complement of voltage- and calcium-dependent membrane currents. We did not include an anatomical submembrane space or inactivation of RyRs, the two heuristic components that have been used in prior models but are not observed experimentally. When RyRs were distributed in discrete clusters separated by >1 µm, only isolated sparks were produced in this model and LCR events did not form. However, immunofluorescent staining of SANCs for RyR revealed the presence of bridging RyR groups between large clusters, forming an irregular network. Incorporation of this architecture into the model led to the generation of propagating LCR events. Partial periodicity emerged from the interaction of LCR events, as observed experimentally. This calcium clock becomes entrained with membrane currents to accelerate the beating rate, which therefore was controlled by the activity of the SERCA pump, RyR sensitivity, and L-type current amplitude, all of which are targets of β-adrenergic-mediated phosphorylation. Unexpectedly, simulations revealed the existence of a pathological mode at high RyR sensitivity to calcium, in which the calcium clock loses synchronization with the membrane, resulting in a paradoxical decrease in beating

  12. Pump element for a tube pump

    DEFF Research Database (Denmark)

    2011-01-01

    The invention relates to a tube pump comprising a tube and a pump element inserted in the tube, where the pump element comprises a rod element and a first and a second non-return valve member positioned a distance apart on the rod element. The valve members are oriented in the same direction...... portion acts to alternately close and open the valve members thereby generating a fluid flow through the tube. The invention further relates to a pump element comprising at least two non-return valve members connected by a rod element, and for insertion in an at least partly flexible tube in such tube...... pump as mentioned above, thereby acting to generate a fluid flow through the tube upon repeated deformation of the tube between the two valve members. The pump element may comprise a connecting part for coupling to another tube and may comprise a sealing part establishing a fluid tight connection to a...

  13. Hole Spin Pumping and Re-pumping in a p-type {\\delta}-doped InAs Quantum Dot

    OpenAIRE

    Lagoudakis, Konstantinos G.; Fischer, Kevin A.; Sarmiento, Tomas; Mueller, Kai; Vučković, Jelena

    2014-01-01

    We have grown high quality p-type {\\delta}-doped InAs quantum dots and have demonstrated coherent spin pumping and repumping of a hole spin in a positively charged quantum dot by means of a single-laser driving scheme under a high magnetic field in the Voigt configuration. Modeling of our system shows excellent qualitative agreement with the experimental findings and further explores the performance of the single-laser scheme for spin pumping and re-pumping.

  14. Oscillation of Clock and Clock Controlled Genes Induced by Serum Shock in Human Breast Epithelial and Breast Cancer Cells: Regulation by Melatonin

    OpenAIRE

    S. Xiang; Mao, L; T. Duplessis; Yuan, L.; R. Dauchy; Dauchy, E.; D.E. Blask,; T. Frasch; Hill, S M

    2012-01-01

    This study investigates differences in expression of clock and clock-controlled genes (CCGs) between human breast epithelial and breast cancer cells and breast tumor xenografts in circadian intact rats and examines if the pineal hormone melatonin influences clock gene and CCG expression. Oscillation of clock gene expression was not observed under standard growth conditions in vitro, however, serum shock (50% horse serum for 2 h) induced oscillation of clock gene and CCG expression in MCF-10A ...

  15. Real-time estimation of satellite clock offset using adaptively robust Kalman filter with classified adaptive factors

    OpenAIRE

    G Huang; Q. Zhang;  

    2012-01-01

    In order to estimate the satellite clock offset in a real-time mode, a new algorithm of adaptively robust Kalman filter with classified adaptive factors for clock offset estimation is proposed. Compared with standard Kalman filter clock offset model, the new method can detect and control outliers and clock jumps automatically in real-time. Moreover, the clock model parameters, which contain the clock offset, clock speed and clock shift, are classified to decide the adaptive factors in the new...

  16. Limits to clock synchronization induced by completely dephasing communication channels

    International Nuclear Information System (INIS)

    Clock synchronization procedures are analyzed in the presence of imperfect communications. In this context we show that there are physical limitations, which prevent one from synchronizing distant clocks when the intervening medium is completely dephasing, as in the case of a rapidly varying dispersive medium

  17. Atomic clocks: new prospects in metrology and geodesy

    CERN Document Server

    Delva, Pacôme

    2013-01-01

    We present the latest developments in the field of atomic clocks and their applications in metrology and fundamental physics. In the light of recent advents in the accuracy of optical clocks, we present an introduction to the relativistic modelization of frequency transfer and a detailed review of chronometric geodesy.

  18. Molecular clock integration of brown adipose tissue formation and function

    Science.gov (United States)

    Nam, Deokhwa; Yechoor, Vijay K.; Ma, Ke

    2016-01-01

    Abstract The circadian clock is an essential time-keeping mechanism that entrains internal physiology to environmental cues. Despite the well-established link between the molecular clock and metabolic homeostasis, an intimate interplay between the clock machinery and the metabolically active brown adipose tissue (BAT) is only emerging. Recently, we came to appreciate that the formation and metabolic functions of BAT, a key organ for body temperature maintenance, are under an orchestrated circadian clock regulation. Two complementary studies from our group uncover that the cell-intrinsic clock machinery exerts concerted control of brown adipogenesis with consequent impacts on adaptive thermogenesis, which adds a previously unappreciated temporal dimension to the regulatory mechanisms governing BAT development and function. The essential clock transcriptional activator, Bmal1, suppresses adipocyte lineage commitment and differentiation, whereas the clock repressor, Rev-erbα, promotes these processes. This newly discovered temporal mechanism in fine-tuning BAT thermogenic capacity may enable energy utilization and body temperature regulation in accordance with external timing signals during development and functional recruitment. Given the important role of BAT in whole-body metabolic homeostasis, pharmacological interventions targeting the BAT-modulatory activities of the clock circuit may offer new avenues for the prevention and treatment of metabolic disorders, particularly those associated with circadian dysregulation.

  19. Clocking in the face of unpredictability beyond quantum uncertainty

    Science.gov (United States)

    Madjid, F. Hadi; Myers, John M.

    2015-05-01

    In earlier papers we showed unpredictability beyond quantum uncertainty in atomic clocks, ensuing from a proven gap between given evidence and explanations of that evidence. Here we reconceive a clock, not as an isolated entity, but as enmeshed in a self-adjusting communications network adapted to one or another particular investigation, in contact with an unpredictable environment. From the practical uses of clocks, we abstract a clock enlivened with the computational capacity of a Turing machine, modified to transmit and to receive numerical communications. Such "live clocks" phase the steps of their computations to mesh with the arrival of transmitted numbers. We lift this phasing, known in digital communications, to a principle of logical synchronization, distinct from the synchronization defined by Einstein in special relativity. Logical synchronization elevates digital communication to a topic in physics, including applications to biology. One explores how feedback loops in clocking affect numerical signaling among entities functioning in the face of unpredictable influences, making the influences themselves into subjects of investigation. The formulation of communications networks in terms of live clocks extends information theory by expressing the need to actively maintain communications channels, and potentially, to create or drop them. We show how networks of live clocks are presupposed by the concept of coordinates in a spacetime. A network serves as an organizing principle, even when the concept of the rigid body that anchors a special-relativistic coordinate system is inapplicable, as is the case, for example, in a generic curved spacetime.

  20. The Circadian Clock-Controlled Transcriptome of Developing Soybean Seeds.

    Science.gov (United States)

    A number of metabolic and physiological processes in plants are controlled by the circadian clock, which enables the plant to anticipate daily changes in the environment. Microarray expression profiling was used to identify circadian clock controlled genes expressed in developing soybean seeds. 1.8...

  1. Optimal Infinite Runs in One-Clock Priced Timed Automata

    DEFF Research Database (Denmark)

    David, Alexandre; Ejsing-Duun, Daniel; Fontani, Lisa; Larsen, Kim Guldstrand; Popescu, Vasile; Haubach Smedegård, Jacob

    We address the problem of finding an infinite run with the optimal cost-time ratio in a one-clock priced timed automaton and pro- vide an algorithmic solution. Through refinements of the quotient graph obtained by strong time-abstracting bisimulation partitioning, we con- struct a graph with time...... of the one-clock priced timed automaton....

  2. Verge and Foliot Clock Escapement: A Simple Dynamical System

    Science.gov (United States)

    Denny, Mark

    2010-01-01

    The earliest mechanical clocks appeared in Europe in the 13th century. From about 1250 CE to 1670 CE, these simple clocks consisted of a weight suspended from a rope or chain that was wrapped around a horizontal axle. To tell time, the weight must fall with a slow uniform speed, but, under the action of gravity alone, such a suspended weight would…

  3. Circadian clock genes universally control key agricultural traits

    Science.gov (United States)

    Circadian clocks are endogenous timers that enable plants to synchronize biological processes with daily and seasonal environmental conditions in order to allocate resources during the most beneficial times of day and year. The circadian clock regulates a number of central plant activities, includin...

  4. Development and entrainment of the colonic circadian clock during ontogenesis

    Czech Academy of Sciences Publication Activity Database

    Polidarová, Lenka; Olejníková, Lucie; Paušlyová, Lucia; Sládek, Martin; Soták, Matúš; Pácha, Jiří; Sumová, Alena

    2014-01-01

    Roč. 306, č. 4 (2014), G346-G356. ISSN 0193-1857 R&D Projects: GA ČR(CZ) GAP303/12/1108 Institutional support: RVO:67985823 Keywords : circadian clock * clock gene * ontogenesis * circadian entrainment Subject RIV: ED - Physiology Impact factor: 3.798, year: 2014

  5. The circadian clock regulates auxin signaling and responses in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Michael F Covington

    2007-08-01

    Full Text Available The circadian clock plays a pervasive role in the temporal regulation of plant physiology, environmental responsiveness, and development. In contrast, the phytohormone auxin plays a similarly far-reaching role in the spatial regulation of plant growth and development. Went and Thimann noted 70 years ago that plant sensitivity to auxin varied according to the time of day, an observation that they could not explain. Here we present work that explains this puzzle, demonstrating that the circadian clock regulates auxin signal transduction. Using genome-wide transcriptional profiling, we found many auxin-induced genes are under clock regulation. We verified that endogenous auxin signaling is clock regulated with a luciferase-based assay. Exogenous auxin has only modest effects on the plant clock, but the clock controls plant sensitivity to applied auxin. Notably, we found both transcriptional and growth responses to exogenous auxin are gated by the clock. Thus the circadian clock regulates some, and perhaps all, auxin responses. Consequently, many aspects of plant physiology not previously thought to be under circadian control may show time-of-day-specific sensitivity, with likely important consequences for plant growth and environmental responses.

  6. The role of biological clock in glucose homeostasis 

    Directory of Open Access Journals (Sweden)

    Piotr Chrościcki

    2013-06-01

    Full Text Available The mechanism of the biological clock is based on a rhythmic expression of clock genes and clock-controlled genes. As a result of their transcripto-translational associations, endogenous rhythms in the synthesis of key proteins of various physiological and metabolic processes are created. The major timekeeping mechanism for these rhythms exists in the central nervous system. The master circadian clock, localized in suprachiasmatic nucleus (SCN, regulates multiple metabolic pathways, while feeding behavior and metabolite availability can in turn regulate the circadian clock. It is also suggested that in the brain there is a food entrainable oscillator (FEO or oscillators, resulting in activation of both food anticipatory activity and hormone secretion that control digestion processes. Moreover, most cells and tissues express autonomous clocks. Maintenance of the glucose homeostasis is particularly important for the proper function of the body, as this sugar is the main source of energy for the brain, retina, erythrocytes and skeletal muscles. Thus, glucose production and utilization are synchronized in time. The hypothalamic excited orexin neurons control energy balance of organism and modulate the glucose production and utilization. Deficiency of orexin action results in narcolepsy and weight gain, whereas glucose and amino acids can affect activity of the orexin cells. Large-scale genetic studies in rodents and humans provide evidence for the involvement of disrupted clock gene expression rhythms in the pathogenesis of obesity and type 2 diabetes. In general, the current lifestyle of the developed modern societies disturbs the action of biological clock

  7. A Novel Method of Clock Synchronization in Distributed System

    Science.gov (United States)

    Li, G.; Niu, M. J.; Cai, Y. S.; Chen, X.; Ren, Y. Q.

    2016-03-01

    Time synchronization plays an important role in application of aircraft flying formation and constellation autonomous navigation, etc. In application of clock synchronization in the network system, it is not always true that each observed node may be interconnected, therefore, it is difficult to achieve time synchronization of network system with high precision in the condition that a certain node can only obtain the measurement information of clock from one of its corresponding neighbors, and cannot obtain from other nodes. According to this special problem, a novel method of high precision time synchronization of network system has been proposed. In this paper, we regard each clock as a node in the network system, and based on different distributed topology definition, the following three control algorithms of time synchronization under three circumstances have been designed: without a master clock (reference clock), with a master clock (reference clock), and with a fixed communication delay in the network system. The validity of the designed clock synchronization protocol has been proved both theoretically and through numerical simulation.

  8. From atomic clocks to coordinate times

    Science.gov (United States)

    Petit, G.

    2006-08-01

    The IAU'1991 Resolution A4, complemented by IAU'2000 Resolution B1.3-4, provide rigorous definitions for barycentric and geocentric reference systems in a relativistic framework and define the coordinate times of these systems as TCB and TCG, respectively. Other coordinate times in use are TT, defined from TCG through IAU'2000 Resolution B1.9, and TDB, whose rigorous definition from TCB is now proposed. For practical use, these coordinate times must be realized and the proper time provided by atomic clocks (Atomic time AT) is used to generate all coordinate times. The present sequence is AT => TT ||> TCG -> TCB ||> TDB, where the sign => indicates the complex series of operations involved in generating International atomic time TAI and where ||> is an exact transformation. The paper examines the uncertainty of realization of TAI and the uncertainty brought by the transformation TCG -> TCB. On-going and future evolutions of atomic clocks are reviewed along with their impact on the diagram of time transformations.

  9. Animal clocks: when science meets nature.

    Science.gov (United States)

    Kronfeld-Schor, Noga; Bloch, Guy; Schwartz, William J

    2013-08-22

    Daily rhythms of physiology and behaviour are governed by an endogenous timekeeping mechanism (a circadian 'clock'), with the alternation of environmental light and darkness synchronizing (entraining) these rhythms to the natural day-night cycle. Our knowledge of the circadian system of animals at the molecular, cellular, tissue and organismal levels is remarkable, and we are beginning to understand how each of these levels contributes to the emergent properties and increased complexity of the system as a whole. For the most part, these analyses have been carried out using model organisms in standard laboratory housing, but to begin to understand the adaptive significance of the clock, we must expand our scope to study diverse animal species from different taxonomic groups, showing diverse activity patterns, in their natural environments. The seven papers in this Special Feature of Proceedings of the Royal Society B take on this challenge, reviewing the influences of moonlight, latitudinal clines, evolutionary history, social interactions, specialized temporal niches, annual variation and recently appreciated post-transcriptional molecular mechanisms. The papers emphasize that the complexity and diversity of the natural world represent a powerful experimental resource. PMID:23825215

  10. The clock ambiguity: Implications and new developments

    CERN Document Server

    Albrecht, Andreas

    2008-01-01

    We consider the ambiguity associated with the choice of clock in time reparameterization invariant theories. This arbitrariness undermines the goal of prescribing a fixed set of physical laws, since a change of time variable can completely alter the predictions of the theory. We review the main features of the clock ambiguity and our earlier work on its implications for the emergence of physical laws in a statistical manner. We also present a number of new results: We show that (contrary to suggestions in our earlier work) time independent Hamiltonians may quite generally be assumed for laws of physics that emerge in this picture. We also further explore the degree to which the observed Universe can be well approximated by a random Hamiltonian. We discuss the possibility of predicting the dimensionality of space, and also relate the 2nd derivative of the density of states to the heat capacity of the Universe. This new work adds to the viability of our proposal that strong predictions for physical laws may eme...

  11. An Integrated Architectural Clock Implemented Memory Design Analysis

    Directory of Open Access Journals (Sweden)

    Ravi Khatwal

    2015-07-01

    Full Text Available Recently Low power consumption and Custom Memory design is major issue for embedded designer. Micro wind and Xilinx simulator implements SRAM design architecture and performs efficient simulation. These simulators implements high performances and low power consumption of SRAM design. SRAM efficiency analyzed with 6-T architecture design and row/column based architectural design. We have analyzed clock implemented memory design and simulated with specific application. We have implemented clock based SRAM architecture that improves the internal clock efficiency of SRAM. Architectural Clock implemented memory design reduces the propagation delay and access time. Internal semiconductor material design implemented technique also improves the SRAM data transitions scheme. Semiconductor material and clock implemented design improve simulation performance of SRAM and these design implements for recently developed Application Specific Memory Design Architecture and mobile devices.

  12. Multiple-bit-rate clock recovery circuit: theory

    International Nuclear Information System (INIS)

    The multiple-bit-rate clock recovery circuit has been recently proposed as a part of the communications packet switch. All packets must be the same length and be preceded by the frequency header, which is a number of consecutive ones (return-to-zero mode). The header is compared with the internal clock, and the result is used to set output clock frequency. The clock rate is defined by a number of fluxons propagating in ring oscillator, which is a close circular Josephson transmission line. The theory gives a bit rate bandwidth as a function of internal clock frequency, header length and silence time (maximum number of consecutive zeros in the packet). (author)

  13. Standard Clock in primordial density perturbations and cosmic microwave background

    International Nuclear Information System (INIS)

    Standard Clocks in the primordial epoch leave a special type of features in the primordial perturbations, which can be used to directly measure the scale factor of the primordial universe as a function of time a(t), thus discriminating between inflation and alternatives. We have started to search for such signals in the Planck 2013 data using the key predictions of the Standard Clock. In this Letter, we summarize the key predictions of the Standard Clock and present an interesting candidate example in Planck 2013 data. Motivated by this candidate, we construct and compute full Standard Clock models and use the more complete prediction to make more extensive comparison with data. Although this candidate is not yet statistically significant, we use it to illustrate how Standard Clocks appear in Cosmic Microwave Background (CMB) and how they can be further tested by future data. We also use it to motivate more detailed theoretical model building

  14. Clock-turning gait synthesis for humanoid robots

    Institute of Scientific and Technical Information of China (English)

    Zhe TANG; Zengqi SUN; Hongbo LIU; Meng Joo ER

    2007-01-01

    Turning gait is a basic motion for humanoid robots.This paper presents a method for humanoid turning.i.e.clock-turning.The objective of clock-turning is to change robot direction at a stationary spot.The clock-turning planning consists of four steps:ankle trajectory generation,hip trajectory generation,knee trajectory generation,and inverse kinematics calculation.Our proposed method is based on a typical humanoid structure with 12 DOFs(degrees of freedom).The final output of clock-turning planning is 12 reference trajectories.which are used to control a humanoid robot wim 12 DOFs.ZMP(zero moment point)is used as stability criterion for the planning.Simulation experiments are conducted to verify the effectiveness of our proposed clock-turning method.

  15. A self-interfering clock as a "which path" witness.

    Science.gov (United States)

    Margalit, Yair; Zhou, Zhifan; Machluf, Shimon; Rohrlich, Daniel; Japha, Yonathan; Folman, Ron

    2015-09-11

    In Einstein's general theory of relativity, time depends locally on gravity; in standard quantum theory, time is global-all clocks "tick" uniformly. We demonstrate a new tool for investigating time in the overlap of these two theories: a self-interfering clock, comprising two atomic spin states. We prepare the clock in a spatial superposition of quantum wave packets, which evolve coherently along two paths into a stable interference pattern. If we make the clock wave packets "tick" at different rates, to simulate a gravitational time lag, the clock time along each path yields "which path" information, degrading the pattern's visibility. In contrast, in standard interferometry, time cannot yield "which path" information. This proof-of-principle experiment may have implications for the study of time and general relativity and their impact on fundamental effects such as decoherence and the emergence of a classical world. PMID:26249229

  16. Geophysical applicability of atomic clocks: direct continental geoid mapping

    CERN Document Server

    Bondarescu, Ruxandra; Hetényi, György; Boschi, Lapo; Jetzer, Philippe; Balakrishna, Jayashree; 10.1111/j.1365-246X.2012.05636.x

    2012-01-01

    The geoid is the true physical figure of the Earth, a particular equipotential surface of the gravity field of the Earth that accounts for the effect of all subsurface density variations. Its shape approximates best (in the sense of least squares) the mean level of oceans, but the geoid is more difficult to determine over continents. Satellite missions carry out distance measurements and derive the gravity field to provide geoid maps over the entire globe. However, they require calibration and extensive computations including integration, which is a non-unique operation. Here we propose a direct method and a new tool that directly measures geopotential differences on continents using atomic clocks. General Relativity Theory predicts constant clock rate at sea level, and faster (resp. slower) clock rate above (resp. below) sea level. The technology of atomic clocks is on the doorstep of reaching an accuracy level in clock rate that is equivalent to 1 cm in determining equipotential surface (including geoid) he...

  17. Gastrostomy feeding tube - pump - child

    Science.gov (United States)

    Feeding - gastrostomy tube - pump; G-tube - pump; Gastrostomy button - pump; Bard Button - pump; MIC-KEY - pump ... Gather supplies: Feeding pump (electronic or battery powered) Feeding set that matches the feeding pump (includes a feeding bag, drip chamber, roller clamp, ...

  18. Tritium gas transfer pump development

    International Nuclear Information System (INIS)

    Non-lubricated, hermetically sealed pumps for tritium service have been selected to replace Sprengel pumps in the existing Tritium Facility. These pumps will be the primary gas-transfer pumps in the planned Replacement Tritium Facility. The selected pumps are Metal Bellows Corporation's bellows pumps and Normetex scroll pumps. Pumping range for a Normetex/Metal Bellows system is from 0.01 torr suction to 2300 torr discharge. Performance characteristics of both pumps are presented. 10 figs

  19. The Retina and Other Light-sensitive Ocular Clocks.

    Science.gov (United States)

    Besharse, Joseph C; McMahon, Douglas G

    2016-06-01

    Ocular clocks, first identified in the retina, are also found in the retinal pigment epithelium (RPE), cornea, and ciliary body. The retina is a complex tissue of many cell types and considerable effort has gone into determining which cell types exhibit clock properties. Current data suggest that photoreceptors as well as inner retinal neurons exhibit clock properties with photoreceptors dominating in nonmammalian vertebrates and inner retinal neurons dominating in mice. However, these differences may in part reflect the choice of circadian output, and it is likely that clock properties are widely dispersed among many retinal cell types. The phase of the retinal clock can be set directly by light. In nonmammalian vertebrates, direct light sensitivity is commonplace among body clocks, but in mice only the retina and cornea retain direct light-dependent phase regulation. This distinguishes the retina and possibly other ocular clocks from peripheral oscillators whose phase depends on the pace-making properties of the hypothalamic central brain clock, the suprachiasmatic nuclei (SCN). However, in mice, retinal circadian oscillations dampen quickly in isolation due to weak coupling of its individual cell-autonomous oscillators, and there is no evidence that retinal clocks are directly controlled through input from other oscillators. Retinal circadian regulation in both mammals and nonmammalian vertebrates uses melatonin and dopamine as dark- and light-adaptive neuromodulators, respectively, and light can regulate circadian phase indirectly through dopamine signaling. The melatonin/dopamine system appears to have evolved among nonmammalian vertebrates and retained with modification in mammals. Circadian clocks in the eye are critical for optimum visual function where they play a role fine tuning visual sensitivity, and their disruption can affect diseases such as glaucoma or retinal degeneration syndromes. PMID:27095816

  20. Large electromagnetic pumps. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Kilman, G.B.

    1976-01-01

    The development of large electromagnetic pumps for the liquid metal heat transfer systems of fission reactors has progressed for a number of years. Such pumps are now planned for fusion reactors and solar plants as well. The Einstein-Szilard (annular) pump has been selected as the preferred configuration. Some of the reasons that electromagnetic pumps may be preferred over mechanical pumps and why the annular configuration was selected are discussed. A detailed electromagnetic analysis of the annular pump, based on slug flow, is presented. The analysis is then used to explore the implications of large size and power on considerations of electromagnetic skin effect, geometric skin effect and the cylindrical geometry.

  1. The eCDR-PLL, a radiation-tolerant ASIC for clock and data recovery and deterministic phase clock synthesis

    International Nuclear Information System (INIS)

    A radiation-tolerant CDR/PLL ASIC has been developed for the upcoming LHC upgrades, featuring clock Frequency Multiplication (FM) and Clock and Data Recovery (CDR), showing deterministic phase and low jitter. Two FM modes have been implemented: either generating 40, 60, 120 and 240 MHz clock outputs for GBT-FPGA applications or providing 40, 80, 160 and 320 MHz clocks for TTC and e-link applications. The CDR operates with 40, 80, 160 or 320 Mbit/s data rates while always generating clocks at 40, 80, 160 and 320 MHz, regardless of the data rate. All the outputs are phase programmable with a resolution of 195 ps or 260 ps, depending on the selected mode. The ASIC has been designed using radiation-tolerant techniques in a 130 nm CMOS technology and operates at a 1.2 V supply voltage

  2. Non-adiabatic pumping through interacting quantum dots

    OpenAIRE

    Cavaliere, Fabio; Governale, Michele; König, Jürgen

    2009-01-01

    We study non-adiabatic two-parameter charge and spin pumping through a single-level quantum dot with Coulomb interaction. For the limit of weak tunnel coupling and in the regime of pumping frequencies up to the tunneling rates, $\\Omega \\lesssim \\Gamma/\\hbar$, we perform an exact resummation of contributions of all orders in the pumping frequency. As striking non-adiabatic signatures, we find frequency-dependent phase shifts in the charge and spin currents, which allow for an effective single-...

  3. Insulin pump (image)

    Science.gov (United States)

    The catheter at the end of the insulin pump is inserted through a needle into the abdominal ... with diabetes. Dosage instructions are entered into the pump's small computer and the appropriate amount of insulin ...

  4. Proton pump inhibitors

    Science.gov (United States)

    Proton pump inhibitors (PPIs) are medicines that work by reducing the amount of stomach acid made by glands in ... Proton pump inhibitors are used to: Relieve symptoms of acid reflux, or gastroesophageal reflux disease (GERD). This is a ...

  5. Proton pump inhibitors

    Science.gov (United States)

    Proton pump inhibitors (PPIs) are medicines that work by reducing the amount of stomach acid made by ... Proton pump inhibitors are used to: Relieve symptoms of acid reflux, or gastroesophageal reflux disease (GERD). This ...

  6. Clocks for quaternary environments in Australia

    International Nuclear Information System (INIS)

    The Australian continent offers a variety of natural systems where records of the Earth's past environment have been stored, including sediment cores, tree rings, rock surfaces and corals. Rock varnish, mud-wasp nests and pack-rat middens provide alternative archives for vegetation and environmental change in arid areas, where continuous sedimentary sequences or trees are not available. Each of these media contain specific information on past climatic conditions but we must determine their chronology and decipher the relevant environmental parameters. Cosmogenic radionuclides, such as 14C, 10Be, 26Al and 36Cl, analysed by accelerator mass spectrometry, provide valuable radiometric clocks to establish an absolute time scale for the environmental events of the Quaternary. U-series, potassium-argon, argonargon and optically stimulated luminescence are other dating methods used in palaeoenvironmental studies. ANSTO supports the Quaternary science community in Australia providing the analysis of long-lived radionuclides: some significant projects from this program will be illustrated. (author)

  7. The Information Flow Problem on Clock Networks

    OpenAIRE

    Atkins, Ross

    2016-01-01

    The information flow problem on a network asks whether $r$ senders, $v_1,v_2, \\ldots ,v_r$ can each send messages to $r$ corresponding receivers $v_{n+1}, \\ldots ,v_{n+r}$ via intermediate nodes $v_{r+1}, \\ldots ,v_n$. For a given finite $R \\subset \\mathbb{Z}^+$, the clock network $N_n(R)$ has edge $v_iv_k$ if and only if $k>r$ and $k-i \\in R$. We show that the information flow problem on $N_n(\\{1,2, \\ldots ,r\\})$ can be solved for all $n \\geq r$. We also show that for any finite $R$ such tha...

  8. Somitogenesis clock-wave initiation requires differential decay and multiple binding sites for clock protein.

    Directory of Open Access Journals (Sweden)

    Mark Campanelli

    2010-04-01

    Full Text Available Somitogenesis is a process common to all vertebrate embryos in which repeated blocks of cells arise from the presomitic mesoderm (PSM to lay a foundational pattern for trunk and tail development. Somites form in the wake of passing waves of periodic gene expression that originate in the tailbud and sweep posteriorly across the PSM. Previous work has suggested that the waves result from a spatiotemporally graded control protein that affects the oscillation rate of clock-gene expression. With a minimally constructed mathematical model, we study the contribution of two control mechanisms to the initial formation of this gene-expression wave. We test four biologically motivated model scenarios with either one or two clock protein transcription binding sites, and with or without differential decay rates for clock protein monomers and dimers. We examine the sensitivity of wave formation with respect to multiple model parameters and robustness to heterogeneity in cell population. We find that only a model with both multiple binding sites and differential decay rates is able to reproduce experimentally observed waveforms. Our results show that the experimentally observed characteristics of somitogenesis wave initiation constrain the underlying genetic control mechanisms.

  9. Photovoltaic pump systems

    Science.gov (United States)

    Klockgether, J.; Kiessling, K. P.

    1983-09-01

    Solar pump systems for the irrigation of fields and for water supply in regions with much sunshine are discussed. For surface water and sources with a hoisting depth of 12 m, a system with immersion pumps is used. For deep sources with larger hoisting depths, an underwater motor pump was developed. Both types of pump system meet the requirements of simple installation and manipulation, safe operation, maintenance free, and high efficiency reducing the number of solar cells needed.

  10. Diurnal oscillations of soybean circadian clock and drought responsive genes.

    Directory of Open Access Journals (Sweden)

    Juliana Marcolino-Gomes

    Full Text Available Rhythms produced by the endogenous circadian clock play a critical role in allowing plants to respond and adapt to the environment. While there is a well-established regulatory link between the circadian clock and responses to abiotic stress in model plants, little is known of the circadian system in crop species like soybean. This study examines how drought impacts diurnal oscillation of both drought responsive and circadian clock genes in soybean. Drought stress induced marked changes in gene expression of several circadian clock-like components, such as LCL1-, GmELF4- and PRR-like genes, which had reduced expression in stressed plants. The same conditions produced a phase advance of expression for the GmTOC1-like, GmLUX-like and GmPRR7-like genes. Similarly, the rhythmic expression pattern of the soybean drought-responsive genes DREB-, bZIP-, GOLS-, RAB18- and Remorin-like changed significantly after plant exposure to drought. In silico analysis of promoter regions of these genes revealed the presence of cis-elements associated both with stress and circadian clock regulation. Furthermore, some soybean genes with upstream ABRE elements were responsive to abscisic acid treatment. Our results indicate that some connection between the drought response and the circadian clock may exist in soybean since (i drought stress affects gene expression of circadian clock components and (ii several stress responsive genes display diurnal oscillation in soybeans.

  11. Automatic minimisation of micromotion in a 88Sr+ optical clock

    International Nuclear Information System (INIS)

    Optical clocks based on narrow linewidth transitions in single cold ions confined in RF traps are being developed at a number of laboratories worldwide. For these ion clock systems, excess micromotion can cause both Stark and Doppler frequency shifts and also a degradation of frequency stability as a result of a reduced excitation rate to the clock transition. At NPL, we detect micromotion in our 88Sr+ optical clocks by observing the correlation between photon arrival times and the zero crossing of the RF trap drive signal. Recently, two nominally identical 88Sr+ optical clocks have been operated over several days and their frequencies compared against one another. During this time the dc voltages on the endcap and compensation voltage electrodes required to minimise the micromotion can change significantly, particularly following the loading of an ion. This paper describes an automatic method to monitor and minimise micromotion applicable to single ion clocks and which we demonstrate using our two NPL 88Sr+ ion clocks. (paper)

  12. Circadian clock and the onset of cardiovascular events.

    Science.gov (United States)

    Takeda, Norihiko; Maemura, Koji

    2016-06-01

    The onset of cardiovascular diseases often shows time-of-day variation. Acute myocardial infarction or ventricular arrhythmia such as ventricular tachycardia occurs mainly in the early morning. Multiple biochemical and physiological parameters show circadian rhythm, which may account for the diurnal variation of cardiovascular events. These include the variations in blood pressure, activity of the autonomic nervous system and renin-angiotensin axis, coagulation cascade, vascular tone and the intracellular metabolism of cardiomyocytes. Importantly, the molecular clock system seems to underlie the circadian variation of these parameters. The center of the biological clock, also known as the central clock, exists in the suprachiasmatic nucleus. In contrast, the molecular clock system is also activated in each cell of the peripheral organs and constitute the peripheral clock. The biological clock system is currently considered to have a beneficial role in maintaining the homeostasis of each organ. Discoordination, however, between the peripheral clock and external environment could potentially underlie the development of cardiovascular events. Therefore, understanding the molecular and cellular pathways by which cardiovascular events occur in a diurnal oscillatory pattern will help the establishment of a novel therapeutic approach to the management of cardiovascular disorders. PMID:26888119

  13. Caenorhabditis elegans opens up new insights into circadian clock mechanisms.

    Science.gov (United States)

    Hasegawa, Kenji; Saigusa, Tetsu; Tamai, Yoichi

    2005-01-01

    The roundworm, Caenorhabditis elegans, is known to carry homologues of clock genes such as per (=period) and tim (=timeless), which constitute the core of the circadian clock in Drosophila and mammals: lin-42 and tim-1. Analyses using WormBase (C. elegans gene database) have identified with relatively high identity analogous of the clock genes recognized in Drosophila and mammals, with the notable exception of cry (=cryptochrome), which is lacking in C. elegans. All of these C. elegans cognates of the clock genes appear to belong to members of the PAS-superfamily and to participate in development or responsiveness to the environment but apparently are not involved in the C. elegans circadian clock. Nevertheless, C. elegans exhibits convincing circadian rhythms in locomotor behavior in the adult stage and in resistance to hyperosmotic stress in starved larvae (L1) after hatching, indicating that it has a circadian clock with a core design entirely different from that of Drosophila and mammals. Here two possibilities are considered. First, the core of the C. elegans circadian clock includes transcriptional/translational feedback loops between genes and their protein products that are entirely different from those of Drosophila and mammals. Second, a more basic principle such as homeostasis governs the circadian cellular physiology, and was established primarily to minimize the accumulation of DNA damage in response to an environment cycling at 24 h intervals. PMID:15865318

  14. A molecular clock regulates angiopoietin-like protein 2 expression.

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Kadomatsu

    Full Text Available Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2 contributes to the pathogenesis of these lifestyle-related diseases by inducing chronic inflammation. However, molecular mechanisms underlying regulation of ANGPTL2 expression are poorly understood. Here, we assess circadian rhythmicity of ANGPTL2 expression in various mouse tissues. We observed that ANGPTL2 rhythmicity was similar to that of the PER2 gene, which is regulated by the CLOCK/BMAL1 complex. Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression. We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells. Furthermore, Cry-deficient mice exhibited arrhythmic Angptl2 expression. Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

  15. Automatic minimisation of micromotion in a 88Sr+ optical clock

    Science.gov (United States)

    Barwood, G. P.; Huang, G.; Klein, H. A.; Gill, P.

    2015-07-01

    Optical clocks based on narrow linewidth transitions in single cold ions confined in RF traps are being developed at a number of laboratories worldwide. For these ion clock systems, excess micromotion can cause both Stark and Doppler frequency shifts and also a degradation of frequency stability as a result of a reduced excitation rate to the clock transition. At NPL, we detect micromotion in our 88Sr+ optical clocks by observing the correlation between photon arrival times and the zero crossing of the RF trap drive signal. Recently, two nominally identical 88Sr+ optical clocks have been operated over several days and their frequencies compared against one another. During this time the dc voltages on the endcap and compensation voltage electrodes required to minimise the micromotion can change significantly, particularly following the loading of an ion. This paper describes an automatic method to monitor and minimise micromotion applicable to single ion clocks and which we demonstrate using our two NPL 88Sr+ ion clocks.

  16. The Bird of Time: Cognition and the Avian Biological Clock

    Directory of Open Access Journals (Sweden)

    Vincent Michael Cassone

    2012-03-01

    Full Text Available Avian behavior and physiology are embedded in time at many levels of biological organization. Biological clock function in birds is critical for sleep/wake cycles, but may also regulate the acquisition of place memory, learning of song from tutors, social integration and time-compensated navigation. This relationship has two major implications. First, mechanisms of the circadian clock should be linked in some way to the mechanisms of all these behaviors. How is not yet clear, and evidence that the central clock has effects is piecemeal. Second, selection acting on characters that are linked to the circadian clock should influence aspects of the clock mechanism itself. Little evidence exists for this in birds, but there have been few attempts to assess this idea. At its core, the avian circadian clock is a multi-oscillator system comprising the pineal gland, the retinae and the avian homologues of the suprachiasmatic nuclei, whose mutual interactions ensure coordinated physiological functions, which are in turn synchronized to ambient light cycles via encephalic, pineal and retinal photoreceptors. At the molecular level, avian biological clocks comprise a genetic network of positive elements clock and bmal1 whose interactions with the negative elements period2, period3 and the cryptochromes form an oscillatory feedback loop that circumnavigates the 24 hrs of the day. We assess the possibilities for dual integration of the clock with time-dependent cognitive processes. Closer examination of the molecular, physiological, and behavioral elements of the circadian system would place birds at a very interesting fulcrum in the neurobiology of time in learning, memory and navigation. 

  17. Using a transportable optical clock for chronometric levelling

    Science.gov (United States)

    Lisdat, Christian; Sterr, Uwe; Koller, Silvio; Grotti, Jacopo; Vogt, Stefan; Häfner, Sebastian; Herbers, Sofia; Al-Masoudi, Ali

    2016-07-01

    With their supreme accuracy and precision, optical clocks in combination with new methods of long-distance frequency transfer can be used to determine height differences by measuring the gravitational red shift between two clocks without accumulation of measurement errors, as in classical levelling. We are developing transportable optical clocks for this purpose that will also serve for the technology development regarding optical clocks in Space and for international comparisons between optical clocks that cannot be linked with sufficient accuracy otherwise. In this talk we will focus on the transportable strontium lattice clock that we are developing and its first evaluation. Presently, we achieve a fractional frequency instability of 3 × 10^{-17} after 1000 s averaging time, which is equivalent to a height resolution of 30 cm. The first uncertainty evaluation of the system yielded 7 × 10^{-17}. We expect rapid improvements to an uncertainty of a few parts in 10^{17}. The clock is now located within a car trailer, which requires compact and rugged lasers systems and physics package. Special care has been taken in the design of the ultra-frequency stable interrogation laser that has to achieve fractional frequency instabilities of considerably below 10^{-15}. Typical laboratory constructions of the reference resonator system used to pre-stabilize the laser frequency are not compatible with the requirement of transportability. In an actual levelling campaign, this clock will be connected via a stabilized optical fibre link with another, stationary frequency standard. The measured gravitational red shift will be compared with the ones calculated from potential differences derived with state of the art geodetic data and models. We will discuss the status of measurements of geodetic relevance with optical clocks and give an outlook on our next steps. This work is supported by QUEST, DFG (RTG 1729, CRC 1128), EU-FP7 (FACT) and EMRP (ITOC). The EMRP is jointly funded

  18. Breast milk - pumping and storing

    Science.gov (United States)

    ... a comfortable chair, sink, and electric pump. If pumping at work is going to be hard, build ... up your milk supply. Wash your hands before pumping. Collect breast milk when pumping. You can use: ...

  19. The auxiliary system design retrofits of the different coolant pump

    International Nuclear Information System (INIS)

    The coolant pump auxiliary systems retrofits are introduced in detail according to the different type of coolant pumps. The retrofit reasons of the chemical and volume control system, component cooling water system, Nuclear Nitrogen Storage and Distribution System, Vent and drain system, etc. are investigated. The most extraordinary change takes place in the chemical and volume control system and cooling water system. The charging flow temperature of re- generative heat exchanger and discharge flow of charging pump will be changed according to the difference coolant pump seal flow distribution. The commercial CFD software Flow master is employed to validate the charging capability. The other auxiliary systems' retrofits are also introduced in the end of this paper. (authors)

  20. Interactions of charged dust particles in clouds of charges

    Science.gov (United States)

    Gundienkov, Vladimir; Yakovlenko, Sergey

    2004-03-01

    Two charged dust particles inside a cloud of charges are considered as Debye atoms forming a Debye molecule. Cassini coordinates are used for the numerical solution of the Poisson-Boltzmann equation for the charged cloud. The electric force acting on a dust particle by the other dust particle was determined by integrating the electrostatic pressure on the surface of the dust particle. It is shown that attractive forces appear when the following two conditions are satisfied. First, the average distance between dust particles should be approximately equal to two Debye radii. Second, attraction takes place when similar charges are concentrated predominantly on the dust particles. If the particles carry a small fraction of total charge of the same polarity, repulsion between the particles takes place at all distances. We apply our results to the experiments with thermoemission plasma and to the experiments with nuclear-pumped plasma.

  1. Time in the 10,000-Year Clock

    OpenAIRE

    Hillis, Danny; Seaman, Rob; Allen, Steve; Giorgini, Jon

    2011-01-01

    The Long Now Foundation is building a mechanical clock that is designed to keep time for the next 10,000 years. The clock maintains its long-term accuracy by synchronizing to the Sun. The 10,000-Year Clock keeps track of five different types of time: Pendulum Time, Uncorrected Solar Time, Corrected Solar Time, Displayed Solar Time and Orrery Time. Pendulum Time is generated from the mechanical pendulum and adjusted according to the equation of time to produce Uncorrected Solar Time, which is ...

  2. Progress Towards a Compact Optical Clock at JPL

    Science.gov (United States)

    Sullivan, Scott; Rellergert, Wade; Grudinin, Ivan; Baumgartel, Lukas; Yu, Nan

    2014-05-01

    The unprecedented stability and accuracy provided by optical clocks allows improved navigation and planetary science in space applications as well as more precise tests of fundamental laws of physics. However, technological advances towards the miniaturization of the physical volume and reduced power consumption of these clocks must be made to suit space-based application. We will describe JPL's effort towards the development of a compact, low-power optical clock based on 171Yb+. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Partial support from NASA Fundamental Physics Program is acknowledged.

  3. Relativistic effects for the JUICE on‐board clock

    OpenAIRE

    S. Bauer; Hussmann, H.; J. Mueller; Oberst, J.

    2014-01-01

    We studied relativistic effects on spacecraft clock rates for ESA’s JUICE mission and derived a relationship between dynamical time TDB and on‐board time. We analysed the S/C on‐board clock rate by using the JUICE mission nominal trajectory. We identify significant changes in the rate of the clock due to large changes of the S/C velocity and its distance to the solar system bodies during the various spacecraft operational phases. After ≈ 11.5 years, at the end of the mission, the offset in ti...

  4. Stimulated Raman clock transition without a differential ac Stark

    International Nuclear Information System (INIS)

    We considered a stimulated Raman clock transition between the ground hyperfine states of an alkali atom by using the second-order perturbation theory and the spherical tensor formalism. When the light fields are circularly polarized and properly detuned, the differential ac Stark shift of the clock transition vanishes with non-vanishing transition amplitude. With a two-zone Raman Ramsey method and a slow atomic beam, the proposed scheme should result in a clock with a systematic shift of the order of a few mHz for the case of cesium. (author)

  5. Magic Wavelength of an Optical Clock Transition of Barium

    International Nuclear Information System (INIS)

    Similar to most of the other alkaline earth elements, barium atoms can be candidates for optical clocks, thus the magic wavelength for an optical lattice is important for the clock transition. We calculate the magic wavelength of a possible clock transition between 6s21S0 and 6s5d3 D2 states of barium atoms. Our theoretical result shows that there are three magic wavelengths 615.9nm, 641.2nm and 678.8nm for a linearly polarized optical lattice laser for barium. (atomic and molecular physics)

  6. Circadian Clocks as Modulators of Metabolic Comorbidity in Psychiatric Disorders.

    Science.gov (United States)

    Barandas, Rita; Landgraf, Dominic; McCarthy, Michael J; Welsh, David K

    2015-12-01

    Psychiatric disorders such as schizophrenia, bipolar disorder, and major depressive disorder are often accompanied by metabolic dysfunction symptoms, including obesity and diabetes. Since the circadian system controls important brain systems that regulate affective, cognitive, and metabolic functions, and neuropsychiatric and metabolic diseases are often correlated with disturbances of circadian rhythms, we hypothesize that dysregulation of circadian clocks plays a central role in metabolic comorbidity in psychiatric disorders. In this review paper, we highlight the role of circadian clocks in glucocorticoid, dopamine, and orexin/melanin-concentrating hormone systems and describe how a dysfunction of these clocks may contribute to the simultaneous development of psychiatric and metabolic symptoms. PMID:26483181

  7. High speed fiber-based clock enhancement of NRZ data

    Institute of Scientific and Technical Information of China (English)

    Tong Wu; Kun Qiu

    2005-01-01

    A scheme for all-fiber clock enhancement of non-return-to-zero (NRZ) data based on cross-phase modulation (XPM) effect in nonlinear fibers is proposed and demonstrated in simulation. The simulation results indicate that the clock-to-data ratio of NRZ signals at 64 Gb/s can be increased to 22.94 dB by using this scheme, and the pattern effect in clock enhanced signals is very weak. The ability of high speed operation up to 140 Gb/s of this scheme is also proved in our simulation.

  8. Deionization and desalination using electrostatic ion pumping

    Science.gov (United States)

    Bourcier, William L.; Aines, Roger D.; Haslam, Jeffery J.; Schaldach, Charlene M.; O& #x27; Brien, Kevin C.; Cussler, Edward

    2013-06-11

    The present invention provides a new method and apparatus/system for purifying ionic solutions, such as, for example, desalinating water, using engineered charged surfaces to sorb ions from such solutions. Surface charge is applied externally, and is synchronized with oscillatory fluid movements between substantially parallel charged plates. Ions are held in place during fluid movement in one direction (because they are held in the electrical double layer), and released for transport during fluid movement in the opposite direction by removing the applied electric field. In this way the ions, such as salt, are "ratcheted" across the charged surface from the feed side to the concentrate side. The process itself is very simple and involves only pumps, charged surfaces, and manifolds for fluid collection.

  9. Regulation of behavioral circadian rhythms and clock protein PER1 by the deubiquitinating enzyme USP2

    DEFF Research Database (Denmark)

    Yang, Yaoming; Duguay, David; Bédard, Nathalie;

    2012-01-01

    Endogenous 24-hour rhythms are generated by circadian clocks located in most tissues. The molecular clock mechanism is based on feedback loops involving clock genes and their protein products. Post-translational modifications, including ubiquitination, are important for regulating the clock...

  10. Temperature-driven and chemical-potential-driven adiabatic pumping in coherent electron transport

    OpenAIRE

    Hasegawa, M.(Graduate School of Science, Kobe University, Kobe, Japan); Kato, T

    2016-01-01

    In this study, we investigate adiabatic pumping induced by the modulation of thermodynamic variables of reservoirs, i.e., temperatures and electrochemical potentials in coherent mesoscopic devices. A simple setup that adopts an impurity Anderson model was used to examine charge pumping under the periodic modulation of the thermodynamic parameters of reservoirs. Consequently, the possibility of charge pumping in the presence of Coulomb interaction is confirmed. Finally, a formula describing ch...

  11. Analysis of primary coolant pump seal water distribution influence to chemical and volume system design

    International Nuclear Information System (INIS)

    The possible influences to Chemical and Volume Control System design caused by coolant pump seal water distribution are discussed. The essential reason is picked out in this paper. The temperature drop of charging flow at the regenerative heat exchanger outlet is calculated, and the feasible retrofits of the Chemical and Volume Control System are illustrated. The thermal hydraulic software Flowmaster 7.5 is employed to numerically investigate the possible capability of charging pump with different coolant pump seal requirements. (authors)

  12. Towards development of the lamp-based 113Cd+ ion atomic clock

    International Nuclear Information System (INIS)

    Full text: We review the development of the microwave frequency standard based on trapped Cd+ ions. The purpose of this development is to test for a possible variation of the fine structure constant by measuring differences of fractional frequency shifts of two (or three) atomic clocks in strong gravitational potential near the sun. The 113Cd+ ions are trapped in the linear quadrupole rf ion trap, similar to one described elsewhere. The trap region was not shielded from an ambient magnetic field. Approximately 105 Torr of He as a buffer gas is used to cool ions to near room temperature and increase loading efficiency. The ions are optically pumped into the S1/2, F=0 hyperfine level of the ground state by a UV light from the Cd rf discharge lamp. The 106Cd lamp has about 1 Torr of Ar and about 1 mg of 106Cd. With 10 W of rf power, the lamp substantially pumps 113Cd+ ions in the F=0 hyperfine level in one second. The ions are interrogated by one Rabi pulse using microwave radiation tuned to a clock transition ∼ 15.2 GHz that couples 52S1/2 hyperfine levels, F=1, mf=0 - F=0, mf=0. The microwave signal was referenced to a hydrogen maser. Detection, i.e., measurements of how many ions made the microwave transition, was performed using the light from the same 106Cd lamp. The UV light-microwave double-resonance spectrum is at 15.199862903 GHz, 45 Hz higher then the high precision measurement of Cd hyperfine splitting at zero magnetic field. The obtained resonance width of ∼ 0.17 Hz when interrogating for 5 sec and high signal to background light ratio gives an estimated short-term stability below 5x10-13. (author)

  13. Optical lattice clocks: Hz-level spectral width with sub-Hz reproducibility

    International Nuclear Information System (INIS)

    State-of-the-art optical clocks have surpassed microwave clocks in this century, causing discussions to redefine the SI second based on an optical transition. The superiority of optical standards was clearly revealed by two of optical-optical comparisons, one of which is a remote comparison of two strontium lattice clocks, and the other is a characterization of a single Ca+ ion clock using a Sr lattice clock as a frequency reference. The former for the first time demonstrated the frequency reproducibility of physically separated clocks at the 10−16 level. The latter has confirmed the capability of single Ca+ clocks to reach the ∼10−16 instability.

  14. Toward A Neutral Mercury Optical Lattice Clock: Determination of the Magic Wavelength for the Ultraviolet clock Transition

    International Nuclear Information System (INIS)

    A lattice clock combines the advantages of ion and neutral atom based clocks, namely the recoil and first order Doppler free spectroscopy allowed by the Lamb-Dicke regime. This lattice light field shifts the energy levels of the clock transition. However a wavelength can be found where the light-shift of the clock states cancelled to first order. In this thesis, we present the latest advances in optical lattice clock with mercury atoms developed at LNE-SYRTE. After a review of the current performances of different optical clock are currently under development, we focus on the concept of optical lattice clock and the features of the mercury that make him an excellent candidate for the realization of an optical lattice clock achievement the uncertainty of the level of 10-17. The second part is devoted to the characterization of the mercury MOT, using a sensitive detection system, which allowed us to evaluate the temperature of different isotopes present in the MOT and have a good evidence of sub-Doppler cooling for the fermionic isotopes. The third part of this these, present the experimental aspects of the implementation and the development of the laser source required for trapping mercury atoms operating near the predicted magic wavelength. Finally, we report on the Lamb-Dicke spectroscopy of the 1S0 →3 P0 clock transition in the 199Hg atoms confined in lattice trap. With use of the ultra-stable laser system, linked to LNE-SYRTE primary frequency reference, we have determined the center frequency of the transition for a range of lattice wavelengths and different lattice depths. Analyzing these measurement, we have carried out the first experimental determination of the magic wavelength, which is the crucial step towards achieving a highly accurate frequency standard using mercury. (author)

  15. Internal pump monitoring device

    International Nuclear Information System (INIS)

    In the present invention, a thermometer is disposed at the upper end of an internal pump casing of a coolant recycling system in a BWR type reactor to detect leakage of reactor water thereby ensuring the improvement of reliability of the internal pump. Namely, a thermometer is disposed, which can detect temperature elevation occurred when water in the internal pump leaked from a reactor pressure vessel passes through the gap between a stretch tube and an upper end of the pump casing. Signals from the thermometer are transmitted to a signal processing device by an instrumentation cable. The signal processing device generates an alarm when the temperature signal exceeds a predetermined value and announces that leakage of reactor water occurs in the internal pump. Since the present invention can detect the leakage of the reactor water in the pump casing in an early stage, it can contribute to the improvement of the safety and reliability of the internal pump. (I.S.)

  16. Pumped storage plants. Status and perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Vennemann, Peter [RWE Power AG, Essen (Germany). Dept. for Electrical and Mechanical Engineering; Gruber, Karl Heinz; Kunsch, Andreas [VERBUND Hydro Power AG, Vienna (Austria); Haaheim, Jon Ulrik [Statkraft Energi AS, Oslo (Norway); Sistenich, Hans-Peter; Thoeni, Hans-Rudolf

    2011-07-01

    Pumped storage plants (PSP) enable the storage of energy with rated capacities of order of GW at a single site. Reservoirs allow charging and discharging times of at least hours, sometimes days or even up to several weeks. Short ramp-up times permit the participation in the secondary reserve market as a standing reserve. For bulk energy storage, PSP reach the lowest, specific costs. In the EU27 countries, Norway and Switzerland, a total of 44 GW of pumped storage capacity is installed. The utilisation of PSP strongly correlates with the amount of conventional generation capacity, rather than with topographical options. (orig.)

  17. Adiabatic pumping in a double-dot Cooper-pair beam splitter

    OpenAIRE

    Hiltscher B.; Governale M.; Splettstoesser J.; Konig J.

    2011-01-01

    We study adiabatic pumping through a double quantum dot coupled to normal and superconducting leads. For this purpose a perturbation expansion in the tunnel coupling between the dots and the normal leads is performed and processes underlying the pumping current are discussed. Features of crossed Andreev reflection are investigated in the average pumped charge and related to local Andreev reflection in a single quantum dot. In order to distinguish Cooper pair splitting from quasi-particle pump...

  18. What is Quantum in Quantum Pumping: The Role of Phase and Asymmetries

    OpenAIRE

    Das, Kunal K.; Opatrny, Tomas

    2008-01-01

    We show that quantum pumping does not always require a quantum description or a quantum phase. Quantum pumping is shown to encompass different types of processes, some of which intrinsically rely on phase while others do not. We also show that many pumping processes have a hidden antisymmetric component that contributes significantly to the instantaneous current at the terminals without causing net charge transfer in a period. We have also computed the exact pumped current for some cases over...

  19. Recent progress of neutral mercury lattice clock in SIOM

    Science.gov (United States)

    Zhao, R. C.; Fu, X. H.; Liu, K. K.; Gou, W.; Sun, J. F.; Xu, Z.; Wang, Y. Z.

    2016-06-01

    Neutral mercury atom is one of good candidates of optical lattice clock. Due to its large atomic number, mercury atom is insensitive to black body radiation, which is the severe limitation for the development of optical clocks. However, the challenge of neutral mercury lattice clock is the requirement of high power deep-UV lasers, especially for both the cooling laser and the lattice laser. Here, we report the recent progress of neutral mercury lattice clock in SIOM, including the development for laser cooling of mercury atom and the cooling laser system with fiber laser amplifier. We have realized the magneto-optical trap of mercury atoms and measured the parameters of cold mercury atoms. A home-made external cavity diode laser works as a seed laser for a room temperature 1014.8 nm fiber laser amplifier. A new efficient frequency-doubling cavity from 1015 nm to 507 nm has been developed.

  20. Atomic Clocks and Variations of the FIne Structure Constant

    Science.gov (United States)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    1995-01-01

    We describe a new test for possible variations of the fine structure constant alpha by comparisons of rates between clocks based on hyperfine transitions in alkali atoms with different atomic number Z. H-maser, Cs, and Hg(+) clocks have a different dependence on alpha via relativistic contributions of order (Z-alpha)(sup 2). Recent H-maser vs Hg(+) clock comparison data improve laboratory limits on a time variation by 100-fold to give dot-alpha less than or equal to 3.7 x 10(exp -14)/yr. Future laser cooled clocks (Be(+), Rb, Cs, Hg(+), etc.), when compared, will yield the most sensitive of all tests for dot-alpha/alpha.

  1. Measurement of Magic Wavelengths for the ^{40}Ca^{+} Clock Transition.

    Science.gov (United States)

    Liu, Pei-Liang; Huang, Yao; Bian, Wu; Shao, Hu; Guan, Hua; Tang, Yong-Bo; Li, Cheng-Bin; Mitroy, J; Gao, Ke-Lin

    2015-06-01

    We demonstrate experimentally the existence of magic wavelengths and determine the ratio of oscillator strengths for a single trapped ion. For the first time, two magic wavelengths near 396 nm for the ^{40}Ca^{+} clock transition are measured simultaneously with high precision. By tuning the applied laser to an intermediate wavelength between transitions 4s_{1/2}→4p_{1/2} and 4s_{1/2}→4p_{3/2}, the sensitivity of the clock transition Stark shift to the oscillator strengths is greatly enhanced. Furthermore, with the measured magic wavelengths, we determine the ratio of the oscillator strengths with a deviation of less than 0.5%. Our experimental method may be applied to measure magic wavelengths for other ion clock transitions. Promisingly, the measurement of these magic wavelengths paves the way to building all-optical trapped ion clocks. PMID:26196619

  2. Complementary approaches to understanding the plant circadian clock

    CERN Document Server

    Akman, Ozgur E; Loewe, Laurence; Troein, Carl; 10.4204/EPTCS.19.1

    2010-01-01

    Circadian clocks are oscillatory genetic networks that help organisms adapt to the 24-hour day/night cycle. The clock of the green alga Ostreococcus tauri is the simplest plant clock discovered so far. Its many advantages as an experimental system facilitate the testing of computational predictions. We present a model of the Ostreococcus clock in the stochastic process algebra Bio-PEPA and exploit its mapping to different analysis techniques, such as ordinary differential equations, stochastic simulation algorithms and model-checking. The small number of molecules reported for this system tests the limits of the continuous approximation underlying differential equations. We investigate the difference between continuous-deterministic and discrete-stochastic approaches. Stochastic simulation and model-checking allow us to formulate new hypotheses on the system behaviour, such as the presence of self-sustained oscillations in single cells under constant light conditions. We investigate how to model the timing of...

  3. A Simple Loop for Simultaneous OTDM Demultiplexing and Clock Recovery

    International Nuclear Information System (INIS)

    A simple and stable loop consisting of a pair of concatenated electroabsorption modulators (EAMs) and 10 GHz clock recovery module is presented and demonstrated experimentally for simultaneous demultiplexing and clock recovery for OTDM networks. The 10Gb/s demultiplexed signal and 10 GHz recovered clock are successfully implemented from 80 Gbit/s and 160 Gbit/s OTDM signals utilizing the loop. The loop based on EAM-PLL can provide excellent tolerance range (> 5 dB) of the OSCR of the source laser, and the recovered clock signal exhibits low rms jitter over a dynamic input optical power range of 15 dB. (fundamental areas of phenomenology (including applications))

  4. Speed of light as measured by two terrestrial stable clocks

    International Nuclear Information System (INIS)

    It is shown that despite the recent criticism within the special theory of relativity there exists an arrangement of stable clocks rotating with the earth which predicts diurnal variations of the one-way speed of light, as suggested previously

  5. Speed of light as measured by two terrestrial stable clocks

    Science.gov (United States)

    Hsu, J. P.; Sherry, T. N.; Chiu, C. B.

    1977-01-01

    Despite the recent criticism within the special theory of relativity, there exists an arrangement of stable clocks rotating with the earth which predicts diurnal variations of the one-way speed of light, as suggested previously.

  6. Clocks and dynamics in quantum models of gravity

    CERN Document Server

    Malkiewicz, Przemyslaw

    2016-01-01

    We investigate how the quantum dynamics of gravitational models depend on the clocks employed in quantization procedure. Our previous result demonstrates that almost all physical features of quantum cosmological bounces depend on the choice of clock. The vital question whether all the quantum (or, semiclassical) solutions admit, away from the quantum interaction region in the far past and future, invariant asymptotic limits irrespectively of the clock's choice is addressed herein. We analyze the semiclassical dynamics of the Bianchi Type I model undergoing a quantum bounce. Our result follows from the universal principle of the free choice of clock and thus, it applies to all quantum gravity models based on the concept of the physical Hilbert space and inner dynamics. Then we propose a suitable interpretation of quantum models of gravity. As a by-product of the pursuit of our main goal, we elaborate the semiclassical description of anisotropic singularity resolution.

  7. An atomic clock with $10^{-18}$ instability

    CERN Document Server

    Hinkley, N; Phillips, N B; Schioppo, M; Lemke, N D; Beloy, K; Pizzocaro, M; Oates, C W; Ludlow, A D

    2013-01-01

    Atomic clocks have been transformational in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Next-generation optical atomic clocks can extend the capability of these timekeepers, where researchers have long aspired toward measurement precision at 1 part in $\\bm{10^{18}}$. This milestone will enable a second revolution of new timing applications such as relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests on physics beyond the Standard Model. Here, we describe the development and operation of two optical lattice clocks, both utilizing spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of $\\bm{1.6\\times 10^{-18}}$ after only $\\bm{7}$ hours of averaging.

  8. Clock synchronization of a broadband seismometer through IEEE-1588 protocol

    OpenAIRE

    Pallares, Oriol; Río Fernandez, Joaquín del; Shariat Panahi, Shahram

    2010-01-01

    In seismology, the time of the signal acquisition is highly important in order to know the magnitude and location of the earthquake. This paper presents the tests carried out to synchronize the seismometer clock through the IEEE-1588 protocol.

  9. Quantum Atomic Clock Synchronization: An Entangled Concept of Nonlocal Simultaneity

    Science.gov (United States)

    Abrams, D.; Dowling, J.; Williams, C.; Jozsa, R.

    2000-01-01

    We demonstrate that two spatially separated parties (Alice and Bob) can utilize shared prior quantum entanglement, as well as a classical information channel, to establish a synchronized pair of atomic clocks.

  10. Superradiance on the milliHertz linewidth strontium clock transition

    CERN Document Server

    Norcia, Matthew A; Cline, Julia R K; Thompson, James K

    2016-01-01

    Today's best atomic clocks are limited by frequency noise on the lasers used to interrogate the atoms. A proposed solution to this problem is to create a superradiant laser using an optical clock transition as its gain medium. This laser would act as an active atomic clock, and would be highly immune to the fluctuations in reference cavity length that limit today's best lasers. Here, we demonstrate and characterize superradiant emission from the mHz linewidth clock transition in an ensemble of laser-cooled $^{87}$Sr atoms trapped within a high-finesse optical cavity. We measure a collective enhancement of the emission rate into the cavity mode by a factor of more than 10,000 compared to independently radiating atoms. We also demonstrate a method for seeding superradiant emission and observe interference between two independent transitions lasing simultaneously. We use this interference to characterize the relative spectral properties of the two lasing sub-ensembles.

  11. Novel putative mechanisms to link circadian clocks to healthy aging.

    Science.gov (United States)

    Popa-Wagner, Aurel; Catalin, Bogdan; Buga, Ana-Maria

    2015-08-01

    The circadian clock coordinates the internal physiology to increase the homeostatic capacity thereby providing both a survival advantage to the system and an optimization of energy budgeting. Multiple-oscillator circadian mechanisms are likely to play a role in regulating human health and may contribute to the aging process. Our aim is to give an overview of how the central clock in the hypothalamus and peripheral clocks relate to aging and metabolic disorders, including hyperlipidemia and hyperglycemia. In particular, we unravel novel putative mechanisms to link circadian clocks to healthy aging. This review may lead to the design of large-scale interventions to help people stay healthy as they age by adjusting daily activities, such as feeding behavior, and or adaptation to age-related changes in individual circadian rhythms. PMID:24297467

  12. A Low-jitter 2.5-to-10 GHz Clock Multiplier Unit in CMOS

    OpenAIRE

    Beek, van, P.; Vaucher, C.S.; Leenaerts, D. M. W.; Klumperink, E.A.M.; Nauta, B.

    2003-01-01

    This paper demonstrates a low-jitter clock multiplier unit [1] that generates a 10 GHz output clock from a 2.5 GHz reference clock. An integrated 10 GHz LCoscillator is locked to the input clock, using a simple and fast phase detector circuit. This phase detector overcomes the speed limitation of a conventional tri-state Phase Frequency Detector, by eliminating an internal feedback loop. A frequency detector guarantees PLL locking without degenerating jitter performance. The clock multiplier ...

  13. CLOCK:BMAL1 is a pioneer-like transcription factor

    OpenAIRE

    Menet, Jerome S.; Pescatore, Stefan; Rosbash, Michael

    2014-01-01

    The mammalian circadian clock requires the master transcription factors CLOCK and BMAL1 to drive rhythmic gene expression. Here, Menet et al. report that rhythmic binding of CLOCK:BMAL1 on DNA promotes rhythmic chromatin opening. Mechanisms include CLOCK:BMAL1 binding to nucleosomes and chromatin modifications such as incorporation of histone variant H2A.Z. The data indicate that clock regulation of transcription relies on rhythmic regulation of chromatin accessibility, thus extending the con...

  14. Low Power at Different levels of VLSI Design an clock Distribution Schemes

    OpenAIRE

    Chetan Sharma

    2011-01-01

    Low power chip requirement in the VLSI industry is main considerable field due to the reduction of chip dimension day by day and environmental factors. In this paper various low power techniques at Gate level, Architecture level and different tradeoffs between different clock distribution schemes like as single driver clock scheme and distributed buffers clock scheme are reviewed. Here it is also tried to showing various effects of particular clock distribution scheme such as clock skew, cloc...

  15. Design of Resonant Clock Distribution Networks for 3-D Integrated Circuits

    OpenAIRE

    Rahimian Omam, Somayyeh; Pavlidis, Vasileios; De Micheli, Giovanni

    2011-01-01

    Designing a low power clock network in synchronous circuits is an important task. This requirement is stricter for 3-D circuits due to the increased power densities. Resonant clock networks are considered efficient low-power alternatives to conventional clock distribution schemes. These networks utilize additional inductive circuits to reduce the power consumption while delivering a full swing clock signal to the sink nodes. A design method for 3-D resonant clock networks is presented. The p...

  16. SpiraClock: a continuous and non-intrusive display for upcoming events

    OpenAIRE

    Dragicevic, Pierre; Huot, Stéphane

    2002-01-01

    In this paper, we present SpiraClock, a new visualization technique for nearby events. SpiraClock fills a gap between static calendar displays and pop-up reminders by giving the user a continuous and non-intrusive feedback on nearby events. Events are displayed inside an analog clock that can be used as a regular computer clock. We used SpiraClock for displaying bus schedules, and collected user feedback.

  17. Clock is important for food and circadian regulation of macronutrient absorption in mice

    OpenAIRE

    Pan, Xiaoyue; Hussain, M. Mahmood

    2009-01-01

    Clock genes respond to external stimuli and exhibit circadian rhythms. This study investigated the expression of clock genes in the small intestine and their contribution in the regulation of nutrient absorption by enterocytes. We examined expression of clock genes and macronutrient transport proteins in the small intestines of wild-type and Clock mutant (Clkmt/mt) mice with free or limited access to food. In addition, we studied absorption of macronutrients in these mice. Intestinal clock ge...

  18. Sound measurements to detect cavitation phenomena in reactor coolant pumps

    International Nuclear Information System (INIS)

    As the early detection of cavitation phenomena in pumps of coolant circuits by monitoring the hydraulic data of the pumps is not possible, and as an analysis of the sonic signals stimulated at the pump by cavitation is complicated by the interference of the pump-inherent noise spectrum, the analyses are first carried out on a special cavitation pipe section and are then compared with measurement on a pump. For sound sensors a quartz crystal diaphragm pressure sensor and a piezo-ceramic sensor with sound conductor are used. In order to be able to record the cavitation phenomena at the same time visually and by measurement the testing device and the pump consisted of acrylic glass resp. glass. Characteristic power density spectra as a function of the cavitation number of the cavitation charge until void formation are given. (ORU)

  19. Improving X10 Program Performances by Clock Removal

    OpenAIRE

    Feautrier, Paul; Violard, Eric; Ketterlin, Alain

    2014-01-01

    X10 is a promising recent parallel language designed specifically to address the challenges of productively programming a wide variety of target platforms. The sequential core of X10 is an object-oriented language in the Java family. This core is augmented by a few parallel constructs that create activities as a generalization of the well known fork/join model. Clocks are a generalization of the familiar barriers. Synchronization on a clock is specified by the advance() method call. Activitie...

  20. Motion and gravity effects in the precision of quantum clocks

    OpenAIRE

    Lindkvist, Joel; Sabín, Carlos; Johansson, Göran; Fuentes, Ivette

    2014-01-01

    We show that motion and gravity affect the precision of quantum clocks. We consider a localised quantum field as a fundamental model of a quantum clock moving in spacetime and show that its state is modified due to changes in acceleration. By computing the quantum Fisher information we determine how relativistic motion modifies the ultimate bound in the precision of the measurement of time. While in the absence of motion the squeezed vacuum is the ideal state for time estimation, we find that...

  1. The Bird of Time: Cognition and the Avian Biological Clock

    OpenAIRE

    Vincent Michael Cassone; David F Westneat

    2012-01-01

    Avian behavior and physiology are embedded in time at many levels of biological organization. Biological clock function in birds is critical for sleep/wake cycles, but may also regulate the acquisition of place memory, learning of song from tutors, social integration and time-compensated navigation. This relationship has two major implications. First, mechanisms of the circadian clock should be linked in some way to the mechanisms of all these behaviors. How is not yet clear, and evidence tha...

  2. The bird of time: cognition and the avian biological clock

    OpenAIRE

    Cassone, Vincent M.; David F Westneat

    2012-01-01

    Avian behavior and physiology are embedded in time at many levels of biological organization. Biological clock function in birds is critical for sleep/wake cycles, but may also regulate the acquisition of place memory, learning of song from tutors, social integration, and time-compensated navigation. This relationship has two major implications. First, mechanisms of the circadian clock should be linked in some way to the mechanisms of all these behaviors. How is not yet clear, and evidence th...

  3. When the circadian clock meets the melanin pigmentary system.

    Science.gov (United States)

    Slominski, Andrzej T; Hardeland, Rüdiger; Reiter, Russel J

    2015-04-01

    Silencing of BMAL1 and PER1 stimulates melanogenic activity of follicular and epidermal melanocytes, indicating a novel role for peripheral circadian clock processes in the regulation of melanin pigmentation. Linking the expression levels of BMAL1/PER1 with changes in melanogenesis opens exciting opportunities to study the role of the local molecular clock in modulation of melanocyte functions in the hair follicle and the epidermis with attendant effects on epidermal barrier functions in general. PMID:25785947

  4. Interpretable Machine Learning Models for the Digital Clock Drawing Test

    OpenAIRE

    Souillard-Mandar, William; Davis, Randall; Rudin, Cynthia; Au, Rhoda; Penney, Dana

    2016-01-01

    The Clock Drawing Test (CDT) is a rapid, inexpensive, and popular neuropsychological screening tool for cognitive conditions. The Digital Clock Drawing Test (dCDT) uses novel software to analyze data from a digitizing ballpoint pen that reports its position with considerable spatial and temporal precision, making possible the analysis of both the drawing process and final product. We developed methodology to analyze pen stroke data from these drawings, and computed a large collection of featu...

  5. The clock ambiguity and the emergence of physical laws

    OpenAIRE

    Albrecht, Andreas; Iglesias, Alberto

    2007-01-01

    The process of identifying a time variable in time reparameterization invariant theories results in great ambiguities about the actual laws of physics described by a given theory. A theory set up to describe one set of physical laws can equally well be interpreted as describing any other laws of physics by making a different choice of time variable or ``clock''. In this article we demonstrate how this ``clock ambiguity'' arises and then discuss how one might still hope to extract specific pre...

  6. An Integrated Architectural Clock Implemented Memory Design Analysis

    OpenAIRE

    Ravi Khatwal; Manoj Kumar Jain

    2015-01-01

    Recently Low power consumption and Custom Memory design is major issue for embedded designer. Micro wind and Xilinx simulator implements SRAM design architecture and performs efficient simulation. These simulators implements high performances and low power consumption of SRAM design. SRAM efficiency analyzed with 6-T architecture design and row/column based architectural design. We have analyzed clock implemented memory design and simulated with specific application. We have implemented clock...

  7. A mercury optical lattice clock at LNE-SYRTE

    Science.gov (United States)

    De Sarlo, L.; Favier, M.; Tyumenev, R.; Bize, S.

    2016-06-01

    We describe the development of an optical lattice clock based on mercury and the results obtained since the 7 th SFSM. We briefly present a new solution for the cooling laser system and an improved lattice trap that allows us to interrogate a few thousand atoms in parallel. This translates into a fractional short term stability of 1.2 x 10-15 at the clock frequency of 1.129 PHz.

  8. The Regulation of Segmentation Clock Period in Zebrafish

    OpenAIRE

    Herrgen, Leah

    2008-01-01

    Oscillations are present at many different levels of biological organization. The cell cycle that directs the division of individual cells, the regular depolarization of neurons in the sinu-atrial node which underlies the regular beating of the heart, the circadian rhythms that govern the daily activity cycles of virtually all organisms, and the clocks that make entire populations of fireflies flash on and off in unison feature as prominent examples of biological clocks. During development, b...

  9. Consistency Models in Distributed Systems with Physical Clocks

    OpenAIRE

    Du, Jiaqing

    2014-01-01

    Most existing distributed systems use logical clocks to order events in the implementation of various consistency models. Although logical clocks are straightforward to implement and maintain, they may affect the scalability, availability, and latency of the system when being used to totally order events in strong consistency models. They can also incur considerable overhead when being used to track and check the causal relationships among events in some weak consistency models. In this thesi...

  10. Master Clock and Time-Signal-Distribution System

    Science.gov (United States)

    Tjoelker, Robert; Calhoun, Malcolm; Kuhnle, Paul; Sydnor, Richard; Lauf, John

    2007-01-01

    A timing system comprising an electronic master clock and a subsystem for distributing time signals from the master clock to end users is undergoing development to satisfy anticipated timing requirements of NASA s Deep Space Network (DSN) for the next 20 to 30 years. This system has a modular, flexible, expandable architecture that is easier to operate and maintain than the present frequency and timing subsystem (FTS).

  11. Methylphenidate Modifies the Motion of the Circadian Clock

    OpenAIRE

    Antle, Michael C.; van Diepen, Hester C; Deboer, Tom; Pedram, Pardis; Pereira, Rob Rodrigues; Meijer, Johanna H.

    2012-01-01

    People with attention-deficit/hyperactivity disorder (ADHD) often experience sleep problems, and these are frequently exacerbated by the methylphenidate they take to manage their ADHD symptoms. Many of the changes to sleep are consistent with a change in the underlying circadian clock. The present study was designed to determine if methylphenidate alone could alter properties of the circadian clock. Young male mice were examined in light–dark cycles and in constant darkness and recordings wer...

  12. Clocks, computers, black holes, spacetime foam, and holographic principle

    OpenAIRE

    Ng, Y. Jack

    2000-01-01

    What do simple clocks, simple computers, black holes, space-time foam, and holographic principle have in common? I will show that the physics behind them is inter-related, linking together our concepts of information, gravity, and quantum uncertainty. Thus, the physics that sets the limits to computation and clock precision also yields Hawking radiation of black holes and the holographic principle. Moreover, the latter two strongly imply that space-time undergoes much larger quantum fluctuati...

  13. Clocking In Turbines: Remarks On Physical Nature And Geometric Requirements

    Directory of Open Access Journals (Sweden)

    Swirydczuk Jerzy

    2015-04-01

    Full Text Available The article discusses two issues relating to the clocking phenomenon in turbines, which are the physical course of stator wake deformation in rotor passages and its further interaction with downstream stator blades, and turbine geometry parameters which are believed to be most favourable for clocking. In both cases, the results presented in the article have made it possible to verify and reformulate the previously accepted opinions.

  14. Adrenergic regulation of clock gene expression in mouse liver

    OpenAIRE

    Terazono, Hideyuki; Mutoh, Tatsushi; Yamaguchi, Shun; Kobayashi, Masaki; Akiyama, Masashi; Udo, Rhyuta; Ohdo, Shigehiro; Okamura, Hitoshi; Shibata, Shigenobu

    2003-01-01

    A main oscillator in the suprachiasmatic nucleus (SCN) conveys circadian information to the peripheral clock systems for the regulation of fundamental physiological functions. Although polysynaptic autonomic neural pathways between the SCN and the liver were observed in rats, whether activation of the sympathetic nervous system entrains clock gene expression in the liver has yet to be understood. To assess sympathetic innervation from the SCN to liver tissue, we investigated whether inj...

  15. Clock Face Drawing Test Performance in Children with ADHD

    Directory of Open Access Journals (Sweden)

    Ahmad Ghanizadeh

    2013-01-01

    Full Text Available  Introduction: The utility and discriminatory pattern of the clock face drawing test in ADHD is unclear. This study therefore compared Clock Face Drawing test performance in children with ADHD and controls.   Material & methods: 95 children with ADHD and 191 school children were matched for gender ratio and age. ADHD symptoms severities were assessed using DSM-IV ADHD checklist and their intellectual functioning was assessed. The participants completed three clock-drawing tasks, and the following four functions were assessed: Contour score, Numbers score, Hands setting score, and Center score    Results: All the subscales scores of the three clock drawing tests of the ADHD group were lower than that of the control group. In ADHD children, inattention and hyperactivity/impulsivity scores were not related with free drawn clock test scores. When pre-drawn contour test was performed, inattentiveness score was statistically associated with Number score. None of the other variables of age, gender, intellectual functioning, and hand use preference were associated with Numbers score. In pre-drawn clock, no association of ADHD symptoms with any CDT subscales was significant. In addition, more errors are observed with free drawn clock and Pre-drawn contour than pre-drawn clock.    Conclusion: Putting Numbers and Hands setting are more sensitive measures to screen ADHD than Contour and Center drawing. Test performance, except Hands setting, may have already reached a developmental plateau. It is probable that Hand setting deficit in children with ADHD may not decrease from age 8 to 14 years. Performance of children with ADHD is associated with the complexity of CDT.

  16. Gravitational wave detection with optical lattice atomic clocks

    OpenAIRE

    Kolkowitz, Shimon; Pikovski, Igor; Langellier, Nicholas; Lukin, Mikhail D.; Walsworth, Ronald L.; Ye, Jun

    2016-01-01

    We propose a space-based gravitational wave detector consisting of two spatially separated, drag-free satellites sharing ultra-stable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident gravitational waves (GWs) at a lev...

  17. General relativistic effects in quantum interference of "clocks"

    CERN Document Server

    Zych, Magdalena; Costa, Fabio; Brukner, Časlav

    2016-01-01

    Quantum mechanics and general relativity have been each successfully tested in numerous experiments. However, the regime where both theories are jointly required to explain physical phenomena remains untested by laboratory experiments, and is also not fully understood by theory. This contribution reviews recent ideas for a new type of experiments: quantum interference of "clocks", which aim to test novel quantum effects that arise from time dilation. "Clock" interference experiments could be realised with atoms or photons in near future laboratory experiments.

  18. Fractional charges

    International Nuclear Information System (INIS)

    20 years ago fractional charges were imagined to explain values of conductivity in some materials. Recent experiments have proved the existence of charges whose value is the third of the electron charge. This article presents the experimental facts that have led theorists to predict the existence of fractional charges from the motion of quasi-particles in a linear chain of poly-acetylene to the quantum Hall effect. According to the latest theories, fractional charges are neither bosons nor fermions but anyons, they are submitted to an exclusive principle that is less stringent than that for fermions. (A.C.)

  19. A Clock Enhanced Loop for Simultaneous Error-Free Demultiplexing and Clock Recovery of 160 Gb/s OTDM Signal Single-Channel Transmission over 100 km

    Institute of Scientific and Technical Information of China (English)

    JIA Nan; LI Tang-Jun; ZHONG Kang-Ping; WANG Mu-Guang; CHEN Ming; LI Jing; CHI Jian-Feng

    2010-01-01

    @@ A simple clock enhanced loop of cascaded electro-absorption modulators(EAMs)and 10GHz clock recovery modules is presented.The intensity of harmonic of clock-frequency component is analyzed theoretically and verified experimentally in a 160Gb/s OTDM 100km transmission system.The 10GHz clock component is enhanced obviously before launching into the clock recovery module and the recovered clock signal exhibits low rms jitter of < 400 fs.Moreover,completely error-free(10-12)transmission is observed for more than two hours without using forward error correction technology.The power penalty is about 3.6dB.The proposed loop has merits of enhancing base clock component,simultaneously de-multiplexing and clock recovery,which make the performance of this loop more stable and high suppression of non-target channels.

  20. A clock network for geodesy and fundamental science.

    Science.gov (United States)

    Lisdat, C; Grosche, G; Quintin, N; Shi, C; Raupach, S M F; Grebing, C; Nicolodi, D; Stefani, F; Al-Masoudi, A; Dörscher, S; Häfner, S; Robyr, J-L; Chiodo, N; Bilicki, S; Bookjans, E; Koczwara, A; Koke, S; Kuhl, A; Wiotte, F; Meynadier, F; Camisard, E; Abgrall, M; Lours, M; Legero, T; Schnatz, H; Sterr, U; Denker, H; Chardonnet, C; Le Coq, Y; Santarelli, G; Amy-Klein, A; Le Targat, R; Lodewyck, J; Lopez, O; Pottie, P-E

    2016-01-01

    Leveraging the unrivalled performance of optical clocks as key tools for geo-science, for astronomy and for fundamental physics beyond the standard model requires comparing the frequency of distant optical clocks faithfully. Here, we report on the comparison and agreement of two strontium optical clocks at an uncertainty of 5 × 10(-17) via a newly established phase-coherent frequency link connecting Paris and Braunschweig using 1,415 km of telecom fibre. The remote comparison is limited only by the instability and uncertainty of the strontium lattice clocks themselves, with negligible contributions from the optical frequency transfer. A fractional precision of 3 × 10(-17) is reached after only 1,000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than any previous long-distance clock comparison. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second. PMID:27503795

  1. Dark energy from quantum uncertainty of distant clock

    Science.gov (United States)

    Luo, M. J.

    2015-06-01

    The observed cosmic acceleration was attributed to an exotic dark energy in the framework of classical general relativity. The dark energy behaves very similar with vacuum energy in quantum mechanics. However, once the quantum effects are seriously taken into account, it predicts a completely wrong result and leads to a severe fine-tuning. To solve the problem, the exact meaning of time in quantum mechanics is reexamined. We abandon the standard interpretation of time in quantum mechanics that time is just a global parameter, replace it by a quantum dynamical variable playing the role of physical clock. We find that synchronization of two spatially separated clocks can not be precisely realized at quantum level. There is an intrinsic quantum uncertainty of distant clock time, which implies an apparent vacuum energy fluctuation and gives an observed dark energy density at tree level approximation, where L P and L H are the Planck and Hubble scale cutoffs. The fraction of the dark energy is given by , which does not evolve with the internal clock time. The "dark energy" as a quantum cosmic variance is always seen comparable with the matter energy density by an observer using the internal clock time. The corrected distance-redshift relation of cosmic observations due to the distant clock effect are also discussed, which again gives a redshift independent fraction . The theory is consistent with current cosmic observations.

  2. The Molecular Circadian Clock and Alcohol-Induced Liver Injury

    Science.gov (United States)

    Udoh, Uduak S.; Valcin, Jennifer A.; Gamble, Karen L.; Bailey, Shannon M.

    2015-01-01

    Emerging evidence from both experimental animal studies and clinical human investigations demonstrates strong connections among circadian processes, alcohol use, and alcohol-induced tissue injury. Components of the circadian clock have been shown to influence the pathophysiological effects of alcohol. Conversely, alcohol may alter the expression of circadian clock genes and the rhythmic behavioral and metabolic processes they regulate. Therefore, we propose that alcohol-mediated disruption in circadian rhythms likely underpins many adverse health effects of alcohol that cut across multiple organ systems. In this review, we provide an overview of the circadian clock mechanism and showcase results from new studies in the alcohol field implicating the circadian clock as a key target of alcohol action and toxicity in the liver. We discuss various molecular events through which alcohol may work to negatively impact circadian clock-mediated processes in the liver, and contribute to tissue pathology. Illuminating the mechanistic connections between the circadian clock and alcohol will be critical to the development of new preventative and pharmacological treatments for alcohol use disorders and alcohol-mediated organ diseases. PMID:26473939

  3. The Molecular Circadian Clock and Alcohol-Induced Liver Injury

    Directory of Open Access Journals (Sweden)

    Uduak S. Udoh

    2015-10-01

    Full Text Available Emerging evidence from both experimental animal studies and clinical human investigations demonstrates strong connections among circadian processes, alcohol use, and alcohol-induced tissue injury. Components of the circadian clock have been shown to influence the pathophysiological effects of alcohol. Conversely, alcohol may alter the expression of circadian clock genes and the rhythmic behavioral and metabolic processes they regulate. Therefore, we propose that alcohol-mediated disruption in circadian rhythms likely underpins many adverse health effects of alcohol that cut across multiple organ systems. In this review, we provide an overview of the circadian clock mechanism and showcase results from new studies in the alcohol field implicating the circadian clock as a key target of alcohol action and toxicity in the liver. We discuss various molecular events through which alcohol may work to negatively impact circadian clock-mediated processes in the liver, and contribute to tissue pathology. Illuminating the mechanistic connections between the circadian clock and alcohol will be critical to the development of new preventative and pharmacological treatments for alcohol use disorders and alcohol-mediated organ diseases.

  4. Serum factors in older individuals change cellular clock properties

    Science.gov (United States)

    Pagani, Lucia; Schmitt, Karen; Meier, Fides; Izakovic, Jan; Roemer, Konstanze; Viola, Antoine; Cajochen, Christian; Wirz-Justice, Anna; Brown, Steven A.; Eckert, Anne

    2011-01-01

    Human aging is accompanied by dramatic changes in daily sleep–wake behavior: Activity shifts to an earlier phase, and the consolidation of sleep and wake is disturbed. Although this daily circadian rhythm is brain-controlled, its mechanism is encoded by cell-autonomous circadian clocks functioning in nearly every cell of the body. In fact, human clock properties measured in peripheral cells such as fibroblasts closely mimic those measured physiologically and behaviorally in the same subjects. To understand better the molecular mechanisms by which human aging affects circadian clocks, we characterized the clock properties of fibroblasts cultivated from dermal biopsies of young and older subjects. Fibroblast period length, amplitude, and phase were identical in the two groups even though behavior was not, thereby suggesting that basic clock properties of peripheral cells do not change during aging. Interestingly, measurement of the same cells in the presence of human serum from older donors shortened period length and advanced the phase of cellular circadian rhythms compared with treatment with serum from young subjects, indicating that a circulating factor might alter human chronotype. Further experiments demonstrated that this effect is caused by a thermolabile factor present in serum of older individuals. Thus, even though the molecular machinery of peripheral circadian clocks does not change with age, some age-related circadian dysfunction observed in vivo might be of hormonal origin and therefore might be pharmacologically remediable. PMID:21482780

  5. Frequency noise processes in a strontium ion optical clock

    International Nuclear Information System (INIS)

    A recent comparison of the frequencies of a pair of optical clocks based on the 674 nm 2S1/2–2D5/2 optical clock transition in 88Sr+ has highlighted the need to understand factors affecting frequency instability. We have developed statistical models to show that our clock is capable of reaching the quantum projection noise limit; for our clock using 100 ms probe pulses, this is ∼3 × 10−15/√τ. However, this optical clock uses atomic transitions with a linear Zeeman shift, which can lead to a degradation in stability in the presence of magnetic field noise. We show that this generally leads to an increase in white frequency noise, even in cases dominated by magnetic field flicker or random walk noise. By taking into account both the quantum projection and magnetic field noise we are able to explain our observed frequency instabilities. This analysis will relate to any optical clock with a linear Zeeman shift where cancellation of this shift is achieved by interrogating pairs of components. Furthermore, implementing automatic control of lasers and minimization of micromotion requires pausing of the frequency servo occasionally; this leads to only a small degradation of frequency stability. (paper)

  6. Quantum arrival and dwell times via idealized clocks

    International Nuclear Information System (INIS)

    A number of approaches to the problem of defining arrival- and dwell-time probabilities in quantum theory makes use of idealized models of clocks. An interesting question is the extent to which the probabilities obtained in this way are related to standard semiclassical results. In this paper, we explore this question using a reasonably general clock model, solved using path-integral methods. We find that, in the weak-coupling regime, where the energy of the clock is much less than the energy of the particle it is measuring, the probability for the clock pointer can be expressed in terms of the probability current in the case of arrival times, and the dwell-time operator in the case of dwell times, the expected semiclassical results. In the regime of strong system-clock coupling, we find that the arrival-time probability is proportional to the kinetic-energy density, consistent with an earlier model involving a complex potential. We argue that, properly normalized, this may be the generically expected result in this regime. We show that these conclusions are largely independent of the form of the clock Hamiltonian.

  7. Inexpensive Clock for Displaying Planetary or Sidereal Time

    Science.gov (United States)

    Lux, James

    2007-01-01

    An inexpensive wall clock has been devised for displaying solar time or sidereal time as it would be perceived on a planet other than the Earth, or for displaying sidereal time on the Earth. The concept of a wall clock synchronized to a period other than the terrestrial mean solar day is not new in itself. What is new here is that the clock is realized through a relatively simple electronic modification of a common battery-powered, quartz-crystal-oscillator-driven wall clock. The essence of the modification is to shut off the internal oscillator of the clock and replace the internal-oscillator output signal with a signal of the required frequency generated by an external oscillator. The unmodified clock electronic circuitry includes a quartz crystal connected to an integrated circuit (IC) that includes, among other parts, a buffer amplifier that conditions the oscillator output. The modification is effected by removing the quartz crystal and connecting the output terminal of the external oscillator, via a capacitor, to the input terminal of the buffer amplifier

  8. Mercury Ion Clock for a NASA Technology Demonstration Mission.

    Science.gov (United States)

    Tjoelker, Robert L; Prestage, John D; Burt, Eric A; Chen, Pin; Chong, Yong J; Chung, Sang K; Diener, William; Ely, Todd; Enzer, Daphna G; Mojaradi, Hadi; Okino, Clay; Pauken, Mike; Robison, David; Swenson, Bradford L; Tucker, Blake; Wang, Rabi

    2016-07-01

    There are many different atomic frequency standard technologies but only few meet the demanding performance, reliability, size, mass, and power constraints required for space operation. The Jet Propulsion Laboratory is developing a linear ion-trap-based mercury ion clock, referred to as DSAC (Deep-Space Atomic Clock) under NASA's Technology Demonstration Mission program. This clock is expected to provide a new capability with broad application to space-based navigation and science. A one-year flight demonstration is planned as a hosted payload following an early 2017 launch. This first-generation mercury ion clock for space demonstration has a volume, mass, and power of 17 L, 16 kg, and 47 W, respectively, with further reductions planned for follow-on applications. Clock performance with a signal-to-noise ratio (SNR)*Q limited stability of 1.5E-13/τ(1/2) has been observed and a fractional frequency stability of 2E-15 at one day measured (no drift removed). Such a space-based stability enables autonomous timekeeping of with a technology capable of even higher stability, if desired. To date, the demonstration clock has been successfully subjected to mechanical vibration testing at the 14 grms level, thermal-vacuum operation over a range of 42(°)C, and electromagnetic susceptibility tests. PMID:27019481

  9. Influence of relativistic effects on satellite-based clock synchronization

    Science.gov (United States)

    Wang, Jieci; Tian, Zehua; Jing, Jiliang; Fan, Heng

    2016-03-01

    Clock synchronization between the ground and satellites is a fundamental issue in future quantum telecommunication, navigation, and global positioning systems. Here, we propose a scheme of near-Earth orbit satellite-based quantum clock synchronization with atmospheric dispersion cancellation by taking into account the spacetime background of the Earth. Two frequency entangled pulses are employed to synchronize two clocks, one at a ground station and the other at a satellite. The time discrepancy of the two clocks is introduced into the pulses by moving mirrors and is extracted by measuring the coincidence rate of the pulses in the interferometer. We find that the pulses are distorted due to effects of gravity when they propagate between the Earth and the satellite, resulting in remarkably affected coincidence rates. We also find that the precision of the clock synchronization is sensitive to the source parameters and the altitude of the satellite. The scheme provides a solution for satellite-based quantum clock synchronization with high precision, which can be realized, in principle, with current technology.

  10. Clock auto-synchronization method for BESIII ETOF upgrade

    Science.gov (United States)

    Wang, Si-Yu; Cao, Ping; Liu, Shu-Bin; An, Qi

    2015-12-01

    An automatic clock synchronization method implemented in a field programmable gate array (FPGA) is proposed in this paper. It is developed for the clock system which will be applied in the end-cap time of flight (ETOF) upgrade of the Beijing Spectrometer (BESIII). In this design, an FPGA is used to automatically monitor the synchronization circuit and deal with signals coming from the external clock synchronization circuit. By testing different delay time of the detection signal and analyzing the signal state returned, the synchronization windows can be found automatically by the FPGA. The new clock system not only retains low clock jitter which is less than 20ps root mean square (RMS), but also demonstrates automatic synchronization to the beam bunches. So far, the clock auto-synchronizing function has been working successfully under a series of tests. It will greatly simplify the system initialization and maintenance in the future. Supported by National Natural Science Foundation of China (10979003, 11005107), CAS Center for Excellence in Particle Physics (CCEPP)

  11. Circadian Rhythms: Hijacking the Cyanobacterial Clock

    Science.gov (United States)

    Hoyle, Nathaniel P.; O’Neill, John S

    2016-01-01

    The production of limitless carbon-free energy is a long-sought dream of scientists and politicians alike. One strategy for achieving this aim is the production of hydrogen by photosynthetic microorganisms – harnessing the effectively limitless power of the sun to power our cars, toasters and PCR machines. It may be tempting to think of host expression systems as miniature factories given over entirely to the production our molecule of interest. However, the biological nature of the host must be taken into account if we are to maximize productivity. The circadian rhythm, an organism’s entrainable oscillation of biological processes with a period of around 24 hours, is one such aspect that has received scant attention but is likely to be of particular importance to photosynthetic host systems. In this issue of current biology Xu et al. describe how our knowledge of the Synechococcus elongatus circadian clock can be leveraged to improve the production of exogeneous proteins, including those involved in the production of hydrogen [1]. PMID:24309283

  12. Reduced Voltage Scaling in Clock Distribution Networks

    Directory of Open Access Journals (Sweden)

    Khader Mohammad

    2009-01-01

    Full Text Available We propose a novel circuit technique to generate a reduced voltage swing (RVS signals for active power reduction on main buses and clocks. This is achieved without performance degradation, without extra power supply requirement, and with minimum area overhead. The technique stops the discharge path on the net that is swinging low at a certain voltage value. It reduces active power on the target net by as much as 33% compared to traditional full swing signaling. The logic 0 voltage value is programmable through control bits. If desired, the reduced-swing mode can also be disabled. The approach assumes that the logic 0 voltage value is always less than the threshold voltage of the nMOS receivers, which eliminate the need of the low to high voltage translation. The reduced noise margin and the increased leakage on the receiver transistors using this approach have been addressed through the selective usage of multithreshold voltage (MTV devices and the programmability of the low voltage value.

  13. Cardiovascular tissues contain independent circadian clocks

    Science.gov (United States)

    Davidson, A. J.; London, B.; Block, G. D.; Menaker, M.

    2005-01-01

    Acute cardiovascular events exhibit a circadian rhythm in the frequency of occurrence. The mechanisms underlying these phenomena are not yet fully understood, but they may be due to rhythmicity inherent in the cardiovascular system. We have begun to characterize rhythmicity of the clock gene mPer1 in the rat cardiovascular system. Luciferase activity driven by the mPer1 gene promoter is rhythmic in vitro in heart tissue explants and a wide variety of veins and arteries cultured from the transgenic Per1-luc rat. The tissues showed between 3 and 12 circadian cycles of gene expression in vitro before damping. Whereas peak per1-driven bioluminescence consistently occurred during the late night in the heart and all arteries sampled, the phases of the rhythms in veins varied significantly by anatomical location. Varying the time of the culture procedure relative to the donor animal's light:dark cycle revealed that, unlike some other rat tissues such as liver, the phases of in vitro rhythms of arteries, veins, and heart explants were affected by culture time. However, phase relationships among tissues were consistent across culture times; this suggests diversity in circadian regulation among components of the cardiovascular system.

  14. Chemical clocks for early-type galaxies

    CERN Document Server

    Carretero, C; Beckman, J E

    2007-01-01

    We present a detailed stellar population analysis of 27 massive elliptical galaxies within 4 very rich clusters at redshift z~0.2. We obtained accurate estimates of the mean luminosity-weighted ages and relative abundances of CN, Mg and Fe as functions of the galaxy velocity dispersion, sigma. Our results are compatible with a scenario in which the stellar populations of massive elliptical galaxies, independently of their environment and mass, had formation timescales shorter than ~1 Gyr. This result implies that massive elliptical galaxies have evolved passively since, at least, as long ago as z~2. For a given galaxy mass the duration of star formation is shorter in those galaxies belonging to more dense environments. Finally, we show that the abundance ratios [CN/Fe] and [Mg/Fe] are the key "chemical clocks" to infer the star formation history timescales in ellipticals. In particular, [Mg/Fe] provides an upper limit for those formation timescales, while [CN/Fe] apperars to be the most suitable parameter to ...

  15. Two-phase charge-coupled device

    Science.gov (United States)

    Kosonocky, W. F.; Carnes, J. E.

    1973-01-01

    A charge-transfer efficiency of 99.99% per stage was achieved in the fat-zero mode of operation of 64- and 128-stage two-phase charge-coupled shift registers at 1.0-MHz clock frequency. The experimental two-phase charge-coupled shift registers were constructed in the form of polysilicon gates overlapped by aluminum gates. The unidirectional signal flow was accomplished by using n-type substrates with 0.5 to 1.0 ohm-cm resistivity in conjunction with a channel oxide thickness of 1000 A for the polysilicon gates and 3000 A for the aluminum gates. The operation of the tested shift registers with fat zero is in good agreement with the free-charge transfer characteristics expected for the tested structures. The charge-transfer losses observed when operating the experimental shift registers without the fat zero are attributed to fast interface state trapping. The analytical part of the report contains a review backed up by an extensive appendix of the free-charge transfer characteristics of CCD's in terms of thermal diffusion, self-induced drift, and fringing field drift. Also, a model was developed for the charge-transfer losses resulting from charge trapping by fast interface states. The proposed model was verified by the operation of the experimental two-phase charge-coupled shift registers.

  16. Electrokinetic pumps and actuators

    International Nuclear Information System (INIS)

    Flow and ionic transport in porous media are central to electrokinetic pumping as well as to a host of other microfluidic devices. Electrokinetic pumping provides the ability to create high pressures (to over 10,000 psi) and high flow rates (over 1 mL/min) with a device having no moving parts and all liquid seals. The electrokinetic pump (EKP) is ideally suited for applications ranging from a high pressure integrated pump for chip-scale HPLC to a high flow rate integrated pump for forced liquid convection cooling of high-power electronics. Relations for flow rate and current fluxes in porous media are derived that provide a basis for analysis of complex microfluidic systems as well as for optimization of electrokinetic pumps

  17. Variations in battery life of a heart-lung machine using different pump speeds, pressure loads, boot material, centrifugal pump head, multiple pump usage, and battery age.

    LENUS (Irish Health Repository)

    Marshall, Cornelius

    2012-02-03

    Electrical failure during cardiopulmonary bypass (CPB) has previously been reported to occur in 1 of every 1500 cases. Most heart-lung machine pump consoles are equipped with built-in battery back-up units. Battery run times of these devices are variable and have not been reported. Different conditions of use can extend battery life in the event of electrical failure. This study was designed to examine the run time of a fully charged battery under various conditions of pump speed, pressure loads, pump boot material, multiple pump usage, and battery life. Battery life using a centrifugal pump also was examined. The results of this study show that battery life is affected by pump speed, circuit pressure, boot stiffness, and the number of pumps in service. Centrifugal pumps also show a reduced drain on battery when compared with roller pumps. These elements affect the longevity and performance of the battery. This information could be of value to the individual during power failure as these are variables that can affect the battery life during such a challenging scenario.

  18. Development of a strontium optical lattice clock for space applications

    Science.gov (United States)

    Singh, Yeshpal

    2016-07-01

    With timekeeping being of paramount importance for modern life, much research and major scientific advances have been undertaken in the field of frequency metrology, particularly over the last few years. New Nobel-prize winning technologies have enabled a new era of atomic clocks; namely the optical clock. These have been shown to perform significantly better than the best microwave clocks reaching an inaccuracy of 1.6x10-18 [1]. With such results being found in large lab based apparatus, the focus now has shifted to portability - to enable the accuracy of various ground based clocks to be measured, and compact autonomous performance - to enable such technologies to be tested in space. This could lead to a master clock in space, improving not only the accuracy of technologies on which modern life has come to require such as GPS and communication networks. But also more fundamentally, this could lead to the redefinition of the second and tests of fundamental physics including applications in the fields of ground based and satellite geodesy, metrology, positioning, navigation, transport and logistics etc. Within the European collaboration, Space Optical Clocks (SOC2) [2-3] consisting of various institutes and industry partners across Europe we have tried to tackle this problem of miniaturisation whilst maintaining stability, accuracy (5x10-17) and robustness whilst keeping power consumption to a minimum - necessary for space applications. We will present the most recent results of the Sr optical clock in SOC2 and also the novel compact design features, new methods employed and outlook. References [1] B. J. Bloom, T. L. Nicholson, J. R. Williams, S. L. Campbell, M. Bishof, X. Zhang, W. Zhang, S. L. Bromley, and J. Ye, "An optical lattice clock with accuracy and stability at the 10-18 level," Nature 506, 71-75 (2014). [2] S. Schiller et al. "Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performance transportable and breadboard optical clocks and

  19. Fakir fuel pump

    Science.gov (United States)

    1922-01-01

    In designing the Fakir fuel pump, the fundamental idea was to obtain a simple and reliable method of conveying the fuel from a low tank to the carburetor, with the avoidance of the faults of all former methods and the simultaneous warming of the fuel by means of the heat of compression generated. The principle of the Fakir fuel pump rests on the well-known principle of the diaphragm pump, which must be suitably adapted to the present purpose.

  20. Detection of pump degradation

    Energy Technology Data Exchange (ETDEWEB)

    Greene, R.H.; Casada, D.A.; Ayers, C.W. [and others

    1995-08-01

    This Phase II Nuclear Plant Aging Research study examines the methods of detecting pump degradation that are currently employed in domestic and overseas nuclear facilities. This report evaluates the criteria mandated by required pump testing at U.S. nuclear power plants and compares them to those features characteristic of state-of-the-art diagnostic programs and practices currently implemented by other major industries. Since the working condition of the pump driver is crucial to pump operability, a brief review of new applications of motor diagnostics is provided that highlights recent developments in this technology. The routine collection and analysis of spectral data is superior to all other technologies in its ability to accurately detect numerous types and causes of pump degradation. Existing ASME Code testing criteria do not require the evaluation of pump vibration spectra but instead overall vibration amplitude. The mechanical information discernible from vibration amplitude analysis is limited, and several cases of pump failure were not detected in their early stages by vibration monitoring. Since spectral analysis can provide a wealth of pertinent information concerning the mechanical condition of rotating machinery, its incorporation into ASME testing criteria could merit a relaxation in the monthly-to-quarterly testing schedules that seek to verify and assure pump operability. Pump drivers are not included in the current battery of testing. Operational problems thought to be caused by pump degradation were found to be the result of motor degradation. Recent advances in nonintrusive monitoring techniques have made motor diagnostics a viable technology for assessing motor operability. Motor current/power analysis can detect rotor bar degradation and ascertain ranges of hydraulically unstable operation for a particular pump and motor set. The concept of using motor current or power fluctuations as an indicator of pump hydraulic load stability is presented.