Sample records for high gain spontaneous

  1. Gain media edge treatment to suppress amplified spontaneous emission in a high power laser

    DOEpatents

    Hackel, Lloyd A. (Livermore, CA); Soules, Thomas F. (Livermore, CA); Fochs, Scott N. (Livermore, CA); Rotter, Mark D. (San Ramon, CA); Letts, Stephan A. (San Ramon, CA)

    2008-12-09

    A novel method and apparatus for suppressing ASE and parasitic oscillation modes in a high average power laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges using a substantially high index bonding elastomer or epoxy to a predetermined electromagnetic absorbing arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE and parasitic oscillation modes can be effectively suppressed.

  2. Gain media edge treatment to suppress amplified spontaneous emission in a high power laser

    DOEpatents

    Hackel, Lloyd A. (Livermore, CA); Soules, Thomas F. (Livermore, CA); Fochs, Scott N. (Livermore, CA); Rotter, Mark D. (San Ramon, CA); Letts, Stephan A. (San Ramon, CA)

    2011-02-22

    A novel method and apparatus for suppressing ASE and/or parasitic oscillation modes in a laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges to a predetermined electromagnetic absorbing material arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE, parasitic oscillation modes and/or residual pump energy can be effectively suppressed.

  3. Amplified spontaneous Raman scattering and gain in fiber Raman amplifiers

    Microsoft Academic Search

    MARK L. DAKSS; Paul Melman

    1985-01-01

    The spectrum of amplified spontaneous Raman scattering and gain in a fiber Raman amplifer has been calculated analytically as a function of distance and pump power. The model used makes no assumptions on the magnitude of the gain and considers the pump nondepletion region. From the results, the on\\/off ratio has been calculated and is found to have a variation

  4. Optical gain, spontaneous and stimulated emission of surface plasmon

    E-print Network

    Grandidier, Jonathan

    Optical gain, spontaneous and stimulated emission of surface plasmon polaritons in confined finally apply this formalism to describe gain­assisted propagation in a dielectric­loaded surface plasmon polariton waveguide. © 2010 Optical Society of America OCIS codes: (240.6680) Surface plasmons; (230

  5. Calculation of spontaneous emission and gain spectra for quantum cascade lasers

    Microsoft Academic Search

    Q. K. Yang; A. Z. Li

    2000-01-01

    In this paper, a quantum cascade laser has been treated as a three-level system, and the calculation of the spontaneous emission and gain spectra has been given. In the calculation, the conduction band nonparabolicity and the injection and exit of electrons have been considered. Results have shown that with increasing injection current, the spontaneous emission peak blue shifts, and the

  6. Unidirectional high gain brake stop

    NASA Technical Reports Server (NTRS)

    Lang, David J. (Inventor)

    1987-01-01

    This invention relates to a unidirectional high gain brake arrangement that includes in combination a shaft mounted for rotation within a housing. The shaft is rotatable in either direction. A brake is selectively releasably coupled to the housing and to the shaft. The brake has a first member. An intermittent motion device is respectively coupled through the first member to the housing and through a one-way clutch to the shaft. The brake also has a second member that is mechanically coupled to the first brake member and to the housing. The intermittent motion device causes the brake to be activated by movement imparted to the first brake member after a preset number of revolutions of the shaft in one direction. The brake is released by rotation of the shaft in an opposite direction whereby torque transmitted through the one-way clutch to the first brake member is removed.

  7. Spontaneous emission and gain in a waveguide free-electron laser

    Microsoft Academic Search

    William J. Golightly; Sally K. Ride

    1991-01-01

    A free-electron laser (FEL) enclosed in a waveguide of narrowly spaced parallel plates has been proposed as a compact, coherent source of far-infrared radiation. The spontaneous emission and small-signal gain of such a device are analyzed. Maxwell's equations are solved for the fields of a relativistic electron beam passing through a linearly polarized undulator in the presence of a parallel-plane

  8. Model-based estimation of loop gain using spontaneous breathing: a validation study.

    PubMed

    Gederi, Elnaz; Nemati, Shamim; Edwards, Bradley A; Clifford, Gari D; Malhotra, Atul; Wellman, Andrew

    2014-09-15

    Non-invasive assessment of ventilatory control stability or loop gain (which is a key contributor in a number of sleep-related breathing disorders) has proven to be cumbersome. We present a novel multivariate autoregressive model that we hypothesize will enable us to make time-varying measurements of loop gain using nothing more than spontaneous fluctuations in ventilation and CO2. The model is adaptive to changes in the feedback control loop and therefore can account for system non-stationarities (e.g. changes in sleep state) and it is resistant to artifacts by using a signal quality measure. We tested this method by assessing its ability to detect a known increase in loop gain induced by proportional assist ventilation (PAV). Subjects were studied during sleep while breathing on continuous positive airway pressure (CPAP) alone (to stabilize the airway) or on CPAP+PAV. We show that the method tracked the PAV-induced increase in loop gain, demonstrating its time-varying capabilities, and it remained accurate in the face of measurement related artifacts. The model was able to detect a statistically significant increase in loop gain from 0.14±10 on CPAP alone to 0.21±0.13 on CPAP+PAV (p<0.05). Furthermore, our method correctly detected that the PAV-induced increase in loop gain was predominantly driven by an increase in controller gain. Taken together, these data provide compelling evidence for the validity of this technique. PMID:25038522

  9. High-gain aneutronic fusion

    NASA Astrophysics Data System (ADS)

    Hay, M. J.; Fisch, N. J.

    2014-10-01

    Fusion reactions which release most of their energy in charged particles are desirable for power applications. The proton-boron reaction p+11 B --> 3 ? + 8 . 7 MeV is ideal due to the low incidence of neutron-generating side reactions and the natural abundance of the reactants. However, an optically thin proton-boron plasma radiates a substantial amount of energy via bremsstrahlung. To compensate, we consider ways of increasing the fusion reactivity above the Maxwellian value. Using the fusion alpha particle energy to heat specific parts of the proton velocity distribution is one such approach. In principle, waves could channel the alpha energy to protons near the cross section maximum in energy, resulting in a substantial reactivity gain. By making aggressive assumptions regarding how energy might be channeled, we present upper bounds on the extent to which a proton-boron fusion reaction can be self-sustaining. Work supported by DOE Contract No. DE-AC02-09CH11466 and DOE NNSA SSAA Grant No. DE274-FG52-08NA28553. M. J. H. was supported in part by the DOE NNSA SSGF under Grant No. DE-FC52-08NA28752.

  10. The Galileo high gain antenna deployment anomaly

    NASA Technical Reports Server (NTRS)

    Johnson, Michael R.

    1994-01-01

    On April 11, 1991, the Galileo spacecraft executed a sequence that would open the spacecraft's High Gain Antenna. The Antenna's launch restraint had been released just after deployment sequence, the antenna, which opens like an umbrella, never reached the fully deployed position. The analyses and tests that followed allowed a conclusive determination of the likely failure mechanisms and pointed to some strategies to use for recovery of the high gain antenna.

  11. Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser

    Microsoft Academic Search

    S. V. Milton; E. Gluskin; N. D. Arnold; C. Benson; W. Berg; S. G. Biedron; M. Borland; Y.-C. Chae; R. J. Dejus; P. K. Den Hartog; B. Deriy; M. Erdmann; Y. I. Eidelman; M. W. Hahne; Z. Huang; K.-J. Kim; J. W. Lewellen; Y. Li; A. H. Lumpkin; O. Makarov; E. R. Moog; A. Nassiri; V. Sajaev; R. Soliday; B. J. Tieman; E. M. Trakhtenberg; G. Travish; I. B. Vasserman; N. A. Vinokurov; X. J. Wang; G. Wiemerslage; B. X. Yang

    2001-01-01

    Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report

  12. Calculation of the gain coefficient in cryogenically cooled Yb : YAG disks at high heat generation rates

    SciTech Connect

    Vadimova, O L; Mukhin, I B; Kuznetsov, I I; Palashov, O V; Perevezentsev, E A; Khazanov, Efim A [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

    2013-03-31

    We have calculated the stored energy and gain coefficient in disk gain elements cooled to cryogenic temperatures. The problem has been solved with allowance for intense heat generation, amplified spontaneous emission and parasitic lasing, without averaging over any spatial coordinate. The numerical simulation results agree well with experimental data, in particular at high heat generation rates. Experimental data and theoretical analysis indicate that composite disk gain elements containing an undoped region can store considerably more energy due to suppression of amplified spontaneous emission and parasitic lasing. (extreme light fields and their applications)

  13. Mechanisms of the Rosetta high gain antenna

    NASA Astrophysics Data System (ADS)

    Pereira, Carlos

    2001-09-01

    This paper describes the antenna pointing mechanism (APM) and the hold down and release mechanism (HRM) used in the high gain antenna of the ROSETTA mission. The hold down and release mechanism consists of three units which compensate the tolerance mismatch between antenna and spacecraft through incorporation of potting rings. Given that the activation mode is pyrotechnic, release shock is a major concern and is minimised through integration of shock absorbers which allow stroking of the separation nuts. The antenna pointing mechanism is a dual drive (azimuth over elevation) unit which allows controlled rotation of the antenna. The drive units incorporate spring loaded end stops to prevent the antenna from hitting the spacecraft, and optical encoders which register the absolute position of the antenna. The pointing and the hold down mechanisms of the ROSETTA antenna are fully qualified and will withstand the high launch loads of the Ariane-5 and the environmental demands of deep space operation.

  14. Progress toward high-gain laser fusion

    NASA Astrophysics Data System (ADS)

    Storm, Erik

    1988-09-01

    A 1985 to 1986 Review of the U.S. inertial confinement fusion program by the National Academy of Sciences concluded that five more years might be required to obtain enough data to determine the future course of the program. Since then, data from the Nova laser and from the Halite/Centurion program have resolved most of the outstanding problems identified by the NAS review. In particular, we now believe that we can produce a sufficiently uniform target; that we can keep the energy content in hot electrons and high-energy photons low enough (approximately 1 to 10 percent of drive energy, depending on target design) and achieve enough pulse-shaping accuracy (approximately 10 percent, with a dynamic range of 100:1) to keep the fuel on a near-Fermi-degenerate adiabat; that we can produce an approximately 100-Mbar pressure pulse of sufficient uniformity (approximately 1 percent), and can control hydrodynamic instabilities so that the mix of the pusher into the hot spot is low enough to permit marginal ignition. These results are sufficiently encouraging that DOE is planning to complete a 10-MJ laboratory microfusion facility to demonstrate high-gain ICF in the laboratory within a decade.

  15. ZnO Nanowire UV Photodetectors with High Internal Gain

    E-print Network

    Wang, Deli

    ZnO Nanowire UV Photodetectors with High Internal Gain C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D, California 92093-0407 Received January 15, 2007; Revised Manuscript Received February 26, 2007 ABSTRACT ZnO, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products (GB) higher than 10

  16. Theory for high gain, high power free electron lasers

    SciTech Connect

    Colson, W.B. (Berkeley Research Associates, Inc., CA (USA))

    1989-01-01

    In the past contracting period, the research on high gain, high power free electron lasers (FELs) has been fruitful. The findings have resulted in publications, presentations, and some important new research topics in progress. The work has been accomplished in close collaboration with the FEL physicists at LLNL including weekly visits to the LLNL Beam Research Building. The new research proposed is also coordinated closely with specific LLNL FEL project physicists, and the upcoming high-gain, high-power amplifier experiments during the next year on the Paladin FEL. The research includes analysis of the initial ELF experiments, identification of new FEL physics in Paladin at 5m length, electron beam distributions from future induction linacs, electron beam distributions in weak optical fields, a major FEL review paper, a simple understanding of FEL optical guiding, multimode analysis applied to single-pass FEL amplifiers, a LLNL review talk on FEL sidebands and electron distribution functions. 3 refs.

  17. A very high frequency CMOS Variable Gain Amplifier 

    E-print Network

    Tan, Siang Tong

    2001-01-01

    A fully differential CMOS Variable Gain Amplifier (VGA) consisting of an analog multiplier, current gain stages, and resistor loads is designed for very high frequency applications. The gain can be programmed from 0dB to 40dB with -3dB bandwidth...

  18. Original article Selection for high and low, colony weight gain

    E-print Network

    Paris-Sud XI, Université de

    weight loss were not correlated with seasonal colony weight gain and do not appear to be useful aidsOriginal article Selection for high and low, colony weight gain in the honey bee, Apis mellifera; Seasonal colony weight gain (honey production) in the honey bee, Apis mellifera, can be modified

  19. High-resolution Brillouin gain spectroscopy in fused silica

    SciTech Connect

    Faris, G.W.; Jusinski, L.E.; Dyer, M.J.; Bischel, W.K.; Hickman, A.P. (Molecular Physics Laboratory, SRI International, Menlo Park, California 94025 (USA))

    1990-06-15

    We report what is to our knowledge the first high-resolution Brillouin gain spectrum in a solid. Resonances corresponding to longitudinal (compressional) and transverse (shear) acoustic waves in fused silica are observed with good resolution and a high signal-to-noise ratio. Absolute gain coefficients, linewidths, and Brillouin frequency shifts are measured. The agreement with previously measured values is good.

  20. The high gain 1310nm Raman amplifier

    NASA Astrophysics Data System (ADS)

    Turkiewicz, Jaros?aw Piotr; Czy?ak, Pawe?

    2014-05-01

    Due to the growing demand for transmission capacity, it has become essential to utilize multiple wavelength domains in one transmission system. To take full advantage of parallel 1550/1310 nm transmission, efficient 1310 nm amplification techniques are needed, such as the 1310 nm Raman amplifier. In the paper, we present detailed studies regarding the design of the 1310 nm Raman amplifier. Based on numerical simulations, we propose an efficient 1310 nm Raman amplifier design, utilizing the 1240 nm quantum-dot pumping lasers. The designed Raman amplifier is built and characterized. The achieved gain in a QD-laser pumped 1310 nm Raman amplifier was 19.5 dB. The presented results open the way for enhanced utilization of the 1310 nm Raman amplifier in the opto-telecommunication systems.

  1. High-Gain Adaptive Control: A Derivative-Based Approach

    Microsoft Academic Search

    Franco Blanchini; Thomas Parisini; Felice Andrea Pellegrino; Gilberto Pin

    2009-01-01

    In this work, we propose an adaptive scheme which is a counterpart of existing high gain control techniques based on control Lyapunov functions. Given a control Lyapunov function, the main idea is that of tuning the feedback gain according to a suitably-chosen Lyapunov time-derivative. The control gain is not monotonically non-decreasing as in existing techniques, but it is increased or

  2. High-gain adaptive control: A derivative-based approach

    Microsoft Academic Search

    Franco Blanchini; Thomas Parisini; Felice Andrea Pellegrino; Gilberto Pin

    2008-01-01

    We propose an adaptive scheme which is a counterpart of existing high gain control techniques based on control Lyapunov functions. Given a control Lyapunov function, the main idea is that of tuning the feedback gain according to a suitably-chosen Lyapunov time-derivative. The control gain is not monotonically non-decreasing as in existing techniques, but it is increased or decreased depending on

  3. Amplified spontaneous emission and optical gain measurements from pyrromethene 567--doped polymer waveguides and quasi-waveguides.

    PubMed

    Costela, A; García, O; Cerdán, L; García-Moreno, I; Sastre, R

    2008-05-12

    Amplified spontaneous emission from planar waveguides and quasi-waveguides based on Pyrromethene 567-doped poly(methyl methacrylate) thin films deposited onto quartz and glass substrates is investigated. Films with different thickness were prepared and pumped optically at 532 nm with pulses of up to 8 MW/cm(2). Pump thresholds for the onset of ASE emission, optical gains and losses were assessed. Net gain coefficients were estimated by fitting the data provided by variable stripe length measurements with a theoretical expression which takes into account saturation. In this way, net gain coefficients of up to 56 +/- 9 cm(-1) at a pump intensity of 5.3 MW/cm(2) for quasi-waveguides and up to 20.6 +/- 2.7 cm(-1) at a pump intensity of 3.4 MW/cm2 for waveguides, were obtained. Loss coefficients in the waveguides were estimated to be 3.8 +/- 0.4 cm-1 and 6.1 +/- 1.3 cm(-1) for 15 microm and 5 microm thick films, respectively. The results obtained seem to indicate a stronger self-mode-restriction capability in the quasiwaveguides than in conventional total internal-reflection waveguides. PMID:18545406

  4. JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. , NO. , MONTH 2004 1 Dynamics of high gain fiber laser arrays

    E-print Network

    Pele?, Slaven

    fiber laser arrays Jeffrey L. Rogers, Slaven Peles, and Kurt Wiesenfeld (Invited Paper) Abstract-- Recent experiments [1] have shown that a small number of fiber lasers can spontaneously form coherent. In this paper we develop a dynamical model for fiber laser arrays that is valid in the high gain regime

  5. A very high frequency CMOS Variable Gain Amplifier

    E-print Network

    Tan, Siang Tong

    2001-01-01

    A VERY HIGH FREQUENCY CMOS VARIABLE GAIN AMPLIFIER A Thesis by SIANG TONG TAN Submitted to the Office of Graduate Studies of Texas AgrM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 2001... of an analog multiplier, current gain stages, and resistor loads is designed for very high frequency applications. The gain can be programmed from OdB to 40dB with -3dB bandwidth greater than 200MHz and 500MHz in 0. 5ltm and 0. 35pm CMOS process...

  6. Computer simulation of space station computer steered high gain antenna

    NASA Technical Reports Server (NTRS)

    Beach, S. W.

    1973-01-01

    The mathematical modeling and programming of a complete simulation program for a space station computer-steered high gain antenna are described. The program provides for reading input data cards, numerically integrating up to 50 first order differential equations, and monitoring up to 48 variables on printed output and on plots. The program system consists of a high gain antenna, an antenna gimbal control system, an on board computer, and the environment in which all are to operate.

  7. Stacking nonenzymatic circuits for high signal gain

    PubMed Central

    Chen, Xi; Briggs, Neima; McLain, Jeremy R.; Ellington, Andrew D.

    2013-01-01

    Signal amplification schemes that do not rely on protein enzymes show great potential in areas as abstruse as DNA computation and as applied as point-of-care molecular diagnostics. Toehold-mediated strand displacement, a programmable form of dynamic DNA hybridization, can be used to design powerful amplification cascades that can achieve polynomial or exponential amplification of input signals. However, experimental implementation of such amplification cascades has been severely hindered by circuit leakage due to catalyst-independent side reactions. In this study, we systematically analyzed the origins, characteristics, and outcomes of circuit leakage in amplification cascades and devised unique methods to obtain high-quality DNA circuits that exhibit minimal leakage. We successfully implemented a two-layer cascade that yielded 7,000-fold signal amplification and a two-stage, four-layer cascade that yielded upward of 600,000-fold signal amplification. Implementation of these unique methods and design principles should greatly empower molecular programming in general and DNA-based molecular diagnostics in particular. PMID:23509255

  8. High gain amplifiers: Power oscillations and harmonic generation

    SciTech Connect

    Dattoli, G.; Ottaviani, P. L.; Pagnutti, S. [ENEA, Dipartimento Tecnologie Fisiche e Nuovi Materiali, Centro Ricerche Frascati, C.P. 65-00044 Frascati, Rome (Italy)

    2007-08-01

    We discuss the power oscillations in saturated high gain free electron laser amplifiers and show that the relevant period can be written in terms of the gain length. We use simple arguments following from the solution of the pendulum equation in terms of Jacobi elliptic functions. Nontrivial effects due to nonlinear harmonic generation and inhomogeneous broadening are discussed too, as well as the saturated dynamics of short pulses.

  9. Superradiance in the high-gain free-electron laser

    Microsoft Academic Search

    R. Bonifacio; B. W. J. McNeil; P. Pierini

    1989-01-01

    In this paper we describe the effects of slippage on the single-pass high-gain free-electron laser (FEL) amplifier. We use a one-dimensional computational code to show the existence of two new dynamical regimes characterized by a dimensionless parameter K, which is a measure of the slippage in one gain length. We define the long-pulse limit to be when K<<1 or the

  10. Gas gain stability of MSGCs operating at high rate

    NASA Astrophysics Data System (ADS)

    van den Berg, F. D.; Daum, C.; van Eijk, B.; Hartjes, F. G.; Udo, F.; Zhukov, V.

    1997-02-01

    Micro Strip Gas Counters (MSGCs) with coated and uncoated borosilicate glass substrates have been investigated on their high rate capability and long-term gas gain stability. It is shown that the gain remains almost constant at count rates up to 10 5 mm -2 s -1 when a semiconductive layer of S8900 glass or polydiamond is applied under or over the strips. The application of such a coating also favours the gain stability at long-term operation. However, the maximum attainable gas gain for coated substrates is 4-10 times smaller than for bare borosilicate glass supports. For the latter substrate type, we observe less ageing when the strips are made of nickel instead of aluminium or copper.

  11. Characteristics of current filamentation in high gain photoconductive semiconductor switching

    SciTech Connect

    Zutavern, F J; Loubriel, G M; O'Malley, M W; Helgeson, W D; McLaughlin, D L; Denison, G J

    1992-01-01

    Characteristics of current filamentation are reported for high gain photoconductive semiconductor switches (PCSS). Infrared photoluminescence is used to monitor carrier recombination radiation during fast initiation of high gain switching in large (1.5 cm gap) lateral GaAs PCSS. Spatial modulation of the optical trigger, a 200--300 ps pulse width laser, is examined. Effects on the location and number of current filaments, rise time, and delay to high gain switching, minimum trigger energy, and degradation of switch contacts are presented. Implications of these measurements for the theoretical understanding and practical development of these switches are discussed. Efforts to increase current density and reduce switch size and optical trigger energy requirements are described. Results from contact development and device lifetime testing are presented and the impact of these results on practical device applications is discussed.

  12. Suppression of spontaneous breathing during high-frequency jet ventilation

    Microsoft Academic Search

    A. J. van Vught; A. Versprille; J. R. C. Jansen

    1986-01-01

    Conditions which suppress spontaneous breathing activity during high-frequency jet ventilation (HFJV) were analysed in Yorkshire piglets under pentobarbital anesthesia. The highest PaCO2 at which the animals did not breathe against the ventilator (apnea point) was established during different patterns of ventilation, either by changing the minute volume or by adding CO2 to the inspiratory gas. Arterial oxygen tension was maintained

  13. Radiation Response of Emerging High Gain, Low Noise Detectors

    NASA Technical Reports Server (NTRS)

    Becker, Heidi N.; Farr, William H; Zhu, David Q.

    2007-01-01

    Data illustrating the radiation response of emerging high gain, low noise detectors are presented. Ionizing dose testing of silicon internal discrete avalanche photodiodes, and 51-MeV proton testing of InGaAs/InAlAs avalanche photodiodes operated in Geiger mode are discussed.

  14. Longitudinal dynamics of high gain free electron laser amplifiers

    NASA Astrophysics Data System (ADS)

    Dattoli, G.; Sabia, E.; Ottaviani, P. L.; Pagnutti, S.; Petrillo, V.

    2013-03-01

    We consider the dynamics of a coherent seed undergoing a free electron laser high gain amplification. We discuss the dispersion of the optical packet during the interaction and study the problem using different formalisms, including that of the Wigner distribution. The analysis we develop is mainly based on a 1D procedure; the inclusion of transverse longitudinal interplay is also briefly discussed.

  15. High gain 1310nm Raman amplifier (withdrawal notice)

    NASA Astrophysics Data System (ADS)

    Czy?ak, Pawe?; Turkiewicz, Jaros?aw Piotr; Mazurek, Pawe?

    2014-05-01

    This paper has been withdrawn. The following nearly identical paper is available in this conference proceedings: Jaros?aw Piotr Turkiewicz and Pawe? Czy?ak, "The high gain 1310nm Raman amplifier," Proc. SPIE 9228, Optical Fibers and Their Applications 2014, 92280P (May 12, 2014); doi:10.1117/12.2067055.

  16. Shaped reflector beam waveguide and high gain antenna systems

    NASA Technical Reports Server (NTRS)

    Galindo-Israel, V.; Mittra, R.

    1983-01-01

    In this paper the problem of synthesizing dual reflector antennas for both amplitude and phase control of the final aperture distribution is discussed. An approximate procedure for the offset synthesis problem is presented and applications of the procedure to the shaping of beam waveguides and reflectors for high-gain antenna systems are illustrated.

  17. Dispersion relations for 1D high-gain FELs

    SciTech Connect

    Webb, S.D.; Litvinenko, V.N.

    2010-08-23

    We present analytical results for the one-dimensional dispersion relation for high-gain FELs. Using kappa-n distributions, we obtain analytical relations between the dispersion relations for various order kappa distributions. Since an exact solution exists for the kappa-1 (Lorentzian) distribution, this provides some insight into the number of modes on the way to the Gaussian distribution.

  18. Variable threshold Q-switching of high gain lasers

    Microsoft Academic Search

    W. C. Scott; M. deWit

    1971-01-01

    We report a technique of Q-switching a high-gain, flash-pumped laser which is capable of extracting, within a single pumping flash, an arbitrary number of output pulses with individually predetermined energies and times of occurrence. Conventional Q-switched lasers which vary the reasonator from a high loss to a fixed low loss state cannot achieve this because the energy of a Q-switched

  19. Silicon photodiodes with high photoconductive gain at room temperature.

    PubMed

    Li, X; Carey, J E; Sickler, J W; Pralle, M U; Palsule, C; Vineis, C J

    2012-02-27

    Silicon photodiodes with high photoconductive gain are demonstrated. The photodiodes are fabricated in a complementary metal-oxide-semiconductor (CMOS)-compatible process. The typical room temperature responsivity at 940 nm is >20 A/W and the dark current density is ? 100 nA/cm2 at 5 V reverse bias, yielding a detectivity of ? 10(14) Jones. These photodiodes are good candidates for applications that require high detection sensitivity and low bias operation. PMID:22418357

  20. Observation of high gain in Ne-like Ag lasers

    SciTech Connect

    Fields, D.J.; Walling, R.S.; Shimkaveg, G.M.; MacGowan, B.J.; Da Silva, L.B.; Scofield, J.H.; Osterheld, A.L.; Phillips, T.W.; Rosen, M.D.; Matthews, D.L.; Goldstein, W.H.; Stewart, R.E. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

    1992-08-01

    We report the observation of high-gain lasing in laser-heated exploding-foil Ag targets at pump irradiances {ge}6{times}10{sup 14} W/cm{sup 2}. The measured gain coefficients on the dominant Ne-like {ital J}=2{r arrow}1 transitions are determined to be 9.4{plus minus}1.5 cm{sup {minus}1} for (2{ital p}{sub 3/2})3{ital p}{sub 3/2}{r arrow}(2{ital p}{sub 3/2})3{ital s} at 9.9365 nm and 6.4{sub {minus}1.5}{sup +2.0} cm{sup {minus}1} for (2{ital p}{sub 1/2})3{ital p}{sub 3/2}{r arrow}(2{ital p}{sub 1/2})3{ital s} at 10.0377 nm. These are the highest gain coefficients yet observed to our knowledge for any short-wavelength laser. Gain is observed on three other Ne-like lines including a {ital J}=0{r arrow}1 transition at 8.1563 nm, the shortest wavelength yet observed to our knowledge for a Ne-like x-ray laser.

  1. HIGH GAIN HARMONIC GENERATION X-RAY FREE ELECTRON LASER.

    SciTech Connect

    WU, J.; YU, L.H.

    2001-06-18

    We present the calculation on the performance of a High Gain Harmonic Generation (HGHG) X-ray Free Electron Laser (FEL) based on the high quality electron beam from the proposed Photoinjected Energy Recovery Linac (PERL) at the NSLS. We consider several sets of e-beam parameters. The calculation indicates that it is possible to produce a fully coherent FEL with a wavelength around 10 Angstrom, with a peak power of several GW. The high order harmonics will also be produced with a significant amount of peak power. One further attractive feature is the possibility to produce ultra short radiation pulses of about 10 fs based on such HGHG scheme.

  2. ZnO Nanowire UV Photodetectors with High Internal Gain

    Microsoft Academic Search

    C. Soci; A. Zhang; B. Xiang; S. A. Dayeh; D. P. R. Aplin; X. Y. Bao; Y. H. Lo; D. Wang

    2007-01-01

    ZnO nanowire (NW) visible-blind UV photodetectors with internal photoconductive gain as high as G 10 8 have been fabricated and characterized. The photoconduction mechanism in these devices has been elucidated by means of time-resolved measurements spanning a wide temporal domain, from 10-9 to 102 s, revealing the coexistence of fast (Ù 20 ns) and slow (Ù 10 s) components of

  3. Coherent backscattering from high-gain scattering media

    NASA Astrophysics Data System (ADS)

    de Oliveira, Paulo C.; Perkins, A. E.; Lawandy, N. M.

    1996-10-01

    We report on experimental observations of coherent backscattering signals from high-gain scattering media in the regime where significant amplification takes place over one transport length. Our samples consist of polymer sheets containing optically pumped dyes as the amplifying medium, with TiO2 nanoparticles providing the scattering. The width of the backscattering cones narrows with increasing amplification, while the enhancement factor remains unchanged.

  4. Design issues for a laboratory high gain fusion facility

    SciTech Connect

    Hogan, W.J.

    1987-11-02

    In an inertial fusion laboratory high gain facility, experiments will be carried out with up to 1000 MJ of thermonuclear yield. The experiment area of such a facility will include many systems and structures that will have to operate successfully in the difficult environment created by the sudden large energy release. This paper estimates many of the nuclear effects that will occur, discusses the implied design issues and suggests possible solutions so that a useful experimental facility can be built. 4 figs.

  5. Functional characterization of a high-gain BJT radiation detector

    Microsoft Academic Search

    Giovanni Batignani; Stefano Bettarini; Mario Bondioli; Maurizio Boscardin; Luciano Bosisio; Gian-Franco Dalla Betta; Selenia Dittongo; Francesco Forti; Gabriele Giacomini; Marcello A. Giorgi; Paolo Gregori; Claudio Piemonte; Irina Rachevskaia; Sabina Ronchin; Nicola Zorzi

    2005-01-01

    n-p-n bipolar phototransistors have been designed and fabricated on high-resistivity silicon substrates. A technology featuring a double implant for the emitter allowed us to obtain a typical current gain of about 600. The device has been tested with ? particles from a 239Pu source, ? particles from 90Sr, and X-rays from 241Am using a simple experimental setup, where the detector

  6. High-Gain Harmonic-Generation Free-Electron Laser

    Microsoft Academic Search

    L.-H. Yu; M. Babzien; I. Ben-Zvi; L. F. DiMauro; A. Doyuran; W. Graves; E. Johnson; S. Krinsky; R. Malone; I. Pogorelsky; J. Skaritka; G. Rakowsky; L. Solomon; X. J. Wang; M. Woodle; V. Yakimenko; S. G. Biedron; J. N. Galayda; E. Gluskin; J. Jagger; V. Sajaev; I. Vasserman; OTD-APS

    2000-01-01

    A high-gain harmonic-generation free-electron laser is demonstrated. Our approach uses a laser-seeded free-electron laser to produce amplified, longitudinally coherent, Fourier transform-limited output at a harmonic of the seed laser. A seed carbon dioxide laser at a wavelength of 10.6 micrometers produced saturated, amplified free-electron laser output at the second-harmonic wavelength, 5.3 micrometers. The experiment verifies the theoretical foundation for the

  7. High gain x-ray lasers pumped by transient collisional excitation

    SciTech Connect

    Dunn, J., LLNL

    1998-06-16

    We present recent results of x-ray laser amplification of spontaneous emission in Ne-like and Ni-like transient collisional excitation schemes. The plasma formation, ionization and collisional excitation can be optimized using two laser pulses of 1 ns and 1 ps duration at table-top energies of 5 J in each beam. High gain of 35 cm{sup -1} has been measured on the 147 {Angstrom} 4d{r_arrow}4p J=0{r_arrow}1 transition of Ni-like Pd and is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse. We report the dependence of the x-ray laser line intensity on the laser plasma conditions and compare the experimental measurements with hydrodynamic and atomic kinetics simulations for Ne-like and Ni-like lasing.

  8. A high gain active photonic antenna for high speed backhaul link: A system analysis

    Microsoft Academic Search

    Teguh Prakoso; Razali Ngah; Tharek Abdul Rahman; Zabih Ghassemlooy

    2010-01-01

    A high-gain active photonic antenna is proposed to provide long distance optical and wireless backhaul link. To support service for long wireless distance, RF amplifier and high gain antenna is integrated to the photonic antenna concept. High speed feature is achieved through utilization of simultaneous multi-channel WLAN transmitted through the photonic antenna. Using this notion, the use of four simultaneous

  9. The Tie that Binds: The Role of Self-Reported High School Gains in Self-Reported College Gains

    ERIC Educational Resources Information Center

    Seifert, Tricia A.; Asel, Ashley M.

    2011-01-01

    The purpose of this chapter is to investigate the extent to which students' retrospective self-reported gains from high school are associated with college self-reported gains. As such, the chapter offers an empirical test of how accounting for one's predisposition to report educational impact changes estimates of the effects of college experiences…

  10. Double-Boosted High-Gain Servo Controller for High-Rotation-Speed Optical Disk Drives

    Microsoft Academic Search

    Tomoharu Mukasa; Yoshiyuki Urakawa

    2008-01-01

    We propose the use of a double-boosted high-gain servo controller for high-rotation-speed optical disk drives. This controller consists of two low-frequency boosters and a lead-lag compensator. Additionally, we use a pole-placement method to design parameters of the controller to obtain the highest low-frequency gain. This controller increases low-frequency gain extremely without decrease in phase margin. We applied this controller to

  11. Collective instabilities and high-gain regime free electron laser

    SciTech Connect

    Bonifacio, R.; Pellegrini, C.; Narducci, L.M.

    1983-01-01

    The operation of Free Electron Lasers (FEL) in the short wavelength region, lambda < 1000 A, requires a large field amplification per undulator pass in order to overcome the large losses of the optical cavity at these wavelengths. Systems based on the combination of a storage ring and of a free electron laser can provide this large amplification. In fact, for these systems small-signal gains of the order of 100 to 1000% per pass have been estimated. Of course, at this level of amplification, the small-signal gain formula is no longer appropriate and a more accurate description of the FEL is required. FEL studies in the high-gain regime have been carried out by many authors who have shown that, with an appropriate selection of the electron density, detuning, and undulator length, it is possible to produce an exponential growth of both the radiation field and of the electron bunching. This is the result of the emergence of a collective instability for the electron beam-undulator-radiation field system. The conditions for the onset of this instability were studied and the characteristic complex frequencies of the FEL system are derived.

  12. 56.6 DB High Gain L-Band Edfa Utilizing Short-Length Highly-Doped Erbium Rare-Earth Material

    NASA Astrophysics Data System (ADS)

    Al-Mansoori, M. H.; Al-Ghaithi, W. S.

    2014-07-01

    In this paper, we experimentally investigate the performance of an efficient high gain L-band erbium-doped fiber (EDF) amplifier structure utilizing short-length highly-doped erbium rare-earth material with a single pump source. The amplifier gain and noise figure variation for different amplifier structures have been investigated. A filter is used to reduce the self-saturation effect and suppress the C-band amplified spontaneous emission (ASE) noise. The amplifier achieves a signal gain of 56.6 dB with a low noise figure of 4.8 dB at -50 dBm input signal power using only 8 m of EDF length. The amplifier gain shows significant improvement of 6 dB with C/L band coupler and 13 dB with tunable-band pass filter compared to amplifier structure without ASE suppression.

  13. Theory for high gain, high power free electron lasers

    SciTech Connect

    Colson, W.B.

    1990-01-01

    During this contracting period, the understanding of the effects of beam quality has improved both experimentally and theoretically. There have been three publications and a few talks at LLNL to serve a interim reports. The research included the derivation of better high-efficiency equations for describing the free electron laser (FEL) in the strongly saturated regime. The equations retain much of the simplicity of the old theory, but are accurate for high energy extraction. 20 refs., 16 figs.

  14. A high gain antenna system for airborne satellite communication applications

    NASA Technical Reports Server (NTRS)

    Maritan, M.; Borgford, M.

    1990-01-01

    A high gain antenna for commercial aviation satellites communication is discussed. Electromagnetic and practical design considerations as well as candidate systems implementation are presented. An evaluation of these implementation schemes is given, resulting in the selection of a simple top mounted aerodynamic phased array antenna with a remotely located beam steering unit. This concept has been developed into a popular product known as the Canadian Marconi Company CMA-2100. A description of the technical details is followed by a summary of results from the first production antennas.

  15. Avoiding Obstructions in Aiming a High-Gain Antenna

    NASA Technical Reports Server (NTRS)

    Edmonds, Karina

    2006-01-01

    The High Gain Antenna Pointing and Obstruction Avoidance software performs computations for pointing a Mars Rover high-gain antenna for communication with Earth while (1) avoiding line-of-sight obstructions (the Martian terrain and other parts of the Rover) that would block communication and (2) taking account of limits in ranges of motion of antenna gimbals and of kinematic singularities in gimbal mechanisms. The software uses simplified geometric models of obstructions and of the trajectory of the Earth in the Martian sky(see figure). It treats all obstructions according to a generalized approach, computing and continually updating the time remaining before interception of each obstruction. In cases in which the gimbal-mechanism design allows two aiming solutions, the algorithm chooses the solution that provides the longest obstruction-free Earth-tracking time. If the communication session continues until an obstruction is encountered in the current pointing solution and the other solution is now unobstructed, then the algorithm automatically switches to the other position. This software also notifies communication- managing software to cease transmission during the switch to the unobstructed position, resuming it when the switch is complete.

  16. High power gain for stimulated Raman amplification in CuAlS2

    NASA Astrophysics Data System (ADS)

    Bairamov, B. H.; Aydinli, A.; Bodnar', I. V.; Rud', Yu. V.; Nogoduyko, V. K.; Toporov, V. V.

    1996-11-01

    The spontaneous Raman spectra of the chalcopyrite structure crystal CuAlS2, which is promising for nonlinear optical applications, has been investigated at 8 and 300 K. The main aim of this study is to compare the absolute spontaneous Raman scattering efficiency in CuAlS2 crystals with that of their isomorphous analog, zinc-blende structure GaP crystals, known as one of the most efficient materials for Raman amplification. Observation of a high value of absolute scattering efficiency S/L d? (where S is the fraction of incident power that scatters into the solid angle d ? and L is the optical path length with S/L d?=9.5×10-5 cm-1 sr-1), together with relatively narrow linewidth (?=5.1 cm-1, full width at half maximum at room temperature and ?=1.5 cm-1 at 8 K for the strongest ?1 phonon mode of CuAlS2 at 314 cm-1) indicate that CuAlS2 has the highest value of the stimulated Raman gain coefficient gs/I where I is the incident laser power density. The calculated value of this gain is gs/I=2.1×10-6 cm-1/W at 300 K and 5.0×10-6 cm/W, at 8 K for 514.5 nm laser excitation, and is larger than those for the appropriate vibrational modes of various materials (including GaP, LiNbO3, Ba2NbO5O15, CS2, and H2) investigated so far. The calculations show that cw Raman oscillator operation in CuAlS2 is feasible with low power threshold of pump laser.

  17. Wavelength swept amplified spontaneous emission source for high speed retinal optical coherence tomography at 1060 nm.

    PubMed

    Eigenwillig, Christoph M; Klein, Thomas; Wieser, Wolfgang; Biedermann, Benjamin R; Huber, Robert

    2011-08-01

    The wavelength swept amplified spontaneous emission (ASE) source presented in this paper is an alternative approach to realize a light source for high speed swept source optical coherence tomography (OCT). ASE alternately passes a cascade of different optical gain elements and tunable optical bandpass filters. In this work we show for the first time a wavelength swept ASE source in the 1060 nm wavelength range, enabling high speed retinal OCT imaging. We demonstrate ultra-rapid retinal OCT at a line rate of 170 kHz, a record sweep rate at 1060 nm of 340 kHz with 70 nm full sweep width, enabling an axial resolution of 11 ?m. Two different implementations of the source are characterized and compared to each other. The last gain element is either a semiconductor optical amplifier or an Ytterbium-doped fibre amplifier enabling high average output power of >40 mW. Various biophotonic imaging examples provide a wide range of quality benchmarks achievable with such sources. PMID:21780301

  18. High gain antenna pointing on the Mars Exploration Rovers

    NASA Technical Reports Server (NTRS)

    Vanelli, C. Anthony; Ali, Khaled S.

    2005-01-01

    This paper describes the algorithm used to point the high gain antennae on NASA/JPL's Mars Exploration Rovers. The gimballed antennae must track the Earth as it moves across the Martian sky during communication sessions. The algorithm accounts for (1) gimbal range limitations, (2) obstructions both on the rover and in the surrounding environment, (3) kinematic singularities in the gimbal design, and (4) up to two joint-space solutions for a given pointing direction. The algorithm computes the intercept-times for each of the occlusions and chooses the jointspace solution that provides the longest track time before encountering an occlusion. Upon encountering an occlusion, the pointing algorithm automatically switches to the other joint-space solution if it is not also occluded. The algorithm has successfully provided flop-free pointing for both rovers throughout the mission.

  19. High gain GaAs photoconductive semiconductor switches: Switch longevity

    SciTech Connect

    Loubriel, G.M.; Zutavern, F.J.; Mar, A. [and others

    1998-07-01

    Optically activated, high gain GaAs switches are being tested for many different pulsed power applications that require long lifetime (longevity). The switches have p and n contact metallization (with intentional or unintentional dopants) configured in such a way as to produce p-i-n or n-i-n switches. The longevity of the switches is determined by circuit parameters and by the ability of the contacts to resist erosion. This paper will describe how the switches performed in test-beds designed to measure switch longevity. The best longevity was achieved with switches made with diffused contacts, achieving over 50 million pulses at 10 A and over 2 million pulses at 80 A.

  20. 75 FR 61228 - Board Meeting: Technical Lessons Gained From High-Level Nuclear Waste Disposal Efforts

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-04

    ...NUCLEAR WASTE TECHNICAL REVIEW BOARD Board Meeting: Technical Lessons Gained From High-Level Nuclear Waste Disposal Efforts Pursuant...high-level radioactive waste. The Board will consider technical lessons that can be gained from those experiences that may be...

  1. Superradiance in the high-gain free-electron laser

    SciTech Connect

    Bonifacio, R.; McNeil, B.W.J.; Pierini, P. (Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano, Italy (IT))

    1989-10-15

    In this paper we describe the effects of slippage on the single-pass high-gain free-electron laser (FEL) amplifier. We use a one-dimensional computational code to show the existence of two new dynamical regimes characterized by a dimensionless parameter {ital K}, which is a measure of the slippage in one gain length. We define the long-pulse limit to be when {ital K}{much lt}1 or the electron pulse length {ital L}{sub {ital e}} is much greater than a properly defined cooperation length'' {ital L}{sub {ital c}} ({ital L}{sub {ital e}}{much gt}L{sub c}). In this case we find that only the leading region of the propagating radiation pulse exhibits the usual steady-state behavior, with peak power proportional to {ital n}{sub {ital e}}{sup 4/3} (where {ital n}{sub {ital e}} is the electron-beam density). The trailing (slippage) region exhibits a spiking behavior with peak intensities reaching many times the saturated intensity predicted by steady-state theory. We define the short-pulse regime to be when {ital K}{approx gt}1 ({ital L}{sub {ital e}}{approx lt}L{sub c}). In this regime the peak power emitted by the electrons does not scale as {ital n}{sub {ital e}}{sup 4/3}, as predicted by steady-state theory, but scales as {ital n}{sub {ital e}}{sup 2}, which is typical of superradiant behavior. Furthermore, energy is extracted from the electrons in a continuous way, with no steady-state synchrotron oscillatory-type behavior.

  2. Machine Copy for Proofreading, 2005 ANALYSIS AND DESIGN OF A HIGH-GAIN ANTENNA

    E-print Network

    Paris-Sud XI, Université de

    . Abstract--In this paper, a new high-gain antenna made from a monopole embedded in a crystal, also called. INTRODUCTION. Electromagnetic bandgap (EBG) materials, also known as photonic crystals [1], have been and results of a new high-gain antenna based on a metallic crystal. High-gain, low-cost antennas using

  3. High gain H? feedback control for an anti-air missile

    Microsoft Academic Search

    Rowena L. Eberhardt; Kevin A. Wise

    1993-01-01

    A singular perturbation approach is applied to characterize the properties of linear time invariant high gain feedback systems with additive disturbance. Using the two time scale property of the high gain system, the near optimum high gain H? state regulator is the composition of the slow subsystem H? state regulator and the fast subsystem LQ state regulator. This approach is

  4. Development of a 3D FEL code for the simulation of a high-gain harmonic generation experiment.

    SciTech Connect

    Biedron, S. G.

    1999-02-26

    Over the last few years, there has been a growing interest in self-amplified spontaneous emission (SASE) free-electron lasers (FELs) as a means for achieving a fourth-generation light source. In order to correctly and easily simulate the many configurations that have been suggested, such as multi-segmented wigglers and the method of high-gain harmonic generation, we have developed a robust three-dimensional code. The specifics of the code, the comparison to the linear theory as well as future plans will be presented.

  5. Solar Dynamics Observatory High Gain Antenna Handover Planning

    NASA Technical Reports Server (NTRS)

    Hashmall, Joseph A.; Mann, Laurie

    2007-01-01

    The Solar Dynamics Observatory (SDO) is planned to launch in early 2009 as a mission to study the solar variability and its impact on Earth. To best satisfy its science goal, SDO will fly in a geosynchronous orbit with an inclination of approximately 29 deg. The spacecraft attitude is designed so that the science instruments point directly at the Sun with high accuracy. One of SDO's principal requirements is to obtain long periods of uninterrupted observations. The observations have an extremely high data volume so SDO must be in continuous contact with the ground during the observation periods. To maintain this contact, SDO is equipped with a pair of high gain antennas (HGAs) transmitting to a pair of ground antennas at the SDO ground station (SDOGS) located in White Sands, New Mexico. Either HGA can transmit to either SDOGS antenna. Neither HGA can be powered down. During a portion of each year, each of the HGA beams will intersect with the SDO body for a portion of the orbit. The original SDO antenna contact plan used each HGA for the half of each year during which its beam would not intersect the spacecraft. No data would be lost except, possibly, when switching from one antenna to another. After this plan was adopted, further analysis showed that daily handovers would be necessary for significant periods of the year. This unexpected need for extensive handovers necessitated that a handover design be developed to minimize the impact on the mission. This antenna handover design was developed and successfully tested with simulated data using the slew rate limits from preliminary jitter analysis. Subsequent analysis provided significant revision of allowed rates requiring modification of the handover plans.

  6. Enhancement of optical gain and amplified spontaneous emission due to waveguide geometry in the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene

    NASA Astrophysics Data System (ADS)

    Lampert, Zach E.; Papanikolas, John M.; Lewis Reynolds, C.

    2013-02-01

    We report enhanced amplified spontaneous emission (ASE) and optical gain performance in a conjugated polymer (CP)-based thin film waveguide (WG) Si(100)/SiO2/poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) by encapsulating the active layer with a transparent dielectric film of poly(methyl methacrylate) (PMMA). With index matched SiO2 and PMMA claddings, symmetric WGs are formed that exhibit increased mode confinement and reduced propagation loss enabling lower ASE threshold (40%) and higher optical gain (50%) compared to Si(100)/SiO2/MEH-PPV/air asymmetric WGs. An extremely large net gain coefficient of 500 cm-1 is achieved under picosecond pulse excitation, which is >4× larger than values previously reported in the literature. Fabrication of symmetric WGs requires no complex processing techniques, thus offering a simple, low-cost approach for effectively controlling the ASE behavior of CP-based WGs and related optical devices.

  7. Mechanisms underlying obesity resistance associated with high spontaneous physical activity

    PubMed Central

    Teske, Jennifer A.; Billington, Charles J.; Kotz, Catherine M.

    2013-01-01

    Obesity resistance due to elevated orexin signaling is accompanied by high levels of spontaneous physical activity (SPA). The behavioral and neural mechanisms underlying this observation have not been fully worked out. We determined the contribution of hypothalamic orexin receptors (OXR) to SPA stimulated by orexin A (OXA), whether OXA-stimulated SPA was secondary to arousal and whether voluntary wheel running led to compensations in 24-h SPA. We further tested whether orexin action on dopamine one receptors (DA1R) in the substantia nigra (SN) plays an important role in generation of SPA. To test this, SPA response was determined in lean and obese rats with cannulae targeted towards the rostral lateral hypothalamus (rLH) or SN. Sleep/wake states were also measured in rats with rLH cannula and EEG/EMG radiotelemetry transmitters. SPA in lean rats was more sensitive to antagonism of the orexin 1 receptor (OX1R) and in the early response to the orexin 2 agonist. OXA increased arousal equally in lean and obese rodents, which is discordant from the greater SPA response in lean rats. Obesity resistant rats ran more and wheel running was directly related to 24-h SPA levels. The OX1R antagonist, SB-334867-A, and the DA1R antagonist, SCH3390, in SN more effectively reduced SPA stimulated by OXA in OR rats. These data suggest OXA-stimulated SPA is not secondary to enhanced arousal, propensity for SPA parallels inclination to run and that orexin action on dopaminergic neurons in SN may participate in mediation of SPA and running wheel activity. PMID:24161277

  8. Theoretical simulations of the synchrotron instability in high gain, high power free electron lasers

    SciTech Connect

    Colson, W.B. (Berkeley Research Associates, Inc., CA (USA))

    1985-01-01

    The ELF FEL experiments at LLNL in 1985 provide the first results of a free electron laser (FEL) operating in the high-current, high-gain, high-efficiency regime. Initial experiments measured 15.6dB/m gain at {lambda} {approx} 8mm radiation wavelength. Much of the understanding of the ELF experiment comes from simulations like LLNL's FRED that are run on large CRAY computers. In this brief study, a simpler model is used to explain weak-field gain and saturation. Several physical quantities are expressed in a useful dimensionless form, and serve to relate the ELF FEL to other FEL configurations and to future amplifier designs. The trapped-particle instability is explored for parameters close to the original experiments, and parameters representative of future improvements. 8 refs., 9 figs.

  9. High gain multigap avalanche detectors for Cerenkov ring imaging

    SciTech Connect

    Gilmore, R.S.; Lavender, W.M.; Leith, D.W.G.S.; Williams, S.H.

    1980-10-01

    We report on a continuing study of multigap parallel plate avalanche chambers, primarily as photoelectron detectors for use with Cerenkov ring imaging counters. By suitable control of the fields in successive gaps and by introducing screens to reduce photon feedback to the cathode the gain many be increased considerably. We have obtained gains in excess of 6 x 10/sup 7/ for photoelectrons with a good pulse height spectrum and expect to increase this further. We discuss the use of resistive anodes to give avalanche positions in two dimensions by charge division.

  10. High Peak Power Gain Switched Flared Waveguide Lasers

    SciTech Connect

    Chow, W.W.; Indik, R.; Koch, S.W.; Mar, Alan, Vawter, G. Allen; Moloney, J.

    1999-08-05

    We gain-switch flared waveguide lasers to obtain 14.5 W peak powers and 0.5 nJ pulse energies with laser structures compatible with the generation of diffraction-limited beams. The results are in excellent agreement with a microscopic laser model.

  11. Microsecond gain-switched master oscillator power amplifier (1958 nm) with high pulse energy

    NASA Astrophysics Data System (ADS)

    Yin, Ke; Yang, Weiqiang; Zhang, Bin; Li, Ying; Hou, Jing

    2014-02-01

    An all-fibre master oscillator power amplifier (MOPA) emitting high-energy pulses at 1958 nm is presented. The seed laser is a microsecond gain-switched thulium-doped fibre laser (TDFL) pumped with a commercial 1550-nm pulsed fibre laser. The TDFL operates at a repetition rate f in the range of 10 to 100 kHz. The two-stage thulium-doped fibre amplifier is built to scale the energy of the pulses generated by the seed laser. The maximum output pulse energy higher than 0.5 mJ at 10 kHz is achieved which is comparable with the theoretical maximum extractable pulse energy. The slope efficiency of the second stage amplifier with respect to the pump power is 30.4% at f = 10 kHz. The wavelength of the output pulse laser is centred near 1958 nm at a spectral width of 0.25 nm after amplification. Neither nonlinear effects nor significant amplified spontaneous emission (ASE) is observed in the amplification experiments.

  12. MIMO High Gain Trajectory Linearization Observer Design and Hardware-in-the-loop Test

    Microsoft Academic Search

    Rui Huang; J. Jim Zhu

    2007-01-01

    In this paper, we extend the previous TLO results for SISO trajecotory linearization observer (TLO) to MIMO nonlinear dynamic systems. Regular perturbation and nonlinear high-gain observer theories are applied to analyze the stability and robustness of the TLO method. The high-gain observer theory has been extended from time-invariant cases to time-varying cases using a singular perturbation approach. The high-gain TLO

  13. Stability in high gain plasmas in DIII-D

    SciTech Connect

    Lazarus, E.A.; Houlberg, W.A.; Murakami, M.; Wade, M.R. [and others

    1996-10-01

    Fusion power gain has been increased by a factor of 3 in DIII-D plasmas through the use of strong discharge shaping and tailoring of the pressure and current density profiles. H-mode plasmas with weak or negative central magnetic shear are found to have neoclassical ion confinement throughout most of the plasma volume. Improved MHD stability is achieved by controlling the plasma pressure profile width. The highest fusion power gain Q (ratio of fusion power to input power) in deuterium plasmas was 0.0015, which extrapolates to an equivalent Q of 0.32 in a deuterium-tritium plasma and is similar to values achieved in tokamaks of larger size and magnetic fields.

  14. High gain CMOS UWB LNA employing thermal noise cancellation

    Microsoft Academic Search

    Mehdi Forouzanfar; Sasan Naseh

    2009-01-01

    This paper presents a 3.1-10.6 GHz CMOS LNA designed with a 0.18 mum CMOS technology. In this amplifier, cancellation of two important noise sources in the amplifier, plus increasing effective transconductance of the input stage, reduce the noise figure (NF) of the amplifier. Noise canceling LNAs suffer from relatively low power gain. In contrast, this paper presents an ultra-wideband LNA

  15. NUTRIENT REQUIREMENTS OF HIGH-LEAN GAIN SWINE AT A HIGH ENVIRONMENTAL TEMPERATURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High-lean gain swine initially averaging 85 kg were assigned to 96 individual pens and given one of six diets ranging in the ratio of Total Ileal Digestible (TID) Lysine:Metabolizable Energy (ME) of 1.23 to 2.28 g/MCal. Pigs and feed intake were weighed weekly and backfat was measured on two week i...

  16. Doped contacts for high-longevity optically activated, high gain GaAs photoconductive semiconductor switches

    Microsoft Academic Search

    ALAN MAR; GUILLERMO M. LOUBRIEL; FRED J. ZUTAVERN; M. W. O'Malley; WESLEY D. HELGESON; DARWIN JAMES BROWN; HAROLD P. HJALMARSON; ALBERT G. BACA; R. L. Thornton; R. D. Donaldson

    1999-01-01

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 50 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer beneath the PCSS contacts which is very effective in the suppression of filament formation and alleviating current crowding to improve the longevity of PCSS. Damage-free operation is

  17. Gain saturation effects in high-speed, multichannel erbium-doped fiber amplifiers at ?=1.53 ?m

    Microsoft Academic Search

    EMMANUEL DESURVIRE; C. RANDY GILES; JAY R. SIMPSON

    1989-01-01

    Gain compression effects during multichannel signal amplification in an erbium-doped fiber amplifier at ?=1.53 are investigated. A theory is presented that accurately models the observed amplified spontaneous emission spectra, signal gains, and saturation effects. Measurements of the gain dynamics show recovery times in the 1-ms range, indicating that the fiber amplifier is immune to interchannel interference over a wide range

  18. High cell density induces spontaneous bifurcations of dissolved oxygen controllers during CHO cell fermentations.

    PubMed

    Chung, John D; Chang, Conway C; Groves, James Ashley

    2003-10-20

    High cell density cultures of CHO cells growing in a bioreactor under dissolved oxygen control were found to undergo spontaneous bifurcations and a subsequent loss of stability some time into the fermentation. This loss of stability was manifested by sustained and amplified oscillations in the bioreactor dissolved oxygen concentration and in the oxygen gas flow rate to the reactor. To identify potential biological and operational causes for the phenomenon, linear stability analysis was applied in a neighborhood of the experimentally observed bifurcation point. The analysis revealed that two steady state process gains, K(P1) and K(P2), regulated k(l)a and gas phase oxygen concentration inputs, respectively, and the magnitude of K(P1) was found to determine system stability about the bifurcation point. The magnitude of K(P1), and hence the corresponding open-loop steady state gain K(OL1), scaled linearly with the bioreactor cell density, increasing with increasing cell density. These results allowed the generation of a fermentation stability diagram, which partitioned K(C)-N operating space into stable and unstable regions separated by the loci of predicted critically stable controller constants, K(C,critical), as a function of bioreactor cell density. This consistency of this operating diagram with experimentally observed changes in system stability was demonstrated. We conclude that time-dependent increases in cell density are the cause of the observed instabilities and that cell density is the critical bifurcation parameter. The results of this study should be readily applicable to the design of a more robust controller. PMID:12966579

  19. High gain 1.3-?m GaInNAs SOA with fast gain dynamics and enhanced temperature stability

    NASA Astrophysics Data System (ADS)

    Fitsios, D.; Giannoulis, G.; Iliadis, N.; Korpijärvi, V.-M.; Viheriälä, J.; Laakso, A.; Dris, S.; Spyropoulou, M.; Avramopoulos, H.; Kanellos, G. T.; Pleros, N.; Guina, M.

    2014-03-01

    Semiconductor optical amplifiers (SOAs) are a well-established solution of optical access networks. They could prove an enabling technology for DataCom by offering extended range of active optical functionalities. However, in such costand energy-critical applications, high-integration densities increase the operational temperatures and require powerhungry external cooling. Taking a step further towards improving the cost and energy effectiveness of active optical components, we report on the development of a GaInNAs/GaAs (dilute nitride) SOA operating at 1.3?m that exhibits a gain value of 28 dB and combined with excellent temperature stability owing to the large conduction band offset between GaInNAs quantum well and GaAs barrier. Moreover, the characterization results reveal almost no gain variation around the 1320 nm region for a temperature range from 20° to 50° C. The gain recovery time attained values as short as 100 ps, allowing implementation of various signal processing functionalities at 10 Gb/s. The combined parameters are very attractive for application in photonic integrated circuits requiring uncooled operation and thus minimizing power consumption. Moreover, as a result of the insensitivity to heating issues, a higher number of active elements can be integrated on chip-scale circuitry, allowing for higher integration densities and more complex optical on-chip functions. Such component could prove essential for next generation DataCom networks.

  20. Dual-carrier multiplication high-gain MWIR strained layer superlattice impact ionization engineered avalanche photodiodes

    E-print Network

    Krishna, Sanjay

    Dual-carrier multiplication high-gain MWIR strained layer superlattice impact ionization engineered multiplication extremely high gain MWIR InAs/InGaSb Type II strained layer superlattice (T2SLS) impact ionization engineered (I2E) APD was designed and simulated. Spatially separated T2SLS electron and hole multiplication

  1. Statistical theory of high-gain free-electron laser saturation Julien Barr,1,2,

    E-print Network

    Dauxois, Thierry

    Statistical theory of high-gain free-electron laser saturation Julien Barré,1,2, * Thierry Dauxois, to predict the saturated state of a single-pass, high-gain free-electron laser. In analogy with the violent of generating coherent and tunable radiation sources, such as free-electron lasers (FELs). In this case

  2. SOFT X-RAY FEL BY CASCADING STAGES OF HIGH GAIN HARMONIC GENERATION.

    SciTech Connect

    YU,L.H.

    2003-04-17

    Short wavelength Free-Electron Lasers are perceived as the next generation of synchrotron light sources. In the past decade, significant advances have been made in the theory and technology of high brightness electron beams and single pass FELs. These developments facilitate the construction of practical VUV FELs and make x-ray FELs possible. Self-Amplified Spontaneous Emission (SASE) and High Gain Harmonic Generation (HGHG)[17-19] are the two leading candidates for x-ray FELs. The first lasing of HGHG proof-of-principle experiment succeeded in August, 1999 in Brookhaven National Laboratory. The experimental results agree with the theory prediction. Compared with SASE FEL, the following advantages of HGHG FEL were confirmed; (1) Better longitudinal coherence, and hence, much narrower bandwidth than SASE. (2) More stable central wavelength, (3) More stable output energy. In this introduction, we will first briefly describe the principle of HGHG in Section A. Then in Section B, we give a general description about how to produce soft x-ray by cascading HGHG scheme. In section 2, we give a detailed description of the system design. Then, in section 3, we give a description of an analytical estimate for the HGHG process, and the calculation of the parameters of different parts of the system. The estimate is found to agree with simulation within about a factor 2 for most cases we studied. The stability issue, the sensitivity to parameter variation, the harmonic contents of the final output, and the noise degradation issue of such HGHG scheme are discussed in Section 4. The results are presented in Section 4. Finally, in Section 5, we will give some discussion of the challenges in development of the system. The conclusion is given in Section 6.

  3. High Gain Transformerless DC-DC Converters for Renewable Energy Sources 

    E-print Network

    Denniston, Nicholas Aaron

    2011-08-08

    efficiency. Simulations are used to verify the modeling approach and predict the performance at different power levels. Experimental prototypes for both low power and high power applications demonstrate the value of multiple module converters in high gain DC...

  4. A high-gain directly modulated L-band microwave optical link

    Microsoft Academic Search

    E. Ackerman; D. Kasemset; S. Wanuga; D. Hogue; J. Komiak

    1990-01-01

    A directly modulated microwave optical data link has yielded high gain. An efficient lossless impedance matching approach was used to maximize the transducer gains in the laser and detector matching networks. The free-space optical link operates at 900 MHz with a peak gain of 3.7 dB over a 3-dB bandwidth of 90 MHz. The link also exhibits a wide dynamic

  5. Collective instabilities and high-gain regime in a free electron laser

    Microsoft Academic Search

    R. Bonifacio; C. Pellegrini; L. M. Narducci

    1984-01-01

    The behavior of a free electron laser in the high gain regime and the conditions for the emergence of a collective instability in the electron beam-undulator-field system are studied. The equations presented here, in the appropriate limit, yield the traditional small gain formula. In the nonlinear regime, numerical solutions of the coupled equations of motion support the correctness of the

  6. In-circuit-measurement of parasitic elements in high gain high bandwidth low noise transimpedance amplifiers

    NASA Astrophysics Data System (ADS)

    Cochems, P.; Kirk, A.; Zimmermann, S.

    2014-12-01

    Parasitic elements play an important role in the development of every high performance circuit. In the case of high gain, high bandwidth transimpedance amplifiers, the most important parasitic elements are parasitic capacitances at the input and in the feedback path, which significantly influence the stability, the frequency response, and the noise of the amplifier. As these parasitic capacitances range from a few picofarads down to only a few femtofarads, it is nearly impossible to measure them accurately using traditional LCR meters. Unfortunately, they also cannot be easily determined from the transfer function of the transimpedance amplifier, as it contains several overlapping effects and its measurement is only possible when the circuit is already stable. Therefore, we developed an in-circuit measurement method utilizing minimal modifications to the input stage in order to measure its parasitic capacitances directly and with unconditional stability. Furthermore, using the data acquired with this measurement technique, we both proposed a model for the complicated frequency response of high value thick film resistors as they are used in high gain transimpedance amplifiers and optimized our transimpedance amplifier design.

  7. High room-temperature optical gain in Ga(NAsP)/Si heterostructures

    NASA Astrophysics Data System (ADS)

    Koukourakis, N.; Bückers, C.; Funke, D. A.; Gerhardt, N. C.; Liebich, S.; Chatterjee, S.; Lange, C.; Zimprich, M.; Volz, K.; Stolz, W.; Kunert, B.; Koch, S. W.; Hofmann, M. R.

    2012-02-01

    We analyze the modal gain of Ga(NAsP) multi quantum-well heterostructures pseudomorphically grown on (001) silicon substrate by metal-organic vapor-phase epitaxy. Using the variable stripe length method, we obtain high modal gain values up to 78 cm-1 at room temperature that are comparable to the values of common high quality III-V laser material. We find good agreement between experimental results and theoretically calculated gain spectra obtained using a microscopic model. The results underline the high potential of Ga(NAsP) as an active material for directly electrically pumped lasers on silicon substrate.

  8. Theta and High-Frequency Activity Mark Spontaneous Recall of Episodic Memories

    PubMed Central

    Burke, John F.; Sharan, Ashwini D.; Sperling, Michael R.; Ramayya, Ashwin G.; Evans, James J.; Healey, M. Karl; Beck, Erin N.; Davis, Kathryn A.; Lucas, Timothy H.

    2014-01-01

    Humans possess the remarkable ability to search their memory, allowing specific past episodes to be re-experienced spontaneously. Here, we administered a free recall test to 114 neurosurgical patients and used intracranial theta and high-frequency activity (HFA) to identify the spatiotemporal pattern of neural activity underlying spontaneous episodic retrieval. We found that retrieval evolved in three electrophysiological stages composed of: (1) early theta oscillations in the right temporal cortex, (2) increased HFA in the left hemisphere including the medial temporal lobe (MTL), left inferior frontal gyrus, as well as the ventrolateral temporal cortex, and (3) motor/language activation during vocalization of the retrieved item. Of these responses, increased HFA in the left MTL predicted recall performance. These results suggest that spontaneous recall of verbal episodic memories involves a spatiotemporal pattern of spectral changes across the brain; however, high-frequency activity in the left MTL represents a final common pathway of episodic retrieval. PMID:25143616

  9. High gain hybrid graphene-organic semiconductor phototransistors.

    PubMed

    Huisman, Everardus H; Shulga, Artem G; Zomer, Paul J; Tombros, Nikolaos; Bartesaghi, Davide; Bisri, Satria Zulkarnaen; Loi, Maria A; Koster, L Jan Anton; van Wees, Bart J

    2015-06-01

    Hybrid phototransistors of graphene and the organic semiconductor poly(3-hexylthiophene-2,5-diyl) (P3HT) are presented. Two types of phototransistors are demonstrated with a charge carrier transit time that differs by more than 6 orders of magnitude. High transit time devices are fabricated using a photoresist-free recipe to create large-area graphene transistors made out of graphene grown by chemical vapor deposition. Low transit time devices are fabricated out of mechanically exfoliated graphene on top of mechanically exfoliated hexagonal boron nitride using standard e-beam lithography. Responsivities exceeding 10(5) A/W are obtained for the low transit time devices. PMID:25961150

  10. Ceramic windows and gain media for high-energy lasers

    NASA Astrophysics Data System (ADS)

    Kim, Woohong; Villalobos, Guillermo; Baker, Colin; Frantz, Jesse; Shaw, Brandon; Bayya, Shyam; Sadowski, Bryan; Hunt, Michael; Aggarwal, Ishwar; Sanghera, Jasbinder

    2013-02-01

    Recent progress in high-quality transparent ceramic window materials (MgAl2O4 spinel and ?-SiC) and high-power solid-state laser materials (Yb?Y2O3, Yb?Lu2O3, and Ho?Lu2O3) is reported. Spinel ceramic demonstrates a record low-absorption loss of 6 ppm/cm at 1.06 ?m. The capability of fabricating various shapes and sizes of spinel ceramics is also demonstrated. We also report optical transparency from a ?-SiC ceramic fabricated by field assisted sintering technology (FAST). We report lasing in hot-pressed Yb?Y2O3 and Yb?Lu2O3 ceramic made from coprecipitated powder. The highest ever reported output power and efficiency from 10% doped Yb?Lu2O3 ceramic is also presented. Lasing oscillation from hot pressed composite of five-layered Yb?Y2O3 ceramic is also demonstrated for the first time.

  11. High gain proportional rf control stability at TESLA cavities Elmar Vogel

    E-print Network

    High gain proportional rf control stability at TESLA cavities Elmar Vogel Deutsches Elektronen) based on TESLA technology. Additional control loops improve the field regulation by treating repetitive loops is desirable for the strong suppression of nonpredictive and nonrepetitive disturbances. TESLA

  12. To kill a kangaroo: understanding the decision to pursue high-risk/high-gain resources

    PubMed Central

    Jones, James Holland; Bird, Rebecca Bliege; Bird, Douglas W.

    2013-01-01

    In this paper, we attempt to understand hunter–gatherer foraging decisions about prey that vary in both the mean and variance of energy return using an expected utility framework. We show that for skewed distributions of energetic returns, the standard linear variance discounting (LVD) model for risk-sensitive foraging can produce quite misleading results. In addition to creating difficulties for the LVD model, the skewed distributions characteristic of hunting returns create challenges for estimating probability distribution functions required for expected utility. We present a solution using a two-component finite mixture model for foraging returns. We then use detailed foraging returns data based on focal follows of individual hunters in Western Australia hunting for high-risk/high-gain (hill kangaroo) and relatively low-risk/low-gain (sand monitor) prey. Using probability densities for the two resources estimated from the mixture models, combined with theoretically sensible utility curves characterized by diminishing marginal utility for the highest returns, we find that the expected utility of the sand monitors greatly exceeds that of kangaroos despite the fact that the mean energy return for kangaroos is nearly twice as large as that for sand monitors. We conclude that the decision to hunt hill kangaroos does not arise simply as part of an energetic utility-maximization strategy and that additional social, political or symbolic benefits must accrue to hunters of this highly variable prey. PMID:23884091

  13. Microwave radiation from a high-gain free-electron laser amplifier

    Microsoft Academic Search

    T. J. Orzechowski; B. Anderson; W. M. Fawley; D. Prosnitz; E. T. Scharlemann; S. Yarema; D. Hopkins; A. C. Paul; A. M. Sessler; J. Wurtele

    1985-01-01

    A high-gain, high-extraction-efficiency, linearly polarized free-electron laser amplifier has been operated at 34.6 GHz. At low signal levels, expontential gain of 13.4 dB\\/m has been measured. With a 30-kW input signal, saturation was observed with an 80-MW output and a 5 percent extraction efficiency. The results are in good agreement with linear models at small signal levels and nonlinear models

  14. High-Performance Bound-to-Continuum Quantum-Cascade Lasers for Broad-Gain Applications

    Microsoft Academic Search

    Andreas Wittmann; Tobias Gresch; Emilio Gini; Lubos Hvozdara; Nicolas Hoyler; Marcella Giovannini; Jérôme Faist

    2008-01-01

    Abstract—Based on the bound-to-continuum,active region design, we shall present a high performance continuous-wave (CW) quantum-cascade laser. In contrast to high performance lasers based on a two-phonon resonance transition and a narrow linewidth 165 cm , the device presented here exhibits a spontaneous emission full-width at half-maximum as large as 295 cm . Thus, such devices are very suitable for broadband

  15. A High Phosphate Diet Lowers Blood Pressure in Spontaneously Hypertensive Rats

    Microsoft Academic Search

    J. M. BINDELS; SILVIA J. W. HILLEBRAND; JOHN M. P. WOKKE

    2010-01-01

    SUMMARY Plasma phosphate values are significantly lower in spontaneously hypertensive rats (SHR) than in normotensive Wistar-Kyoto rats (WKY). In this study, we increased plasma phosphate in SHR by a high dietary phosphate intake and followed the effects on blood pressure. Fifteen male WKY and 15 male SHR were housed from 4 weeks of age up to 26 weeks. At 4

  16. Polarization-insensitive optical gain characteristics of highly stacked InAs/GaAs quantum dots

    SciTech Connect

    Kita, Takashi; Suwa, Masaya; Kaizu, Toshiyuki; Harada, Yukihiro [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2014-06-21

    The polarized optical gain characteristics of highly stacked InAs/GaAs quantum dots (QDs) with a thin spacer layer fabricated on an n{sup +}-GaAs (001) substrate were studied in the sub-threshold gain region. Using a 4.0-nm-thick spacer layer, we realized an electronically coupled QD superlattice structure along the stacking direction, which enabled the enhancement of the optical gain of the [001] transverse-magnetic (TM) polarization component. We systematically studied the polarized electroluminescence properties of laser devices containing 30 and 40 stacked InAs/GaAs QDs. The net modal gain was analyzed using the Hakki-Paoli method. Owing to the in-plane shape anisotropy of QDs, the polarization sensitivity of the gain depends on the waveguide direction. The gain showing polarization isotropy between the TM and transverse-electric polarization components is high for the [110] waveguide structure, which occurs for higher amounts of stacked QDs. Conversely, the isotropy of the [?110] waveguide is easily achieved even if the stacking is relatively low, although the gain is small.

  17. Chronic intracerebroventricular injection of TLQP-21 prevents high fat diet induced weight gain in fast weight-gaining mice

    PubMed Central

    Bresciani, Elena; Bulgarelli, Ilaria; Rigamonti, Antonello E.; Pascucci, Tiziana; Levi, Andrea; Possenti, Roberta; Torsello, Antonio; Locatelli, Vittorio; Muller, Eugenio E.

    2009-01-01

    The vgf gene regulates energy homeostasis and the VGF-derived peptide TLQP-21 centrally exerts catabolic effects in mice and hamsters. Here, we investigate the effect of chronic intracerebroventricular (icv) injection of TLQP-21 in mice fed high fat diet (HFD). Fast weight-gaining mice injected with the peptide or cerebrospinal fluid were selected for physiological, endocrine, and molecular analysis. TLQP-21 selectively inhibited the increase in body weight and epididymal white adipose tissue (eWAT) weight induced by HFD in control animals despite both groups having a similar degree of hyperphagia. TLQP-21 normalized the increase in leptin and decrease in ghrelin while increasing epinephrine and epinephrine/norepinephrine ratio when compared to values in controls. Finally, HFD-TLQP-21 mice showed a selective increase of eWAT ?3-adrenergic receptor mRNA. Peroxisome-proliferator-activated-receptor-? and hormone-sensing-lipase mRNA were also upregulated. In conclusion, chronic icv infusion of TLQP-21 prevented the early phase of diet-induced obesity despite overfeeding. These effects were paralleled by activation of catabolic pathways within the eWAT. Our results further support a role for TLQP-21 as a catabolic neuropeptide. PMID:19247701

  18. Performance studies of high gain photomultiplier having Z-configuration of microchannel plates

    SciTech Connect

    Lo, C.C.; Leskovar, B.

    1980-11-01

    The characteristics of a high gain type ITT F4129 photomultiplier having three microchannel plates in cascade for electron multiplication have been investigated. These plates are in the Z-configuration. Measurements are given of the gain, dark current, cathode quantum efficiency, anode pulse linearity, electron transit time, single and multiphoton time spreads, fatigue, and pulse height resolution. The gain as a function of transverse magnetic field has been measured and is discussed. Photomultiplier characteristics as a function of the input pulse repetition frequency have also been investigated and discussed.

  19. Energy gain of highly charged ions in front of LiF

    SciTech Connect

    Haegg, L. [Stockholm Univ. (Sweden)]/[Oak Ridge National Lab., TN (United States)]/[Tennessee Univ., Knoxville, TN (United States); Reinhold, C.O. [Oak Ridge National Lab., TN (United States); Burgdoerfer, J. [Oak Ridge National Lab., TN (United States)]/[Tennessee Univ., Knoxville, TN (United States)

    1996-12-31

    We present estimates of the energy gain of highly charged ions approaching a LiF surface, based on a modified classical-over-barrier model for insulators. The analysis includes the energy gain by image acceleration as well as the deceleration due to charge-up of the surface in a staircase sequence. The role of the frequency-dependent dielectric response of LiF is emphasized. The resulting velocity dependent total energy gain is studied in detail and the results are compared with experimental data.

  20. Spontaneous emission control in high-extraction efficiency plasmonic crystals.

    PubMed

    Iwase, Hideo; Englund, Dirk; Vuckovic, Jelena

    2008-01-01

    We experimentally and theoretically investigate exciton-field coupling for the surface plasmon polariton (SPP) in waveguide-confined (WC) anti-symmetric modes of hexagonal plasmonic crystals in InP-TiOAu-TiO-Si heterostructures. The radiative decay time of the InP-based transverse magnetic (TM)-strained multi-quantum well (MQW) coupled to the SPP modes is observed to be 2.9-3.7 times shorter than that of a bare MQW wafer. Theoretically we find that 80 % of the enhanced photoluminescence (PL) is emitted into SPP modes, and 17 % of the enhanced PL is redirected into WC-anti-symmetric modes. In addition to the direct coupling of the excitons to the plasmonic modes, this demonstration is also useful for the development of high-temperature SPP lasers, the development of highly integrated photo-electrical devices, or miniaturized biosensors. PMID:18521174

  1. DEMONSTRATION OF 3D EFFECTS WITH HIGH GAIN AND EFFICIENCY IN A UV FEL OSCILLATOR

    SciTech Connect

    Stephen Benson; George Biallas; Keith Blackburn; James Boyce; Donald Bullard; James Coleman; Cody Dickover; David Douglas; Forrest Ellingsworth; Pavel Evtushenko; Carlos Hernandez-Garcia; Christopher Gould; Joseph Gubeli; David Hardy; Kevin Jordan; John Klopf; James Kortze; Robert Legg; Matthew Marchlik; Steven Moore; George Neil; Thomas Powers; Daniel Sexton; Michelle D. Shinn; Christopher Tennant; Richard Walker; Anne Watson; Gwyn Williams; Frederick Wilson; Shukui Zhang

    2011-03-01

    We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab. The high brightness of the electron beam leads to both gain and efficiency that cannot be reconciled with a one-dimensional model. Three-dimensional simulations do predict the performance with reasonable precision. Gain in excess of 100% per pass and an efficiency close to 1/2NW, where NW is the number of wiggler periods, is seen. The laser mirror tuning curves currently permit operation in the wavelength range of 438 to 362 nm. Another mirror set allows operation at longer wavelengths in the red with even higher gain and efficiency.

  2. A novel high-gain wide-band omnidirectional antenna for satellite communication application

    Microsoft Academic Search

    Yonggen Wang

    2009-01-01

    A novel antenna is proposed in this article, which has simple structure, high gain, wide-band, omni direction and small physical size characteristics. Through optimized design, the maximum gain in omnidirectional plane is 5.0dB, the 3dB beam width in the normal plane >=40°, the absolute VSWR band width of this antenna is 22.2GHz, and the relative VSWR band width is about

  3. Photonic band-gap materials for high-gain printed circuit antennas

    Microsoft Academic Search

    Hung-Yu David Yang; Nicolaos G. Alexopoulos; Eli Yablonovitch

    1997-01-01

    It is found through a vector integral-equation analysis and the reciprocity theorem that the gain of a microstrip antenna can be greatly enhanced with a photonic band-gap material layer either as the substrate or the superstrate. The beam angle is found to coincide with that of a leaky-wave mode of a planar-grating structure. This observation suggests that high gain is

  4. High-Gain Wideband Leaky-Wave Antenna Excited by Bowtie Element

    Microsoft Academic Search

    Shi-Wei Qu; Jia-Lin Li; Quan Xue

    2008-01-01

    A leaky-wave antenna with wideband and high-gain characteristics, excited by a rhombic bowtie element with round corners, is derived from a rectangular resonant cavity operating in TM111 mode. In the design procedure, a few particular techniques are used to enhance the antenna impedance bandwidth and gain, such as utilization of bowtie exciter and differentially-fed mechanism. The antenna is fed by

  5. 1000-V, 30-A 4H-SiC BJTs with high current gain

    Microsoft Academic Search

    Sumi Krishnaswami; Anant Agarwal; Sei-Hyung Ryu; Craig Capell; James Richmond; John Palmour; Santosh Balachandran; T. Paul Chow; Stephen Bayne; Bruce Geil; Kenneth Jones; Charles Scozzie

    2005-01-01

    This paper presents the development of 1000 V, 30A bipolar junction transistor (BJT) with high dc current gain in 4H-SiC. BJT devices with an active area of 3×3 mm2 showed a forward on-current of 30 A, which corresponds to a current density of 333 A\\/cm2, at a forward voltage drop of 2 V. A common-emitter current gain of 40, along

  6. Spontaneous Steinbeck: The Influence of Arts Integration, Primarily Spontaneous Painting, on the Reader Response of High School Juniors to "The Grapes of Wrath"

    ERIC Educational Resources Information Center

    Klasek, Catherine Huey

    2010-01-01

    This paper addresses my experience with a group of 11th grade students and their reading of The Grapes of Wrath (1939, 2002) by John Steinbeck. I questioned how the application of visual arts integration strategies, specifically the use of spontaneously created paintings, might influence the reader responses of my high school junior-level…

  7. High current gain InGaN=GaN HBTs with C operating temperature

    E-print Network

    Asbeck, Peter M.

    with high current gain [1­3] and high voltage operation [4, 5]. Initial work on nitride based HBTs focused charges that arise from compositional grading. The indium mole fraction was determined using X that the base layer is designed with a slight reverse grade, with 3% indium mole fraction at the collector side

  8. THE INTEGRAL EQUATION FOR A HIGH GAIN FEL N. A. Vinokurov *

    E-print Network

    Kemner, Ken

    1 THE INTEGRAL EQUATION FOR A HIGH GAIN FEL N. A. Vinokurov * Introduction The theory of a high of the Radiation Field Consider the electron beam propagating inside a long planar undulator. The Fourier transform velocity, k = c is the wave number, jx is the component of a current density, and A0x describes

  9. Transverse mode control in high gain free electron lasers with grazing incidence, unstable ring resonators

    Microsoft Academic Search

    Anup Bhowmik; Steven Bitterly; Paul Kennedy; Ross H. Labbe

    1988-01-01

    Grazing incidence, ring resonators have been proposed [1,2] to alleviate the problem of inordinately high irradiance on the intracavity optics in free electron lasers. Such resonators are also relatively compact, and consequently their alignment tolerances are more manageable. In this paper we present the transverse mode characteristics of an unstable, grazing incidence ring resonator under high gain conditions, and examine

  10. High gain GaAs photoconductive semiconductor switches for ground penetrating radar

    Microsoft Academic Search

    G. M. Loubriel; J. F. Aurand; M. T. Buttram; F. J. Zutavern; W. D. Helgeson; D. J. Brown

    1996-01-01

    The ability of high gain GaAs photoconductive semiconductor switches (PCSS) to deliver high peak power, fast risetime pulses when triggered with small laser diode arrays makes them suitable for their use in radars that rely on fast impulses. This type of direct time domain radar is uniquely suited for observation of large structures underground because it can operate at low

  11. Steady State Analysis of Short-wavelength, High-gainFELs in a Large Storage Ring

    SciTech Connect

    Huang, Z.; Bane, K.; Cai, Y.; Chao, A.; Hettel, R.; /SLAC; Pellegrini, C.; /UCLA

    2007-10-15

    Storage ring FELs have operated successfully in the low-gain regime using optical cavities. Discussions of a high-gain FEL in a storage ring typically involve a special bypass to decouple the FEL interaction from the storage ring dynamics. In this paper, we investigate the coupled dynamics of a high-gain FEL in a large storage ring such as PEP and analyze the equilibrium solution. We show that an FEL in the EUV and soft x-ray regimes can be integrated into a very bright storage ring and potentially provides three orders of magnitude improvement in the average brightness at these radiation wavelengths. We also discuss possibilities of seeding with HHG sources to obtain ultra-short, high-peak power EUV and soft x-ray pulses.

  12. High-gain X-ray free electron laser by beat-wave terahertz undulator

    SciTech Connect

    Chang, Chao; Hei, DongWei [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an City 710024 (China) [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an City 710024 (China); Institute of Energy, Tsinghua University, Beijing 100084 (China); Pellegrin, Claudio; Tantawi, Sami [SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94309 (United States)] [SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94309 (United States)

    2013-12-15

    The THz undulator has a higher gain to realize a much brighter X-ray at saturation, compared with the optical undulator under the same undulator strength and beam quality. In order to fill the high-power THz gap and realize the THz undulator, two superimposed laser pulses at normal incidence to the electron-beam moving direction form an equivalent high-field THz undulator by the frequency difference to realize the high-gain X-ray Free electron laser. The pulse front tilt of lateral fed lasers is used to realize the electron-laser synchronic interaction. By PIC simulation, a higher gain and a larger X-ray radiation power by the beat wave THz undulator could be realized, compared with the optical undulator for the same electron beam parameters.

  13. High-gain free electron lasers as generators of short wavelength coherent radiation

    SciTech Connect

    Kim, K.J.; Pellegrini, C.

    1986-05-01

    The development of coherent radiation in high-gain free electron lasers, either from initial noise or from low-power input radiation, is analyzed in terms of three-dimensional Maxwell-Klimontovich equations. Exponential growth and saturation, transverse radiation profiles, transverse coherence and spectral features are discussed. Two possible systems of high-gain free electron lasers, one based on a storage ring and by-pass, another based on a linac and damping rings, are considered for the generation of 400 A radiation.

  14. Balancing high gain and bandwidth in multilayer organic photodetectors with tailored carrier blocking layers

    NASA Astrophysics Data System (ADS)

    Hammond, William T.; Mudrick, John P.; Xue, Jiangeng

    2014-12-01

    We present detailed studies of the high photocurrent gain behavior in multilayer organic photodiodes containing tailored carrier blocking layers we reported earlier in a Letter [W. T. Hammond and J. Xue, Appl. Phys. Lett. 97, 073302 (2010)], in which a high photocurrent gain of up to 500 was attributed to the accumulation of photogenerated holes at the anode/organic active layer interface and the subsequent drastic increase in secondary electron injection from the anode. Here, we show that both the hole-blocking layer structure and layer thickness strongly influence the magnitude of the photocurrent gain. Temporal studies revealed that the frequency response of such devices is limited by three different processes with lifetimes of 10 ?s, 202 ?s, and 2.72 ms for the removal of confined holes, which limit the 3 dB bandwidth of these devices to 1.4 kHz. Furthermore, the composition in the mixed organic donor-acceptor photoactive layer affects both gain and bandwidth, which is attributed to the varying charge transport characteristics, and the optimal gain-bandwidth product is achieved with approximately 30% donor content. Finally, these devices show a high dynamic range of more than seven orders of magnitude, although the photocurrent shows a sublinear dependence on the incident optical power.

  15. Electro-optic response of some chiral liquid crystals with high spontaneous polarization

    NASA Astrophysics Data System (ADS)

    Dascalu, Constanta; Motoc, Cornelia; Petrescu, Emil; Rosu, Constantin; Koswig, H. D.; Labes, U.

    1998-07-01

    The electrooptical properties of some SSFLC devices with high spontaneous polarization liquid crystals are presented. The switching time was determined as function of electric field strength and a.c. frequency. Using the switching time the rotational viscosity (gamma) $curly phi was determined. The results are explained by considering the spectacular molecular relaxation, known as Goldstone mode. The surface stabilized ferroelectric liquid crystal (SSFLC) devices offer memory (bistable) capability, fast response speed and sharp threshold and have a variety of applications in electronics.

  16. A high cholesterol\\/cholate diet induced fatty liver in spontaneously hypertensive rats

    Microsoft Academic Search

    Kohji Ueno; Harumi Okuyama

    1986-01-01

    A high cholesterol diet was found to induce fatty liver in spontaneously hypertensive rats. Although cholesterol ester and\\u000a triacylglycerol accumulated in large amounts in liver, the increases of these lipids in plasma were relatively small and no\\u000a increase in cholesterol and cholesterol ester was observed in aorta. In rats fed normal diet, plasma cholesterol ester mainly\\u000a consisted of arachidonate species;

  17. A novel 3-stage structure for a low-noise, high-gain and gain-flattened L-band erbium doped fiber amplifier.

    PubMed

    Qiang, Ze-xuan; He, Sai-ling; Zhang, Xu-liang; Shen, Lin-fang

    2004-09-01

    The configuration of the novel three-stage L-band erbium-doped fiber amplifier with very large and flat gain and very low noise figure presented in this paper uses the forward ASE (amplified spontaneous emission) from the first section of the EDF (erbium-doped fiber) and the backward ASE from the third section of the EDF (both serve as the secondary pump sources of energy) to pump the second EDF. To improve the pump efficiency, the power of the pump is split into two parts (with a ratio of e.g. 2:7). The characteristics of this L-band EDFA are studied on the basis of the Giles Model with ASE. PMID:15323009

  18. Application of variable-gain output feedback for high-alpha control

    NASA Technical Reports Server (NTRS)

    Ostroff, Aaron J.

    1990-01-01

    A variable-gain, optimal, discrete, output feedback design approach that is applied to a nonlinear flight regime is described. The flight regime covers a wide angle-of-attack range that includes stall and post stall. The paper includes brief descriptions of the variable-gain formulation, the discrete-control structure and flight equations used to apply the design approach, and the high performance airplane model used in the application. Both linear and nonlinear analysis are shown for a longitudinal four-model design case with angles of attack of 5, 15, 35, and 60 deg. Linear and nonlinear simulations are compared for a single-point longitudinal design at 60 deg angle of attack. Nonlinear simulations for the four-model, multi-mode, variable-gain design include a longitudinal pitch-up and pitch-down maneuver and high angle-of-attack regulation during a lateral maneuver.

  19. Resolved discrepancies between visible spontaneous Raman cross-section and direct near-infrared Raman gain measurements in TeO2-based glasses.

    PubMed

    Rivero, Clara; Stegeman, Robert; Couzi, Michel; Talaga, David; Cardinal, Thierry; Richardson, Kathleen; Stegeman, George

    2005-06-13

    Disagreements on the Raman gain response of different tellurite-based glasses, measured at different wavelengths, have been recently reported in the literature. In order to resolve this controversy, a multi-wavelength Raman cross-section experiment was conducted on two different TeO2-based glass samples. The estimated Raman gain response of the material shows good agreement with the directly-measured Raman gain data at 1064 nm, after correction for the dispersion and wavelength-dependence of the Raman gain process. PMID:19495394

  20. Presynaptic NMDA receptors act as local high-gain glutamate detector in developing cerebellar molecular layer interneurons.

    PubMed

    Rossi, Bénédicte; Collin, Thibault

    2013-07-01

    In the classical view, NMDA receptors (NMDARs) are located postsynaptically and play a pivotal role in excitatory transmission and synaptic plasticity. In developing cerebellar molecular layer interneurons (MLIs) however, NMDARs are known to be solely extra- or presynaptic and somewhat poorly expressed. Somatodendritic NMDARs are exclusively activated by glutamate spillover from adjacent synapses, but the mode of activation of axonal NMDARs remains unclear. Our data suggest that a volume transmission is likely to stimulate presynaptic NMDARs (preNMDARs) since NMDA puffs directed to the axon led to inward currents and Ca²? transients restricted to axonal varicosities. Using local glutamate photoliberation, we show that pre- and post-synaptic NMDARs share the same voltage dependence indicating their containing NR2A/B subunits. Ca²? transients elicited by NMDA puffs are eventually followed by delayed events reminding of the spontaneous Ca²? transients (ScaTs) described at the basket cell/Purkinje cell terminals. Moreover, the presence of Ca²? transients at varicosities located more than 5 ?m away from the uncaging site indicates that the activation of preNMDARs sensitizes the Ca²? stores in adjacent varicosities, a process that is abolished in the presence of a high concentration of ryanodine. Altogether, the data demonstrate that preNMDARs act as high-gain glutamate detectors. PMID:23607752

  1. Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

    SciTech Connect

    Baca, A.G.; Brown, D.J.; Donaldson, R.D.; Helgeson, W.D.; Hjalmarson, H.P.; Loubriel, G.M.; Mar, A.; O'Malley, M.W.; Thornton, R.L.; Zutavern, F.J.

    1999-08-05

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 50 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer beneath the PCSS contacts which is very effective in the suppression of filament formation and alleviating current crowding to improve the longevity of PCSS. Virtually indefinite, damage-free operation is now possible at much higher current levels than before. The inherent damage-free current capacity of the switch depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approximately}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.

  2. Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

    SciTech Connect

    MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES; HJALMARSON,HAROLD P.; BACA,ALBERT G.; THORNTON,R.L.; DONALDSON,R.D.

    1999-12-17

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer that is very effective in the suppression of filament formation, alleviating current crowding. Damage-free operation is now possible with virtually infinite expected lifetime at much higher current levels than before. The inherent damage-free current capacity of the bulk GaAs itself depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approx}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs, unlike a switch with conventional contacts. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.

  3. Plasmonic Amplification with Ultra-High Optical Gain at Room Temperature

    E-print Network

    Wang, Wei Hua

    Plasmonic Amplification with Ultra-High Optical Gain at Room Temperature Ning Liu1 , Hong Wei1, ohmic losses are inherent to all plasmonic devices so that further development of integrated plasmonics we show that CdSe nanobelt/Al2O3/Ag hybrid plasmonic waveguides allow for efficient broadband loss

  4. Dynamical robust backstepping using a combined sliding modes and high-gain observer approach

    Microsoft Academic Search

    J. J. Gorman; K. W. Jablokow; David J. Cannon

    2003-01-01

    The design of a controller and high-gain observer methodology which aims to simplify the backstepping procedure is presented. This approach differs from standard backstepping in that the virtual control inputs are designed based on estimates of the previous virtual control inputs. This eliminates the need to take derivatives of the system dynamics, which simplifies the control law and reduces the

  5. ONT High Gain Initiative WRAP (Wide Area Rapid Acoustic Prediction) computational performance section

    Microsoft Academic Search

    J. R. McGraw; G. Hedstrom; T. De Groot

    1990-01-01

    LLNL received a contract during March 1990 to perform three tasks for ONT. This letter report covers Task I which concerned a supercomputing effort in a program termed the High Gain Initiative, which is an anti-submarine (ASW) project that requires substantial computational and signal processing expertise. The core of the computational aspects at the present time is a code called

  6. Longevity of optically activated, high gain GaAs photoconductive semiconductor switches

    Microsoft Academic Search

    Guillermo M. Loubriel; Fred J. Zutavern; Alan Mar; Harold P. Hjalmarson; Albert G. Baca; W. D. Helgeson; R. A. Falk; D. J. Brown

    1998-01-01

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSSs) has been extended to well over ten million pulses by reducing the density of carriers at the semiconductor to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The latter was achieved by varying the spatial distribution of the trigger light thereby widening the

  7. Longevity of optically activated, high gain GaAs photoconductive semiconductor switches

    Microsoft Academic Search

    G. M. Loubriel; F. J. Zutavern; A. Mar; M. W. O'Malley; W. D. Helgeson; D. J. Brown; H. P. Hjalmarson; A. G. Baca

    1997-01-01

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) for pulsed power applications has been extended to well over 10 million pulses by reducing the density of carriers at the semiconductor to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The first was achieved by varying the spatial distribution of the trigger

  8. An ultra-low voltage high gain operational transconductance amplifier for biomedical

    E-print Network

    Paris-Sud XI, Université de

    An ultra-low voltage high gain operational transconductance amplifier for biomedical applications@lpsc.in2p3.fr Abstract--A novel differential-input single-output Operational Transconductance Amplifier cascoded amplifier, and an output stage based on a current source amplifier and a bulk-driven current

  9. High-gain weakly nonlinear flux-modulated Josephson parametric amplifier using a SQUID-array

    E-print Network

    Boyer, Edmond

    High-gain weakly nonlinear flux-modulated Josephson parametric amplifier using a SQUID-array X devices (SQUIDs). This amplifier is parametrically pumped by modulating the flux threading the SQUIDs be obtained with a single SQUID of the same inductance, due to the smaller nonlinearity of the SQUID array. 1

  10. High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis , L. Dugard3

    E-print Network

    Paris-Sud XI, Université de

    High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis H. Ouadi1 , F. Giri2 , L in induction motors is considered in this paper. In most previous works, motor observers have been designed using standard models, neglecting the saturation and hysteretic effects in the machine magnetic circuit

  11. Analytical treatment of the high-gain free electron laser equation

    Microsoft Academic Search

    G. Dattoli; S. Lorenzutta; G. Maino; A. Torre

    1996-01-01

    Exact solutions are obtained for the monodimensional and higher dimensional Free Electron Laser high-gain equations. These equations, which belong to the class of integrodifferential Volterra equations are treated within the context of a perturbative approach, yielding suitable closed-form expressions for the relevant solutions. The proposed method allows to obtain a unified analytical formalism for the full FEL dynamics. Numerical results

  12. Radially resolved simulation of a high-gain free electron laser amplifier

    SciTech Connect

    Fawley, W.M.; Prosnitz, D.; Doss, S.; Gelinas, R.

    1983-06-27

    The results of a two-dimensional simulation of a high-gain free electron laser (FEL) amplifier is presented. The simulation solves the inhomogeneous paraxial wave equation. The source term is radially resolved and is obtained by tracking the interaction of the laser field with localized macroparticles.

  13. Optical properties of the output of a high gain, self-amplified free-electron laser.

    SciTech Connect

    Krinsky, S.; Lewellen , J.; Sajaev, V.; Accelerator Systems Division (APS); BNL

    2004-01-01

    The temporal structure and phase evolutions of a high-gain, self-amplified free-electron laser are measured, including single-shot analysis and statistics over many shots. Excellent agreement with the theory of free-electron laser and photon statistics is found.

  14. High lick rate is maintained throughout spontaneous liquid meals in freely feeding rats.

    PubMed

    Rushing, P A; Houpt, T A; Henderson, R P; Gibbs, J

    1997-11-01

    To investigate the microstructure of spontaneous meals in freely feeding rats, 16 adult male Sprague Dawley rats were housed individually in custom-designed lickometer cages and maintained on a milk diet. Licks were recorded over 23 h at millisecond accuracy via a computer-controlled lickometer. Analysis of lick data revealed an average of about 12 discrete meals/day occurring mainly during the dark phase. The most striking feature of both dark and light meals was the maintenance of a high initial rate of licking until an abrupt decline at the end of the meal. This pattern of licking is very different from the exponential decay of lick rate reported in scheduled test meals of palatable solutions. Thus, the microstructure of licking for meals is affected in an apparently fundamental way by whether a meal is scheduled or spontaneous, suggesting a basic difference in the underlying physiologic controls. PMID:9333217

  15. High-precision gas gain and energy transfer measurements in Ar-CO2 mixtures

    NASA Astrophysics Data System (ADS)

    ?ahin, Özkan; Kowalski, Tadeusz Z.; Veenhof, Rob

    2014-12-01

    Ar-CO2 is a Penning mixture since a fraction of the energy stored in Ar 3p5 3 d and higher excited states can be transferred to ionize CO2 molecules. In the present work, concentration and pressure dependence of Penning transfer rate and photon feedback parameter in Ar-CO2 mixtures have been investigated with recent systematic high-precision gas gain measurements which cover the range 1-50% CO2 at 400, 800, 1200, 1800 hPa and gas gain from 1 to 5×105.

  16. High-gain cascode MMICs in coplanar technology at W-band frequencies

    Microsoft Academic Search

    Axel Tessmann; William H. Haydl; A. Hulsmann; M. Schlechtweg

    1998-01-01

    Compact high-gain W-band multistage amplifier MMICs have been developed in coplanar technology using 0.15 ?m AlGaAs-InGaAs-GaAs PM-HEMTs. The conventional dual-gate HEMT has been modified to include an additional interstage network between the common-source and the common-gate HEMT. The effect of stabilizing circuit elements has been investigated. A gain of 10 dB per cascode stage is obtained at 94 GHz. Multistage

  17. High-gain optical waveguide amplifier based on proton beam writing of Nd:YAG crystal.

    PubMed

    Tan, Yang; Shang, Zhen; Vanga, Sudheer Kumar; Bettiol, Andrew A; Chen, Feng

    2015-06-01

    We report on an optical amplifier based on a Nd:YAG channel waveguide, which was fabricated by proton beam writing. Under the pumping of a continuous wave laser, the high-gain optical amplifications at single wavelength of 1064 nm and wavelength band of 1300 nm -1360 nm were obtained. The maximum gain was 24 dB/cm at 1064 nm and 6 dB/cm at 1319 nm, respectively. This work paves a way to apply proton beam written Nd:YAG waveguides as integrated optical amplifiers for the efficient amplification. PMID:26072821

  18. A high gain array antenna for WLAN-WiMAX applications

    Microsoft Academic Search

    Mei-jing Song; Jiu-sheng Li

    2011-01-01

    A high gain array antenna with 8×4 arrays applied for WLAN\\/WiMAX applications is presented. The proposed antenna is designed for the frequency band 5.07?5.94GHz with the return loss less than ?15dB and the VSWR<1.43. The largest gain of the proposed antenna achieves about 22.78dBi at 5.5GHz and the HBPW is 12.04° at E-plane. The antenna size is 285mm× 133mm. Measured

  19. Long wavelength, high gain InAsSb strained-layer superlattice photoconductive detectors

    DOEpatents

    Biefeld, Robert M. (Albuquerque, NM); Dawson, L. Ralph (Albuquerque, NM); Fritz, Ian J. (Albuquerque, NM); Kurtz, Steven R. (Albuquerque, NM); Zipperian, Thomas E. (Albuquerque, NM)

    1991-01-01

    A high gain photoconductive device for 8 to 12 .mu.m wavelength radiation including an active semiconductor region extending from a substrate to an exposed face, the region comprising a strained-layer superlattice of alternating layers of two different InAs.sub.1-x Sb.sub.x compounds having x>0.75. A pair of spaced electrodes are provided on the exposed face, and changes in 8 to 12 .mu.m radiation on the exposed face cause a large photoconductive gain between the spaced electrodes.

  20. High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host

    DOEpatents

    Comaskey, Brian J. (Walnut Creek, CA); Ault, Earl R. (Livermore, CA); Kuklo, Thomas C. (Oakdale, CA)

    2005-07-05

    A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

  1. Femtosecond Ti:sapphire cryogenic amplifier with high gain and MHz repetition rate.

    PubMed

    Dantan, Aurélien; Laurat, Julien; Ourjoumtsev, Alexei; Tualle-Brouri, Rosa; Grangier, Philippe

    2007-07-01

    We demonstrate high gain amplification of 160-femtosecond pulses in a compact double-pass cryogenic Ti:sapphire amplifier. The setup involves a negative GVD mirrors recompression stage, and operates with a repetition rate between 0.2 and 4 MHz with a continuous pump laser. Amplification factors as high as 17 and 320 nJ Fourier-limited pulses are obtained at a 800 kHz repetition rate. PMID:19547224

  2. Parameter analysis for a high-gain harmonic generation FEL using a recently developed 3D polychromatic code.

    SciTech Connect

    Biedron, S. G.; Freund, H. P.; Yu, L.-H.

    1999-09-10

    One possible design for a fourth-generation light source is the high-gain harmonic generation (HGHG) free-electron laser (FEL). Here, a coherent seed with a wavelength at a subharmonic of the desired output radiation interacts with the electron beam in an energy-modulating section. This energy modulation is then converted into spatial bunching while traversing a dispersive section (a three-dipole chicane). The final step is passage through a radiative section, an undulator tuned to the desired higher harmonic output wavelength. The coherent seed serves to remove noise and can be at a much lower subharmonic of the output radiation, thus eliminating the concerns found in self-amplified spontaneous emission (SASE) and seeded FELs, respectively. Recently, a 3D code that includes multiple frequencies, multiple undulatory (both in quantity and/or type), quadruple magnets, and dipole magnets was developed to easily simulate HGHG. Here, a brief review of the HGHG theory, the code development, the Accelerator Test Facility's (ATF) HGHG FEL experimental parameters, and the parameter analysis from simulations of this specific experiment will be discussed.

  3. DFIG-Based Wind Turbine Robust Control Using High-Order Sliding Modes and a High Gain Observer

    E-print Network

    Brest, Université de

    DFIG-Based Wind Turbine Robust Control Using High-Order Sliding Modes and a High Gain Observer with the power generation control in variable speed wind turbines. In this context, a control strategy is proposed to ensure power extraction optimization of a DFIG- based wind turbine. The proposed control

  4. Investigations of spontaneous ignition of high-pressure hydrogen release based on detailed chemical kinetics

    NASA Astrophysics Data System (ADS)

    Terashima, Hiroshi; Koshi, Mitsuo; Mogi, Toshio; Dobashi, Ritsu

    2013-11-01

    A numerical simulation of spontaneous ignition of high-pressure release in a length of duct is performed to explore ignition mechanisms. The present study adopts a rectangular duct and focuses on effects of initial diaphragm shape on spontaneous ignitions. The Navier-Stokes equations with a detailed chemical kinetics mechanism are solved in a manner of direct numerical simulation. A conventional numerical approach is used for solving the Navier-Stokes equations, while the chemical source term is integrated by a dynamic multi-timescale method for alleviating the stiffness. Detailed mechanisms of spontaneous ignitions are discussed for various initial diaphragm shapes. For a straight diaphragm shape, the ignition occurs only near the wall region due to the adiabatic wall condition, while, for a largely deformed diaphragm shape, the three ignition events: ignition due to leading shock wave reflection at the wall, hydrogen penetration into shock-heated air near the wall, and deep penetration of hydrogen into shock-heated air behind the leading shock wave, are identified.

  5. Properties of high gain GaAs switches for pulsed power applications

    SciTech Connect

    Zutavern, F.J.; Loubriel, G.M.; Hjalmarson, H.P.; Mar, A.; Helgeson, W.D.; O`Malley, M.W.; Ruebush, M.H. [Sandia National Labs., Albuquerque, NM (United States); Falk, R.A. [OptoMetrix, Inc., Renton, WA (United States)

    1997-09-01

    High gain GaAs photoconductive semiconductor switches (PCSS) are being used in a variety of electrical and optical short pulse applications. The highest power application, which the authors are developing, is a compact, repetitive, short pulse linear induction accelerator. The array of PCSS, which drive the accelerator, will switch 75 kA and 250 kV in 30 ns long pulses at 50 Hz. The accelerator will produce a 700 kV, 7kA electron beam for industrial and military applications. In the low power regime, these switches are being used to switch 400 A and 5 kV to drive laser diode arrays which produce 100 ps optical pulses. These short optical pulses are for military and commercial applications in optical and electrical range sensing, 3D laser radar, and high speed imaging. Both types of these applications demand a better understanding of the switch properties to increase switch lifetime, reduce jitter, optimize optical triggering, and improve overall switch performance. These applications and experiments on the fundamental behavior of high gain GaAs switches will be discussed. Open shutter, infra-red images and time-resolved images of the current filaments, which form during high gain switching, will be presented. Results from optical triggering experiments to produce multiple, diffuse filaments for high current repetitive switching will be described.

  6. High-Tc superconducting quantum interference device recordings of spontaneous brain activity: Towards high-Tc magnetoencephalography

    NASA Astrophysics Data System (ADS)

    Öisjöen, F.; Schneiderman, J. F.; Figueras, G. A.; Chukharkin, M. L.; Kalabukhov, A.; Hedström, A.; Elam, M.; Winkler, D.

    2012-03-01

    We have performed single- and two-channel high transition temperature (high-Tc) superconducting quantum interference device (SQUID) magnetoencephalography (MEG) recordings of spontaneous brain activity in two healthy human subjects. We demonstrate modulation of two well-known brain rhythms: the occipital alpha rhythm and the mu rhythm found in the motor cortex. We further show that despite higher noise-levels compared to their low-Tc counterparts, high-Tc SQUIDs can be used to detect and record physiologically relevant brain rhythms with comparable signal-to-noise ratios. These results indicate the utility of high-Tc technology in MEG recordings of a broader range of brain activity.

  7. High-efficiency high-gain monolithic heterostructure FET amplifier at 31 GHz

    NASA Technical Reports Server (NTRS)

    Tserng, H. Q.; Saunier, P.; Kao, Y.-C.

    1993-01-01

    A three-stage heterostructure FET monolithic amplifier has achieved a power-added efficiency of 36 percent with 200 mW output and 18 dB gain at 31 GHz. At a higher drain voltage, the output power increases to 280 mW (with 17.5 dB gain and 31 percent PAE) at a power density of 0.7 W/mm. The MMIC chip measures 2.63 x 1.35 sq mm and requires only a single drain bias and a single gate bias.

  8. Ultraviolet Femtosecond Pulse Amplification with High Gain Using Solid-State, Broad-Band Gain Medium Ce3+:LiCaAlF6

    NASA Astrophysics Data System (ADS)

    Liu, Zhenlin; Kozeki, Toshimasa; Suzuki, Yuji; Sarukura, Nobuhiko; Shimamura, Kiyoshi; Fukuda, Tsuguo; Hirano, Masahiro; Hosono, Hideo

    2001-04-01

    Femtosecond pulse amplification with high gain in the ultraviolet region has been demonstrated using the solid-state, broad-band crystal Ce3+:LiCaAlF6. With the seed pulses coming from the third harmonic generation of a cw mode-locked Ti:sapphire laser, the confocal, four-pass amplifier pumped by 15-mJ, 266-nm, 10-ns pulses from a Q-switched Nd:YAG laser demonstrates 60-dB gain and delivers 54-?J, 289-nm, 200-fs, 10-Hz pulses. There is almost no satellite pulse even without any special single-pulse selection.

  9. Numerical Simulation on the Spontaneous Ignition of Leaking High Pressure Hydrogen from Terminal Unit

    NASA Astrophysics Data System (ADS)

    Xiaobo, Shen; Jinhua, Sun

    The CFD simulation study was carried out on the spontaneous ignition of high pressure leaking hydrogen from some terminal units. An integrated 2D axisymmetric PDF numerical model was established. The results show that, the strong and weak discontinuous surfaces accompanied by combustion phenomenon are formed leading the local temperature and density rising up sharply. Near the outer-edge of the tube mouth, the vortexes are prone to take shape, which contribute to the mixing of hydrogen and air resulting in intenser and longer time combustion. But the combustion is not sustainable and will die out finally. The simulation catches the detailed jet structure including mach disk and barrel shock.

  10. High-gain backup antenna design for Pioneer Venus Orbiter spacecraft

    NASA Technical Reports Server (NTRS)

    Glaser, J. I.

    1986-01-01

    The development and performance is described of a high-gain antenna designed to serve on the Pioneer Venus Orbiter spacecraft as a backup to the principal high-gain antenna unit in the unlikely event the mechanically despun antenna mechanism malfunctioned. The final design, a center-fed standing wave array of six sleeve dipoles enclosed in a fiber glass radome, performed successfully, as did all the antennas, on the Pioneer Orbiter spacecraft which was launched on May 20, 1978, as part of the Pioneer Venus mission. Photographs of experimental models giving details of design and construction are included, as well as graphs showing measured pattern and impedance matching characteristics of the subject antenna.

  11. Mode control in a high gain relativistic klystron amplifier with 3 GW output power

    NASA Astrophysics Data System (ADS)

    Wu, Yang; Xie, Hong-Quan; Xu, Zhou

    2014-01-01

    Higher mode excitation is very serious in the relativistic klystron amplifier, especially for the high gain relativistic amplifier working at tens of kilo-amperes. The mechanism of higher mode excitation is explored in the PIC simulation and it is shown that insufficient separation of adjacent cavities is the main cause of higher mode excitation. So RF lossy material mounted on the drift tube wall is adopted to suppress higher mode excitation. A high gain S-band relativistic klystron amplifier is designed for the beam current of 13 kA and the voltage of 1 MV. PIC simulation shows that the output power is 3.2 GW when the input power is only 2.8 kW.

  12. Terahertz photonic transmitters with a high-gain open-ended rampart slot array antenna

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Ru; Chen, Hung-Pin; Chiu, Pei-Chin; Chyi, Jen-Inn; Wang, Bing-Hsiao; Chen, Shih-Yuan; Sun, Chi-Kuang

    2010-02-01

    We propose to integrate a high-gain open-ended rampart slot array antenna in our edge-coupled terahertz (THz) photonic transmitters. By locating the open circuits at the end of each quarter-wavelength slot antenna, the reflected terahertz wave can constructively interference with the input wave and hence produce higher gain. In addition, the folded feeding networks turn more propagating waves into the effective radiating segments rather than the dispersive surface waves. A THz resonant cavity is also designed under our monolithic THz-wave circuits. A 300-nm gold layer is coated below the substrate to serve as a reflecting mirror to reflect back the THz waves to the antenna. The resonant cavity design not only provides a robust base for post device process but also greatly enhances the gain of antenna. With the design of openended rampart slot array antenna and THz resonant cavity, we demonstrate that the gain of antenna can reach 8~9 dBi.

  13. AlxGa1-xN-based avalanche photodiodes with high reproducible avalanche gain

    E-print Network

    Ozbay, Ekmel

    to be lower than 8 fA for bias voltages up to 20 V. The responsivity of the photodetectors is 0.13 A/W at 272-blind photodetectors with reproducible avalanche gain as high as 1560 under ultraviolet illumination. The solar-blind photodetectors have a sharp cutoff around 276 nm. The dark currents of the 40 m diameter devices are measured

  14. High-gain dual-WLAN-band dual-loop antennas for MIMO access-points

    Microsoft Academic Search

    Saou-Wen Su; Fa-Shian Chang

    2010-01-01

    A high-gain, three-antenna system suitable to be concealed inside wireless access points for multiple-input multiple-output (MIMO) applications in the WLAN 2.4\\/5.2\\/5.8 GHz bands is presented. The MIMO antenna system is composed of three dual-loop antennas occupying a moderate size of 10 × 20 × 40 mm3. Each dual-loop antenna further comprises a large outer loop and a small inner loop,

  15. Design of a High Gain Low Sidelobe Microstrip Antenna Array at Ku-band

    Microsoft Academic Search

    Hongqi Xiang; Xing Jiang; Simin Li

    2009-01-01

    Aperture coupling feed and double-layer microstrip patch structure are applied to design microstrip antenna element and subarrays of microstrip antenna array with high gain low sidelobe and backlobe at Ku-band. Parallel feed and T-junction type power divider are used to design low sidelobe array by the principle of Dolph-Chebeshev distribution. The simulate results show that the relative bandwidth of the

  16. First ultraviolet high-gain harmonic-generation free-electron laser.

    PubMed

    Yu, L H; DiMauro, L; Doyuran, A; Graves, W S; Johnson, E D; Heese, R; Krinsky, S; Loos, H; Murphy, J B; Rakowsky, G; Rose, J; Shaftan, T; Sheehy, B; Skaritka, J; Wang, X J; Wu, Z

    2003-08-15

    We report the first experimental results on a high-gain harmonic-generation (HGHG) free-electron laser (FEL) operating in the ultraviolet. An 800 nm seed from a Ti:sapphire laser has been used to produce saturated amplified radiation at the 266 nm third harmonic. The results confirm the predictions for HGHG FEL operation: stable central wavelength, narrow bandwidth, and small pulse-energy fluctuation. PMID:12935021

  17. A CMOS-MEMS Gyroscope Interface Circuit Design With High Gain and Low Temperature Dependence

    Microsoft Academic Search

    Hongzhi Sun; Kemiao Jia; Xuesong Liu; Guizhen Yan; Yu-Wen Hsu; Robert M. Fox; Huikai Xie

    2011-01-01

    This paper describes an interface circuit design for monolithic CMOS-MEMS gyroscopes, based on a novel differen- tial difference amplifier (DDA) with high gain, low temperature and process dependence, low noise, and low power consumption. The DDA achieves a 4 fF equivalent transcapacitance with a 0.01 temperature variation. The DDA-based interface circuit has been integrated with a -axis gyroscope on a

  18. Interval mapping of high growth (hg), a major locus that increases weight gain in mice

    Microsoft Academic Search

    Simon Horvat; Juan F. Medrano

    1995-01-01

    The high growth locus (hg) causes a major increase in weight gain and body size in mice. As a first step to map-based cloning of hg, we developed a genetic map of the hg-containing region using interval mapping of 403 Fâ from a C57BL\\/6J-hghg x CAST\\/EiJ cross. The maximum likelihood position of hg was at the chromosome 10 marker D10Mit41

  19. First Ultraviolet High-Gain Harmonic-Generation Free-Electron Laser

    Microsoft Academic Search

    L. H. Yu; L. Dimauro; A. Doyuran; W. S. Graves; E. D. Johnson; R. Heese; S. Krinsky; H. Loos; J. B. Murphy; G. Rakowsky; J. Rose; T. Shaftan; B. Sheehy; J. Skaritka; X. J. Wang; Z. Wu

    2003-01-01

    We report the first experimental results on a high-gain harmonic-generation (HGHG) free-electron laser (FEL) operating in the ultraviolet. An 800nm seed from a Ti:sapphire laser has been used to produce saturated amplified radiation at the 266nm third harmonic. The results confirm the predictions for HGHG FEL operation: stable central wavelength, narrow bandwidth, and small pulse-energy fluctuation.

  20. Optimization of single-step tapering amplitude and energy detuning for high-gain FELs

    NASA Astrophysics Data System (ADS)

    Li, He-Ting; Jia, Qi-Ka

    2015-01-01

    We put forward a method to optimize the single-step tapering amplitude of undulator strength and initial energy tuning of electron beam to maximize the saturation power of high gain free-electron lasers (FELs), based on the physics of longitudinal electron beam phase space. Using the FEL simulation code GENESIS, we numerically demonstrate the accuracy of the estimations for parameters corresponding to the linac coherent light source and the Tesla test facility.

  1. Broadband discrete fiber Raman amplifier with high differential gain operating over 1.65 ?m-band

    Microsoft Academic Search

    T. Tsuzaki; M. Kakui; M. Hirano; M. Onishi; Y. Nakai; M. Nishimura

    2001-01-01

    A high differential-gain (0.08 dB\\/mW), low-noise (<5.0 dB), broadband (30 nm) and flat-gain (<±1 dB) fiber Raman amplifier operating over the 1.65 ?m-band has been demonstrated employing a low-loss highly nonlinear fiber and a broadened pump light source.

  2. Highly accurate measurements of the spontaneous fission half-life of 240,242Pu

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, P.; Bry?, T.; Eykens, R.; Hambsch, F.-J.; Moens, A.; Oberstedt, S.; Sibbens, G.; Vanleeuw, D.; Vidali, M.; Pretel, C.

    2013-12-01

    Fast spectrum neutron-induced fission cross-section data for transuranic isotopes are of special demand from the nuclear data community. In particular highly accurate data are needed for the new generation IV nuclear applications. The aim is to obtain precise neutron-induced fission cross sections for 240Pu and 242Pu. To do so, accurate data on spontaneous fission half-lives must be available. Also, minimizing uncertainties in the detector efficiency is a key point. We studied both isotopes by means of a twin Frisch-grid ionization chamber with the goal of improving the present data on the neutron-induced fission cross section. For the two plutonium isotopes the high ?-particle decay rates pose a particular problem to experiments due to piling-up events in the counting gas. Argon methane and methane were employed as counting gases, the latter showed considerable improvement in signal generation due to its higher drift velocity. The detection efficiency for both samples was determined, and improved spontaneous fission half-lives were obtained with very low statistical uncertainty (0.13% for 240Pu and 0.04% for 242Pu): for 240Pu, T1/2,SF=1.165×1011 yr (1.1%), and for 242Pu, T1/2,SF=6.74×1010 yr (1.3%). Systematic uncertainties are due to sample mass (0.4% for 240Pu and 0.9% for 242Pu) and efficiency (1%).

  3. Interpolating gain-scheduled H? loop shaping design for high speed ball screw feed drives.

    PubMed

    Dong, Liang; Tang, WenCheng; Bao, DaFei

    2015-03-01

    This paper presents a method to design servo controllers for flexible ball screw drives with time-varying dynamics, which are mainly due to the time-varying table position and the workpiece mass. A gain-scheduled H? loop shaping controller is designed to achieve high tracking performance against the dynamic variations. H? loop shaping design procedure incorporates open loop shaping by a set of compensators to obtain performance/robust stability tradeoffs. The interpolating gain-scheduled controller is obtained by interpolating the state space model of the linear time-invariant (LTI) controllers estimated for fixed values of the scheduling parameters and a linear least squares problem can be solved. The proposed controller has been compared with P/PI with velocity and acceleration feedforward and adaptive backstepping sliding mode control experimentally. The experimental results indicate that the tracking performance has been improved and the robustness for time-varying dynamics has been achieved with the proposed scheme. PMID:25592980

  4. A bootstrapped, low-noise, and high-gain photodetector for shot noise measurement

    SciTech Connect

    Zhou, Haijun; Yang, Wenhai; Li, Zhixiu; Li, Xuefeng; Zheng, Yaohui, E-mail: yhzheng@sxu.edu.cn [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China)] [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China)

    2014-01-15

    We presented a low-noise, high-gain photodetector based on the bootstrap structure and the L-C (inductance and capacitance) combination. Electronic characteristics of the photodetector, including electronic noise, gain and frequency response, and dynamic range, were verified through a single-frequency Nd:YVO{sub 4} laser at 1064 nm with coherent output. The measured shot noise of 50 ?W laser was 13 dB above the electronic noise at the analysis frequency of 2 MHz, and 10 dB at 3 MHz. And a maximum clearance of 28 dB at 2 MHz was achieved when 1.52 mW laser was illuminated. In addition, the photodetector showed excellent linearities for both DC and AC amplifications in the laser power range between 12.5 ?W and 1.52 mW.

  5. High-gain dc SQUID magnetometers with NbN nanobridges

    SciTech Connect

    Irie, A.; Hamasaki, K.; Yamashita, T. (Dept. of Electronics, Nagaoka Univ. of Technology, Kamitomioka-Machi 1603-1, Nagoka-shi, Niigata 940-21 (JP)); Matsui, T.; Komiyama, B. (Communication Research Lab., Ministry of Posts and Telecommunication, Koganei, Tokyo 184 (JP))

    1991-03-01

    This paper reports on high-gain dc SQUIDs using NbN nanobridges fabricated for magnetometers with high sensitivity, and their device parameters and intrinsic energy sensitivity have been evaluated. The slit inductance of the square washer SQUID was reduced by using the co-planar edge structure of the low inductance. The junction capacitance was typically 15 {approximately} 40 ft. The maximum voltage modualtion was about 110 {mu}V for the NbN nanobridge SQUID with an inductance of 0.18nH.

  6. Highly stable phospholipid unilamellar vesicles from spontaneous vesiculation: A DLS and SANS study.

    PubMed

    Yue, Baohua; Huang, Chien-Yueh; Nieh, Mu-Ping; Glinka, Charles J; Katsaras, John

    2005-01-13

    Spontaneously formed unilamellar vesicles (ULV) composed of short- and long-chain phospholipids, dihexanoyl phosphorylcholine (DHPC) and dimyristoyl phosphorylcholine (DMPC), respectively, were doped with a negatively charged lipid, dimyristoyl phosphorylglycerol (DMPG), and studied with small-angle neutron scattering (SANS) and dynamic light scattering (DLS). Upon dilution, the spontaneous formation of vesicles was found to take place from bilayered micelles, or so-called "bicelles". SANS and DLS data show that ULV with narrow size distributions are highly stable at low lipid (C(lp) < 0.50 wt %) and NaCl salt (C(s)) concentrations. ULV size was found to be independent of both C(lp) and C(s) when they were below 0.33 and 0.5 wt %, respectively. Surface charge and salinity were found to be important factors in preparing ULV of a certain size. This observation is not in complete agreement with previous experimental results and cannot be completely explained with current theoretical predictions based on equilibrium calculations for catanionic surfactant mixtures. ULV size is found to be invariant over a wide range of temperatures, both below and above the phase-transition temperature, T(M), of DMPC, and was stable for periods of weeks and months, even after sonication. PMID:16851053

  7. Redesign of a Variable-Gain Output Feedback Longitudinal Controller Flown on the High-Alpha Research Vehicle (HARV)

    NASA Technical Reports Server (NTRS)

    Ostroff, Aaron J.

    1998-01-01

    This paper describes a redesigned longitudinal controller that flew on the High-Alpha Research Vehicle (HARV) during calendar years (CY) 1995 and 1996. Linear models are developed for both the modified controller and a baseline controller that was flown in CY 1994. The modified controller was developed with three gain sets for flight evaluation, and several linear analysis results are shown comparing the gain sets. A Neal-Smith flying qualities analysis shows that performance for the low- and medium-gain sets is near the level 1 boundary, depending upon the bandwidth assumed, whereas the high-gain set indicates a sensitivity problem. A newly developed high-alpha Bode envelope criterion indicates that the control system gains may be slightly high, even for the low-gain set. A large motion-base simulator in the United Kingdom was used to evaluate the various controllers. Desired performance, which appeared to be satisfactory for flight, was generally met with both the low- and medium-gain sets. Both the high-gain set and the baseline controller were very sensitive, and it was easy to generate pilot-induced oscillation (PIO) in some of the target-tracking maneuvers. Flight target-tracking results varied from level 1 to level 3 and from no sensitivity to PIO. These results were related to pilot technique and whether actuator rate saturation was encountered.

  8. Whey protein reduces early life weight gain in mice fed a high-fat diet.

    PubMed

    Tranberg, Britt; Hellgren, Lars I; Lykkesfeldt, Jens; Sejrsen, Kristen; Jeamet, Aymeric; Rune, Ida; Ellekilde, Merete; Nielsen, Dennis S; Hansen, Axel Kornerup

    2013-01-01

    An increasing number of studies indicate that dairy products, including whey protein, alleviate several disorders of the metabolic syndrome. Here, we investigated the effects of whey protein isolate (whey) in mice fed a high-fat diet hypothesising that the metabolic effects of whey would be associated with changes in the gut microbiota composition. Five-week-old male C57BL/6 mice were fed a high-fat diet ad libitum for 14 weeks with the protein source being either whey or casein. Faeces were collected at week 0, 7, and 13 and the fecal microbiota was analysed by denaturing gradient gel electrophoresis analyses of PCR-derived 16S rRNA gene (V3-region) amplicons. At the end of the study, plasma samples were collected and assayed for glucose, insulin and lipids. Whey significantly reduced body weight gain during the first four weeks of the study compared with casein (P<0.001-0.05). Hereafter weight gain was similar resulting in a 15% lower final body weight in the whey group relative to casein (34.0±1.0 g vs. 40.2±1.3 g, P<0.001). Food intake was unaffected by protein source throughout the study period. Fasting insulin was lower in the whey group (P<0.01) and glucose clearance was improved after an oral glucose challenge (P<0.05). Plasma cholesterol was lowered by whey compared to casein (P<0.001). The composition of the fecal microbiota differed between high- and low-fat groups at 13 weeks (P<0.05) whereas no difference was seen between whey and casein. In conclusion, whey initially reduced weight gain in young C57BL/6 mice fed a high-fat diet compared to casein. Although the effect on weight gain ceased, whey alleviated glucose intolerance, improved insulin sensitivity and reduced plasma cholesterol. These findings could not be explained by changes in food intake or gut microbiota composition. Further studies are needed to clarify the mechanisms behind the metabolic effects of whey. PMID:23940754

  9. Whey Protein Reduces Early Life Weight Gain in Mice Fed a High-Fat Diet

    PubMed Central

    Tranberg, Britt; Hellgren, Lars I.; Lykkesfeldt, Jens; Sejrsen, Kristen; Jeamet, Aymeric; Rune, Ida; Ellekilde, Merete; Nielsen, Dennis S.; Hansen, Axel Kornerup

    2013-01-01

    An increasing number of studies indicate that dairy products, including whey protein, alleviate several disorders of the metabolic syndrome. Here, we investigated the effects of whey protein isolate (whey) in mice fed a high-fat diet hypothesising that the metabolic effects of whey would be associated with changes in the gut microbiota composition. Five-week-old male C57BL/6 mice were fed a high-fat diet ad libitum for 14 weeks with the protein source being either whey or casein. Faeces were collected at week 0, 7, and 13 and the fecal microbiota was analysed by denaturing gradient gel electrophoresis analyses of PCR-derived 16S rRNA gene (V3-region) amplicons. At the end of the study, plasma samples were collected and assayed for glucose, insulin and lipids. Whey significantly reduced body weight gain during the first four weeks of the study compared with casein (P<0.001–0.05). Hereafter weight gain was similar resulting in a 15% lower final body weight in the whey group relative to casein (34.0±1.0 g vs. 40.2±1.3 g, P<0.001). Food intake was unaffected by protein source throughout the study period. Fasting insulin was lower in the whey group (P<0.01) and glucose clearance was improved after an oral glucose challenge (P<0.05). Plasma cholesterol was lowered by whey compared to casein (P<0.001). The composition of the fecal microbiota differed between high- and low-fat groups at 13 weeks (P<0.05) whereas no difference was seen between whey and casein. In conclusion, whey initially reduced weight gain in young C57BL/6 mice fed a high-fat diet compared to casein. Although the effect on weight gain ceased, whey alleviated glucose intolerance, improved insulin sensitivity and reduced plasma cholesterol. These findings could not be explained by changes in food intake or gut microbiota composition. Further studies are needed to clarify the mechanisms behind the metabolic effects of whey. PMID:23940754

  10. ONT High Gain Initiative WRAP (Wide Area Rapid Acoustic Prediction) computational performance section

    SciTech Connect

    McGraw, J.R.; Hedstrom, G.; De Groot, T.

    1990-10-02

    LLNL received a contract during March 1990 to perform three tasks for ONT. This letter report covers Task I which concerned a supercomputing effort in a program termed the High Gain Initiative, which is an anti-submarine (ASW) project that requires substantial computational and signal processing expertise. The core of the computational aspects at the present time is a code called WRAP (Wide Area Rapid Acoustic Prediction). LLNL's objective was to study the WRAP model and determine the feasibility and limits of its optimization. At the present time, the WRAP code runs on a single processor VAX computer.

  11. High Gain Antenna System Deployment Mechanism Integration, Characterization, and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Parong, Fil; Russell, Blair; Garcen, Walter; Rose, Chris; Johnson, Chris; Huber, Craig

    2014-01-01

    The integration and deployment testing of the High Gain Antenna System for the Global Precipitation Measurement mission is summarized. The HGAS deployment mechanism is described. The gravity negation system configuration and its influence on vertical, ground-based, deployment tests are presented with test data and model predictions. A focus is made on the late discovery and resolution of a potentially mission degrading deployment interference condition. The interaction of the flight deployment mechanism, gravity negation mechanism, and use of dynamic modeling is described and lessons learned presented.

  12. High Gain Antenna System Deployment Mechanism Integration, Characterization, and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Parong, Fil; Russell, Blair; Garcen, Walter; Rose, Chris; Johnson, Chris; Huber, Craig

    2014-01-01

    The integration and deployment testing of the High Gain Antenna System (HGAS) for the Global Precipitation Measurement mission is summarized. The HGAS deployment mechanism is described. The gravity negation system configuration and its influence on vertical, ground-based deployment tests are presented with test data and model predictions. A focus is made on the late discovery and resolution of a potentially mission-degrading deployment interference condition. The interaction of the flight deployment mechanism, gravity-negation mechanism, and use of dynamic modeling is described and lessons learned presented

  13. High gain FEL amplification of charge modulation caused by a hadron

    SciTech Connect

    Litvinenko,V.; Ben-Zvi, I.; Hao, Y.; Kayran, D.; Pozdeyev, E.; Wang, G.; Reiche, S.; Shevchenko, O.; Vinokurov, N. A.

    2008-08-24

    In scheme of coherent electron cooling (CeC) [1,2], a modulation of electron beam density induced by a copropagation hadron is amplified in high gain FEL. The resulting amplified modulation of electron beam, its shape, form and its lethargy determine number of important properties of the coherent electron cooling. In this talk we present both analytical and numerical (using codes RON [3] and Genesis [4]) evaluations of the corresponding Green functions. We also discuss influence of electron beam parameters on the FEL response.

  14. Longevity of optically activated, high gain GaAs photoconductive semiconductor switches

    SciTech Connect

    Loubriel, G.M.; Zutavern, F.J.; Mar, A. [and others

    1997-08-01

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to well over 10 million pulses by reducing the density of carriers at the semiconductor to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The first was achieved by varying the spatial distribution of the trigger light thereby widening the current filaments that are characteristic of the high gain switches. The authors reduced the carrier density in the vertical direction by using ion implantation. These results were obtained for currents of about 10 A, current duration of 3.5 ns, and switched voltage of {approximately}2 kV. At currents of {approximately}70 A, the switches last for 0.6 million pulses. In order to improve the performance at high currents new processes such as deep diffusion and epitaxial growth of contacts are being pursued. To guide this effort the authors measured a carrier density of 6 x 10{sup 18} electrons (or holes)/cm{sup 3} in filaments that carry a current of 5 A.

  15. A large-area VUV photosensor with high gain by means of photoelectron acceleration and concentration

    SciTech Connect

    Lopes, J.A.M.; Conde, C.A.N. [Univ. de Coimbra (Portugal). Dept. de Fisica] [Univ. de Coimbra (Portugal). Dept. de Fisica

    1995-08-01

    Photomultiplier tubes (PMT) are generally used to detect the vacuum ultraviolet (VUV) scintillation light produced in devices like gas proportional scintillation counters (GPSC). Here, the authors report the results of the development of a new photosensor with large area and high gain. The photoelectrons from a 48 mm diameter CsI photocathode are accelerated with high voltage and electrostatically concentrated, rather than imaged, onto the surface of an 8 mm diameter semiconductor detector. The amplitude of the photoelectron signals initiated by a pulsed xenon lamp of constant intensity and high stability (instability <1%) is approximately linear with the accelerating voltage in the 10 to 20 kV region. Non uniformity of the signal amplitude over 70% of the photocathode area is below 6%.

  16. Doped contacts for high-longevity optically activated, high-gain GaAs photoconductive semiconductor switches

    Microsoft Academic Search

    Alan Mar; Guillermo M. Loubriel; Fred J. Zutavern; M. W. O'Malley; W. D. Helgeson; D. J. Brown; H. P. Hjalmarson; A. G. Baca; R. L. Thornton; R. D. Donaldson

    2000-01-01

    The longevity of high-gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer that is very effective in the suppression of filament formation, alleviating current crowding. Damage-free operation is now possible at much higher current levels than before. The inherent damage-free

  17. A Comparative Study of the Spontaneous Social Interactions of Children with High-Functioning Autism and Children with Asperger's Disorder

    ERIC Educational Resources Information Center

    Macintosh, Kathleen; Dissanayake, Cheryl

    2006-01-01

    A comparative observational study was undertaken of the spontaneous social interactions of children with high-functioning autism and Asperger's disorder. The sample comprised 20 children with high-functioning autism, 19 children with Asperger's disorder and 17 typically developing children matched on chronological age and overall mental age. A…

  18. Technology developments and first measurements of Low Gain Avalanche Detectors (LGAD) for high energy physics applications

    NASA Astrophysics Data System (ADS)

    Pellegrini, G.; Fernández-Martínez, P.; Baselga, M.; Fleta, C.; Flores, D.; Greco, V.; Hidalgo, S.; Mandi?, I.; Kramberger, G.; Quirion, D.; Ullan, M.

    2014-11-01

    This paper introduces a new concept of silicon radiation detector with intrinsic multiplication of the charge, called Low Gain Avalanche Detector (LGAD). These new devices are based on the standard Avalanche Photo Diodes (APD) normally used for optical and X-ray detection applications. The main differences to standard APD detectors are the low gain requested to detect high energy charged particles, and the possibility to have fine segmentation pitches: this allows fabrication of microstrip or pixel devices which do not suffer from the limitations normally found [1] in avalanche detectors. In addition, a moderate multiplication value will allow the fabrication of thinner devices with the same output signal of standard thick substrates. The investigation of these detectors provides important indications on the ability of such modified electrode geometry to control and optimize the charge multiplication effect, in order to fully recover the collection efficiency of heavily irradiated silicon detectors, at reasonable bias voltage, compatible with the voltage feed limitation of the CERN High Luminosity Large Hadron Collider (HL-LHC) experiments [2]. For instance, the inner most pixel detector layers of the ATLAS tracker will be exposed to fluences up to 2×1016 1 MeV neq/cm2, while for the inner strip detector region fluences of 1×1015 neq/cm2 are expected. The gain implemented in the non-irradiated devices must retain some effect also after irradiation, with a higher multiplication factor with respect to standard structures, in order to be used in harsh environments such those expected at collider experiments.

  19. Spontaneous pneumothorax

    PubMed Central

    2011-01-01

    Introduction The incidence of spontaneous pneumothorax is 24/100,000 a year in men and 9.9/100,000 a year in women in England and Wales. The major contributing factor is smoking, which increases the likelihood by 22 times in men, and by 8 times in women. While death from spontaneous pneumothorax is rare, rates of recurrence are high, with one study of men in the USA finding a total recurrence rate of 35%. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatments in people presenting with spontaneous pneumothorax? What are the effects of interventions to prevent recurrence in people with previous spontaneous pneumothorax? We searched: Medline, Embase, The Cochrane Library, and other important databases up to January 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 17 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review we present information relating to the effectiveness and safety of the following interventions: chest-tube drainage (alone or plus suction), chest tubes (small, standard sizes, one-way valves), needle aspiration, and pleurodesis. PMID:21477390

  20. Design and performance of high-gain free-electron lasers with grazing incidence, unstable ring resonators

    Microsoft Academic Search

    A. Bhowmik; P. K. Kennedy; S. E. Bitterly; R. H. Labbe

    1988-01-01

    Grazing incidence, ring resonators have been proposed for high-gain free-electron lasers to alleviate the problem of inordinately high irradiance on intracavity optics. Such resonators are also relatively compact, and consequently, their alignment tolerances are more manageable. In this paper, the authors present a geometric design algorithm and detailed computer analysis of a high-gain free-electron ring laser with hyperboloid-paraboloid grazing incidence

  1. Design and performance of high-gain free-electron lasers with grazing incidence, unstable ring resonators

    Microsoft Academic Search

    Anup Bhowmik; Paul K. Kennedy; Steven E. Bitterly; Ross H. Labbe

    1988-01-01

    Grazing incidence, ring resonators have been proposed for high-gain free-electron lasers to alleviate the problem of inordinately high irradiance on intracavity optics. Such resonators are also relatively compact, and consequently, their alignment tolerances are more manageable. A geometric design algorithm and detailed computer analysis of a high-gain free-electron ring laser with hyperboloid-paraboloid grazing incidence telescopes is presented. A 3-D wave

  2. High modal gain in Ga(NAsP)/(BGa)((As)P) heterostructures grown lattice matched on (001) silicon

    NASA Astrophysics Data System (ADS)

    Koukourakis, N.; Funke, D. A.; Gerhardt, N. C.; Hofmann, M. R.; Liebich, S.; Bückers, C.; Zinnkann, S.; Zimprich, M.; Beyer, A.; Chatterjee, S.; Koch, S. W.; Kunert, B.; Volz, K.; Stolz, W.

    2011-02-01

    We present modal gain measurements in Ga(NAsP) heterostructures pseudomorphically grown on silicon substrate. Using the variable stripe length method we analyze the modal gain performance of an unprocessed single quantum well sample for different excitation densities. We obtain high modal gain values up to 55 cm-1 at room temperature. These values are comparable to those of common high quality laser material. This demonstrates the high optical quality of the new dilute nitride material Ga(NAsP) and underlines its candidacy for electrically pumped lasing on silicon substrate.

  3. Inflection point caustic problems and solutions for high-gain dual-shaped reflectors

    NASA Technical Reports Server (NTRS)

    Galindo-Israel, Victor; Veruttipong, Thavath; Imbriale, William; Rengarajan, Sembiam

    1990-01-01

    The singular nature of the uniform geometrical theory of diffraction (UTD) subreflector scattered field at the vicinity of the main reflector edge (for a high-gain antenna design) is investigated. It is shown that the singularity in the UTD edge-diffracted and slope-diffracted fields is due to the reflection distance parameter approaching infinity in the transition functions. While the geometrical optics (GO) and UTD edge-diffracted fields exhibit singularities of the same order, the edge slope-diffracted field singularity is more significant and is substantial for greater subreflector edge tapers. The diffraction analysis of such a subreflector in the vicinity of the main reflector edge has been carried out efficiently and accurately by a stationary phase evaluation of the phi-integral, whereas the theta-integral is carried out numerically. Computational results from UTD and physical optics (PO) analysis of a 34-m ground station dual-shaped reflector confirm the analytical formulations for both circularly symmetric and offset asymmetric subreflectors. It is concluded that the proposed PO(theta)GO(phi) technique can be used to study the spillover or noise temperature characteristics of a high-gain reflector antenna efficiently and accurately.

  4. Anti-HMGB1 antibody reduces weight gain in mice fed a high-fat diet

    PubMed Central

    Montes, V N; Subramanian, S; Goodspeed, L; Wang, S A; Omer, M; Bobik, A; Teshigawara, K; Nishibori, M; Chait, A

    2015-01-01

    Insulin resistance in obesity is believed to be propagated by adipose tissue and liver inflammation. HMGB1 is a multifunctional protein that is pro-inflammatory when released from cells. It has been previously demonstrated that anti-HMGB1 antibody reduces atherosclerotic lesion pro-inflammatory cells and progression of atherosclerosis in a mouse model. To test the potential beneficial role of blocking HMGB1 in adipose tissue and liver inflammation in mice fed an obesogenic diet, we administered anti-HMGB1 antibody to C57Bl/6 mice fed a high (60%)-fat diet. The mice were treated with weekly injections of an anti-HMGB1 antibody or anti-KLH antibody (isotype control) for 16 weeks. Mice that received the anti-HMGB1 antibody gained less weight than the control-treated animals. Anti-HMGB1 treatment also reduced hepatic expression of TNF-alpha and MCP-1, molecules that promote inflammation. However, adipose tissue inflammation, as measured by gene expression analyses and immunohistochemistry, did not differ between the two groups. There also were no differences in glucose or insulin tolerance between the two groups. When feeding mice a high-fat diet, these data suggest that HMGB1 may have a crucial role in weight gain and liver inflammation. PMID:26075638

  5. Anti-HMGB1 antibody reduces weight gain in mice fed a high-fat diet.

    PubMed

    Montes, V N; Subramanian, S; Goodspeed, L; Wang, S A; Omer, M; Bobik, A; Teshigawara, K; Nishibori, M; Chait, A

    2015-01-01

    Insulin resistance in obesity is believed to be propagated by adipose tissue and liver inflammation. HMGB1 is a multifunctional protein that is pro-inflammatory when released from cells. It has been previously demonstrated that anti-HMGB1 antibody reduces atherosclerotic lesion pro-inflammatory cells and progression of atherosclerosis in a mouse model. To test the potential beneficial role of blocking HMGB1 in adipose tissue and liver inflammation in mice fed an obesogenic diet, we administered anti-HMGB1 antibody to C57Bl/6 mice fed a high (60%)-fat diet. The mice were treated with weekly injections of an anti-HMGB1 antibody or anti-KLH antibody (isotype control) for 16 weeks. Mice that received the anti-HMGB1 antibody gained less weight than the control-treated animals. Anti-HMGB1 treatment also reduced hepatic expression of TNF-alpha and MCP-1, molecules that promote inflammation. However, adipose tissue inflammation, as measured by gene expression analyses and immunohistochemistry, did not differ between the two groups. There also were no differences in glucose or insulin tolerance between the two groups. When feeding mice a high-fat diet, these data suggest that HMGB1 may have a crucial role in weight gain and liver inflammation. PMID:26075638

  6. Effects of high count rate and gain shift on isotope identification algorithms

    SciTech Connect

    Robinson, Sean M.; Kiff, Scott D.; Ashbaker, Eric D.; Flumerfelt, Eric L.; Salvitti, Matthew

    2009-11-01

    Spectroscopic gamma-ray detectors are used for many research, industrial, and homeland- security applications. Thallium-doped sodium iodide, (NaI(Tl)), scintillation crystals coupled to photomultiplier tubes provide medium-resolution spectral data about the surrounding environment. NaI(Tl)-based detectors, paired with spectral identification algorithms, are often effective for identifying gamma-ray sources by isotope. However, intrinsic limitations for NaI(Tl) systems exist, including gain shifts and spectral marring (e.g., loss of resolution and count-rate saturation) at high count rates. These effects are hardware dependent and have strong effects on the radioisotopic identification capability of NaI(Tl)-based systems. In this work, the effects of high count rate on the response of isotope-identification algorithms are explored. It is shown that a small gain shift of a few tens of keV is sufficient to disturb identification. The onset of this and other spectral effects is estimated for NaI(Tl) crystals, and a mechanism for mitigating these effects by estimating and correcting for them is implemented and evaluated.

  7. Effects of High Count Rate and Gain Shift on Isotope Identification Algorithms

    SciTech Connect

    Robinson, Sean M.; Kiff, Scott D.; Ashbaker, Eric D.; Bender, Sarah E.; Flumerfelt, Eric L.; Salvitti, Matthew; Borgardt, James D.; Woodring, Mitchell L.

    2007-12-31

    Spectroscopic gamma-ray detectors are used for many research applications, as well as Homeland Security screening applications. Sodium iodide (NaI) scintillator crystals coupled with photomultiplier tubes (PMTs) provide medium-resolution spectral data about the surrounding environment. NaI based detectors, paired with spectral identification algorithms, are often effective in identifying sources of interest by isotope. However, intrinsic limitations exist for NaI systems because of gain shifts and spectral marring (e.g., loss of resolution and count-rate saturation) at high count rates. These effects are hardware dependent, and have strong effects on the radioisotopic identification capability of these systems. In this work, the effects of high count rate on the capability of isotope identification algorithms are explored. It is shown that a small gain shift of a few tens of keV is sufficient to disturb identification. The onset of this and other spectral effects are estimated for several systems., and a mechanism for mitigating these effects by estimating and correcting for them is implemented and evaluated.

  8. Beam cleanup and low distortion amplification in efficient high-gain hydrogen Raman amplifiers

    SciTech Connect

    Komine, H.; Long W.H. Jr.; Stappaerts, E.A.; Brosnan, S.J.

    1986-10-01

    We report the results of a theoretical and experimental investigation of two important properties of Raman converters. The first property is Raman beam cleanup, which refers to the generation of high-quality Stokes beams in a Raman amplifier pumped by laser beams of poor spatial quality. The second is nearly distortion-free amplification of aberrated Stokes beams in a Raman amplifier pumped by good-quality laser beams. A parallel beam geometry was used with collinear pump and Stokes beams. In both cases, excellent energy-conversion efficiencies into the first Stokes order, of the order of 60%, were demonstrated at high amplifier gains of 100 to 1000. The spatial characteristics of the amplified beams were found to be in good agreement with model predictions.

  9. Design of a high-power, high-gain, 2nd harmonic, 22.848 GHz gyroklystron

    SciTech Connect

    Veale, M. [University of California, Berkeley, CA, 24720 (United States)] [University of California, Berkeley, CA, 24720 (United States); Purohit, P. [Qualcomm Technologies, Inc. USA (United States)] [Qualcomm Technologies, Inc. USA (United States); Lawson, W. [University of Maryland, College Park, MD 20742 (United States)] [University of Maryland, College Park, MD 20742 (United States)

    2013-08-15

    In this paper we consider the design of a four-cavity, high-gain K-band gyroklystron experiment for high gradient structure testing. The frequency doubling gyroklystron utilizes a beam voltage of 500 kV and a beam current of 200 A from a magnetron injection gun (MIG) originally designed for a lower-frequency device. The microwave circuit features input and gain cavities in the circular TE{sub 011} mode and penultimate and output cavities that operate at the second harmonic in the TE{sub 021} mode. We investigate the MIG performance and study the behavior of the circuit for different values of perpendicular to parallel velocity ratio (?= V{sub ?}/ V{sub z}). This microwave tube is expected to be able to produce at least 20 MW of power in 1?s pulses at a repetition rate of at least 120 Hz. A maximum efficiency of 26% and a large signal gain of 58 dB under zero-drive stable conditions were simulated for a velocity ratio equal to 1.35.

  10. A low power, high dynamic-range, broadband variable gain amplifier for an ultra wideband receiver 

    E-print Network

    Chen, Lin

    2007-09-17

    A fully differential Complementary Metal-Oxide Semiconductor (CMOS) Variable Gain Amplifier (VGA) consisting of complementary differential pairs with source degeneration, a current gain stage with programmable current mirror, and resistor loads...

  11. Ultra-broadband, high-gain, polarization-independent optical parametric amplification in type-II quasi-phase-

    E-print Network

    Kolner, Brian H.

    -independent operation. Ref [1] demonstrated polarization insensitive wavelength conversion using DFG over 40 nm 1-dUltra-broadband, high-gain, polarization-independent optical parametric amplification in type (300 nm) and uniform (20 dB) with polarization

  12. Progress in laboratory high gain ICF (inertial confinement fusion): Prospects for the future

    SciTech Connect

    Storm, E.; Lindl, J.D.; Campbell, E.M.; Bernat, T.P.; Coleman, L.W.; Emmett, J.L.; Hogan, W.J.; Hunt, J.T.; Krupke, W.F.; Lowdermilk, W.H.

    1988-01-01

    Inertial confinement fusion (ICF), a thermonuclear reaction in a small (/approximately/5 mm diameter) fuel capsule filled with a few milligrams of deuterium and tritium, has been the subject of very fruitful experimentation since the early 1970's. High gain ICF is now on the threshold of practical applications. With a Laboratory Microfusion Facility (LMF), these applications will have major implications for national defense, basic and applied science, and power production. With a driver capable of delivering about 10 MJ in a 10-ns pulse at an intensity of /approximately/3 /times/ 10/sup 14/ W/cm/sup 2/, an appropriately configured cryogenic capsule could be compressed to a density of about 200 g/cm/sup 3/ and a temperature of 3--5 keV. Under these conditions, up to 10 mg of DT could be ignited, and with a burn efficiency of about 30%, release up to 1000 MJ of fusion energy, an energy gain of about 100. A thousand megajoules is equivalent to about one quarter ton of TNT, or about 7 gallons of oil--an amount of energy tractable under laboratory conditions and potentially very useful for a variety of applications. 61 refs., 33 figs.

  13. Progress in laboratory high gain ICF (Inertial Confinement Fusion): Prospects for the future

    NASA Astrophysics Data System (ADS)

    Storm, Erik; Lindl, J. D.; Campbell, E. M.; Bernat, T. P.; Coleman, L. W.; Emmett, J. L.; Hogan, W. J.; Hunt, J. T.; Krupke, W. F.; Lowdermilk, W. H.

    Inertial Confinement Fusion (ICF), a thermonuclear reaction in a small (approximately 5 mm diameter) fuel capsule filled with a few milligrams of deuterium and tritium, has been the subject of very fruitful experimentation since the early 1970's. High gain ICF is now on the threshold of practical applications. With a Laboratory Microfusion Facility (LMF), these applications will have major implications for national defense, basic and applied science, and power production. With a driver capable of delivering about 10 MJ in a 10-ns pulse at an intensity of approximately 3 X 10 to the 14th W/sq cm, an appropriately configured cryogenic capsule could be compressed to a density of about 200 g/ cu cm and a temperature of 3 to 5 keV. Under these conditions, up to 10 mg of DT could be ignited, and with a burn efficiency of about 30 percent, release up to 1000 MJ of fusion energy, an energy gain of about 100. A thousand megajoules is equivalent to about one quarter ton of TNT, or about 7 gallons of oil--an amount of energy tractable under laboratory conditions and potentially very useful for a variety of applications.

  14. IEEEJOURNAL OF QUANTUMELECTRONICS, VOL. QE-21,NO. 7, JULY 1985 831 High-Gain Free Electron Lasers Using Induction

    E-print Network

    Wurtele, Jonathan

    radiation. Induction linacs [2] can produce high-current, highIEEEJOURNAL OF QUANTUMELECTRONICS, VOL. QE-21,NO. 7, JULY 1985 831 High-Gain Free Electron Lasers, AND J. S. WURTELE Abstract-High-power free electron lasers (FEL's) can be realized using induction

  15. High performance quantum cascade lasers: Loss, beam stability, and gain engineering

    NASA Astrophysics Data System (ADS)

    Bouzi, Pierre Michel

    Quantum Cascade (QC) lasers are semiconductor devices emitting in the mid-infrared (3-30 micron) and terahertz (30-300 micron) regions of the electromagnetic spectrum. Since their first demonstration by Jerome Faist et. al. in 1994, they have evolved very quickly into high performance devices and given rise to many applications such as trace-gas sensing, medical diagnosis, free-space communication, and light detection and ranging (LIDAR). In this thesis, we investigate a further increase of the performance of QC devices and, through meticulous device modeling and characterizations, gain a deeper understanding of several of their unique characteristics, especially their carrier transport and lifetime, their characteristic temperature, their waveguide loss and modal gain, their leakage current, and their transverse mode profile. First, in our quest to achieve higher performance, we investigate the effect of growth asymmetries on device transport characteristics. This investigation stems from recent studies on the role of interface roughness on intersubband scattering and device performance. Through a symmetric active core design, we find that interface roughness and ionized impurity scattering induced by dopant migration play a significant role in carrier transport through the device. Understanding how interface roughness affects intersubband scattering, in turn, we engineer the gain in QC devices by placing monolayer barriers at specific locations within the device band structure. These strategically placed additional thin barrier layers introduce roughness scattering into the device active region, thereby selectively decreasing the lower laser state lifetime and increasing population inversion necessary for laser action. Preliminary measurement results from modified devices reveal a 50% decrease in the emission broadening compared to the control structures, which should lead to a two-fold increase in gain. A special class of so-called "strong coupling" QC lasers recently emerged with high optical power and high efficiency at cryogenic temperatures. However their performances decay rather rapidly with temperature in both pulsed and continuous wave modes. Through detailed measurements and analysis, we investigate several possible causes of this shortcoming and propose design modifications for temperature performance improvement. While the strong coupling devices are efficient and powerful, their performance often suffers from unintentional and potentially harmful beam steering at high power. Here, we identify the root of this pointing instability to be from non-linear interactions between multiple transverse modes. And, to resolve this issue, we employ focused ion beam (FIB) milling to etch small lateral constrictions on top of the devices and fill them with metal. This has the effect of greatly reducing the intensity of higher order transverse modes as they propagate through the cavity. A good grasp of the microscopic details involved in QC device operations will result in better lasers, with high beam quality. This, in turn, will enable new applications, such as the detection of SO2 isotopologues near 7.4 micron, which is of particular importance for the study of ultraviolet photolysis and the sulfur cycle on Venus.

  16. Verbal Marking of Affect by Children with Asperger Syndrome and High Functioning Autism during Spontaneous Interactions with Family Members

    ERIC Educational Resources Information Center

    Muller, Eve; Schuler, Adriana

    2006-01-01

    Verbal marking of affect by older children with Asperger Syndrome (AS) and high functioning autism (HFA) during spontaneous interactions is described. Discourse analysis of AS and HFA and typically developing children included frequency of affective utterances, affective initiations, affective labels and affective explanations, attribution of…

  17. Radiation Spectrum Statistics in a High-Gain Free-Electron Laser at 266 nm

    SciTech Connect

    Shaftan, T.; Sheehy, B.; Yu, L.H.; Murphy, J.B.; Krinsky, S.; Rose, J.; Watanabe, T.; Liu, D.; Wang, X.J.; /Brookhaven; Loos, H.; /SLAC

    2005-12-14

    High Gain Harmonic Generation FEL is in operations at the DUV-FEL facility (BNL). During HGHG FEL characterization we have measured a set of data demonstrating basic properties of the FEL radiation and compared them with analytic calculations [1]. This paper describes continuation of characterization of the HGHG FEL radiation output, based on the spectral measurements. We discuss analysis of an experiment at which the tunability concept of a seeded FEL with a fixed seed wavelength has been verified [2]. During the experiment we recorded about 200 radiation spectra corresponding to different energy chirps in the electron beam. We have analyzed this set of spectral data to obtain statistical properties of HGHG radiation. Correlations and trends in the radiation spectrum at 266 nm have been observed and studied.

  18. RADIATION SPECTRUM STATISTICS IN A HIGH-GAIN FREE-ELECTRON LASER AT 266NM.

    SciTech Connect

    STAFTAN, T.; SHEEHY, B.; LOOS, H.; YU, L.H.; MURPHY, J.B.; KRINSKY, S.; ROSE, J.; WATANABE, T.; LIU, D.; WANG, X.J.

    2005-08-21

    High Gain Harmonic Generation FEL is in operations at the DUV-FEL facility (BNL). During HGHG FEL characterization we have measured a set of data demonstrating basic properties of the FEL radiation and compared them with analytic calculations [1]. This paper describes continuation of characterization of the HGHG FEL radiation output, based on the spectral measurements. We discuss analysis of an experiment at which the tunability concept of a seeded FEL with a fixed seed wavelength has been verified [2]. During the experiment we recorded about 200 radiation spectra corresponding to different energy chirps in the electron beam. We have analyzed this set of spectral data to obtain statistical properties of HGHG radiation. Correlations and trends in the radiation spectrum at 266 nm have been observed and studied.

  19. High-gain inverters based on WSe2 complementary field-effect transistors.

    PubMed

    Tosun, Mahmut; Chuang, Steven; Fang, Hui; Sachid, Angada B; Hettick, Mark; Lin, Yongjing; Zeng, Yuping; Javey, Ali

    2014-05-27

    In this work, the operation of n- and p-type field-effect transistors (FETs) on the same WSe2 flake is realized,and a complementary logic inverter is demonstrated. The p-FET is fabricated by contacting WSe2 with a high work function metal, Pt, which facilities hole injection at the source contact. The n-FET is realized by utilizing selective surface charge transfer doping with potassium to form degenerately doped n+ contacts for electron injection. An ON/OFF current ratio of >10(4) is achieved for both n- and p-FETs with similar ON current densities. A dc voltage gain of >12 is measured for the complementary WSe2 inverter. This work presents an important advance toward realization of complementary logic devices based on layered chalcogenide semiconductors for electronic applications. PMID:24684575

  20. NASA/Cousteau ocean bathymetry experiment. Remote bathymetry using high gain LANDSAT data

    NASA Technical Reports Server (NTRS)

    Polcyn, F. C.

    1976-01-01

    Satellite remote bathymetry was varified to 22 m depths where water clarity was defined by alpha = .058 1/m and bottom reflection, r(b), was 26%. High gain band 4 and band 5 CCT data from LANDSAT 1 was used for a test site in the Bahama Islands and near Florida. Near Florida where alpha = .11 1/m and r(b) = 20%, depths to 10 m were verified. Depth accuracies within 10% rms were achieved. Position accuracies within one LANDSAT pixel were obtained by reference to the Transit navigation satellites. The Calypso and the Beayondan, two ships, were at anchor on each of the seven days during LANDSAT 1 and 2 overpasses: LORAN C position information was used when the ships were underway making depth transects. Results are expected to be useful for updating charts showing shoals hazardous to navigation or in monitoring changes in nearshore topography.

  1. High-gain wideband high-power 200GHz multiple-beam serpentine TWT design

    Microsoft Academic Search

    Khanh Nguyen; L. Ludeking; J. Pasour; D. Pershing; E. Wright; D. K. Abe; B. Levush

    2010-01-01

    Serpentine traveling-wave tubes (TWTs) are a class of vacuum electronic devices capable of wideband (25%), high power performance. However, their bandwidth depends critically on the path length along a half-period of the serpentine waveguide (from gap to gap). At THz frequencies (200 to 1000 GHz), beam tunnel diameters well below 200 ?m are required to achieve bandwidth ~20%. On this

  2. Nanoparticle-assisted high photoconductive gain in polymer/fullerene matrix

    PubMed Central

    Chen, Hsiang-Yu; Lo, Michael K. F.; Yang, Guanwen; Monbouquette, Harold G.; Yang, Yang

    2014-01-01

    Polymer/inorganic nanocrystal composites1–10 offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by the solubility11 and distribution of nanocrystals (NCs) in polymer matrices. Here, a high photoconductive gain has been achieved by blending cadmium telluride (CdTe) nanoparticles (NPs) into a polymer/fullerene matrix followed by a solvent annealing12 process. The NP surface capping ligand, N-phenyl-N’-methyldithiocarbamate, renders the NPs highly soluble in the polymer blend thereby enabling high nanocrystal loadings. An external quantum efficiency (EQE) as high as ~8000% (at 350nm) is reached at ?4.5V. Hole-dominant devices coupled with AFM images are studied to uncover the probable mechanism. We observe a higher concentration of CdTe NPs is located near the cathode/polymer interface. These NPs with trapped electrons assist hole injection into the polymer under reverse bias, which contributes to greater than 100% EQE. PMID:18772915

  3. High-gain, high-speed ZnO MSM ultraviolet photodetectors[Metal-Semiconductor-Metal

    SciTech Connect

    Shen, H.; Wraback, M.; Gorla, C.R.; Liang, S.; Emanetoglu, N.; Liu, Y.; Lu, Y.

    2000-07-01

    High quality zinc oxide (ZnO) films were epitaxially grown on R-plane sapphire substrates by metalorganic chemical vapor deposition at temperatures in the range 350--600 C. In-situ nitrogen compensation doping was performed using NH{sub 3}. The metal-semiconductor-metal ultraviolet-sensitive photodetectors were fabricated on nitrogen-compensation-doped epitaxial ZnO films. The photoresponsivity of these devices exhibits a linear dependence upon bias voltage up to 10 V, with a photoresponsivity of 400 A/W at 5 V. The rise and fall times are 1 and 1.5 {micro}s, respectively.

  4. Commensal E. coli Stx2 lysogens produce high levels of phages after spontaneous prophage induction

    PubMed Central

    Iversen, Hildegunn; L' Abée-Lund, Trine M.; Aspholm, Marina; Arnesen, Lotte P. S.; Lindbäck, Toril

    2015-01-01

    Enterohemorrhagic E. coli (EHEC) is a food-borne pathogen that causes disease ranging from uncomplicated diarrhea to life-threatening hemolytic uremic syndrome (HUS) and nervous system complications. Shiga toxin 2 (Stx2) is the major virulence factor of EHEC and is critical for development of HUS. The genes encoding Stx2 are carried by lambdoid bacteriophages and the toxin production is tightly linked to the production of phages during lytic cycle. It has previously been suggested that commensal E. coli could amplify the production of Stx2-phages and contribute to the severity of disease. In this study we examined the susceptibility of commensal E. coli strains to the Stx2-converting phage ?734, isolated from a highly virulent EHEC O103:H25 (NIPH-11060424). Among 38 commensal E. coli strains from healthy children below 5 years, 15 were lysogenized by the ?734 phage, whereas lytic infection was not observed. Three of the commensal E. coli ?734 lysogens were tested for stability, and appeared stable and retained the phage for at least 10 cultural passages. When induced to enter lytic cycle by H2O2 treatment, 8 out of 13 commensal lysogens produced more ?734 phages than NIPH-11060424. Strikingly, five of them even spontaneously (non-induced) produced higher levels of phage than the H2O2 induced NIPH-11060424. An especially high frequency of HUS (60%) was seen among children infected by NIPH-11060424 during the outbreak in 2006. Based on our findings, a high Stx2 production by commensal E. coli lysogens cannot be ruled out as a contributor to the high frequency of HUS during this outbreak. PMID:25692100

  5. Experimental characteristics of a high-gain free-electron laser amplifier operating at 8-mm and 2-mm wavelengths

    SciTech Connect

    Throop, A.L.; Orzechowski, T.J.; Anderson, B.R.; Chambers, F.W.; Clark, J.C.; Fawley, W.M.; Jong, R.A.; Halbach, K.; Hopkins, D.B.; Sessler, A.M.

    1987-06-08

    The Electron Laser Facility (ELF) at the Lawrence Livermore National Laboratory (LLNL) uses a high-current induction linac (3.5 MeV, 1000 A), in conjunction with a pulsed electromagnetic wiggler (4.0 M, 4000 G), to operate a free electron laser (FEL) that produces intense radiation in the microwave regime (2 to 8 mm). ELF is a high-gain, single-pass amplifier, using a commercial microwave source as an oscillator input (200 W-50 kW). Previous experiments at 35 GHz produced exponential gains of 40 dB/m, peak powers exceeding 1 GW, and beam-to-rf conversion efficiencies of 34%. Recent experiments at 140 GHz have demonstrated exponential gains of 22 dB/m, peak powers exceeding 50 MW, and total gains of 65 dB. In this paper, we describe the experimental results at these two frequencies and compare then with the predictions of simulation codes.

  6. Fructose-induced leptin resistance exacerbates weight gain in response to subsequent high-fat feeding

    NSDL National Science Digital Library

    Alexandra Shapiro (University of Florida Pharmacology and Therapeutics)

    2008-08-16

    It has been suggested that increased fructose intake is associated with obesity. We hypothesized that chronic fructose consumption causes leptin resistance, which subsequently may promote the development of obesity in response to a high fat diet. Sprague-Dawley rats were fed a fructose-free control or 60% fructose diet for six months and then tested for leptin resistance. Half of the rats in each group were then switched to high fat diet for two weeks, while the other half continued on their respective diets. Chronic fructose consumption caused leptin resistance while serum leptin levels, weight and adiposity were the same as in control rats that were leptin responsive. Intraperitoneal leptin injections reduced 24-hour food intake in fructose-free group (73.7 ± 6.3 vs 58.1 ± 8 kcal, p=0.02), but had no effect in fructose-fed rats (71.2 ± 6.6 vs 72.4 ± 6.4 kcal, p=0.9). Absence of anorexic response to intraperitoneal leptin injection was associated with 25.7% decrease in hypothalamic signal transducer and activator of transcription 3 (STAT3) phosphorylation in the high-fructose fed rats compared with controls (p=0.015). Subsequent exposure of the fructose-mediated leptin-resistant rats to a high fat diet lead to exacerbated weight gain (50.2 ± 2 g) compared with correspondingly fed leptin-responsive animals that were pre-treated with the fructose-free diet (30.4 ± 5.8 g, p= 0.012). Our data indicate that chronic fructose consumption induces leptin resistance prior to body weight, adiposity, serum leptin, insulin or glucose increases, and this fructose-induced leptin resistance accelerates high fat induced obesity

  7. Spontaneous emission enhancement in a microtube cavity with highly confined optical modes

    NASA Astrophysics Data System (ADS)

    Rakovich, Y. P.; Balakrishnan, S.; Gun'ko, Y.; Perova, T. S.; Moore, A.; Donegan, J. F.

    2007-06-01

    A detailed study of the photonic modes in microtube cavity of ~ 7-8 ?m outer diameter is presented. We demonstrate a new route to the fabrication of individual microtubes with the maximum length of 200 ?m, using a vacuum assisted wetting and filtration through a microchannel glass matrix. The microtubes were studied using micro-photoluminescence spectroscopy and luminescence lifetime imaging confocal microscopy. In the emission spectra of the microresonators we find periodic very narrow peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors upto 3200 at room temperature. In order to identify the peaks in the observed mode structure, we have adopted the boundary-value solution to the problem of scattering of electromagnetic waves by a dielectric microcylinder. A strong enhancement in photoluminescence decay rates at high excitation power suggest the occurrence of amplified spontaneous emission from a single microtube. The evanescent field in these photonic structures extends a couple of micrometers into the surroundings providing the possibility for efficient coupling to an external photonic device.

  8. Dynamics of high power gain switched DFB RW laser under high current pulse excitation on a nanosecond time scale

    NASA Astrophysics Data System (ADS)

    Klehr, A.; Schwertfeger, S.; Wenzel, H.; Hoffmann, Th.; Liero, A.; Staske, R.; Brox, O.; Erbert, G.; Tränkle, G.

    2013-03-01

    In this paper we present detailed experimental results of the impact of the amplitude and the widths of current pulses injected into a gain-switched distributed feedback (DFB) laser emitting at a wavelength of 1064 nm. The laser with a InGaAs triple quantum well active region has a 3 ?m wide ridge waveguide (RW) and a cavity length of 1.5 mm. Gainswitching is achieved by injecting current pulses with a width of 50 ns, a repetition frequency of 200 kHz and a very high amplitude up to 40 times the threshold current (2.5 A). Time resolved investigations show, that depending on the amplitude and the duration of the current pulses, the optical power exhibits different types of oscillatory behavior during the pulses, accompanied by changes in the lateral near field intensity profiles and optical spectra. Three different types of instabilities can be distinguished: Mode beating with frequencies between 25 GHz and 30 GHz, switching between different lateral modes and self-sustained oscillations with a frequency of about 4 GHz. Our results are relevant for the utilization of gain-switched DFB-RW lasers as seed lasers for fiber laser systems and in other applications, which require high optical power.

  9. High-frequency ? electroencephalogram activity in association with sleep-wake states and spontaneous behaviors in the rat

    Microsoft Academic Search

    K. J. Maloney; E. G. Cape; J. Gotman; B. E. Jones

    1997-01-01

    The occurrence of high-frequency ? activity (30–60 Hz) and its relationship to other frequency band activities were examined by spectral analysis of the electroencephalogram in association with sleep-wake states and spontaneous behaviors in the rat. In the electroencephalogram, ? wave activity was evident in unfiltered and high-frequency filtered recordings, in which it was prominent during attentive or active Wake episodes

  10. High-gain harmonic generation of soft X-rays with the `fresh bunch` technique

    SciTech Connect

    Yu, Li-Hua; Ben-Zvi, I.

    1996-10-01

    We report numerical simulations (using the TDA code) and analytic verification of the generation of 64 {Angstrom} high power soft X- rays from an exponential regime single pass seeded FEL. The seed is generated in the FEL using the High Gain Harmonic Generation (HGHG) technique combined with the `Fresh bunch` technique. A seed pulse at 2944 {Angstrom} is generated by conventional laser techniques. The seed pulse produces an intense energy modulation of the rear part of a I GeV, 1245 {Angstrom} electron beam in a `modulator` wiggler. In the `radiator` wiggler, (resonant to 64 {Angstrom}), the energy modulation creates beam density modulation followed by radiation of the 46{sup th} harmonic of the seed. We use a magnetic delay to position the 64 A{Angstrom} radiation at the undisturbed front of the bunch to serve as a seed for a single pass, exponential growth FEL. After a 9 m long exponential section followed by a 7 m long tapered section the radiation power reaches 3.3 GW.

  11. A 12-pass laser amplifier scheme for achieving efficient high gain amplification

    Microsoft Academic Search

    A. M. Scott; H. Cook; A. P. G. Davies

    2000-01-01

    If one wishes to extract energy from an amplifier one usually requires substantial input energies, and the net gain is modest. Gain and energy extraction can be improved by double passing an amplifier system, often using nonlinear optical phase conjugation to compensate for aberrations. In amplifier systems it is often convenient to use relay imaging, using an intermediate telescope. In

  12. Amplified spontaneous emission in pulse-pumped Raman amplifiers

    Microsoft Academic Search

    Jake Bromage; P. J. Winzer; L. E. Nelson; M. D. Mermelstein; C. Horn; C. H. Headley

    2003-01-01

    We discuss amplified spontaneous emission (ASE) generated in Raman amplifiers that are counter-pumped with trains of pulses. Our experimental and theoretical results show that if the peak power of the pump pulses is too high, the ASE output from the amplifier can be significantly higher than that from a continuous-wave pumped amplifier providing the same gain. This effect places a

  13. Case study of sample spacing in planar near-field measurement of high gain antennas

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.; Lee, R. Q.

    1984-01-01

    Far field antenna patterns can be reconstructed from planar near field measurements acquired at a sample spacing of lambda/2 or less. For electrically large antennas, sampling at the Nyquist rate may result in errors due to system electronic drift over long acquisition times. The computer capacity may limit the largest size of the near field data set. The requirement to sample at the Nyquist rate is relaxed for high gain antennas which concentrate most of the radiated energy into a small angular region of the far field. The criteria for sample spacing at greater than lambda/e through the use of a priori information of the antenna radiation characteristics are presented. Far field patterns of a 30 GHz dual offset reflector system with a 2.7 m parabolic main reflector are computed from near field data obtained at sample spacings ranging from 0.1 lambda to 10 lambda. The effects of sampling interval and spectrum cutoff on the far field patterns are discussed.

  14. Design parameters of the high gain harmonic generation experiment using Cornell Undulator A at the ATF

    SciTech Connect

    Yu, L.H. [Brookhaven National Lab., Upton, NY (United States)

    1998-10-01

    The authors present the design parameters of a high gain harmonic generation (HGHG) FEL experiment to be carried out at the accelerator test facility (ATF) at BNL, in collaboration with APS. This experiment is a proof-of-principle experiment for the DUV-FEL at BNL. In the HGHG experiment the author plans to double the frequency of a CO{sub 2} seed layer by utilizing a 0.76 m long 9 period undulator (named the Mini Undulator), a 2 m long 60 period undulator (named the Cornell Undulator A), and a 0.3 m electromagnet chicane (the dispersive section). The first undulator will be used in conjunction with the CO{sub 2} seed laser to generate a ponderomotive force that will bunch the electron beam. The bunching will then be enhanced by the dispersion section. The second undulator, the Cornell Undulator A, tuned to the second harmonic of the seed laser will serve as the radiator. In the beginning of the radiator the bunched beam will produce coherent emission (characterized by a quadratic growth of the radiated power), then the radiation will be amplified exponentially. The author plans to study the evolution of the various radiation growth mechanisms as well as the coherence of the doubled, exponentially amplified radiation.

  15. DESIGN PARAMETERS OF THE HIGH GAIN HARMONIC GENERATION EXPERIMENT USING CORNELL UNDULATOR A AT THE ATF

    SciTech Connect

    YU,L.H.

    1998-10-27

    The authors present the design parameters of a high gain harmonic generation (HGHG) FEL experiment to be carried out at the accelerator test facility (ATF) at BNL, in collaboration with APS. This experiment is a proof-of-principle experiment for the DUV-FEL at BNL. In the HGHG experiment they plan to double the frequency of a CO{sub 2} seed laser by utilizing a 0.76 m long 9 period undulator (named the Mini Undulator), a 2 m long 60 period undulator (named the Cornell Undulator A), and a 0.3 m electromagnet chicane (the dispersive section). The first undulator will be used in conjunction with the CO{sub 2} seed laser to generate a ponderomotive force that will bunch the electron beam. The bunching will then be enhanced by the dispersion section. The second undulator, the Cornell Undulator A, tuned to the second harmonic of the seed laser will serve as the radiator. In the beginning of the radiator the bunched beam will produce coherent emission (characterized by a quadratic growth of the radiated power), then the radiation will be amplified exponentially. They plan to study the evolution of the various radiation growth mechanisms as well as the coherence of the doubled, exponentially amplified radiation.

  16. Liver fatty acid binding protein gene-ablation exacerbates weight gain in high-fat fed female mice.

    PubMed

    McIntosh, Avery L; Atshaves, Barbara P; Landrock, Danilo; Landrock, Kerstin K; Martin, Gregory G; Storey, Stephen M; Kier, Ann B; Schroeder, Friedhelm

    2013-05-01

    Loss of liver fatty acid binding protein (L-FABP) decreases long chain fatty acid uptake and oxidation in primary hepatocytes and in vivo. On this basis, L-FABP gene ablation would potentiate high-fat diet-induced weight gain and weight gain/energy intake. While this was indeed the case when L-FABP null (-/-) mice on the C57BL/6NCr background were pair-fed a high-fat diet, whether this would also be observed under high-fat diet fed ad libitum was not known. Therefore, this possibility was examined in female L-FABP (-/-) mice on the same background. L-FABP (-/-) mice consumed equal amounts of defined high-fat or isocaloric control diets fed ad libitum. However, on the ad libitum-fed high-fat diet the L-FABP (-/-) mice exhibited: (1) decreased hepatic long chain fatty acid (LCFA) ?-oxidation as indicated by lower serum ?-hydroxybutyrate level; (2) decreased hepatic protein levels of key enzymes mitochondrial (rate limiting carnitine palmitoyl acyltransferase A1, CPT1A; HMG-CoA synthase) and peroxisomal (acyl CoA oxidase 1, ACOX1) LCFA ?-oxidation; (3) increased fat tissue mass (FTM) and FTM/energy intake to the greatest extent; and (4) exacerbated body weight gain, weight gain/energy intake, liver weight, and liver weight/body weight to the greatest extent. Taken together, these findings showed that L-FABP gene-ablation exacerbated diet-induced weight gain and fat tissue mass gain in mice fed high-fat diet ad libitum--consistent with the known biochemistry and cell biology of L-FABP. PMID:23539345

  17. Optimization on the design of an ultra-high-power multisection tunable laser gain epilayers

    NASA Astrophysics Data System (ADS)

    Zhang, Yaping; Benson, Trevor M.; Christopoulos, Christos

    2007-02-01

    Great efforts and vast investments have been put into the research and development of widely tunable lasers in the last 25 years. Tunable lasers have become critical components in the implementation of next generation telecommunication networks and systems, to provide dynamic wavelength provision for channel restoration, reconfiguration and protection. Some stringent requirements have been imposed on tunable lasers by telecommunication applications. Consequently, ultra-high optical output power (>=100 mW), wide tunability (tuning range ~ 40nm), narrow linewidth (< 2MHz), and side-mode suppression ratio (SMSR > 40dB) have become the main objectives for the development of the future telecommunication tunable lasers. Facet output power is the fundamental decisive factor among these targets. Original design ideas and novel approaches to the design of ultra-high power InGaAsP/InP based multisection widely-tunable laser gain section have been reported by the authors previously, mainly including: firstly, a bulk balance layer structure is placed above the InP buffer layer and below the MQWs stack, which enables a large reduction of free-carrier absorption loss by greatly shifting the optical field distribution to the intrinsic and n-doped sides. Secondly, an InP spacer layer is placed below the ridge and above the multiple quantum wells (MQWs) stack, so as to introduce extra freedom in the control of widening the single mode ridge width. This paper will focus on the optimization on the implementation of the above design ideas and approaches, regarding single mode ridge width, optical confinement in the MQWs, optical overlap with the p-doped epilayers, output power, threshold current, and slope efficiency.

  18. A High Gain, Composite Nd:YVO4/SiC Thin Disk Amplifier

    NASA Astrophysics Data System (ADS)

    Newburgh, G. A.; Dubinskii, Mark

    2014-06-01

    We have demonstrated a new form of Nd:YVO4 amplifier operating at 1064 nm based on a 800 µm thick Nd:YVO4 gain layer bonded to a 4H-SiC prism. The amplifier was tested in the `master oscillator - power amplifier' (MOPA) configuration, where both the seed source and the single pass amplifier were operated in a quasi-continuous wave (Q-CW) regime: pulse duration 500 µs, pulse repetition frequency (PRF) - 100 Hz. The Nd:YVO4gain element was pumped by a 808 nm laser diode bar stack to amplify seed inputs in the power range of 1 to 55 W with a gains of 4 to 2.6, respectively, with 25% optical-to-optical extraction efficiency. The temperature distribution of the gain medium was measured under operational conditions using thermography.

  19. Experimental and theoretical investigations of the spontaneous infrared radiation fluctuations of a high-pressure, high-current argon discharge.

    PubMed

    Gubler, W; Strutt, M J

    1966-04-01

    The equations describing the spontaneous fluctuations of photon radiation are given by the Bose-Einstein statistics. These equations are applied to calculate the statistical fluctuations of photon radiation emitted by a nonhomogeneous plasma. By using a photodetector, the radiation fluctuations are transformed into corresponding output current fluctuations. The detector must have special properties as to sensitivity, noise, frequency response, and transmission characteristics. The InSb photodetector described here has the required properties. As a radiation source, the plasma of a stationary argon arc discharge at high pressure was used. By measuring and calculating the continuous photon radiation, it is possible to determine the temperature distribution in the plasma. Investigations of the electrical conductivity confirm the temperature distributions. Because of the high temperatures, as well as the sufficient optical thickness in the infrared spectral range, determination of the fluctuation factors is made possible. Considering the experimental difficulties, the agreement between measured and calculated factors is good. Instabilities in the plasma have been considered and eliminated in the experimental procedure. PMID:20048913

  20. Overview of new high gain target design for a laser fusion power plant

    Microsoft Academic Search

    S. E Bodner; D. G Colombant; A. J Schmitt; J. H Gardner; R. H Lehmberg; S. P Obenschain

    2002-01-01

    We have developed a new direct-drive target design that has a predicted energy gain of 127 using a 1.3 MJ KrF laser, and a gain of 155 using 3.1 MJ. The DT fuel is surrounded by an ablator consisting of a low density CH foam filled with frozen DT. The ablator is then surrounded by a thin CH coating and

  1. Peroxisome proliferator-activated receptor-? activator fenofibrate prevents high-fat diet-induced renal lipotoxicity in spontaneously hypertensive rats

    Microsoft Academic Search

    Seok Joon Shin; Ji Hee Lim; Sungjin Chung; Dong-Ye Youn; Hyun Wha Chung; Hyung Wook Kim; Jeong-Hwa Lee; Yoon Sik Chang; Cheol Whee Park

    2009-01-01

    We investigated the effects of a high-fat (HF) diet and peroxisome proliferator-activated receptor (PPAR)-? activation on the intrarenal lipotoxicity associated with the renin–angiotensin system (RAS) and oxidative stress using spontaneously hypertensive (SHR) rats. Male SHR and Wistar–Kyoto (WKY) rats at 8 weeks of age were fed either a normal-fat diet or an HF diet without or with fenofibrate treatment for

  2. 100 nm bandwidth flat gain Raman amplifiers pumped and gain-equalized by 12-wavelength-channel WDM high power laser diodes

    Microsoft Academic Search

    Y. Emori; S. Namiki

    1999-01-01

    We demonstrate 100 nm bandwidth Raman amplifiers using 12-wavelength-channel WDM pump laser diode unit. The gain flatness is less than ±0.5 dB, which is achieved through an asymmetric channel allocation of pump and without any gain equalization filters

  3. Non-stoichiometric W18O49-xSx nanowires for wide spectrum photosensors with high internal gain

    NASA Astrophysics Data System (ADS)

    Hsu, Yu-Ming; Wang, Chiu-Yen; Chang, Pin; Yew, Tri-Rung

    2014-12-01

    This study reports successful synthesis of non-stoichiometric single-crystal W18O49-xSx nanowires for photosensors with a high absorption rate (>83%) across a wide spectrum (300-2000 nm), a high internal gain (G = 106-107) and a relatively fast response time (approximately 1-3 s). In addition, the correlation between the photoconductivity gain (G) and the surface-to-volume ratio of non-stoichiometric single-crystal W18O49-xSx nanowires was studied. The surface-to-volume ratio and non-stoichiometric material of W18O49-xSx contributed to the photoconductivity gain; hence, the nanowires are favorable for photosensor devices. The wide spectrum obtained also suggests their extensive applications in numerous fields.This study reports successful synthesis of non-stoichiometric single-crystal W18O49-xSx nanowires for photosensors with a high absorption rate (>83%) across a wide spectrum (300-2000 nm), a high internal gain (G = 106-107) and a relatively fast response time (approximately 1-3 s). In addition, the correlation between the photoconductivity gain (G) and the surface-to-volume ratio of non-stoichiometric single-crystal W18O49-xSx nanowires was studied. The surface-to-volume ratio and non-stoichiometric material of W18O49-xSx contributed to the photoconductivity gain; hence, the nanowires are favorable for photosensor devices. The wide spectrum obtained also suggests their extensive applications in numerous fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05234j

  4. Verification of the Solar Dynamics Observatory High Gain Antenna Pointing Algorithm Using Flight Data

    NASA Technical Reports Server (NTRS)

    Bourkland, Kristin L.; Liu, Kuo-Chia

    2011-01-01

    The Solar Dynamics Observatory (SDO), launched in 2010, is a NASA-designed spacecraft built to study the Sun. SDO has tight pointing requirements and instruments that are sensitive to spacecraft jitter. Two High Gain Antennas (HGAs) are used to continuously send science data to a dedicated ground station. Preflight analysis showed that jitter resulting from motion of the HGAs was a cause for concern. Three jitter mitigation techniques were developed and implemented to overcome effects of jitter from different sources. These mitigation techniques include: the random step delay, stagger stepping, and the No Step Request (NSR). During the commissioning phase of the mission, a jitter test was performed onboard the spacecraft, in which various sources of jitter were examined to determine their level of effect on the instruments. During the HGA portion of the test, the jitter amplitudes from the single step of a gimbal were examined, as well as the amplitudes due to the execution of various gimbal rates. The jitter levels were compared with the gimbal jitter allocations for each instrument. The decision was made to consider implementing two of the jitter mitigating techniques on board the spacecraft: stagger stepping and the NSR. Flight data with and without jitter mitigation enabled was examined, and it is shown in this paper that HGA tracking is not negatively impacted with the addition of the jitter mitigation techniques. Additionally, the individual gimbal steps were examined, and it was confirmed that the stagger stepping and NSRs worked as designed. An Image Quality Test was performed to determine the amount of cumulative jitter from the reaction wheels, HGAs, and instruments during various combinations of typical operations. The HGA-induced jitter on the instruments is well within the jitter requirement when the stagger step and NSR mitigation options are enabled.

  5. Towards high accurate neutron-induced fission cross sections of 240,242Pu: Spontaneous fission half-lives

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, P.; Bry?, T.; Eykens, R.; Hambsch, F.-J.; Moens, A.; Oberstedt, S.; Pretel, C.; Sibbens, G.; Vanleeuw, D.; Vidali, M.

    2013-12-01

    Fast spectrum neutron-induced fission cross sections of transuranic isotopes are being of special demand in order to provide accurate data for the new GEN-IV nuclear power plants. To minimize the uncertainties on these measurements accurate data on spontaneous fission half-lives and detector efficiencies are a key point. High ?-active actinides need special attention since the misinterpretation of detector signals can lead to low efficiency values or underestimation in fission fragment detection. In that context, 240,242Pu isotopes have been studied by means of a Twin Frisch-Grid Ionization Chamber (TFGIC) for measurements of their neutron-induced fission cross section. Gases with different drift velocities have been used, namely P10 and CH4. The detector efficiencies for both samples have been determined and improved spontaneous fission half-life values were obtained.

  6. Spontaneous breaking of rotational symmetry in rotating solitons: A toy model of excited nucleons with high angular momentum

    SciTech Connect

    Hen, Itay; Karliner, Marek [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978 (Israel)

    2008-06-01

    We study the phenomenon of spontaneous breaking of rotational symmetry in the rotating solutions of two types of baby Skyrme models. In the first, the domain is a two-sphere, and in the other, the Skyrmions are confined to the interior of a unit disk. Numerical full-field results show that when the angular momentum of the Skyrmions increases above a certain critical value, the rotational symmetry of the solutions is broken and the minimal-energy configurations become less symmetric. We propose a possible mechanism as to why spontaneous breaking of rotational symmetry is present in the rotating solutions of these models, while it is not observed in the 'usual' baby Skyrme model. Our results might be relevant for a qualitative understanding of the nonspherical deformation of excited nucleons with high orbital angular momentum.

  7. Microstrip patch array antenna with high gain and wideband for Tx\\/Rx dual operation at Ku-band

    Microsoft Academic Search

    Haeng Sook Noh; Jae Seung Yun; Jong Myen Kim; Soon-Ik Jeon

    2004-01-01

    In this paper, a microstrip patch array antenna with high gain and wideband for dual transmitting\\/receiving at Ku-band is presented. The patch array antenna has a horizontal polarization for Rx band and a vertical polarization for Tx band. A unit element of the patch array antenna consists of one radiating patch and two parasitic patches for improving impedance bandwidth and

  8. EFFECTS OF PREVIOUS LIVEWEIGHT GAIN ON VISCERAL ORGAN MASS AND OXYGEN CONSUMPTION IN CATTLE DUING HIGH-GRAIN FEEDING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Forty-eight fall-weaned crossbred steers (231+/-25 kg) were used in a completely random design to determine the effect of previous liveweight gain on visceral organ mass and oxygen consumption. During the 143-d growing phase, treatments were high (HGW; 1.28 kg/d) or low (LGW; .48 kg/d) daily BW gai...

  9. The New Horizons high gain antenna: reflector design for a spin-stabilized bus at cryogenic temperatures

    Microsoft Academic Search

    R. C. Schulze; S. Hill

    2004-01-01

    The New Horizons antenna system is subjected to cryogenic temperatures during the Pluto and KBO encounters. The RF performance of the high gain antenna (HGA) during and after these encounters is critical for the science and communications mission requirements. In order to satisfy these requirements, the angular alignment of the HGA bore-site and spacecraft spin axis must be maintained within

  10. Optical properties of the output of a high-gain, self-amplified free-electron laser.

    SciTech Connect

    Li, Y.; Lewellen, J.; Huang, Z.; Krinsky, S.; Accelerator Systems Division (APS); BNL

    2004-01-01

    The temporal structure and phase evolutions of a high-gain, self-amplified free-electron laser are measured, including single-shot analysis and statistics over many shots. Excellent agreement with the theory of free-electron laser and photon statistics is found.

  11. High energy gain in three-dimensional simulations of light sail acceleration

    SciTech Connect

    Sgattoni, A., E-mail: andrea.sgattoni@polimi.it [Dipartimento di Energia, Politecnico di Milano, Milano (Italy); CNR, Istituto Nazionale di Ottica, u.o.s. “Adriano Gozzini,” Pisa (Italy); Sinigardi, S. [CNR, Istituto Nazionale di Ottica, u.o.s. “Adriano Gozzini,” Pisa (Italy); Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna (Italy); INFN sezione di Bologna, Bologna (Italy); Macchi, A. [CNR, Istituto Nazionale di Ottica, u.o.s. “Adriano Gozzini,” Pisa (Italy); Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Pisa (Italy)

    2014-08-25

    The dynamics of radiation pressure acceleration in the relativistic light sail regime are analysed by means of large scale, three-dimensional (3D) particle-in-cell simulations. Differently to other mechanisms, the 3D dynamics leads to faster and higher energy gain than in 1D or 2D geometry. This effect is caused by the local decrease of the target density due to transverse expansion leading to a “lighter sail.” However, the rarefaction of the target leads to an earlier transition to transparency limiting the energy gain. A transverse instability leads to a structured and inhomogeneous ion distribution.

  12. Modelling Plant and Soil Nitrogen Feedbacks Affecting Forest Carbon Gain at High CO2

    NASA Astrophysics Data System (ADS)

    McMurtrie, R. E.; Norby, R. J.; Franklin, O.; Pepper, D. A.

    2007-12-01

    Short-term, direct effects of elevated atmospheric CO2 concentrations on plant carbon gain are relatively well understood. There is considerable uncertainty, however, about longer-term effects, which are influenced by various plant and ecosystem feedbacks. A key feedback in terrestrial ecosystems occurs through changes in plant carbon (C) allocation patterns. For instance, if high CO2 were to increase C allocation to roots, then plants may experience positive feedback through improved plant nutrition. A second type of feedback, associated with decomposition of soil-organic matter, may reduce soil-nutrient availability at high CO2. This paper will consider mechanistic models of both feedbacks. Effects of high CO2 on plant C allocation will be investigated using a simple model of forest net primary production (NPP) that incorporates the primary mechanisms of plant carbon and nitrogen (N) balance. The model called MATE (Model Any Terrestrial Ecosystem) includes an equation for annual C balance that depends on light- saturated photosynthetic rate and therefore on [CO2], and an equation for N balance incorporating an expression for N uptake as a function of root mass. The C-N model is applied to a Free Air CO2 Exchange (FACE) experiment at Oak Ridge National Laboratory (ORNL) in Tennessee, USA, where closed-canopy, monoculture stands of the deciduous hardwood sweetgum ( Liquidambar styraciflua) have been growing at [CO2] of 375 and 550 ppm for ten years. Features of this experiment are that the annual NPP response to elevated CO2 has averaged approximately 25% over seven years, but that annual fine-root production has almost doubled on average, with especially large increases in later years of the experiment (Norby et al. 2006). The model provides a simple graphical approach for analysing effects of elevated CO2 and N supply on leaf/root/wood C allocation and productivity. It simulates increases in NPP and fine-root production at the ORNL FACE site that are consistent with experimental measurements. Increased below-ground C allocation has been observed at other forest high-CO2 experiments including the Duke FACE and Flakaliden experiments in North Carolina, USA, and Sweden, respectively. This result is predicted by MATE, but not by biogeochemical-cycling models such as our plant-soil model G'DAY (Generic Decomposition And Yield), which predicts instead that a positive CO2 response will enhance litter quantity, and hence will increase soil N immobilisation and reduce the pool of N available for plant uptake (Pepper et al. 2007). We will use G'DAY and MATE to determine the sensitivity of the modelled CO2 response to key model parameters on contrasting timescales. One conclusion is that models are required that simulate both increased N uptake at high CO2 as a consequence of increased root production and soil N-cycling feedbacks. References: Norby RJ, Wullschleger SD, Hanson PJ, Gunderson CA, Tschaplinski TJ, Jastrow JD (2006) CO2 enrichment of a deciduous forest: the Oak Ridge FACE experiment. Ecological Studies 187: 231-251 (Springer-Verlag, Berlin). Pepper DA, Eliasson PE, McMurtrie RE, Corbeels M, Ågren GI, Strömgren M, Linder S (2007) Simulated mechanisms of soil N feedback on the forest CO2 response. Global Change Biology 13: 1265-1281.

  13. Behavioral characterization of non-copulating male rats with high spontaneous yawning frequency rate.

    PubMed

    Portillo, Wendy; Camacho, Francisco; Eguibar, Jose R; Paredes, Raúl G

    2010-12-25

    An important number of Sprague-Dawley males selected by strict inbreeding process for their high spontaneous yawing frequency (HY) fail to copulate after repeated exposure to receptive females. These HY males that fail to mate are called non-copulators (HYNC). The causes of this behavioral deficit are still unknown. The aim of the present study was to make a detailed behavioral characterization of these animals by evaluating: their partner preference between a sexually receptive female as opposed to a sexually active male; their ability to detect food related odors and their preference for sexually relevant chemosensory cues between bedding from estrous females, bedding from sexually active males and clean bedding. We also evaluated whether these males had alterations in motor function using a rotarod or in their general reward system mediated by opioids by injecting them with 1mg/kg of morphine to evaluate if they develop conditioned place preference (CPP). At the end of these behavioral tests, we measured their plasmatic levels of testosterone (T). Together, these results will contribute to elucidate the causes of their deficient copulatory performance. Both HYNC and HY copulators (HYC) males showed a clear preference for receptive females as opposed to sexually active males. As well, both groups of animals had a similar ability to detect food related odors. HYC males had a clear preference for estrous female odors as opposed to male or clean bedding, but HYNC males spend the same amount of time sniffing estrous, anestrous, male and clean bedding. In both, HYC and HYNC, morphine induced CPP suggesting that in these males the reward system is functional. No differences were found in motor coordination or in T levels between HY and HYNC males. The behavioral deficit in HYNC male rats cannot be explained by an alteration in: partner preference, food related odor recognition, motor coordination, general reward system, or differences in plasmatic levels of T. However, HYNC males present clear deficits in recognizing sexually relevant odors. These results could, at least in part, explain the deficient execution of copulatory pattern in HYNC males. PMID:20510299

  14. Compact gain-switched Tm:YAP laser pumped by a high power laser diode around 790?nm

    NASA Astrophysics Data System (ADS)

    Cai, Shuangshuang; Yang, Dingzhong; Wu, Pinghui; Hu, Chengzhi; Jiang, Peipei

    2015-07-01

    We report, to the best of our knowledge, the first demonstration of stable pulse generation from a gain-switched Tm:YAP laser directly pumped with a modulated high power laser diode around 790?nm. A piece of Tm:YAP crystal (3% Tm3+ doping) 5?mm in diameter and 12?mm in length was used as the gain medium. To realize effective gain-switching pulse operation, the laser diode was modulated with suitable pulse repetition rates and corresponding pulse durations. Stable single pulse output was achieved with repetition rates from 1 to 20?kHz. By adjusting the cavity parameters, a maximum laser output power of 4.6?W was obtained under a pump power of 16?W with corresponding overall optical-to-optical conversion efficiency of 28.7%.

  15. An efficient fast response and high-gain solar-blind flexible ultraviolet photodetector employing hybrid geometry

    NASA Astrophysics Data System (ADS)

    Hussain, Amreen A.; Pal, Arup R.; Patil, Dinkar S.

    2014-05-01

    We report high performance flexible hybrid ultraviolet photodetector with solar-blind sensitivity using nanocomposite film of plasma polymerized aniline-titanium dioxide. A facile solvent-free plasma technique is used to synthesize superior quality hybrid material with high yield. The hybrid photodetector exhibited high photoconductive gain of the order of ˜105 and fast speed with response and recovery time of 22.87 ms and 34.23 ms. This is an excellent result towards getting a balance in the response speed and photoconductive gain trade-off of the photodetectors reported so far. In addition, the device has the advantages of enhanced photosensitivity ((Ilight - Idark)/Idark) of the order of ˜102 and high responsivity of ˜104 AW-1. All the merits substantiates that, to prepare hybrid material, plasma based method holds potential to be an easy way for realizing large scale nanostructured photodetectors for practical applications.

  16. High-gain 35GHz free-electron laser-amplifier experiment

    Microsoft Academic Search

    S. H. Gold; D. L. Hardesty; A. K. Kinkead; L. R. Barnett; V. L. Granatstein

    1984-01-01

    A new intense-beam free-electron laser experiment, operating as a short-pulse amplifier at 35 GHz, has demonstrated linear growth rates of 1.2 dB\\/cm, total gain of 50 dB, and coherent emission of 17 MW, corresponding to an experimental efficiency of greater than 3%.

  17. High-gain Cerenkov free-electron laser at far infrared wavelengths

    Microsoft Academic Search

    E. P. Garate; C. H. Shaughnessy; J. E. Walsh

    1987-01-01

    The small-signal gain is derived for a Cernekov free-electron laser operating in the collective beam limit. The device consists of two dielectrically lined parallel plates driven by a cold, relativistic electron beam. The dependence of the output wavelength on the resonator parameters and the electron beam energy is examined with particular attention devoted to device operation in the far infrared

  18. The Linguistic Gains and Acculturation of American High School Students on Exchange Programs in Germany

    ERIC Educational Resources Information Center

    Lovitt, Ashli

    2013-01-01

    There has been a sharp rise in study abroad participation over the last few decades (Institute for International Education, 2011), which can largely be explained by the rise of short-term study abroad programs. While there is much to be gained from participation in such programs, mid-length and year programs may offer the greatest benefits for…

  19. Effect of high dietary copper on weight gain and neuropeptide Y level in the hypothalamus of pigs.

    PubMed

    Li, Jiakui; Yan, Lianyu; Zheng, Xin; Liu, Guowen; Zhang, Naisheng; Wang, Zhe

    2008-01-01

    An experiment was performed to examine the effect of dietary copper supplementation on weight gain, neuropeptide Y (NPY) concentration and NPY mRNA expression level in the hypothalamus of pigs. Forty-five crossbred pigs were randomly assigned to three groups of 15 pigs, each comprising five replicates of 3 animals. Pigs were allocated to diets that contained 10mg/kg (as a control), 125 and 250 mg/kg copper as CuSO4. Live weight gain and feed conversion efficiency was determined at the end of the experiment and five pigs, selected at random from each group, were slaughtered and the hypothalami collected for determination of NPY concentration and NPY mRNA expression level. The results showed that average daily gain (ADG) and average daily feed intake (ADFI) were higher and feed:gain (F:G) ratio was lower in pigs fed the diets with 125 and 250 mg/kg copper (P<0.05), respectively, than in pigs fed a diet with 10 mg/kg copper, but that there was no statistically significant difference in growth performance between animals of the 125 mg/kg and the 250 mg/kg copper groups. Furthermore, pigs fed diets with 125 and 250 mg/kg copper had higher NPY concentrations and NPY mRNA expression levels in their hypothalamus than control animals. The data indicated that 125 and 250 mg/kg copper gave similar responses in terms of weight gain, whilst high dietary copper could enhance NPY concentration and NPY mRNA expression level in the hypothalamus of pigs. High dietary copper appears to increase feed intake and promote weight gain by enhancing NPY concentration and NPY mRNA expression level in the hypothalamus of pigs. PMID:18319138

  20. Novel design of inherently gain-flattened discrete highly nonlinear photonic crystal fiber Raman amplifier and dispersion compensation using a single pump in C-band

    Microsoft Academic Search

    Shailendra K. Varshney; Takeshi Fujisawa; Kunimasa Saitoh; Masanori Koshiba

    2005-01-01

    In this paper, we report, for the first time, an inherently gain-flattened discrete highly nonlinear photonic crystal fiber (HNPCF) Raman amplifier (HNPCF-RA) design which shows 13.7 dB of net gain (with +\\/-0.85-dB gain ripple) over 28-nm bandwidth. The wavelength dependent leakage loss property of HNPCF is used to flatten the Raman gain of the amplifier module. The PCF structural design

  1. Spontaneous pneumomediastinum in an 18-year-old black Sudanese high school student.

    PubMed

    Okereke, U N; Weber, B E; Israel, R H

    1999-06-01

    Spontaneous pneumomediastinum (SPM) is defined as pneumomediastinum in the absence of an underlying lung disease. It is the second most common cause of chest pain in young, healthy individuals (< 30 years) necessitating hospital visits. It is surpassed in frequency in this setting only by spontaneous pneumothorax. These two conditions may coexist in 18% of patients. The incidence of spontaneous pneumomediastinum varies in different communities and generally is relatively uncommon. Inhalational drug use (cocaine and cannabis) have been associated with a significant number of cases, although cases with no apparent etiologic or incriminating factors are well recognized. Also its recurrence, though uncommon, is worthy of note. It is a benign clinical condition with diverse clinical presentations. Physicians' knowledge of the presentation, treatment, and prognosis of SPM will guard against the need for expensive radiologic and laboratory tests. The differential diagnosis of chest pain, shortness of breath, and dysphagia include cardiac, pulmonary, and esophageal diseases. The tendency to pursue these entities may lead to laboratory investigations such as electrocardiograms, arterial blood gases, ventilation/perfusion scans, and contrast radiographic studies of the esophagus. PMID:10388262

  2. High-resolution genomic profiling reveals gain of chromosome 14 as a predictor of poor outcome in ileal carcinoids.

    PubMed

    Andersson, Ellinor; Swärd, Christina; Stenman, Göran; Ahlman, Håkan; Nilsson, Ola

    2009-09-01

    Ileal carcinoids are malignant neuroendocrine tumours of the small intestine. The aim of this study was to obtain a high-resolution genomic profile of ileal carcinoids in order to define genetic changes important for tumour initiation, progression and survival. Forty-three patients with ileal carcinoids were investigated by high-resolution array-based comparative genomic hybridization. The average number of copy number alterations (CNAs) per tumour was 7.1 (range 1-22), with losses being more common than gains (ratio 1.4). The most frequent CNA was loss of chromosome 18 (74%). Other frequent CNAs were gain of chromosome 4, 5, 14 and 20, and loss of 11q22.1-q22.2, 11q22.3-q23.1 and 11q23.3, and loss of 16q12.2-q22.1 and 16q23.2-qter. Two distinct patterns of CNAs were found; the majority of tumours was characterized by loss of chromosome 18 while a subgroup of tumours had intact chromosome 18, but gain of chromosome 14. Survival analysis, using a series of Poisson regressions including recurrent CNAs, demonstrated that gain of chromosome 14 was a strong predictor of poor survival. In conclusion, high-resolution profiling demonstrated two separate patterns of CNAs in ileal carcinoids. The majority of tumours showed loss of chromosome 18, which most likely represents a primary event in the development and pathogenesis of tumours. A different genetic pathway is operative in a subgroup of tumours; this is characterized by gain of chromosome 14 and is strongly associated with poor prognosis. Predictive fluorescence in situ hybridization analysis of chromosome 14 status in patients with ileal carcinoids is suggested. PMID:19458023

  3. A numerical algorithm for optimal feedback gains in high dimensional linear quadratic regulator problems

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Ito, K.

    1991-01-01

    A hybrid method for computing the feedback gains in linear quadratic regulator problem is proposed. The method, which combines use of a Chandrasekhar type system with an iteration of the Newton-Kleinman form with variable acceleration parameter Smith schemes, is formulated to efficiently compute directly the feedback gains rather than solutions of an associated Riccati equation. The hybrid method is particularly appropriate when used with large dimensional systems such as those arising in approximating infinite-dimensional (distributed parameter) control systems (e.g., those governed by delay-differential and partial differential equations). Computational advantages of the proposed algorithm over the standard eigenvector (Potter, Laub-Schur) based techniques are discussed, and numerical evidence of the efficacy of these ideas is presented.

  4. Design of a high gain microstrip antenna array at Ku-band

    Microsoft Academic Search

    Hongqi Xiang; Xing Jiang

    2008-01-01

    Aperture coupling feed and double-layer microstrip patch structure are applied to design microstrip antenna element, 64 elements and 256 elements microstrip antenna array. Parallel feed and T-junction type power divider are used to design antenna array. The measured results of subarray antennas show that the operational bandwidth (VSWR les 1.5) is 1.32 GHz and the gain is not less than

  5. Real-time gain tuning of PI controllers for high-performance PMSM drives

    Microsoft Academic Search

    Marco Tursini; Francesco Parasiliti; Daqing Zhang

    2002-01-01

    In this paper, a new and practical real-time gain-tuning method for proportional plus integral (PI) controllers has been formulated and implemented, using the speed control of a permanent-magnet synchronous motor drive system as a testbed. While the novel strategy enhances the performance of traditional PI controller greatly and proves to be a completely model-free approach, it also preserves the simple

  6. A leaky-wave analysis of the high-gain printed antenna configuration

    Microsoft Academic Search

    David R. Jackson; Arthur A. Oliner

    1988-01-01

    A leaky-wave analysis is used to explain the narrow-beam resonance-gain phenomenon, in which narrow beams may be produced from a printed antenna element in a substrate-superstrate geometry. It is demonstrated that the phenomenon is attributable to the presence of both transverse electric and transverse magnetic-mode leaky waves that are excited on the structure. Asymptotic formulas for the leaky wave are

  7. Suppression of parasitics and pencil beams in the high-gain National Ignition Facility multipass preamplifier

    Microsoft Academic Search

    Bryan D. Moran; C. Brent Dane; John K. Crane; Mikael D. Martinez; Frank A. Penko; Lloyd A. Hackel

    1998-01-01

    The multi-pass amplifier (MPA) is the last subsystem of the NIF preamplifier, which feeds the main amplification stages of the NIF beamline. The MPA is based on a flashlamp pumped 5-cm diameter by 48 cm long Nd:glass rod amplifier operated at a single pass small signal gain of 15 to 17. The MPA is an off-axis multi-pass image relayed system,

  8. Master-Oscillator-Power-Amplifier (MOPA) Laser Sources Used as Drive Lasers for Photoinjectors for High-Gain, Free Electron Lasers (FELs)

    E-print Network

    Anlage, Steven

    Master-Oscillator-Power-Amplifier (MOPA) Laser Sources Used as Drive Lasers for Photoinjectors for High-Gain, Free Electron Lasers (FELs) By David Leonard Demske Scholarly paper submitted In partial Milchberg #12;- 1 - Abstract The realization of extremely high gain, and high power in Free Electron Lasers

  9. A multifunctional switched-capacitor programmable gain amplifier for high-definition video analog front-ends

    NASA Astrophysics Data System (ADS)

    Hong, Zhang; Jie, Zhang; Mudan, Zhang; Xue, Li; Jun, Cheng

    2015-03-01

    A multifunctional programmable gain amplifier (PGA) that provides gain and offset adjusting abilities for high-definition video analog front-ends (AFE) is presented. With a switched-capacitor structure, the PGA also acts as a sample and holder of the analog-to-digital converter (ADC) in the AFE to reduce the power consumption and chip area of the whole AFE. Furthermore, the PGA converts the single-ended video signal into differential signal for the following ADC to reject common-mode noise and interferences. The 9-bit digital-to-analog converter (DAC) for gain and offset adjusting is embedded into the switched capacitor networks of the PGA. A video AFE integrated circuit based on the proposed PGA is fabricated in a 0.18-?m process. Simulation and measurement results show that the PGA achieves a gain control range of 0.90 to 2.34 and an offset control range of ?220 to 220 mV while consuming 10.1 mA from a 1.8 V power supply. Project supported by the National Natural Science Foundation of China (No. 61106027), and the Science and Technology Project of Shanxi Province (No. 2014K05-14).

  10. Sustained mild hypergravity reduces spontaneous cardiac baroreflex sensitivity.

    PubMed

    Yanagida, Ryo; Ogawa, Yojiro; Ueda, Kaname; Aoki, Ken; Iwasaki, Ken-ichi

    2014-10-01

    Head-to-foot gravitational force >1G (+Gz hypergravity) augments venous pooling in the lower body and reduces central blood volume during exposure, compared with 1Gz. Central hypovolemia has been reported to reduce spontaneous cardiac baroreflex sensitivity. However, no investigations have examined spontaneous cardiac baroreflex sensitivity during exposure to sustained mild +Gz hypergravity. We therefore hypothesized that mild +Gz hypergravity would reduce spontaneous cardiac baroreflex sensitivity, compared with 1Gz. To test this hypothesis, we examined spontaneous cardiac baroreflex sensitivity in 16 healthy men during exposure to mild +Gz hypergravity using a short-arm centrifuge. Beat-to-beat arterial blood pressure (tonometry) and R-R interval (electrocardiography) were obtained during 1Gz and 1.5Gz exposures. Spontaneous cardiac baroreflex sensitivity was assessed by sequence slope and transfer function gain. Stroke volume was calculated from the arterial pressure waveform using a three-element model. All indices of spontaneous cardiac baroreflex sensitivity decreased significantly (up slope: 18.6±2.3?12.7±1.6ms/mmHg, P<0.001; down slope: 19.0±2.5?13.2±1.3ms/mmHg, P=0.002; transfer function gain in low frequency: 14.4±2.2?10.1±1.1ms/mmHg, P=0.004; transfer function gain in high frequency: 22.2±7.5?12.4±3.5ms/mmHg, P<0.001). Stroke volume decreased significantly (88±5?80±6ml, P=0.025). Moreover, although systolic arterial pressure variability increased, R-R interval variability did not increase. These results suggest that even mild +Gz hypergravity reduces spontaneous cardiac baroreflex sensitivity, increasing the risk of cardiovascular disturbance during the exposure. PMID:25156804

  11. All-solid-state, ultraviolet, high power laser system using Ce:LiCAF as a gain medium

    Microsoft Academic Search

    Nobuhiko Sarukura; Shingo Ono; Hidetoshi Murakami; Alex Quema; Elmer Estacio; Tsuguo Fukuda

    2006-01-01

    High peak-power, femtosecond, ultraviolet (UV) lasers have attracted new interest. Chirped pulse amplification (CPA) in the UV region has been demonstrated using Ce:LiCaAlF6 (Ce:LiCAF) crystal as the gain medium. The peak power of the amplified and compressed pulse (115 fs) reached 30 GW at 290 nm. To increase the peak power to the terawatt (TW) level, further pulse compression is

  12. Level dependent signal flow in the light pupil reflex. III. Phase velocity in high gain instability oscillations.

    PubMed

    Myers, G A; Stark, L

    1993-01-01

    The pupil can be excited to sustained oscillations under high gain feedback conditions. The period of these oscillations (cycle time) is reduced by increased average light level by an amount commensurate with reductions in phase lag reported in the companion paper (Myers et al. 1991b). A mathematical model of this phenomenon is used to unify and clarify experimental data presented here and in the literature. PMID:8452893

  13. Ultrafast nonlinearities and gain dynamics in high-power semiconductor amplifiers

    Microsoft Academic Search

    Ali R. Motamedi; Jason J. Plant; Joseph P. Donnelly; Paul W. Juodawlkis; Erich P. Ippen

    2008-01-01

    The limits imposed by two-photon absorption and free-carrier absorption on the gain and output powers of an InGaAsP?InP slab-coupled optical waveguide amplifier with a confinement factor of ?=0.5% were studied. The two-photon absorption coefficient and the induced free-carrier absorption cross section were measured to be 65 cm?GW and 7×10?17 cm2, respectively. The effects of two-photon absorption begin to limit the

  14. Ultrafast nonlinearities and gain dynamics in high-power semiconductor amplifiers

    Microsoft Academic Search

    Ali R. Motamedi; Jason J. Plant; Joseph P. Donnelly; Paul W. Juodawlkis; Erich P. Ippen

    2008-01-01

    The limits imposed by two-photon absorption and free-carrier absorption on the gain and output powers of an InGaAsP\\/InP slab-coupled optical waveguide amplifier with a confinement factor of Gamma=0.5% were studied. The two-photon absorption coefficient and the induced free-carrier absorption cross section were measured to be 65 cm\\/GW and 7×10-17 cm2, respectively. The effects of two-photon absorption begin to limit the

  15. High-gain and low-excess noise near-infrared single-photon avalanche detector arrays

    NASA Astrophysics Data System (ADS)

    Linga, Krishna; Yevtukhov, Yuriy; Liang, Bing

    2010-04-01

    We have designed and developed a new family of photodetectors and arrays with Internal Discrete Amplification (IDA) mechanism for the realization of very high gain and low excess noise factor in the visible and near infrared spectral regions. These devices surpass many limitations of the Single Photon Avalanche Photodetectors such as ultra low excess noise factor, very high gain, lower reset time (< 200 ns). These devices are very simple to operate in the non-gated mode under a constant dc bias voltage. Because of its unique characteristics of self-quenching and self-recovery, no external quenching circuit is needed. This unique feature of self quenching and self-recovery makes it simple to less complex readout integrated circuit to realize large format detector arrays. In this paper, we present the discrete amplification design approach used for the development of self reset, high gain photodetector arrays in the near infrared wavelength region. The demonstrated device performance far exceeds any available solid state Photodetectors in the near infrared wavelength range. These devices are ideal for researchers in the field of spectroscopy, industrial and scientific instrumentation, Ladar, quantum cryptography, night vision and other military, defense and aerospace applications.

  16. High-Gain, Direct-Drive Foam Target Designs for the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Collins, T. J. B.; Skupsky, S.; Goncharov, V. N.; Betti, R.; McKenty, P. W.; Radha, P. B.

    2002-11-01

    Previous direct-drive targets designed for the National Ignition Facility achieved a 1-D gain of 45 using a pure cryogenic DT shell with fuel set on an ? = 3 adiabat by the foot pulse. One-dimensional calculations indicate that a gain of at least 100 may be achieved through the use of an outer layer of foam wetted by cryogenic DT [CH(DT)20]. The presence of higher-Z ions (C) in the foam increases the absorbed energy, allowing the shell to contain more fuel. The ratio of bubble to shell thickness at the end of the acceleration phase, as calculated by a postprocessor to 1-D simulations, is approximately 0.1, as opposed to 0.6 for the all-DT design. Stability is increased in this design by use of an intensity spike at the start of the foot pulse. This spike produces a shaped adiabat, low in the inner fuel layers and higher in the outer layers, resulting in greater ablative stabilization (invited talk by V. N. Goncharov, this conference). This spike [as reported previously in T. J. B. Collins and S. Skupsky, Phys. Plasmas 9, 275 (2002)] also serves to reduce the magnitude of laser imprint. We will present 2-D DRACO simulations that explore the stability and performance of this design. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  17. Long-Term Reduction of High Blood Pressure by Angiotensin II DNA Vaccine in Spontaneously Hypertensive Rats.

    PubMed

    Koriyama, Hiroshi; Nakagami, Hironori; Nakagami, Futoshi; Osako, Mariana Kiomy; Kyutoku, Mariko; Shimamura, Munehisa; Kurinami, Hitomi; Katsuya, Tomohiro; Rakugi, Hiromi; Morishita, Ryuichi

    2015-07-01

    Recent research on vaccination has extended its scope from infectious diseases to chronic diseases, including Alzheimer disease, dyslipidemia, and hypertension. The aim of this study was to design DNA vaccines for high blood pressure and eventually develop human vaccine therapy to treat hypertension. Plasmid vector encoding hepatitis B core-angiotensin II (Ang II) fusion protein was injected into spontaneously hypertensive rats using needleless injection system. Anti-Ang II antibody was successfully produced in hepatitis B core-Ang II group, and antibody response against Ang II was sustained for at least 6 months. Systolic blood pressure was consistently lower in hepatitis B core-Ang II group after immunization, whereas blood pressure reduction was continued for at least 6 months. Perivascular fibrosis in heart tissue was also significantly decreased in hepatitis B core-Ang II group. Survival rate was significantly improved in hepatitis B core-Ang II group. This study demonstrated that Ang II DNA vaccine to spontaneously hypertensive rats significantly lowered high blood pressure for at least 6 months. In addition, Ang II DNA vaccines induced an adequate humoral immune response while avoiding the activation of self-reactive T cells, assessed by ELISPOT assay. Future development of DNA vaccine to treat hypertension may provide a new therapeutic option to treat hypertension. PMID:26015450

  18. Spontaneous formation of graphene-like stripes on high-index diamond C(331) surface.

    PubMed

    Xu, Maojie; Zhang, Yaozhong; Zhang, Jing; Lu, Jiyun; Qian, Bingjian; Lu, Dejiong; Zhang, Yafei; Wang, Liang; Chen, Xiaoshuang; Shigekawa, Hidemi

    2012-01-01

    We employ first-principles density functional theory calculations to study the surface reconstruction, energetic stability, and electronic structure of diamond C(331) surface. Spontaneous formation of graphene-like stripes on the reconstructed surface is found to occur as the surface terrace C atoms transform from sp3 to sp2 hybridization upon structural relaxation. The comparison of the calculated absolute surface energies of C(331), C(111), and C(110) surfaces demonstrates the energetic stability of the graphitic-like C(331) surface. Local density of electronic states analysis reveals the occurrence of localized electronic states near the Fermi level, which may have a significant impact on the surface conductivity. PMID:22898095

  19. Driving high-gain shock-ignited inertial confinement fusion targets by green laser light

    SciTech Connect

    Atzeni, Stefano; Marocchino, Alberto; Schiavi, Angelo [Dipartimento SBAI, Universita di Roma 'La Sapienza' and CNISM, Via A. Scarpa 14-16, I-00161 Roma (Italy)

    2012-09-15

    Standard direct-drive inertial confinement fusion requires UV light irradiation in order to achieve ignition at total laser energy of the order of 1 MJ. The shock-ignition approach opens up the possibility of igniting fusion targets using green light by reducing the implosion velocity and laser-driven ablation pressure. An analytical model is derived, allowing to rescale UV-driven targets to green light. Gain in the range 100-200 is obtained for total laser energy in the range 1.5-3 MJ. With respect to the original UV design, the rescaled targets are less sensitive to irradiation asymmetries and hydrodynamic instabilities, while operating in the same laser-plasma interaction regime.

  20. Direct amplification of a nanosecond laser diode in a high gain diode-pumped Nd:YVO? amplifier.

    PubMed

    Délen, Xavier; Balembois, François; Georges, Patrick

    2014-02-15

    We demonstrate that Nd:YVO? can efficiently amplify a nanosecond laser diode in a very simple double-pass configuration. Based on longitudinal pumping with a high brightness fiber-coupled laser diode at 808 nm (60 W, 100 ?m, 0.22 NA) and a low Nd-doped (0.2%) temperature controlled Nd:YVO? we achieved an optical gain of 62 dB with very low (<2%) parasitic laser emission and an average output power of 10 W. At 15 kHz, we observed a strong gain saturation dynamic resulting in a pulse duration reduction from 100 to 3.5 ns. This effect enhances the peak power by a factor of 18 (130 kW) with an energy of 620 ?J. PMID:24562261

  1. Eigenmode analysis of a high-gain free-electron laser based on a transverse gradient undulator

    NASA Astrophysics Data System (ADS)

    Baxevanis, Panagiotis; Huang, Zhirong; Ruth, Ronald; Schroeder, Carl B.

    2015-01-01

    The use of a transverse gradient undulator (TGU) is viewed as an attractive option for free-electron lasers (FELs) driven by beams with a large energy spread. By suitably dispersing the electron beam and tilting the undulator poles, the energy spread effect can be substantially mitigated. However, adding the dispersion typically leads to electron beams with large aspect ratios. As a result, the presence of higher-order modes in the FEL radiation can become significant. To investigate this effect, we study the eigenmode properties of a TGU-based, high-gain FEL, using both an analytically-solvable model and a variational technique. Our analysis, which includes the fundamental and the higher-order FEL eigenmodes, can provide an estimate of the mode content for the output radiation. This formalism also enables us to study the trade-off between FEL gain and transverse coherence. Numerical results are presented for a representative soft X-ray, TGU FEL example.

  2. A Novel SWIR Detector with an Ultra-high Internal Gain and Negligible Excess Noise

    E-print Network

    Mohseni, Hooman

    Ugmented Sensor (FOCUS). It utilizes very high charge compression into a nano-injector, and subsequent carrier have a very high noise as well. Here we present the recent results from our novel FOcalized Carrier a injection to achieve high quantum efficiency and high sensitivity at short infrared at room temperature. We

  3. Dual gate photo-thin film transistor with high photoconductive gain for high reliability, and low noise flat panel transparent imager

    Microsoft Academic Search

    Sanghun Jeon; Seung-Eon Ahn; Ihun Song; Yongwoo Jeon; Young Kim; Sangwook Kim; Hyunsik Choi; Hojung Kim; Eunha Lee; Sungsik Lee; Arokia Nathan; John Robertson; Changjung Kim; U-In Chung; Inkyung Yoo; Kinam Kim

    2011-01-01

    In this presentation, we report excellent electrical and optical characteristics of a dual gate photo thin film transistor (TFT) with bi-layer oxide channel, which was designed to provide virgin threshold voltage (VT) control, improve the negative bias illumination temperature stress (NBITS) reliability, and offer high photoconductive gain. In order to address the photo-sensitivity of phototransistor for the incoming light, top

  4. Current gain collapse in microwave multifinger heterojunction bipolar transistors operated at very high power densities

    Microsoft Academic Search

    William Liu; Steve Nelson; Darrell G. Hill; Ali Khatibzadeh

    1993-01-01

    The rapid development of heterojunction bipolar transistor (HBT) technologies has led to the demonstration of high power single-chip microwave amplifiers. Because HBTs are operated at high power densities, the ultimate limits on the performance of HBTs are imposed by thermal considerations. The authors address a thermal phenomenon observed when a multifinger power HBT is operating at high power densities. This

  5. Very High Energy Gain at the Neptune Inverse Free Electron Laser Experiment

    SciTech Connect

    Musumeci, P.; Boucher, S.; Doyuran, A.; England, R. J.; Pellegrini, C.; Rosenzweig, J. B.; Travish, G.; Yoder, R. [Neptune Laboratory Department of Physics and Astronomy, University of California, Los Angeles, CA, 90095 (United States); Tochitsky, S.Ya.; Joshi, C.; Ralph, J.; Sung, C. [Department of Electrical Engineering. University of California, Los Angeles, CA, 90095 (United States); Tolmachev, S.; Varfolomeev, A.; Varfolomeev, A. Jr.; Yarovoi, T. [RRCKI, Moscow (Russian Federation)

    2004-12-07

    We report the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected in an undulator strongly tapered in period and field amplitude. The IFEL driver is a CO2 10.6 {mu}m laser with power larger than 400 GW. The Rayleigh range of the laser, {approx} 1.8 cm, is much shorter than the undulator length so that the interaction is diffraction dominated. A few per cent of the injected particles are trapped in a stable accelerating bucket. Electrons with energies up to 35 MeV are measured by a magnetic spectrometer. Three-dimensional simulations, in good agreement with the measured electron energy spectrum, indicate that most of the acceleration occurs in the first 25 cm of the undulator, corresponding to an energy gradient larger than 70 MeV/m. The measured energy spectrum also indicates that higher harmonic Inverse Free Electron Laser interaction takes place in the second section of the undulator.

  6. A megajoule class krypton fluoride amplifier for single shot, high gain ICF application

    SciTech Connect

    Rose, E.; Hanson, D.; Krohn, B.; McLeod, J.; Kang, M.

    1988-01-01

    A design study is underway to define the optimal architecture for a KrF laser system which will deliver 10 MJ of 248-nm light to an ICF target. We present one approach which incorporates final power amplifiers in the megajoule class, achieving 10 MJ with four final amplifiers. Each double-pass laser amplifier employs two-sided electron-beam pumping of the laser gas medium. Details of the design are based on a Monte-Carlo electron-beam deposition code, a one-dimensional, time-dependent kinetics code, and pulsed power circuit modeling. Linear dimensions of the amplifier's extracted gain volume are 6.25 m in height and length and 5.12 m in width. Each amplifier handles 160 angularly multiplexed laser channels. The one-amagat, krypton-rich laser medium is e-beam pumped at 60-kW cm/sup /minus/3/ (4-MA at3.3-MV) over the 2-microsecond duration of the laser beam pulse train. 5 refs., 4 figs.

  7. 150 KGate general-purpose high-coding-gain TCM VLSIs for high-speed multi-level QAM systems

    Microsoft Academic Search

    Satoru AIKAWA; Yasuhisa NAKAMURA; Hitoshi TAKANASHI

    1990-01-01

    Multilevel trellis-coded QAM (quadrature amplitude modulation) VLSIs were designed and developed. These VLSIs realize a coding gain of 7.9 dB with SPORT-256 QAM. The VLSIs contain an encoder, a mapper, and a decoder for trellis-coded 16, 32, 64, 128, and 256 QAM utilizing general mapping. The VLSIs also function as a phase ambiguity rejection circuit for a recovered carrier and

  8. A high speed and high gain CMOS receiver chip for a pulsed time-of-flight laser rangefinder

    NASA Astrophysics Data System (ADS)

    Yu, Jin-jin; Deng, Ruo-han; Yuan, Hong-hui; Chen, Yong-ping

    2011-06-01

    An integrated receiver channel for a pulsed time-of-flight (TOF) laser rangefinder has been designed. Pulsed TOF laser range finding devices using a laser diode transmitter can achieve millimeter-level distance measurement accuracy in a measurement range of several tens of meters to non-cooperative targets. The amplifier exploits the regulated cascade (RGC) configuration as the input-stage, thus achieving as large effective input trans-conductance as that of Si Bipolar or GaAs MESFET. The RGC input configuration isolates the input parasitic capacitance including photodiode capacitance from the bandwidth determination better than common-gate TIA. To enlarge the bandwidth, inductive peaking technology has been adopted. An active inductor (MOS-L) is used instead of spiral inductor in CMOS process. An R-2R resistor ladder is inserting between per-amplifier and post-amplifier as the variable attenuator for digital gain control purpose. The gain-bandwidth of a basic differential pair with resistive load is not large enough for broad band operation. A circuit solution to improve both gain and bandwidth of an amplifying stage is proposed. Traditional and modified Cherry-Hooper amplifiers are discussed and the cascading of several stages to constitute the post-amplifier is designed. The fully integrated one-chip solution is designed with Cadence IC design platform. The simulation result shows the bandwidth of the trans-impedance amplifier is 215MHz with the presence of a 2pF input capacitor and 5pF load capacitor. And the maximum trans-impedance gain is 136dB. The walk error is less than 1ns in 1:1000 dynamic range. The responsive time is less than 2.2ns.

  9. Gain high-quality colloidal quantum dots directly from natural minerals.

    PubMed

    Wu, Wen-Tian; Liu, Hui; Dong, Chao; Zheng, Wen-Jing; Han, Li-Li; Li, Lan; Qiao, Shi-Zhang; Yang, Jing; Du, Xi-Wen

    2015-03-01

    Green and simple synthesis of high-quality colloidal quantum dots (CQDs) is of great importance and highly anticipated yet not fully implemented. Herein, we achieve the direct conversion of natural minerals to highly uniform, crystalline lead sulfide CQDs based on laser irradiation in liquid. The trivial fragmentation of mineral particles by an intense nanosecond laser was found to create a localized high degree of monomer supersaturation in oleic acid, initiating the LaMer growth of uniform CQDs. The photoconductive device made of these CQDs exhibits a competitive temporal response of photocurrent with those highly sensitive photodetectors based on PbS CQDs reported in the literature. Our synthesis strategy paves the way for the most environmentally friendly and convenient mass production of high-quality uniform CQDs. PMID:25689447

  10. Traveling-wave photodetectors with high power-bandwidth and gain-bandwidth product performance

    Microsoft Academic Search

    Daniel Lasaosa; Jin-Wei Shi; Donato Pasquariello; Kian-Giap Gan; Ming-Chun Tien; Hsu-Hao Chang; Shi-Wei Chu; Chi-Kuang Sun; Yi-Jen Chiu; John E. Bowers

    2004-01-01

    Traveling-wave photodetectors (TWPDs) are an attractive way to simultaneously maximize external quantum efficiency, electrical bandwidth, and maximum unsaturated output power. We review recent advances in TWPDs. Record high-peak output voltage together with ultrahigh-speed performance has been observed in low-temperature-grown GaAs (LTG-GaAs)-based metal-semiconductor-metal TWPDs at the wavelengths of 800 and 1300 nm. An approach to simultaneously obtain high bandwidth and high

  11. Gain enhancement in L-band EDFA through a double-pass technique

    Microsoft Academic Search

    S. W. Harun; P. Poopalan; H. Ahmad

    2002-01-01

    An improvement of gain in the long-wavelength band (L-band) is observed by double passing the forward amplified spontaneous emission and signal in the erbium-doped fiber (EDF) using a circulator, unlike conventional single pass amplification. A gain enhancement as high as 11 dB is obtained for a 1570-nm signal with an input power of -20 dBm at 98 mW of pump

  12. High gain, low noise, fully complementary logic inverter based on bi-layer WSe{sub 2} field effect transistors

    SciTech Connect

    Das, Saptarshi; Roelofs, Andreas [Center for Nanoscale Material, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Dubey, Madan [U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States)

    2014-08-25

    In this article, first, we show that by contact work function engineering, electrostatic doping and proper scaling of both the oxide thickness and the flake thickness, high performance p- and n-type WSe{sub 2} field effect transistors (FETs) can be realized. We report record high drive current of 98??A/?m for the electron conduction and 110 ?A/?m for the hole conduction in Schottky barrier WSe{sub 2} FETs. Then, we combine high performance WSe{sub 2} PFET with WSe{sub 2} NFET in double gated transistor geometry to demonstrate a fully complementary logic inverter. We also show that by adjusting the threshold voltages for the NFET and the PFET, the gain and the noise margin of the inverter can be significantly enhanced. The maximum gain of our chemical doping free WSe{sub 2} inverter was found to be ?25 and the noise margin was close to its ideal value of ?2.5?V for a supply voltage of V{sub DD}?=?5.0?V.

  13. Full characterization of the amplified spontaneous emission from a diode-pumped high-power laser system.

    PubMed

    Keppler, S; Hornung, M; Bödefeld, R; Sävert, A; Liebetrau, H; Hein, J; Kaluza, M C

    2014-05-01

    We present the first complete temporal and spatial characterization of the amplified spontaneous emission (ASE) of laser radiation generated by a diode-pumped high-power laser system. The ASE of the different amplifiers was measured independently from the main pulse and was characterized within a time window of -10ms ? t ? 10ms and an accuracy of up to 15fs around the main pulse. Furthermore, the focusability and the energy of the ASE from each amplifier was measured after recompression. Using our analysis method, the laser components, which need to be optimized for a further improvement of the laser contrast, can be identified. This will be essential for laser-matter interaction experiments requiring a minimized ASE intensity or fluence. PMID:24921820

  14. Role of Spontaneous Current Oscillations during High-Efficiency Electrotransformation of Thermophilic Anaerobes

    PubMed Central

    Tyurin, Michael V.; Sullivan, Charles R.; Lynd, Lee R.

    2005-01-01

    Current oscillations at about 24 MHz were observed during electrotransformation (ET) of the thermophilic anaerobes Clostridium thermocellum ATCC 27405, C. thermocellum DSM 1313, and Thermoanaerobacterium saccharolyticum YS 485, using a pulse gated by a square signal generated by a custom generator. In experiments in which only the field strength was varied, all three of these strains resulted in a one-to-one correspondence between the appearance of current oscillations and successful ET. Oscillations accompanied ET of both C. thermocellum strains only at field strengths of ?12 kV/cm, and ET was only observed above the same threshold. Similarly, for T. saccharolyticum, oscillations were only observed at field strengths of ?10 kV/cm, and ET was only observed above the same threshold. When a passive electrical filter consisting of an inductor and resistor in parallel was added to the system to prevent the development of oscillations, ET efficiencies were reduced dramatically for all three strains at all field strengths tested. The maximum tested field strength, 25 kV/cm, resulted in the maximum measured transformation efficiency for all three strains. At this field strength, the efficiency of ET in the absence of oscillations was decreased compared to that observed in the presence of oscillations by 500-fold for C. thermocellum ATCC 27405, 2,500-fold for C. thermocellum DSM 1313, and 280-fold for T. saccharolyticum. Controls using the same apparatus with Escherichia coli cells or a resistor with a value representative of the direct current resistance of typical cell samples did not develop oscillations, and ET efficiencies obtained with E. coli were the same with or without the electrical filter included in the pulse generator circuit. The results are interpreted to indicate that spontaneously arising oscillations have a large beneficial effect on transformation efficiency in the system employed here and that the development of oscillations in this system is affected by the cell species present. PMID:16332787

  15. 2296 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 60, NO. 7, JULY 2013 Dual-Carrier High-Gain Low-Noise Superlattice

    E-print Network

    Hayat, Majeed M.

    2296 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 60, NO. 7, JULY 2013 Dual-Carrier High-Gain Low with alternate carrier multiplication nanometer regions, placed next to a wider electron multiplication region, to create dual- carrier feedback systems, are proposed. Gain and excess noise factor of these structures

  16. Multiple, high-gain, common-emitter operational amplifiers using super-ß lateral transistors

    Microsoft Academic Search

    T. Frederiksen; W. Davis; D. Zobel

    1971-01-01

    Six independent, internally-compensated high-performance op-amps have been built on a single monolithic chip. They were designed for industrial control and automotive electronic systems which require low-cost single-supply amplifiers.

  17. Low noise and high gain-bandwidth product AlInAs avalanche photodiodes

    Microsoft Academic Search

    Anne Rouvie; Daniele Carpentier; Jean Decobert; Nadine Lagay; Frederic Pommereau; Mohand Achouche

    2008-01-01

    We demonstrate a planar junction AlInAs APD using Carbon as p-doping impurity of the charge layer allowing to achieve simultaneously a high primary sensitivity of 0.9 A\\/W, a low dark current (Idark(M=10)=17 nA at ambient temperature), a low excess noise factor (f(M=10)=3.5) and high gaintimesbandwidth product over 140 GHz.

  18. Kick and phase errors in spontaneous and amplified radiation.

    SciTech Connect

    Kim, K.-J.

    1999-08-31

    Two types of magnet errors are considered--the random phase error (RPE), in which the phase errors are evenly distributed along the magnet, and the random kick error (RKE), in which the errors in the derivative of the phase are evenly distributed. We compute the reduction in performance of both spontaneous radiation and high-gain free-electron lasers for both types of errors within the framework of 1-D free-electron laser theory.

  19. Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range

    PubMed Central

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David; Hoch, Jeffrey C.; Rovnyak, David

    2014-01-01

    Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C–13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C, 15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C–13C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

  20. High-resolution stimulated-Raman-gain spectroscopy with cavity ringdown detection

    Microsoft Academic Search

    F. K. Englich; Yabai He; B. J. Orr

    2005-01-01

    In this paper, a distinctive form of continuous-wave (cw) cavity-ringdown (CRD) spectroscopy is adopted, with a rapidly swept ringdown cavity. Preliminary high-resolution measurements of the ?band Raman spectrum of CH4 gas, to demonstrate the new SRG-CRD approach, is reported.

  1. The Role of Grades in Gaining Admission to Highly Selective Medical Schools.

    ERIC Educational Resources Information Center

    Cooke, W. D.; And Others

    1992-01-01

    A study of over 8,000 admissions of Cornell University (New York) graduates to 19 highly selective medical schools, 1982-89, found that grade point average (GPA) was extremely influential especially at 9 schools. It was concluded that applicants often receive encouragement to continue the application process despite little chance of acceptance.…

  2. A critical examination of the evidence relating high fructose corn syrup and weight gain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of high fructose corn syrup (HFCS) has increased over the past several decades in the United States while overweight and obesity rates have risen dramatically. Some scientists hypothesize that HFCS consumption has uniquely contributed to the increasing mean body mass index (BMI) of the U.S....

  3. KrF laser path to high gain ICF (inertial confinement fusion) laboratory microfusion facility

    Microsoft Academic Search

    David B. Harris; J. Al Sullivan; Joseph F. Figueiro; David C. Cartwright; Thomas E. McDonald; Allan A. Hauer; Stephen V. Coggeshall; Stephen M. Younger

    1990-01-01

    The krypton-fluoride laser has many desirable features for inertial confinement fusion. Because it is a gas laser capable of operation with high efficiency, it is the only known laser candidate capable of meeting the driver requirements for inertial fusion energy (IFE) production. Los Alamos National Laboratory has defined a program plan to develop KrF lasers for IFE production. This plan

  4. Best Practices: Campaign to Discover Successful Practices Nets Gains for High School

    ERIC Educational Resources Information Center

    Psencik, Kay; Czaplicki, Hilary J.; Houston, Tracy A.; Kopp, Debra

    2007-01-01

    Hanging in the entryway of Quakertown Community Senior High School in Quakertown, Pennsylvania, was the school vision: "Enter to Learn; Leave to Serve." The school vision statement contained the right words, but it did not inspire anyone. In many classrooms, teachers lectured from the front of the room, students sat in rows taking notes, and…

  5. Low Noise, High Gain Short-Wave Infrared Nano-Injection Photon Detectors with Low Jitter

    E-print Network

    Mohseni, Hooman

    in short wave infrared (SWIR) spectrum, particularly focusing at 1.55 m wavelength. Spanning a wide range of applications from slow imaging technologies to very high speed fiber telecommunications, SWIR contains both of detectors have been created. Common technologies for SWIR detection are InGaAs/InP based detectors (P

  6. A Study of Information Gain in High Angular Resolution Diffusion Imaging (HARDI)

    E-print Network

    Thompson, Paul

    . Zhu2 , L. Zhan3 , K. McMahon4 , G.I. de Zubicaray4 , M. Meredith4 , M. Wright4 , P.M. Thompson3 1 tissue. High- angular resolution diffusion imaging (HARDI) schemes have been em- ployed to resolve fiber estimates of the recovered fibers stabilized with around 40 directions, suggesting asymptotic but clear

  7. Characteristics of trap-filled gallium arsenide photoconductive switches used in high gain pulsed power applications

    Microsoft Academic Search

    N. E. ISLAM; E. SCHAMILOGLU; ALAN MAR; GUILLERMO M. LOUBRIEL; FRED J. ZUTAVERN; R. P. JOSHI

    2000-01-01

    The electrical properties of semi-insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle

  8. Performance of a high-efficiency 5-cm gain length supersonic chemical oxygen-iodine laser

    Microsoft Academic Search

    Tilghman L. Rittenhouse; Stephen P. Phipps; Charles A. Helms

    1999-01-01

    The Air Force Phillips Laboratory has developed a small-scale supersonic chemical oxygen-iodine laser (COIL) test stand (VertiCOIL) to rapidly evaluate emerging potential technology improvements. VertiCOIL was designed to address issues relevant to military and commercial applications such as long run time, high-efficiency operation, and compact design. VertiCOIL demonstrated an overall chemical efficiency of nearly 27%, one of the highest chemical

  9. KrF laser path to high gain ICF (inertial confinement fusion) laboratory microfusion facility

    NASA Astrophysics Data System (ADS)

    Harris, David B.; Sullivan, J. Al; Figueiro, Joseph F.; Cartwright, David C.; McDonald, Thomas E.; Hauer, Allan A.; Coggeshall, Stephen V.; Younger, Stephen M.

    1990-09-01

    The krypton-fluoride laser has many desirable features for inertial confinement fusion. Because it is a gas laser capable of operation with high efficiency, it is the only known laser candidate capable of meeting the driver requirements for inertial fusion energy (IFE) production. Los Alamos National Laboratory has defined a program plan to develop KrF lasers for IFE production. This plan develops the KrF laser and demonstrates the target performance in single-pulse facilities. A 100-kJ Laser Target Test Facility (LTTF) is proposed as the next step, to be followed by a 3 to 10-MJ Laboratory Microfusion Facility (LMF). The LTTF will resolve many target physics issues and accurately define the driver energy required for the LMF. It is also proposed that the technology development for IFE, such as the high-efficiency, high-reliability, repetitively pulsed driver, the reactor, mass production of targets, and the mechanism of injecting targets be developed in parallel with the single-pulse facilities.

  10. High-power ultralow-noise semiconductor external cavity lasers based on low-confinement optical waveguide gain media

    NASA Astrophysics Data System (ADS)

    Juodawlkis, Paul W.; Loh, William; O'Donnell, Frederick J.; Brattain, Michael A.; Plant, Jason J.

    2010-02-01

    For the past several years, we have been developing a new class of high-power, low-noise semiconductor optical gain medium based on the slab-coupled optical waveguide (SCOW) concept. The key characteristics of the SCOW design are (i) large (> 5 x 5 ?m), symmetric, fundamental-transverse-mode operation attained through a combination of coupledmode filtering and low index-contrast, (ii) very low optical confinement factor (? ~ 0.3-0.5%), and (iii) low excessoptical loss (?i ~ 0.5 cm-1). The large transverse mode and low confinement factor enables SCOW lasers (SCOWLs) and amplifiers (SCOWAs) having Watt-class output power. The low confinement factor also dictates that the waveguide length be very large (0.5-1 cm) to achieve useful gain, which provides the benefits of small ohmic and thermal resistance. In this paper, we review the operating principles and performance of the SCOW gain medium, and detail its use in 1550-nm single-frequency SCOW external cavity lasers (SCOWECLs). The SCOWECL consists of a doublepass, curved-channel InGaAlAs quantum-well SCOWA and a narrowband (2.5 GHz) fiber Bragg grating (FBG) external cavity. We investigate the impact of the cavity Q on SCOWECL performance by varying the FBG reflectivity. We show that a bench-top SCOWECL having a FBG reflectivity of R = 10% (R = 20%) has a maximum output power of 450 mW (400 mW), linewidth of 52 kHz (28 kHz), and RIN at 2-MHz offset frequency of -155 dB/Hz (-165 dB/Hz).

  11. A high calcium diet containing nonfat dry milk reduces weight gain and associated adipose tissue inflammation in diet-induced obese mice when compared to high calcium alone

    PubMed Central

    2012-01-01

    Background High dietary calcium (Ca) is reported to have anti-obesity and anti-inflammatory properties. Evidence for these properties of dietary Ca in animal models of polygenic obesity have been confounded by the inclusion of dairy food components in experimental diets; thus, effect of Ca per se could not be deciphered. Furthermore, potential anti-inflammatory actions of Ca in vivo could not be dissociated from reduced adiposity. Methods We characterized adiposity along with metabolic and inflammatory phenotypes in diet-induced obese (DIO) mice fed 1 of 3 high fat diets (45% energy) for 12 wk: control (n = 29), high-Ca (n = 30), or high-Ca + nonfat dry milk (NFDM) (n = 30). Results Mice fed high-Ca + NFDM had reduced body weight and adiposity compared to high-Ca mice (P < 0.001). Surprisingly, the high-Ca mice had increased adiposity compared to lower-Ca controls (P < 0.001). Hyperphagia and increased feed efficiency contributed to obesity development in high-Ca mice, in contrast to NFDM mice that displayed significantly reduced weight gain despite higher energy intake compared to controls (P < 0.001). mRNA markers of macrophages (e.g., CD68, CD11d) strongly correlated with body weight in all diet treatment groups, and most treatment differences in WAT inflammatory factor mRNA abundances were lost when controlling for body weight gain as a covariate. Conclusions The results indicate that high dietary Ca is not sufficient to dampen obesity-related phenotypes in DIO mice, and in fact exacerbates weight gain and hyperphagia. The data further suggest that putative anti-obesity properties of dairy emanate from food components beyond Ca. PMID:22269778

  12. High gain and high extraction efficiency from a free electron laser amplifier operating in the millimeter wave regime

    SciTech Connect

    Orzechowski, T.J.; Anderson, B.R.; Fawley, W.M.; Prosnitz, D.; Scharlemann, E.T.; Yarema, S.M.; Sessler, A.M.; Hopkins, D.B.; Paul, A.C.; Wurtele, J.S.

    1985-10-01

    Experiments at the Electron Laser Facility have generated peak microwave power of 180 MW at 35 GHz. The facility is operated as a single pass amplifier. Gain in excess of 30 dB/m has been observed up to saturation of the amplifier. For the 3 MeV, 850 Amp electron beam, the radiation corresponds to 7% energy extraction from the electron beam. Beyond saturation, the electron beam output power exhibits oscillations corresponding to the synchrotron motion of the trapped electrons in the ponderomotive well. In addition, the TE/sub 21/ and TM/sub 21/ modes have been studied and have power levels comparable to the fundamental. Third harmonic (105 GHz) radiation has been measured at power levels on the order of a few percent of the peak fundamental power.

  13. Ce3+:LiCaAlF6 crystal for high-gain or high-peak-power amplification of ultraviolet femtosecond pulses and new potential ultraviolet gain medium: Ce3+:LiSr0.8Ca 0.2AlF6

    Microsoft Academic Search

    Zhenlin Liu; Toshimasa Kozeki; Yuji Suzuki; Nobuhiko Sarukura; Kiyoshi Shimamura; Tsuguo Fukuda; Masahiro Hirano; Hideo Hosono

    2001-01-01

    To develop high-peak-power ultrashort pulse laser systems in the ultraviolet region, a large Ce3+:LiCaAlF6 (Ce:LiCAF) crystal, a tunable ultraviolet laser medium with large saturation fluence and broad gain spectrum width, was grown successfully with a diameter of more than 70 mm. To demonstrate high small signal gain, a four-pass confocal amplifier with 60 dB gain and 54 ?J output energy

  14. Laser-diode-pumped highly efficient gain-shifted thulium-doped fiber amplifier operating in the 1480-1510-nm band

    Microsoft Academic Search

    Tadashi Kasamatsu; Yutaka Yano; Takashi Ono

    2001-01-01

    We have developed a gain-shifted thulium-doped fiber amplifier (TDFA) with a high optical efficiency (29%) and a high output power (+21.5 dBm) operating in the 1480-1510-nm wavelength band by employing a novel laser diode pumping scheme of 1.4 and 1.56 ?m. The results we obtained confirm the feasibility of applying our gain-shifted TDFA to practical wavelength-division-multiplexing (WDM) networks

  15. Allowing for spontaneous breathing during high-frequency oscillation: the key for final success?

    Microsoft Academic Search

    Peter C Rimensberger

    2006-01-01

    In the present issue of Critical Care, van Heerde and colleagues describe a new technical development (a flow-demand system during high-frequency oscillation) that may have an important impact on the future use of high-frequency ventilation in children and adults. Flow compensation on patient demand seems to reduce the imposed work of breathing, may therefore increase patient comfort, and should theoretically

  16. An opto-electro-mechanical infrared photon detector with high internal gain at room temperature.

    PubMed

    Kohoutek, John; Wan, Ivy Yoke Leng; Memis, Omer Gokalp; Mohseni, Hooman

    2009-08-17

    Many applications require detectors with both high sensitivity and linearity, such as low light level imaging and quantum computing. Here we present an opto-electro-mechanical detector based on nano-injection and lateral charge compression that operates at the short infrared (SWIR) range. Electrical signal is generated by photo-induced changes in a nano-injector gap, and subsequent change of tunneling current. We present a theoretical model developed for the OEM detector, and it shows good agreement with the measured experimental results for both the mechanical and electrical properties of the device. The device shows a measured responsivity of 276 A/W, equivalent to 220 electrons per incoming photon, and an NEP of 3.53 x 10(-14) W/Hz(0.5) at room temperature. Although these results are already competing with common APDs in linear mode, we believe replacing the AFM tip with a dedicated nano-injector can improve the sensitivity significantly. PMID:19687924

  17. Consumption of a high-fat diet abrogates inhibitory effects of methylseleninic acid on spontaneous metastasis of Lewis lung carcinoma in mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We investigated the effect of dietary supplementation with selenium (Se) on spontaneous metastasis of Lewis lung carcinoma (LLC) in male C57BL/6 mice fed a high-fat diet. Mice were fed the AIN93G diet or that diet modified with 45% calories from fat supplemented with or without 2.5 mg Se/4029 kCal ...

  18. Effects of a high-fat diet on spontaneous metastasis of Lewis lung carcinoma in plasminogen activator inhibitor-1 deficient and wild-type mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We investigated the effects of plasminogen activator inhibitor-1 (PAI-1) deficiency on spontaneous metastasis of Lewis lung carcinoma (LLC) in PAI-1 deficient (PAI-1-/-) and wildtype mice (C57BL/6J background) fed the AIN93G diet or that diet modified with 45% calories from fat. The high-fat diet i...

  19. Vegetable Oils High in Phytosterols Make Erythrocytes Less Deformable and Shorten the Life Span of Stroke-Prone Spontaneously Hypertensive Rats1,2

    Microsoft Academic Search

    Walisundera M. N. Ratnayake; Mary R. L'Abbe ´; Rudi Mueller; Stephen Hayward; Louise Plouffe; Rudy Hollywood; Keith Trick

    Previous studies have shown that canola oil (CA), compared with soybean oil (SO), shortens the life span of stroke-prone spontaneously hypertensive (SHRSP) rats, a widely used model for hemorrhagic stroke. SHRSP rats are highly sensitive to dietary cholesterol manipulations because a deficiency of membrane cholesterol makes their cell membranes weak and fragile. Phytosterols, abundant in CA but not in SO,

  20. Implementing planetary meteor impact craters as high gain radio frequency dish reflector antennas

    NASA Astrophysics Data System (ADS)

    Taylor, Travis S.

    Future ventures back to the Moon, Mars, or the outer planets and natural solar system objects would benefit fiom high bandwidth communications capabilities that enable faster data transfer rates to and fiom the spacecraft. However, communication links for such missions are limited by the antenna aperture size, transceiver power, and range between the space vehicle communications system and the receiving systems on Earth. This dissertation proposes a novel approach for using naturally occurring meteor impact craters as the parabolic dish reflector for radio frequency antennas. Analysis and experimentation shows that for long radio wavelengths that meteor impact craters appear very similar in geometry to dish antennas. There are many craters on the lunar surface that fit very closely to dish geometries. Some of these craters are as large as 100 kilometers in diameter. The calculated data transmission rate achievable from such an antenna configuration is many times greater than currently available long range space communications systems. Preliminary experiments conducted using manmade craters demonstrated the possibility of the concept. A 20 m diameter crater was dug and implemented in a complex radio telescope configuration with receiver systems at multiple wavelengths. The electronic components were all inexpensive hobbyist components or homemade. The radio telescope system was successful in detecting radio signals from the Sun and from the Crab Nebula. Sidereal motion of the astronomical sources matched exactly to the time lapse of the detected signals. Further analysis suggests that this concept could be implemented in near-term missions to the Moon with currently available technology. Analysis suggests that a spacecraft orbiting the Moon at 100 km altitude could use very large craters as reflector dishes. Terrestrial based experiments using impact craters like the one in Meteor Crater, Arizona could be conducted to determine the impact of soil reflectivity, surface roughness, and feedhorn position accuracy.

  1. The Spontaneous Imbalance of an Atmospheric Vortex at High Rossby Number

    E-print Network

    Schecter, David

    at high Rossby number, due to the radiation of spiral inertia­gravity (IG) waves. The outward Rossby waves. An individual vortex Rossby wave and its IG wave emission have angular pseudomomenta of opposite sign, positive and negative, respectively. The Rossby wave therefore grows in response to pro

  2. Cooling by spontaneous decay of highly excited antihydrogen atoms in magnetic traps.

    PubMed

    Pohl, T; Sadeghpour, H R; Nagata, Y; Yamazaki, Y

    2006-11-24

    An efficient cooling mechanism of magnetically trapped, highly excited antihydrogen (H) atoms is presented. This cooling, in addition to the expected evaporative cooling, results in trapping of a large number of H atoms in the ground state. It is found that the final fraction of trapped atoms is insensitive to the initial distribution of H magnetic quantum numbers. Expressions are derived for the cooling efficiency, demonstrating that magnetic quadrupole (cusp) traps provide stronger cooling than higher order magnetic multipoles. The final temperature of H confined in a cusp trap is shown to depend as approximately 2.2T(n0)n(0)(-2/3) on the initial Rydberg level n0 and temperature T(n0). PMID:17155740

  3. Cooling by Spontaneous Decay of Highly Excited Antihydrogen Atoms in Magnetic Traps

    SciTech Connect

    Pohl, T.; Sadeghpour, H. R. [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge Massachusetts 02138 (United States); Nagata, Y.; Yamazaki, Y. [Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902 (Japan); Atomic Physics Laboratory, RIKEN, Saitama 351-0198 (Japan)

    2006-11-24

    An efficient cooling mechanism of magnetically trapped, highly excited antihydrogen (H) atoms is presented. This cooling, in addition to the expected evaporative cooling, results in trapping of a large number of H atoms in the ground state. It is found that the final fraction of trapped atoms is insensitive to the initial distribution of H magnetic quantum numbers. Expressions are derived for the cooling efficiency, demonstrating that magnetic quadrupole (cusp) traps provide stronger cooling than higher order magnetic multipoles. The final temperature of H confined in a cusp trap is shown to depend as {approx}2.2T{sub n{sub 0}}n{sub 0}{sup -2/3} on the initial Rydberg level n{sub 0} and temperature T{sub n{sub 0}}.

  4. Quantitative Analysis of Spectral Interference of Spontaneous Raman Scattering in High-Pressure Fuel-Rich H2-Air Combustion

    NASA Technical Reports Server (NTRS)

    Kojima, Jun; Nguyen, Quang-Viet

    2004-01-01

    We present a theoretical study of the spectral interferences in the spontaneous Raman scattering spectra of major combustion products in 30-atm fuel-rich hydrogen-air flames. An effective methodology is introduced to choose an appropriate line-shape model for simulating Raman spectra in high-pressure combustion environments. The Voigt profile with the additive approximation assumption was found to provide a reasonable model of the spectral line shape for the present analysis. The rotational/vibrational Raman spectra of H2, N2, and H2O were calculated using an anharmonic-oscillator model using the latest collisional broadening coefficients. The calculated spectra were validated with data obtained in a 10-atm fuel-rich H2-air flame and showed excellent agreement. Our quantitative spectral analysis for equivalence ratios ranging from 1.5 to 5.0 revealed substantial amounts of spectral cross-talk between the rotational H2 lines and the N2 O-/Q-branch; and between the vibrational H2O(0,3) line and the vibrational H2O spectrum. We also address the temperature dependence of the spectral cross-talk and extend our analysis to include a cross-talk compensation technique that removes the nterference arising from the H2 Raman spectra onto the N2, or H2O spectra.

  5. Design considerations and implementation of a programmable high-frequency continuous-time filter and variable-gain amplifier in submicrometer CMOS

    Microsoft Academic Search

    Venu Gopinathan; Maurice Tarsia; Davy Choi

    1999-01-01

    We report on an approach to designing high-speed, low-voltage programmable continuous-time filters with an embedded variable-gain amplifier (VGA). The methods we describe here are aimed at implementation in ultra-short-channel, low-voltage CMOS technologies. The seventh-order equiripple filter and VGA combination described here has a -3-dB frequency programmable from 30 to 100 MHz, gain programmable from 0 to 17 dB and 12

  6. Bifunctional star-burst amorphous molecular materials for OLEDs: achieving highly efficient solid-state luminescence and carrier transport induced by spontaneous molecular orientation.

    PubMed

    Kim, Jun Yun; Yasuda, Takuma; Yang, Yu Seok; Adachi, Chihaya

    2013-05-21

    Bifunctional star-burst amorphous molecular materials displaying both efficient solid-state luminescence and high hole-transport properties are developed in this study. A high external electroluminescence quantum efficiency up to 5.9% is attained in OLEDs employing the developed amorphous materials. It is revealed that the spontaneous horizontal orientation of these light-emitting molecules in their molecular-condensed states leads to a remarkable enhancement of the electroluminescence efficiencies and carrier-transport properties. PMID:23401305

  7. Ultrahigh-speed personal wireless communications in 60 GHz using picocell zones and high-gain direct beams

    NASA Astrophysics Data System (ADS)

    Takimoto, Yukio; Inoue, Akihiko

    1995-09-01

    This paper describes a simple and low cost transceiver for indoor wireless LAN system to be operated in 60 GHz for ultra-high speed data (e.g. 156 Mbps) transmission, along with design of system parameters such as frequency selection, radio link parameters featuring very low RF power of 10 mW suitable to MMIC performances and high gain antennas. Without using route diversity and adaptive delay equalizers making up for shadowing and multipath reflection of RF signals, new layout of hub and user stations and line-of-sight transmission scheme are adopted. In addition, partially applied radio absorber helps effectively to reduce the undesired co-channel interference signal to the neglectful level, which system is named minimum delay spread (MDS0 local area network (LAN). This paper also presents the idea of effective applying absorber on ceiling which is derived from simulation and some useful measured data of absorbing construction materials, and presents main features of developed MMIC chip set workable in 60 GHz.

  8. Consumption of Clarified Grapefruit Juice Ameliorates High-Fat Diet Induced Insulin Resistance and Weight Gain in Mice

    PubMed Central

    Chudnovskiy, Rostislav; Thompson, Airlia; Tharp, Kevin; Hellerstein, Marc; Napoli, Joseph L.; Stahl, Andreas

    2014-01-01

    To determine the metabolic effects of grapefruit juice consumption we established a model in which C57Bl/6 mice drank 25–50% sweetened GFJ, clarified of larger insoluble particles by centrifugation (cGFJ), ad libitum as their sole source of liquid or isocaloric and sweetened water. cGFJ and control groups consumed similar amounts of liquids and calories. Mice fed a high-fat diet and cGFJ experienced a 18.4% decrease in weight, a 13–17% decrease in fasting blood glucose, a three-fold decrease in fasting serum insulin, and a 38% decrease in liver triacylglycerol values, compared to controls. Mice fed a low-fat diet that drank cGFJ experienced a two-fold decrease in fasting insulin, but not the other outcomes observed with the high-fat diet. cGFJ consumption decreased blood glucose to a similar extent as the commonly used anti-diabetic drug metformin. Introduction of cGFJ after onset of diet-induced obesity also reduced weight and blood glucose. A bioactive compound in cGFJ, naringin, reduced blood glucose and improved insulin tolerance, but did not ameliorate weight gain. These data from a well-controlled animal study indicate that GFJ contains more than one health-promoting neutraceutical, and warrant further studies of GFJ effects in the context of obesity and/or the western diet. PMID:25296035

  9. High spontaneous colony growth in chronic myelomonocytic leukemia correlates with increased disease activity and is a novel prognostic factor for predicting short survival.

    PubMed

    Sagaster, V; Ohler, L; Berer, A; Kabrna, E; Ofner, P; Lechner, K; Geissler, K

    2004-01-01

    We have originally shown that spontaneous granulocyte/macrophage colony (CFU-GM) formation in semisolid medium is a characteristic in vitro feature of chronic myelomonocytic leukemia (CMML). However, the clinical significance of spontaneous CFU-GM growth in CMML is unknown so far. CFU-GM growth characteristics were studied in semisolid cultures in the absence of exogenous cytokines using peripheral blood mononuclear cells in 30 patients with CMML at first presentation. The median number of CFU-GM/10(5) MNC of all patients was 48.5 (range 0-622) with 18 patients having colony numbers below 100 (low CFU-GM growth) and 12 patients above 100 (high CFU-GM growth). Kaplan-Meier analysis revealed that patients with high CFU-GM growth had a significantly shorter survival than patients with low CFU-GM growth (median 6.5 vs. 44.5 months, p<0.00002). The probability of survival after 2 years was 60.5% for patients with low colony growth but 0% in those with high colony formation. Patients with CFU-GM >100 had a significantly higher WBC count, a higher LDH, and a higher number of blast cells in blood and bone marrow than patients with low colony growth. Moreover, patients with high colony growth had more often splenomegaly and lower platelet counts. In seven patients, in whom semisolid in vitro cultures were performed after transformation into RAEBT/AML, spontaneous colony growth was significantly increased as compared to CFU-GM growth in patients before transformation (median number/10(5) MNC 533, range 212-4553, p<0.005). This study demonstrates that high (>100) spontaneous CFU-GM formation in CMML at presentation correlates with increased disease activity and represents a novel and important prognostic factor predicting for short survival of CMML patients. PMID:13680175

  10. Low noise, low heat dissipation, high gain AC-DC front end amplification for scanning probe microscopy.

    SciTech Connect

    Messina, P.; Fradin, F. Y.; Pittana, P. (Materials Science Division); (Sincrotrone Trieste)

    2009-01-01

    We report here on the design, construction and testing of a vacuum compatible AC-DC amplification system for low signal measurements with scanning probes. The most important feature of this new amplification system is incorporated within the head of a scanning tunneling microscope (STM). This is achieved with a very low thermal dissipation radio frequency amplifier at the STM head. The amplifier gain is higher than 40 dB and has a 50 dB maximum. Further, the AC noise figure is 0.7 dB between 100 and 1000 MHz. The noise induced in the DC amplifier is less than 2 pA RMS (root mean square), which enables the microscope to scan over soft insulating molecular layers. Thermal drift at the STM tip-sample interface is below 0.1 nm min{sup -1} both in air and in vacuum operation. Atomic resolution on highly oriented pyrolytic graphite surfaces is reliably achieved. Spin noise measurements are provided as an example of an application.

  11. Rotational-translational coupling and asymmetric line shapes in the high resolution stimulated Brillouin gain spectra of liquid carbon disulfide

    NASA Astrophysics Data System (ADS)

    Grubbs, W. T.; MacPhail, Richard A.

    1992-12-01

    We have measured high resolution stimulated Brillouin gain spectra of liquid carbon disulfide at a number of temperatures between 158 and 301 K. As the temperature decreases the shape of the Brillouin peak becomes increasingly asymmetric, with the intensity skewed away from the center of the spectrum. We show that this unusual asymmetry results from the coupling between rotational and translational motions. Rotational-translational coupling is well known to give rise to line shape distortions in the depolarized light scattering spectra of nonspherical molecules (e.g., the ``Rytov dip''), but the observation of line shape distortions (the asymmetry) in the polarized Brillouin lines has not been noted before. In the latter case, the asymmetry in the Brillouin peak can be traced to a cross correlation between the collective molecular orientation variable and the number density fluctuation and can be viewed as an acoustically induced birefringence. A calculation using the theory of rotational-translational coupling and experimental values for the relevant parameters reproduces quantitatively the observed asymmetry in the Brillouin lines over the entire temperature range.

  12. Sensor fault detection and isolation via high-gain observers: application to a double-pipe heat exchanger.

    PubMed

    Escobar, R F; Astorga-Zaragoza, C M; Téllez-Anguiano, A C; Juárez-Romero, D; Hernández, J A; Guerrero-Ramírez, G V

    2011-07-01

    This paper deals with fault detection and isolation (FDI) in sensors applied to a concentric-pipe counter-flow heat exchanger. The proposed FDI is based on the analytical redundancy implementing nonlinear high-gain observers which are used to generate residuals when a sensor fault is presented (as software sensors). By evaluating the generated residual, it is possible to switch between the sensor and the observer when a failure is detected. Experiments in a heat exchanger pilot validate the effectiveness of the approach. The FDI technique is easy to implement allowing the industries to have an excellent alternative tool to keep their heat transfer process under supervision. The main contribution of this work is based on a dynamic model with heat transfer coefficients which depend on temperature and flow used to estimate the output temperatures of a heat exchanger. This model provides a satisfactory approximation of the states of the heat exchanger in order to allow its implementation in a FDI system used to perform supervision tasks. PMID:21501838

  13. Measurement and simulation of spontaneous Raman scattering in high-pressure fuel-rich H2 air flames

    NASA Astrophysics Data System (ADS)

    Kojima, Jun; Nguyen, Quang-Viet

    2004-03-01

    Rotational and vibrational spontaneous Raman scattering (SRS) spectra of H2, N2 and H2O have been measured in H2-air flames at pressures up to 30.4 bar as a first step towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in terms of spectral resolution, wavelength coverage and signal-to-noise ratio for use in the development of transferable standards for the cross-talk calibration matrix. The fully resolved Stokes and anti-Stokes shifted spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a spectrograph fitted with a non-intensified CCD detector and a high-speed shutter. Temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometric and fuel-rich conditions. A discussion of the temperature measurement accuracy in terms of the number of laser shots, including a single-shot measurement, is presented. Theoretical Raman spectra of hydrogen were calculated using a semi-classical anharmonic-oscillator model with recent pressure broadening data and were compared with experimental data. The data and simulation showed good agreement at different equivalence ratios and pressures and indicate that high-J rotational lines of H2 may interfere with the N2 vibrational Q-branch lines, which could lead to errors in N2-Raman thermometry based on the line-fitting method. In addition, the relative intensities of the O- and S-branches to the Q-branch were determined theoretically and the result indicates that further studies of spectral interferences including contributions from O- and S-branches should be pursued. Finally, from a comparison of N2 Q-branch spectra in lean H2-air flames at nearly atmospheric (1.2 bar) and high pressure (30.4 bar), we found no significant line-narrowing or -broadening effects at a spectral resolution of 0.04 nm.

  14. Submicron Single-Gate and Dual-Gate GaAs MESFET's with Improved Low Noise and High Gain Performance

    Microsoft Academic Search

    MASAKI OGAWA; KEIICHI OHATA; T. Furutsuka; N. Kawamura

    1976-01-01

    Microwave performance of single-gate and dual-gate GaAs MESFET's with submicron gate structure is described. Design consideration and device technologies are also discussed. The performance of these GaAs MESFET's exceeds previous performance with regard to lower noise and higher gain up to X band: 2.9-dB noise figure (NF) and 10.0-dB associated gain at 12 GHz for a 0.5-mu m single-gate MESFET,

  15. A compact 1 GHz, 16 ps pulse source operating at 1060 nm incorporating a high power gain-switched semiconductor laser and fiber grating pulse compressor

    Microsoft Academic Search

    A. Piper; P. Dupriez; M. Ibsen; A. Malinowski; J. H. V. Price; B. C. Thomsen; D. J. Richardson; L. M. B. Hickey; M. N. Zervas

    2005-01-01

    Gain-switching of semiconductor laser diodes provides a practical and potentially low cost means of generating picosecond optical pulses. In this paper we describe the use of a highly dispersive chirped fiber Bragg grating (CFBG) to perform the pulse compression resulting in a very compact and attractive ps (1 GHz, 16 ps) pulse source.

  16. High-power continuous-wave diode-pumped Nd:YAlO3 laser that emits on low-gain 1378-and 1385-nm transitions

    E-print Network

    Paris-Sud XI, Université de

    High-power continuous-wave diode-pumped Nd:YAlO3 laser that emits on low-gain 1378- and 1385-nm transitions Sylvie Yiou, Franc¸ ois Balembois, Patrick Georges, and Alain Brun Efficient operation of a diode than for the 1.34- m line.10 Consequently, an efficient diode-pumped laser at 1378 and 1385 nm presents

  17. 1 TAKADA, A., SUO% T., axid SARUWATARI, M.: 'High-speed picosecond optical pulse compression from gain-switched 1.3-pm distributed

    E-print Network

    Mitchell, Chris

    compression from gain-switched 1.3-pm distributed feedback laser diode (DFB-LD) through highly dispersive single- mode fiber', J. Lightwave Technol.,1987, LT-5,pp. 152S1533 2 FRANZM, D. L., YAMABAYASHI, Y.' They have applica- tions in coded aperture imaging3 and optical image alignment? For two

  18. Optical gain spectra of high density electron-hole plasma in GaSe and InSe

    NASA Astrophysics Data System (ADS)

    Cingolani, R.; Ferrara, M.; Lugarà, M.

    1988-04-01

    We have performed stimulated emission and unsaturated optical gain measurements at low temperature in the indirect semiconductors GaSe and InSe at excitation intensities above 0.5 MW/cm2, i.e., when the critical Mott density is overcome and an electron-hole plasma (EHP) is generated. In both GaSe and InSe the gain spectra show only the band due to zero phonon recombination of indirect plasma (IEHP). No optical gain due to direct plasma (DEHP) is observed. The comparison of experimental results with theoretical models is very satisfactory. In InSe it becomes also a tool for evaluating the consistence of proposed band structures with observed data.

  19. Impaired CBF Regulation and High CBF Threshold Contribute to the Increased Sensitivity of Spontaneously Hypertensive Rats to Cerebral Ischemia

    PubMed Central

    Kang, Byeong-Teck; Leoni, Renata F.; Silva, Afonso C.

    2014-01-01

    The correlation between temporal changes of regional cerebral blood flow (rCBF) and the severity of transient ischemic stroke in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) was investigated using T2-, diffusion- and perfusion-weighted magnetic resonance imaging at six different time points: before and during 1 hour of unilateral middle cerebral artery occlusion (MCAO), 1 hour after reperfusion, and 1 day, 4 days and 7 days after MCAO. Regional CBF values were measured in both hemispheres, and the perfusion deficient lesion (PDL) was defined as the area of the brain with a 57% or more reduction in basal CBF. Within the PDL, regions were further refined as ischemic core (rCBF = 0–6 mL/100 g/min), ischemic penumbra (rCBF = 6–15 mL/100 g/min) and benign oligemia (rCBF > 15 mL/100 g/min). SHR and WKY had identical initial volume of the PDLs (WKY: 32.52±4.08% vs. SHR: 33.95±3.68%; P>0.05) and the maximum rCBF measured within those lesions (WKY: 38.20±3.57 mL/100 g/min vs. SHR: 38.46±6.22 mL/100 g/min; P>0.05) during MCAO. However, in SHR virtually all of the PDL progressed to become the final ischemic lesion (33.02±5.41%, P>0.05), while the final ischemic lesion volume of WKY (12.62±9.19%) was significantly smaller than their original PDL (P<0.01) and similar to the ischemic core (13.13±2.96%, P>0.05). The region with the lowest range of rCBF was positively correlated with the final ischemic lesion volume (r=0.716, P<0.01). Both during ischemia and after reperfusion, rCBF in either ipsilesional and contralesional brain hemispheres of SHR could not be restored to pre-ischemic levels, and remained lower than in WKY until up to 4 days after MCAO. The data suggests that impaired CBF regulation and relatively high CBF threshold for ischemia are strong contributors to the increased susceptibility of SHR to ischemic stroke. PMID:24680939

  20. [Spontaneous pneumomediastinum].

    PubMed

    Legrand, M; Dassonneville, J C; Lesobre, R

    Spontaneous pneumomediastinum is a relatively rare disease, the clinical signs of which may be misleading, and the physiopathology is still unknown. The authors report 7 cases collected over a period of 3 years and note the etiology, the clinical findings and the X-ray findings. The disease often affectsyoung sybjects, without any sex predominance. The initial symptom is thoracic pain and is often accompanied by dispnea. Subcutaneous emphysema only appears secondarily and may be mild. The association with pneumothorax is not rare. Among the etiological circumstances, pneumomediastinum often occurs after an effort or a respiratory infection with dyspnea. The diagnosis depends on the discovery of subcutaneous emphysema and on radiological signs in A.P. and lateral chest views. Treatment should be as conservative as possible in the usual benign forms. It should be limited to bed rest, analgesics and sedatives. In severe cases, supra-sternal drainage permits decompression of the mediastinum. The physiopathological mechanisms are discussed, but the usually accepted theory is rupture of an alveolus into the pulmonary interstitial tissue. The pressure gradient necessary for this rupture may be due to variations in alveolar or vascular pressure. PMID:170684

  1. Non-linear, high-gain and sustained-to-transient signal transmission from rods to amacrine cells in dark-adapted retina of Ambystoma

    PubMed Central

    Yang, Xiong-Li; Gao, Fan; Wu, Samuel M

    2002-01-01

    In darkness, On-Off amacrine cells (ACs) of the tiger salamander retina exhibited large spontaneous transient depolarizing potentials (sTDPs) with average peak amplitude of 5.05 ± 2.5 mV and average frequency of 0.42 ± 0.25 s?1. Under voltage-clamp conditions the cell displayed large spontaneous postsynaptic currents (sPSCs) with average peak amplitude of 98 ± 39 pA and average frequency of 0.45 ± 0.22 s?1. To a light step, ACs gave rise to a transient ‘On’ response at the light onset and a transient ‘Off’ response at light offset, followed by a train of TDPs (‘After’ response). Near the response threshold (0.3 activated rhodopsin molecules per rod per second), light-evoked TDPs (leTDPs) of similar amplitude and kinetics as the large sTDPs observed in darkness were seen, and about half of these leTDPs elicited a regenerative potential (RP). Brighter light steps gave rise to more leTDPs and higher rates of RPs in the On, Off and After responses. Within the linear response range of the rods, the AC response was non-linear, with the highest gain (676 ± 429) near the dark potential. The amplitude of Off responses increased with the duration of the light step, and ACs may use this to encode speeds of moving stimuli: the faster the light object moves, the smaller the AC Off response. Moreover, the number of leTDPs in the AC After response increased with light intensity, and the onset of the After response coincides with bipolar cell tail response recovery. One possible origin of the large sTDPs and leTDPs is the spontaneous and depolarization-induced regenerative calcium potentials (RCaPs) in bipolar cell synaptic terminals. RCaPs in bipolar cell synaptic terminals cause transient glutamate release that results in the sTDPs in darkness, and leTDPs in On, Off and After responses in ACs. PMID:11850516

  2. "Making it explicit" makes a difference: evidence for a dissociation of spontaneous and intentional level 1 perspective taking in high-functioning autism.

    PubMed

    Schwarzkopf, Sarah; Schilbach, Leonhard; Vogeley, Kai; Timmermans, Bert

    2014-06-01

    The ability of perspective taking is a fundamental aspect of social cognition. The ability to decide, what another person can or cannot see is referred to as "level 1 perspective taking." This is thought to be a process that we can make use of intentionally, but which also takes place spontaneously. Autism is characterized by impairments of social interaction, which are thought to be related to deficits in implicit rather than explicit perspective taking. In order to assess both levels of processing with regard to perspective taking, we employed an established task in patients and controls. Our results demonstrate that both groups engage in spontaneous level 1 perspective taking. In contrast to controls, however, patients reacted more slowly if they had to verify the other's as compared to their own perspective, which shows that participants with high-functioning autism have selective difficulties in explicit, but not implicit, level 1 perspective taking. These findings demonstrate that while spontaneous level 1 perspective taking appears to be intact in autism, this ability is impaired in patients when used explicitly. PMID:24632324

  3. Experiment on suppression of spontaneous undulator radiation at ATF

    SciTech Connect

    Litvinenko,V.; Yakimenko, V.

    2009-08-23

    We propose undertaking a demonstration experiment on suppressing spontaneous undulator radiation from an electron beam at BNL's Accelerator Test Facility (ATF). We describe the method, the proposed layout, and a possible schedule. There are several advantages in strongly suppressing shot noise in the electron beam, and the corresponding spontaneous radiation. The self-amplified spontaneous (SASE) emission originating from shot noise in the electron beam is the main source of noise in high-gain FEL amplifiers. It may negatively affect several HG FEL applications ranging from single- to multi-stage HGHG FELs. SASE saturation also imposes a fundamental hard limit on the gain of an FEL amplifier in a coherent electron-cooling scheme. A novel active method for suppressing shot noise in relativistic electron beams by many orders-of-magnitude was recently proposed. While theoretically such strong suppression appears feasible, the performance and applicability of this novel method must be evaluated experimentally. Several practical questions about the proposed noise suppressor, such as 3D effects and/or sensitivity to the e-beam parameters also require experimental clarification. To do this, we propose here a proof-of-principle experiment using elements of the VISA FEL at BNL's Accelerator Test Facility.

  4. High CO2 concentration increases relative leaf carbon gain under dynamic light in Dipterocarpus sublamellatus seedlings in a tropical rain forest, Malaysia.

    PubMed

    Tomimatsu, Hajime; Iio, Atsuhiro; Adachi, Minaco; Saw, Leng-Guan; Fletcher, Christine; Tang, Yanhong

    2014-09-01

    Understory plants in tropical forests often experience a low-light environment combined with high CO2 concentration. We hypothesized that the high CO2 concentration may compensate for leaf carbon loss caused by the low light, through increasing light-use efficiency of both steady-state and dynamic photosynthetic properties. To test the hypothesis, we examined CO2 gas exchange in response to an artificial lightfleck in Dipterocarpus sublamellatus Foxw. seedlings under contrasting CO2 conditions: 350 and 700??mol?CO2?mol(-1) air in a tropical rain forest, Pasoh, Malaysia. Total photosynthetic carbon gain from the lightfleck was about double when subjected to the high CO2 when compared with the low CO2 concentration. The increase of light-use efficiency in dynamic photosynthesis contributed 7% of the increased carbon gain, most of which was due to reduction of photosynthetic induction to light increase under the high CO2. The light compensation point of photosynthesis decreased by 58% and the apparent quantum yield increased by 26% at the high CO2 compared with those at the low CO2. The study suggests that high CO2 increases photosynthetic light-use efficiency under both steady-state and fluctuating light conditions, which should be considered in assessing the leaf carbon gain of understory plants in low-light environments. PMID:25187569

  5. Very high-gain and low-excess noise near-infrared single-photon avalanche detector: an NIR solid state photomultiplier

    NASA Astrophysics Data System (ADS)

    Linga, Krishna; Yevtukhov, Yuriy; Liang, Bing

    2009-05-01

    A new family of photodetectors with a Discrete Amplification (DA) mechanism allows the realization of very high gain and low excess noise factor in the visible and near infrared spectral regions and offers an alternative to conventional photomultiplier tubes and Geiger mode avalanche photodetectors. These photodetectors can operate in linear detection mode with gain-bandwidth product in excess of 4X1014 and in photon counting mode with count rates up to 108 counts/sec. Potential benefits of this technology over conventional avalanche photodetectors include ultra low excess noise factor, very high gain, and lower reset time (<< 1 ?s). In the photon counting mode, the devices can be operated in the non-gated mode under a constant dc bias. Because of its unique characteristics of self-quenching and self-recovery, no external quenching circuit is needed. We present the discrete amplification design approach used for the development of a solid state photomultiplier in the near infrared wavelength region. The demonstrated device performance far exceeds any available solid state photodetectors in the near infrared wavelength range. The measured devices have the following performance characteristics: gain > 2X105, excess noise factor < 1.05, rise time < 350ps, fall time < 500ps, dark current < 2X106 cps, operating voltage < 60V. These devices are ideal for researchers in the field of deep space optical communication, spectroscopy, industrial and scientific instrumentation, Ladar/Lidar, quantum cryptography, night vision and other military, defence and aerospace applications.

  6. High-gain lasing and polarization switch with a distributed optical-klystron free-electron laser.

    PubMed

    Wu, Y K; Vinokurov, N A; Mikhailov, S; Li, J; Popov, V

    2006-06-01

    This Letter reports the first experimental results from the world's first distributed optical-klystron (DOK) free-electron laser (FEL), the DOK-1 FEL, at Duke University. The DOK-1 FEL is a hybrid system, comprised of four wigglers: two horizontal and two helical. With the DOK-1 FEL, we have obtained the highest FEL gain among all storage ring based FELs at 47.8% (+/-2.7%) per pass. We have also demonstrated that the FEL gain can be enhanced by increasing electron bunching using wigglers with a different polarization. Furthermore, we have realized controlled polarization switches of the FEL beam by a nonoptical means through the manipulation of a buncher magnet. PMID:16803315

  7. A 3T Gain Cell Embedded DRAM Utilizing Preferential Boosting for High Density and Low Power On-Die Caches

    Microsoft Academic Search

    Ki Chul Chun; Pulkit Jain; Jung Hwa Lee; Chris H. Kim

    2011-01-01

    Circuittechniquesforenablingasub-0.9Vlogic-com- patible embedded DRAM (eDRAM) are presented. A boosted 3T gain cell utilizes Read Word-line (RWL) preferential boosting to increase read margin and improve data retention time. Read speed is enhanced with a hybrid current\\/voltage sense amplifier that al- lows the Read Bit-line (RBL) to remain close to VDD. A regu- lated bit-line write scheme for driving the Write Bit-line

  8. High gain-density K-band P-HEMT LNA MMIC for LMDS and satellite communication

    Microsoft Academic Search

    Yutaka Mimino; M. Hirata; K. Nakamura; K. Sakamoto; Y. Aoki; S. Kuroda

    2000-01-01

    A miniature and broadband, K-band p-HEMT LNA MMIC, that incorporates simple lumped matching elements and series bias topologies, has been developed for LMDS (Local Multi-point Distribution Service) and satellite communication. The gain and noise figure is 14.5 +\\/- 1.5 dB and 1.7 +\\/- 0.2 dB, respectively, at frequencies between 23 and 30 GHz. The die size of the MMIC is

  9. Ultrabroad-band Raman amplifiers pumped and gain-equalized by wavelength-division-multiplexed high-power laser diodes

    Microsoft Academic Search

    Shu Namiki; Yoshihiro Emori

    2001-01-01

    This paper reviews recent progress in broad-band Raman amplifiers for wavelength-division-multiplexed (WDM) applications. After the fundamentals of Raman amplifiers are discussed in contrast to erbium-doped fiber amplifiers, a new technique called “WDM pumping” is introduced to obtain ultrabroad and flat gain in Raman amplifiers only using WDM diode pumps. The design issues of this technique are then developed to realize

  10. Anomalous response in the vicinity of spontaneous symmetry breaking

    NASA Astrophysics Data System (ADS)

    Baek, Seung Ki; Park, Hye Jin; Kim, Beom Jun

    2015-05-01

    We propose a mechanism to induce negative AC permittivity in the vicinity of a ferroelectric phase transition involved with spontaneous symmetry breaking. This mechanism makes use of responses at low frequency, yielding a high gain and a large phase delay, when the system jumps over the free-energy barrier with the aid of external fields. We illustrate the mechanism by analytically studying spin models with the Glauber-typed dynamics under periodic perturbations. Then, we show that the scenario is supported by numerical simulations of mean-field as well as two-dimensional spin systems.

  11. Investigation of the gain regimes and gain parameters of the free electron laser dispersion equation

    Microsoft Academic Search

    E. Jerby; A. Gover

    1985-01-01

    The small signal gain curve and various gain parameters have been computed by solving numerically the generalized gain-dispersion equation of free electron lasers (FEL), which characterizes the conventional magnetic bremsstrahlung FEL, as well as a large number of other FEL devices. The method includes high gain, collective, and axial velocity spread effects, and some waveguide effects. The FEL gain regimes

  12. Experimental Investigation on Spontaneously Active Hippocampal Cultures Recorded by Means of High-Density MEAs: Analysis of the Spatial Resolution Effects.

    PubMed

    Maccione, Alessandro; Gandolfo, Mauro; Tedesco, Mariateresa; Nieus, Thierry; Imfeld, Kilian; Martinoia, Sergio; Berdondini, Luca

    2010-01-01

    Based on experiments performed with high-resolution Active Pixel Sensor microelectrode arrays (APS-MEAs) coupled with spontaneously active hippocampal cultures, this work investigates the spatial resolution effects of the neuroelectronic interface on the analysis of the recorded electrophysiological signals. The adopted methodology consists, first, in recording the spontaneous activity at the highest spatial resolution (interelectrode separation of 21 mum) from the whole array of 4096 microelectrodes. Then, the full resolution dataset is spatially downsampled in order to evaluate the effects on raster plot representation, array-wide spike rate (AWSR), mean firing rate (MFR) and mean bursting rate (MBR). Furthermore, the effects of the array-to-network relative position are evaluated by shifting a subset of equally spaced electrodes on the entire recorded area. Results highlight that MFR and MBR are particularly influenced by the spatial resolution provided by the neuroelectronic interface. On high-resolution large MEAs, such analysis better represent the time-based parameterization of the network dynamics. Finally, this work suggest interesting capabilities of high-resolution MEAs for spatial-based analysis in dense and low-dense neuronal preparation for investigating signaling at both local and global neuronal circuitries. PMID:20485465

  13. Spontaneous Resolution of Pneumocystis jirovecii Pneumonia on High-Resolution Computed Tomography in a Patient with Renal Cell Carcinoma

    PubMed Central

    Tanaka, Yasutaka; Saraya, Takeshi; Kurai, Daisuke; Ishii, Haruyuki; Takizawa, Hajime; Goto, Hajime

    2014-01-01

    Patient: Male, 59 Final Diagnosis: Pneumocystis jirovecii pneumonia Symptoms: Low grade fever Medication: — Clinical Procedure: Transbronchial lung biopsy Specialty: Pulmonology Objective: Rare disease Background: Spontaneous resolution of Pneumocystis jirovecii pneumonia has rarely been reported. Case Report: A 59-year-old man presented to our hospital because of pyrexia (38°C) and shaking chills for 2 days. He had a history of right nephrectomy due to renal cell carcinoma and left upper lobectomy for lung metastasis in the last 1.5 years. Two months previously, he was treated with oral prednisolone (20 mg/day) plus the intravenous mTOR inhibitor, temsirolimus (25 mg/week), for brain metastasis. On radiological examination, thoracic computed tomography showed diffuse ground glass opacities spreading in bilateral middle to lower lung fields. Although transbronchial biopsy specimens and bronchoalveolar lavage fluid demonstrated the presence of accumulation of black-colored Pneumocystis jirovecii cysts in the lung, his chief complaints and radiological abnormalities disappeared completely with no treatment. This case demonstrates a unique clinical presentation of Pneumocystis jirovecii pneumonia, in that spontaneous resolution was noted on clinical and sequential radiological evaluations. Conclusions: Increasing numbers of cytotoxic drugs and biological therapies have emerged, and changes in the immune status due to underlying diseases or administration of immunosuppressive drugs might affect the inflammatory process of Pneumocystis jirovecii pneumonia, as in the present case. PMID:25396336

  14. Experimental Setup and Commissioning of a Test Facility for Gain Evaluation of Microchannel-Plate Photomultipliers in High Magnetic Field at Jefferson Lab

    NASA Astrophysics Data System (ADS)

    Bringley, Eric; Cao, Tongtong; Ilieva, Yordonka; Nadel-Turonski, Pawel; Park, Kijun; Zorn, Carl

    2014-09-01

    At the Thomas Jefferson National Accelerator Facility (JLab) a research and development project for a Detector of Internally-Reflected Cherenkov light for the upcoming Electron Ion Collider is underway. One goal is the development of a compact readout camera that can operate in high magnetic fields. Small-size photon sensors, such as Microchannel-Plate Photomultipliers (MCP-PMT), are key components of the readout. Here we present our work to set up and commission a dedicated test facility at JLab where MCP-PMT gain is evaluated in magnetic fields of up to 5 T, and to develop a test procedure and analysis software to determine the gain. We operate the setup in a single-photon mode, where a light-emitting diode delivers photons to the sensor's photocathode. The PMT spectrum is measured with a flash Analog-to-Digital converter (fADC). We model the spectrum as a sum of an exponential background and a convolution of Poisson and Gaussian distributions of the pedestal and multiple photoelectron peaks, respectively. We determine the PMT's gain from the position of the single-photoelectron peak obtained by fitting the fADC spectrum to the model. Our gain uncertainty is <10%. The facility is now established and will have a long-lasting value for sensor tests and beyond-nuclear-physics applications.

  15. Time resolved gain/loss studies under low and high power loading for the XeF C-A transition

    SciTech Connect

    Sze, R.C. (Los Alamos National Lab., NM (USA)); Sentis, M. (Institut de Mecanique des Fluides, 13 - Marseille (France)); Vannini, M. (Consiglio Nazionale delle Ricerche, Florence (Italy). Ist. di Elettronica Quantistica)

    1990-01-01

    The behavior of gain versus peak power deposition and the gain-length product versus total energy deposited are measured for devices with power deposition levels from 1 to 13 MW/cm{sup 3} under a variety of gas mixtures. The temporal correlation between the power deposition and gain shows that both the fluorescence and the gain occur after the power deposition has concluded for excitation pulses in the range of 10--30 ns. We find that both B-X and C-A fluorescence takes place in the afterglow and their temporal shapes are similar. This indicates that the C and B states are tightly coupled. This tight coupling has two detrimental consequences for C-state lasing. First is that the population of the B and C states are approximately equal rather than 90% in the C state believed to exist for short pulse electron beam excitation. We believe this close coupling is due to the presence of electric fields in the afterglow which keep the electron temperature relatively hot. The relative populations of the B and C states are determined by a Boltzman distribution governed by the electron temperature and their relative energy separation. Second is that with the C state lifetime approximately the same as the B state lifetime the C-A saturation intensity is very high and efficient energy extraction is substantially more difficult. 5 refs., 10 figs.

  16. High-Gain Dual-Loop Antennas for MIMO Access Points in the 2.4\\/5.2\\/5.8 GHz Bands

    Microsoft Academic Search

    Saou-Wen Su

    2010-01-01

    A high-gain, three-antenna system suitable to be concealed inside wireless access points for multiple-input multiple-output (MIMO) applications in the WLAN 2.4\\/5.2\\/5.8 GHz bands is presented. The MIMO antenna system is composed of three dual-loop antennas occupying a moderate size of 10 × 20 × 40 mm3. Each dual-loop antenna further comprises a large outer loop and a small inner loop,

  17. Optical ``NOT'' Operation in a Light Transducer in which a High-gain Photoresponsive Organic Heterojunction Device is Combined with an Organic Electroluminescent Diode

    Microsoft Academic Search

    Masahiro Hiramoto; Yoshihito Motohashi; Norio Nagayama; Hiroyuki Kumaoka; Masaaki Yokoyama

    2004-01-01

    A multilayered device combining an organic electroluminescent (EL) diode with a high-gain organic photoresponsive heterojunction between phthalocyanine and perylene pigments was fabricated. The EL output under red light irradiation was reversibly erased by superimposing blue light irradiation, due to the photo-suppression of the photocurrent multiplication phenomenon at the organic\\/organic heterojunction. The spatial resolution for image conversion was confirmed to be

  18. Spectral and temporal fidelity of a hard x-ray weapons effects simulation test in a high-gain ICF (inertial confinement fusion) facility. Master's thesis

    Microsoft Academic Search

    1989-01-01

    The MORSE-CG Monte Carlo code was used to simulate the effects of hard X rays from a nuclear weapon. Facility will be an inertial confinement fusion facility for the testing of high-gain deuterium-tritium (DT) pellets, and will produce a pulse of hard X rays and neutrons over a very short time interval. A spherical shell for ⁶LiH with a thickness

  19. A 667 MHz Logic-Compatible Embedded DRAM Featuring an Asymmetric 2T Gain Cell for High Speed On-Die Caches

    Microsoft Academic Search

    Ki Chul Chun; Pulkit Jain; Tae-Ho Kim; Chris H. Kim

    2012-01-01

    Circuit techniques for enhancing the retention time and random cycle of logic-compatible embedded DRAMs (eDRAMs) are presented. An asymmetric 2T gain cell utilizes the gate and junction leakages of a PMOS write device to maintain a high data ‘1’ voltage level which enables fast read access using an NMOS read device. A current-mode sense amplifier (C-S\\/A) featuring a cross-coupled PMOS

  20. Improving proliferation resistance of high breeding gain generation 4 reactors using blankets composed of light water reactor waste

    SciTech Connect

    Hellesen, C.; Grape, S.; Haakanson, A.; Jacobson Svaerd, S.; Jansson, P. [Division of Applied Nuclear Physics, Uppsala University, Aangstroemlaboratoriet Laegerhyddsvaegen 1, 751 20 Uppsala (Sweden)

    2013-07-01

    Fertile blankets can be used in fast reactors to enhance the breeding gain as well as the passive safety characteristics. However, such blankets typically result in the production of weapons grade plutonium. For this reason they are often excluded from Generation IV reactor designs. In this paper we demonstrate that using blankets manufactured directly from spent light water (LWR) reactor fuel it is possible to produce a plutonium product with non-proliferation characteristics on a par with spent LWR fuel of 30-50 MWd/kg burnup. The beneficial breeding and safety characteristics are retained. (authors)

  1. Main resonances in directly modulated semiconductor lasers: effect of spontaneous

    E-print Network

    Toral, Raúl

    Main resonances in directly modulated semiconductor lasers: effect of spontaneous emission and gain saddle-node bifurcations related to the main resonances in pump-modulated laser diodes are obtained via] and of the spontaneous emission terms [lo] have already been considered, but little attention has been given to main

  2. Characterization of semiconductor lasers by spontaneous emission measurements

    Microsoft Academic Search

    F. Girardin; Guang-Hua Duan

    1997-01-01

    The measurement of spontaneous emission is a powerful characterization technique of semiconductor lasers, which has been developed with the fabrication of the first lasers. It allows the determination of both material and structural parameters such as gain, refractive index, longitudinal effects, etc. Significant advance has been made recently on the understanding of material properties and lasing characteristics by using spontaneous

  3. Amplified spontaneous Raman scattering in fiber Raman amplifiers

    Microsoft Academic Search

    Kiyofumi Mochizuki; Noboru Edagawa; Yoshinao Iwamoto

    1986-01-01

    Amplified spontaneous Raman scattered light power in forward and backward Raman amplifiers is theoretically and experimentally studied under the assumption of the constant Raman gain coefficient in the bandwidth of an optical filter. On the basis of the results, the power ratio of the amplified signal to amplified spontaneous scattering is discussed. As a result, it is clarified that the

  4. Impact of Korean pine nut oil on weight gain and immune responses in high-fat diet-induced obese mice.

    PubMed

    Park, Soyoung; Lim, Yeseo; Shin, Sunhye; Han, Sung Nim

    2013-10-01

    Korean pine nut oil (PNO) has been reported to have favorable effects on lipid metabolism and appetite control. We investigated whether PNO consumption could influence weight gain, and whether the PNO-induced effect would result in an improvement of immune function in high-fat diet (HFD)-induced obese mice. C57BL/6 mice were fed control diets with 10% energy fat from either PNO or soybean oil (SBO), or HFDs with 45% energy fat from 10% PNO or SBO and 35% lard, 20% PNO or SBO and 25% lard, or 30% PNO or SBO and 15% lard for 12 weeks. The proliferative responses of splenocytes upon stimulation with concanavalin A (Con A) or lipopolysaccharide (LPS), Con A-stimulated production of interleukin (IL)-2 and interferon (IFN)-?, and LPS-stimulated production of IL-6, IL-1?, and prostaglandin E2 (PGE2) by splenocytes were determined. Consumption of HFDs containing PNO resulted in significantly less weight gain (17% less, P < 0.001), and lower weight gain was mainly due to less white adipose tissue (18% less, P = 0.001). The reduction in weight gain did not result in the overall enhancement in splenocyte proliferation. Overall, PNO consumption resulted in a higher production of IL-1? (P = 0.04). Replacement of SBO with PNO had no effect on the production of IL-2, IFN-?, IL-6, or PGE2 in mice fed with either the control diets or HFDs. In conclusion, consumption of PNO reduced weight gain in mice fed with HFD, but this effect did not result in the overall improvement in immune responses. PMID:24133613

  5. Spontaneous heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased use of large-rectangular or large-round balers has been observed throughout the US. In part, this move away from small (100-lb) rectangular hay bales has occurred because of the high cost and limited availability of labor required to handle these bales. Although the efficiency of harvest i...

  6. Dynamics of a gain-switched distributed feedback ridge waveguide laser in nanoseconds time scale under very high current injection conditions.

    PubMed

    Klehr, A; Wenzel, H; Brox, O; Schwertfeger, S; Staske, R; Erbert, G

    2013-02-11

    We present detailed experimental investigations of the temporal, spectral and spatial behavior of a gain-switched distributed feedback (DFB) laser emitting at a wavelength of 1064 nm. Gain-switching is achieved by injecting nearly rectangular shaped current pulses having a length of 50 ns and a very high amplitude up to 2.5 A. The repetition frequency is 200 kHz. The laser has a ridge waveguide (RW) for lateral waveguiding with a ridge width of 3 µm and a cavity length of 1.5 mm. Time resolved investigations show, depending on the amplitude of the current pulses, that the optical power exhibits different types of oscillatory behavior during the pulses, accompanied by changes in the lateral near field intensity profiles and optical spectra. Three different types of instabilities can be distinguished: mode beating with frequencies between 25 GHz and 30 GHz, switching between different lateral intensity profiles with a frequency of 0.4 GHz and self-sustained oscillations with a frequency of 4 GHz. The investigations are of great relevance for the utilization of gain-switched DFB-RW lasers as seed lasers for fiber laser systems and in other applications, which require a high optical power. PMID:23481734

  7. Compact tunable dual-wavelength mid-infrared optical parametric oscillator pumped by high power gain-switched fiber laser

    NASA Astrophysics Data System (ADS)

    Cai, Shuangshuang; Su, Jianjia; Wu, Pinghui; Hu, Chengzhi; Jiang, Peipei

    2015-06-01

    We report, to the best of our knowledge, the first demonstration of a gain-switched fiber laser pumped tunable dual-wavelength optical parametric oscillator (OPO) operating around 3–5?µm. A homemade APMgLN crystal was used as the nonlinear material. A ‘figure-of-h’ shaped pump pulse was employed to improve the nonlinear conversion efficiency of the OPO. A maximum total idler output power of 4.82?W was obtained under pump power of 44.6?W with corresponding pump-to-idler conversion efficiency of 10.5%. The idler wavelengths were measured to be 3.34 and 3.65??m at a temperature of 40?°C, which can be successfully tuned with a rate of about 2?nm?°C?1 by adjusting the working temperature of the APMgLN crystal from 20?°C to 80?°C.

  8. Postnatal weight gain induced by overfeeding pups and maternal high-fat diet during the lactation period modulates glucose metabolism and the production of pancreatic and gastrointestinal peptides.

    PubMed

    Du, Qinwen; Hosoda, Hiroshi; Umekawa, Takashi; Kinouchi, Toshi; Ito, Natsuki; Miyazato, Mikiya; Kangawa, Kenji; Ikeda, Tomoaki

    2015-08-01

    The impact of rapid weight gain on glucose metabolism during the early postnatal period remains unclear. We investigated the influence of rapid weight gain under different nutritional conditions on glucose metabolism, focusing on the production of pancreatic and gastric peptides. On postnatal day (PND) 2, C57BL/6N pups were divided into three groups: control (C) pups whose dams were fed a control diet (10%kcal fat) and nursed 10 pups each; maternal high-fat diet (HFD) pups whose dams were fed an HFD (45%kcal fat) and nursed 10 pups each; and overfeeding (OF) pups whose dams were fed the control diet and nursed 4 pups each. Data were collected on PND 7, 14 and 21. The body weight gains of the HFD and OF pups were 1.2 times higher than that of the C pups. On PND 14, the HFD pups had higher blood glucose levels, but there were no significant differences in serum insulin levels between the HFD and C pups. The OF pups had higher blood glucose and serum insulin levels than that of the C pups. Insulin resistance was found in the HFD and OF pups. On PND 14, the content of incretins in the jejunum was increased in the OF pups, and acyl ghrelin in the stomach was upregulated in the HFD and OF pups. These results suggest that neonatal weight gain induced by overfeeding pups and maternal high-fat diet during the early postnatal period modulates the insulin sensitivity and the production of pancreatic and gastrointestinal peptides. PMID:26022984

  9. Compact high power mid-infrared optical parametric oscillator pumped by a gain-switched fiber laser with "figure-of-h" pulse shape.

    PubMed

    Jiang, Peipei; Chen, Tao; Wu, Bo; Yang, Dingzhong; Hu, Chengzhi; Wu, Pinghui; Shen, Yonghang

    2015-02-01

    We demonstrate a compact high power mid-infrared (MIR) optical parametric oscillator (OPO) pumped by a gain-switched linearly polarized, pulsed fiber laser. The gain-switched fiber laser was constructed with a piece of Yb doped polarization maintaining (PM) fiber, a pair of fiber Bragg gratings written into the matched passive PM fiber and 6 pigtailed pump laser diodes working at 915 nm with 30 W output peak power each. By modulating the pulse width of the pump laser diode, simple pedestal-free pulse shape or pedestal-free trailing pulse shape ("figure-of-h" as we call it) could be achieved from the gain-switched fiber laser. The laser was employed as the pump of a two-channel, periodically poled magnesium oxide lithium niobate-based OPO system. High power MIR emission was generated with average output power of 5.15 W at 3.8 ?m channel and 8.54 W at 3.3 ?m channel under the highest pump power of 45 W. The corresponding pump-to-idler conversion efficiency was computed to be 11.7% and 19.1%, respectively. Experimental results verify a significant improvement to signal-to-idler conversion efficiency by using "figure-of-h" pulses over simple pedestal-free pulses. Compared to the master oscillator power amplifier (MOPA) fiber laser counterpart, the presented gain switched fiber laser is more attractive in OPO pumping due to its compactness and simplicity which are beneficial to construction of OPO systems for practical MIR applications. PMID:25836126

  10. Spontaneous pneumomediastinum in children

    Microsoft Academic Search

    F. G. A. Versteegh; I. A. J. M. Broeders

    1991-01-01

    Spontaneous pneumomediastinum is defined as a non-traumatic mediastinal air leak in patients without underlying lung disease. In children it is rarely diagnosed but is likely to be often missed. We have made a comprehensive review of the literature on spontaneous pneumomediastinum in children. The aetiopathogenesis, incidence, clinical features, diagnosis and treatment are discussed. We suggest that spontaneous pneumomediastinum in children

  11. Gaining Insights from a Case Study of High School Student Performance in Dual-Credit College Chemistry Courses

    ERIC Educational Resources Information Center

    White, Jacob; Hopkins, Robert; Shockley, Denise

    2014-01-01

    This report describes student performance in a state-level initiative that provided first-year college coursework in chemistry to high school students. Upon successful completion of the coursework, students received both high school and college credit. In this initiative, high school teachers team taught college-level chemistry courses in…

  12. Intraperitoneal injection of clodronate liposomes eliminates visceral adipose macrophages and blocks high-fat diet-induced weight gain and development of insulin resistance.

    PubMed

    Bu, Le; Gao, Mingming; Qu, Shen; Liu, Dexi

    2013-10-01

    Macrophage infiltration in adipose tissue is strongly correlated with obesity. The exact role of macrophage in the development of obesity, however, has not been fully understood. In this study, using intraperitoneal injection of clodronate liposomes, we tissue-specifically depleted visceral adipose tissue macrophages (VATMs) and explored their roles in initiation and progression of obesity. Two sets of experiments were conducted, using mice on a high-fat diet as the animal model. Mice were injected with clodronate liposomes at the beginning of high-fat diet feeding to investigate the role of VATMs in the initiation of obesity. Treatment starting on week 5 was designed to explore the function of VATMs in the progression of weight gain. The results show that intraperitoneal injection of clodronate liposomes effectively depleted VATMs, which blocked high-fat diet-induced weight gain, fat accumulation, insulin resistance, and hepatic steatosis. Similarly, clodronate liposomes suppressed progression of weight gain in mice after being fed with a high-fat diet for 4 weeks and improved insulin sensitivity. Gene expression analysis showed that depletion of VATMs was associated with downregulation of the expression of genes involved in lipogenesis and gluconeogenesis including acc1, fas, scd1, and pepck, decreased expression of genes involved in chronic inflammation including mcp1 and tnf?, and suppressed expression of macrophage specific marker genes of f4/80 and cd11c in adipose tissue. Depletion of VATMs was associated with prevention of the formation of crown-like structures in white adipose tissue and the maintenance of a low level of blood TNF-?. Collectively, these data demonstrate that VATMs appeared to play a crucial role in the development of obesity and obesity-associated diseases and suggest that adipose tissue macrophages could be regarded as a potential target for drug development in prevention and therapy of obesity and obesity-associated complications. PMID:23821353

  13. High-Fat-Diet-Induced Weight Gain Ameliorates Bone Loss without Exacerbating A?PP Processing and Cognition in Female APP/PS1 Mice

    PubMed Central

    Peng, Yunhua; Liu, Jing; Tang, Ying; Liu, Jianshu; Han, Tingting; Han, Shujun; Li, Hua; Hou, Chen; Liu, Jiankang; Long, Jiangang

    2014-01-01

    Osteoporosis is negatively correlated with body mass, whereas both osteoporosis and weight loss occur at higher incidence during the progression of Alzheimer’s disease (AD) than the age-matched non-dementia individuals. Given that there is no evidence that being overweight is associated with AD-type cognitive dysfunction, we hypothesized that moderate weight gain might have a protective effect on the bone loss in AD without exacerbating cognitive dysfunction. In this study, feeding a high-fat diet (HFD, 45% calorie from fat) to female APP/PS1 transgenic mice, an AD animal model, induced weight gain. The bone mineral density, microarchitecture, and biomechanical properties of the femurs were then evaluated. The results showed that the middle-aged female APP/PS1 transgenic mice were susceptible to osteoporosis of the femoral bones and that weight gain significantly enhanced bone mass and mechanical properties. Notably, HFD was not detrimental to brain insulin signaling and A?PP processing, as well as to exploration ability and working, learning, and memory performance of the transgenic mice measured by T maze and Morris water maze, compared with the mice fed a normal-fat diet (10% calorie from fat). In addition, the circulating levels of leptin but not estradiol were remarkably elevated in HFD-treated mice. These results suggest that a body weight gain induced by the HFD feeding regimen significantly improved bone mass in female APP/PS1 mice with no detriments to exploration ability and spatial memory, most likely via the action of elevated circulating leptin. PMID:25152713

  14. JUNGFRAU 0.2: prototype characterization of a gain-switching, high dynamic range imaging system for photon science at SwissFEL and synchrotrons

    NASA Astrophysics Data System (ADS)

    Jungmann-Smith, J. H.; Bergamaschi, A.; Cartier, S.; Dinapoli, R.; Greiffenberg, D.; Johnson, I.; Maliakal, D.; Mezza, D.; Mozzanica, A.; Ruder, Ch; Schaedler, L.; Schmitt, B.; Shi, X.; Tinti, G.

    2014-12-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional pixel detector for photon science applications at free electron lasers and synchrotron light sources. It is developed for the SwissFEL currently under construction at the Paul Scherrer Institute, Switzerland. Characteristics of this application-specific integrating circuit readout chip include single photon sensitivity and low noise over a dynamic range of over four orders of magnitude of photon input signal. These characteristics are achieved by a three-fold gain-switching preamplifier in each pixel, which automatically adjusts its gain to the amount of charge deposited on the pixel. The final JUNGFRAU chip comprises 256 × 256 pixels of 75 × 75 ?m2 each. Arrays of 2 × 4 chips are bump-bonded to monolithic detector modules of about 4 × 8 cm2. Multi-module systems up to 16 Mpixels are planned for the end stations at SwissFEL. A readout rate in excess of 2 kHz is anticipated, which serves the readout requirements of SwissFEL and enables high count rate synchrotron experiments with a linear count rate capability of > 20 MHz/pixel. Promising characterization results from a 3.6 × 3.6 mm2 prototype (JUNGFRAU 0.2) with fluorescence X-ray, infrared laser and synchrotron irradiation are shown. The results include an electronic noise as low as 100 electrons root-mean-square, which enables single photon detection down to X-ray energies of about 2 keV. Noise below the Poisson fluctuation of the photon number and a linearity error of the pixel response of about 1% are demonstrated. First imaging experiments successfully show automatic gain switching. The edge spread function of the imaging system proves to be comparable in quality to single photon counting hybrid pixel detectors.

  15. Novel high-gain, improved-bandwidth, finned-ladder V-band Traveling-Wave Tube slow-wave circuit design

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Wilson, Jeffrey D.

    1994-01-01

    The V-band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for inter-satellite communications. As a first effort to develop a high-efficiency V-band Traveling-Wave Tube (TWT), variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite these advantages, however, low bandwidth and high voltage requirements have, until now, prevented its acceptance outside the laboratory. In this paper, the three-dimensional electrodynamic simulation code MAFIA (solution of MAxwell's Equation by the Finite-Integration-Algorithm) is used to investigate methods of increasing the bandwidth and lowering the operating voltage of the ring-plane circuit. Calculations of frequency-phase dispersion, beam on-axis interaction impedance, attenuation and small-signal gain per wavelength were performed for various geometric variations and loading distributions of the ring-plane TWT slow-wave circuit. Based on the results of the variations, a circuit termed the finned-ladder TWT slow-wave circuit was designed and is compared here to the scaled prototype ring-plane and a conventional ferruled coupled-cavity TWT circuit over the V-band frequency range. The simulation results indicate that this circuit has a much higher gain, significantly wider bandwidth, and a much lower voltage requirement than the scaled ring-plane prototype circuit, while retaining its excellent thermal dissipation properties. The finned-ladder circuit has a much larger small-signal gain per wavelength than the ferruled coupled-cavity circuit, but with a moderate sacrifice in bandwidth.

  16. International Topical Meeting on Microwave Photonics 10-12 September, 2003 High Conversion Gain Millimeter-wave Optoelectronic Mixer

    E-print Network

    Choi, Woo-Young

    wireless conven~r. By invcsligafing dependence of communication syslems, radio-on-fikr ryrrcmrAlAs graded buffcr laycr, the m-HEMT has shown high speed perfomsncc as well 8s high power capability [4;10-12 September, 2003 International Topical Meeting oil Microwave Photonics make it possible to detect 1.55 m

  17. Liquid crystal as laser medium with tunable gain spectra.

    PubMed

    Blinov, L M; Cipparrone, G; Lazarev, V V; Pagliusi, P; Rugiero, T

    2008-04-28

    Amplified spontaneous emission intensity and gain spectra in polarized light have been measured in a dye doped nematic liquid crystal for different orientation of its optical axis and pump intensity. A possibility for switching the gain of the liquid crystal by an external electric field is shown experimentally. The liquid crystal materials with field controlled gain can be used in microlasers and light micro-amplifiers in both planar and waveguiding geometry. PMID:18545366

  18. Co-regulation analysis of closely linked genes identifies a highly recurrent gain on chromosome 17q25.3 in prostate cancer

    PubMed Central

    Bermudo, Raquel; Abia, David; Ferrer, Berta; Nayach, Iracema; Benguria, Alberto; Zaballos, Ángel; del Rey, Javier; Miró, Rosa; Campo, Elías; Martínez-A, Carlos; Ortiz, Ángel R; Fernández, Pedro L; Thomson, Timothy M

    2008-01-01

    Background Transcriptional profiling of prostate cancer (PC) has unveiled new markers of neoplasia and allowed insights into mechanisms underlying this disease. Genomewide analyses have also identified new chromosomal abnormalities associated with PC. The combination of both classes of data for the same sample cohort might provide better criteria for identifying relevant factors involved in neoplasia. Here we describe transcriptional signatures identifying distinct normal and tumoral prostate tissue compartments, and the inference and demonstration of a new, highly recurrent copy number gain on chromosome 17q25.3. Methods We have applied transcriptional profiling to tumoral and non-tumoral prostate samples with relatively homogeneous epithelial representations as well as pure stromal tissue from peripheral prostate and cultured cell lines, followed by quantitative RT-PCR validations and immunohistochemical analysis. In addition, we have performed in silico colocalization analysis of co-regulated genes and validation by fluorescent in situ hybridization (FISH). Results The transcriptomic analysis has allowed us to identify signatures corresponding to non-tumoral luminal and tumoral epithelium, basal epithelial cells, and prostate stromal tissue. In addition, in silico analysis of co-regulated expression of physically linked genes has allowed us to predict the occurrence of a copy number gain at chromosomal region 17q25.3. This computational inference was validated by fluorescent in situ hybridization, which showed gains in this region in over 65% of primary and metastatic tumoral samples. Conclusion Our approach permits to directly link gene copy number variations with transcript co-regulation in association with neoplastic states. Therefore, transcriptomic studies of carefully selected samples can unveil new diagnostic markers and transcriptional signatures highly specific of PC, and lead to the discovery of novel genomic abnormalities that may provide additional insights into the causes and mechanisms of prostate cancer. PMID:18973659

  19. IR gain monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2013-10-01

    The gain of the IR channel of WFC3 will be measured using a series of internal flat fields. Using knowledge gained from ground testing and previous cycles, we propose to collect flat field ramps which will be used to create photon transfer curves and give a measure of the gain. This continues the strategy of last cycle's gain monitor, in proposal 13080.

  20. High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm

    Microsoft Academic Search

    P. Dupriez; A. Piper; A. Malinowski; J. K. Sahu; M. Ibsen; B. C. Thomsen; Y. Jeong; L. M. B. Hickey; M. N. Zervas; J. Nilsson; D. J. Richardson

    2006-01-01

    We demonstrate a pulsed ytterbium-doped fiber master-oscillator power amplifier source at 1060 nm producing over 300 W of average power in 20-ps pulses at 1-GHz repetition rate. The pulses generated by a gain-switched diode were compressed by a chirped fiber Bragg grating and amplified without any distortion with excellent spectral quality. This fiber master oscillator power amplifier system offers versatility

  1. High colloid oncotic pressure priming of cardiopulmonary bypass in neonates and infants: implications on haemofiltration, weight gain and renal function

    Microsoft Academic Search

    Florian Loeffelbein; Uwe Zirell; Christoph Benk; Christian Schlensak; Sven Dittrich

    2008-01-01

    Objective: To evaluate the influence of high colloid oncotic pressure (COP) priming of cardiopulmonary bypass (CPB) on fluid balances, haemofiltration, capillary leakage and renal function in neonates and infants. Methods: Twenty neonates or infants underwent heart surgery using CPB and were randomised in two groups. For group 1 (FFP-group) a blood priming with fresh frozen plasma (FFP, low oncotic pressure)

  2. Spontaneous intercalation of long-chain alkyl ammonium into edge-selectively oxidized graphite to efficiently produce high-quality graphene

    PubMed Central

    Wei, Liangming; Wu, Fei; Shi, Diwen; Hu, Changchen; Li, Xiaolin; Yuan, Weien; Wang, Jian; Zhao, Jiang; Geng, Huijuan; Wei, Hao; Wang, Ying; Hu, Nantao; Zhang, Yafei

    2013-01-01

    Mass production of high-quality graphene nanosheets (GNs) is essential for practical applications. We report that oxidation of graphite by low concentration KMnO4 at relatively high temperature (60°C) leads to edge-selectively oxidized graphite (EOG) which preserves the high crystalline graphitic structure on its basal planes while the edges are functionalized by oxygen-containing groups. Long-chain tetradecyl-ammonium salt (C14N+) could be spontaneously intercalated into EOG to form intercalated EOG-C14N+ compounds. Gentle and short-time sonication of EOG-C14N+ in toluene can full exfoliate EOG into edge-oxidized graphene nanosheets (EOGNs) with concentration of 0.67?mg/ml, monolayer population up to 90% and lateral size from 1??m to >100??m. The EOG and EOGN films show excellent electrical conductance, which is far superior to their graphene oxide (GO) counterparts. Our method provides an efficient way to produce high-quality GNs, and the resultant EOG also can be directly used for production of multifunctional materials and devices. PMID:24022463

  3. Suppression of shot noise and spontaneous radiation in electron beams

    SciTech Connect

    Litvinenko,V.

    2009-08-23

    Shot noise in the electron beam distribution is the main source of noise in high-gain FEL amplifiers, which may affect applications ranging from single- and multi-stage HGHG FELs to an FEL amplifier for coherent electron cooling. This noise also imposes a fundamental limit of about 10{sup 6} on FEL gain, after which SASE FELs saturate. There are several advantages in strongly suppressing this shot noise in the electron beam, and the corresponding spontaneous radiation. For more than a half-century, a traditional passive method has been used successfully in practical low-energy microwave electronic devices to suppress shot noise. Recently, it was proposed for this purpose in FELs. However, being passive, the method has some significant limitations and is hardly suitable for the highly inhomogeneous beams of modern high-gain FELs. I present a novel active method of suppressing, by many orders-of-magnitude, the shot noise in relativistic electron beams. I give a theoretical description of the process, and detail its fundamental limitation.

  4. Very high gain millimeter-wave InAlAs\\/InGaAs\\/GaAs metamorphic HEMT's

    Microsoft Academic Search

    K. C. Hwang; P. C. Chao; C. Creamer; K. B. Nichols; S. Wang; D. Tu; W. Kong; D. Dugas; G. Patton

    1999-01-01

    We report the first demonstration of W-band metamorphic HEMTs\\/LNA MMICs using an AlGaAsSb lattice strain relief buffer layer on a GaAs substrate. 0.1×50 ?m low-noise devices have shown typical extrinsic transconductance of 850 mS\\/mm with high maximum drain current of 700 mA\\/mm and gate-drain breakdown voltage of 4.5 V. Small-signal S-parameter measurements performed on the 0.1-?m devices exhibited an excellent

  5. Spontaneous CSF Rhinorrhea Our Experience.

    PubMed

    Deenadayal, D S; Vidyasagar, D; Naveen Kumar, M; Sudhakshin, P; Sharath Chandra, S V; Hameed, Saif

    2013-08-01

    To analyse the possible factors contributing to spontaneous cerebrospinal fluid (CSF) rhinorrhea and to assess the outcome of Transnasal endoscopic repair at our centre. Retrospective case series of patients with spontaneous CSF rhinorrhea at our institution from Jan 2006 to May 2010. 7 patients were diagnosed with spontaneous CSF rhinorrhea. 5 of the 7 patients were obese, middle aged females managed with Transnasal endoscopic repair with fascia lata auto graft. Successful repair of CSF rhinorrhea was achieved in all the patients with a single endoscopic procedure; no patient required a revision procedure. Spontaneous CSF rhinorrhea is a rare condition seen mostly in middle aged obese females with the anterior part of the cribriform plate being the most common site of leak. HRCT paranasal sinus (1 mm cuts) was an effective modality of investigation in our study with ancillary investigations been CT Cisternography, CSF analysis and MRI for inactive leaks. In the absence of a large breech of the skull base, endoscopic repair of CSF rhinorrhea carries a high success rate with a high safety margin and very low morbidity rate. PMID:24427660

  6. New insights into hydrochemical processes in lowland river systems gained from in situ, high-resolution monitoring

    NASA Astrophysics Data System (ADS)

    Wade, Andrew; Palmer-Felgate, Elizabeth; Halliday, Sarah; Skeffington, Richard; Loewenthal, Matthew; Jarvie, Helen; Bowes, Michael; Greenway, Gillian; Haswell, Stephen; Bell, Ian; Joly, Etienne; Fallatah, Ahmed; Neal, Colin; Williams, Richard; Gozzard, Emma; Newman, Jonathan

    2013-04-01

    This work focuses on the insights obtained from in situ, high-resolution hydrochemical monitoring in three lowland UK catchments experiencing different levels of nutrient enrichment. Between November 2009 and February 2012, the upper River Kennet, the River Enborne and The Cut, all located within the Thames basin, southeast England, were instrumented with in situ analytical equipment to make hourly measurements of a range of hydrochemical determinands. The upper River Kennet is a rural catchment with limited effluent inputs above the selected monitoring point. The River Enborne is a rural catchment, impacted by agricultural runoff, and septic tank and sewage treatment works (STWs) discharges. The Cut is a highly urbanised system significantly affected by STW discharges. On the upper River Kennet and the River Enborne hourly measurements of Total Reactive Phosphorus (TRP) were made using a Systea Micromac C. In addition on the River Enborne, a Hach Lange Nitratax was used to measure nitrate (NO3). On The Cut both Total P and TRP were measured using a Hach Lange Phosphax Sigma. At all stations nutrient monitoring was supplemented with hourly pH, chlorophyll, dissolved oxygen, conductivity, turbidity and water temperature using YSI 6600 Multi-parameter sondes. Instream hydrochemical dynamics were investigated using non-stationary time-series analysis techniques. The results reveal complex nutrient dynamics, with diurnal patterns which exhibit seasonal changes in phase and amplitude, and are influenced by flow conditions, shading and nutrient sources. On the River Enborne a marked diurnal cycle was present within the streamwater NO3 time-series. The cycle was strongest in the spring before riparian shading developed. At times of low flow a two peak diurnal cycle was also evident in the streamwater NO3 time-series. The reduction in diurnal NO3 processing after the development of riparian shading was also accompanied by a marked drop in dissolved oxygen at this time. The presence of a two peak diurnal cycle is indicative of the dominance of STW discharges to the system, as STW discharges exhibit a marked two peak diurnal cycle associated with peak water usage. This two peak diurnal cycling can also been seen in the River Enborne TRP data. The dominance of effluent discharges was also evident in the River Enborne seasonal NO3 and TRP dynamics. Both determinands displayed summer time peaks caused by the reduced dilution capacity of the system and increased water residence time during the low flow summer months. The TP and TRP dynamics on The Cut were highly complex with significant diurnal fluctuations. Although, a two peak diurnal signal was evident within the TRP time-series it was difficult to characterise due to the complexity of the dynamics observed. Monitoring on the upper River Kennet highlighted the challenges associated with undertaking in situ analytical monitoring without mains electricity. Resampling of the data at lower sampling frequencies demonstrated that within the point-source dominated catchments, daily monitoring was sufficient for accurate load estimation.

  7. Removing environmental sources of variation to gain insight on symbionts vs. transient microbes in high and low microbial abundance sponges.

    PubMed

    Blanquer, Andrea; Uriz, Maria J; Galand, Pierre E

    2013-11-01

    In this study, we pursue unravelling the bacterial communities of 26 sponges, belonging to several taxonomical orders, and comprising low microbial abundance (LMA) and high microbial abundance (HMA) representatives. Particularly, we searched for species-specific bacteria, which could be considered as symbionts. To reduce temporal and spatial environmentally caused differences between host species, we sampled all the sponge species present in an isolated small rocky area in a single dive. The bacterial communities identified by pyrosequencing the 16S rRNA gene showed that all HMA species clustered separated from LMA sponges and seawater. HMA sponges often had highest diversity, but some LMA sponges had also very diverse bacterial communities. Network analyses indicated that no core bacterial community seemed to exist for the studied sponges, not even for such a space and time-restricted sampling. Most sequences, particularly the most abundant ones in each species, were species-specific for both HMA and LMA sponges. The bacterial sequences retrieved from LMA sponges, despite being phylogenetically more similar to seawater, did not represent transient seawater bacteria. We conclude that sponge bacterial communities depend more on the host affiliation to the HMA or LMA groups than on host phylogeny. PMID:24118834

  8. Exercise Prevents Weight Gain and Alters the Gut Microbiota in a Mouse Model of High Fat Diet-Induced Obesity

    PubMed Central

    Evans, Christian C.; LePard, Kathy J.; Kwak, Jeff W.; Stancukas, Mary C.; Laskowski, Samantha; Dougherty, Joseph; Moulton, Laura; Glawe, Adam; Wang, Yunwei; Leone, Vanessa; Antonopoulos, Dionysios A.; Smith, Dan; Chang, Eugene B.; Ciancio, Mae J.

    2014-01-01

    Background Diet-induced obesity (DIO) is a significant health concern which has been linked to structural and functional changes in the gut microbiota. Exercise (Ex) is effective in preventing obesity, but whether Ex alters the gut microbiota during development with high fat (HF) feeding is unknown. Objective Determine the effects of voluntary Ex on the gastrointestinal microbiota in LF-fed mice and in HF-DIO. Methods Male C57BL/6 littermates (5 weeks) were distributed equally into 4 groups: low fat (LF) sedentary (Sed) LF/Sed, LF/Ex, HF/Sed and HF/Ex. Mice were individually housed and LF/Ex and HF/Ex cages were equipped with a wheel and odometer to record Ex. Fecal samples were collected at baseline, 6 weeks and 12 weeks and used for bacterial DNA isolation. DNA was subjected both to quantitative PCR using primers specific to the 16S rRNA encoding genes for Bacteroidetes and Firmicutes and to sequencing for lower taxonomic identification using the Illumina MiSeq platform. Data were analyzed using a one or two-way ANOVA or Pearson correlation. Results HF diet resulted in significantly greater body weight and adiposity as well as decreased glucose tolerance that were prevented by voluntary Ex (p<0.05). Visualization of Unifrac distance data with principal coordinates analysis indicated clustering by both diet and Ex at week 12. Sequencing demonstrated Ex-induced changes in the percentage of major bacterial phyla at 12 weeks. A correlation between total Ex distance and the ?Ct Bacteroidetes: ?Ct Firmicutes ratio from qPCR demonstrated a significant inverse correlation (r2?=?0.35, p?=?0.043). Conclusion Ex induces a unique shift in the gut microbiota that is different from dietary effects. Microbiota changes may play a role in Ex prevention of HF-DIO. PMID:24670791

  9. Three-dimensional analysis of harmonic generation in self-amplified spontaneous emission.

    SciTech Connect

    Huang, Z.; Kim, K.-J.

    1999-09-01

    In a high-gain free-electron laser, strong bunching at the fundamental wavelength can drive substantial harmonic bunching and sizable power levels at the harmonic frequencies. In this paper, we investigate the three-dimensional evolution of the harmonic fields based on the coupled Maxwell-Vlasov equations that take into account the nonlinear harmonic interaction. Each harmonic field is the sum of a self-amplified term and a term driven by the nonlinear harmonic interaction. In the exponential gain regime, the growth rate of the dominant nonlinear term is much faster than that of the self-amplified harmonic field. As a result, the gain length and the transverse profile of the first few harmonics are completely determined by those of the fundamental. A percentage of the fundamental power level is found at the third harmonic frequency right before saturation for the current self-amplified spontaneous emission projects.

  10. Simultaneous optical recording of evoked and spontaneous transients of membrane potential and intracellular calcium concentration with high spatio-temporal resolution.

    PubMed

    Sinha, S R; Patel, S S; Saggau, P

    1995-08-01

    We have developed a system for simultaneous optical recording of transients of membrane potential and intracellular calcium concentration from mammalian brain slice preparations with high spatio-temporal resolution. Simultaneous recording was achieved by using two dedicated photodetectors together with two fluorescent indicators. Specifically, the calcium-sensitive dye Calcium Orange and the voltage-sensitive dye RH-414 were selected because they have overlapping excitation spectra, but separable emission spectra. Transverse guinea pig hippocampal slices were double-loaded by bath application of the membrane-permeant form of Calcium Orange and RH-414. Transients of intracellular calcium concentration and membrane potential associated with evoked neural activity in hippocampal areas CA1 and CA3 were recorded. Furthermore, we have recorded calcium and voltage transients associated with spontaneous epileptiform activity induced by bath application of an epileptogenic drug, 4-aminopyridine. The use of photodiode matrices (10 x 10 elements each) as detectors gives the high spatial (200 x 200 microns/element with a 10 x objective) and temporal resolution (570 microseconds/frame). The recording system also includes a CCD camera for obtaining images of the preparation and overlaying the image with the optically detected signals. A software package has been developed for setting up the experimental protocol(s) and for collecting, processing, displaying, and analyzing the data in an user-friendly, windows-based environment. PMID:8544487

  11. Spontaneous ovarian hyperstimulation syndrome.

    PubMed

    Kasum, Miro; Oreskovi?, Slavko; Jezek, Davor

    2013-06-01

    Spontaneous forms of the ovarian hyperstimulation syndrome (sOHSS) are nearly always reported between 8 and 14 weeks of pregnancy and also with follicle-stimulating hormone (FSH) producing pituitary adenoma. The syndrome has been previously reported in rare instances of increased production of human chorionic gonadotrophin (hCG) such as multiple pregnancies, hydatiforme mole, polycystic ovary disease and elevated concentrations of thyroid-stimulating hormone (TSH) in hypothyreoidism. High levels of these hormones are able to stimulate by natural promiscuous activation the wild-type FSHr, resulting in sporadic presentations of the syndrome. Since 2003, only six different activating FSHr gene mutations have been reported in cases of familial or habitual sOHSS. In addition to five mutations which have been found in the transmembrane helices (Asp567Asn, Asp567Gly, Thr449Ile, Thr449Ala, Ile545Thr), the first germline mutation (c.383C > A, p. Ser 128 Tyr) in the extracelullar domain was identified. All five mutants were abnormally activated by TSH and normal levels of hCG while displaying constitutive activity. In contrast to these mutations, the p.Ser128Tyr mutant displayed an increase in sensitivity only toward hCG. Accordingly, the mutated FSHrs, may be hyperstimulated by the pregnancy-derived hCG or TSH, inducing the occurrence of the syndrome. In the differential diagnosis, malignancy, pregnancy luteoma and hyperreactio luteinalis would have to be excluded. In almost all of the cases the disease regresses spontaneously and could be managed expectantly or conservatively, but with termination of pregnancy or surgery in cases of complications. PMID:23941020

  12. Spontaneous polymerization and chain microstructure evolution in high-temperature solution polymerization of n-butyl acrylate

    Microsoft Academic Search

    Felix S. Rantow; Masoud Soroush; Michael C. Grady; Georgios A. Kalfas

    2006-01-01

    This study concerns understanding of the underlying mechanistic pathways in high temperature solution polymerization of n-butyl acrylate (nBA) in the absence of added thermal initiators. The particular system of interest is the batch polymerization of nBA in xylene at temperatures between 140 and 180°C with initial monomer content between 20 and 40wt%. A mechanistic process model is developed to capture

  13. Spontaneous emission of a two-level static atom coupling with the electromagnetic vacuum fluctuations outside a high-dimensional Einstein Gauss-Bonnet black hole

    E-print Network

    Ming Zhang; Zhan-Ying Yang; Rui-Hong Yue

    2014-07-04

    In present paper, by using the generalized DDC formalism, we investigate the spontaneous excitation of an static atom interacting with electromagnetic vacuum fluctuations outside a EGB black hole in $d$-dimensions. We find that spontaneous excitation does not occur in Boulware vacuum. The Gauss-Bonnet term has no effect on the stability of the atom. Finally, we discuss the contribution of the coupling constant and dimensional factor to the results in three different kinds of spacetime.

  14. Spontaneous organisation of ZnS nanoparticles into monocrystalline nanorods with highly enhanced dopant-related emission

    NASA Astrophysics Data System (ADS)

    Manzoor, K.; Aditya, V.; Vadera, S. R.; Kumar, N.; Kutty, T. R. N.

    2005-07-01

    A natural self-assembly process of semiconductor nanoparticles leading to the formation of doped, monocrystalline nanorods with highly enhanced dopant-related luminescence properties is reported. ˜4 nm sized, polycrystalline ZnS nanoparticles of zinc-blende (cubic) structure, doped with Cu+-Al3+ or Mn2+ have been aggregated in the aqueous solution and grown into nanorods of length ˜400 nm and aspect ratio ˜12. Transmission electron microscopic (TEM) images indicate crystal growth mechanisms involving both Ostwald-ripening and particle-to-particle oriented-attachment. Sulphur sulphur catenation is proposed for the covalent-linkage between the attached particles. The nanorods exhibit self-assembly mediated quenching of the lattice defect-related emission accompanied by multifold enhancement in the dopant-related emission. This study demonstrates that the collective behavior of an ensemble of bare nanoparticles, under natural conditions, can lead to the formation of functionalized (doped) nanorods with enhanced luminescence properties.

  15. High peak- and average-power pulse shaped fiber laser in the ns-regime applying step-index XLMA gain fibers

    NASA Astrophysics Data System (ADS)

    Dinger, R.; Grundmann, F.-P.; Hapke, C.; Ruppik, S.

    2014-03-01

    Pulsed fiber lasers and continuous-wave (cw) fiber lasers have become the tool of choice in more and more laser based industrial applications like metal cutting and welding mainly because of their robustness, compactness, high brightness, high efficiency and reasonable costs. However, to further increase the productivity with those laser types there is a great demand for even higher laser power specifications. In this context we demonstrate a pulsed high peak- and averagepower fiber laser in a Master Oscillator Power Amplifier (MOPA) configuration with selectable pulse durations between 1 ns and several hundred nanoseconds. To overcome fiber nonlinearities such as stimulated Raman scattering (SRS) and self-phase-modulation (SPM) flexible Ytterbium doped extra-large mode area (XLMA) step index fibers, prepared by novel powder-sinter technology, have been used as gain fibers. As an example, for 12 ns pulses with a repetition rate of 10 kHz, a pump power limited average laser output power of more than 400 W in combination with peak powers of more than 3.5 MW (close to self-focusing-threshold) has been achieved in stable operation. The potentials of this laser system have been further explored towards longer pulse durations in order to achieve even higher pulse energies by means of pulse shaping techniques. In addition, investigations have been conducted with reduced pulse energies and repetition rates up to 500 kHz and average powers of more than 500 W at nearly diffraction limited beam quality.

  16. Antihypertensive Effect of Radix Paeoniae Alba in Spontaneously Hypertensive Rats and Excessive Alcohol Intake and High Fat Diet Induced Hypertensive Rats

    PubMed Central

    Su-Hong, Chen; Qi, Chen; Bo, Li; Jian-Li, Gao; Jie, Su; Gui-Yuan, Lv

    2015-01-01

    Radix Paeoniae Alba (Baishao, RPA) has long been used in traditional Chinese medicine formulation to treat hypertension by repression the hyperfunction of liver. However, whether the RPA itself has the antihypertensive effect or not is seldom studied. This study was to evaluate the protective effect of RPA on hypertensive rats. Alcohol in conjunction with a high fat diet- (ACHFD-) induced hypertensive rats and spontaneously hypertensive rats (SHR) was constantly received either RPA extract (25 or 75?mg/kg) or captopril (15?mg/kg) all along the experiments. As a result, RPA extract (75?mg/kg) could significantly reduce systolic blood pressure of both ACHFD-induced hypertensive rats and SHR after 9-week or 4-week treatment. In ACHFD-induced hypertensive rats, the blood pressure was significantly increased and the lipid profiles in serum including triglyceride, total cholesterol, LDL-cholesterol, and HDL-cholesterol were significantly deteriorated. Also, hepatic damage was manifested by a significant increase in alanine transaminase (ALT) and aspartate transaminase (AST) in serum. The RPA extract significantly reversed these parameters, which revealed that it could alleviate the liver damage of rats. In SHR, our result suggested that the antihypertensive active of RPA extract may be related to its effect on regulating serum nitric oxide (NO) and endothelin (ET) levels. PMID:25784949

  17. Spontaneous imbibition characteristics of diatomite

    Microsoft Academic Search

    S Akin; J. M Schembre; S. K Bhat; A. R Kovscek

    2000-01-01

    A systematic investigation of fluid flow characteristics within diatomite (a high porosity, low permeability, siliceous rock) is reported. Using an X-ray computerized tomography (CT) scanner, and a novel, CT-compatible imbibition cell, we study spontaneous cocurrent water imbibition into diatomite samples. Air–water and oil–water systems are used and the initial water saturation is variable. Mercury porosimetry and a scanning electron microscope

  18. Rad51 gain-of-function mutants that exhibit high affinity DNA binding cause DNA damage sensitivity in the absence of Srs2.

    PubMed

    Malik, Punjab S; Symington, Lorraine S

    2008-11-01

    We previously identified several rad51 gain-of-function alleles that partially suppress the requirement for RAD55 and RAD57 in DNA repair. To gain further insight into the mechanism of action of these alleles, we compared the activities of Rad51-V328A, Rad51-P339S and Rad51-I345T with wild-type Rad51, for DNA binding, filament stability, strand exchange and interaction with the antirecombinase helicase, Srs2. These alleles were chosen because they show the highest activity in suppression of ionizing radiation sensitivity of the rad57 mutant, and Val 328 and Ile 345 are conserved in the human Rad51 protein. All three mutant proteins exhibited higher affinity for single-stranded DNA (ssDNA) and showed more robust strand exchange activity with oligonucleotide substrates than wild-type Rad51, with the Rad51-I345T and Rad51-V328A proteins displaying higher activity than Rad51-P339S. However, the Srs2 antirecombinase was able to disrupt Rad51-ssDNA complexes formed with all the mutant proteins. In vivo, the rad51-I345T mutant strain exhibited high resistance to methyl methane sulfonate that was dependent on functional SRS2. These results suggest the Srs2 translocase is able to disrupt Rad51-ssDNA complexes at stalled replication forks, but in the absence of Srs2 the enhanced DNA binding of the Rad51-I345T protein is detrimental to cell survival. PMID:18927106

  19. Spontaneous Facial Motility in Infancy: A 3D Kinematic Analysis

    PubMed Central

    Green, Jordan R.; Wilson, Erin M.

    2008-01-01

    Early spontaneous orofacial movements have rarely been studied experimentally, though the motor experiences gained from these behaviors may influence the development of motor skills emerging for speech. This investigation quantitatively describes developmental changes in silent, spontaneous lip and jaw movements from 1 to 12 months of age using optically based 3D motion capture technology. Twenty-nine typically developing infants at five ages (1, 5, 7, 9, and 12 months) were studied cross-sectionally. Infants exhibited spontaneous facial movements at all ages studied. Several age-related changes were detected in lip and jaw kinematics: the occurrence of spontaneous movements increased, movement speed increased, the duration of movement epochs decreased and movement coupling among different facial regions increased. Additionally, evidence for stereotypic movements was not strong. The present findings suggest that, during the first year of life, early spontaneous facial movements undergo significant developmental change in the direction of skill development for speech. PMID:16381029

  20. High-efficiency TEM/sub 00/ continuous-wave (Al,Ga)As epitaxial surface-emitting lasers and effect of half-wave periodic gain

    SciTech Connect

    Gourley, P.L.; Brennan, T.M.; Hammons, B.E.; Corzine, S.W.; Geels, R.S.; Yan, R.H.; Scott, J.W.; Coldren, L.A.

    1989-03-27

    We report room-temperature, continuous-wave (cw), photopumped operation of (Al,Ga)As surface-emitting lasers grown by molecular beam epitaxy. These monolithic semiconductor lasers comprise two multilayer semiconductor mirrors surrounding a layered active region. In the active region, GaAs quantum wells are spaced with half-wave periodicity to center on standing-wave maxima of the cavity optical field. By comparing threshold data for different lasers grown with and without half-wave periodicity, we observe the first experimental evidence for reduced cw lasing threshold (as low as 2 x 10/sup 4/ W/cm/sup 2/ ) with periodic gain in an epitaxial surface-emitting laser. Up to 50 mW with high efficiency (35% total, 80% differential) and narrow spectral linewidth (2 A) have been measured. A very high quality beam with low divergence (2.5/sup 0/) and circular TEM/sub 00/ profile has been observed. All of these observations represent significant advances for surface-emitting laser technology.

  1. High-efficiency TEM(00) continuous-wave (Al,Ga)As epitaxial surface-emitting lasers and effect of half-wave periodic gain

    SciTech Connect

    Gourley, P.L.; Brennan, T.M.; Hammons, B.E.; Corzine, S.W.; Geels, R.S.

    1989-03-27

    This report is on room temperature, continuous-wave (c-w), photopumped operation of (Al,Ga)As surface-emitting lasers grown by molecular beam epitaxy. These monolithic semiconductor lasers comprise two multilayer semiconductor mirrors surrounding a layered active region. In the active region, GaAs quantum wells are spaced with half-wave periodicity to center on standing-wave maxima of the cavity optical field. By comparing threshold data for different lasers grown with and without half-wave periodicity, the first experimental evidence is observed for reduced c-w lasing threshold (as low as 20,000 W/sq cm) with periodic gain in an epitaxial surface-emitting laser. Up to 50 mW with high efficiency (35% total, 80% differential) and narrow spectral linewidth (2 A) have been measured. A very high-quality beam with low divergence (2.5 deg) and circular TEM(00) profile has been observed. All of these observations represent significant advances for surface-emitting laser technology.

  2. Effects of Acidic Polysaccharides from Gastrodia Rhizome on Systolic Blood Pressure and Serum Lipid Concentrations in Spontaneously Hypertensive Rats Fed a High-Fat Diet

    PubMed Central

    Lee, Ok-Hwan; Kim, Kyung-Im; Han, Chan-Kyu; Kim, Young-Chan; Hong, Hee-Do

    2012-01-01

    The effects of acidic polysaccharides purified from Gastrodia rhizome on blood pressure and serum lipid levels in spontaneously hypertensive rats (SHR) fed a high-fat diet were investigated. Acidic polysaccharides were purified from crude polysaccharides by DEAE-Sepharose CL-6B. Thirty-six male SHR were randomly divided into three groups: Gastrodia rhizome crude polysaccharide (A), acidic polysaccharide (B) groups, and a control group (C). A 5-week oral administration of all treatment groups was performed daily in 3- to 8-week-old SHRs with a dose of 6 mg/kg of body weight/day. After 5 weeks of treatment, total cholesterol in the acidic polysaccharide group, at 69.7 ± 10.6 mg/dL, was lower than in the crude polysaccharide group (75.0 ± 6.0 mg/dL) and the control group (89.2 ± 7.4 mg/dL). In addition, triglyceride and low-density lipoprotein cholesterol levels in the acidic polysaccharide group were lower than in the crude polysaccharide and control groups. The atherogenic index of the acidic polysaccharide group was 46.3% lower than in the control group. Initial blood pressure after the initial three weeks on the high-fat diet averaged 195.9 ± 3.3 mmHg among all rats. Compared with the initial blood pressure, the final blood pressure in the control group was increased by 22.8 mmHg, whereas it decreased in the acidic polysaccharide group by 14.9 mmHg. These results indicate that acidic polysaccharides from Gastrodia rhizome reduce hypertension and improve serum lipid levels. PMID:22312280

  3. High-resolution molecular validation of self-renewal and spontaneous differentiation in clinical-grade adipose-tissue derived human mesenchymal stem cells.

    PubMed

    Dudakovic, Amel; Camilleri, Emily; Riester, Scott M; Lewallen, Eric A; Kvasha, Sergiy; Chen, Xiaoyue; Radel, Darcie J; Anderson, Jarett M; Nair, Asha A; Evans, Jared M; Krych, Aaron J; Smith, Jay; Deyle, David R; Stein, Janet L; Stein, Gary S; Im, Hee-Jeong; Cool, Simon M; Westendorf, Jennifer J; Kakar, Sanjeev; Dietz, Allan B; van Wijnen, Andre J

    2014-10-01

    Improving the effectiveness of adipose-tissue derived human mesenchymal stromal/stem cells (AMSCs) for skeletal therapies requires a detailed characterization of mechanisms supporting cell proliferation and multi-potency. We investigated the molecular phenotype of AMSCs that were either actively proliferating in platelet lysate or in a basal non-proliferative state. Flow cytometry combined with high-throughput RNA sequencing (RNASeq) and RT-qPCR analyses validate that AMSCs express classic mesenchymal cell surface markers (e.g., CD44, CD73/NT5E, CD90/THY1, and CD105/ENG). Expression of CD90 is selectively elevated at confluence. Self-renewing AMSCs express a standard cell cycle program that successively mediates DNA replication, chromatin packaging, cyto-architectural enlargement, and mitotic division. Confluent AMSCs preferentially express genes involved in extracellular matrix (ECM) formation and cellular communication. For example, cell cycle-related biomarkers (e.g., cyclins E2 and B2, transcription factor E2F1) and histone-related genes (e.g., H4, HINFP, NPAT) are elevated in proliferating AMSCs, while ECM genes are strongly upregulated (>10-fold) in quiescent AMSCs. AMSCs also express pluripotency genes (e.g., POU5F1, NANOG, KLF4) and early mesenchymal markers (e.g., NES, ACTA2) consistent with their multipotent phenotype. Strikingly, AMSCs modulate expression of WNT signaling components and switch production of WNT ligands (from WNT5A/WNT5B/WNT7B to WNT2/WNT2B), while upregulating WNT-related genes (WISP2, SFRP2, and SFRP4). Furthermore, post-proliferative AMSCs spontaneously express fibroblastic, osteogenic, chondrogenic, and adipogenic biomarkers when maintained in confluent cultures. Our findings validate the biological properties of self-renewing and multi-potent AMSCs by providing high-resolution quality control data that support their clinical versatility. PMID:24905804

  4. Rate, spectrum, and evolutionary dynamics of spontaneous epimutations.

    PubMed

    van der Graaf, Adriaan; Wardenaar, René; Neumann, Drexel A; Taudt, Aaron; Shaw, Ruth G; Jansen, Ritsert C; Schmitz, Robert J; Colomé-Tatché, Maria; Johannes, Frank

    2015-05-26

    Stochastic changes in cytosine methylation are a source of heritable epigenetic and phenotypic diversity in plants. Using the model plant Arabidopsis thaliana, we derive robust estimates of the rate at which methylation is spontaneously gained (forward epimutation) or lost (backward epimutation) at individual cytosines and construct a comprehensive picture of the epimutation landscape in this species. We demonstrate that the dynamic interplay between forward and backward epimutations is modulated by genomic context and show that subtle contextual differences have profoundly shaped patterns of methylation diversity in A. thaliana natural populations over evolutionary timescales. Theoretical arguments indicate that the epimutation rates reported here are high enough to rapidly uncouple genetic from epigenetic variation, but low enough for new epialleles to sustain long-term selection responses. Our results provide new insights into methylome evolution and its population-level consequences. PMID:25964364

  5. Rate, spectrum, and evolutionary dynamics of spontaneous epimutations

    PubMed Central

    van der Graaf, Adriaan; Wardenaar, René; Neumann, Drexel A.; Taudt, Aaron; Shaw, Ruth G.; Jansen, Ritsert C.; Schmitz, Robert J.; Colomé-Tatché, Maria; Johannes, Frank

    2015-01-01

    Stochastic changes in cytosine methylation are a source of heritable epigenetic and phenotypic diversity in plants. Using the model plant Arabidopsis thaliana, we derive robust estimates of the rate at which methylation is spontaneously gained (forward epimutation) or lost (backward epimutation) at individual cytosines and construct a comprehensive picture of the epimutation landscape in this species. We demonstrate that the dynamic interplay between forward and backward epimutations is modulated by genomic context and show that subtle contextual differences have profoundly shaped patterns of methylation diversity in A. thaliana natural populations over evolutionary timescales. Theoretical arguments indicate that the epimutation rates reported here are high enough to rapidly uncouple genetic from epigenetic variation, but low enough for new epialleles to sustain long-term selection responses. Our results provide new insights into methylome evolution and its population-level consequences. PMID:25964364

  6. High average power scaleable thin-disk laser

    DOEpatents

    Beach, Raymond J. (Livermore, CA); Honea, Eric C. (Sunol, CA); Bibeau, Camille (Dublin, CA); Payne, Stephen A. (Castro Valley, CA); Powell, Howard (Livermore, CA); Krupke, William F. (Pleasanton, CA); Sutton, Steven B. (Manteca, CA)

    2002-01-01

    Using a thin disk laser gain element with an undoped cap layer enables the scaling of lasers to extremely high average output power values. Ordinarily, the power scaling of such thin disk lasers is limited by the deleterious effects of amplified spontaneous emission. By using an undoped cap layer diffusion bonded to the thin disk, the onset of amplified spontaneous emission does not occur as readily as if no cap layer is used, and much larger transverse thin disks can be effectively used as laser gain elements. This invention can be used as a high average power laser for material processing applications as well as for weapon and air defense applications.

  7. Resveratrol suppresses body mass gain in a seasonal non-human primate model of obesity

    PubMed Central

    2010-01-01

    Background Resveratrol, a natural polyphenolic compound, was shown to protect rodents against high-fat-diet induced diabesity by boosting energy metabolism. To the best of our knowledge, no data is yet available on the effects of resveratrol in non-human primates. Six non-human heterotherm primates (grey mouse lemurs, Microcebus murinus) were studied during four weeks of dietary supplementation with resveratrol (200 mg/kg/day) during their winter body-mass gain period. Body mass, spontaneous energy intake, resting metabolic rate, spontaneous locomotor activity and daily variations in body temperature were measured. In addition, the plasma levels of several gut hormones involved in satiety control were evaluated. Results Resveratrol reduced the seasonal body-mass gain by concomitantly decreasing energy intake by 13% and increasing resting metabolic rate by 29%. Resveratrol supplementation inhibited the depth of daily torpor, an important energy-saving process in this primate. The daily amount of locomotor activity remained unchanged. Except for an increase in the glucose-dependent insulinotropic polypeptide, a gut hormone known to promote mobilization of fat stores, no major change in satiety hormone plasma levels was observed under resveratrol supplementation. Conclusions These results suggest that in a non-human primate, resveratrol reduces body-mass gain by increasing satiety and resting metabolic rate, and by inhibiting torpor expression. The measured anorectic gut hormones did not seem to play a major role in these observations. PMID:20569453

  8. COS FUV Detector Gain Maps

    NASA Astrophysics Data System (ADS)

    Sahnow, David

    2013-10-01

    This program uses the deuterium lamp to illuminate the entire region of the detector currently being used to collect spectra. The data obtained will be used to create gain maps of the detector. Because of the strongly varying intensity of the lamp as a function of wavelength, G130M/1309 data will be obtained for Segment A, and G160M/1600 will be used for Segment B.Gain map data will be obtained both before and after any change is made to the nominal high voltage value on either segment.

  9. Rice koji reduced body weight gain, fat accumulation, and blood glucose level in high-fat diet-induced obese mice

    PubMed Central

    Yoshizaki, Yumiko; Kawasaki, Chihiro; Cheng, Kai-Chun; Ushikai, Miharu; Amitani, Haruka; Asakawa, Akihiro; Okutsu, Kayu; Sameshima, Yoshihiro; Takamine, Kazunori

    2014-01-01

    Rice koji is considered a readily accessible functional food that may have health-promoting effects. We investigated whether white, yellow, and red koji have the anti-obesity effect in C57BL/6J mice fed a high-fat diet (HFD), which is a model for obesity. Mice were fed HFD containing 10% (w/w) of rice koji powder or steamed rice for 4 weeks. Weight gain, epididymal white adipose tissue, and total adipose tissue weight were significantly lower in all rice koji groups than in the HFD-rice group after 4 weeks. Feed efficiency was significantly reduced in the yellow koji group. Blood glucose levels were significantly lower in the white and red koji groups with HOMA-R and leptin levels being reduced in the white koji group. White and red koji increased glucose uptake and GLUT4 protein expression in L6 myotube cells. These results showed that all rice koji have the anti-obesity or anti-diabetes effects although the mechanisms may differ depending on the type of rice koji consumed. PMID:25237599

  10. Nutrition During Weight Gain

    E-print Network

    , Department of Food Science and Human Nutrition, 3/09 MSU is an affirmative-action, equal-opportunity employerNutrition During Pregnancy Weight Gain: The right weight gain (not too little and not too much you are taking, such as vitamins, minerals or herbs. Nutrition during pregnancy is very important

  11. Invention and Gain Analysis.

    ERIC Educational Resources Information Center

    Weber, Robert J.; Dixon, Stacey

    1989-01-01

    Gain analysis is applied to the invention of the sewing needle as well as different sewing implements and modes of sewing. The analysis includes a two-subject experiment. To validate the generality of gain heuristics and underlying switching processes, the invention of the assembly line is also analyzed. (TJH)

  12. A high calcium diet containing nonfat dry milk reduces weight gain and associated adipose tissue inflammation in diet-induced obese mice when compared to high calcium alone

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High dietary calcium (Ca) has been reported to have anti-obesity and anti-inflammatory properties. Evidence for these properties of dietary Ca in animal models of polygenic obesity have been confounded by the inclusion of dairy food components (proteins and/or carbohydrates), thus the individual ef...

  13. Giant Excess Noise and Transient Gain in Misaligned Laser Cavities

    NASA Astrophysics Data System (ADS)

    Firth, William J.; Yao, Alison M.

    2005-08-01

    The excess noise factor is calculated analytically for a very general class of optical cavities, and is shown to have a superexponential dependence on cavity misalignment, easily attaining values of order 1010. The physical basis is shown to be “transient gain” associated with amplified spontaneous emission. Similarly dramatic effects of symmetry breaking can be expected in other physical systems with non-normal modes.

  14. Brazilian Multicentre Study on Preterm Birth (EMIP): Prevalence and Factors Associated with Spontaneous Preterm Birth

    PubMed Central

    Passini, Renato; Cecatti, Jose G.; Lajos, Giuliane J.; Tedesco, Ricardo P.; Nomura, Marcelo L.; Dias, Tabata Z.; Haddad, Samira M.; Rehder, Patricia M.; Pacagnella, Rodolfo C.; Costa, Maria L.; Sousa, Maria H.

    2014-01-01

    Background Preterm birth rate is increasing and is currently a worldwide concern. The purpose of this study was to estimate the prevalence of preterm birth in a sample of health facilities in Brazil and to identify the main risk factors associated with spontaneous preterm births. Methods and Findings This was a multicentre cross sectional study on preterm births in 20 referral obstetric hospitals with a case-control component to identify factors associated with spontaneous preterm birth. Surveillance was implemented at all centres to identify preterm births. For eligible consenting women, data were collected through a post-delivery questionnaire completed with information from all mother-newborn medical records until death or discharge or at a maximum of 60 days post-delivery, whichever came first. The risk of spontaneous preterm birth was estimated with OR and 95%CI for several predictors. A non-conditional logistic regression analysis was then performed to identify independently associated factors. The overall prevalence of preterm birth was 12.3%. Among them, 64.6% were spontaneous and 35.4% therapeutic. In the case-control component, 2,682 spontaneous preterm births were compared to a sample of 1,146 term births. Multivariate analyses identified the following as risk factors for spontaneous preterm birth among women with at least one previous birth: a previous preterm birth (ORadj?=?3.19, 2.30–4.43), multiple pregnancy (ORadj?=?29.06, 8.43–100.2), cervical insufficiency (ORadj?=?2.93, 1.07–8.05), foetal malformation (ORadj?=?2.63, 1.43–4.85), polyhydramnios (ORadj?=?2.30, 1.17–4.54), vaginal bleeding (ORadj?=?2.16, 1.50–3.11), and previous abortion (ORadj?=?1.39, 1.08–1.78). High BMI (ORadj?=?0.94, 0.91–0.97) and weight gain during gestation (ORadj?=?0.92, 0.89–0.95) were found to be protective factors. Conclusions The preterm birth rate in these health facilities in Brazil is high and spontaneous preterm births account for two thirds of them. A better understanding of the factors associated with spontaneous preterm birth is of utmost importance for planning effective measures to reduce the burden of its increasing rates. PMID:25299699

  15. Suppression of the amplified spontaneous emission in chirped-pulse-amplification lasers by clean high-energy seed-pulse injection

    Microsoft Academic Search

    J. Itatani; J. Faure; M. Nantel; G. Mourou; S. Watanabe

    1998-01-01

    We have suppressed the amplified spontaneous emission in a femtosecond terawatt Ti:sapphire chirped-pulse-amplification (CPA) laser by injecting clean microjoule seed pulses into the regenerative amplifier. The intensity contrast ratio, which is one of the major difficulties in CPA lasers, was improved from ?105 in the original nanojoule injection case to ?107 in the nanosecond scale.

  16. Scintillator high-gain avalanche rushing photoconductor active-matrix flat panel imager: Zero-spatial frequency x-ray imaging properties of the solid-state SHARP sensor structure

    PubMed Central

    Wronski, M.; Zhao, W.; Tanioka, K.; DeCrescenzo, G.; Rowlands, J. A.

    2012-01-01

    Purpose: The authors are investigating the feasibility of a new type of solid-state x-ray imaging sensor with programmable avalanche gain: scintillator high-gain avalanche rushing photoconductor active matrix flat panel imager (SHARP-AMFPI). The purpose of the present work is to investigate the inherent x-ray detection properties of SHARP and demonstrate its wide dynamic range through programmable gain. Methods: A distributed resistive layer (DRL) was developed to maintain stable avalanche gain operation in a solid-state HARP. The signal and noise properties of the HARP-DRL for optical photon detection were investigated as a function of avalanche gain both theoretically and experimentally, and the results were compared with HARP tube (with electron beam readout) used in previous investigations of zero spatial frequency performance of SHARP. For this new investigation, a solid-state SHARP x-ray image sensor was formed by direct optical coupling of the HARP-DRL with a structured cesium iodide (CsI) scintillator. The x-ray sensitivity of this sensor was measured as a function of avalanche gain and the results were compared with the sensitivity of HARP-DRL measured optically. The dynamic range of HARP-DRL with variable avalanche gain was investigated for the entire exposure range encountered in radiography/fluoroscopy (R/F) applications. Results: The signal from HARP-DRL as a function of electric field showed stable avalanche gain, and the noise associated with the avalanche process agrees well with theory and previous measurements from a HARP tube. This result indicates that when coupled with CsI for x-ray detection, the additional noise associated with avalanche gain in HARP-DRL is negligible. The x-ray sensitivity measurements using the SHARP sensor produced identical avalanche gain dependence on electric field as the optical measurements with HARP-DRL. Adjusting the avalanche multiplication gain in HARP-DRL enabled a very wide dynamic range which encompassed all clinically relevant medical x-ray exposures. Conclusions: This work demonstrates that the HARP-DRL sensor enables the practical implementation of a SHARP solid-state x-ray sensor capable of quantum noise limited operation throughout the entire range of clinically relevant x-ray exposures. This is an important step toward the realization of a SHARP-AMFPI x-ray flat-panel imager. PMID:23127101

  17. Scintillator high-gain avalanche rushing photoconductor active-matrix flat panel imager: Zero-spatial frequency x-ray imaging properties of the solid-state SHARP sensor structure

    SciTech Connect

    Wronski, M.; Zhao, W.; Tanioka, K.; DeCrescenzo, G.; Rowlands, J. A. [Department of Radiation Oncology, Sunnybrook Health Sciences Center, Toronto, Ontario M4N 3M5 (Canada); Department of Radiology, State University of New York at Stony Brook, Stony Brook, New York 11794-8460 (United States); Tokyo Denki University, Tokyo, 120-8551 (Japan); Thunder Bay Regional Research Institute, Thunder Bay, Ontario P7A 7T1 (Canada)

    2012-11-15

    Purpose: The authors are investigating the feasibility of a new type of solid-state x-ray imaging sensor with programmable avalanche gain: scintillator high-gain avalanche rushing photoconductor active matrix flat panel imager (SHARP-AMFPI). The purpose of the present work is to investigate the inherent x-ray detection properties of SHARP and demonstrate its wide dynamic range through programmable gain. Methods: A distributed resistive layer (DRL) was developed to maintain stable avalanche gain operation in a solid-state HARP. The signal and noise properties of the HARP-DRL for optical photon detection were investigated as a function of avalanche gain both theoretically and experimentally, and the results were compared with HARP tube (with electron beam readout) used in previous investigations of zero spatial frequency performance of SHARP. For this new investigation, a solid-state SHARP x-ray image sensor was formed by direct optical coupling of the HARP-DRL with a structured cesium iodide (CsI) scintillator. The x-ray sensitivity of this sensor was measured as a function of avalanche gain and the results were compared with the sensitivity of HARP-DRL measured optically. The dynamic range of HARP-DRL with variable avalanche gain was investigated for the entire exposure range encountered in radiography/fluoroscopy (R/F) applications. Results: The signal from HARP-DRL as a function of electric field showed stable avalanche gain, and the noise associated with the avalanche process agrees well with theory and previous measurements from a HARP tube. This result indicates that when coupled with CsI for x-ray detection, the additional noise associated with avalanche gain in HARP-DRL is negligible. The x-ray sensitivity measurements using the SHARP sensor produced identical avalanche gain dependence on electric field as the optical measurements with HARP-DRL. Adjusting the avalanche multiplication gain in HARP-DRL enabled a very wide dynamic range which encompassed all clinically relevant medical x-ray exposures. Conclusions: This work demonstrates that the HARP-DRL sensor enables the practical implementation of a SHARP solid-state x-ray sensor capable of quantum noise limited operation throughout the entire range of clinically relevant x-ray exposures. This is an important step toward the realization of a SHARP-AMFPI x-ray flat-panel imager.

  18. Biomodal spontaneous fission

    SciTech Connect

    Hulet, E.K. (Lawrence Livermore National Lab., CA (USA))

    1989-09-26

    Investigations of mass and kinetic-energy distributions from spontaneous fission have been extended in recent years to an isotope of element 104 and, for half-lives, to an isotope of element 108. The results have been surprising in that spontaneous fission half-lives have turned out to be much longer than expected and mass and kinetic- energy distributions were found to abruptly shift away from those of the lighter actinides, showing two modes of fission. These new developments have caused a re-evaluation of our understanding of the fission process, bringing an even deeper appreciation of the role played by nuclear shell effects upon spontaneous fission properties. 16 refs., 10 figs.

  19. Spontaneous excitation of an accelerated atom: The contributions of vacuum fluctuations and radiation reaction

    Microsoft Academic Search

    Juergen Audretsch; Rainer Muller

    1994-01-01

    It was a known fact that a uniformly accelerated atom in ground state is spontaneously excited even in the vacuum. This process, known as the Unruh effect, was correlated with the emission of a particle. To gain insight in its physical mechanisms, the methods which evolved from the theory of spontaneous emission for inertial atoms were applied to the case

  20. Spontaneous vesicle recycling in the synaptic bouton

    PubMed Central

    Truckenbrodt, Sven; Rizzoli, Silvio O.

    2014-01-01

    The trigger for synaptic vesicle exocytosis is Ca2+, which enters the synaptic bouton following action potential stimulation. However, spontaneous release of neurotransmitter also occurs in the absence of stimulation in virtually all synaptic boutons. It has long been thought that this represents exocytosis driven by fluctuations in local Ca2+ levels. The vesicles responding to these fluctuations are thought to be the same ones that release upon stimulation, albeit potentially triggered by different Ca2+ sensors. This view has been challenged by several recent works, which have suggested that spontaneous release is driven by a separate pool of synaptic vesicles. Numerous articles appeared during the last few years in support of each of these hypotheses, and it has been challenging to bring them into accord. We speculate here on the origins of this controversy, and propose a solution that is related to developmental effects. Constitutive membrane traffic, needed for the biogenesis of vesicles and synapses, is responsible for high levels of spontaneous membrane fusion in young neurons, probably independent of Ca2+. The vesicles releasing spontaneously in such neurons are not related to other synaptic vesicle pools and may represent constitutively releasing vesicles (CRVs) rather than bona fide synaptic vesicles. In mature neurons, constitutive traffic is much dampened, and the few remaining spontaneous release events probably represent bona fide spontaneously releasing synaptic vesicles (SRSVs) responding to Ca2+ fluctuations, along with a handful of CRVs that participate in synaptic vesicle turnover. PMID:25538561

  1. Weight gain - unintentional

    MedlinePLUS

    ... drugs used to treat bipolar disorder, schizophrenia, and depression Some drugs used to treat diabetes Hormone changes or medical problems can also cause unintentional weight gain. This may be due to: Cushing syndrome Underactive ...

  2. Preventing Weight Gain

    MedlinePLUS

    ... proportion of fat increases. This shift slows their metabolism, making it easier to gain weight. In addition, ... Disease Control and Prevention 1600 Clifton Rd Atlanta, GA 30333 800-CDC-INFO (800-232-4636) TTY: ( ...

  3. Amplified spontaneous emission in solar-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.

    1992-01-01

    The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

  4. The Spatial and Temporal Variability of a High-Energy Beach: Insight Gained From Over 50 High-Resolution Sub-aerial Surveys

    NASA Astrophysics Data System (ADS)

    Hansen, J. E.; Barnard, P. L.

    2008-12-01

    Since April 2004 a monitoring program of 7 km-long Ocean Beach, San Francisco, CA, has led to the completion of 55 Global Positioning System topographic surveys of the sub-aerial beach. The four-year timeseries contains over 1 million beach elevation measurements and documents detailed changes of the beach over a variety of spatial, temporal, and physical forcing scales. The goal of this ongoing data collection is to understand the variability in beach response as a function of wave forcing and offshore morphology which will ultimately aid in sediment management and erosion mitigation efforts. Several statistical methods are used to describe and account for the observed beach change, including empirical orthogonal functions (EOFs) and linear regression. Results from the EOF analysis show that the first mode, and approximately 50% of the observed variance of either the mean high water (MHW) or mean sea level (MSL) position, is explained by the seasonal movement of sediment on and offshore. The second mode, and approximately 15% of the variance, is dominated by alongshore variability, possibly corresponding to the position of cusps and embayments. Higher level modes become increasingly variable in the alongshore direction and each explain little of the observed variance. In both cases the first temporal mode is well correlated (R2~=0.7) with offshore significant wave height averaged over the previous 80 to 110 days, suggesting that seasonal wave height variations are the primary driver of intra-annual shoreline position. No other modes exhibit good correlation with offshore wave parameters regardless of the averaging time. The observed seasonal change is superimposed on a longer term trend of net annual accretion at the north end of Ocean Beach and erosion at the south end. Areas at the northern end have seen as much as 60 m of cumulative shoreline progradation since 2004, while some areas of the southern portion have retrograded nearly as much. This pattern shows an overall rotation in the shoreline position hinged on a nodal point in the middle portion of the beach. The nodal point roughly corresponds to the location where the southern lobe of a large ebb tidal delta welds to the coast, suggesting that wave conditions coupled with offshore morphologic variability is a key control on short and long-term beach evolution.

  5. A low-power high-performance configurable auto-gain control loop for a digital hearing aid SoC

    NASA Astrophysics Data System (ADS)

    Chengying, Chen; Hainan, Liu; Yong, Hei; Jun, Fan; Xiaoyu, Hu

    2013-10-01

    A low-power, configurable auto-gain control loop for a digital hearing aid system on a chip (SoC) is presented. By adopting a mixed-signal feedback control structure and peak detection and judgment, it can work in automatic gain or variable gain control modes through a digital signal processing unit. A noise-reduction and dynamic range (DR) improvement technique is also used to ensure the DR of the circuit in a low-voltage supply. The circuit is implemented in an SMIC 0.13 ?m 1P8M CMOS process. The measurement results show that in a 1 V power supply, 1.6 kHz input frequency and 200 mVp—p, the SFDR is 74.3 dB, the THD is 66.1 dB, and the total power is 89 ?W, meeting the application requirements of hearing aid SoCs.

  6. Current Feedback Loop Gain Analysis and

    E-print Network

    Lanterman, Aaron

    presents a high imped- ance to the input voltage, V+ , so as to not load the driving source. Any voltage voltage to follow the non-inverting input voltage while also providing a low impedance path for an error-couple the signal gain from the loop gain part of the overall transfer function. Commonly available voltage feedback

  7. Spontaneous Causal Thinking

    Microsoft Academic Search

    Bernard Weiner

    1985-01-01

    Studies that examine spontaneous attributional activity are reviewed. The paradigms include the coding of written material, recording of thoughts during or after task completion, and indirect inferences of attributional activity exhibited in other cognitive processes. There is unequivocal documentation of attributional activity, with unexpected events and nonattainment of a goal among the antecedent cues that elicit causal search.

  8. Spontaneous spinal epidural hematoma

    Microsoft Academic Search

    Weiying Zhong; Haifeng Chen; Chao You; Jin Li; Yi Liu; Siqing Huang

    2011-01-01

    Spontaneous spinal epidural hematoma (SSEH) is a rare emergent condition. It may result in paraplegia, quadriplegia and even death. Prompt diagnosis and emergent decompressive surgical management have been recommended to prevent mortality and morbidity. Although several factors have been associated with prognosis, controversy remains, partly due to its rarity. Thus, the history, clinical presentation, physical examination findings, radiological images, and

  9. Spontaneous mediastinal emphysema

    Microsoft Academic Search

    Dorit Weissberg; Dov Weissberg

    2004-01-01

    Objective: Spontaneous mediastinal emphysema is uncommon. Its cause has not been determined precisely, but the entity is usually associated with suddenly raised alveolar pressure. Methods: Between 1980 and 2001, 114 patients with mediastinal emphysema of various causes were hospitalized in the Wolfson Medical Center. In 22 of these patients (19.3%) the emphysema occurred without an obvious preceding event and was

  10. Management by Spontaneity.

    ERIC Educational Resources Information Center

    Olson, Richard M.; Thomas, M. Donald

    1999-01-01

    Management by spontaneity shuns job descriptions, supervisory duties, needs assessment, strategic planning, group process, and problem solving. Not for the fainthearted, MBS requires knowledge of psychology, lawyerly skills, and philosophic wisdom. MBS remains untested, as current job descriptions have confined authors to MBO and TQM. (MLH)

  11. Spectral hole burnings at high energy tails in spontaneous emission and hot carrier relaxation in InGaAsP lasers

    Microsoft Academic Search

    M. Yamanishi; I. Suemune; K. Nonomura; N. Mikoshiba

    1983-01-01

    Spectral hole burnings in spontaneous emission spectra from 1.3 ..mu..m InGaAsP lasers were found. The results are understood on the basis of population burnings of holes associated with the saturation of intervalence-band absorption. Theoretical results on hot carrier relaxation are shown to explain the population burnings, pointing out an importance of nonequilibrium optical phonon populations in the active layers of

  12. Resonant periodic gain surface-emitting semiconductor lasers

    SciTech Connect

    Raja, M.Y.A.; Schaus, C.F.; McInerney, J.G.; Brennan, T.M.; Hammons, B.E.

    1989-06-01

    A novel surface-emitting semiconductor laser structure with a vertical cavity, extremely short gain medium length, and enhanced gain at a specific design wavelength is described. The active region consists of a series of quantum wells spaced at one half the wavelength of a particular optical transition in the quantum wells. This spatial periodicity allows the antinodes of the standing wave optical field to coincide with the gain elements, enhancing the frequency selectivity, increasing the gain in the vertical direction by a factor of two compared to a uniform medium or a nonresonant multiple quantum well, and substantially reducing amplified spontaneous emission. Optically pumped lasing was achieved in a GaAs/AlGaAs structure grown by molecular beam epitaxy, with the shortest gain medium (310 nm) ever reported. Various other optoelectronic devices which depend on the interaction between an electromagnetic standing wave and a carrier population distribution can also benefit from this concept.

  13. High-gain subnanowatt power consumption hybrid complementary logic inverter with WSe2 nanosheet and ZnO nanowire transistors on glass.

    PubMed

    Shokouh, Seyed Hossein Hosseini; Pezeshki, Atiye; Ali Raza, Syed Raza; Lee, Hee Sung; Min, Sung-Wook; Jeon, Pyo Jin; Shin, Jae Min; Im, Seongil

    2015-01-01

    A 1D-2D hybrid complementary logic inverter comprising of ZnO nanowire and WSe2 nanosheet field-effect transistors (FETs) is fabricated on glass, which shows excellent static and dynamic electrical performances with a voltage gain of ?60, sub-nanowatt power consumption, and at least 1 kHz inverting speed. PMID:25377731

  14. Difference in effects of stretch on depressive effect of endothelium-derived nitric oxide on noradrenaline- and high-K+-induced contractions between the aortae from normotensive and spontaneously hypertensive rats.

    PubMed

    Sekiguchi, F; Miyake, Y; Nakazumi, S; Shimamura, K; Yamamoto, K; Sunano, S

    2001-02-01

    Difference in effects of stretch tension on endothelium-derived nitric oxide (EDNO)-dependent depression of noradrenaline (NA)- and high-K+-induced contraction between the aortae from normotensive Wistar Kyoto rats (WKY) a nd stroke-pronespontaneously hypertensive rats (SHRSP) was studied. NA-induced contraction in preparations both from WKY and SHRSP was augmented in the presence of N(omega)-nitro-L-arginine (L-NNA). This augmentation was minimized when the spontaneous tone, which was more prominent in preparations from SHRSP, was subtracted and the effects of L-NNA became less prominent in preparations from SHRSP. The effects of L-NNA were maximal at the stretch tension of 15 mN and, then, decreased as stretch tension increased in both preparations when the spontaneous tone was subtracted. The effects of L-NNA were less prominent when the contraction was initiated by high-K+, although the effects of stretch on high-K+-induced contraction were similar to that of NA-induced contraction. These results suggested 1) that both NA- and high-K+-induced contractions are depressed by EDNO, 2) that the release of EDNO induced by high-K+ is less than that by NA, 3) that increase in stretch tension decreases the release of EDNO, and 4) that the depressive effect of EDNO on contraction is impaired in the aorta of SHRSP. PMID:11436982

  15. Receiver Gain Modulation Circuit

    NASA Technical Reports Server (NTRS)

    Jones, Hollis; Racette, Paul; Walker, David; Gu, Dazhen

    2011-01-01

    A receiver gain modulation circuit (RGMC) was developed that modulates the power gain of the output of a radiometer receiver with a test signal. As the radiometer receiver switches between calibration noise references, the test signal is mixed with the calibrated noise and thus produces an ensemble set of measurements from which ensemble statistical analysis can be used to extract statistical information about the test signal. The RGMC is an enabling technology of the ensemble detector. As a key component for achieving ensemble detection and analysis, the RGMC has broad aeronautical and space applications. The RGMC can be used to test and develop new calibration algorithms, for example, to detect gain anomalies, and/or correct for slow drifts that affect climate-quality measurements over an accelerated time scale. A generalized approach to analyzing radiometer system designs yields a mathematical treatment of noise reference measurements in calibration algorithms. By treating the measurements from the different noise references as ensemble samples of the receiver state, i.e. receiver gain, a quantitative description of the non-stationary properties of the underlying receiver fluctuations can be derived. Excellent agreement has been obtained between model calculations and radiometric measurements. The mathematical formulation is equivalent to modulating the gain of a stable receiver with an externally generated signal and is the basis for ensemble detection and analysis (EDA). The concept of generating ensemble data sets using an ensemble detector is similar to the ensemble data sets generated as part of ensemble empirical mode decomposition (EEMD) with exception of a key distinguishing factor. EEMD adds noise to the signal under study whereas EDA mixes the signal with calibrated noise. It is mixing with calibrated noise that permits the measurement of temporal-functional variability of uncertainty in the underlying process. The RGMC permits the evaluation of EDA by modulating the receiver gain using an external signal. Without the RGMC, samples of calibrated references from radiometers form an ensemble data set of the natural occurring fluctuations within a receiver. By driving the gain of an otherwise stable receiver with an external signal, the conceptual framework and generalization of the mathematics of EDA can be tested. A series of measurements was conducted to evaluate and characterize the performance of the RGMC. Test signals stepped the RGMC across its dynamic range of performance using a radiometer that sampled four noise references; analysis indicates that the RGMC successfully modulated the receiver gain with an external signal. Calibration algorithms applied to four noise references demonstrate the RGMC produced ensemble data sets of the external signal.

  16. Gain Clamped Two-Stage Double-Pass L-Band EDFA with a Single Fibre Bragg Grating

    NASA Astrophysics Data System (ADS)

    Sulaiman Wadi, Harun; Harith, Ahmad

    2004-10-01

    A gain clamping is demonstrated in a two-stage double-pass L-band erbium-doped fibre amplifier (EDFA) by using a single fibre Bragg grating. Two types of the fibre-Bragg-grating (FBG) broadband and narrowband have been used in the gain-clamped system. The combination of the FBG and the optical circulator has created a laser in the cavity for gain clamping. The application of a broadband FBG has improved the amplifier's efficiency and noise figure compared to the narrowband FBG system. The gain is clamped at about 22.1 dB for the amplifier with broadband FBG with gain variation of less than +/-0.15 dB and the input saturation power Psat at -8 dBm. The gain varies from 19.0 to 25.4 dB in the signal wavelength region of 1574 nm-1604 nm. The noise figure varies from 6.0 to 10.8 dB at this wavelength range. The noise figure values are found to improve by as much as 0.3-1.1 dB when compared to the unclamped amplifier for signal wavelengths above 1580 nm. The high clamped gain and low noise figure are obtained due to the suppression of the backward C-band amplified spontaneous emission. The gain clamped amplifier shows only a small power excursions when three of the four channels are added/dropped. The effects of relaxation oscillation are not seen for the gain-clamped two-stage double-pass L-band EDFA.

  17. GaNWW-oxide metal base transistor with very large current gain and power gain

    E-print Network

    Asbeck, Peter M.

    and radio frequency rf performance while maintaining the advantages of HBTs. So far, MBTs with high common-emitter is a possible candidate for microwave and millimeterwave amplifiers as well as for high-speed integrated current gain and common-base cur- rent gain have been demonstrated in several material sys- tems: 100

  18. Spontaneous rupture of uterus.

    PubMed

    Siddiqui, Meraj; Ranasinghe, J Sudharma

    2002-08-01

    Spontaneous rupture of the uterus is a life-threatening obstetrical emergency. Diagnosis may be delayed because of the bizarre presentation or absence of significant pain and tenderness, which could have been masked by the analgesic medications used during labor. We present a case of spontaneous rupture in a multigravid female who was undergoing oxytocin-augmented labor while receiving epidural analgesia. She had had no previous cesarean deliveries or uterine surgery. Half an hour after an initial complaint of left inguinal pain, which was thought to be related to a patchy epidural block, she presented with changes in vital signs and significant fetal decelerations. At emergent cesarean section, a uterine rupture was noted. The uterine rupture extended down to the left vaginal angle, was not reparable and a hysterectomy was performed. The fetus survived. PMID:12208442

  19. Roof Coating Procedures and Their Productivity Gains

    E-print Network

    Bonaby, J.; Schaub, D.

    2006-01-01

    Roof Coating Procedures and their Productivity Gains John Bonaby and Dr. Diane Schaub, University of Florida As building envelope improvements are realized in organizations as ways to insulate businesses from high energy costs, the relative...

  20. Design of Silicon Photonic Crystal Waveguides for High Gain Raman Amplification Using Two Symmetric Transvers-Electric-Like Slow-Light Modes

    NASA Astrophysics Data System (ADS)

    Hsiao, Yi-Hua; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2013-04-01

    We designed silicon photonic crystal (PhC) waveguides (WGs) for efficient silicon Raman amplifiers and lasers. We adopted narrow-width WGs to utilize two symmetric transvers-electric-like (TE-like) guided modes, which permit efficient external coupling for both the pump and Stokes waves. Modifying the size and shape of air holes surrounding the line-defect WG structures could tune the frequency difference between these two modes, at the Brillouin-zone edge, to match the Raman shift of silicon. Thus, small group velocities are also available both for pump and Stokes waves simultaneously, which results in a large enhancement of Raman gain. The enhancement factor of the Raman gain in the designed structure is more than 100 times that reported previously.

  1. Neurobiology of Disease Ionic Dynamics Mediate Spontaneous Termination of

    E-print Network

    Gutkin, Boris

    mediated by activation of sodium channels during highly active epileptic state. In contrast, an increase of recurrent, highly synchronized activity that spontaneously terminates, followed.Usingarealisticcomputationalmodel,wedemonstratethatterminationofseizureandpostictaldepres- sionstatemaybemediatedbydynamicsoftheintracellularandextracellularionconcentrations.Spontaneousterminationwaslinkedto progressive increase of intracellular sodium concentration

  2. SPONTANEOUS SOCIAL ORDERS†

    Microsoft Academic Search

    MILAN ZELENY

    1985-01-01

    As the results of man-engineered experiments with social design, social “revolution”, socialist “architectures”, and other feats of “social engineering”, are crumbling down, they are causing large-scale human suffering through their failures. There is a renewed awareness that self-organizing and spontaneous properties of complex social systems are much too powerful (and much too vulnerable at the same lime) to respond or

  3. Spontaneous intracranial hypotension

    Microsoft Academic Search

    Bahram Mokri

    2001-01-01

    Spontaneous intracranial hypotension (SIH) is typically manifested by orthostatic headaches that may be associated with one\\u000a or more of several other symptoms, including pain or stiffness of the neck, nausea, emesis, horizontal diplopia, dizziness,\\u000a change in hearing, visual blurring or visual field cuts, photophobia, interscapular pain, and occasionally face numbness or\\u000a weakness or radicular upper-limb symptoms. Cerebrospinal fluid (CSF) pressures,

  4. Low body weight gain, low white blood cell count and high serum ferritin as markers of poor nutrition and increased risk for preterm delivery.

    PubMed

    Hsu, Wen-Yin; Wu, Cheng-Hsuan; Hsieh, Charles Tsung-Che; Lo, Hui-Chen; Lin, Jen-Shiou; Kao, Mei-Ding

    2013-01-01

    This study determined factors of preterm delivery in Taiwan. Healthy women (n=520, age 29.1±4.2 y) at 8-12 weeks of pregnancy were recruited from prenatal clinics. Background information, anthropometrics, biochemical parameters, and dietary intake, collected by 24 h-recall were obtained from the first, second, and third trimesters to delivery. Clinical outcomes of neonates were also collected. The results show that 53.7% of women were primiparous and that the incidence of preterm delivery was 6.2%. Body weight gains in the first trimester and throughout pregnancy were significantly lower in mothers with preterm delivery (preterm group) than in mothers with term delivery (term group, p<0.05). Maternal cholesterol intake, circulating white blood cell counts (WBC) and serum albumin were significantly lower and that serum magnesium and ferritin were significantly higher in the preterm group than in the term group. Maternal weight gain was positively correlated with caloric and nutrient intake (p<0.05). Neonatal birth weight was positively correlated with maternal weight gain and intakes of protein and phosphate during pregnancy; with intakes of calories, vitamin B-1 and B-2 in the first trimester; and with intakes of calcium, magnesium, iron and zinc, as well as circulating WBC in the third trimester. However, neonatal birth weight was negatively correlated with serum iron in the third trimester and with serum iron and ferritin at the time of delivery. In conclusion, maternal weight gain in early pregnancy and WBC, mineral intake and iron status in late pregnancy seem to be major factors affecting delivery and neonatal outcomes. PMID:23353616

  5. Design of a high-gain laser diode-array pumped Nd:YAG Alternating Precessive Slab Amplifier (APS-Amplifier)

    NASA Technical Reports Server (NTRS)

    Coyle, D. Barry

    1991-01-01

    In the design of space qualifiable laser systems for ranging and altimetry, such as NASA's Geodynamic Laser Ranging System (GLRS), the transmitter must be kept small, powerful yet efficient, and must consist of as few components as possible. A novel preamplifier design is examined which requires no external beam steering optics, yielding a compact component with simple alignment procedures. The gains achieved are comparable to multipass zigzag amplifiers using two or more sets of external optics for extra passes through the amplifying medium.

  6. A low-noise, and high-gain double-balanced mixer for 77 GHz automotive radar front-ends in SiGe bipolar technology

    Microsoft Academic Search

    W. Perndl; H. Knapp; M. Wurzer; K. Aufinger; T. F. Meister; T. F. Bock; W. Simburger; A. L. Scholtz

    2004-01-01

    An active down-conversion mixer for automotive radar applications at 76 GHz to 81 GHz was realized in a 200 GHz fT SiGe bipolar technology. A conversion gain of more than 24 dB and a single-sideband noise figure of less than 14 dB is achieved. The 1 dB output compression point is -4 dBm. The power consumption is 300 mW at

  7. Performance results of the high-gain Nd:glass engineering prototype preamplifier module (PAM) for the National Ignition Facility (NIF)

    Microsoft Academic Search

    Mikael D. Martinez; Kenneth M. Skulina; Fred J. Deadrick; John K. Crane; Bryan D. Moran; John Braucht; Bobby Jones; Steven Hawkins; Ronald Tilley; James Crawford; Donald F. Browning; Frank A. Penko

    1999-01-01

    We describe recent, energetics performance results on the engineering preamplifier module (PAM) prototype located in the front end of the 1.8 MJ National Ignition Facility laser system. Three vertically mounted subsystem located in the PAM provide laser gain as well as spatial beam shaping. The first subsystem in the PAM prototype is a diode pumped, Nd:glass, linear, TEM00, 4.5 m

  8. 1.55-micron multiquantum well semiconductor optical amplifier with low gain ripple and high coupling efficiency for photonic circuit integration

    Microsoft Academic Search

    M. A. Newkirk; B. I. Miller; U. Koren; M. G. Young; M. Chien; R. M. Jopson; G. Raybon; C. A. Burrus; H. M. Presby

    1993-01-01

    The Letter demonstrates a 1.55-micron multiquantum well amplifier on an extended InGaAsP passive waveguide with only +\\/- 0.14 dB gain. Reflectivity less than 8 x 10 exp -5 from active-to-passive transitions and 41 percent coupling efficiency from a single-mode fiber are obtained. These amplifiers are suitable for integration with other optical devices in photonic integrated circuits.

  9. Analysis and simulation of nonlinearity and effects of spontaneous emission in Schottky-junction-based plasmonic amplifiers.

    PubMed

    Livani, Abdolber Mallah; Kaatuzian, Hassan

    2015-07-01

    An amplifier that operates on surface plasmon polaritons has been analyzed and simulated. Nonlinearity behavior and the spontaneous emission effects of the plasmonic amplifier are investigated in this paper. A rate equations approach has been used in which parameters are derived from simulation results of the plasmonic amplifier (Silvaco/ATLAS). Details on the method of this derivation are included, which were not previously reported. Rate equations are solved numerically by MATLAB codes. These codes verify the Silvaco results. The plasmonic amplifier operates on surface plasmons with a free-space wavelength of 1550 nm. Results show that, even without the effect of spontaneous emission, gain of the plasmonic amplifier saturates in high input levels. Saturation power, which can be used for comparing nonlinearity of different amplifiers, is 2.1 dBm for this amplifier. Amplified spontaneous emission reduces the gain of the amplifiers, which is long. There is an optimum value for the length of the amplifier. For the amplifier of this work, the optimum length for the small signal condition is 265 ?m. PMID:26193159

  10. Spontaneous mechanical activity in depolarized frog ventricle

    PubMed Central

    1976-01-01

    Spontaneous mechanical activity can be produced in depolarized frog ventricle by bathing the tissue in a solution with low Na, Iow Ca, and high K+. The contractions can be inhibited by depleting the tissue of Ca first, but they are relatively insensitive to changes in either extracellular [Ca++] or [Ca++]/[Na+]2. They are terminated very rapidly by raising [Na+] to 40 mM. Local anesthetics enhance the spontaneous activity in proportion to the concentration of their free base form. These contractions occur relatively rhythmically for several hours. Since the preparation is multicellular, this suggests a mechanism for intercellular communication without change in membrane potential. PMID:822122

  11. Factors influencing spontaneous combustion of solid waste.

    PubMed

    Moqbel, Shadi; Reinhart, Debra; Chen, Ruey-Hung

    2010-01-01

    Landfill fires create a critical problem for landfill operators and require investigation of its occurrence and the conditions that favor its initiation. Subsurface fires are considered the most significant due to the difficulty in determining their location and extent. These fires are mainly caused by spontaneous combustion, combustion due to high temperature in absence of flame. This study investigates the effect of moisture content, oxygen concentration and leachate components on spontaneous ignition, combustion initiation, and self-heating of solid waste. A new procedure for testing spontaneous ignition is described; however, variations in solid waste components and landfill conditions can create some limitations to its use. The presence of water and dissolved solids in leachate was found to accelerate chemical self-heating of the solid waste. Oxygen concentration at 10% by volume can sustain chemical oxidation but did not promote accelerated burning. PMID:20110161

  12. CMOS Programmable Gain Distributed Amplifier With 0.5dB Gain Steps

    Microsoft Academic Search

    Byul Hur; William R. Eisenstadt

    2011-01-01

    A new CMOS programmable gain distributed am- plifier with 0.5-dB gain steps is fabricated in a 130-nm process. The circuit is designed to demonstrate broadband ( 1 decade) programmable gains with excellent matching and high isolation for use in RF integrated-circuit testing. The measured slope of loss is approximately 3 dB\\/decade over frequencies from 0.8 to 9 GHz where input

  13. Smoking Cessation and Weight Gain.

    ERIC Educational Resources Information Center

    Hall, Sharon M.; And Others

    1986-01-01

    Investigated determinants of weight gain after quitting smoking in two smoking treatment outcome studies. Results indicated abstinence resulted in weight gain, and postquitting weight gain was predicted by pretreatment tobacco use, a history of weight problems, and eating patterns. Relapse to smoking did not follow weight gain. (Author/BL)

  14. Assess the key physics that underpins high-hydro coupling-efficiency in NDCX-II experiments and high-gain heavy ion direct drive target designs using proven hydro codes like HYDRA

    SciTech Connect

    Barnard, J. J.; Hay, M. J.; Logan, B. G.; Ng, S. F.; Perkins, L. J.; Veitzer, S.; Yu, S. S.

    2010-07-01

    The simulations provided in this milestone have solidified the theoretical underpinning of direct drive targets and also the ability to design experiments on NDCX II that will enhance our understanding of ion-beam hydrodynamic coupling, and thus be relevant to IFE. For the case of the IFE targets, we have studied hydro and implosion efficiency using HYDRA in ID, a starting point towards the goal of polar direct drive in geometry compatible with liquid wall chambers. Recent analysis of direct drive fusion energy targets using heavy ion beams has found high coupling efficiency of ion beam energy into implosion energy. However, to obtain optimal coupling, the ion energy must increase during the pulse in order to penetrate the outflowing ablated material, and deposit the energy close enough to the fuel so that the fuel achieves sufficient implosion velocity. We have computationally explored ID (radial) time dependent models of ion driven direct drive capsule implosions using the Arbitrary Lagrangian-Eulerian (ALE) code HYDRA, to help validate the theoretical analysis done so far, particularly exploring the effects of varying the ion energy and ion current over the course of the pulse. On NDCX II, experiments have been proposed to explore issues of ion penetration of the outflowing plasma over the course of the ion pulse. One possibility is to create a first pulse of ions that heats a planar target, and produces an outflow of material. A second pulse, {approx}10 ns after the first, of higher ion energy (and hence larger projected range) will interact with this outflow before reaching and further heating the target. We have investigated whether the change in range can be tailored to match the evolution of the ablation front. We have carried out simulations using the one-dimensional hydrodynamic code DISH and HYDRA to set parameters for this class of experiments. DISH was upgraded with an ion deposition algorithm, and we have carried out ID (planar) simulations. HYDRA was also used for ID (planar) and 2D (r,z) simulations of potential experiments. We have also explored whether similar physics could be studied using an energy ramp (i.e., a velocity tilt) rather than two separate pulses. We have shown that an optimum occurs in the macropulse duration (with fixed velocity tilt) that maximizes the shock strength. In the area of IFE target design we have continued to explore direct drive targets composed of deuterium-tritium fuel and ablator layers. We have extended our previous target designs at 0.44 MJ drive energy, gain 50, (50 MeV foot, 500 MeV main pulse, Rb ion, which requires a large number of beams due to a high beam space charge constraint) to a power plant scale 3.7 MJ drive energy, gain {approx}150 (220 MeV foot, 2.2 GeV main pulse, Hg ion) that eases requirements on the accelerator. We have studied the effects of two important design choices on ICF target performance. We have shown that increasing the number of foot pulses may reduce the target's in-flight adiabat and consequently improve its compressibility and fusion yield. As in the case of laser drive, the first three shocks are the most important to the target's performance, with additional shocks contributing only marginally to compression and burn. We have also demonstrated that ion range lengthening during the main pulse can further reduce the target adiabat and improve the efficiency with which beam energy is coupled into the target. (Ion range lengthening using two different kinetic energies for the foot and main pulse has previously proven effective in the design of high gain targets).

  15. High efficiency, full-color AlInGaN quaternary nanowire light emitting diodes with spontaneous core-shell structures on Si

    NASA Astrophysics Data System (ADS)

    Wang, Renjie; Liu, Xuedong; Shih, Ishiang; Mi, Zetian

    2015-06-01

    We have developed AlInGaN quaternary core-shell nanowire heterostructures on Si substrate, wherein an In-rich core and an Al-rich shell were spontaneously formed during the epitaxial growth process. By varying the growth conditions, the emission wavelengths can be tuned from ˜430 nm to ˜630 nm. Such core-shell structures can largely suppress nonradiative surface recombination, leading to a significant enhancement of carrier lifetime from ˜0.2 ns to ˜2 ns. The resulting nanowire light emitting diodes can exhibit an output power exceeding 30 mW for a ˜1 × 1 mm2 non-packaged device at a current density of 100 A/cm2.

  16. Pre-pregnancy BMI and weight gain: where is the tipping point for preterm birth?

    PubMed Central

    2013-01-01

    Background Obesity in pregnant women is a major problem affecting both the mother and her offspring. Literature on the effect of obesity on preterm birth is inconsistent and few studies have investigated the influence of weight gain during pregnancy. This study examined the effect of maternal pre-pregnancy BMI and weight gain during pregnancy on preterm birth. Methods Data from the Collaborative Perinatal Project (CPP) on 45,824 pregnant women with singleton, live-born infants with no sever congenital anomalies was analyzed. Primary outcome variables included preterm (< 37 weeks of gestation), categorized into spontaneous preterm with and without premature rupture of membrane (PROM) and indicated preterm. Maternal BMI was categorized into underweight (BMI?spontaneous preterm birth with PROM among overweight women decreased with increasing weight gain but increased among women who had excessive weight gain. Similarly, a U-shaped rate of spontaneous preterm birth with and without PROM was observed in obese women. Gaining less weight was protective of spontaneous preterm with and without PROM among overweight and obese women compared to normal weight women. Among underweight women, gaining?gain and the subtypes of preterm births among African Americans and Caucasian Americans. Conclusion Reduced weight gain during pregnancy among overweight and obese women is associated with reduced spontaneous preterm birth with and without PROM. Health care professionals and public health workers should be aware of this risk and adhere to the 2009 IOM guideline that recommended reduced weight gain during pregnancy for obese and overweight women. PMID:23706121

  17. Understanding bichromatic emission from scattering gain media

    NASA Astrophysics Data System (ADS)

    Balachandran, R. M.; Lawandy, N. M.

    1996-10-01

    Intense optical pumping of solutions of high-gain laser dyes and TiO 2 nanoscatterers in methanol is found to result in narrow-linewidth bichromatic emission. Experimental studies of the long-wavelength emission peak show that weak pumping of the scattering gain medium by the primary lasing emission results in a random system that lases at longer wavelengths. Measurements with other dyes show that the bichromatic emission effect is very general.

  18. Mechanism of stability enhancement of passively harmonic mode-locked erbium doped fiber ring laser by passively modulating the saturable absorber's loss and the amplifier's gain depletion at high frequency

    NASA Astrophysics Data System (ADS)

    ?chiopu, Ionut Romeo; ?chiopu, Paul

    2010-11-01

    After many experimental investigations of passive harmonic mode-locking erbium doped fiber ring laser cavity, we have observed some new typical characteristics of the solitons and we propose here a circular cavity laser where a high frequency cavity transmission modulation is possible by sending a reflected pulse into the cavity, in the opposite direction to the direct pulse. The pre-saturation of the absorber and the gain depletion at the optimum frequency, superposed on the natural effect of harmonic state, determine a stable harmonic solitonic state. In this mode we can better estimate the importance of the role of unstable continuous waves and of gain recovery in forming a stable equidistant multisoliton state.

  19. Cash and in-kind transfers lead to excess weight gain in a population of women with a high prevalence of overweight in rural Mexico.

    PubMed

    Leroy, Jef L; Gadsden, Paola; González de Cossío, Teresa; Gertler, Paul

    2013-03-01

    There is a growing concern that food or cash transfer programs may contribute to overweight and obesity in adults. We studied the impact of Mexico's Programa de Apoyo Alimentario (PAL), which provided very poor rural households with cash or in-kind transfers, on women's body weight. A random sample of 208 rural communities in southern Mexico was randomly assigned to 1 of 4 groups: food basket with or without health and nutrition education, cash with education, or control. The impact on women's weight was estimated in a cohort of 3010 women using a difference-in-difference model. We compared the impact between the food basket and cash groups and evaluated whether the impact was modified by women's BMI status at baseline. With respect to the control group, the program increased women's weight in the food basket (550 ± 210 g; P = 0.004) and the cash group (420 ± 230 g; P = 0.032); this was equivalent to 70 and 53% increases in weight gain, respectively, over that observed in the control group in a 23-mo time period. The greatest impact was found in already obese women: 980 ± 290 g in the food basket group (P = 0.001) and 670 ± 320 g in the cash group (P = 0.019). Impact was marginally significant in women with a preprogram BMI between 25 and 30 kg/m2: 490 ± 310 g (P = 0.055) and 540 ± 360 g (P = 0.067), respectively. No program impact was found in women with a BMI <25 kg/m2. Providing households with a considerable amount of unrestricted resources led to excess weight gain in an already overweight population. Research is needed to develop cost-effective behavior change communication strategies to complement cash and in-kind transfer programs such as PAL and to help beneficiaries choose healthy diets that improve the nutritional status of all family members. PMID:23343672

  20. Silicon photonic crystals spontaneous emission

    E-print Network

    Polman, Albert

    Silicon photonic crystals and spontaneous emission #12;Silicon photonic crystals and spontaneous and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands. #12;Silicon photonic crystals based on silicon 17 2.1 Introduction 18 2.2 Bandstructure calculations 18 2.3 2-D photonic crystal

  1. Spontaneous Emission from Planar Microstructures

    Microsoft Academic Search

    D. G. Deppe; C. Lei; C. C. Lin; D. L. Huffaker

    1994-01-01

    The alteration of spontaneous emission characteristics in terms of the spontaneous lifetime and spectral emission characteristics are discussed for dipoles in the presence of nearby planar reflecting interfaces and cavities, specifically for the case of semiconductors. For dipoles closely spaced to absorbing metal mirrors, significant lifetime change is possible. Analysis and experimental data are presented for light emitting diodes. For

  2. Gain function and hydrocarbon indicators

    Microsoft Academic Search

    De-hua Han; Michael Batzle

    1999-01-01

    Summary We have derived the gain function for porous rock based on the Gassmann's equation. We study property of the gain function for consolidated sandstone and poor consolidated sands from deep-water, Gulf of Mexico. We apply the gain function to derive pore fluid modulus as a hydrocarbon indicator from log data.

  3. Intrinsically-low Brillouin gain optical fibers

    NASA Astrophysics Data System (ADS)

    Dragic, Peter D.; Ballato, John; Morris, Stephanie; Hawkins, Thomas

    2013-05-01

    Numerous methods to increase the stimulated Brillouin scattering (SBS) threshold have been previously implemented. Some are passive, based on acousto-optic fiber designs that incorporate longitudinally- or radially-tailored optical and/or acoustic index profiles, leading to broadened Brillouin gain spectra (BGS) with reduced peak gain. Some are active, relying on an applied temperature or strain distribution, also resulting in broadened BGS. Broadening the laser spectrum still represents the most effective method to-date to obtain large-scale (> 20 dB) decreases in the gain, but the suitability of this method depends largely on the application and system requirements on the laser spectrum. Despite these technologies, some introduced only in the last decade, the vast majority of high-energy, narrow-linewidth fiber laser systems are still limited by SBS rather than the availability of pump power. We present an alternative approach; rather than focusing on `suppressing' SBS in waveguide or other designs, we propose implementing materials with intrinsically low Brillouin gain. We focus on high-density, high-soundvelocity, large acoustic-damping-coefficient, and low-photoelastic-constant materials wherein the correct balancing of physical characteristics gives rise to extremely low Brillouin gain. In general, the approach requires the use of compositions that would be considered to be highly unconventional and unachievable utilizing standard fiber fabrication methods. For example, we describe recent results on sapphire-derived fibers (among other compositions) wherein a Brillouin gain nearly 20 dB lower than those of more conventional fibers has been realized. Other compositions will also be presented, including new results on a novel baria doped fiber, including others predicted to have zero-valued photoelastic constants, and therefore zero Brillouin gain.

  4. Gain and energy storage in holmium YLF

    NASA Technical Reports Server (NTRS)

    Storm, Mark E.; Deyst, John P.

    1991-01-01

    It is demonstrated that Q-switched holmium lasers are capable of high-gain and high-energy operation at 300 K. Small-signal gain coefficients of 0.50 and 0.12/cm have been measured in YLF and YAG, respectively. Small-signal gains of 0.50/cm are comparable to those achievable in Nd:YAG and are not typical of low-gain materials. This large gain in the Ho:YLF material is made possible by operating the amplifier in the ground state depletion mode. The amplifier performance data and associated analysis presented demonstrate that efficient energy storage is possible with very high excited state ion densities of the Ho 5I7 upper laser level. This is an important result since upconversion can limit the 5I7 population. Although upconversion was still present in this experiment, it was possible to achieve efficient energy storage, demonstrating that the problem is manageable even at high excitation densities in YLF.

  5. High power 1018 nm monolithic Yb3+-doped fiber laser and amplifier

    Microsoft Academic Search

    H Xiao; P Zhou; X L Wang; S F Guo; X J Xu

    2012-01-01

    In this letter high power monolithic 1018 nm fiber laser and amplifier are presented. The output characteristics of 1018 nm laser with amplified spontaneous emission (ASE) feedback, fiber Bragg gratings (FBG) reflectivity, gain fiber length and other parameters are experimentally investigated. The difference between 1018 and 1064 nm amplification are also compared in experiment. Based on these experimental results, we

  6. Rosuvastatin reduces gliosis and the accelerated weight gain observed in WT and ApoE?\\/? mice exposed to a high cholesterol diet

    Microsoft Academic Search

    Daniel Famer; Milita Crisby

    2007-01-01

    The influence of a high cholesterol (HC) diet on brain pathology is being recognized increasingly and is of immense interest. Previous findings from our laboratory demonstrated that a high cholesterol diet increases gliosis, astrocytic reactivity and neuroinflammation in both wild type (WT) and apolipoprotein knockout (ApoE?\\/?) mice.In the present study, we analyzed whether this increase in astrocytic reactivity, monitored by

  7. Property evaluation on the spontaneous polarity for nanopowders.

    PubMed

    Meng, Junping; Liang, Jinsheng; Ding, Yan; Han, Yilin; Yuan, Youde

    2011-11-01

    For the tourmaline fine powders, in view of their low polarized charge density and easily occurred neutralization, a new evaluation model on the spontaneous polarity was proposed. By adjusting the temperature and applying electric field, the polarized charge could be measured. On this basis, a portable evaluation device was designed and assembled into four parts: Voltage Input Unit, Temperature Control Unit, Sample Loading Unit, and Charge Detection Unit. Using the designed device, the property evaluation on the spontaneous polarity of tourmaline fine powders was carried out. The spontaneous polarization intensity was finally achieved. After experimental verification, the method had the characteristics of easy operation and high accuracy. PMID:22413324

  8. Enhancing optical gains in Si nanocrystals via hydrogenation and cerium ion doping

    SciTech Connect

    Wang, Dong-Chen; Li, Yan-Li; Song, Sheng-Chi; Guo, Wen-Ping; Lu, Ming, E-mail: minglu55@fudan.edu.cn [Department of Optical Science and Engineering, and Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Fudan University, Shanghai 200433 (China); Chen, Jia-Rong [Department of Optical Science and Engineering, and Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Fudan University, Shanghai 200433 (China); School of Information Engineering, Guizhou Minzu University, Guiyang 550025 (China)

    2014-07-28

    We report optical gain enhancements in Si nanocrystals (Si-NCs) via hydrogenation and Ce{sup 3+} ion doping. Variable stripe length technique was used to obtain gains. At 0.3?W/cm{sup 2} pumping power density of pulsed laser, net gains were observed together with gain enhancements after hydrogenation and/or Ce{sup 3+} ion doping; gains after loss corrections were between 89.52 and 341.95?cm{sup ?1}; and the photoluminescence (PL) lifetime was found to decrease with the increasing gain enhancement. At 0.04?W/cm{sup 2} power density, however, no net gain was found and the PL lifetime increased with the increasing PL enhancement. The results were discussed according to stimulated and spontaneous excitation and de-excitation mechanisms of Si-NCs.

  9. Simulation of an X-ray laser in the transient gain-saturation regime

    SciTech Connect

    Starikov, F A; Volkov, V A; Gasparyan, P D; Roslov, V I [Russian Federal Nuclear Center - The All-Russian Research Institute of Experimental Physics, Sarov, Nizhnii Novgorod Region (Russian Federation)

    2009-09-30

    By using the TRANS code, we performed three-dimensional calculations of amplified spontaneous emission (ASE) in X-ray lasers on the 3p-3s transition in Ne-like Ge ({lambda} = 19.6 nm) and Ti ({lambda} = 2.6 nm) operating in the transient regime upon irradiation of a flat target by a high-power picosecond laser pulse focused into a line with one or two nanosecond prepulses. The hydrodynamics and population kinetics of the active medium of X-ray lasers were calculated by using the SS-9M code. The pulse duration, the gain, the spatial structure of the laser beam and the type of influence of a 'travelling' pump wave on the ASE brightness obtained in calculations are in agreement with the experimental data. The use of the 'travelling pump wave' leads not only to the increase in the ASE brightness but also considerably reduces its angular divergence. (active media)

  10. Acting to gain information

    NASA Technical Reports Server (NTRS)

    Rosenchein, Stanley J.; Burns, J. Brian; Chapman, David; Kaelbling, Leslie P.; Kahn, Philip; Nishihara, H. Keith; Turk, Matthew

    1993-01-01

    This report is concerned with agents that act to gain information. In previous work, we developed agent models combining qualitative modeling with real-time control. That work, however, focused primarily on actions that affect physical states of the environment. The current study extends that work by explicitly considering problems of active information-gathering and by exploring specialized aspects of information-gathering in computational perception, learning, and language. In our theoretical investigations, we analyzed agents into their perceptual and action components and identified these with elements of a state-machine model of control. The mathematical properties of each was developed in isolation and interactions were then studied. We considered the complexity dimension and the uncertainty dimension and related these to intelligent-agent design issues. We also explored active information gathering in visual processing. Working within the active vision paradigm, we developed a concept of 'minimal meaningful measurements' suitable for demand-driven vision. We then developed and tested an architecture for ongoing recognition and interpretation of visual information. In the area of information gathering through learning, we explored techniques for coping with combinatorial complexity. We also explored information gathering through explicit linguistic action by considering the nature of conversational rules, coordination, and situated communication behavior.

  11. Precision Measurement of the Undulator K Parameter using Spontaneous Radiation

    SciTech Connect

    Welch, J.J.; Arthur, J.; Emma, P.; Hastings, J.B.; Huang, Z.; Nuhn, H.D.; Stefan, P.; /SLAC; Bionta, R.M.; /LLNL, Livermore; Dejus, R.J.; Yang, B.X.; /Argonne

    2007-04-17

    Obtaining precise values of the undulator parameter, K, is critical for producing high-gain FEL radiation. At the LCLS [1], where the FEL wavelength reaches down to 1.5 {angstrom}, the relative precision of K must satisfy ({Delta}K/K){sub rms} {approx}< 0.015% over the full length of the undulator. Transverse misalignments, construction errors, radiation damage, and temperature variations all contribute to errors in the mean K values among the undulator segments. It is therefore important to develop some means to measure relative K values, after installation and alignment. We propose a method using the angle-integrated spontaneous radiation spectrum of two nearby undulator segments, and the natural shot-to-shot energy jitter of the electron beam. Simulation of this scheme is presented using both ideal and measured undulator fields. By ''leap-frogging'' to different pairs of segments with extended separations we hope to confirm or correct the values of K, including proper tapering, over the entire 130-m long LCLS undulator.

  12. Can LENR Energy Gains Exceed 1000?

    NASA Astrophysics Data System (ADS)

    Nagel, David J.

    2011-03-01

    Energy gain is defined as the energy realized from reactions divided by the energy required to produce those reactions. Low Energy Nuclear Reactions (LENR) have already been measured to significantly exceed the energy gain of 10 projected from ITER,possibly 15 years from now. Electrochemical experiments using the Pd-D system have shown energy gains exceeding 10. Gas phase experiments with the Ni-H system were reported to yield energy gains of over 100. Neither of these reports has been adequately verified or reproduced. However, the question in the title still deserves consideration. If, as thought by many, it is possible to trigger nuclear reactions that yield MeV energies with chemical energies of the order of eV, then the most optimistic expectation is that LENR gains could approach one million. Hence, the very tentative answer to the question above is yes. However, if LENR could be initiated with some energy cost, and then continue to ``burn,'' very high energy gains might be realized. Consider a match and a pile of dry logs. The phenomenon termed ``heat after death'' will be examined to see if it might be the initial evidence for nuclear ``burning.''

  13. D-band MMIC LNAs with 12 dB gain at 155 GHz fabricated on a high yield InP HEMT MMIC production process

    Microsoft Academic Search

    R. Lai; H. Wang; Y. C. Chen; T. Block; P. H. Liu; D. C. Streit; D. Tran; P. Siegel; M. Barsky; W. Jones; T. Gaier

    1997-01-01

    We have developed a highly robust, high performance 0.1 ?m passivated InP HEMT MMIC process with frequency capability up to 200 GHz and beyond. This process has demonstrated consistent wafer to wafer performance as well as remarkable uniformity with a wafer average Gmp of 1100 mS\\/mm ±44 mS for more than 1000 sites tested over a 2 inch diameter wafer.

  14. Spontaneous fission of the heaviest elements

    SciTech Connect

    Hoffman, D.C.

    1989-04-01

    Although spontaneous fission was discovered in /sup 238/U in 1940, detailed studies of the process were first made possible in the 1960's with the availability of milligram quantities of /sup 252/Cf. The advent of solid-state detectors made it possible to perform measurements of coincident fission fragments from even very short-lived spontaneous fission activities or those available in only very small quantities. Until 1971 it was believed that the main features of the mass and kinetic-energy distributions were essentially the same as those for thermal neutron-induced fission and that all low-energy fission proceeded via asymmetric mass division with total kinetic energies which could be derived by linear extrapolation from those of lighter elements. In 1971, measurements of /sup 257/Fm showed an increase in symmetric mass division with anomalously high TKE's. Subsequent experiments showed that in /sup 258/Fm and /sup 259/Fm, the most probable mass split was symmetric with very high total kinetic energy. Measurements for the heavier elements have shown symmetric mass distributions with both high and low total kinetic energies. Recent results for spontaneous fission properties of the heaviest elements are reviewed and compared with theory. 31 refs., 8 figs., 1 tab.

  15. Spontaneous breaking of supersymmetry

    SciTech Connect

    Zumino, B.

    1981-12-01

    There has been recently a revival of interest in supersymmetric gauge theories, stimulated by the hope that supersymmetry might help in clarifying some of the questions which remain unanswered in the so called Grand Unified Theories and in particular the gauge hierarchy problem. In a Grand Unified Theory one has two widely different mass scales: the unification mass M approx. = 10/sup 15/GeV at which the unification group (e.g. SU(5)) breaks down to SU(3) x SU(2) x U(1) and the mass ..mu.. approx. = 100 GeV at which SU(2) x U(1) is broken down to the U(1) of electromagnetism. There is at present no theoretical understanding of the extreme smallness of the ratio ..mu../M of these two numbers. This is the gauge hierarchy problem. This lecture attempts to review the various mechanisms for spontaneous supersymmetry breaking in gauge theories. Most of the discussions are concerned with the tree approximation, but what is presently known about radiative correction is also reviewed.

  16. Spontaneous Retrobulbar Haematoma

    PubMed Central

    Deveer, Mehmet; Cullu, Nesat; Beydilli, Halil; Sozen, Hamdi; Yeniceri, Onder; Parlak, Selcuk

    2015-01-01

    Background. Spontaneous orbital haemorrhage is a very rare condition and vision-threatening event. It may occur due to trauma, orbital surgery/injections, orbital vascular anomalies, and a variety of systemic predisposing factors. Signs of retrobulbar hemorrhage include proptosis, ophthalmoplegia, increased intraocular pressure, loss of pupillary reflexes, and optic disc or retinal pallor. Both Computed Tomography scan and Magnetic Resonance Imaging may be performed in the diagnosis. Case Report. A 31-year-old woman was referred to our hospital with a complaint of headache and blurred vision following a strong sneeze. Ophthalmological examination revealed mild Relative Afferent Pupillary Defect in left eye. Computed Tomography revealed left hyperdense retrobulbar mass and displaced optic nerve. T1 weighted hypointense, T2 weighted hyperintense and non-enhanced round shape, sharply demarcated lesion measuring 18 × 15 × 14 × mm in diameter compatible with haematoma was detected by MRI. Surgically Caldwell-Luc procedure was performed. Histological examination confirmed haematoma. Follow-up Magnetic Resonance Imaging revealed a small reduction in the size of lesion but not complete resolution. The patient's complaint was regressed. She is now free of symptoms and is still under surveillance. To our knowledge, this is the first reported case of retrobulbar haematoma caused by sneeze. PMID:26090258

  17. Spontaneous Retrobulbar Haematoma.

    PubMed

    Deveer, Mehmet; Cullu, Nesat; Beydilli, Halil; Sozen, Hamdi; Yeniceri, Onder; Parlak, Selcuk

    2015-01-01

    Background. Spontaneous orbital haemorrhage is a very rare condition and vision-threatening event. It may occur due to trauma, orbital surgery/injections, orbital vascular anomalies, and a variety of systemic predisposing factors. Signs of retrobulbar hemorrhage include proptosis, ophthalmoplegia, increased intraocular pressure, loss of pupillary reflexes, and optic disc or retinal pallor. Both Computed Tomography scan and Magnetic Resonance Imaging may be performed in the diagnosis. Case Report. A 31-year-old woman was referred to our hospital with a complaint of headache and blurred vision following a strong sneeze. Ophthalmological examination revealed mild Relative Afferent Pupillary Defect in left eye. Computed Tomography revealed left hyperdense retrobulbar mass and displaced optic nerve. T1 weighted hypointense, T2 weighted hyperintense and non-enhanced round shape, sharply demarcated lesion measuring 18 × 15 × 14 × mm in diameter compatible with haematoma was detected by MRI. Surgically Caldwell-Luc procedure was performed. Histological examination confirmed haematoma. Follow-up Magnetic Resonance Imaging revealed a small reduction in the size of lesion but not complete resolution. The patient's complaint was regressed. She is now free of symptoms and is still under surveillance. To our knowledge, this is the first reported case of retrobulbar haematoma caused by sneeze. PMID:26090258

  18. Rates of spontaneous mutation.

    PubMed Central

    Drake, J W; Charlesworth, B; Charlesworth, D; Crow, J F

    1998-01-01

    Rates of spontaneous mutation per genome as measured in the laboratory are remarkably similar within broad groups of organisms but differ strikingly among groups. Mutation rates in RNA viruses, whose genomes contain ca. 10(4) bases, are roughly 1 per genome per replication for lytic viruses and roughly 0.1 per genome per replication for retroviruses and a retrotransposon. Mutation rates in microbes with DNA-based chromosomes are close to 1/300 per genome per replication; in this group, therefore, rates per base pair vary inversely and hugely as genome sizes vary from 6 x 10(3) to 4 x 10(7) bases or base pairs. Mutation rates in higher eukaryotes are roughly 0.1-100 per genome per sexual generation but are currently indistinguishable from 1/300 per cell division per effective genome (which excludes the fraction of the genome in which most mutations are neutral). It is now possible to specify some of the evolutionary forces that shape these diverse mutation rates. PMID:9560386

  19. Brillouin optical correlation domain analysis with 4 millimeter resolution based on amplified spontaneous emission.

    PubMed

    Cohen, Raphael; London, Yosef; Antman, Yair; Zadok, Avi

    2014-05-19

    A new technique for Brillouin scattering-based, distributed fiber-optic measurements of temperature and strain is proposed, analyzed, simulated, and demonstrated. Broadband Brillouin pump and signal waves are drawn from the filtered amplified spontaneous emission of an erbium-doped fiber amplifier, providing high spatial resolution. The reconstruction of the position-dependent Brillouin gain spectra along 5 cm of a silica single-mode fiber under test, with a spatial resolution of 4 mm, is experimentally demonstrated using a 25 GHz-wide amplified spontaneous emission source. A 4 mm-long localized hot spot is identified by the measurements. The uncertainty in the reconstruction of the local Brillouin frequency shift is ± 1.5 MHz. The single correlation peak between the pump and signal is scanned along a fiber under test using a mechanical variable delay line. The analysis of the expected spatial resolution and the measurement signal-to-noise ratio is provided. The measurement principle is supported by numerical simulations of the stimulated acoustic field as a function of position and time. Unlike most other Brillouin optical correlation domain analysis configurations, the proposed scheme is not restricted by the bandwidth of available electro-optic modulators, microwave synthesizers, or pattern generators. Resolution is scalable to less than one millimeter in highly nonlinear media. PMID:24921326

  20. What Does "Highly Qualified" Mean for Student Achievement? Evaluating the Relationships between Teacher Quality Indicators and At-Risk Students' Mathematics and Reading Achievement Gains in First Grade

    ERIC Educational Resources Information Center

    Phillips, Kristie J. R.

    2010-01-01

    Policymakers and researchers continue to search for ways to improve K-12 education, which has led to an increased focus on teacher quality as an impetus for educational improvement. As such, current legislation under No Child Left Behind (NCLB) calls for highly qualified teachers in every classroom. But are the characteristics associated with…

  1. Lower weight gain and hepatic lipid content in hamsters fed high fat diets supplemented with white rice protein, brown rice protein, and soy protein and their hydrolysates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The physiological effects of the hydrolysates from white rice, brown rice, and soy isolate were compared to the original protein source. White rice, brown rice, and soy protein were hydrolyzed with the food grade enzyme, alcalase2.4 L®. Male Syrian hamsters were fed high-fat diets containing eithe...

  2. Effect of undulations on spontaneous braid formation.

    PubMed

    Lee, Dominic

    2013-08-01

    This paper is an extension of a recent study where it was shown that forces dependent on molecular helical structure may cause two DNA molecules to spontaneously braid [R. Cortini et al., Biophys. J. 101, 875 (2011)]. Here, bending fluctuations of molecular center lines about the braid axis are incorporated into the braiding theory, which may be generalized to other helix-dependent interactions and other helical molecules. The free energy of the pair of molecules is recalculated and compared to its value without incorporating undulations. We find that the loss of configurational entropy due to confinement of the molecules in the braid is quite high. This contribution to the free energy increases the amount of attraction needed for spontaneous braiding due to helix-dependent forces. The theory will be further developed for plectonemes and braids under mechanical forces in later work. PMID:24032876

  3. Spontaneous stress fractures of the femoral neck

    SciTech Connect

    Dorne, H.L.; Lander, P.H.

    1985-02-01

    The diagnosis of spontaneous stress fractures of the femoral neck, a form of insufficiency stress fracture, can be missed easily. Patients present with unremitting hip pain without a history of significant trauma or unusual increase in daily activity. The initial radiographic features include osteoporosis, minor alterations of trabecular alignment, minimal extracortical or endosteal reaction, and lucent fracture lines. Initial scintigraphic examinations performed in three of four patients showed focal increased radionuclide uptake in two and no focal abnormality in one. Emphasis is placed on the paucity of early findings. Evaluation of patients with persistent hip pain requires a high degree of clinical suspicion and close follow-up; the sequelae of undetected spontaneous fractures are subcapital fracture with displacement, angular deformity, and a vascular necrosis of the femoral head.

  4. Perturbed and spontaneous regional cerebral blood flow responses to changes in blood pressure after high-level spinal cord injury: the effect of midodrine

    PubMed Central

    Phillips, Aaron A.; Krassioukov, Andrei V.; Ainslie, Philip N.

    2014-01-01

    Individuals with spinal cord injury (SCI) above the T6 spinal segment suffer from orthostatic intolerance. How cerebral blood flow (CBF) responds to orthostatic challenges in SCI is poorly understood. Furthermore, it is unclear how interventions meant to improve orthostatic tolerance in SCI influence CBF. This study aimed to examine 1) the acute regional CBF responses to rapid changes in blood pressure (BP) during orthostatic stress in individuals with SCI and able-bodied (AB) individuals; and 2) the effect of midodrine (alpha1-agonist) on orthostatic tolerance and CBF regulation in SCI. Ten individuals with SCI >T6, and 10 age- and sex-matched AB controls had beat-by-beat BP and middle and posterior cerebral artery blood velocity (MCAv, PCAv, respectively) recorded during a progressive tilt-test to quantify the acute CBF response and orthostatic tolerance. Dynamic MCAv and PCAv to BP relationships were evaluated continuously in the time domain and frequency domain (via transfer function analysis). The SCI group was tested again after administration of 10 mg midodrine to elevate BP. Coherence (i.e., linearity) was elevated in SCI between BP-MCAv and BP-PCAv by 35% and 22%, respectively, compared with AB, whereas SCI BP-PCAv gain (i.e., magnitudinal relationship) was reduced 30% compared with AB (all P < 0.05). The acute (i.e., 0–30 s after tilt) MCAv and PCAv responses were similar between groups. In individuals with SCI, midodrine led to improved PCAv responses 30–60 s following tilt (10 ± 3% vs. 4 ± 2% decline; P < 0.05), and a 59% improvement in orthostatic tolerance (P < 0.01). The vertebrobasilar region may be particularly susceptible to hypoperfusion in SCI, leading to increased orthostatic intolerance. PMID:24436297

  5. Perturbed and spontaneous regional cerebral blood flow responses to changes in blood pressure after high-level spinal cord injury: the effect of midodrine.

    PubMed

    Phillips, Aaron A; Krassioukov, Andrei V; Ainslie, Philip N; Warburton, Darren E R

    2014-03-15

    Individuals with spinal cord injury (SCI) above the T6 spinal segment suffer from orthostatic intolerance. How cerebral blood flow (CBF) responds to orthostatic challenges in SCI is poorly understood. Furthermore, it is unclear how interventions meant to improve orthostatic tolerance in SCI influence CBF. This study aimed to examine 1) the acute regional CBF responses to rapid changes in blood pressure (BP) during orthostatic stress in individuals with SCI and able-bodied (AB) individuals; and 2) the effect of midodrine (alpha1-agonist) on orthostatic tolerance and CBF regulation in SCI. Ten individuals with SCI >T6, and 10 age- and sex-matched AB controls had beat-by-beat BP and middle and posterior cerebral artery blood velocity (MCAv, PCAv, respectively) recorded during a progressive tilt-test to quantify the acute CBF response and orthostatic tolerance. Dynamic MCAv and PCAv to BP relationships were evaluated continuously in the time domain and frequency domain (via transfer function analysis). The SCI group was tested again after administration of 10 mg midodrine to elevate BP. Coherence (i.e., linearity) was elevated in SCI between BP-MCAv and BP-PCAv by 35% and 22%, respectively, compared with AB, whereas SCI BP-PCAv gain (i.e., magnitudinal relationship) was reduced 30% compared with AB (all P < 0.05). The acute (i.e., 0-30 s after tilt) MCAv and PCAv responses were similar between groups. In individuals with SCI, midodrine led to improved PCAv responses 30-60 s following tilt (10 ± 3% vs. 4 ± 2% decline; P < 0.05), and a 59% improvement in orthostatic tolerance (P < 0.01). The vertebrobasilar region may be particularly susceptible to hypoperfusion in SCI, leading to increased orthostatic intolerance. PMID:24436297

  6. Inhibitory effects of levetiracetam on the high-voltage-activated L-type Ca²? channels in hippocampal CA3 neurons of spontaneously epileptic rat (SER).

    PubMed

    Yan, Hai-Dun; Ishihara, Kumatoshi; Seki, Takahiro; Hanaya, Ryosuke; Kurisu, Kaoru; Arita, Kazunori; Serikawa, Tadao; Sasa, Masashi

    2013-01-01

    Levetiracetam (LEV) is a widely used antiepileptic agent for partial refractory epilepsy in humans. LEV has unique antiepileptic effects in that it does not inhibit electroshock- or pentylenetetrazol-induced convulsion, but does inhibit seizures in kindling animal and spontaneously epileptic rat (SER: zi/zi, tm/tm) that shows both tonic convulsion and absence-like seizures. LEV also has unique characteristics in terms of its antiepileptic mechanism; it has no activity on Na? and K? channels or on glutamate and GABA(A) receptors. Recently, we found that LEV inhibits the depolarization shift and accompanying repetitive firing induced by mossy fiber stimulation in CA3 neurons of SER hippocampal slices. Therefore, this study was performed to determine whether LEV could inhibit the voltage-activated L-type Ca²? current of hippocampal CA3 neurons obtained from SER and the non-epileptic Wistar rat. As previously reported, SER CA3 neurons were classified into type 1 and type 2 neurons. The application of LEV (100 ?M) elevated the threshold for activation of the Ca²? current, which was lowered in SER type 1 neurons and reduced the current size. Type 2 neurons of SER have a similar current-voltage relationship to Wistar rat neurons and the decay component of Ca²? current during depolarization pulse in type 2 neurons was found to be smaller than that in Wistar rat neurons. LEV (100 ?M) also reduced Ca²? current in SER type 2 neurons. The effects of LEV were examined on such type 2 SER hippocampal CA3 neurons, compared with those on Wistar rat CA3 neurons. Application of LEV (10 ?M) produced a significant decrease of amplitude of the Ca²? current in SER neurons, although at this concentration of LEV there was no statistically significant decrease in the amplitude of Ca²? current in Wistar rat neurons. Furthermore, LEV (100 nM-1 mM) reduced the Ca²? current in a concentration-dependent manner in both SER and Wistar rat neurons, but the inhibition was much more potent in the former neurons than in the latter. Under the condition that the Ca²? current had already been inhibited by LEV (10 ?M), the addition of nifedipine (10 ?M) did not cause further inhibition. Conversely, LEV had no effects on the current that had already been decreased by nifedipine (10 ?M) given before LEV treatment (10 ?M), indicating that LEV could act on the L-type Ca²? channel. LEV elevated the threshold potential level for activation of the Ca²? current and reduced the L-type Ca²? current in type 1 neurons of SER, and the inhibitory action in type 2 neurons was much more potent than that in Wistar rat neurons, suggesting that these effects contribute, at least partly, to the antiepileptic action of LEV. PMID:23107646

  7. Hearing Aid Evaluation: Predicting Speech Gain from Insertion Gain.

    ERIC Educational Resources Information Center

    Dillon, Harvey

    1993-01-01

    This study, involving 11 older males with mild or moderate sensorineural loss, tested whether speech gain that results from a hearing aid fitting is predictable on the basis of unaided performance intensity curve, unaided narrow-band sound field thresholds, hearing aid insertion gain as a function of frequency, ambient noise, and internal hearing…

  8. Gain and linewidth enhancement factor in InAs quantum-dot laser diodes

    Microsoft Academic Search

    T. C. Newell; D. J. Bossert; A. Stintz; B. Fuchs; K. J. Malloy; L. F. Lester

    1999-01-01

    Amplified spontaneous emission measurements are investigated below threshold in InAs quantum-dot lasers emitting at 1.22 ?m. The dot layer of the laser was grown in a strained quantum well (QW) on a GaAs substrate. Ground state gain is determined from cavity mode Fabry-Perot modulation. As the injection current increases, the gain rises super-linearly while changes in the index of refraction

  9. Project GAIN Evaluation: 1969-70.

    ERIC Educational Resources Information Center

    Biller, Julian

    Project GAIN was designed to meet the special needs of the academically retarded junior high school student. This federally funded project has been on-going in Broward County (Florida) since January 1966. The project was conceived of as a means to motivate and educate those students whose "dull normal" intellectual ability might otherwise doom…

  10. The Relationship among Spontaneity, Impulsivity, and Creativity

    ERIC Educational Resources Information Center

    Kipper, David A.; Green, Doreen J.; Prorak, Amanda

    2010-01-01

    The present study was designed to investigate two characteristics of spontaneity, its relationship to creativity and to impulsivity. We hypothesized a positive relationship between spontaneity and creativity, consistent with Moreno, 1953 "canon of spontaneity-creativity." We also predicted a negative relationship between spontaneity and…

  11. Edge-facet pumped, multi-aperture, thin-disk laser geometry for very high average power output scaling

    DOEpatents

    Zapata, Luis E.

    2004-12-21

    The average power output of a laser is scaled, to first order, by increasing the transverse dimension of the gain medium while increasing the thickness of an index matched light guide proportionately. Strategic facets cut at the edges of the laminated gain medium provide a method by which the pump light introduced through edges of the composite structure is trapped and passes through the gain medium repeatedly. Spontaneous emission escapes the laser volume via these facets. A multi-faceted disk geometry with grooves cut into the thickness of the gain medium is optimized to passively reject spontaneous emission generated within the laser material, which would otherwise be trapped and amplified within the high index composite disk. Such geometry allows the useful size of the laser aperture to be increased, enabling the average laser output power to be scaled.

  12. Reform Agenda Gains Strength

    ERIC Educational Resources Information Center

    Howell, William; West, Martin; Peterson, Paul E.

    2013-01-01

    In this paper the authors identify some of the key findings from the sixth annual "Education Next"-PEPG Survey, a nationally representative sample of U.S. citizens interviewed during April and May of 2012. Highlights include: (1) the Republican tilt of the education views of independents; (2) the especially high marks that Hispanics give their…

  13. Gains in Teacher Quality

    ERIC Educational Resources Information Center

    Goldhaber, Dan; Walch, Joe

    2014-01-01

    The quality of the teacher workforce in the United States is of considerable concern to education stakeholders and policymakers. Numerous studies show that student academic success depends in no small part on access to high-quality teachers. Many pundits point to the fact that in the United States, teachers tend not to be drawn from the top of the…

  14. Pulsed-Periodic Generation of Laser on SR I and SR II Transitions With High Gain Under Conditions of Ionization and Recombination Plasma Inhomogeneity

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Mirza, S. Yu.; Polunin, Yu. P.; Shumeiko, A. S.

    2014-03-01

    Parametrical investigations of pulsed-periodic strontium vapor laser are carried out. Conditions of simultaneous generation on strontium atom and ion transitions (? = 1.03 and 1.09 ?m; 2.69, 2.6, 2.92, 3.01 and 3.06 ?m; and 6.45 ?m) formed during the period of ionization plasma inhomogeneity on the leading front of the excitation pulse and on strontium ion transitions (? = 416.2 and 430.5 nm) formed during the period of recombination plasma inhomogeneity in the near afterglow of the discharge are determined. Simultaneous generation is understood as the presence of all generation lines per excitation period of high-voltage pulsed-periodic discharge in one resonator whose nontransmitting mirror has the reflection coefficient ?90% and a CaF2 plane-parallel plate without deposited coating is used as an output mirror.

  15. Analytical framework for gain scheduling

    Microsoft Academic Search

    Wilson J. Rugh

    1991-01-01

    The gain scheduling approach to the control of nonlinear systems is explained, and its characteristics are examined. On the basis of this framework questions are raised, and implications are drawn for practical design situations. The relationship between the gain scheduling formulation and the extended-linearization approach for nonlinear control design is considered

  16. Gain of circularly polarised arrays composed of linearly polarised elements

    NASA Astrophysics Data System (ADS)

    Hall, P. S.; Huang, J.; Rammos, E.; Roederer, A.

    1989-01-01

    The gain of circularly polarized (CP) array antennas realized by proper phasing of sequentially rotated linearly polarized (LP) elements is compared to that of arrays using CP elements and demonstrated by calculations for microstrip patch elements. When element spacing is large and array size is small, the advantages of LP elements are offset by the significant reduction in gain due to high cross polarized lobes in the diagonal planes. For large arrays of closely spaced elements, this gain loss reduces to a negligible amount. However, for spacings above a critical value of about 0.7 wavelengths, unacceptably high gain losses will be incurred.

  17. Quantum theory of magnetic bremsstrahlung gain

    Microsoft Academic Search

    Robert Deck; Peter Gill

    1982-01-01

    We present a quantum electrodynamic calculation of the gain associated with the stimulated emission and absorption of photons by high-energy electrons in the presence of a spatially periodic, static magnetic field. The calculation is relevant to the description of a high-energy electron laser in the long-interaction-length low-density (single-particle) regime. The different kinematic constraints imposed on the photon-emission and -absorption processes

  18. Soft x-ray laser gain measurements in a recombining plasma column

    SciTech Connect

    Suckewer, S.; Skinner, C.H.; Milchberg, H.; Keane, C.; Voorhees, D.

    1985-03-01

    An enhancement of approx. 100 of stimulated emission over spontaneous emission of the CVI 182 A line (one-pass gain approx. = 6.5) was measured in a recombining, magnetically confined plasma column by two independent techniques using intensity calibrated XUV monochromators. Additional confirmation that the enhancement was due to stimulated emission has been obtained with a soft x-ray mirror.

  19. Geotech Smart24 data acquisition system input terminated noise seismic response adjusted test : StreckeisenSTS2-low and high gain, Guralp CMG3T and Geotech GS13 seismometers.

    SciTech Connect

    Rembold, Randy Kai; Hart, Darren M.; Harris, James Mark

    2008-08-01

    Sandia National Laboratories has tested, evaluated and reported on the Geotech Smart24 data acquisition system with active Fortezza crypto card data signing and authentication in SAND2008-. One test, Input Terminated Noise, allows us to characterize the self-noise of the Smart24 system. By computing the power spectral density (PSD) of the input terminated noise time series data set and correcting for the instrument response of different seismometers, the resulting spectrum can be compared to the USGS new low noise model (NLNM) of Peterson (1996), and determine the ability of the matched system of seismometer and Smart24 to be quiet enough for any general deployment location. Four seismometer models were evaluated: the Streckeisen STS2-Low and High Gain, Guralp CMG3T and Geotech GS13 models. Each has a unique pass-band as defined by the frequency band of the instrument corrected noise spectrum that falls below the new low-noise model.

  20. An investigation of the factors associated with interpretation of mine atmosphere for spontaneous combustion in coal mines

    Microsoft Academic Search

    A. Adamus; J. Šancer; P. Gu?anová; V. Zubi?ek

    2011-01-01

    The risk of spontaneous combustion of coal is highly serious especially in gaseous underground coal mines. In many cases such a spontaneous combustion is a source of initiation of methane-explosive mixture with tragic consequences. Early indication of spontaneous combustion and determination of its seat temperature is in a given environment a key part of safety of underground coal mines. A

  1. Competence effects for choices involving gains and losses

    Microsoft Academic Search

    José Guilherme de Lara Resende; George Wu

    2010-01-01

    We investigate how choices for uncertain gain and loss prospects are affected by the decision maker’s perceived level of knowledge\\u000a about the underlying domain of uncertainty. Specifically, we test whether Heath and Tversky’s (J Risk Uncertain 4:5–28, 1991) competence hypothesis extends from gains to losses. We predict that the commonly-observed preference for high knowledge\\u000a over low knowledge prospects for gains

  2. [Intracranial tuberculoma with spontaneous recovery].

    PubMed

    Nakajima, H; Ashida, K; Yamasaki, H; Shinoda, K; Ohsawa, N

    1995-05-01

    A 57-year-old man was admitted because of headache, nausea, and fever up (38 degrees C). He showed nuchal rigidity slightly. CSF analysis showed 833 white blood cells (WBC) (80% monocyte), protein value of 68 mg/dl, glucose level of 36 mg/dl and ADA level of 11.8 IU/l. Brain pre-contrast CT indicated high density area in right parietal lobe, and it showed slightly homogeneously enhancement with contrast medium. MRI on T2 WI demonstrated hypointense lesion with bright central core in right parietal lobe. The lesion showed isointense on T1WI, and indicated homogeneous enhancement with Gd-DTPA. He was sent to our hospital after one week. With only antibiotics the symptoms were relieved and the CSF findings improved during the previous hospital. However, Mycobacterium tuberculosis (M. tuberculosis) DNA was detected in CSF by PCR amplification, and he recovered completely with anti-tuberculous treatment. This case was interesting to reveal atypical features of spontaneous recovery. Since Shankar's study using polymerase chain reaction (PCR) for detection of M. tuberculosis in cerebrospinal fluid (CSF), the PCR assay have been recognized to be a rapid method for diagnosis of tuberculous meningitis (TBM). But there are problems of PCR sensitivity when dealing with CSF samples containing small amount of M. tuberculosis DNA. Comparing direct PCR with nested PCR, we studied on the evaluation of PCR for diagnosis of TBM. In this study the nested PCR was positive in all CSF specimens from 4 patients with TBM, but we could not detect M. tuberculosis DNA by only the direct PCR. Nested PCR amplification improved the sensitivity and specificity.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7664522

  3. Functional Connectivity in MRI Is Driven by Spontaneous BOLD Events.

    PubMed

    Allan, Thomas W; Francis, Susan T; Caballero-Gaudes, Cesar; Morris, Peter G; Liddle, Elizabeth B; Liddle, Peter F; Brookes, Matthew J; Gowland, Penny A

    2015-01-01

    Functional brain signals are frequently decomposed into a relatively small set of large scale, distributed cortical networks that are associated with different cognitive functions. It is generally assumed that the connectivity of these networks is static in time and constant over the whole network, although there is increasing evidence that this view is too simplistic. This work proposes novel techniques to investigate the contribution of spontaneous BOLD events to the temporal dynamics of functional connectivity as assessed by ultra-high field functional magnetic resonance imaging (fMRI). The results show that: 1) spontaneous events in recognised brain networks contribute significantly to network connectivity estimates; 2) these spontaneous events do not necessarily involve whole networks or nodes, but clusters of voxels which act in concert, forming transiently synchronising sub-networks and 3) a task can significantly alter the number of localised spontaneous events that are detected within a single network. These findings support the notion that spontaneous events are the main driver of the large scale networks that are commonly detected by seed-based correlation and ICA. Furthermore, we found that large scale networks are manifestations of smaller, transiently synchronising sub-networks acting dynamically in concert, corresponding to spontaneous events, and which do not necessarily involve all voxels within the network nodes oscillating in unison. PMID:25922945

  4. Functional Connectivity in MRI Is Driven by Spontaneous BOLD Events

    PubMed Central

    Allan, Thomas W.; Francis, Susan T.; Caballero-Gaudes, Cesar; Morris, Peter G.; Liddle, Elizabeth B.; Liddle, Peter F.; Brookes, Matthew J.; Gowland, Penny A.

    2015-01-01

    Functional brain signals are frequently decomposed into a relatively small set of large scale, distributed cortical networks that are associated with different cognitive functions. It is generally assumed that the connectivity of these networks is static in time and constant over the whole network, although there is increasing evidence that this view is too simplistic. This work proposes novel techniques to investigate the contribution of spontaneous BOLD events to the temporal dynamics of functional connectivity as assessed by ultra-high field functional magnetic resonance imaging (fMRI). The results show that: 1) spontaneous events in recognised brain networks contribute significantly to network connectivity estimates; 2) these spontaneous events do not necessarily involve whole networks or nodes, but clusters of voxels which act in concert, forming transiently synchronising sub-networks and 3) a task can significantly alter the number of localised spontaneous events that are detected within a single network. These findings support the notion that spontaneous events are the main driver of the large scale networks that are commonly detected by seed-based correlation and ICA. Furthermore, we found that large scale networks are manifestations of smaller, transiently synchronising sub-networks acting dynamically in concert, corresponding to spontaneous events, and which do not necessarily involve all voxels within the network nodes oscillating in unison. PMID:25922945

  5. Multiple genetic switches spontaneously modulating bacterial mutability

    PubMed Central

    2010-01-01

    Background All life forms need both high genetic stability to survive as species and a degree of mutability to evolve for adaptation, but little is known about how the organisms balance the two seemingly conflicting aspects of life: genetic stability and mutability. The DNA mismatch repair (MMR) system is essential for maintaining genetic stability and defects in MMR lead to high mutability. Evolution is driven by genetic novelty, such as point mutation and lateral gene transfer, both of which require genetic mutability. However, normally a functional MMR system would strongly inhibit such genomic changes. Our previous work indicated that MMR gene allele conversion between functional and non-functional states through copy number changes of small tandem repeats could occur spontaneously via slipped-strand mis-pairing during DNA replication and therefore may play a role of genetic switches to modulate the bacterial mutability at the population level. The open question was: when the conversion from functional to defective MMR is prohibited, will bacteria still be able to evolve by accepting laterally transferred DNA or accumulating mutations? Results To prohibit allele conversion, we "locked" the MMR genes through nucleotide replacements. We then scored changes in bacterial mutability and found that Salmonella strains with MMR locked at the functional state had significantly decreased mutability. To determine the generalizability of this kind of mutability 'switching' among a wider range of bacteria, we examined the distribution of tandem repeats within MMR genes in over 100 bacterial species and found that multiple genetic switches might exist in these bacteria and may spontaneously modulate bacterial mutability during evolution. Conclusions MMR allele conversion through repeats-mediated slipped-strand mis-pairing may function as a spontaneous mechanism to switch between high genetic stability and mutability during bacterial evolution. PMID:20836863

  6. Lot sizing with inventory gains

    E-print Network

    2006-11-23

    end of period t is a strictly positive rational multiplier or gain, µt > 0. If one ...... LISCOS: Large Scale Integrated Supply Chain Optimization Software Based on ... Prentice Hall. ... nuclear power plant refueling with mixed-integer programming.

  7. Eating Out and Weight Gain

    MedlinePLUS Videos and Cool Tools

    ... Videos & Tools You Are Here: Home ? Latest Health News ? Eating Out and Weight Gain URL of this page: http://www.nlm.nih.gov/medlineplus/videos/news/Eating_Out_070615.html Eating Out and Weight ...

  8. Full state-resolved energy gain profiles of CO2 from collisions with highly vibrationally excited molecules. II. Energy-dependent pyrazine (E = 32,700 and 37,900 cm(-1)) relaxation.

    PubMed

    Du, Juan; Sassin, Nicholas A; Havey, Daniel K; Hsu, Kailin; Mullin, Amy S

    2013-11-21

    The full state-resolved distribution of scattered CO2 (00(0)0) molecules from collisions with highly vibrationally excited pyrazine (E = 32,700 cm(-1)) is reported and compared to previous studies on pyrazine (E = 37,900 cm(-1)) to investigate how internal energy content impacts the dynamics for collisional quenching of high energy molecules [J. Phys. Chem. A 2010, 113, 1569]. Nascent rotational and translational energy profiles for scattered CO2 (00(0)0) molecules with J = 2-72 were measured using high-resolution transient infrared absorption and combined with earlier results for the J = 56-78 states [J. Chem. Phys. 1999, 111, 7373]. The product translational energy for individual J-states increases by 50% for a 16% increase in donor vibrational energy. The nascent rotational distribution for scattered CO2 is biexponential, comprising 77% nearly elastic collisions and 23% inelastic collisions. The spread of the rotational distribution is sensitive to donor energy, but the branching ratio for elastic and inelastic collisions is the same for both donor energies. The measured collision rates are close to the Lennard-Jones values and are only weakly dependent on changes in donor energy. The nascent energy gain distribution function P(?E) depends strongly on the energy, and this energy dependence is stronger than the linear dependence seen in multicollision energy transfer studies for pyrazine(E) + CO2 collisions. PMID:24063656

  9. In vivo two-photon imaging of mouse hippocampal neurons in dentate gyrus using a light source based on a high-peak power gain-switched laser diode

    PubMed Central

    Kawakami, Ryosuke; Sawada, Kazuaki; Kusama, Yuta; Fang, Yi-Cheng; Kanazawa, Shinya; Kozawa, Yuichi; Sato, Shunichi; Yokoyama, Hiroyuki; Nemoto, Tomomi

    2015-01-01

    In vivo two-photon microscopy is an advantageous technique for observing the mouse brain at high resolution. In this study, we developed a two-photon microscopy method that uses a 1064-nm gain-switched laser diode-based light source with average power above 4 W, pulse width of 7.5-picosecond, repetition rate of 10-MHz, and a high-sensitivity photomultiplier tube. Using this newly developed two-photon microscope for in vivo imaging, we were able to successfully image hippocampal neurons in the dentate gyrus and obtain panoramic views of CA1 pyramidal neurons and cerebral cortex, regardless of age of the mouse. Fine dendrites in hippocampal CA1 could be imaged with a high peak-signal-to-background ratio that could not be achieved by titanium sapphire laser excitation. Finally, our system achieved multicolor imaging with neurons and blood vessels in the hippocampal region in vivo. These results indicate that our two-photon microscopy system is suitable for investigations of various neural functions, including the morphological changes undergone by neurons during physiological phenomena. PMID:25798313

  10. High gain free electron laser at ETA

    SciTech Connect

    Orzechowski, T.J.; Prosnitz, D.; Halbach, K.; Kuenning, R.; Paul, A.; Hopkins, D.; Sessler, A.; Stover, G.; Tanabe, J.; Wurtele, J.

    1983-02-09

    A single pass, tapered electron wiggler and associated beam transport has been constructed at the Experimental Test Accelerator (ETA) at Lawrence Livermore National Laboratory (LLNL). The system is designed to transport 1 kA of 4.5 MeV electrons with an emittance of 30 millirad-cm. The planar wiggler is provided by a pulsed electromagnet. The interaction region is an oversized rectangular waveguide. Quadrupole fields stabilize the beam in the plane parallel to the wiggler field. The 3 meter long wiggler has a 9.8 cm period. The Free Electron Laser (FEL) will serve as an amplifier for input frequencies of 35 GHz and 140 GHz. The facility is designed to produce better than 500 Megawatts peak power.

  11. The Role of Morphology and Electronic Chain Aggregation on the Optical Gain Properties of Semiconducting Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Lampert, Zachary Evan

    Conjugated polymers (CPs) are a novel class of materials that exhibit the optical and electrical properties of semiconductors while still retaining the durability and processability of plastics. CPs are also intrinsically 4-level systems with high luminescence quantum efficiencies making them particularly attractive as organic gain media for solid-state laser applications. However, before CPs can emerge as a commercially available laser technology, a more comprehensive understanding of the morphological dependence of the photophysics is required. In this thesis, the morphology and chain conformation dependence of amplified spontaneous emission (ASE) and optical gain in thin films of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) was investigated. By changing the chemical nature of the solvent from which films were cast, as well as the temperature at which films were annealed, CP films with different morphologies, and hence different degrees of interchain interactions were achieved. Contrary to the common perception that polymer morphology plays a decisive role in determining the ASE behavior of thin CP films, we found that chromophore aggregation and degree of conformational order have minimal impact on optical gain. In fact, experimental results indicated that an extremely large fraction of interchain aggregate species and/or exciton dissociating defects are required to significantly alter the optical properties and suppress stimulated emission. These results are pertinent to the fabrication and optimization of an electrically pumped laser device, as improvements in charge carrier mobility through controlled increases in chain aggregation may provide a viable means of optimizing injection efficiency without significantly degrading optical gain. To offset charge-induced absorption losses under electrical pumping, and to enable the use of more compact and economical sources under optical pumping, conjugated polymers exhibiting low lasing thresholds and large net gains are highly desirable. In this thesis, we also discuss novel routes we developed for enhancement of ASE performance in MEH-PPV thin film planar waveguides. The first technique relied on improving the distribution of the TE0 guided mode in the CP gain layer through optimization of waveguide architecture. This was achieved by fabricating symmetric heterostructure waveguides formed from a core layer of MEH-PPV sandwiched between an SiO2 buffer and index matched poly(methyl methacrylate) (PMMA) cover layer. Relative to asymmetric waveguides of Si(100)/SiO2/MEH-PPV/Air, symmetric waveguides exhibited increased optical confinement and reduced propagation loss enabling lower ASE threshold (40%) and higher net gain (50%). Independent of device architecture and degree of aggregation in the films, we discovered that optical gain is also highly dependent on the excitation conditions, specifically the temporal width of the pump laser pulses. A 400% increase in net gain was achieved under transient (25 picosecond pulses), compared to quasi-steady state (8 nanosecond pulses), excitation conditions. This large difference is attributed to low pumping efficiency and increased non-radiative recombination under ns pumping, which reduces the emission cross-section resulting in a net decrease in gain. The gain values we achieved in the ps regime are to the best of our knowledge the largest gain values reported to date for thin conjugated polymer films measured using the variable stripe length (VSL) technique. Films pumped in the transient regime also required 30 times less pump energy density to reach threshold in comparison with films pumped in the quasi-steady state regime, although the excited state densities were essentially the same. These results demonstrate that the pumping efficiency, and hence generation rate of excited states in a gain medium, can be dramatically increased by using pump laser pulses that are shorter than the exciton luminescence lifetime

  12. Mitigation of pulsed RFI via automatic gain control

    NASA Technical Reports Server (NTRS)

    Chang, R. W.-S.; Weinberg, A.

    1981-01-01

    Three automatic gain control (AGC) strategies and their potential capabilities for mitigation of pulsed radio frequency interference (RFI) over a coded, nonlinear channel are examined. The first updates the AGC control voltage once each symbol interval in accordance with a prespecified criterion. The second implementation is designed to first detect high level RFI and then appropriately update its gain. The final implementation is a wideband device which updates its gain once each symbol interval by reducing the gain in direct proportion to a suitable power measurement. Computed results treat pulsed noise and pulsed CW RFI and compare performances in terms of bit error rate (BER) at the output of a Viterbi decoder.

  13. Can false memories spontaneously recover?

    PubMed

    Seamon, John G; Berko, Jeffrey R; Sahlin, Brooke; Yu, Yi-Lo; Colker, Jennifer M; Gottfried, David H

    2006-05-01

    Can false memories that were suppressed at one time spontaneously recover at a later time? Fuzzy trace theory and activation-monitoring theory predict that false memories in the Deese, Roediger, and McDermott (DRM) procedure become substantially reduced as list learning progresses because participants employ a memory-editing process. It follows that if the editing process is rendered less effective, false memories should spontaneously recover. We found that after DRM lists were well learned and false recognition to critical words was substantially reduced by multiple study-test trials, those false memories spontaneously recovered when participants were either rushed or delayed on a retest. We attributed the reduction in false recognition over trials to a memory-editing process that suppresses false recognition as participants gradually learn which words were in the lists and which words, though similar, were not. Rushing or delaying the participants on a retest made it more difficult for them to edit their memory, and false memories spontaneously returned. PMID:16766445

  14. Spontane oder traumatische tödliche subarachnoidalblutung

    Microsoft Academic Search

    U. Klages

    1970-01-01

    The literature referring to spontaneous or post-traumatic subarachnoid hemorrhage and to lesions of the basal cerebral arteries was compiled and evaluated. Cases with civil (compensatory) or criminal implications were particularly emphasized, as were cases suited for differential diagnosis. A total of 100 cases of subarachnoid hemorrhage is reported; of this ten were presumably associated with blunt injury to the head.

  15. Spontaneous pneumomediastinum and diabetic ketoacidosis.

    PubMed

    O'Sullivan, A J; Casey, J H

    1997-03-01

    Spontaneous pneumomediastinum is a rare complication of diabetic ketoacidosis. We report two patients with this complication who presented to a Sydney hospital within one week. Although both patients were young backpackers, staying at the same hostel, we believe this was coincidental. PMID:9076268

  16. Sloppiness in spontaneously active neuronal networks.

    PubMed

    Panas, Dagmara; Amin, Hayder; Maccione, Alessandro; Muthmann, Oliver; van Rossum, Mark; Berdondini, Luca; Hennig, Matthias H

    2015-06-01

    Various plasticity mechanisms, including experience-dependent, spontaneous, as well as homeostatic ones, continuously remodel neural circuits. Yet, despite fluctuations in the properties of single neurons and synapses, the behavior and function of neuronal assemblies are generally found to be very stable over time. This raises the important question of how plasticity is coordinated across the network. To address this, we investigated the stability of network activity in cultured rat hippocampal neurons recorded with high-density multielectrode arrays over several days. We used parametric models to characterize multineuron activity patterns and analyzed their sensitivity to changes. We found that the models exhibited sloppiness, a property where the model behavior is insensitive to changes in many parameter combinations, but very sensitive to a few. The activity of neurons with sloppy parameters showed faster and larger fluctuations than the activity of a small subset of neurons associated with sensitive parameters. Furthermore, parameter sensitivity was highly correlated with firing rates. Finally, we tested our observations from cell cultures on an in vivo recording from monkey visual cortex and we confirm that spontaneous cortical activity also shows hallmarks of sloppy behavior and firing rate dependence. Our findings suggest that a small subnetwork of highly active and stable neurons supports group stability, and that this endows neuronal networks with the flexibility to continuously remodel without compromising stability and function. PMID:26041916

  17. Galileo mission planning for Low Gain Antenna based operations

    Microsoft Academic Search

    R. Gershman; K. L. Buxbaum; J. M. Ludwinski; B. G. Paczkowski

    1994-01-01

    The Galileo mission operations concept is undergoing substantial redesign, necessitated by the deployment failure of the High Gain Antenna, while the spacecraft is on its way to Jupiter. The new design applies state-of-the-art technology and processes to increase the telemetry rate available through the Low Gain Antenna and to increase the information density of the telemetry. This paper describes the

  18. Modeling and simulation of net energy gain by dark fermentation

    Microsoft Academic Search

    Karnayakage Rasika J. Perera; Yalini Arudchelvam; Venkataramana Gadhamshetty; Nagamany Nirmalakhandan

    For dark fermentation (DF) to be accepted as a sustainable process for biohydrogen production, the net energy gain should be positive and as high as possible. A theoretical approach is proposed in this study to evaluate the net energy gain possible from hydrogen generated by the DF process as well as from the end products of DF via anaerobic digestion

  19. Psychological Adjustment of Adolescents Attempting to Lose or Gain Weight.

    ERIC Educational Resources Information Center

    Rosen, James C.; And Others

    1987-01-01

    Compared the psychological adjustment of high school boys and girls trying to reduce or gain weight. Reducers of both sexes and male gainers exhibited lower physical self-esteem. Girls trying to change weight in either direction showed depression and lower global self-esteem. Girls' decisions to gain or lose weight were influenced by psychological…

  20. Optical Gain and Stimulated Emission in Nanocrystal Quantum Dots

    Microsoft Academic Search

    V. I. Klimov; A. A. Mikhailovsky; Su Xu; A. Malko; J. A. Hollingsworth; C. A. Leatherdale; H.-J. Eisler; M. G. Bawendi

    2000-01-01

    The development of optical gain in chemically synthesized semiconductor nanoparticles (nanocrystal quantum dots) has been intensely studied as the first step toward nanocrystal quantum dot lasers. We examined the competing dynamical processes involved in optical amplification and lasing in nanocrystal quantum dots and found that, despite a highly efficient intrinsic nonradiative Auger recombination, large optical gain can be developed at