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1

Simulation of amplified spontaneous emission in high gain KrF laser amplifiers  

NASA Astrophysics Data System (ADS)

High gain KrF amplifier simulations require a realistic model of amplified spontaneous emission (ASE). We have recently developed an accurate three-dimensional time-dependent code to model ASE and parasitic oscillations in the Nike and Electra amplifiers. It currently includes arbitrary specular reflections at all of the walls and can be easily extended to nonspecular reflections. It can also simulate the ASE that would be seen by another amplifier stage or a camera located outside the amplifier module. The code approximates the ASE light by a discrete set of ordinates or quasi-plane waves whose propagation vectors represent all directions, but cluster preferentially around the amplifier axis, where the gain is highest. At each grid point, it updates the directed intensity by adding an analytic solution of the radiation transport equation within time increment ?t to the earlier intensity at a ``local look-back'' (LLB) point; this point is located a distance c?t back along the ordinate's characteristic direction. Because the LLB does not generally lie at a grid point, interpolation is required to calculate the earlier flux. Trilinear interpolation is simple and computationally fast, but it can introduce numerical spatial diffusion in the specific intensity. This diffusion is usually tolerable, but it can be a significant limitation if one attempts to treat a problem where the operating conditions or ASE viewing position favor a narrow range of directions that are not parallel to one of the Cartesian axes. For those conditions, we use an alternative interpolation scheme based on the flux-corrected transport algorithm, which previously has been used only to treat shock wave propagation in fluids. This article describes the code in detail, then shows ASE simulations illustrating the code's capabilities and the effects of transient excitation, diffusion, and gain narrowing.

Lehmberg, R. H.; Giuliani, J. L.

2003-07-01

2

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

DOEpatents

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.

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

3

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

DOEpatents

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.

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

4

Minimization of the impact of a broad bandwidth high-gain nonlinear preamplifier to the amplified spontaneous emission pedestal of the Vulcan petawatt laser facility  

Microsoft Academic Search

To generate petawatt pulses using the Vulcan Nd:glass laser requires a broad bandwidth high-gain preamplifier. The preamplifier used is an optical parametric amplifier that provides a total gain of 108 in three amplification stages. We report on a detailed investigation of the effect of the Vulcan optical parametric chirped pulse amplification (OPCPA) preamplifier on contrast caused by the amplified spontaneous

I. O. Musgrave; C. Hernandez-Gomez; D. Canny; J. Collier; R. Heathcote

2007-01-01

5

Quantum-to-classical transition via fuzzy measurements on high-gain spontaneous parametric down-conversion  

SciTech Connect

We consider the high-gain spontaneous parametric down-conversion in a noncollinear geometry as a paradigmatic scenario to investigate the quantum-to-classical transition by increasing the pump power, that is, the average number of generated photons. The possibility of observing quantum correlations in such a macroscopic quantum system through dichotomic measurement will be analyzed by addressing two different measurement schemes, based on different dichotomization processes. More specifically, we will investigate the persistence of nonlocality in an increasing size (n/2)-spin singlet state by studying the change in the correlations form as n increases, both in the ideal case and in presence of losses. We observe a fast decrease in the amount of Bell's inequality violation for increasing system size. This theoretical analysis is supported by the experimental observation of macro-macro correlations with an average number of photons of about 10{sup 3}. Our results shed light on the practical extreme difficulty of observing nonlocality by performing such a dichotomic fuzzy measurement.

Vitelli, Chiara; Spagnolo, Nicolo [Dipartimento di Fisica, 'Sapienza' Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Toffoli, Lorenzo [Dipartimento di Fisica, 'Sapienza' Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Sciarrino, Fabio [Dipartimento di Fisica, 'Sapienza' Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Istituto Nazionale di Ottica Applicata, Largo Fermi 6, I-50125 Firenze (Italy); De Martini, Francesco [Dipartimento di Fisica, 'Sapienza' Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Accademia Nazionale dei Lincei, via della Lungara 10, I-00165 Roma (Italy)

2010-03-15

6

Minimization of the impact of a broad bandwidth high-gain nonlinear preamplifier to the amplified spontaneous emission pedestal of the Vulcan petawatt laser facility.  

PubMed

To generate petawatt pulses using the Vulcan Nd:glass laser requires a broad bandwidth high-gain preamplifier. The preamplifier used is an optical parametric amplifier that provides a total gain of 10(8) in three amplification stages. We report on a detailed investigation of the effect of the Vulcan optical parametric chirped pulse amplification (OPCPA) preamplifier on contrast caused by the amplified spontaneous emission (ASE) pedestal that extends up to 2 ns before the arrival of the main pulse. The contrast after compression is improved to 4x10(8) of the intensity of the main pulse using near-field apertures between the stages of the OPCPA preamplifier. Further reduction of the level of the ASE pedestal can be achieved at the cost of a reduction in amplified bandwidth by solely phosphate glass amplification after initial preamplification rather than a mixed glass amplification scheme. PMID:17906727

Musgrave, I O; Hernandez-Gomez, C; Canny, D; Collier, J; Heathcote, R

2007-10-01

7

Helicopter high gain control  

NASA Technical Reports Server (NTRS)

High gain control is explored through a design study of the CH-47B helicopter. The plans are designed to obtain the maximum bandwidth possible given the hardware constraints. Controls are designed with modal control theory to specific bandwidths and closed loop mode shapes. Comparisons are made to an earlier complementary filter approach. Bandwidth improvement by removal of limitations is explored in order to establish hardware and mechanization options. Improvements in the pitch axis control system and in the rate gyro sensor noise characteristics in all axes are discussed. The use of rotor state feedback is assessed.

Cunningham, T. B.; Nunn, E. C.

1979-01-01

8

Dynamic high gain observer design  

Microsoft Academic Search

A dynamic high gain based observer is proposed for the class of uniformly observable systems which are observable for any inputs. The main feature of this observer consists in an appropriate calibration of the observation gain through a single parameter governed by some scalar Riccati equation. Simulation results are given in order to highlight the performances of the proposed observer,

M. Farza; M. M'Saad; M. Oueder; L. Sellami; R. Ben Abdennour

2009-01-01

9

High gain observers with updated gain and homogeneous correction terms  

Microsoft Academic Search

Exploiting dynamic scaling and homogeneity in the bi-limit, we develop a new class of high gain observers which incorporate a gain update law and nonlinear output error injection terms. A broader class of systems can be addressed and the observer gain is better fitted to the incremental rate of the nonlinearities. The expected improved performance is illustrated.

V. Andrieu; L. Praly; Alessandro Astolfi

2009-01-01

10

Recent Progress in High-Gain FEL Theory  

SciTech Connect

High-gain free electron lasers (FEL) are being developed as extremely bright x-ray sources of a next-generation radiation facility. In this paper, we review the basic theory and the recent progress in understanding the startup, the exponential growth and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emission (SASE). We will also discuss how the FEL performance may be affected by various errors and wakefield effects in the undulator.

Huang, Z.; /SLAC

2005-09-30

11

Unidirectional high gain brake stop  

NASA Technical Reports Server (NTRS)

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.

Lang, David J. (Inventor)

1987-01-01

12

High Gain Observer Design for Eth Helicopter  

Microsoft Academic Search

This paper deals with the design of a high gain observer (HGO) for the ETH helicopter laboratory process. The standard format of high gain observer is used and the parameters of the observer are selected in such away that the observer gain matrix H0 becomes Hurwitz. The observer not only estimates the angular positions and velocities of the system but

Naeem Ullah; A. Qayyum Khan; Ghulam Mustafa; M. Yousuf

2006-01-01

13

Integrated High-Gain Active Radar Augmentor.  

National Technical Information Service (NTIS)

A compact and integrated high-gain radar augmented system, including: a cylindrical microstrip receive antenna mounted on a cylinder for providing nominal omni-directional coverage, a transmit antenna similar to the receive antenna mounted on the same cyl...

J. M. DeVries

1983-01-01

14

Numerical differentiation using high-gain observers  

Microsoft Academic Search

High-gain observers have been used in nonlinear control to estimate the derivatives of the output. In this paper, we study discrete-time implementation of high-gain observers and their use as numerical differentiators. We show that discretization using the bilinear transformation method gives results better than other discretization methods. We also show that many of the available numerical differentiators are special cases

Ahmed Dabroom; H. K. Khalil

1997-01-01

15

High-gain magnetized inertial fusion.  

PubMed

Magnetized inertial fusion (MIF) could substantially ease the difficulty of reaching plasma conditions required for significant fusion yields, but it has been widely accepted that the gain is not sufficient for fusion energy. Numerical simulations are presented showing that high-gain MIF is possible in cylindrical liner implosions based on the MagLIF concept [S. A. Slutz et al Phys. Plasmas 17, 056303 (2010)] with the addition of a cryogenic layer of deuterium-tritium (DT). These simulations show that a burn wave propagates radially from the magnetized hot spot into the surrounding much denser cold DT given sufficient hot-spot areal density. For a drive current of 60 MA the simulated gain exceeds 100, which is more than adequate for fusion energy applications. The simulated gain exceeds 1000 for a drive current of 70 MA. PMID:22324693

Slutz, Stephen A; Vesey, Roger A

2012-01-13

16

High-Gain Magnetized Inertial Fusion  

NASA Astrophysics Data System (ADS)

Magnetized inertial fusion (MIF) could substantially ease the difficulty of reaching plasma conditions required for significant fusion yields, but it has been widely accepted that the gain is not sufficient for fusion energy. Numerical simulations are presented showing that high-gain MIF is possible in cylindrical liner implosions based on the MagLIF concept [S. A. Slutz et al Phys. Plasmas 17, 056303 (2010)PHPAEN1070-664X10.1063/1.3333505] with the addition of a cryogenic layer of deuterium-tritium (DT). These simulations show that a burn wave propagates radially from the magnetized hot spot into the surrounding much denser cold DT given sufficient hot-spot areal density. For a drive current of 60 MA the simulated gain exceeds 100, which is more than adequate for fusion energy applications. The simulated gain exceeds 1000 for a drive current of 70 MA.

Slutz, Stephen A.; Vesey, Roger A.

2012-01-01

17

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

Microsoft Academic Search

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

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

18

High-gain MOS tunnel emitter transistors  

NASA Astrophysics Data System (ADS)

Tunnel emitter transistors (TETs) are promising devices for high-current-density, high-frequency applications. The excellent CMOS compatibility of the TET makes it an ideal candidate to replace the bipolar junction transistors in BiCMOS technology; however, many properties of the TET are still under investigation. In this paper we present TETs with the highest current gain ever reported, 500-800. The effect of oxide quality on device performance is also described, and how the device characteristics can be improved by post-metallization annealing. Finally, we observe enhanced gain due to collector-emitter avalanching.

Aderstedt, Erik; Medugorac, Igor; Lundgren, Per

2002-04-01

19

Tapered fiber amplifier with high gain and output power  

NASA Astrophysics Data System (ADS)

We present a high-power ytterbium fiber amplifier based on active tapered double-clad fiber (T-DCF) and capable of high single-pass gain. The T-DCF power amplifier seeded with a 320 mW narrow-band signal generates up to 110 W of average output power corresponding to more than 25 dB gain. The amplifier exhibits near-diffraction-limited beam quality ( M 2 = 1.06) at the highest output power, which was limited by the available pump power. With a broadband seed source, the amplifier produced a gain of nearly 40 dB obtained for low-signal limit of the seed. The high output power combined with high gain is achieved owing to amplified spontaneous emission (ASE) filtering and increased stimulated Brillouin scattering (SBS) threshold inherent to the axially non-uniform geometry. The amplifier operates efficiently with a wide range of input seed powers thus providing the basis for one-stage tapered amplifier which combines the functions of preamplifier and power amplifier and can be a competitive alternative to multi-stage design.

Kerttula, J.; Filippov, V.; Chamorovskii, Y.; Ustimchik, V.; Golant, K.; Okhotnikov, O. G.

2012-11-01

20

High gain observers based on immersion technics  

Microsoft Academic Search

The high gain observer based on normal forms is initially proposed in. These normal forms characterize single input uniformly observable systems (systems which are observable independently on the input). Next, in, this observable normal form together with observer synthesis have been extended to a class of MIMO nonlinear systems by assuming that some regular flag of co-distribution does not depend

Hassan Hammouri; Basil Ucchueddu

2010-01-01

21

The High Gain Free Electron Lasers  

Microsoft Academic Search

This dissertation is composed of two independent parts on a theoretical study of the high gain free electron laser. In the first part (Chapters 2-4) a non-linear (saturation) regime of the free electron lasers (FELs) with electromagnetic wigglers is described. Two opposite configurations for the wiggler field propagation direction are considered in a unified manner. The wiggler field propagating counter

Yoonho Seo; Yoonho

1989-01-01

22

High gain flux compression generator fabrication issues  

Microsoft Academic Search

The fabrication issues involved with a high gain helical flux compression generator are discussed. The generator is 20 cm in diameter, 76 cm long, contains 4500 gm of explosives, and its desired output is 2 million amperes into a 200-nH load. The goal is to attain better than 1000 X current multiplication. To achieve this goal great attention must be

J. L. Cutting; D. K. Abe; J. B. Chase; R. S. Hawke; P. A. Pincosy; H. T. Takemori; M. L. Fillipucci

1989-01-01

23

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

SciTech Connect

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)

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

24

Ramelteon attenuates age-associated hypertension and weight gain in spontaneously hypertensive rats.  

PubMed

The neuroendocrine theory of aging suggests the common mechanisms of developmental (prereproductive) and aging (postreproductive) processes and identified a cluster of conditions (hypertension, obesity, dyslipidemia, type 2 diabetes, menopause, late onset depression, vascular cognitive impairment, impairment of immune defense, and some forms of cancer) as age-associated neuroendocrine disorders (AAND). Obesity, dyslipidemia, hypertension, and type 2 diabetes were later described as metabolic syndrome (MetS). Because melatonin attenuated development of MetS is age-dependent, that is, in young and old, but not in middle-aged rats, we studied the effect of the selective melatonin agonist, Ramelteon, on the two core symptoms of MetS/AAND: hypertension and body weight gain in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto male rats (WKY). SHR rats developed hypertension at the time of maximal weight gain that coincided with the onset of reproductive activity (8-10 weeks old). Chronic (but not acute) administration of Ramelteon (in drinking water, 8 mg/kg/day, from 4 to 12 weeks of age) attenuated age-associated increase of systolic blood pressure (tail-cuff method) by 45%, and age-associated body weight gain by 30%. Acute and chronic Ramelteon did not affect blood pressure and body weight in normotensive WKY rats. Ramelteon-induced attenuation of age-associated hypertension and weight gain suggests that Ramelteon might attenuate the other symptoms of MetS/AAND and might be useful in the treatment of MetS/AAND during puberty, menopause, and old age. PMID:20633116

Oxenkrug, Gregory F; Summergrad, Paul

2010-06-01

25

High-gain observers in the presence of measurement noise: A nonlinear gain approach  

Microsoft Academic Search

This paper studies a high-gain observer with a nonlinear gain. The nonlinearity is chosen to have a higher observer gain during the transient period and a lower gain afterwards, thus overcoming the tradeoff between fast state reconstruction and measurement noise attenuation. The observer is designed such that the behavior of the innovation process can be controlled separately from the other

Alexis Amanda Ball; Hassan K. Khalil

2008-01-01

26

High gain selective metal organic framework preconcentrators  

US Patent & Trademark Office Database

Novel metal organic framework (MOF) molecules and methods of synthesizing them are described. MOFs are organometallic crystalline structures that have high sorption capacity due to high surface area, tailorable selectivity, an inert nature, and thermal stability at high temperatures. MOFs may be used as sorbents in preconcentrators for analytical devices to provide orders of magnitude of improved sensitivity in analyte detection. MOFs are also useful as sorbents in new compact and portable micropreconcentrator designs such as a modified purge and trap system and a multi-valve microelectromechanical system (MEMS) to achieve high gain in analyte detection. Further, MOFs may be used as coatings for novel microstructure arrays in micropreconcentrators where the microstructures are designed to increase the surface area to volume ratio inside the micropreconcentrator while minimizing the pressure drop across the micropreconcentrator.

2012-02-28

27

High gain observer with updated gain for a class of MIMO nonlinear systems  

Microsoft Academic Search

A high gain like observer with an updated gain is proposed for a class of MIMO nonlinear systems that are observable for any inputs. The main contribution of this article lies in the nature of the observer gain that involves a scalar time-varying design parameter governed by some scalar Riccati equation. This time-varying design parameter, chosen constant in standard high

M. Farza; M. Oueder; R. Ben Abdennour; M. MSaad

2011-01-01

28

Ignition and high gain with ultrapowerful lasers  

SciTech Connect

Ultrahigh intensity lasers can potentially be used in conjunction with conventional fusion lasers to ignite inertial confinement fusion (ICF) capsules with a total energy of a few tens of kilojoules of laser light, and can possibly lead to high gain with as little as 100 kJ. A scheme is proposed with three phases. First, a capsule is imploded as in the conventional approach to inertial fusion to assemble a high-density fuel configuration. Second, a hole is bored through the capsule corona composed of ablated material, as the critical density is pushed close to the high-density core of the capsule by the ponderomotive force associated with high-intensity laser light. Finally, the fuel is ignited by suprathermal electrons, produced in the high-intensity laser--plasma interactions, which then propagate from critical density to this high-density core. This new scheme also drastically reduces the difficulty of the implosion, and thereby allows lower quality fabrication and less stringent beam quality and symmetry requirements from the implosion driver. The difficulty of the fusion scheme is transferred to the technological difficulty of producing the ultrahigh-intensity laser and of transporting this energy to the fuel.

Tabak, M.; Hammer, J.; Glinsky, M.E.; Kruer, W.L.; Wilks, S.C.; Woodworth, J.; Campbell, E.M.; Perry, M.D. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)); Mason, R.J. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1994-05-01

29

Time-varying high-gain observers for numerical differentiation  

Microsoft Academic Search

In this paper, we propose high-gain numerical differentiators for estimating the higher derivatives of a given signal. We consider time varying high-gain vectors converging exponentially to the high-gain vectors introduced by F. Esfandiari and K.H. Khalil (1992) in an earlier paper. The dynamics of these time-varying high-gain vectors can be chosen in order to achieve specific objectives, such as peaking

Yacine Chitour

2002-01-01

30

On the performance of high-gain observers with gain adaptation under measurement noise  

Microsoft Academic Search

We address the problem of state observation for a system whose dynamics may involve poorly known, perhaps even nonlocally Lipschitz functions and whose output measurement may be corrupted by noise. It is known that one way to cope with all these uncertainties and noise is to use a high-gain observer with a gain adapted on-line. The proposed method, while presented

Ricardo G. Sanfelice; Laurent Praly

2011-01-01

31

High-gain observers in the presence of measurement noise: A switched-gain approach  

Microsoft Academic Search

This paper considers output feedback control using high-gain observers in the presence of measurement noise for a class of nonlinear systems. We study stability in the presence of measurement noise and illustrate the tradeoff when selecting the observer gain between state reconstruction speed and robustness to model uncertainty on the one hand versus amplification of noise on the other. Based

Jeffrey H. Ahrens; Hassan K. Khalil

2009-01-01

32

Updating the gain of global finite-time high gain observers  

Microsoft Academic Search

Recently, new results about semi-global and global finite-time observation have been obtained by the use of continuous high gain observers. In this paper, we propose to extend these results by studying “time-varying high gain” observers and by providing new update laws: first, we adapt the law introduced by L. Praly in the case of asymptotic observation to the finite-time case

Laurent Burlion; Tarek Ahmed-Ali; Francoise Lamnabhi-Lagarrigue

2011-01-01

33

High-gain observers in nonlinear feedback control  

Microsoft Academic Search

The theory of high-gain observers has been developed for about twenty years. This paper is a brief introduction to high-gain observers in nonlinear feedback control, with emphasis on the peaking phenomenon and the role of control saturation in dealing with it. The paper surveys recent results on the nonlinear separation principle, conditional servo compensators, extended high-gain observers, performance in the

Hassan K. Khalil

2008-01-01

34

High-gain observers in nonlinear feedback control  

Microsoft Academic Search

Summary form only given. The theory of high-gain observers has been developed for about twenty years. This talk is a brief introduction to high-gain observers in nonlinear feedback control, with emphasis on the peaking phenomenon and the role of control saturation in dealing with it. The talk surveys recent results on the nonlinear separation principle, extended high-gain observers, performance in

Hassan K. Khalil

2009-01-01

35

High upconversion optical gain of Er3+-doped tellurite glass  

NASA Astrophysics Data System (ADS)

The upconversion technique of rare-earth-doped glasses or crystals is a potential route for achieving short-wavelength lasers (SWLs). The optical gain is an important parameter for evaluating lasing medium performance. Therefore, upconversion luminescence in glass with composition of 70TeO2-9PbF2-10AlF3-10BaF2-1Er2O3 was demonstrated, and the small-signal optical gain was measured via an amplified spontaneous emission technique when the sample was excited with a 980 nm laser. It was found that the optical gain was as large as 4.0 dB/cm, thus indicating that this glass may be a good medium for SWLs.

Fu, S. B.; Chen, B. J.; Zhang, J. S.; Li, X. P.; Zhong, H.; Tian, B. N.; Wang, Y. Z.; Sun, M.; Zhang, X. Q.; Cheng, L. H.; Zhong, H. Y.; Xia, H. P.

2014-06-01

36

Circular polarization with crossed-planar undulators in high gain FELs.  

SciTech Connect

We propose a crossed undulator configuration for a high-gain free-electron laser to allow versatile polarization control. This configuration consists of a long (saturation length) planar undulator, a dispersive section, and a short (a few gain lengths) planar undulator oriented perpendicular to the first one. In the first undulator, a radiation component linearly polarized in the x-direction is amplified to saturation. In the second undulator, the x-polarized component propagates freely, while a new component, polarized in the y-direction, is generated and reaches saturation in a few gain lengths. By adjusting the strength of the dispersive section, the relative phase of two radiation components can be adjusted to obtain a suitable polarization for the total radiation field, including the circular polarization. The operating principle of the high-gain crossed undulator, which is quite different from that of the crossed undulator for spontaneous radiation, is illustrated in terms of 1-D FEL theory.

Kim, K.-J.

1999-08-31

37

An adaptive high-gain observer for nonlinear systems  

Microsoft Academic Search

In this paper the authors provide a solution to the noise sensitivity of high-gain observers. The resulting nonlinear observer possesses simultaneously (1) extended Kalman filter’s good noise filtering properties, and (2) the reactivity of the high-gain extended Kalman filter with respect to large perturbations.The authors introduce innovation as the quantity that drives the gain adaptation. They prove a general convergence

Nicolas Boizot; Eric Busvelle; Jean-Paul Gauthier

2010-01-01

38

Design of a high-gain flux-compression generator  

Microsoft Academic Search

The current gain of a high gain, high explosive helical magnetic-flux-compression generator (HEG) is limited both by nonuniformities in stator expansion and by armature-stator misalignment. Three goals were explored: (1) an output current of at least 2 MA with a current gain greater than 1000 to drive a 150- to 300-nH load; (2) a generator with an acceptably small volume

P. A. Pincosy; D. K. Abe; J. B. Chase

1989-01-01

39

Nonlinear sliding mode high-gain observers for fault estimation  

Microsoft Academic Search

A robust high gain observer for state and unknown inputs\\/faults estimations for a special class of nonlinear systems is developed in this article. Ensuring the observability of the faults\\/unknown inputs with respect to the outputs, the faults can be estimated from the sliding surface. Under a Lipschitz condition for the nonlinear part, the high gain observers are designed under some

K. C. Veluvolu; M. Y. Kim; D. Lee

2011-01-01

40

Nonlinear sliding mode high-gain observers for fault detection  

Microsoft Academic Search

A robust high gain observer for state and faults estimations for a special class of nonlinear systems is developed in this article. Ensuring the observability of the faults with respect to the outputs, the faults can be estimated from the sliding surface. Under a Lipschitz condition for the nonlinear part, the high gain observers are designed under some regularity assumptions.

K. C. Veluvolu; F. Zhe; Y. C. Soh

2010-01-01

41

High gain observer: attenuation of the peak phenomena  

Microsoft Academic Search

In many problems of estimation, the high gain technique is used to compensate for nonlinear terms in order to guarantee the convergence of the estimator. However, the use of the high gain generally generates the so-called peak phenomena (at the beginning, the estimated trajectory deviates from the desired one). We extend the observer stated in J. P. Gauthier et al.

E. H. El Yaagoubi; A. El Assoudi; H. Hammouri

2004-01-01

42

Soft-switching interleaved boost converter with high voltage gain  

Microsoft Academic Search

In this paper a soft-switching interleaved boost converter with high voltage gain is presented. The high voltage gain converter is far suitable for applications where a high step-up voltage is required, as in some renewable energy systems, which use, for example, photovoltaic panels and\\/or fuel cells. Besides, in order to guarantee small switching losses and, consequently, a high efficiency, a

R. N. A. L. Silva; G. A. L. Henn; P. P. Praca; L. H. S. C. Barreto; D. S. Oliveira Jr; F. L. M. Antunes

2008-01-01

43

High gain fractal-based Yagi antenna  

Microsoft Academic Search

In this paper, a new high directivity wire antenna based on the modified 2nd iteration space-filling Peano curve is used as an element in a Yagi-Uda array for WIMAX and WIFI applications. A three elements feeder- reflector-director arrangement is proposed. The whole antenna structure including; the reflector, the feeder and the director has been analyzed and optimized using a full-wave

Essam A. El-khouly; Hani A. Ghali

2008-01-01

44

A Low Noise High Gain Bandwidth Charge Sensitive Preamplifier  

Microsoft Academic Search

The concept of the charge sensitive amplifier is discussed and a novel method for obtaining a high gain amplifier stage through the use of a positive current feedback dynamic plate load is described. It is shown that under certain conditions this type of feedback can provide increased bandwidth as well as increased low frequency gain. The schematic of a preamplifier

Jack Hahn; Ralph Mayer

1962-01-01

45

A high gain array antenna with serially fed dipole elements  

Microsoft Academic Search

In this paper, a planar array antenna is proposed to maximize its gain performance, which is critical to point-to-point communications. Comparing to conventional parabolic reflectors, the planar array antenna is a cost effective alternative since the printed circuit board fabrication process can be adopted. However, the major drawback in the design of high gain array antenna is the losses in

Wen-Jiao Liao; Shen-Je You

2010-01-01

46

High-gain observer design for loop transfer recovery  

Microsoft Academic Search

A systematic procedure of designing a high-gain observer which achieves asymptotic loop transfer recovery is given. The method allows assignment of different time-scales to an observer while permitting a chosen eigenstructure in each time-scale.

A. Saberi; P. Sannuti

1987-01-01

47

An adaptive high-gain observer for nonlinear systems  

Microsoft Academic Search

In this paper we present a high-gain observer for a general class of nonlinear SISO systems for which the high-gain parameter is determined on-line in an adaptive fashion. The adaptation scheme is simple and universal in the sense that it is independent of the system the observer is designed for. We prove that the observer output error becomes smaller than

Eric Bullinger; Frank Allgower

1997-01-01

48

Highly charged ion energy gain spectroscopy of molecular excitations  

NASA Astrophysics Data System (ADS)

We show that the measurement at high resolution of the kinetic-energy gain spectrum of a highly charged ion (HCI) scattered and partly neutralised by a molecule, a nanocluster or a surface can reveal the excitation spectrum of the target. As a first application of the analysis, we demonstrate that the periodic oscillations in the measured energy gain spectra of energetic Ar q+ ions flying by C 60 molecules arise from the coherent multiple excitations of C 60 plasmons.

Lucas, A. A.; Benedek, G.; Sunjic, M.; Echenique, P. M.

2010-06-01

49

High gain and high peak power in planar waveguide lasers  

Microsoft Academic Search

We report enhanced peak power and gain for pulses in the 10-100 ?sec range, with specific peak power to 240 kW m-2 of electrode area at frequencies to 4 kHz. Pulsed small signal gain is increased by a factor of 7 relative to cw\\/long pulse excitation

F. J. Villarreal; Q. Cao; R. J. Ramirez; H. J. Baker; D. R. Hall

2001-01-01

50

Gain enhancement in a two-frequency high-gain waveguide free-electron laser  

Microsoft Academic Search

In a waveguide monomode free-electron laser (FEL), two resonant frequencies can be amplified by the electron beam. At the CEA\\/CESTA facility, single-pass high-gain FEL experiments have been performed over the last five years using relativistic electron beams provided by induction linacs. Most of the work was done in the amplifier regime (at the higher frequency) with the aim of producing

T. Lefevre; J. Gardelle; J. L. Rullier; P. Gouard; J. T. Donohue

2002-01-01

51

Superradiance in the high-gain free-electron laser  

Microsoft Academic Search

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

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

1989-01-01

52

High performance quantum cascade lasers with broadband gain spectra  

NASA Astrophysics Data System (ADS)

QC laser active regions with multiple transitions from strongly coupled upper laser states to lower laser states were designed to achieve broad gain spectra as well as high performance. Two broad gain QC laser designs in the 7-9 ?m wavelength region were demonstrated based on the continuum-to-bound design. The first embodiment of one design at ~8 ?m enables external cavity tuning over 190 cm-1 (7.5 - 8.8 ?m) in pulsed mode operation at 0°C. We also demonstrated a QC laser structure based on a continuum-to-continuum active region in the 4-5 ?m wavelength region with a gain spectrum of ~ 430 cm-1. External cavity tuning over 340 cm-1 (4.4 - 5.2 ?m) was achieved with this design in pulsed mode operation at 15°C. In spite of the broad gain spectrum, a low threshold current density (1.6 kA/cm2), large slope efficiency (4.5 W/A), good temperature performance (T0=160 K), high peak power (up to 5 W) and high wall plug efficiency (WPE, up to 20%) were achieved for ridge lasers with as cleaved facets, in pulsed mode operation at 295 K, demonstrating that it is possible to make a wide gain spectrum compatible with high power and efficiency performance.

Yao, Yu; Wang, Xiaojun; Fan, Jen-Yu; Charles, William O.; Tsai, Tracy; Chen, Jianxin; Wysocki, Gerard; Gmachl, Claire F.

2011-02-01

53

A novel bidirectional interleaved boost converter with high voltage gain  

Microsoft Academic Search

In this paper a novel interleaved boost converter with high voltage gain and bidirectional operation is presented. High efficiency and low stress in the switches are expected. The great voltage limit range in bidirectional mode allows that this topology is far suitable for renewable energy systems applications.

G. A. L. Henn; L. H. S. Barreto; D. S. Oliveira; E. A. S. da Silva

2008-01-01

54

Robust Feedback Linearization using Extended High-Gain Observers  

Microsoft Academic Search

We consider a partially feedback linearizable system with stable zero dynamics. The system is uncertain and only the output is measured. Consequently, exact feedback linearization is not applicable. We propose to design an extended high-gain observer to recover unmeasured derivatives of the output and an extra one, which contains information about the uncertainty. The observer can be stabilized via feedback

Leonid B. Freidovich; Hassan K. Khalil

2006-01-01

55

Application of a high gain observer to fault detection  

Microsoft Academic Search

It is well known that model uncertainty in dynamic systems can be expressed in terms of unknown inputs. The purpose of designing a robust observer is then to find a gain matrix which will attenuate the effect of the unknown input. During the last few years many methods have been developed to achieve this. One such method is the high

S. Daley; H. Wang

1993-01-01

56

Further results on high gain observers for nonlinear systems  

Microsoft Academic Search

On the basis of high-gain observers for perturbed state affine systems, an observer for a class of nonlinear systems satisfying a more general triangular structure is proposed. The design is based on interconnection of subobservers on the one hand, and saturation techniques on the other hand. Exponential convergence of the estimation error is shown under appropriate excitation condition

G. Besancon

1999-01-01

57

High gain observer for a class of implicit systems  

Microsoft Academic Search

Under some observability assumptions (uniform observability), a high gain observer for a class of implicit dynamical systems is given. Numerically, the computation of trajectories of such implicit systems usually necessitates the use of an optimization algorithm together with an ODE numerical method. This complicates the synthesis of an observer. The observer design proposed here leads to a classical dynamical system

Abdellatif El Assoudi; E. El Yaagoubi; H. Hammouri

2000-01-01

58

High Gain Observer Design for Some Networked Control Systems  

Microsoft Academic Search

New results on high gain observer design for networked control systems via an emulation-like approach are presented. By using a general framework and a Lyapunov approach, we derive some explicit conditions on the maximum allowable transmission interval that ensure an exponential convergence of the observation error for a large class of network protocols.

Tarek Ahmed-Ali; Françoise Lamnabhi-Lagarrigue

2012-01-01

59

Output Feedback Nonlinear GPC Using High Gain Observer  

Microsoft Academic Search

In this paper, Nonlinear Generalized Predictive Control (NGPC), proposed by Chen [4] in continuous time, is reformulated into a quadratic optimization problem in order to take into account constraints, and this approach is applied to a particular class of nonlinear systems. The states which are assumed available will be estimated in this work by a high gain observer (HGO). The

S. H. Said; F. M'Sahli

2007-01-01

60

Radiation Response of Emerging High Gain, Low Noise Detectors  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

61

Progress on Achieving the ICF Conditions Needed for High Gain.  

National Technical Information Service (NTIS)

Progress during the past two years has moved us much closer to demonstrating the scientific and technological requirements for high gain ICF in the laboratory. This progress has been made possible by operating at the third harmonic of 1 mu m light which d...

J. D. Lindl

1988-01-01

62

Parameter estimation of feedback gain in a stochastic model of renal hemodynamics: differences between spontaneously hypertensive and Sprague-Dawley rats.  

PubMed

Proximal tubular pressure shows periodic self-sustained oscillations in normotensive rats but highly irregular fluctuations in spontaneously hypertensive rats (SHR). Although we have suggested that the irregular fluctuations in SHR represent low-dimensional deterministic chaos in tubuloglomerular feedback (TGF), they could also arise from other mechanisms, such as intrinsic instabilities in preglomerular vessels or inputs from neighboring, coupled nephrons. To test this possibility, we applied a parameter estimation procedure to a model of TGF, where a stochastic process was added to represent mechanisms not included explicitly in the model. In its deterministic version, the model can have chaotic dynamics arising from TGF. The model introduces random fluctuations into a parameter that determines the gain of TGF. The model shows a rich variety of dynamics ranging from low-dimensional deterministic oscillations and chaos to high-dimensional random fluctuations. To fit the data from normotensive rats, the model must introduce only a small variation in the feedback gain, and its estimates of that gain agree well with experimental values. These results support the use of the deterministic model of nephron dynamics in normotensive rats. In contrast, the irregular tubular pressure fluctuations in SHR were best described by a model dominated by random parameter fluctuations. The results point to the failure of simple mathematical models of nephron dynamics adequately to describe processes that are important for the irregular tubular pressure fluctuations and the need to consider other factors, such as differences in vascular function or nephron-nephron interactions, in further work on this problem. PMID:17018842

Ditlevsen, Susanne; Yip, Kay-Pong; Marsh, Donald J; Holstein-Rathlou, Niels-Henrik

2007-02-01

63

High power gain guided index antiguided fiber lasers and amplifiers  

NASA Astrophysics Data System (ADS)

Increasing the core size of high-power fiber lasers and amplifiers is highly desired in order to mitigate the unwanted nonlinear optical effects and raise the optical damage threshold. If the core size of conventional index-guided (IG) optical fibers increases, the fiber will become multimode, because it is very difficult to control and fine-tune the index step between the core and cladding to satisfy the single mode condition. Siegman proposed Gain-guided index-antiguided (GG-IAG) fibers as a possible platform for ultra-large-core single-mode operation for lasers and amplifiers. In this thesis, the beam-quality factor M2 for the fundamental LP01 mode of a step-index fiber with finite and infinite cladding diameter is calculated in the presence of gain as a function of the complex generalized V number. The numerical results agree with analytical work that obtained in our group. It is shown that the M2 value of a single-mode gain-guided fiber laser can be arbitrarily large. The results are important for the interpretation of the beam-quality measurements in recent experiments on single-mode gain-guided fiber lasers. It is also shown that the conventional infinite cladding diameter approximation cannot be used for index-antiguided gain-guided fibers, and the rigorous analysis is required for accurate prediction of the beam quality factor, as reported in recent experimental measurements. We also highlight the key reasons behind the poor power efficiency observed in multiple experiments in gain guided index-antiguided (GG-IAG) fiber amplifiers and lasers. We show that by properly designing the fiber geometrical characteristics, it is possible to considerably improve the power efficiency of GG-IAG fiber amplifiers in end-pumping schemes.

Gandomkar Yarandi, Parisa

64

An integral equation based computer code for high-gain free-electron lasers  

SciTech Connect

A computer code for gain optimization of high-gain free-electron lasers (FELs) is described. The electron motion is along precalculated period-averaged trajectories, and the finite-emittance electron beam is represented by a set of thin partial beams. The radiation field amplitudes are calculated at these thin beams only. The system of linear integral equations for these field amplitudes and the Fourier harmonics of the current of each thin beam is solved numerically. The code is aimed for design optimization of high-gain short-wavelength FELs with nonideal magnetic systems (breaks between undulators with quadrupoles and magnetic bunchers; field and steering errors). Both self-amplified spontaneous emission (SASE) and external input signal options can be treated. A typical run for a UV FEL, several gain lengths long, takes only one minute on a Pentium II personal computer (333 MHz) which makes it possible to run the code in optimization loops. Results for the Advanced Photon Source FEL project are presented.

Dejus, R.J. [Argonne National Lab., IL (United States). Advanced Photon Source; Shevchenko, O.A.; Vinokurov, N.A. [Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation)

1998-09-01

65

Spontaneous high-concentration dispersions and liquid crystals of graphene  

Microsoft Academic Search

Graphene combines unique electronic properties and surprising quantum effects with outstanding thermal and mechanical properties. Many potential applications, including electronics and nanocomposites, require that graphene be dispersed and processed in a fluid phase. Here, we show that graphite spontaneously exfoliates into single-layer graphene in chlorosulphonic acid, and dissolves at isotropic concentrations as high as ~2 mg ml-1, which is an

Natnael Behabtu; Jay R. Lomeda; Micah J. Green; Amanda L. Higginbotham; Alexander Sinitskii; Dmitry V. Kosynkin; Dmitri Tsentalovich; A. Nicholas G. Parra-Vasquez; Judith Schmidt; Ellina Kesselman; Yachin Cohen; Yeshayahu Talmon; James M. Tour; Matteo Pasquali

2010-01-01

66

High-gain 1310-nm reflective semiconductor optical amplifiers with low-gain uncertainty  

Microsoft Academic Search

A 1310-nm reflective semiconductor optical amplifier with a gain uncertainty of only 0.8 dB at an average gain level of over 30 dB has been demonstrated using a microoptic polarization reversing retroreflector. For this amplifier 3-dB saturation output powers of up to 10 dBm and a noise figure of 7.5 dB have been obtained. A low gain uncertainty for undefined

L. F. Tiemeijer; G. N. van den Hoven; P. J. A. Thijs; T. van Dongen; J. J. M. Binsma; E. J. Jansen; A. J. M. Verboven

1997-01-01

67

Observation of high gain in Ne-like Ag lasers  

SciTech Connect

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.

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

68

The UCLA high gain infrared free electron laser  

NASA Astrophysics Data System (ADS)

A high gain SASE FEL amplifier designed to operate in the infrared (near 10 ?m) is being commissioned in the Particle Beam Physics Laboratory at UCLA. The high brightness beam needed to drive the FEL is provided by an RF photocathode gun employing solenoidal emittance compensation. A novel linac (a Plane Wave Transformer) accelerates the beam to a final energy ? 15 MeV. This beam is to be sent through a 60 cm long undulator with a period of 1.5 cm and an undulator parameter K ? 1. Near future experiments will focus on FEL physics relevant to proposed short wavelength devices. Investigations of start-up from noise (SASE), effects of beam parameters on gain as well as noise fluctuations are of particular interest. Here we present an overview of the hardware including relevant diagnostics, measured beam parameters, FEL simulation results and the status of proposed experiments.

Hogan, M.; Pellegrini, C.; Rosenzweig, J.; Travish, G.; Varfolomeev, A. A.

1997-02-01

69

High-Frequency Power Gain in the Mammalian Cochlea  

NASA Astrophysics Data System (ADS)

Amplification in the mammalian inner ear is thought to result from a nonlinear active process known as the cochlear amplifier. Although there is much evidence that outer hair cells (OHCs) play a central role in the cochlear amplifier, the mechanism of amplification remains uncertain. In non-mammalian ears hair bundles can perform mechanical work and account for the active process in vitro, yet in the mammalian cochlea membrane-based electromotility is required for amplification in vivo. A key issue is how OHCs conduct mechanical power amplification at high frequencies. We present a physical model of a segment of the mammalian cochlea that can amplify the power of external signals. In this representation both electromotility and active hair-bundle motility are required for mechanical power gain at high frequencies. We demonstrate how the endocochlear potential, the OHC resting potential, Ca2+ gradients, and ATP-fueled myosin motors serve as the energy sources underlying mechanical power gain in the cochlear amplifier.

Maoiléidigh, Dáibhid Ó.; Hudspeth, A. J.

2011-11-01

70

Approximate high-gain observers for uniformly observable nonlinear systems  

Microsoft Academic Search

A methodolgy for the design of continuous practical observers for nonlinear uniformly observable systems is presented. The system is first transformed into observability normal form, using the observability map semi-diffeomorphism. Since this normal form may have a non-Lipschitz continuous right hand side, a so called ?-approximate high-gain observer is designed for it, constituting the dynamic part of the observer. The

Jaime Moreno; Alejandro Vargas

2000-01-01

71

ZnO Nanowire UV Photodetectors with High Internal Gain  

Microsoft Academic Search

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

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

2007-01-01

72

High-Gain Harmonic-Generation Free-Electron Laser  

Microsoft Academic Search

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

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

73

Design issues for a laboratory high gain fusion facility  

SciTech Connect

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.

Hogan, W.J.

1987-11-02

74

High resolution BPMS with integrated gain correction system  

SciTech Connect

High resolution beam position monitors (BPM) are an essential tool to achieve and reproduce a low vertical beam emittance at the KEK Accelerator Test Facility (ATF) damping ring. The ATF damping ring (DR) BPMs are currently upgraded with new high resolution read-out electronics. Based on analog and digital down-conversion techniques, the upgrade includes an automatic gain calibration system to correct for slow drift effects and ensure high reproducible beam position readings. The concept and its technical realization, as well as preliminary results of beam studies are presented.

Wendt, M.; Briegel, C.; Eddy, N.; Fellenz, B.; Gianfelice, E.; Prieto, P.; Rechenmacher, R.; Voy, D.; /Fermilab; Terunuma, N.; Urakawa, J.; /KEK, Tsukuba

2009-08-01

75

High Gain and Frequency Ultra-Stable Integrators  

NASA Astrophysics Data System (ADS)

Eagle Harbor Technologies has received DOE Phase I SBIR funding to continue the development of high gain and stability integrators that are capable of high bandwidth measurements over long pulse operation. The present design operates with a 10 us RC time, for pulse durations up to the second time scale, with a frequency response in excess of 10 MHz, and typical drift errors of under 10 mV. This integrator development effort consists of two primary tasks. The first is to demonstrate stable operation over the much longer time scales required by ITER. When a proper comparison between available integrator designs is made that normalizes for gain and operation time, the existing integrators are the best available and meet ITER requirements for stability. However, this stability needs to be demonstrated over the hour type time scales relevant to ITER, as opposed to the very high gain second type operation typically used within the ICC community. The second primary task is to incorporate the integrators into the National Instruments (NI) platform to allow for easy operation with modern DAQ systems.

Miller, K. E.; Ziemba, T. M.; Prager, J. R.; Lotz, D. E.

2011-11-01

76

Spontaneous high-concentration dispersions and liquid crystals of graphene.  

PubMed

Graphene combines unique electronic properties and surprising quantum effects with outstanding thermal and mechanical properties. Many potential applications, including electronics and nanocomposites, require that graphene be dispersed and processed in a fluid phase. Here, we show that graphite spontaneously exfoliates into single-layer graphene in chlorosulphonic acid, and dissolves at isotropic concentrations as high as approximately 2 mg ml(-1), which is an order of magnitude higher than previously reported values. This occurs without the need for covalent functionalization, surfactant stabilization, or sonication, which can compromise the properties of graphene or reduce flake size. We also report spontaneous formation of liquid-crystalline phases at high concentrations ( approximately 20-30 mg ml(-1)). Transparent, conducting films are produced from these dispersions at 1,000 Omega square(-1) and approximately 80% transparency. High-concentration solutions, both isotropic and liquid crystalline, could be particularly useful for making flexible electronics as well as multifunctional fibres. PMID:20512130

Behabtu, Natnael; Lomeda, Jay R; Green, Micah J; Higginbotham, Amanda L; Sinitskii, Alexander; Kosynkin, Dmitry V; Tsentalovich, Dmitri; Parra-Vasquez, A Nicholas G; Schmidt, Judith; Kesselman, Ellina; Cohen, Yachin; Talmon, Yeshayahu; Tour, James M; Pasquali, Matteo

2010-06-01

77

Spectral properties of high-gain parametric down-conversion.  

PubMed

High-gain parametric down-conversion (PDC) is a source of bright squeezed vacuum, which is a macroscopic nonclassical state of light and a promising candidate for quantum information applications. Here we study its properties, such as the intensity spectral width and the spectral width of pairwise correlations. In agreement with the theory, we observe an increase in the spectral width by 27% compared with the low-gain PDC. Frequency cross- and auto-correlations are registered by measuring the reduction of noise in the difference of PDC intensities at various pairs of wavelengths. The noise reduction plots also demonstrate super-bunching typical for collinear frequency-degenerate PDC. PMID:22453430

Spasibko, K Yu; Iskhakov, T Sh; Chekhova, M V

2012-03-26

78

A neural amplifier with high programmable gain and tunable bandwidth.  

PubMed

A neural recording amplifier having programmable gain and bandwidth is presented. The gain can be digitally programmed using 6 bits from 100x to 1100x in steps of 100x. The low-frequency cutoff can be varied from less than 10Hz to above 100Hz to accept or reject field potentials while the high-frequency cutoff is fixed at 9kHz. The input referred noise of this amplifier is 4.8microV(rms) and it consumes 50microW operating from +/-1.5V. Implemented in a 0.5microm technology, the amplifier occupies an area of 0.098mm(2). This amplifier has been successfully demonstrated in-vivo and compared to a commercial amplifier. PMID:19163376

Perlin, Gayatri E; Sodagar, Amir M; Wise, Kensall D

2008-01-01

79

Transverse amplified spontaneous emission: The limiting factor for output energy of ultra-high power lasers  

NASA Astrophysics Data System (ADS)

For the new generation of the ultra-high power lasers with tens of PW of output power, kJ-level energies have to be reached. Our modeling, applied to Ti:sapphire amplifiers, demonstrates for the first time, according our knowledge, that Transverse Amplified Spontaneous Emission (TASE) places an additional restriction on storing and extracting energy in larger gain apertures, even stronger than transverse parasitic generation (TPG). Nevertheless, we demonstrate that extracting during pumping (EDP) can significantly reduce parasitic losses due to both TASE and TPG.

Chvykov, Vladimir; Nees, John; Krushelnick, Karl

2014-02-01

80

Collective instabilities and high-gain regime free electron laser  

SciTech Connect

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.

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

1983-01-01

81

Evaluation of an ultrabroadband high-gain amplification technique for chirped pulse amplification facilities.  

PubMed

Recently, an amplification technique for ultrashort pulses was explored in detail in a theoretical paper by Ross et al. [Opt. Commun. 144, 125 (1997)]. The technique, based on nonlinear optics, is called optical parametric chirped pulse amplification. It has a number of features that, in principle, make it highly attractive. It primarily offers extremely large gains simultaneously with extremely large bandwidths. Additional attractions are virtually no spatial and temporal phase distortion of the amplified pulse, high efficiencies and a low thermal loading, reduced amplified spontaneous emission levels, small optical material lengths, and an inherent simplicity of implementation. We present an evaluation of the technique as a front end amplifier for the ultrashort pulse amplification chain of the Vulcan laser system. Such a device could replace some of the existing amplification in Nd:glass and additionally have a wider effect as a direct replacement of Ti:sapphire regenerative amplifiers on large-scale chirped pulse amplification scale facilities. PMID:18324304

Collier, J; Hernandez-Gomez, C; Ross, I N; Matousek, P; Danson, C N; Walczak, J

1999-12-20

82

High gain x-ray lasers pumped by transient collisional excitation  

SciTech Connect

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.

Dunn, J., LLNL

1998-06-16

83

High-gain phototransistors on high-resistivity silicon substrate  

NASA Astrophysics Data System (ADS)

NPN phototransistors have been fabricated on high-purity silicon substrate. The devices have been produced by ITC-IRST in the framework of a National Research Project funded by the Italian Education, University and Research Ministry (MIUR). The phototransistor emitter is composed of a phosphorus n + implant, the base is a diffused high-energy boron implant, and the collector is the 300 ?m thick silicon bulk. Several devices have been investigated. Results with 22 keV X-ray from a 109Cd-radioactive source and visible light irradiation are presented.

Batignani, G.; Bisogni, M. G.; Boscardin, M.; Bosisio, L.; Dalla Betta, G. F.; Del Guerra, A.; Dittongo, S.; Forti, F.; Giorgi, M.; Han, D. J.; Linsalata, S.; Marchiori, G.; Piemonte, C.; Rachevskaia, I.; Ronchin, S.

2004-02-01

84

Where do we stand with high gain FEL simulations?  

SciTech Connect

Computer technology improvements have allowed for more complete and detailed free electron laser simulations, yet the demands of the large number of new experiments and proposed projects has outpaced the capability and availability of present codes. This paper, based on a talk given at the conference of these proceedings, presents a brief assessment of Free Electron Laser (FEL) codes, their availability and features, as well as some opinions on what direction the FEL code community should take for the near future. The discussion of FEL codes is restricted here to ones for high gain amplifiers: no codes for oscillators, waveguides or exotic configurations are considered.

Travish, Gil [Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Milano, Via Cervi, 201. 20090 Segrate (Italy)

1997-06-01

85

STARS A Two Stage High Gain Harmonic Generation FEL Demonstrator  

SciTech Connect

BESSY is proposing a demonstration facility, called STARS, for a two-stage high-gain harmonic generation free electron laser (HGHG FEL). STARS is planned for lasing in the wavelength range 40 to 70 nm, requiring a beam energy of 325 MeV. The facility consists of a normal conducting gun, three superconducting TESLA-type acceleration modules modified for CW operation, a single stage bunch compressor and finally a two-stage HGHG cascaded FEL. This paper describes the faciliy layout and the rationale behind the operation parameters.

M. Abo-Bakr; W. Anders; J. Bahrdt; P. Budz; K.B. Buerkmann-Gehrlein; O. Dressler; H.A. Duerr; V. Duerr; W. Eberhardt; S. Eisebitt; J. Feikes; R. Follath; A. Gaupp; R. Goergen; K. Goldammer; S.C. Hessler; K. Holldack; E. Jaeschke; Thorsten Kamps; S. Klauke; J. Knobloch; O. Kugeler; B.C. Kuske; P. Kuske; A. Meseck; R. Mitzner; R. Mueller; M. Neeb; A. Neumann; K. Ott; D. Pfluckhahn; T. Quast; M. Scheer; Th. Schroeter; M. Schuster; F. Senf; G. Wuestefeld; D. Kramer; Frank Marhauser

2007-08-01

86

Development of high-gain high-efficiency grid-connected inverter for PV Module  

Microsoft Academic Search

This paper proposes a high gain and high efficiency power conditioning system for grid connected PV module. The system consists of a one module of PV, boost converter with high gain transformation ratio, and singlephase H-bridge inverter. The system is suitable for using less number of PV modules or using only one PV module for the grid connection applications which

Omar Abdel-Rahim; Mohamed Orabi; Mahrous E. Ahmed

2010-01-01

87

High-gain parametric amplification for the generation of quantum states of light  

NASA Astrophysics Data System (ADS)

The novel quantum statistical properties of the two- photon entangled states generated by spontaneous parametric downconversion have been utilized in a variety of fourth-order interferometric configurations. The extent to which the intense light produced by an unneeded parametric amplifier (optical parametric generator) retains these desirable properties is explored in a series of calculations. Common fourth-order interferometric configurations using two-photon entangled states are summarized, with an emphasis on the Hong-Ou-Mandel and Mach-Zehnder interferometers. This summary is followed by a review of recent proposals for the exploitation of entangled states for sub-Rayleigh-limit imaging. The limitations of using parametric downconversion at two-photon levels are discussed and the replacement of two-photon interferometric sources with the multiphoton output of a high-gain optical parametric generator is considered. The output of the Hong-Ou-Mandel interferometer, Mach-Zehnder interferometer, and quantum lithography configurations as a function of single-pass gain is determined, and the interpretation of these results in the context of multiple photon pair contributions to interferometric patterns is presented. The analysis of the high-gain optical parametric generator as a fourth-order interferometric source is then extended to the case of multiple signal and idler output modes. The impact of the system transfer characteristics on the desired interferometric properties is discussed. The initiation of beam filamentation by vacuum fluctuations is considered, and this four-wave mixing process is compared to parametric downconversion as a source for fourth-order interferometric applications. We conclude by contrasting the states produced by high- gain optical parametric generation with coherent states and the states produced by seeded optical parametric amplification as sources for fourth-order interferometric configurations.

Nagasako, Elna Mieko

88

Direct drive pellet designs for high gain and NIF  

NASA Astrophysics Data System (ADS)

We are designing and analyzing direct drive icf pellets for application to both high-gain ICF and the 1.6 MJ glass laser National Ignition Facility (NIF). The primary tool for this analysis is the NRL FAST MPI radiation-hydrocode; it runs in one to three dimensions, includes LTE & nonLTE multigroup radiation transport with an STA opacity database, and has fusion burn with multigroup alpha particle transport. The pellets under consideration for direct drive are composed of a variety of ablator materials (plastic, plastic foams wicked with DT, DT, and with and without thin high-Z layers) [S.E. Bodner, D.G. Colombant, A.J. Schmitt, and M. Klapisch, Phys. Plasmas 7, 2298 (2000); D.G. Colombant, et al., Proc. 26th ECLIM 2000, SPIE 4424 224 (2001)]. We present the resulting pellet designs, discuss them in the context of hydrodynamic instability theory, and summarize the simulations of the effects of nonuniformities on gain. Nonuniformity sources that are examined include laser imprint, surface finish imperfections, and low-mode power imbalance due to beam misalignment and pulse jitter.

Schmitt, Andrew J.; Colombant, Denis; Fyfe, David; Gardner, John H.; Velikovich, Alexander

2001-10-01

89

Dual AMP features variable gain and high bandwidth  

NASA Astrophysics Data System (ADS)

Variable-gain amplifiers (VGAs) are important components in many receiver systems. One such VGA design intended for lightwave transmission systems operating at gigabit-per-second rates provides 2.5-GHz bandwidth and 40-dB gain.

Pfund, George; Zhang, Jim; Wu, Jieh-Tsorng

1992-02-01

90

On the spontaneous creation of chromomagnetic fields at high temperature  

SciTech Connect

The spontaneous generation of the chromomagnetic field at high temperature is investigated in a lattice formulation of the SU(2) gluodynamics. The procedure of studying this phenomenon is developed. Monte Carlo simulations of the free energy on the lattices 2 x 8{sup 3}, 2 x 16{sup 3}, and 4 x 8{sup 3} at various temperatures are carried out. The creation of the field is indicated by means of the {chi}{sup 2} analysis of the data set accumulating (5-10) x 10{sup 6} Monte Carlo configurations. A comparison with the results of other approaches is done.

Demchik, V. I., E-mail: vadimdi@yahoo.com; Skalozub, V. V. [Dnepropetrovsk National University (Ukraine)], E-mail: skalozub@ff.dsu.dp.ua

2008-01-15

91

On the spontaneous creation of chromomagnetic fields at high temperature  

SciTech Connect

The spontaneous generation of the chromomagnetic field at high temperature is investigated in a lattice formulation of the SU(2) gluodynamics. The procedure of studying this phenomenon is developed. Monte Carlo simulations of the free energy on the lattices 2 Multiplication-Sign 8{sup 3}, 2 Multiplication-Sign 16{sup 3}, and 4 Multiplication-Sign 8{sup 3} at various temperatures are carried out. The creation of the field is indicated by means of the {chi}{sup 2} analysis of the data set accumulating (5-10) Multiplication-Sign 10{sup 6} Monte Carlo configurations. A comparison with the results of other approaches is done.

Demchik, V. I., E-mail: vadimdi@yahoo.com; Skalozub, V. V., E-mail: skalozub@ff.dsu.dp.ua [Dnepropetrovsk National University (Ukraine)

2008-01-15

92

Critical review of high gain x-ray FEL experiments  

SciTech Connect

There is a renewed interest at the present time to develop x-ray free electron lasers (FELs). The interest is driven by the scientific opportunities with coherent x-rays glimpsed at the third generation light sources. With the recent development in linac technology in producing high-energy, high-brightness electron beams, it is now possible to design intense coherent x-ray source for wavelengths as short as one Angstrom based on the self- amplified spontaneous emission (SASE) principle. Major linac laboratories such as SLAC and DESY are therefore actively pursuing detailed design studies for the x-ray SASE facilities. The x-rays from these facilities will provide a peak brightness more than ten orders of magnitude higher than that of the current synchrotron radiation sources. Short wavelength coherent radiation could also be generated with harmonic generation techniques in linacs or storage rings. However, these schemes are not expected to be effective for 1 {Angstrom} wavelengths. This review will therefore concentrate on the linac based SASE scheme. The critical components of the SASE are: an electron source consisting of an RF photocathode gun with the emittance corrector producing high brightness electron beam; the beam bunching and acceleration; and a long undulator in which the radiation develops from initially incoherent radiation to intense, coherent radiation. We discuss the critical experimental issues in these components highlighting some relevant recent experiments. We also discuss issues related to the SASE experiment which are distinct from the usual free electron lasers. We give a brief survey of the world-wide SASE experiments. We conclude with a summary and outlook.

Kim, Kwang-Je

1996-08-01

93

High-gain, low-noise amplification in olfactory transduction.  

PubMed Central

It is desirable that sensory systems use high-gain, low-noise amplification to convert weak stimuli into detectable signals. Here it is shown that a pair of receptor currents underlying vertebrate olfactory transduction constitutes such a scheme. The primary receptor current is an influx of Na+ and Ca2+ through cAMP-gated channels in the olfactory cilia. External divalent cations improve the signal-to-noise properties of this current, reducing the mean current and the current variance. As Ca2+ enters the cilium, it gates Cl- channels, activating a secondary depolarizing receptor current. This current amplifies the primary current, but introduces little additional noise. The system of two currents plus divalent cations in the mucus produces a large receptor current with very low noise.

Kleene, S J

1997-01-01

94

High gain GaAs photoconductive semiconductor switches: Switch longevity  

SciTech Connect

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.

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

1998-07-01

95

Vibrational temperatures and gain coefficient measurements by using spontaneous radiation data obtained in a shock driven CO2-GDL  

Microsoft Academic Search

A method for determination of vibrational temperatures in vibrationally-nonequilibrated CO2-laser active medium for CO2, CO and NO admixture molecules is developed and described. The determination of vibrational temperatures of CO and NO molecules is based on spontaneous radiation intensity measurements in the 4.7 and 5.3 micron bands respectively and that of CO2 molecules is based on the simultaneous measurement of

N. N. Kudriavtsev; S. S. Novikov

1982-01-01

96

High gain multigap avalanche detectors for Cerenkov ring imaging  

Microsoft Academic Search

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 for

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

1980-01-01

97

Spontaneous Raman scattering as a high resolution XUV radiation source  

NASA Technical Reports Server (NTRS)

A type of high resolution XUV radiation source is described which is based upon spontaneous anti-Stokes scattering of tunable incident laser radiation from atoms excited to metastable levels. The theory of the source is summarized and two sets of experiments using He (1s2s)(1)S atoms, produced in a cw hollow cathode and in a pulsed high power microwave discharge, are discussed. The radiation source is used to examine transitions originating from the 3p(6) shell of potassium. The observed features include four previously unreported absorption lines and several sharp interferences of closely spaced autoionizing lines. A source linewidth of about 1.9 cm(-1) at 185,000 cm(-1) is demonstrated.

Rothenberg, J. E.; Young, J. F.; Harris, S. E.

1983-01-01

98

Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices  

SciTech Connect

Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

Geoffrey Krafft

2005-09-15

99

High-gain nonlinear observer for simple genetic regulation process  

NASA Astrophysics Data System (ADS)

High-gain nonlinear observers occur in the nonlinear automatic control theory and are in standard usage in chemical engineering processes. We apply such a type of analysis in the context of a very simple one-gene regulation circuit. In general, an observer combines an analytical differential-equation-based model with partial measurement of the system in order to estimate the non-measured state variables. We use one of the simplest observers, that of Gauthier et al., which is a copy of the original system plus a correction term which is easy to calculate. For the illustration of this procedure, we employ a biological model, recently adapted from Goodwin's old book by De Jong, in which one plays with the dynamics of the concentrations of the messenger RNA coding for a given protein, the protein itself, and a single metabolite. Using the observer instead of the metabolite, it is possible to rebuild the non-measured concentrations of the mRNA and the protein.

Torres, L. A.; Ibarra-Junquera, V.; Escalante-Minakata, P.; Rosu, H. C.

2007-07-01

100

Fast ignition integrated experiments and high-gain point design  

NASA Astrophysics Data System (ADS)

Integrated fast ignition experiments were performed at ILE, Osaka, and LLE, Rochester, in which a nanosecond driver laser implodes a deuterated plastic shell in front of the tip of a hollow metal cone and an intense ultrashort-pulse laser is injected through the cone to heat the compressed plasma. Based on the initial successful results of fast electron heating of cone-in-shell targets, large-energy short-pulse laser beam lines were constructed and became operational: OMEGA-EP at Rochester and LFEX at Osaka. Neutron enhancement due to heating with a ?kJ short-pulse laser has been demonstrated in the integrated experiments at Osaka and Rochester. The neutron yields are being analysed by comparing the experimental results with simulations. Details of the fast electron beam transport and the electron energy deposition in the imploded fuel plasma are complicated and further studies are imperative. The hydrodynamics of the implosion was studied including the interaction of the imploded core plasma with the cone tip. Theory and simulation studies are presented on the hydrodynamics of a high-gain target for a fast ignition point design.

Shiraga, H.; Nagatomo, H.; Theobald, W.; Solodov, A. A.; Tabak, M.

2014-05-01

101

Lyapunov-based switching control of nonlinear systems using high-gain observers  

Microsoft Academic Search

We consider dynamic output feedback practical stabilization of uniformly observable nonlinear systems, based on high-gain observers with saturation. We assume that uncertain parameters and initial conditions belong to known but comparably large compact sets. In this situation, designs based on traditional robust or adaptive techniques, if applicable, would lead to high controller, observer, and adaptation gains. High gains may excite

Leonid B. Freidovich; Hassan K. Khalil

2005-01-01

102

Spontaneous Raman Scattering Diagnostics for High-Pressure Gaseous Flames  

NASA Technical Reports Server (NTRS)

A high-pressure (up to 60 atm) gaseous burner facility with optical access that provides steady, reproducible flames with high precision, and the ability to use multiple fuel/oxidizer combinations has been developed. In addition, a high-performance spontaneous Raman scattering system for use in the above facility has also been developed. Together, the two systems will be used to acquire and establish a comprehensive Raman scattering spectral database for use as a quantitative high-pressure calibration of single-shot Raman scattering measurements in high-pressure combustion systems. Using these facilities, the Raman spectra of H2-Air flames were successfully measured at pressures up to 20 atm. The spectra demonstrated clear rotational and ro-vibrational Raman features of H2, N2, and H2O. theoretical Raman spectra of pure rotational H2, vibrational H2, and vibrational N2 were calculated using a classical harmonic-oscillator model with pressure broadening effects and fitted to the data. At a gas temperature of 1889 K for a phi = 1.34 H2-Air flame, the model and the data showed good agreement, confirming a ro-vibrational equilibrium temperature.

Kojima, Jun; Nguyen, Quang-Viet; Reddy, D. R. (Technical Monitor)

2002-01-01

103

Analysis of a nonlinear high-gain observer in the presence of measurement noise  

Microsoft Academic Search

Motivated by the sensitivity of high-gain observers to measurement noise, this paper presents a high-gain observer with a nonlinear gain that takes the form of a piecewise linear function. The piecewise function is designed to have three linear regions, with the two outermost sectors chosen to elicit the desired behavior in the transient and steady- state responses, respectively. In order

Alexis A. Ball; Hassan K. Khalil

2011-01-01

104

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)

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.

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

2013-02-01

105

High gain Yagi-Uda UHF RFID tag antennas  

Microsoft Academic Search

In this paper, 5-elements Yagi-Uda type UHF tag antennas, resonated at 915MHz, are designed to increase the gain and FBR (front-back-ratio) of tag antennas and extend the reading range. The designs have better FBR than a conventional Yagi-Uda tag antenna designs.

Kyounghwan Lee; You Chung Chung

2007-01-01

106

Rectangular-bore, high-gain laser plasma tube  

NASA Technical Reports Server (NTRS)

Rectangular-bore tube improves population inversion obtained from upper and terminal laser states, resulting in a significant increase in unsaturated gain factor. Radial field produces efficient pumping of upper laser state. Narrow tube dimensions cause increased diffusion flow of neon is metastable states to tube walls.

Mollo, R. A.

1969-01-01

107

High gain CO chemical laser produced in a shock tunnel  

Microsoft Academic Search

Experimental theoretical results are presented of small signal gain in a CO chemical laser produced in a shock tunnel. The thermal dissociation of CS2 into CS + S is effected by a reflected shock wave. The dissociated products, diluted in Ar, expand through a supersonic nozzle having an area ratio of 40 into a combustion chamber. At the nozzle exit,

M. Tilleman; J. Stricker

1982-01-01

108

Stability in high gain plasmas in DIII-D  

SciTech Connect

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.

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

1996-10-01

109

Stability in High Gain Plasmas in DIII-D  

SciTech Connect

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.

Lazarus, E. A.; Hong, R. M. [Oak Ridge National Lab., TN (United States); Navratil, G. A.; Sabbagh, S. [Columbia Univ., New York, NY (United States); Strait, E. J.; Rice, B. W. [Lawrence Livermore National Lab., CA (United States); Ferron, J. R.; Greenfield, C. M.; Austin, M. E. [Maryland Univ., College Park, MD (United States); Chan, V. S.; DeBoo, J. C.; Doyle, E. J. [California Univ., Los Angeles, CA (United States; Durst, R. [Wisconsin Univ., Madison, WI (United States); Forest, C. B. [California Univ., Irvine, CA (United States); Leonard, A. W. [Oak Ridge Associated Universities, Inc., TN (United States); Schissel, D. P. [JET Joint Undertaking, Abingdon (United Kingdom)

1997-01-01

110

Interleaved-Boost Converter With High Voltage Gain  

Microsoft Academic Search

This paper presents an interleaved-boost converter, magnetically coupled to a voltage-doubler circuit, which provides a voltage gain far higher than that of the conventional boost topology. Besides, this converter has low-voltage stress across the switches, natural-voltage balancing between output capacitors, low-input current ripple, and magnetic components operating with the double of switching frequency. These features make this converter suitable to

Gustavo A. L. Henn; R. N. A. L. Silva; Paulo P. Praca; Luiz H. S. C. Barreto

2010-01-01

111

High gain CO chemical laser produced in a shock tunnel  

NASA Astrophysics Data System (ADS)

Experimental theoretical results are presented of small signal gain in a CO chemical laser produced in a shock tunnel. The thermal dissociation of CS2 into CS + S is effected by a reflected shock wave. The dissociated products, diluted in Ar, expand through a supersonic nozzle having an area ratio of 40 into a combustion chamber. At the nozzle exit, molecular oxygen is injected supersonically. The two streams mix and combustion occurs where vibrationally excited CO is produced by the CS + O - CO (v) + S reaction. Gain measurements of the P7(14) line are made at distances of 5.5 and 11.5 cm downstream of the oxygen injection point, the stagnation pressure being 25 atm. The stagnation temperatures are varied in the range of 2500-4600 K and mixtures of CS2:Ar between 5:95 and 30:70 are tested. A maximum gain of 8% per cm is observed for CS2:Ar = 20:80 at a stagnation temperature of about 4000 K and a distance of 11.5 cm. A semiempirical model describing the fuel-diluent expansion through the supersonic nozzle and the fuel-oxidizer mixing process is then developed.

Tilleman, M.; Stricker, J.

112

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

NASA Astrophysics Data System (ADS)

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 a tracking servo system of an experimental optical disk drive based on a Blu-ray disk drive, and confirmed the decrease in residual tracking error to only 22%. Furthermore, the rotational speed reaches 14500 rpm on an inner track of a disc (r=25 mm).

Mukasa, Tomoharu; Urakawa, Yoshiyuki

2008-07-01

113

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

114

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

NASA Astrophysics Data System (ADS)

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.

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

115

A new soft switching interleaved boost converter with high voltage gain  

Microsoft Academic Search

This paper proposed a new soft switching interleave boost converter with high voltage gain. In this converter two switches operate under ZVS condition without adding any auxiliary ? ? + , - ,------???-----. , , -- -'--''-'-'-'--''-''------' -''-'-'- ? \\\\ ,- ,- ------ ... ... ,\\\\ ? \\\\

Majid Delshad; Ehsan Shahri

2011-01-01

116

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

Microsoft Academic Search

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

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

1989-01-01

117

High gain ytterbium doped Ge pedestal large pitch fiber  

NASA Astrophysics Data System (ADS)

Large mode area rod-type fibers have enabled amplification of ultra-short pulses to mJ pulse energy and MW peak powers. For very large mode field areas, fibers have to be designed as rigid rods with typical fiber lengths of around 1 m for efficient operation. A shorter fiber length can be desirable to reduce the packaging size of commercial systems and to decrease the impact of parasitic nonlinear effects for peakpower scaling. The fiber design presented here is based on a modified large-pitch fiber with an effectively higher ytterbium concentration in the fiber core. To achieve index matching the cladding index needs to be changed. In this contribution we propose to co-dope the passive host material with germanium to match both indices and to obtain a higher Yb-concentration within the active core. Compared to standard LPF, where the core index is reduced by co-doping the core with Flourine, the ytterbium doping concentration of this novel germanium-pedestal LPF is doubled. A detailed numerical and experimental investigation shows that with short fiber lengths <40cm is feasible to achieve output powers beyond 100W with 10W seed. Significantly higher gains, of nearly 30 dB, can be achieved for fiber lengths in the order of 60cm. A similar gain can be expected in a conventional LPF with 1.20 m length. In conclusion, we demonstrate a fiber design for significantly enhanced energy storage per fiber length and improved pump absorption. This concept will notably reduce the footprint of ultra-short fiber laser systems.

Gaida, Christian; Stutzki, Fabian; Jansen, Florian; Otto, Hans-Jürgen; Eidam, Tino; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

2014-03-01

118

Mechanisms underlying obesity resistance associated with high spontaneous physical activity.  

PubMed

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 (OXRs) 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 the generation of SPA. To test this, SPA response was determined in lean and obese rats with cannulae targeted toward the rostral lateral hypothalamus (rLH) or SN. Sleep/wake states were also measured in rats with rLH cannula and electroencephalogram/electromyogram radiotelemetry transmitters. SPA in lean rats was more sensitive to antagonism of the 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 obesity-resistant 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 the mediation of SPA and running wheel activity. PMID:24161277

Teske, J A; Billington, C J; Kotz, C M

2014-01-01

119

Output feedback control using high-gain observers in the presence of measurement noise  

Microsoft Academic Search

Output feedback control using high-gain observers in the presence of measurement noise is considered for a class of nonlinear systems. We show that the closed-loop system with high-gain observer converges to a closed-loop system with ideal differentiation as the gain of the observer is increased. This ideal differentiation system is developed to reference the convergence properties. Analytical and simulation results

Jeffrey H. Ahrens; Hassan K. Khalil

2004-01-01

120

Photon detection with high gain avalanche photodiode arrays  

SciTech Connect

The detection of light emitted in fast scintillating fibers and Cerenkov radiators used for fiber calorimetry and tracking applications in high energy colliders, requires fast detector arrays with high sensitivity to short wavelength photons. Photomultiplier tubes, the traditional imaging detectors for short wavelength optical radiation, have limited spatial resolution and require expensive anti-magnetic shielding. The authors report on short wavelength sensitivity improvement and detection efficiency performance for a novel p-n junction planar structure silicon avalanche photodiode (APD) array, operated in Geiger mode. The APD array provides a high sensitivity detector for applications requiring the detection of light spatial distributions with single photon sensitivity.

Vasile, S.; Gothoskar, P.; Farrell, R. [Radiation Monitoring Devices, Inc., Watertown, MA (United States)] [Radiation Monitoring Devices, Inc., Watertown, MA (United States); Sdrulla, D. [Advanced Power Technology, Bend, OR (United States)] [Advanced Power Technology, Bend, OR (United States)

1998-06-01

121

Broadband High Gain Small Array Antenna for High Altitude Platforms Applications  

Microsoft Academic Search

This paper presents a novel design of a high gain multilayer strip-slot-foam-inverted patch (SSFIP) antenna working at 30 GHz. The antenna is designed to provide a special radiation pattern, which contributes to the reduction of grating lobes when used as element of array. Sub-arrays of 4 and 16 elements were simulated using a commercial EM simulator. Radiation pattern of 64

Qin Xu; John R. Farserotu; Jean-François Zürcher; Anja Skrivervik

2007-01-01

122

Gaining confidence in high-throughput protein interaction networks  

Microsoft Academic Search

Although genome-scale technologies have benefited from statistical measures of data quality, extracting biologically relevant pathways from high-throughput proteomics data remains a challenge. Here we develop a quantitative method for evaluating proteomics data. We present a logistic regression approach that uses statistical and topological descriptors to predict the biological relevance of protein-protein interactions obtained from high-throughput screens for yeast. Other sources

Amitabha Chaudhuri; Jonathan M Rothberg; John Chant; Joel S Bader

2003-01-01

123

A high-swing 2-V CMOS operational amplifier with replica-amp gain enhancement  

Microsoft Academic Search

A general gain-enhancement technique for operational amplifiers using a replica amplifier is described. Unlike conventional techniques such as cascoding, which increases the gain by increasing the output resistance, the replica-amp technique increase the gain by matching the main and the replica amps. Among the advantages of the replica-amp technique are low supply, high swing, and effectiveness with resistive loads. This

P. C. Yu; Hae-Seung Lee

1993-01-01

124

High gain avalanche photodiode arrays for DIRC applications  

SciTech Connect

The detection of light emitted in Cherenkov radiators requires fast detector arrays with high sensitivity to short wavelength photons. Photomultiplier tubes, the traditional imaging detectors for short wavelength optical radiation, have limited spatial resolution and require expensive anti-magnetic shielding. The authors report on the performance of a new, Geiger mode operated, silicon micro-avalanche photodiode ({micro}APD) array, designed for Cherenkov light imaging applications. They address issues of optical interfacing, speed, and pulse spectra achievable with these {micro}APDs. The new {micro}APD array provides a high sensitivity detector for applications requiring two dimensional light mapping with single photon sensitivity. These features make it a promising candidate for the detection of Cherenko light in modern high energy physics experiments.

Vasile, S.; Shera, S.; Shamo, D.; Squillante, M.R. [Radiation Monitoring Devices, Inc., Watertown, MA (United States)] [Radiation Monitoring Devices, Inc., Watertown, MA (United States); Wilson, R.J. [Colorado State Univ., Fort Collins, CO (United States)] [Colorado State Univ., Fort Collins, CO (United States)

1999-08-01

125

High Gain Observer for Structured Multi-Output Nonlinear Systems  

Microsoft Academic Search

In this note, we present two system structures that characterize classes of multi-input multi-output uniformly observable systems. The first structure is decomposable into a linear and a nonlinear part while the second takes a more general form. It is shown that the second system structure, being more general, contains several system structures that are available in the literature. Two high

Hassan Hammouri; Guy Bornard; Krishna Busawon

2010-01-01

126

New high-gain detectors for active imaging  

NASA Astrophysics Data System (ADS)

New applications require high sensitivity infrared (IR) sensors in order to detect very low incident fluxes. Laser gated imaging has, in particular, additional specific needs. IR sensors for this type of application are synchronized with eye-safe lasers, and have to detect a weak signal backscattered from the target on the order of 10 photons per pulse. They also have to be able to operate with a very short integration time, typically one hundred nanoseconds, to gate the backscattered signal around the target. In partnership with Sofradir, CEA/LETI (France) has developed high quality HgCdTe avalanche photodiodes satisfying these requirements. In parallel, specific studies have been carried out at the Read-Out Circuit level to develop optimized architectures. Thanks to these advances, a new Integrated Dewar Detector Cooler Assembly has been developed. This new product is the first step in a road-map to address low flux infrared sensors in the next few years.

Pistone, Frederic; Tribolet, P.; Lefoul, X.; Zecri, M.; Courtas, S.; Jenouvrier, P.; Rothman, Johan

2009-05-01

127

Energy gain of highly charged ions in front of LiF.  

National Technical Information Service (NTIS)

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 charg...

L. Haegg C. O. Reinhold J. Burgdoerfer

1996-01-01

128

High-Gain Observer-Based Estimation of Parameter Variations With Delay Alignment  

Microsoft Academic Search

This technical note analyzes the estimation delay in a high gain observer, where the state estimates may lag behind the actual states due to the observer's non-zero phase response. The technical note proves that, for a slowly time-varying system subject to bounded noises, the estimation delay depends on the observer gain, but is independent of the variations of system parameters.

Xuewu Dai; Zhiwei Gao; Timofei Breikin; Hong Wang

2012-01-01

129

Error bounds in differentiation of noisy signals by high-gain observers  

Microsoft Academic Search

The error in estimating the derivative(s) of a noisy signal by using a high-gain observer is studied and quantified. The error is bounded in terms of the infinity norms of the noise and a derivative of the signal. The error bound is independent of the frequency or derivatives of the noise. Guidelines are presented for the observer gain design when

Luma K. Vasiljevic; Hassan K. Khalil

2008-01-01

130

Nonlinear stabilizing control law, with a dynamical high gain observer: application to mechanical process  

Microsoft Academic Search

The authors consider mechanical systems for which a stabilizing control law from the minimization of a Lyapunov function has to be constructed. A stabilizing control law for an overhead crane is proposed. In particular, a high-gain observer is used to estimate the momentum of the mechanical process. Its gain is adaptive and depends on the estimation error

T. Chorot; J. De Leon Morales

1991-01-01

131

High-gain-observer tracking performance in the presence of measurement noise  

Microsoft Academic Search

High-gain observers are commonly utilized to estimate the states used in constructing the output feedback control, when such states are derivatives of the output. In the presence of measurement noise, the estimation error can be noticeably compromised if the observer gain is chosen too large. However, the effect of measurement noise on the tracking error is less significant. This phenomenon

Alexis A. Ball; Hassan K. Khalil

2009-01-01

132

Output feedback sampled-data control of nonlinear systems using high-gain observers  

Microsoft Academic Search

This paper studies sampled-data control of nonlinear systems using high-gain observers. The observer is designed in continuous time, then discretized using three different discretization methods. Closed-loop analysis shows that the sampled data controller recovers the performance of the continuous time controller as the sampling frequency and the observer gain become sufficiently large

Ahmed M. Dabroom; Hassan K. Khalil

2000-01-01

133

Differentiation with High-Gain Observers the Presence of Measurement Noise  

Microsoft Academic Search

The error in estimating the derivative(s) of a noisy signal by using a high-gain observer is studied and quantified. The error is bounded in terms of the infinity norms of the noise and a derivative of the signal. The error bound is independent of the frequency or derivatives of the noise. Guidelines are presented for the observer gain design when

Luma K. Vasiljevic; Hassan K. Khalil

2006-01-01

134

Robust output feedback control of robot manipulators using high-gain observer  

Microsoft Academic Search

In this paper, we design a robust output feedback controller for trajectory control of n-link robot manipulators with bounded parametric uncertainties. The state feedback controller with integral control improves tracking error due to limit of the robust feedback gains and use of continuous control input for chattering rejection. High-gain observer is used to estimate joint velocities. We show that the

E. S. Shin; K. W. Lee

1999-01-01

135

Discrete fuzzy high gain observer for a class of nonlinear systems  

Microsoft Academic Search

In order to improve the robustness of the discrete high gain observer with respect to noise measurements and enhance the convergence dynamics, we propose, in this paper, a fuzzy supervision for the observation of a class of nonlinear systems. Actually, a suitable tuning of the observer’s gain is made by a fuzzy supervisor. Simulation results are given in order to

M. Oueder; M. Mihoub; R. Ben Abdennour; M. Farza

2011-01-01

136

Estimation delay compensation in high-gain observer-based parameter identification  

Microsoft Academic Search

In this paper, the properties of the disturbance estimation in a high gain observer are analyzed, and a time delay calculation method is proposed to improve the performance of parameter identification. This paper shows that the estimation delay depends on the observer gain, but has nothing to do with the parameter variation. Then, a novel algorithm is proposed to calculate

Xuewu Dai; Zhiwei Gao; Tim Breikin; Hong Wang

2009-01-01

137

A novel high-gain wideband patch antenna fed by twin-L-probe  

Microsoft Academic Search

A novel high-gain, wideband central-shorted oblong patch antenna fed by twin-L-probe is presented in this paper. The proposed antenna is studied both numerically and experimentally. It is shown that the antenna has a wide operational bandwidth of over 40% (S11<;-10 dB) and maximum gain up to 11.5 dBi.

Liang Zhu; Yong Cheng; Bin Yu; Di Wu; K. Seo

2010-01-01

138

High-Gain UHF Backfire Antenna for Communications, Telemetry, and Radio Astronomy.  

National Technical Information Service (NTIS)

The backfire antenna described combines the structural advantages of a single endfire with the high gain of a reflector antenna. With its principal application in the gain range between 15 and 30 dB where ordinary endfire antennas become impractically lon...

H. W. Ehrenspeck

1967-01-01

139

Short-Backfire Antenna as an Element for High-Gain Arrays.  

National Technical Information Service (NTIS)

The short backfire (SBF) antenna consisting of a large reflector illuminated by a dipole feed and smaller disk reflector produces a gain of 15 dB above isotropic. As an array element it has been effciently adapted for various configurations of high-gain a...

H. W. Ehrenspeck J. A. Strom

1971-01-01

140

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

Microsoft Academic Search

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

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

1984-01-01

141

Lateral npn bipolar transistor for high current gain applications at reduced temperatures  

Microsoft Academic Search

The possibility of operating a high-current-gain lateral bipolar junction transistor (BJT), derived from a CMOS structure by jointing the gate and the substrate to form the base of the BJT, at very low temperature is described. This transistor does not suffer any current gain degradation at 77 K due to heavy doping effects. The structure can also be used in

J. C. S. Woo; S. Wong; S. Verdonckt-Vanderbroek; P. Ko; K. Terrill; P. K. Vasudev

1989-01-01

142

Ceramic windows and gain media for high-energy lasers  

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

143

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

PubMed

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

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

2003-10-20

144

Design, development and testing of the x-ray timing explorer High Gain Antenna System  

NASA Technical Reports Server (NTRS)

The High Gain Antenna System (HGAS), consisting of two High Gain Antenna Deployment Systems (HGADS) and two Antenna Pointing Systems (APS), is used to position two High Gain Antennas (HGA) on the X-Ray Timing Explorer (XTE). A similar APS will be used on the upcoming Tropical Rainfall Measuring Mission (TRMM). Both XTE and TRMM are NASA in-house satellites. The salient features of the system include the two-axis gimbal and control electronics of the APS and the spring deployment and latch/release mechanisms of the HGADS. This paper describes some of the challenges faced in the design and testing of this system and their resolutions.

Lecha, Javier; Woods, Claudia; Phan, Minh

1995-01-01

145

Tomographic Imaging and Three-Dimensional Reconstruction Based on a High-Gain Optical Parametric Amplifier  

NASA Astrophysics Data System (ADS)

Tomographic imaging and three-dimensional reconstruction based on a high-gain picosecond optical parametric amplifier (OPA) is demonstrated. More than 40 dB intensity amplification of the image is achieved from the high-gain OPA. The images of various longitudinal positions of the target are extracted by the gated nature of the OPA, then a three-dimensional (3-D) surface topography of the target is reconstructed. The gated and high-gain property of the OPA allows tomographic optical imaging together with 3-D profile reconstruction of the target in turbid media.

Yang, Jing; Du, Shi-Feng; Zhang, Jing-Yuan; Cao, Dong; Cui, Da-Fu; Peng, Qin-Jun; Xu, Zu-Yan

2012-05-01

146

Angular spectrum characters of high gain non-critical phase match optical parametric oscillators  

NASA Astrophysics Data System (ADS)

The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time. The experimental results of the KTiOAsO4 and the KTiOPO4 crystals are discussed in detail. At the high energy single resonant condition, low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles. This method can also be used for other high gain non-walk-off phase match optical parametric processes.

Liu, Jian-Hui; Liu, Qiang; Gong, Ma-Li

2011-05-01

147

Nanogate- a nanosecond gated image intensifier with high gain and high resolution  

SciTech Connect

The investigation of luminous phenomena with two-dimensional resolution in space and resolution in time requires electro-optical devices which can be gated for very short time intervals. Image intensifiers are presently mainly used for this purpose. They are available either as image intensifiers with microchannel plates or as image intensifier diodes. Due to secondary electron multiplication, microchannel plate intensifiers have high gain; if image intensifier diodes are used, up to three diodes must be cascaded to attain a comparably high gain. This paper presents an image intensifier cascade consisting of three image intensifier diodes which are coupled by fiber optics. The first image intensifier is used as an electro-optical high-speed shutter. Since the entire supply voltage of 9 KeV has to be pulsed, a diode with an electrode spacing of only 1.5 mm is used; the gain for this voltage is about 50. The two cascaded image intensifiers have an electrode spacing of 2.5 mm and a supply voltage of 15 KeV each and are used for the light amplification of the output of the first intensifier. This amplification is about 3,500. The third intensifier has a quartz glass input window which provides useful sensitivity in a spectral range of about 180 to 900 nm. A transistorized high voltage pulse generator, developed according to the Marx cascade and coupled to the intensifier, is described. The advantages and disadvantages of such a cascade compared to a microchannel plate intensifier are discussed.

Pfeiffer, W.; Wittmar, D.

1984-02-01

148

Procedures and Use of Time in Reading Classes in High-Gain and Low-Gain Elementary Schools in Chicago.  

ERIC Educational Resources Information Center

A study of 39 elementary schools in Chicago was conducted to compare two sets of schools, those whose students made above average yearly gains in reading comprehension and those whose students' reading gains were below average. These schools were compared on the proportion of time spent on task, on what the teacher and pupils did during reading…

Fredrick, Wayne; And Others

149

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

PubMed

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

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

2013-09-22

150

Analysis and Synthesis of High Gain and Variable Structure Feedback Systems.  

National Technical Information Service (NTIS)

This study deals with the analysis and synthesis of two classes of multivariable feedback systems, high gain feedback systems and variable structure systems (VSS), subject to parameter variations and disturbances. First is examined the insensitivity prope...

K. K. D. Young

1977-01-01

151

High-gain observer design with sampled measurements: application to inverted pendulum  

Microsoft Academic Search

New results on high-gain observer design for sampled-data systems are presented for a large class of nonlinear uniformly observable systems. It is shown that by using an appropriate Lyapunov function, it is possible to design a continuous high-gain observer coupled with a large class of output predictors. An explicit bound on the maximum allowable sampling interval guaranteeing stability of the

Ph. Dorléans; J.-F. Massieu; T. Ahmed-Ali

2011-01-01

152

Separation results for the stabilization of nonlinear systems using different high-gain observer designs  

Microsoft Academic Search

High-gain observers have been used in the design of output feedback controllers due to their ability to robustly estimate the unmeasured states while asymptotically attenuating disturbances. The available techniques for the design of high-gain observers can be classified into three groups: pole-placement algorithms, Riccati equation-based algorithms, and Lyapunov equation-based algorithms. In [1], we presented separation results for globally bounded stabilizing

A. N. Atassi; H. K. Khalil

2000-01-01

153

Adaptive nonlinear output feedback tracking with a reduced order high-gain observer  

Microsoft Academic Search

Concerns output-feedback adaptive controllers for nonlinear systems which require observers with the high gain. This may pose a problem if the measured output is corrupted by noise. In order to reduce the effect of noise a new class of adaptive controllers is proposed which uses a reduced order high-gain observer to estimate only the first r, (r

Mrdjan Jankovic

1994-01-01

154

Adaptive nonlinear output feedback tracking with a partial high-gain observer and backstepping  

Microsoft Academic Search

An adaptive output feedback controller for nonlinear systems with nonlinearities depending on the first r (1⩽r⩽n) derivatives of the output is proposed. The derivatives are estimated with a partial state high-gain observer, and the remaining states are handled using a backstepping method. Compared with methods based on full state high-gain observer, this approach improves robustness with respect to measurement noise

Mrdjan Jankovic

1997-01-01

155

Full-order high-gain observers for minimum phase nonlinear systems  

Microsoft Academic Search

This paper studies the design of a full-order, high-gain observer for a class of minimum-phase nonlinear systems. The dynamic state feedback design is modified to include the observer for the internal dynamics. It is shown that the performance of such a dynamic partial-state feedback control can be recovered by the output feedback control using a sufficiently fast high-gain observer, in

Attaullah Y. Memon; Hassan K. Khalil

2009-01-01

156

High-gain observer for a class of time-delay nonlinear systems  

Microsoft Academic Search

This article proposes a high-gain observer design for a class of nonlinear systems with multiple known time-varying delays intervening in the states and the inputs. In the free delay case, the class of systems under consideration coincides with a canonical form characterising a class of multi-output nonlinear systems, which are observable for any input. The underlying high-gain design has been

M. Farza; A. Sboui; E. Cherrier; M. MSaad

2010-01-01

157

Design, testing and modeling of a high-gain magnetic flux-compression generator  

Microsoft Academic Search

Using a simultaneously initiated cylindrical explosive, a coaxial magnetic flux-compression generator (FCG) was designed to test high-current-gain limitations. A coaxial design with a lossless gain of approx.100:1 was chosen for its efficiency, relative simplicity, and calculability. Theoretical design included modeling as well as 1-D and 2-D hydrodynamic and MHD calculations. A 69.3-cm cylinder of PBX-9501 high explosive, 20.3 cm in

M. G. Sheppard; B. L. Freeman; R. L. Bowers; J. H. Brownell; C. M. Fowler; J. N. Fritz; A. E. Greene; S. P. Marsh; T. A. Oliphant; D. L. Tubbs

1986-01-01

158

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

Microsoft Academic Search

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

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

159

Brightness and coherence of radiation from undulators and high-gain free electron lasers  

SciTech Connect

The purpose of this paper is to review the radiation characteristics of undulators and high-gain free electron lasers (FELs). The topics covered are: a phase-space method in wave optics and synchrotron radiation, coherence from the phase-space point of view, discussions of undulator performances in next-generation synchrotron radiation facility and the characteristics of the high-gain FELs and their performances. (LSP)

Kim, Kwang-Je

1987-03-01

160

Gain-transparent SOA-switch for high-bitrate OTDM add\\/drop multiplexing  

Microsoft Academic Search

We report on an all-optical interferometric optical time-division multiplexing switch that exhibits high linearity, high-switching contrast, low noise, wide bandwidth, and low crosstalk. The key element of the gain-transparent switch is a semiconductor optical amplifier (SOA), which is transparent for the data signal. However, the injection of optical control pulses in the gain wavelength region of the SOA leads to

S. Diez; R. Ludwig; H. G. Weber

1999-01-01

161

Active Flutter Suppression of a High-Aspect-Ratio Aeroelastic Using Gain Scheduling  

NASA Astrophysics Data System (ADS)

This paper presents a control design of gain scheduling controllers for active flutter suppression (AFS) in which the closed loop system is stabilized in the operating region specified in advance. The AFS system of a high-aspect-ratio wing is represented by a linearly interpolated polytopic model whose varying parameter is the dynamic pressure. The gain scheduling controller in this paper consists of a regulator and a full-order observer which are scheduled by the varying parameter. Linear matrix inequalities for designing the gains of the regulator and the observer are separately derived in the frame of the H2 optimization. The control performance and the characteristics of the designed gain scheduling controllers are evaluated in comparison with fixed H2 controllers which are designed with the same design parameters. As the result, the gain scheduling controllers may be inferior to the fixed controller at local regions, but are superior to the fixed controllers for the entire operating region.

Fujimori, Atsushi; Miura, Kyohei; Matsushita, Akira

162

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

NASA Astrophysics Data System (ADS)

The polarized optical gain characteristics of highly stacked InAs/GaAs quantum dots (QDs) with a thin spacer layer fabricated on an n+-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.

Kita, Takashi; Suwa, Masaya; Kaizu, Toshiyuki; Harada, Yukihiro

2014-06-01

163

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

SciTech Connect

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.

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

164

Design of a Novel High-Gain Dual-Band Antenna for WLAN Applications  

Microsoft Academic Search

A novel high-gain, dual-band antenna covering IEEE 802.11a\\/b\\/g bands is presented in this letter for wireless local area network (WLAN) applications. The antenna is composed of a fork-like monopole, a rectangular ring, and a miniaturized rectangular patch. The backside radiation of the antenna is effectively reflected back by a rectangular metal, so maximum gain with the values of 6.2 and

Xiaoxiang He; Sheng Hong; Huagang Xiong; Qishan Zhang; Emmanouil Manos M. Tentzeris

2009-01-01

165

Generation of ultra-short pulses from high-gain narrow-linewidth lasers  

Microsoft Academic Search

Modified type mode-locking with many passive-mode excitation has been proposed to generate ultra-short light pulses from high-gain narrow-linewidth lasers, The mode-locking with single-active-mode (MLSAM) which is the useful and practical case of the modified type mode-locking has been analyzed taking into account the effect of large locking signal and the variation of the saturated gain along the light path. An

T. Kobayashi; S. Konishi; T. Sueta

1975-01-01

166

Peaking free variable structure control of uncertain linear systems based on a high-gain observer  

Microsoft Academic Search

An output-feedback model-reference variable structure controller based on a high-gain observer (HGO) is proposed and analyzed. For single-input–single-output (SISO) linear plants with relative degree greater than one, the control law is generated using the HGO signals only to drive the sign function of the variable structure control component while the sign function gain, also called modulation, as well as the

José Paulo Vilela Soares Da Cunha; Ramon R. Costa; Fernando C. Lizarralde; Liu Hsu

2009-01-01

167

Output feedback sampled-data control of nonlinear systems using high-gain observers  

Microsoft Academic Search

This paper studies sampled-data control of nonlinear systems using high-gain observers. The observer is designed in continuous time, then discretized using three different discretization methods. Closed-loop analysis shows that the sampled-data controller recovers the performance of the continuous time controller as the sampling frequency and observer gain become sufficiently large. The theory is illustrated by experimental results

Ahmed Mohammed Dabroom; Hassan K. Khalil

2001-01-01

168

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

Microsoft Academic Search

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

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

2008-01-01

169

High-gain active composite right\\/left-handed leaky-wave antenna  

Microsoft Academic Search

A novel high-gain active composite right\\/left-handed (CRLH) metamaterial leaky-wave antenna (LWA) is presented. This antenna, which is designed to operate at broadside, is constituted by passive CRLH leaky-wave sections interconnected by amplifiers, which regenerate the power progressively leaked out of the structure in the radiation process in order to increase the effective aperture of the antenna and thereby its gain.

Francisco P. Casares-Miranda; Carlos Camacho-Peñalosa; Christophe Caloz

2006-01-01

170

Gain and efficiency studies of a high power travelling wave tube amplifier  

Microsoft Academic Search

The results of measurements on the gain and efficiency of a high power travelling wave tube amplifier powered by a 850 keV, 0.8-1.6 kA, 100 nsec pencil electron beam are reported. The amplifier operates in the TM01 mode and is driven by a 250 kW magnetron. Gains of up to 35 dB and efficiencies of 11 percent have been achieved

D. Shiffler; John A. Nation; J. D. Ivers; G. Kerslick

1990-01-01

171

Low power high bandwidth amplifier with RC Miller and gain enhanced feedforward compensation  

Microsoft Academic Search

An improved frequency compensation technique is presented for low-power low-voltage three-stage operational amplifiers with high capacitive loads. The technique uses single RC Miller compensation and a direct gain enhanced feedforward path from the input to the output. With a load capacitance of 300 pF, the amplifier nominally achieves a dc gain of 74 dB, a 3-dB bandwidth of 2.9 kHz,

Shagun Bajoria; Vineet Kumar Singh; Raju Kunde; Chetan D. Parikh

2008-01-01

172

Nonrestoration of spontaneously broken P, CP and PQ at high temperature.  

National Technical Information Service (NTIS)

The possibility of P and CP violation at high temperature in models where these symmetries are spontaneously broken is investigated. It is found that in minimal models that include singlet fields, high T nonrestoration is possible for a wide range of para...

G. Dvali A. Melfo G. Senjanovic

1996-01-01

173

High Gain Observer for backstepping control of a MRI-guided therapeutic microrobot in blood vessels  

Microsoft Academic Search

This paper reports precise modeling and controller\\/ observer design for a microsized polymer aggregate of magnetic particles inside an artery, using a Magnetic Resonance Imaging (MRI) device for supplying propulsion in order to achieve targeted chemotherapy. Non-Newtonian behaviour of blood is taken into account, as well as wall effects and interactions, resulting in a highly nonlinear model. A High Gain

Laurent Arcese; Ali Cherry; Matthieu Fruchard; Antoine Ferreira

2010-01-01

174

Use of optically triggered, high gain GaAs switches for UWB pulse generation.  

National Technical Information Service (NTIS)

A high peak power impulse pulser that is controlled with high gain, optically triggered GaAs Photoconductive Semiconductor Switches (PCSS) has been constructed and tested. The system has a short 50 (Omega) line that is charged to 100 kV and discharged thr...

G. M. Loubriel F. J. Zutavern M. W. O'Malley R. R. Gallegos W. D. Helgeson

1994-01-01

175

Development and Testing of a High-Gain Magnetic Flux Compression Generator  

Microsoft Academic Search

The performance of a high-gain FCG is often limited by internal electrical breakdown caused by the high voltage generated during operation. Modern diagnostic techniques provide the opportunity to diagnose internal breakdowns so that generator designs can be improved. This paper describes the internal breakdowns observed in the JAKE FCG developed at the AFRL during the late 1990's. A revision to

J. V. Parker; T. C. Cavazos; C. E. Roth; J. H. Degnan; G. F. Kiuttu; F. M. Lehr

2006-01-01

176

High gain parametric processes in quasi-phase-matching proton-exchange lithium niobate waveguides  

Microsoft Academic Search

Developments in nonlinear optical materials and solid-state lasers led to rapid progress in nonlinear optics in recent years. Among the many fields of nonlinear optics, chi(2) parametric processes are among the major tools for generating coherent radiation indispensable in optical communication, spectroscopy and medical applications. Involving short pulses with high peak power, high gain parametric processes, including optical parametric amplification

Xiuping Xie

2006-01-01

177

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

NASA Astrophysics Data System (ADS)

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.

Chang, Chao; Hei, DongWei; Pellegrin, Claudio; Tantawi, Sami

2013-12-01

178

The 2.45 GHz 36 W CW Si recessed gate type SIT with high gain and high voltage operation  

Microsoft Academic Search

The Si microwave recess gate type SIT (Static Induction Transistor) has been fabricated and the high drain blocking voltage up to 140 V with high gain was obtained. The power gain of 13.7 dB up to 1.7 GHz, 10 dB at 2 GHz, 6 dB at 3 GHz, and the maximum frequency of oscillation of 4 GHz in common gate

Jun-ichi Nishizawa; Kaoru Motoya; Akira Itoh

2000-01-01

179

High responsivity and internal gain mechanisms in Au-ZnMgO Schottky photodiodes  

NASA Astrophysics Data System (ADS)

Schottky photodiodes based on Au-ZnMgO/sapphire are demonstrated covering the spectral region from 3.35 to 3.48 eV, with UV/VIS rejection ratios up to ~105 and responsivities as high as 185 A/W. Both the rejection ratio and the responsivity are shown to be largely enhanced by the presence of an internal gain mechanism, by which the compensated films become highly conductive as a result of illumination. This causes a large increase in the tunnel current through the Schottky barrier, yielding internal gains that are a function of the incident photon flux.

Tabares, G.; Hierro, A.; Ulloa, J. M.; Guzman, A.; Muñoz, E.; Nakamura, A.; Hayashi, T.; Temmyo, J.

2010-03-01

180

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

NASA Astrophysics Data System (ADS)

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 73% (VSWR<2), so the antenna can cover the K/Ka band. Because of the merits of the high gain and wide band, this antenna is not just used in the satellite communication, but also in the other domain such as the mobile communication.

Wang, Yonggen

2009-12-01

181

Soft-switching interleaved boost converter with high voltage gain applied to a photovoltaic system  

Microsoft Academic Search

This paper presents a soft-switching interleaved boost converter with high voltage gain connected to photovoltaic panels. This converter is far suitable for this application, as it presents a high step-up voltage and high efficiency, due to the non-dissipative soft-switching cell adapted to the converter. In order to verify its effectiveness, experimental results from this converter operating with hard-switching and soft-switching

R. N. A. L. Silva; G. A. L. Henn; P. P. Praça; R. A. da Ca?mara; L. H. S. C. Barreto; D. S. Oliveira Jr

2010-01-01

182

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

SciTech Connect

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.

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

183

A variable structure model reference robust control without a prior knowledge of high frequency gain sign  

Microsoft Academic Search

The design of a variable structure model reference robust control without a prior knowledge of high frequency gain sign is presented. Based on an appropriate monitoring function, a switching scheme for some control signals is proposed. It is shown that after a finite number of switching, the tracking error converges to zero at least exponentially for plants with relative degree

Lin Yan; Liu Hsu; Ramon R. Costa; Fernando C. Lizarralde

2008-01-01

184

Sliding mode high-gain observers for a class of uncertain nonlinear systems  

Microsoft Academic Search

A robust high-gain observer for state and unknown input estimations for a special class of single-output nonlinear systems is developed in this article. Ensuring the observability of the unknown input with respect to the output, the disturbance can be estimated from the sliding surface. In the sliding mode, the convergence of the estimation error dynamics is proven similar to the

Kalyana C. Veluvolu; Dongik Lee

2011-01-01

185

RECONSTRUCTING AND IDENTIFYING THE ROSSLER'S SYSTEM BY USING A HIGH GAIN OBSERVER  

Microsoft Academic Search

A simple way to determine the parameters of Rössler's system based on a suitable output is presented in this paper. The fact that the nonlinear system is observable and algebraically identifiable with re- spect to the selected output, allows us to propose, in a first stage, a high-gain observer to estimate the output time derivatives. And then, based on these

Carlos Aguilar Ibáñez; R. Martínez; R. Garrido

2006-01-01

186

High gain observer for a class of non-triangular systems  

Microsoft Academic Search

This paper presents a high gain observer for a class of MIMO nonlinear systems involving some uncertainties. The latter is particularly composed of cascade subsystems where each subsystem is associated with a subset of the output variables, and assumes a triangular dependence on its own state variables and may depend on the state variables of all other subsystems. The main

Mondher Farza; Mohammed M'Saad; M. Triki; Tarak Maatoug

2011-01-01

187

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

Microsoft Academic Search

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

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

2003-01-01

188

High-gain observer approach to disturbance attenuation using measurement feedback  

Microsoft Academic Search

A procedure is developed for disturbance attenuation in a linear system via the use of measurement feedback. A high-gain observer is used to recover the disturbance attenuation properties asymptotically, which can be achieved using full state feedback. It is thus shown that the problem of disturbance attenuation via measurement feedback can be decomposed into two problems of disturbance attenuation via

IAN R. PETERSEN; CHRISTOPHER V. HOLLOT

1988-01-01

189

Nonlinear output feedback control design of a hypersonic vehicle via high gain observers  

Microsoft Academic Search

In this paper, the output feedback control problem for a genetic hypersonic vehicle is considered under the restriction that only the vehicle's velocity and altitude are measurable. High gain observers (HGO) are utilized to provide estimation signals for unmeasurable derivatives of the vehicle's velocity and altitude. A comprehensive stability analysis of the closed loop system under the output feedback control

Xindong Li; Bin Xian; Chen Diao; Yanping Yu; Kaiyan Yang; Yu Feng

2010-01-01

190

Decentralized Adaptive Control of Interconnected Non-Linear Systems Using High Gain Observer  

Microsoft Academic Search

This paper investigates a decentralized adaptive control strategy for a class of interconnected unknown non-linear systems. The idea of the strategy is based on the feedback linearizing control and perturbation estimation. A high gain observer is designed in association with each sub-system to estimate the states and a fictitious state which is defined to represent the system perturbation including the

Q. H. Wu; L. Jiang; J. Y. Wen

2004-01-01

191

Nonlinear restoring force estimation in civil structures using a high gain observer  

Microsoft Academic Search

Strong ground motions may cause damage to structural elements by cracking or yielding. Hysteresis cycles are a measure of this damage. The present paper uses a class of integral high gain observers to estimate the unknown nonlinear restoring force of a single-degree-of-freedom structure. Simulations are carried out using the Mexico City at SCT (1985) and the El Centro (1940) time

R. Garrido; F. J. Rivero-Angeles; R. Martinez-Guerra; B. Gomez-Gonzalez; J. C. Martinez-Garcia

2004-01-01

192

A high-gain observer-based PD control for robot manipulator  

Microsoft Academic Search

In this paper, the popular PD control of robot manipulator is modified. A high-gain observer is proposed for the estimation of the velocity. The main contributions of this paper are: (1) By means of singular perturbation analysis, we prove that the closed-loop system is asymptotic stable; (2) We solve the problem of how much faster the observer should be than

Josk Antonio Heredia; Wen Yu

2000-01-01

193

High-Gain Observers With Sliding Mode for State and Unknown Input Estimations  

Microsoft Academic Search

To handle the state estimation of a nonlinear system perturbed by a scalar disturbance distributed by a known nonlinear vector, a sliding-mode term is incorporated into the nonlinear high-gain observer (HGO) to realize a robust HGO. By imposing a structural assumption on the unknown input distribution vector, the observability of the disturbance with respect to the output is safeguarded, and

Kalyana C. Veluvolu; Yeng Chai Soh

2009-01-01

194

Robust output feedback control of a magnetic levitation system via high-gain observer  

Microsoft Academic Search

This paper proposes a novel robust output feedback controller for an electromechanical system in the presence of external disturbance and uncertainties of physical parameters. By exploiting the cascade features of backstepping design, a simple disturbance observer is proposed to suppress the effects of the uncertainties, and a high-gain observer is applied to estimate the unmeasureable states of the system. Strict

Zi-Jiang Yang; Seiichiro Hara; Shunshoku Kanae; Kiyoshi Wada

2009-01-01

195

Original benchmark for sensorless induction motor drives at low frequencies and validation of high gain observer  

Microsoft Academic Search

An original benchmark for the validation of sensorless induction motor observers is proposed to evaluate them particularly in the well-known case where the motor state could be unobservable. Due to the complexity of observation at low frequencies (specifically on our benchmark) we present an improvement of a high gain observer which has been tested and validated on the reference trajectories

Malek Ghanes; Alexis Girin; Tarik Saheb

2004-01-01

196

Output regulation of non-minimum phase nonlinear systems using an extended high-gain observer  

Microsoft Academic Search

In this paper, we present an output feedback regulator for nonlinear systems that could potentially include unstable zero dynamics. The regulation scheme adopted herein incorporates continuously-implemented sliding mode control and an extended high gain observer to estimate the derivatives of the output and one of the unknown functions. The result is illustrated using a simulation.

Shahid Nazrulla; Hassan K. Khalil

2009-01-01

197

High gain observers with multiple sliding mode for state and unknown input estimations  

Microsoft Academic Search

High-gain observers with multiple sliding modes for simultaneous state and unknown input estimations of a class of MIMO nonlinear systems are systematically developed in this paper. The unknown inputs are assumed to be bounded and not necessarily Lipschitz, and do not require any matching condition. A new nonlinear transformation is proposed and the observer design and analysis are performed in

Kalyana C. Veluvolu; Soh Yeng Chai

2009-01-01

198

Parameter Identification for Electromechanical Servo Systems Using a High-gain Observer  

Microsoft Academic Search

In this paper, a High-gain Observer (HGO)-based identification technique is used to identify the parameters for electromechanical servo systems. The HGO is used for estimating the system states, disturbances due to uncertainty or parameter changing, and output noise. Then, a new model is presented using QR factorization. The estimated observer states show good agreement with the system actual states for

Usama Abou-Zayed; Zhiwei Gao; Xuewu Dai; Tim Breikin

199

STATE ESTIMATION IN FREE-RADICAL POLYMERIZATION REACTORS USING A NONLINEAR INTERCONNECTED HIGH GAIN OBSERVER  

Microsoft Academic Search

In this paper, a new robust nonlinear observer is proposed for the reconstruction of the whole process state variables in a simulated polymerization reactor. It presents an interconnected high gain observer to perform the estimation. This observer has robust performance in the presence of measurement noise and model uncertainty. The global stability of the observer is analytically treated using the

A. Mansouri; M. Bouhamida; M. Chenafa; E. N. S. T. Oran

200

A high-gain observer vs. algebraic derivative methods for track estimation  

Microsoft Academic Search

In this paper track estimation algorithms for a multiple articulated vehicle are examined to be used in advanced steering control systems. Therefore a high-gain observer based track estimator is designed for different sensor configurations. The results of an observability analysis are used for the observer design. The accuracy can be improved by the sensor fusion. Furthermore this approach utilizes the

R. Huber; S. Zipser; S. Wagner; K. Robenack

2012-01-01

201

Nonlinear high-gain observers with integral action: Application to bioreactors  

Microsoft Academic Search

This paper deals with the problem of estimating the states in nonlinear systems with parameters that are not precisely knwon through the implementation of proportional nonlinear high gain observers with additional integral action. It is known that non-linear observers (NL-P) show excellent results in the estimation of state variables but these depend heavily on precise knowledge of model parameters, this

A. Rodriguez-Mata; J. Torres-Munoz; A. R. Dominguez; D. Hernandez-Villagran; S. Celikovsky

2011-01-01

202

Design of two high gain, low profile helical antennas for operation at 918 MHz  

Microsoft Academic Search

Two helical antennas were designed, fabricated and tested to permit tanks or tracked vehicles to function with a high gain, low profile antenna field pattern for a telemetry system operating at 918 MHz. The electrical properties of the helical antennas were compared to the system's dipole antennas in an attempt to enhance the operating performance of the RMS\\/SCORE system. Field

J. F. Bouldry

1977-01-01

203

High gain linear polarization microstrip antenna with four element electromagnetically coupled patch  

Microsoft Academic Search

A high gain linear polarization antenna with four element electromagnetically coupled patch is presented in this paper. This antenna may be used to limited scan phased array. Two-layer patch is employed to broad impedance band and feeding network with exponential taper line transformer and coax to microstrip transition power divider is employed. Single element of electromagnetically coupled patch compared with

Cui WeiDong

2009-01-01

204

Research on high-gain and broad-band backfire antenna  

Microsoft Academic Search

In this paper, the experimental results of the backfire antenna with high gain and broad bandwidth are presented. The antenna\\u000a design is based on the theory of backfire antenna shown in Lin Changlu and the auther’s paper (1982), and what is presented\\u000a here may be considered as an experimental verification of it.

Song Ximing

1987-01-01

205

High-Gain, Long-Period Seismograph Station Installation Report, Eilat, Israel.  

National Technical Information Service (NTIS)

The report describes the installation of a high-gain, long-period seismograph system at Eilat, Israel. The station is located at 29.33 degrees North latitude, 34.57 degrees East longitude at an elevation of about 200 m above sea level in the same tunnel a...

T. L. Johnson

1971-01-01

206

Analytical treatment of the high-gain free electron laser equation  

Microsoft Academic Search

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

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

1996-01-01

207

Attainment of a high gain in a disk amplifying stage with neodymium phosphate glass elements  

SciTech Connect

An efficient reflecting coating made of a MIRO foil with an oxide layer is fabricated, which enhances the reflection of radiation of pump lamps in the head of a high-power neodymium laser and allows a gain g{sub 0}=5x10{sup -2} cm{sup -1} to be achieved. (lasers)

Voronich, Ivan N; Garanin, Sergey G; Zaretskii, Aleksei I; Ignat'ev, Ivan V; Kirillov, G A; Murugov, Vasilii M; Osin, Vladimir A; Sukharev, Stanislav A [Russian Federal Nuclear Center 'All-Russian Scientific Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod Region (Russian Federation); Charukhchev, Aleksandr V [Research Institute for Complex Testing of Optoelectronic Devices and Systems, Leningrad region (Russian Federation)

2004-06-30

208

A high power gain switched diode laser oscillator and amplifier for the CEBAF polarized electron injector  

SciTech Connect

The photocathode in the polarized electron source at Jefferson Lab is illuminated with pulsed laser light from a gain switched diode laser and diode optical amplifier. Laser pulse repetition rates up to 2,000 MHz, optical pulsewidths between 31 and 123 ps, and average power > 100 mW are demonstrated. The laser system is highly reliable and completely remotely controlled.

Poelker, M.; Hansknecht, J.

1996-12-31

209

Resistance and susceptibility to weight gain: individual variability in response to a high-fat diet.  

PubMed

An obesigenic environment is a potent force for promoting weight gain. However, not all people exposed to such an environment become obese; some remain lean. This means that some people are susceptible to weight gain (in a weight-promoting environment) and others are resistant. Identifying the characteristics of appetite control and food motivation in these two groups could throw light on the causes of weight gain and how this can be either treated or prevented. We have investigated the issue experimentally by identifying people who habitually consume a high-fat diet (greater than 43% fat energy). These individuals have been termed high-fat phenotypes. We have compared individuals, of the same age (mean=37 years old) and gender (male), who have gained weight (BMI=34) or who have remained lean (BMI=22). The susceptible individuals are characterised by a cluster of characteristics including a weak satiety response to fatty meals, a maintained preference for high-fat over low-energy foods in the post-ingestive satiety period, a strong hedonic attraction to palatable foods and to eating, and high scores on the TFEQ factors of Disinhibition and Hunger. The analysis of large databases suggests that this profile of factors contributes to an average daily positive energy balance from food of approximately 0.5 MJ. This profile of characteristics helps to define the symptomatology of a thrifty phenotype. PMID:16225895

Blundell, J E; Stubbs, R J; Golding, C; Croden, F; Alam, R; Whybrow, S; Le Noury, J; Lawton, C L

2005-12-15

210

High-gain meanderless slot arrays on electrically thick substrates at millimeter-wave frequencies  

Microsoft Academic Search

Introduces new techniques and architectures for the implementation of linear slot arrays on electrically thick dielectric substrates at millimeter-wave frequencies. The slot arrays are fed by a coplanar waveguide series line and lead to high gain by utilizing the phase cancellation technique to reduce coupling to the dominant surface-wave mode. Unlike traditional designs, no meander lines are used in the

Meide Qiu; Michael Simcoe; George V. Eleftheriades

2002-01-01

211

Synchronization and secure communication of chaotic systems via robust adaptive high-gain fuzzy observer  

Microsoft Academic Search

This paper proposes an alternative robust adaptive high-gain fuzzy observer design scheme and its application to synchronization and secure communication of chaotic systems. It is assumed that their states are immeasurable and their parameters are unknown. The structure of the proposed observer is represented by Takagi–Sugeno fuzzy model and has the integrator of the estimation error. It improves the performance

Chang-Ho Hyun; Chang-Woo Park; Jae-Hun Kim; Mignon Park

2009-01-01

212

High-gain, polarization-preserving, Yb-doped fiber amplifier for low-duty-cycle pulse amplification  

Microsoft Academic Search

Amplified spontaneous emission (ASE) suppression techniques were utilized to fabricate a double-pass, Yb-doped amplifier with the noise properties of a single-pass amplifier. Simulations based on a rate equation model were used to analyze the ASE and the effectiveness of the suppression techniques. These techniques were implemented in an alignment-free, double-pass, Yb-doped fiber amplifier with a 26 dB gain at a

J. R. Marciante; J. D. Zuegel

2006-01-01

213

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

DOEpatents

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.

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

2005-07-05

214

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

DOEpatents

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.

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

215

High gain coherent amplification in thermally stabilized InP:Fe crystals under dc fields.  

PubMed

After recalling the principal results of the theory of two-wave mixing gain enhancement in photorefractive InP:Fe crystals under a dc field, we report on experiments performed with several samples manufactured at CNET. For the first time, we believe, a maximum gain of 11.4 cm(-1) has been obtained under an applied dc field of 10 kV/cm in a thermally stablized crystal (T = 290 K) at lambda = 1.06 microm. In spite of a decrease in the factor n(3)r(eff)/lambda high gains (Gamma >/= 5 cm(-1)) have been achieved at lambda = 1.32microm in thick crystals. These experimental results are in good agreement with theoretical predictions. PMID:20567319

Ozkul, C; Picoli, G; Gravey, P; Wolffer, N

1990-06-20

216

A high gain wide dynamic range transimpedance amplifier for optical receivers  

NASA Astrophysics Data System (ADS)

As the front-end preamplifiers in optical receivers, transimpedance amplifiers (TIAs) are commonly required to have a high gain and low input noise to amplify the weak and susceptible input signal. At the same time, the TIAs should possess a wide dynamic range (DR) to prevent the circuit from becoming saturated by high input currents. Based on the above, this paper presents a CMOS transimpedance amplifier with high gain and a wide DR for 2.5 Gbit/s communications. The TIA proposed consists of a three-stage cascade pull push inverter, an automatic gain control circuit, and a shunt transistor controlled by the resistive divider. The inductive-series peaking technique is used to further extend the bandwidth. The TIA proposed displays a maximum transimpedance gain of 88.3 dB? with the -3 dB bandwidth of 1.8 GHz, exhibits an input current dynamic range from 100 nA to 10 mA. The output voltage noise is less than 48.23 nV/?Hz within the -3 dB bandwidth. The circuit is fabricated using an SMIC 0.18 ?m 1P6M RFCMOS process and dissipates a dc power of 9.4 mW with 1.8 V supply voltage.

Lianxi, Liu; Jiao, Zou; Yunfei, En; Shubin, Liu; Yue, Niu; Zhangming, Zhu; Yintang, Yang

2014-01-01

217

High gain GaAs photoconductive semiconductor switches for ground penetrating radar  

SciTech Connect

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 under ground because it can operate at low frequencies and at high average power. This paper will summarize the state-of-the-art in high gain GaAs switches and discuss their use in a radar transmitter. We will also present a summary of an analysis of the effectiveness of different pulser geometries that result in transmitted pulses with varying frequency content. To this end we developed a simple model that includes transmit and receive antenna response, attenuation and dispersion of the electromagnetic impulses by the soil, and target cross sections.

Loubriel, G.M.; Aurand, J.F.; Buttram, M.T.; Zutavern, F.J.; Helgeson, W.D.; O`Malley, M.W. [Sandia National Labs., Albuquerque, NM (United States); Brown, D.J. [Ktech Corp., Albuquerque, NM (United States)

1996-07-01

218

On the super-Gaussian unstable resonator for high-gain short-pulse laser media  

SciTech Connect

High-mode-volume high-energy (70 mJ) high-brightness (1.6 [times] 10[sup 14] W cm[sup [minus]2] Sr[sup [minus]1]) laser beams have been extracted from a high gain short-pulse XeCl laser with a super-Gaussian unstable resonator. These results are obtained by increasing the cavity magnification factor to 6.6 and the output mirror peak reflectivity to 78%. The output beam divergence is seen to decrease from an initial value of [approximately]0.2 mrad down to nearly diffraction limited after 6 ns for the short gain build-up time of the active medium.

Perrone, M.R. (Dipartimento di Fisica, Via per Arnesano (Italy)); Piegari, A.; Scaglione, S. (Laboratorio Film Sottili, ENEA Casaccia (Italy))

1993-05-01

219

High gain, Fast Scan, Broad Spectrum Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM  

SciTech Connect

During contract # DE-FG02-ER83545, Parallax Research, Inc. developed a High gain, Fast Scan Broad Spectrum Parallel beam Wavelength Dispersive X-ray Spectrometer for use on Scanning Electron Microscopes (SEM). This new spectrometer allows very fast high resolution elemental analysis of samples in an electron microscope. By comparison to previous WDS spectrometers, it can change from one energy position to another very quickly and has an extended range compared to some similar products.

OHara, David

2009-05-08

220

A Coherent Compton Backscattering High Gain FEL using an X-Band Microwave Undulator  

SciTech Connect

High power microwave sources at X-Band, delivering 400 to 500 of megawatts for about 400 ns, have been recently developed. These sources can power a microwave undulator with short period and large gap, and can be used in short wavelength FELs reaching the nm region at a beam energy of about 1 GeV. We present here an experiment designed to demonstrate that microwave undulators have the field quality needed for high gain FELs.

Tantawi, S.; Dolgashev, V.; Nantista, C.; /SLAC; Pellegrini, C.; Rosenzweig, J.; Travish, G.; /UCLA

2005-12-14

221

High-power optically pumped VECSEL using a double-well resonant periodic gain structure  

Microsoft Academic Search

We present the design and fabrication of an optically pumped vertical-external-cavity surface-emitting lasers with double-well resonant periodic gain structure. Each double-well consists of two 4-nm-thick InGaAs strained quantum wells. The double-well provides optimum overlap between the quantum wells and the antinodes of the standing wave of laser signal at high-power and high-temperature operation. The structure is more tolerant to variation

Li Fan; Jörg Hader; Marc Schillgalies; Mahmoud Fallahi; Aramais R. Zakharian; Jerome V. Moloney; Robert Bedford; James T. Murray; Stephan W. Koch; Wolfgang Stolz

2005-01-01

222

A differential low-voltage high gain current-mode integrated RF receiver front-end  

NASA Astrophysics Data System (ADS)

A differential low-voltage high gain current-mode integrated RF front end for an 802.11b WLAN is proposed. It contains a differential transconductance low noise amplifier (Gm-LNA) and a differential current-mode down converted mixer. The single terminal of the Gm-LNA contains just one MOS transistor, two capacitors and two inductors. The gate-source shunt capacitors, Cx1 and Cx2, can not only reduce the effects of gate-source Cgs on resonance frequency and input-matching impedance, but they also enable the gate inductance Lg1,2 to be selected at a very small value. The current-mode mixer is composed of four switched current mirrors. Adjusting the ratio of the drain channel sizes of the switched current mirrors can increase the gain of the mixer and accordingly increase the gain of RF receiver front-end. The RF front-end operates under 1 V supply voltage. The receiver RFIC was fabricated using a chartered 0.18 ?m CMOS process. The integrated RF receiver front-end has a measured power conversion gain of 17.48 dB and an input referred third-order intercept point (IIP3) of -7.02 dBm. The total noise figure is 4.5 dB and the power is only 14 mW by post-simulations.

Chunhua, Wang; Minglin, Ma; Jingru, Sun; Sichun, Du; Xiaorong, Guo; Haizhen, He

2011-02-01

223

Optically pumped high-power semiconductor disk laser with gain element engineered for wide tunability  

NASA Astrophysics Data System (ADS)

The layer structure of the gain element in an optically pumped semiconductor disk laser (OP-SDL) was designed for wide tunability. This was achieved by a parametric optimization of the structure, which in effect balanced the spectrally varying influence of the gain of the quantum wells, the longitudinal distribution of the standing wave lasing field in the structure, and the degree of resonance in the subcavity formed between the distributed Bragg reflector at the bottom and the air-semiconductor interface at the top. The quality measure in the optimization was the spectral reflectance of the gain element for light incident from the external cavity at low power. This unsaturated reflectance was compared to its target function, which was constant at a specified value larger than unity over a wide, prescribed wavelength range. The fabricated gain element was used in a linear OP-SDL with a rotatable intra-cavity birefringent filter for wavelength tuning. The design principles for achieving wide tunability were experimentally validated by the strong agreement between measurements and simulations of the spectral threshold pump intensity. Furthermore, tuning experiments at high pump powers were performed showing that the lasing wavelength could be tuned from 967 nm to 1010 nm with a maximum output power of 2.6 W.

Borgentun, C.; Bengtsson, J.; Larsson, A.; Demaria, F.; Hein, A.; Unger, P.

2010-04-01

224

CMOS highly linear direct-conversion transmitter for WCDMA with fine gain accuracy  

NASA Astrophysics Data System (ADS)

A highly linear, high output power, 0.13 ?m CMOS direct conversion transmitter for wideband code division multiple access (WCDMA) is described. The transmitter delivers 6.8 dBm output power with 38 mA current consumption. With careful design on the resistor bank in the IQ-modulator, the gain step accuracy is within 0.1 dB, hence the image rejection ratio can be kept below -47 dBc for the entire output range. The adjacent channel leakage ratio and the LO leakage at 6.8 dBm output power are -44 dBc @ 5 MHz and -37 dBc, respectively, and the corresponding EVM is 3.6%. The overall gain can be programmed in 6 dB steps in a 66-dB range.

Xin, Li; Jian, Fu; Yumei, Huang; Zhiliang, Hong

2011-08-01

225

High-Gain Harmonic-Generation Free-Electron Laser Seeded by Harmonics Generated in Gas  

NASA Astrophysics Data System (ADS)

The injection of a seed in a free-electron laser (FEL) amplifier reduces the saturation length and improves the longitudinal coherence. A cascaded FEL, operating in the high-gain harmonic-generation regime, allows us to extend the beneficial effects of the seed to shorter wavelengths. We report on the first operation of a high-gain harmonic-generation free-electron laser, seeded with harmonics generated in gas. The third harmonics of a Ti:sapphire laser, generated in a gas cell, has been amplified and up-converted to its second harmonic (?rad=133nm) in a FEL cascaded configuration based on a variable number of modulators and radiators. We studied the transition between coherent harmonic generation and superradiant regime, optimizing the laser performances with respect to the number of modulators and radiators.

Labat, M.; Bellaveglia, M.; Bougeard, M.; Carré, B.; Ciocci, F.; Chiadroni, E.; Cianchi, A.; Couprie, M. E.; Cultrera, L.; Del Franco, M.; di Pirro, G.; Drago, A.; Ferrario, M.; Filippetto, D.; Frassetto, F.; Gallo, A.; Garzella, D.; Gatti, G.; Giannessi, L.; Lambert, G.; Mostacci, A.; Petralia, A.; Petrillo, V.; Poletto, L.; Quattromini, M.; Rau, J. V.; Ronsivalle, C.; Sabia, E.; Serluca, M.; Spassovsky, I.; Surrenti, V.; Vaccarezza, C.; Vicario, C.

2011-11-01

226

Chromosome 17/17q gain and unaltered profiles in high resolution array-CGH are prognostically informative in neuroblastoma.  

PubMed

The prognostic relevance of chromosome 17 gain in neuroblastoma is still discussed. This investigation specifies the frequency, type, size, and transcriptional relevance in a large patient cohort. Primary tumor material of 202 patients was analyzed using high-resolution oligonucleotide array-based comparative genomic hybridization (aCGH) and correlated with clinical and survival data. A subset (n?=?145) was correlated for differentially expressed genes (DEG) by microarray analysis. Chromosome 17 aCGH analysis showed numerical gain in 94/202 patients (47%), partial gain in 93/202 patients (46%), and no gain in 15/202 patients (7%). The frequency of partial gain was higher in stage 4 neuroblastoma (stage 1 15%; stage 2 12%; stage 3 16%; stage 4S 7%; and stage 4 50%). Overall survival (OS) was superior in patients with numerical gain compared with patients with partial gain or no gain (5-y-OS: 0.95?±?0.02 vs. 0.63?±?0.05 vs. 0.60?±?0.13; P?gain. Only one DEG (CCKBR) was detected comparing tumors with partial gain and those with no gain. In patients with partial gain, the distribution of breakpoints did not correlate with stage and 11q status, but with MYCN amplification and 1p status. The "best" breakpoints in cases with partial 17q gain were at 42.5 Mb for event-free and 26.6 Mb for OS. Numerical gain of chromosome 17 is associated with a better prognosis than partial and no gain. The group of tumors with partial gain was similar to the group without gain with respect to stage distribution, outcome, and gene expression profile. © 2014 Wiley Periodicals, Inc. PMID:24737690

Theissen, Jessica; Oberthuer, Andre; Hombach, Anja; Volland, Ruth; Hertwig, Falk; Fischer, Matthias; Spitz, Ruediger; Zapatka, Marc; Brors, Benedikt; Ortmann, Monika; Simon, Thorsten; Hero, Barbara; Berthold, Frank

2014-08-01

227

Highly elevated emission of mercury vapor due to the spontaneous combustion of refuse in a landfill  

NASA Astrophysics Data System (ADS)

Refuse disposal (e.g., landfilling and incineration) have been recognized as a significant anthropogenic source of mercury (Hg) emission globally. However, in-situ measurements of Hg emission from landfill or refuse dumping sites where fugitive spontaneous combustion occurs have not been reported. Gaseous elemental mercury (Hg0) concentration and emission flux were observed near spontaneous combustions of refuse at a landfill site in southwestern China. Ambient Hg0 concentrations above the refuse surface ranged from 42.7 ± 20.0 to 396.4 ± 114.2 ng m-3, up to 10 times enhancement due to the spontaneous burning. Using a box model with Hg0 data obtained from 2004 to 2013, we estimated that the Hg0 emission from refuse was amplified by 8-40 times due to spontaneous combustion. A micrometeorological flux measurement system based on relaxed eddy accumulation was configured downwind of the combustion sites to quantify the Hg0 emission. Extremely large turbulent deposition fluxes (up to -128.6 ?g m-2 h-1, 20 min average) were detected during periods of high Hg0 concentration events over the measurement footprint. The effect of temperature, moisture and light on the air-surface exchange of Hg0 exchange was found to be masked by the overwhelming deposition of Hg0 from the enriched air from the refuse combustion plumes. This research reveals that mercury emission from the landfill refuse can be boosted by fugitive spontaneous combustion of refuse. The emission represents an anthropogenic source that has been overlooked in Hg inventory estimates.

Zhu, Wei; Sommar, Jonas; Li, Zhonggen; Feng, Xinbin; Lin, Che-Jen; Li, Guanghui

2013-11-01

228

Measuring the rates of spontaneous vortex formation in highly oblate Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

By studying the dynamics of the Bose-Einstein condensation transition in highly oblate (˜11:1 aspect ratio) traps, we have measured the dependence of spontaneous vortex formation on BEC growth rate, extending our previous experimental and numerical observations of spontaneous vortex formation in weakly oblate (˜2:1 aspect ratio) traps [1]. Our condensation procedure in these highly oblate traps allows us to create BECs over a large range of growth times, from approximately 200 ms to over 2 s. By characterizing vortex formation vs. BEC growth rate, and comparing experimental and numerical results, the Kibble-Zurek mechanism for topological defect formation may be quantitatively studied in our system. [1] C.N. Weiler, T.W. Neely, D.R. Scherer, A.S. Bradley, M.J. Davis, and B.P. Anderson., Nature 455, 948 (2008).

Neely, Tyler; Samson, Edward; Bradley, Ashton; Davis, Matthew; Anderson, Brian

2009-05-01

229

Approximate high-gain observers for non-Lipschitz observability forms  

Microsoft Academic Search

A methodology for the design of continuous practical high-gain observers for non-linear observable systems is presented. Only two conditions are required: injectivity of the observability map of order n and uniform continuity of its inverse. Using this map, the system is transformed to observability normal form, which could have a non-Lipschitz continuous right-hand side and eventually multiplicity of solutions. A

Alejandro Vargas; Jaime A. Moreno

2005-01-01

230

Output feedback control of hypersonic vehicles based on neural network and high gain observer  

Microsoft Academic Search

In this paper, the output feedback control problem for a genetic hypersonic vehicle is considered under the restriction that\\u000a only the vehicle’s velocity and altitude are measurable. High gain observers (HGO) are utilized to provide estimation signals\\u000a for unmeasurable derivatives of the vehicle’s velocity and altitude. Neural network based feedforward function is designed\\u000a to compensate for model uncertainties. The proposed

XinDong Li; Bin Xian; Chen Diao; YanPing Yu; KaiYan Yang; Yao Zhang

2011-01-01

231

Lyapunov-based switching control of nonlinear systems using high-gain observers  

Microsoft Academic Search

We consider output feedback stabilization of uniformly observable uncertain nonlinear systems when the uncertain parameters belong to a known but comparably large compact set. In a previous paper, we proposed a new logic-based switching control to improve the performance of continuous high-gain-observer-based sliding mode controllers. Our main goal here is to show that similar techniques can be exploited for solving

Leonid B. Freidovich; Hassan K. Khalil

2007-01-01

232

Global tracking sliding mode control for uncertain nonlinear systems based on variable high gain observer  

Microsoft Academic Search

An output-feedback sliding mode controller is proposed for a class of single-input-single-output (SISO) uncertain nonlinear systems. The sliding surface is generated using the state of a high gain observer (HGO) while the control signal amplitude is generated from a norm observer free of peaking. The proposed scheme achieves global tracking with respect to a small residual set by means of

Alessandro J. Peixoto; Liu Hsu; Ramon R. Costa; Fernando Lizarralde

2007-01-01

233

Robustness of high-gain observer-based nonlinear controllers to unmodeled actuators and sensors  

Microsoft Academic Search

We investigate the robust stabilization of a class of nonlinear systems in the presence of unmodeled actuator and sensor dynamics. We show that, given any globally bounded stabilizing state-feedback control, the closed-loop system performance can be recovered by a sufficiently fast high-gain observer in the presence of sufficiently fast actuator and sensor dynamics. The performance recovery includes recovery of exponential

Magdi S. Mahmoud; Hassan K. Khalil

2002-01-01

234

Robust Stabilization of Non-Minimum Phase Nonlinear Systems Using Extended High-Gain Observers  

Microsoft Academic Search

A robust, stabilizing output feedback controller for systems in the normal form, which could potentially in- clude unstable zero dynamics, is presented. The control scheme adopted herein incorporates continuously-implemented sliding mode control—chosen for its robustness properties as well as its ability to prescribe or constrain the motion of trajectories in the sliding phase—and an extended high gain observer to estimate

Shahid Nazrulla; Hassan K. Khalil

2011-01-01

235

Multirate Sampled-Data Output Feedback Using High-Gain Observers  

Microsoft Academic Search

We consider multirate sampled-data output feedback control of a class of nonlinear systems using high-gain observers where the analog-to-digital sampling rate is faster than the digital-to-analog sampling rate. We show that if a single-rate sampled-data state feedback controller globally stabilizes the origin, then the multirate output feedback controller achieves semiglobal practical stabilization

Jeffrey H. Ahrens; Hassan K. Khalil

2006-01-01

236

High-gain observation with disturbance attenuation and application to robust fault detection  

Microsoft Academic Search

One approach to the problem of residual generation in a purpose of fault detection is to use an observer. One particular difficulty is to distinguish between faults and disturbances. Various observers have already been inspected in that direction, generally based on exact decoupling w.r.t. unknown disturbances. Here the use of high-gain observer techniques is inspected, with a purpose of attenuation

Gildas Besançon

2003-01-01

237

High-Voltage-Gain CMOS LNA For 6–8.5GHz UWB Receivers  

Microsoft Academic Search

The design of a fully integrated CMOS low noise amplifiers (LNA) for ultra-wide-band (UWB) integrated receivers is presented. An original LC input matching cell architecture enables fractional bandwidths of about 25%, with practical values, that match the new ECC 6-8.5-GHz UWB frequency band. An associated design method which allows low noise figure and high voltage gain is also presented. Measurements

Marc Battista; Jean Gaubert; Matthieu Egels; Sylvain Bourdel; HervÉ Barthelemy

2008-01-01

238

Status of the UCLA high-gain infrared free electron laser  

Microsoft Academic Search

A compact, infrared (10-20 ?m), high-gain FEL is being commissioned at the Particle Beam Physics Laboratory (PBPL) at UCLA. A 60 cm long undulator with a period of 1.5 cm and an undulator parameter K-l has been built to be used in conjunction with the PBPL beam. Experiments will focus on EEL physics pertinent to proposed short wavelength devices. Of

M. Hogan; C. Pellegrini; J. Rosenzweig; G. Travish; A. Varfolomeev

1995-01-01

239

High-Gain Yagi-Uda Antennas for Millimeter-Wave Switched-Beam Systems  

Microsoft Academic Search

A high-efficiency microstrip-fed Yagi-Uda antenna has been developed for millimeter-wave applications. The antenna is built on both sides of a Teflon substrate (epsivr = 2.2) which results in an integrated balun for the feed dipole. A 7-element design results in a measured gain of 9-11 dB at 22-26 GHz with a cross-polarization level of < - 16 dB. The antenna

Ramadan A. Alhalabi; Gabriel M. Rebeiz

2009-01-01

240

Longitudinal Coherence Preservation and Chirp Evolution in a High Gain Laser Seeded Free Electron Laser Amplifier  

SciTech Connect

In this letter we examine the start-up of a high gain free electron laser in which a frequency-chirped coherent seed laser pulse interacts with a relativistic electron beam. A Green function formalism is used to evaluate the initial value problem. We have fully characterized the startup and evolution through the exponential growth regime. We obtain explicit expressions for the pulse duration, bandwidth and chirp of the amplified light and show that the FEL light remains fully longitudinally coherent.

Murphy, J.B.; /BNL, NSLS; Wu, Juhao; /SLAC; Wang, X.J.; Watanabe, T.; /BNL, NSLS

2006-06-07

241

High-Gain Fully Printed Organic Complementary Circuits on Flexible Plastic Foils  

Microsoft Academic Search

We present several fully printed organic complemen- tary circuits using n- and p-type organic thin-film transistors. n-Type and p-type devices are developed on a flexible poly- ethylene-naphthalate substrate. All organic layers are deposited using a low-cost screen-printing technique. The inverters show a high gain and a switching point at exactly V DD\\/2. A seven-stage voltage-controlled oscillator (VCO) is designed with

A. Daami; E. Bergeret; E. Benevent; P. Pannier; R. Coppard; Mathieu Guerin

2011-01-01

242

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

Microsoft Academic Search

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.

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

243

Electric-field-assisted gain control in a high-power picosecond laser diode  

NASA Astrophysics Data System (ADS)

A laser diode structure has lately been reported that is capable of generating high-power picosecond optical pulses (~ 50 W / 20 ps) in the near-infrared range for laser radars and other applications. The physical idea consists of achieving fast gain control through the effect of a transverse electric field on the carrier distribution across the active region, which controls the local gain and local absorption at each instant. The mechanism of field-assisted gain control, which has so far been formulated only as a qualitative idea, is justified in this work by simulations of the carrier transport and laser response using the semiconductor device simulator "Atlas" (Silvaco Inc.). A simplified approach is adopted which replaces photon-assisted carrier transport with carrier penetration over the lowered potential barrier. This points to reasonably good agreement between the experimental and simulation results for picosecond pulse generation, provided that the carrier mobilities are assumed to be higher than those in the heavily doped semiconductor structure by a factor of ~ 4. One important conclusion is that comprehensive modelling of the operation of the experimental laser diode is not possible without considering photon-assisted carrier transport, which has not been studied so far at very high carrier densities (exceeding the transparency concentration).

Vainshtein, Sergey N.; Yuferev, Valentin; Kostamovaara, Juha T.

2003-03-01

244

Precision motion control with a high gain disturbance compensator for linear motors.  

PubMed

In this paper, we address the problem relating to the precision control of permanent magnet linear motors to track repeated motion trajectories. A high gain disturbance compensator is developed to improve the control performance degraded due to the presence of significant disturbances. An inverse gain of the overall system model is used to set up a disturbance observer. The observed disturbance is then used to generate a "knocker" signal, to be augmented to the control signal, which can provide the additional energy necessary to overcome the effects of the disturbances. A learning scheme is used to adjust the knocker signal iteratively over the repeated cycles. Simulation and experimental results are furnished to demonstrate the effectiveness of the proposed control scheme. PMID:15272795

Tan, Kok Kiong; Zhao, Shao

2004-07-01

245

Simulation and parameters optimization of high gain silicon micro-pixel avalanche photodiode  

NASA Astrophysics Data System (ADS)

In this paper, the silicon avalanche photodiode (Si-APD) size in micron, which was comprised of separate layer of absorption charge and multiplication (SACM) has been studied. The influence of different thicknesses and different doping concentration of the absorption, charge and multiplication layer on the electric field distribution, current-voltage characteristic and breakdown voltage were simulated and analyzed respectively. The structural parameters optimization has be done with the simulation results. The results show that the better gain and low bias voltage can be achieved with layer thicknesses in micro/nano-sized, which can give a high gain of 106 and low bias voltage of 127V. Also the fabrication process conditions has been given.

Sun, Fangkui; Gu, Huaiqi; Wang, Zhiwei; Chen, Lixue

2012-11-01

246

Effects of bandwidth, compression speed, and gain at high frequencies on preferences for amplified music.  

PubMed

This article reviews a series of studies on the factors influencing sound quality preferences, mostly for jazz and classical music stimuli. The data were obtained using ratings of individual stimuli or using the method of paired comparisons. For normal-hearing participants, the highest ratings of sound quality were obtained when the reproduction bandwidth was wide (55 to 16000 Hz) and ripples in the frequency response were small (less than ± 5 dB). For hearing-impaired participants listening via a simulated five-channel compression hearing aid with gains set using the CAM2 fitting method, preferences for upper cutoff frequency varied across participants: Some preferred a 7.5- or 10-kHz upper cutoff frequency over a 5-kHz cutoff frequency, and some showed the opposite preference. Preferences for a higher upper cutoff frequency were associated with a shallow high-frequency slope of the audiogram. A subsequent study comparing the CAM2 and NAL-NL2 fitting methods, with gains slightly reduced for participants who were not experienced hearing aid users, showed a consistent preference for CAM2. Since the two methods differ mainly in the gain applied for frequencies above 4 kHz (CAM2 recommending higher gain than NAL-NL2), these results suggest that extending the upper cutoff frequency is beneficial. A system for reducing "overshoot" effects produced by compression gave small but significant benefits for sound quality of a percussion instrument (xylophone). For a high-input level (80 dB SPL), slow compression was preferred over fast compression. PMID:23172008

Moore, Brian C J

2012-09-01

247

Research on a novel high gain model for dispersive spectrographic systems  

NASA Astrophysics Data System (ADS)

Traditional dispersive spectrographic systems usually base on slit imaging. The entrance slit can ensure a remarkable spectral resolution but a loss of system throughput and vice versa, thus this kind of instruments can't achieve Jacquinot advantage and Fellgett advantage simultaneously and statically. To derive a high gain model for the stationary dispersive systems with these two advantages, traditional single-slit and the multi-slit spectrographic systems were studied. A method for single channel spectrum abstraction in a multi-slit spectrographic system was derived. This method demonstrates that if each individual slit in a multi-slit system possesses a transformation form of orthogonal independent column codes, the spectrum of each individual slit can be abstracted from superposed spectrum, spectral resolution of equivalent single-slit system is obtained and the system achieves dual advantages. This high gain computational system model is applicable for almost all kinds of existing dispersive spectrographic systems. Furthermore individual coded slits can be integrated as a coded aperture to increase system's integration level and reduce off-axis aberration. Based on the derivation of theoretical model, two kinds of coding forms' mathematical models were studied. To verify the derived theory, a testing system with a specially designed flat-field holographic concave grating and a coded aperture of order 16 Hadamard matrix form was set up. The experiment indicated that although optical aberration and other system noise were involved, this high gain system model could still achieve a high spectral resolution of 0.4nm as single-slit system, while remarkable system etendue (8X) and SNR (4X) were also obtained, which proved the correctness of the theoretical derivation.

Cheng, Liang; Ye, Zi; Gong, Xingzhi; Yu, Feihong

2008-03-01

248

High-performance adhesives resulting from spontaneous formation of nanogels within miniemulsion particles.  

PubMed

Molecular structure plays a crucial role in determining the final properties of pressure-sensitive adhesives. Here, we demonstrate that the molecular structure of polyurethane/(meth)acrylic hybrids synthesized by miniemulsion photopolymerization changes during storage of the dispersion at room temperature because of the spontaneous formation of nanogels by the assembly of polymer chains within the polymer particles. Analysis of the nanogel structure by asymmetric-flow field-flow fractionation allows identification of the molecular structure that provides the unusual combination of high tack adhesion and excellent shear resistance at high temperature [maximum value of the shear-adhesion failure temperature (SAFT) test, >210 °C]. PMID:24484476

Daniloska, Vesna; Carretero, Paula; Tomovska, Radmila; Paulis, Maria; Asua, José M

2014-03-12

249

Broadband optical parametric gain by novel highly nonlinear tellurite hybrid microstructured optical fiber with four zero-dispersion wavelengths  

NASA Astrophysics Data System (ADS)

Fiber-optical parametric amplification (FOPA) has been intensively studied and exploited for various interesting applications such as wavelength conversion, wavelength division multiplexing, optical signal processing and so on. However, its efficiency is governed by the fiber nonlinearity and chromatic dispersion. By employing tellurite glass we propose novel highly nonlinear tellurite hybrid microstructured optical fibers (HMOFs) which have nonlinearity of 6642 W-1km-1 and near-zero flattened dispersion profiles from 1.3 to 2.3 ?m with four zero dispersion wavelengths for FOPA applications. The linear phase-mismatch, optical signal gain and gain bandwidth are precisely calculated by using a full propagation constant which includes the contribution of all high-order dispersion parameters. In contrast with silica fibers, the signal gain is shown to be generated in the wavelength regions where ??<-4?P and the parametric gain coefficient g is imaginary. It is shown that the proposed tellurite HMOFs with short fiber length L<90 cm have the gain bandwidth as broad as 760 nm when it is pumped at 1550 nm. The increase in pump power from 1 to 4 W not only increases the signal gain but also broadens the FOPA gain bandwidth. At 1700-nm pump wavelength, the signal gain larger than 14 dB is obtained over a very broad gain bandwidth of 1200 nm (from 1290 to 2490 nm). To our best knowledge, it is the first time that highly nonlinear tellurite HMOFs are demonstrated as attractive candidates for high performance of FOPA.

Tuan, Tong Hoang; Cheng, Tonglei; Asano, Koji; Duan, Zhongchao; Suzuki, Takenobu; Ohishi, Yasutake

2014-03-01

250

Compact ultra-high gain multi-pass Nd:YAG amplifier with a low passive reflection phase conjugate mirror  

Microsoft Academic Search

We show a compact multi-pass amplifier, based on a single dual-rod laser-head which produces ultra-high gain. A double-pass produced a maximum small signal gain of 4×108. Another double-pass was permitted by including a specially designed Brillouin phase conjugate mirror (PCM). This enabled a total gain of 7.7×1010, which raised an input signal of 10 pJ to 770 mJ output signal.

Yitshak Tzuk; Yaakov Glick; Michael M. Tilleman

1999-01-01

251

High gain FEL amplification of charge modulation caused by a hadron  

SciTech Connect

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.

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

2008-08-24

252

Method and system for modulation of gain suppression in high average power laser systems  

DOEpatents

A high average power laser system with modulated gain suppression includes an input aperture associated with a first laser beam extraction path and an output aperture associated with the first laser beam extraction path. The system also includes a pinhole creation laser having an optical output directed along a pinhole creation path and an absorbing material positioned along both the first laser beam extraction path and the pinhole creation path. The system further includes a mechanism operable to translate the absorbing material in a direction crossing the first laser beam extraction laser path and a controller operable to modulate the second laser beam.

Bayramian, Andrew James (Manteca, CA)

2012-07-31

253

Sub-Poissonian shot noise of a high internal gain injection photon detector.  

PubMed

The noise performance of an infrared injection photon detector with very high internal gain was investigated at a wavelength of 1.55 mum. The devices showed sub-Poissonian shot noise with Fano factors around 0.55 at 0.7 V at room temperature. Optical to electrical conversion factors of 3000 electrons per absorbed photon were recorded at 0.7 V. The change in noise-equivalent power with respect to bias voltage was evaluated. The optical to electrical conversion factor and Fano factor were measured under increasing illumination and compared to theoretical expectations. PMID:18711508

Memis, Omer Gokalp; Katsnelson, Alex; Kong, Soon-Cheol; Mohseni, Hooman; Yan, Minjun; Zhang, Shuang; Hossain, Tim; Jin, Niu; Adesida, Ilesanmi

2008-08-18

254

The use of optically triggered, high gain GaAs switches for UWB pulse generation  

SciTech Connect

A high peak power impulse pulser that is controlled with high gain, optically triggered GaAs Photoconductive Semiconductor Switches (PCSS) has been constructed and tested. The system has a short 50 {Omega} line that is charged to 100 kV and discharged through the switch when the switch is triggered with as little as 90 nJ of laser energy. The laser that is used is a small laser diode array whose output is delivered through a fiber to the switch. The current in the system ranges from 1 kA (with one laser) to 1.3 kA (with two) and the pulse widths are 1.9 and 1.4 ns, respectively. The peak power and the energy delivered to the load are 50 MW to 84 MW and 95 NJ to 120 mJ for one or two lasers. The small trigger energy and switch jitter are due to a high gain switching mechanism in GaAs. This experiment also shows a relationship between the rise time of the voltage across the switch and the required trigger energy and switch jitter.

Loubriel, G.M.; Zutavern, F.J.; O`Malley, M.W.; Gallegos, R.R.; Helgeson, W.D.

1994-04-01

255

Ground penetrating radar enabled by high gain GaAs photoconductive semiconductor switches  

SciTech Connect

The ability of high gain GaAs Photoconductive Semiconductor switches (PCSS) to deliver fast risetime, low jitter pulses when triggered with small laser diode arrays makes them suitable for their use in ultrawide bandwidth (UWB), impulse transmitters. This paper will summarize the state-of-the-art in high gain GaAs switches and discuss how GaAs switches are being implemented in a transmitter for detection of underground structures. The advantage of this type of semiconductor switch is demonstrated operation at high voltages (100 kV) and repetition rates (1 kHz) with the potential for much higher repetition rates. The latter would increase the demonstrated average powers of 100 W to 1 kW and higher. We will also present an analysis of the effectiveness of different pulser geometries that result in transmitted pulses with varying frequency content. To this end, we have developed a simple model that includes transmit and receive antenna response, attenuation and dispersion of the electromagnetic impulses by the soil, and target cross sections.

Loubriel, G.M.; Buttram, M.T.; Aurand, J.F.; Zutavern, F.J.

1996-06-01

256

High gain GaAs Photoconductive Semiconductor Switches for impulse sources  

SciTech Connect

A high peak power impulse pulser that is controlled with high gain, optically triggered GaAs Photoconductive Semiconductor Switches (PCSS) has been constructed and tested. The system has a short 50 {Omega} line that is charged to 100 kV and discharged through the switch when the switch is triggered with as little as 90 nJ of laser energy. We have demonstrated that the GaAs switches can be used to produce either a monocycle or a monopulse with a period or total duration of about 3 ns. For the monopulse, the voltage switched was above 100 kV, producing a peak power of about 48 MW to the 30 {Omega} load at a burst repetition rate of 1 kHz. The laser that is used is a small laser diode array whose output is delivered through a fiber to the switch. The current in the system has rise times of 430 ps and a pulse width of 1.4 ns when two laser diode arrays are used to trigger the switch. The small trigger energy and switch jitter are due to a high gain switching mechanism in GaAs.

Loubriel, G.M.; Zutavern, F.J.; O`Malley, M.W.; Helgeson, W.D.

1994-11-01

257

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

NASA Technical Reports Server (NTRS)

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.

Ostroff, Aaron J.

1998-01-01

258

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

259

High-gain integral dynamic compensation robust control for a satellite with mobile body  

NASA Astrophysics Data System (ADS)

A robust control law using high-gain integral dynamic compensation is introduced for the slew maneuver control of a satellite with one mobile body. The movement of such a mobile body disturbs the satellite attitude and changes the inertia of the whole satellite significantly. The proposed method regards the model uncertainties and exogenous disturbances as unknown inputs to the plant and then a high-gain integrator together with a lead filter is used as an unknown input observer. The observed values are used to compensate the dynamic uncertainties. The unit quaternion is used to represent the orientation which allows overcoming problems arising from representation singularities. The kinematics of the quaternion and angular velocity have a standard form that the backstepping method is used and a Lyapunov candidate function is constructed. Under a certain frequency domain assumption, we can prove the boundedness of the states and the bounds can be designed to be arbitrarily small. Numerical simulation shows the effectiveness of the propsed controller.

Zhang, Zhao; Hu, Jun

2009-12-01

260

Longevity improvement of optically activated, high gain GaAs photoconductive semiconductor switches  

SciTech Connect

The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses at 23A, and over 100 pulses at 1kA. This is achieved by improving the ohmic contacts by doping the semi-insulating GaAs underneath the metal, and by achieving a more uniform distribution of contact wear across the entire switch by distributing the trigger light to form multiple filaments. This paper will compare various approaches to doping the contacts, including ion implantation, thermal diffusion, and epitaxial growth. The device characterization also includes examination of the filament behavior using open-shutter, infra-red imaging during high gain switching. These techniques provide information on the filament carrier densities as well as the influence that the different contact structures and trigger light distributions have on the distribution of the current in the devices. This information is guiding the continuing refinement of contact structures and geometries for further improvements in switch longevity.

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

2000-03-02

261

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

SciTech Connect

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.

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

262

Design of a novel mixer with high gain and linearity improvement for DRM/DAB applications  

NASA Astrophysics Data System (ADS)

This paper focuses on a new design of a down-conversion mixer for a low-IF wideband receiver. Based on the folded structure and differential multiple gated transistor (DMGTR) technique, a novel quadrature mixer with a high conversion gain, a moderate linearity, and a moderate NF is proposed. The mixer is designed and implemented in a 0.18-?m CMOS process, and can operate in a frequency range from 150 kHz to 1.5 GHz. The circuit performance is confirmed by both simulation and measurement results. The measurement results exhibit a peak conversion gain of 13.35 dB, a high third order input referred intercept point of 14.85 dBm, and a moderate single side band noise figure of 10.67 dB. Moreover, the whole quadrature mixer core occupies a compact die area of 0.122 mm2. It consumes a current of 3.96 mA (excluding the output buffers) under a single supply voltage of 1.8 V.

Yiqiang, Wu; Zhigong, Wang; Jian, Xu; Jian, Wang; Ouli, Zhang; Lu, Tang

2013-01-01

263

A combined high gain observer and high-order sliding mode controller for a DFIG-based wind turbine  

Microsoft Academic Search

This paper deals 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 strategy combines an MPPT using a high gain observer and second-order sliding mode for the DFIG control. This strategy presents attractive features such as chattering-free behavior,

B. Beltran; M. E. H. Benbouzid; T. Ahmed-Ali

2010-01-01

264

Theoretical study of the design and performance of a high-gain, high-extraction-efficiency FEL oscillator  

SciTech Connect

We present the results of theoretical and simulation studies of the design and performance of a new F type of FEL oscillator. This device, known by the acronym RAFEL for Regenerative Amplifier Free-Electron Laser, will be constructed in the space presently occupied by the AFEL (Advanced FEL) at Los Alamos, and will be driven by an upgraded (to higher average power) version of the present AFEL linac. In order to achieve a long-time-averaged optical output power of {approximately} 1 kW using an electron beam with an average power of {approximately} 20 kW, a rather high extraction efficiency {eta} {approximately} 5% is required. We have designed a 2-m-long undulator to attain this goal: the first meter is untapered and provides high gain while the second meter is linearly-tapered in magnetic field amplitude to provide high extraction efficiency in the standard K-M-R manner. Two-plane focusing and linear polarization of the undulator are assumed. Electron-beam properties from PARMEIA simulations of the AFEL accelerator were used in the design. A large saturated gain, {approximately} 500, requires a very small optical feedback to keep the device operating at steady-state. However, the large gain leads to distorted optical modes which require two- and three-dimensional simulations to adequately treat diffraction effects. This FEL will be driven by 17 MeV electrons and will operate in the 16 {mu}m spectral region.

Goldstein, J.; Nguyen, D.C.; Sheffield, R.L.

1996-10-01

265

High-power picosecond laser diodes based on different methods of fast gain control for high-precision radar applications  

NASA Astrophysics Data System (ADS)

Current-pumped picosecond-range laser diodes with a peak power significantly exceeding that achievable from gainswitched lasers are of major interest for a large variety of commercial applications. A group of phenomena have been explored in which the peak transient gain is efficiently controlled by a fast reduction in the pumping current. Common to all these phenomena is the fact that the peak powers of the emitted picosecond optical pulses (15-100 ps) exceed that obtainable from gain-switched laser diodes by at least an order of magnitude, although the physical reasons for the high gain and the design principles of the semiconductor structures are different. The main problem in the realization of these picosecond modes in low-cost practical systems is the high sensitivity of the operation regime to structural and circuit parameters. A related problem is the questionable reproducibility of the fabrication processes used so far. Proper development of reliable high-power picosecond transmitters will require the use of more advanced fabrication methods and further study of the effect of structural parameters on the properties of the picosecond lasing mode. In this paper we report on a record value for the power density of the picosecond lasing (50W / 30ps) obtained from a laser diode chip of width 20 ?m and give a qualitative interpretation of the operating mode. Use of the MOCVD process for diode fabrication should allow reproducible technology for picosecond laser diodes to be developed.

Vainshtein, Sergey; Kostamovaara, Juha; Lantratov, Vladimir; Kaluzhniy, Nikolay; Mintairov, Sergey

2007-05-01

266

Adverse cardiac remodelling in spontaneously hypertensive rats: acceleration by high aerobic exercise intensity  

PubMed Central

In the present study it was hypothesized that voluntary aerobic exercise favours a pro-fibrotic phenotype and promotes adverse remodelling in hearts from spontaneously hypertensive rats (SHRs) in an angiotensin II-dependent manner. To test this, female SHRs at the age of 1 year were started to perform free running wheel exercise. Captopril was used to inhibit the renin–angiotensin system (RAS). Normotensive rats and SHRs kept in regular cages were used as sedentary controls. Training intensity, expressed as mean running velocity, was positively correlated with the left ventricular mRNA expression of TGF-?1, collagen-III and biglycan but negatively correlated with the ratio of sarcoplasmic reticulum Ca2+-ATPase (SERCA)2a to Na+–Ca2+ exchanger (NCX). A pro-fibrotic phenotype was verified by Picrosirius red staining. Sixty-seven per cent of SHRs performing free running wheel exercise died either spontaneously or had to be killed during a 6 month follow-up. In the presence of captopril, aerobic exercise did not show a similar positive correlation between training intensity and the expression of fibrotic markers. Moreover, in SHRs receiving captopril and performing free running wheel exercise, a training intensity-dependent reverse remodelling of the SERCA2a-to-NCX ratio was observed. None of these rats died spontaneously or had to be killed. In captopril-treated SHRs performing exercise, expression of mRNA for decorin, a natural inhibitor of TGF-?1, was up-regulated. Despite these differences between SHR-training groups with and without captopril, positive training effects (lower resting heart rate and no progression of hypertension) were found in both groups. In conclusion, high aerobic exercise induces an angiotensin II-dependent adverse remodelling in chronic pressure overloaded hearts. However, high physical activity can potentially induce reverse remodelling in the presence of RAS inhibition.

da Costa Rebelo, Rui Manuel; Schreckenberg, Rolf; Schluter, Klaus-Dieter

2012-01-01

267

Fluorescent and highly stable unimodal DMPC based unilamellar vesicles formed by spontaneous curvature.  

PubMed

The formation of uniform and highly stable unilamellar vesicles (ULVs) and the theory behind it are ongoing tasks within the vesicle community. Herein, we report the formation of highly stable, fluorescent, and unimodal 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) based ULVs with an average size of ~100 nm, as determined by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). The ULVs are formed by mixing a two-component powder mixture or mixed lipid film of DMPC and 5 mol % of a novel amphiphilic carbenium salt, sodium 2-didecylamino-6,10-bis(N-methyltaruino)-4,8,12-trioxatriangulenium (Na-DSA) in aqueous solution when subjected to shaking. We propose that the high stability and the unimodal size distribution of the 5% DSA ULVs confirmed by DLS studies are a product of spontaneous curvature. UV-vis absorption/emission studies reveal that the structure of DSA promotes a strong interaction between the DMPC and the DSA to take place due to the complementary charge distribution of the DSA and DMPC head groups. The strong interaction may introduce an asymmetric amphiphile composition in the inner and outer leaflet of the bilayer which drives the spontaneous curvature. PMID:22594640

Shi, Dong; Sfintes, George; Laursen, Bo W; Simonsen, Jens B

2012-06-12

268

Spontaneous high-yield hydrogen production from cellulosic materials and water catalyzed by enzyme cocktail  

SciTech Connect

Carbon-neutral hydrogen gas is a compelling energy carrier, especially for the transportation section. Low-cost hydrogen can be produced from abundant renewable lignocellulosic biomass through a number of methods employing chemical catalysis, biocatalysis or a combination of both, but these technologies suffer from low hydrogen yields (well below the theoretical yield of 12 H2 per glucose), undesired side-products and/or required severe reaction conditions. Here we present a novel in vitro synthetic biology approach for producing near theoretical hydrogen yields from cellulosic materials (cellodextrins) and water at 32oC and 1 atm. These non-natural catabolic pathways containing up to 14 enzymes and one coenzyme degrade cellodextrins initially to glucose-1-phosphate and eventually to CO2, split water and finally release the chemical energy in the form of hydrogen gas. Up to 11.2 H2 per anhydroglucose was produced in a batch reaction. This spontaneous endothermic reaction is driven by entropy gain, suggesting that the thermal energy is adsorbed for generating more chemical energy (hydrogen gas) than that in cellodextrins, i.e., output/input of chemical energy > 1, with an input of ambient-temperature thermal energy.

Ye, Xinhao [Virginia Polytechnic Institute and State University (Virginia Tech); Wang, Yiran [Virginia Polytechnic Institute and State University (Virginia Tech); Hopkins, Robert C. [University of Georgia, Athens, GA; Adams, Michael W. W. [University of Georgia, Athens, GA; Evans, Barbara R [ORNL; Mielenz, Jonathan R [ORNL; Zhang, Y.-H. Percival [Virginia Polytechnic Institute and State University (Virginia Tech)

2009-01-01

269

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

SciTech Connect

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.

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

270

Determination of the meteoroid velocity distribution at the Earth using high-gain radar  

NASA Astrophysics Data System (ADS)

Plasma formed in the immediate vicinity of a meteoroid as it descends through Earth's atmosphere enables high-gain radars such as those found at Kwajalein, Arecibo, and Jicamarca to detect ablating meteoroids. In the work presented here, we show that these head echo measurements preferentially detect more energetic meteoroids over less energetic ones and present a method of estimating the effects of this bias when measuring the velocity distributions. To do this, we apply ablation and ionization models to estimate a meteoroid's plasma production rate based on its initial kinetic energy and ionization efficiency. This analysis demonstrates that, almost regardless of the assumptions made, high-gain radars will preferentially detect faster and more massive meteoroids. Following the model used by Taylor (1995, Icarus 116, 154-158), we estimate the biases and then apply them to observed meteoroid velocity distributions. We apply this technique to observations of the North Apex meteoroid source made by the Advanced Research Project Agency Long Range Tracking and Instrumentation Radar (ALTAIR) at two frequencies (160 and 422 MHz) and compare results from the Harvard Radio Meteor Project (HRMP) at High Frequency (HF, 40.9 MHz). Both studies observe a peak in the distribution of North Apex meteoroids at approximately 56 km s -1. After correcting for biases using Taylor's method, the results suggest that the mass-weighted peak of the distribution lies near 20 km s -1 for both studies. We attribute these similarities to the fact that both radar systems depend upon similar ablation and ionization processes and thus have a common mass scale.

Hunt, S. M.; Oppenheim, M.; Close, S.; Brown, P. G.; McKeen, F.; Minardi, M.

2004-03-01

271

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

NASA Astrophysics Data System (ADS)

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%).

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

272

Spontaneous and visually-driven high-frequency oscillations in the occipital cortex: Intracranial recording in epileptic patients  

PubMed Central

SUMMARY High-frequency oscillations (HFOs) at ?80 Hz of nonepileptic nature spontaneously emerge from human cerebral cortex. In 10 patients with extra-occipital lobe epilepsy, we compared the spectral-spatial characteristics of HFOs spontaneously arising from the nonepileptic occipital cortex with those of HFOs driven by a visual task as well as epileptogenic HFOs arising from the extra-occipital seizure focus. We identified spontaneous HFOs at ?80 Hz with a mean duration of 330 msec intermittently emerging from the occipital cortex during interictal slow-wave sleep. The spectral frequency band of spontaneous occipital HFOs was similar to that of visually-driven HFOs. Spontaneous occipital HFOs were spatially sparse and confined to smaller areas, whereas visually-driven HFOs involved the larger areas including the more rostral sites. Neither spectral frequency band nor amplitude of spontaneous occipital HFOs significantly differed from those of epileptogenic HFOs. Spontaneous occipital HFOs were strongly locked to the phase of delta activity, but the strength of delta-phase coupling decayed from 1 to 3 Hz. Conversely, epileptogenic extra-occipital HFOs were locked to the phase of delta activity about equally in the range from 1 to 3 Hz. The occipital cortex spontaneously generates physiological HFOs which may stand out on electrocorticography traces as prominently as pathological HFOs arising from elsewhere; this observation should be taken into consideration during presurgical evaluation. Coupling of spontaneous delta and HFOs may increase the understanding of significance of delta-oscillations during slow-wave sleep. Further studies are warranted to determine whether delta-phase coupling distinguishes physiological from pathological HFOs or simply differs across anatomical locations.

Nagasawa, Tetsuro; Juhasz, Csaba; Rothermel, Robert; Hoechstetter, Karsten; Sood, Sandeep; Asano, Eishi

2011-01-01

273

A Case of High Rate of Spontaneous Mutation Affecting Viability in DROSOPHILA MELANOGASTER  

PubMed Central

A spontaneous lethal mutation rate approximately twenty to thirty times greater than normal has been discovered in second and third chromosomes derived from an irradiated isogenic line and paired with marked inversion chromosomes. Mutations resulting in reductions of viability of varying magnitude short of complete lethality apparently also occur at a very high rate in the third but not in the second chromosome. The pattern of accumulation of lethal mutations over several generations and viability frequency distributions within generations have been studied in a number of independent experiments. High mutation rate occurs in heterozygous isogenic-derived second and third chromosomes, either together or apart, irrespective of the genetic constitution of nonhomologous chromosomes. High mutation rates were not observed using the same methods with chromosomes of an inbred line from a different source. The possible mechanisms responsible for these results are discussed.

Kidwell, Margaret Gale; Kidwell, J. F.; Nei, M.

1973-01-01

274

Filtering technique based on high-frequency plant modeling for high-gain control  

NASA Technical Reports Server (NTRS)

This invention was an improvement in aircraft control systems that utilized feedback motion sensors to generate a signal to control the aircraft. The improvement consisted essentially of a complementary filter comprising a simplified model of the aircraft, a high pass filter, a low pass filter and a summing amplifier. The control signal was applied to the simplified model of the aircraft which attempted to compute the vehicle response to the signal. This computed response was then fed into the high pass filter to eliminate long term errors in the calculated response, with the result that a good estimate of the high frequency content of the aircraft motion was obtained. In order to obtain a good estimate of the low frequency content of the motion, a rate gyro signal was fed through the low pass filter that eliminates all of the offending noise.

Niessen, F. R.; Garren, J. F., Jr. (inventors)

1979-01-01

275

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

SciTech Connect

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.

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

276

High Gain and Frequency Ultra-Stable Integrators for ICC and Long Pulse ITER Applications  

NASA Astrophysics Data System (ADS)

Eagle Harbor Technologies has developed a high gain and frequency ultra-stable integrator for small scale concept experiments and long pulse ITER applications. The Phase I integrator has a 10 ?s RC time with a frequency response greater than 10 MHz. The device has been operated for the 3600 s with a drift error less than 600 ?V, which exceeds the ITER specification. Longer period operation is also possible (> 30 hours). Additionally, this integrator has an extremely large dynamic range thereby increasing the effective bit depth of a digitizer. These integrators allow for both the fast and slow magnetic/plasma dynamics to be resolved with a single diagnostic. Data will be presented demonstrating the success of the Phase I program, and the Phase II work plan will be discussed. Work has begun to incorporate the integrators into legacy (CAMAC) and modern (National Instruments) DAQ systems.

Miller, Kenneth; Ziemba, Timothy; Prager, James

2012-10-01

277

Calibration of Gimbaled Platforms: The Solar Dynamics Observatory High Gain Antennas  

NASA Technical Reports Server (NTRS)

Simple parameterization of gimbaled platform pointing produces a complete set of 13 calibration parameters-9 misalignment angles, 2 scale factors and 2 biases. By modifying the parameter representation, redundancy can be eliminated and a minimum set of 9 independent parameters defined. These consist of 5 misalignment angles, 2 scale factors, and 2 biases. Of these, only 4 misalignment angles and 2 biases are significant for the Solar Dynamics Observatory (SDO) High Gain Antennas (HGAs). An algorithm to determine these parameters after launch has been developed and tested with simulated SDO data. The algorithm consists of a direct minimization of the root-sum-square of the differences between expected power and measured power. The results show that sufficient parameter accuracy can be attained even when time-dependent thermal distortions are present, if measurements from a pattern of intentional offset pointing positions is included.

Hashmall, Joseph A.

2006-01-01

278

Stimulated Brillouin scattering suppression through laser gain competition: scalability to high power.  

PubMed

We demonstrate stimulated Brillouin scattering (SBS) suppression in a Yb-doped fiber amplifier by seeding with a combination of broad- and single-frequency laser beams that are separated sufficiently to suppress four-wave mixing and to allow for efficient laser gain competition between the two signals. In the experiment, a monolithic fiber configuration was used. With appropriate selection of seed power ratio, we were able to generate single-frequency 1064 nm light with a slope efficiency of 78% while simultaneously suppressing the backscattered Stokes light. We discuss scalability to high power wherein a large thermal gradient can be induced at the output end of the fiber via quantum defect heating, leading to an SBS suppression factor comparable to counterpumping. PMID:20847796

Dajani, Iyad; Zeringue, Clint; Lu, Chunte; Vergien, Christopher; Henry, Leanne; Robin, Craig

2010-09-15

279

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

PubMed

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

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

2014-05-27

280

Nanogate - A Nanosecond Gated Image Intensifier with High Gain and High Resolution  

Microsoft Academic Search

The investigation of luminous phenomena with two-dimensional resolution in space and resolution in time requires electro-optical devices which can be gated for very short time intervals. Image intensifiers are presently mainly used for this purpose. They are available either as image intensifiers with microchannel plates or as image intensifier diodes. Due to secondary electron multiplication, microchannel plate intensifiers have high

W. Pfeiffer; D. Wittmer

1984-01-01

281

An Assessment of the High-gain Streckeisen STS2 Seismometer for Routine Earthquake Monitoring in the United States  

Microsoft Academic Search

USGS Open-File report: DRAFT Summary Objective. In this document we report the results of a study to determine if the Streckeisen STS2 high-gain seismometer is appropriate for use by the United States Geological Survey's (USGS) Advanced National Seismic System (ANSS) for routine earthquake monitoring in the United States (US). Issue. At issue is whether the high-gain STS2, with a sensitivity

D. E. McNamara; R. P. Buland; H. M. Benz

282

Natural Course of Spontaneous Pneumothorax without Bullae or Blebs under High-Resolution Computed Tomography.  

PubMed

Background The cause of primary spontaneous pneumothorax (PSP) is known as rupture of some bullae or blebs.Objective The aim of this study is to clarify the natural course of spontaneous pneumothorax in the absence of bullae or blebs under high-resolution chest computed tomography (HRCT).Patients and Method From January 2006 to December 2010, 854 patients with PSP were enrolled in the study group. All subjects received a chest CT scan and were reviewed retrospectively.Result There were 56 PSP cases (6.5%) without bullae or blebs under HRCT. Treatments included oxygen therapy in 16 (28.5%) cases, arrow catheter insertion in 22 (39.2%) cases, closed thoracostomy in 17 (30.3%) cases, and 1 (1.7%) case received a video-assisted thoracoscopic surgery (VATS) operation. There were nine recurrent cases (16%). Of the nine cases, eight cases were treated with VATS operation. Several bullae or blebs were found in five of those nine operated cases, and there were severe inflammatory fibrotic changes on the apex of one of the nine operated cases.Conclusion Several bullae and blebs were revealed upon operation of PSP without previously detected bullae and blebs on HRCT. We cautiously recommend operating on PSP regardless of whether bullae and blebs are detected by HRCT as long as there are no contraindications to the operation. PMID:23775414

Kim, Jung Tae; Oh, Tae Yoon; Chang, Woon Ha; Kong, Joon Hyuk; Baek, Kang Seok; Lee, Won Jin; Bang, Yun Yi

2013-06-17

283

Spontaneous bacterial peritonitis with a very high leukocyte count in ascitic fluid caused by Haemophilus influenzae  

PubMed Central

We report on a case of spontaneous bacterial peritonitis (SBP) due to Haemophilus influenzae (H. influenzae) in an elderly patient with alcoholic cirrhosis. The patient presented with a 5 day history of fever, cough, and fatigue. Abdominal paracentesis revealed a very high neutrophil count (134,800 cells/?L). Secondary peritonitis and abdominal abscess were ruled out. Peritoneal fluid culture displayed the growth of H. influenzae. The patient was treated with ceftriaxone and showed signs of improvement. Eventually, the patient died due to septic shock caused by other organisms. H. influenzae is a very rare cause of SBP. This case report demonstrates that (1) H. influenzae should be considered a potential cause of SBP, and (2) a very high leukocyte count in ascitic fluid can be found in patients with SBP.

Saadi, Tarek; Khoury, Safie; Veitsman, Ella; Baruch, Yaacov; Raz-Pasteur, Ayelet

2013-01-01

284

Spontaneous and Evoked High Frequency Oscillations in the Tetanus Toxin Model of Epilepsy  

PubMed Central

Summary Purpose High-frequency oscillations (HFOs) are an emerging biomarker for epileptic tissue. Yet the mechanism by which HFOs are produced is unknown, and their rarity makes them difficult to study. Our objective was to examine the occurrence of HFOs in relation to action potentials (APs) and the effect of microstimulation in the tetanus toxin (TT) model of epilepsy, a non-lesional model with a short latency to spontaneous seizures. Methods Rats were injected with TT into dorsal hippocampus and implanted with a 16 channel (8 × 2) multielectrode array, one row each in CA3 and CA1. After onset of spontaneous seizures (3-9 days), recordings were begun of APs and local field potentials, analyzed for the occurrence of interictal spikes and HFOs. Recordings were made during microstimulation of each electrode using customized, open-source software. Results Population bursts of APs during interictal spikes were phase-locked with HFOs, which were observable almost exclusively with high-amplitude interictal spikes. Further, HFOs could reliably be produced by microstimulation of the hippocampus, providing evidence that these oscillations can be controlled temporally by external means. Discussion We show for the first time the occurrence of HFOs in the TT epilepsy model, an attractive preparation for their experimental investigation and, importantly, one with a different etiology than status models, providing further evidence of the generality of HFOs. The ability to provoke HFOs with microstimulation may prove useful for better understanding HFOs by directly evoking them in the lab, and designing high-throughput techniques for pre-surgical localization of the epileptic focus.

Rolston, John D.; Laxpati, Nealen G.; Gutekunst, Claire-Anne; Potter, Steve M.; Gross, Robert E.

2010-01-01

285

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

NSDL National Science Digital Library

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 ñ 6.3 vs 58.1 ñ 8 kcal, p=0.02), but had no effect in fructose-fed rats (71.2 ñ 6.6 vs 72.4 ñ 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 ñ 2 g) compared with correspondingly fed leptin-responsive animals that were pre-treated with the fructose-free diet (30.4 ñ 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

Alexandra Shapiro (University of Florida Pharmacology and Therapeutics); Wei Mu (University of Florida Nephrology); Carlos Roncal (University of Florida Nephrology); Kit-Yan Cheng (University of Florida Pharmacology/Therapeutics); MD Richard J Johnson (University of Florida Division of Nephrology); Philip Scarpace (University of Florida Pharmacology and Therapeutics)

2008-08-16

286

Resistance and susceptibility to weight gain: Individual variability in response to a high-fat diet  

Microsoft Academic Search

An obesigenic environment is a potent force for promoting weight gain. However, not all people exposed to such an environment become obese; some remain lean. This means that some people are susceptible to weight gain (in a weight-promoting environment) and others are resistant. Identifying the characteristics of appetite control and food motivation in these two groups could throw light on

J. E. Blundell; R. J. Stubbs; C. Golding; F. Croden; R. Alam; S. Whybrow; J. Le Noury; C. L. Lawton

2005-01-01

287

Influence of some aminoacids on the spontaneous precipitation of calcium oxalate from high ionic strength solutions  

NASA Astrophysics Data System (ADS)

Kinetics of spontaneous batch precipitation of calcium oxalate from high ionic strength (0.3 mol dm-3) solutions, at pH = 6.50±0.05 and 298K, was followed by size distribution and thermogravimetric analysis, X-ray diffraction and optical microscopy. The effect of glutamic acid, ornithine or tryptophan on nucleation, crystal growth and aggregation was investigated in a wide range of concentrations, including that of physiological significance. The investigated aminoacids affected the nucleation of the solid phase. Their influence on growth and aggregation of crystals depended on the type and the concentration of aminoacid used. Results are interpreted in terms of critical time and supersaturation when crystal growth or aggregation commences, control mechanism of crystal growth and/or aggregation and the effect of aggregation on the rate of crystal growth.

Škrti?, Drago; Füredi-Milhofer, Helga

1993-04-01

288

Spontaneous ion-acoustic generation in a high power, multifilament ion source  

NASA Astrophysics Data System (ADS)

Under certain operating conditions, a high power, multifilament ion source can effectively function as a spontaneously excited ion-acoustic resonator. The fluctuations, initially excited by a current-driven instability at the thermionic source cathode, exhibit a Lorentzian spectral profile where the resonant frequency is solely determined by the spatial cathode configuration, and the resonance half-width is set by the mean plasma ion lifetime. The ion wave-cathode interaction, responsible for the resonant behavior, entails a feedback mechanism dependent on the electrostatic wave scattering properties of thermionic filaments operated under space-charge-limited conditions. Fluctuation amplitude levels are insufficient to significantly perturb the ions and consequently, the instability does not affect the performance of a multifilament source neutral beam system.

Schoenberg, K. F.; Kunkel, W. B.

1981-06-01

289

A high-gain EDFA design using double-pass amplification with a double-pass filter  

Microsoft Academic Search

An erbium-doped fiber (EDF) amplifier configured in a double-pass amplification scheme together with a midway bandpass filter is presented to provide a gain as high as 37.5 dB with a noise figure of less than 6 dB. The system provides a gain improvement of as much as 9.5 dB from the double-pass system without filter. The system also can easily

Belloui Bouzid; B. Mohd. Ali; M. K. Abdullah

2003-01-01

290

Virtual dielectric waveguide mode description of a high-gain free-electron laser. II. Modeling and numerical simulations  

Microsoft Academic Search

A high-gain free-electron laser is modeled using an expansion of the radiation field in terms of guided Laguerre-Gaussian modes of a virtual dielectric waveguide [E. Hemsing, A. Gover, and J. Rosenzweig, preceding paper, Phys Rev. A 77, 063830 (2008)]. The radiation profile evolution, power gain, and detuning efficiency characteristics are investigated for seeding with fundamental Gaussian and higher-order Laguerre-Gaussian input

Erik Hemsing; Avraham Gover; James Rosenzweig

2008-01-01

291

Extremely fast high-gain and low-current SOA by optical speed-up at transparency  

Microsoft Academic Search

We propose a new configuration for semiconductor optical amplifiers (SOAs), called optical speed-up at transparency (OSAT), which allows to speed up the gain recovery of SOAs and their saturation power without sacrificing the gain, nor increasing the applied current. The proposed configuration is particularly well-suited for high-speed WDM or OTDM applications. It consists of an optical CW-signal injected at the

M. A. Dupertuis; J. L. Pleumeekers; T. P. Hessler; P. E. Selbmann; B. Deveaud; B. Dagens; J. Y. Emery

2000-01-01

292

A novel 4H-SiC lateral bipolar junction transistor structure with high voltage and high current gain  

NASA Astrophysics Data System (ADS)

In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor (LBJT) with a base field plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 ?m and base doping of 3 × 1017 cm-3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 ?m. Besides, an investigation of a 4H-SiC vertical BJT (VBJT) with comparable breakdown voltage (3357 V) shows that the minimum base width of 0.25 ?m and base doping as high as 8 × 1017 cm-3 contribute to a maximum current gain of only 128.

Deng, Yong-Hui; Xie, Gang; Wang, Tao; Sheng, Kuang

2013-09-01

293

The high gain light water breeder reactor with a uranium-plutonium cycle  

SciTech Connect

In the design concept presented, two seed-blanket cores are utilized, a prebreeder and a breeder. The prebreeder core is fueled with plutonium obtained from standard LWR spent fuel and generates plutonium with a high isotopic content of /sup 240/Pu and /sup 241/Pu, which is used to fuel the breeder core. The initial fissile fuel for a 950-MW(electric) prebreeder is between 3000 and 4000 kg. Assuming the availability of rapid fuel reprocessing and refabrication, overall breeding of well over 10%/6 yr is feasible. The time between core refueling is >1 yr, rather than once every 3 months as required in the case of liquid-metal fast breeder reactors, so that the fuel inventories are substantially reduced for our system. Thermal-hydraulic analysis indicates that each of the two seed-blanket cores can fit into a standard pressurized water reactor pressure vessel and meet safety requirements. Major advantages of the concept are continued utilization of present LWR plants and strong negative void coefficients for the core. It is anticipated that at equilibrium conditions, when plutonium for the prebreeder and breeder cores is recycled into standard LWRs, there will be a further gain in breeding.

Radkowsky, A.; Shayer, Z.

1988-02-01

294

A MMI-based ultra-linear high-gain modulator and its performance analysis  

NASA Astrophysics Data System (ADS)

An electric optical modulator including a 1×2 multimode interference (MMI) coupler and an integrated Mach-Zehnder Interferometer (MZI) modulator that consists of a microring and a Phase Modulator (PM) is suggested in this paper. Such a modulator can achieve large output RF gain and high linearity performance at the same time. Moreover, due to the application of MMI coupler, traditional direct current (DC) bias circuits can be omitted and the modulator's deterioration caused by the phase error can be decreased a lot, which leads to reduced device complexity and increased device stability. The presented numerical and simulation results confirm the advantages of the newly proposed modulator over conventional modulators (MZI, RAMZI and IMPACC). Further analysis manifests that the proposed modulator has good tolerance in two aspects. Firstly, the modulator has an inherent ability to mitigate the detrimental effects of microring waveguide loss on slope efficiency and linearity by simply adjusting the external RF power split ratio. Secondly, the application of the MMI device increases the modulator's tolerance for the phase deviation caused by some environmental factors.

Yue, P.; Mao, B. M.; Yi, X.; Li, Q. N.; Liu, Z. J.

2013-12-01

295

A Modified Lunar Reconnaissance Orbiter (LRO) High Gain Antenna (HGA) Controller Based on Flight Performance  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration's (NASA) Lunar Reconnaissance Orbiter (LRO) was launched on June 18, 2009 and is currently in a 50 km mean altitude polar orbit around the Moon. LRO was designed and built by the NASA Goddard Space Flight Center in Greenbelt, MD. The spacecraft is three-axis stabilized via the attitude control system (ACS), which is composed of various control modes using different sets of sensors and actuators. In addition to pointing the spacecraft, the ACS is responsible for pointing LRO s two appendages, the Solar Array (SA) and the High Gain Antenna (HGA). This study reviews LRO s HGA control system. Starting with an overview of the HGA system, the paper delves into the single input single output (SISO) linear analysis followed by the controller design. Based on flight results, an alternate control scheme is devised to address inherent features in the flight control system. The modified control scheme couples the HGA loop with the spacecraft pointing control loop, and through analysis is shown to be stable and improve transient performance. Although proposed, the LRO project decided against implementing this modification.

Shah, Neerav

2010-01-01

296

Spontaneous growth of diamond from MnNi solvent-catalyst using opposed anvil-type high-pressure apparatus  

NASA Astrophysics Data System (ADS)

In this paper an overview of the application of opposed anvil-type high-pressure and high-temperature apparatus for spontaneous growth of diamond crystals by solvent-catalyst technique is presented. The process makes use of a molten Mn47Ni53 catalyst to initiate the graphite-diamond transformation reaction. The pressure and temperature requirements to obtain reproducible spontaneous diamond crystallization were around 52.5-54 kbar and 1270-1320 °C. The crystals had well-shaped cubo-structured morphology with the {100} and {111} faces and grain sizes of 0.2-0.5 mm. This work can stimulate future experimental exploration of spontaneous diamond crystallization by using other solvent-catalyst metals.

Zhigadlo, N. D.

2014-06-01

297

Progress towards a high-gain and robust target design for heavy ion fusion  

SciTech Connect

Recently [E. Henestroza et al., Phys. Plasmas 18, 032702 (2011)], a new inertial-fusion target configuration, the X-target, using one-sided axial illumination has been explored. This class of target uses annular and solid-profile heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an 'X.' X-targets using all-DT-filled metal cases imploded by three annular ion beams resulted in fuel densities of {approx}50 g/cm{sup 3} at peak compression, and fusion gains of {approx}50, comparable to heavy ion driven hohlraum targets [D. A. Callahan-Miller and M. Tabak, Phys. Plasmas 7, 2083 (2000)]. This paper discusses updated X-target configurations that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT fuel. The updated configurations are capable of assembling higher fuel areal densities {approx}2 g/cm{sup 2} using two annular beams to implode the target to peak DT densities {approx}100 g/cm{sup 3}, followed by a fast-ignition solid ion beam which heats the high-density fuel to thermonuclear temperatures in {approx}200 ps to start the burn propagation, obtaining gains of {approx}300. These targets have been modeled using the radiation-hydrodynamics code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] in two- and three- dimensions to study the properties of the implosion as well as the ignition and burn propagation phases. At typical Eulerian mesh resolutions of a few microns, the aluminum-DT interface shows negligible Rayleigh-Taylor (RT) and Richtmyer-Meshkov instability growth; also, the shear flow of the DT fuel as it slides along the metal X-target walls, which drives the RT and Kelvin Helmholtz instabilities, does not have a major effect on the burning rate. An analytic estimate of the RT instability process at the Al-DT interface shows that the aluminum spikes generated during the pusher deceleration phase would not reach the ignition zone in time to affect the burning process. Also, preliminary HYDRA calculations, using a higher resolution mesh to study the shear flow of the DT fuel along the X-target walls, indicate that metal-mixed fuel produced near the walls would not be transferred to the DT ignition zone (at maximum {rho}R) located at the vertex of the X-target.

Henestroza, Enrique; Grant Logan, B. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2012-07-15

298

Progress towards a high-gain and robust target design for heavy ion fusion  

NASA Astrophysics Data System (ADS)

Recently [E. Henestroza et al., Phys. Plasmas 18, 032702 (2011)], a new inertial-fusion target configuration, the X-target, using one-sided axial illumination has been explored. This class of target uses annular and solid-profile heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an ``X.'' X-targets using all-DT-filled metal cases imploded by three annular ion beams resulted in fuel densities of ~50 g/cm3 at peak compression, and fusion gains of ~50, comparable to heavy ion driven hohlraum targets [D. A. Callahan-Miller and M. Tabak, Phys. Plasmas 7, 2083 (2000)]. This paper discusses updated X-target configurations that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT fuel. The updated configurations are capable of assembling higher fuel areal densities ~2 g/cm2 using two annular beams to implode the target to peak DT densities ~100 g/cm3, followed by a fast-ignition solid ion beam which heats the high-density fuel to thermonuclear temperatures in ~200 ps to start the burn propagation, obtaining gains of ~300. These targets have been modeled using the radiation-hydrodynamics code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] in two- and three- dimensions to study the properties of the implosion as well as the ignition and burn propagation phases. At typical Eulerian mesh resolutions of a few microns, the aluminum-DT interface shows negligible Rayleigh-Taylor (RT) and Richtmyer-Meshkov instability growth; also, the shear flow of the DT fuel as it slides along the metal X-target walls, which drives the RT and Kelvin Helmholtz instabilities, does not have a major effect on the burning rate. An analytic estimate of the RT instability process at the Al-DT interface shows that the aluminum spikes generated during the pusher deceleration phase would not reach the ignition zone in time to affect the burning process. Also, preliminary HYDRA calculations, using a higher resolution mesh to study the shear flow of the DT fuel along the X-target walls, indicate that metal-mixed fuel produced near the walls would not be transferred to the DT ignition zone (at maximum ?R) located at the vertex of the X-target.

Henestroza, Enrique; Grant Logan, B.

2012-07-01

299

High Extraction Efficiency of Spontaneous Emission from Slabs of Photonic Crystals  

Microsoft Academic Search

A thin slab of two-dimensional photonic crystal is shown to alter drastically the radiation pattern of spontaneous emission. More specifically, by eliminating all guided modes at the transition frequencies, spontaneous emission can be coupled entirely to free space modes, resulting in a greatly enhanced extraction efficiency. Such structures might provide a solution to the long-standing problem of poor light extraction

Shanhui Fan; Pierre R. Villeneuve; J. D. Joannopoulos; E. F. Schubert

1997-01-01

300

High-gain AlGaAs/GaAs double heterojunction Darlington phototransistors for optical neural networks  

NASA Technical Reports Server (NTRS)

High-gain MOCVD-grown (metal-organic chemical vapor deposition) AlGaAs/GaAs/AlGaAs n-p-n double heterojunction bipolar transistors (DHBTs) and Darlington phototransistor pairs are provided for use in optical neural networks and other optoelectronic integrated circuit applications. The reduced base doping level used results in effective blockage of Zn out-diffusion, enabling a current gain of 500, higher than most previously reported values for Zn-diffused-base DHBTs. Darlington phototransitor pairs of this material can achieve a current gain of over 6000, which satisfies the gain requirement for optical neural network designs, which advantageously may employ neurons comprising the Darlington phototransistor pairs in series with a light source.

Kim, Jae H. (inventor); Lin, Steven H. (inventor)

1991-01-01

301

Design and performance of an Automatic Gain Control system for the High Energy X-Ray Timing Experiment  

NASA Technical Reports Server (NTRS)

The High Energy X-Ray Timing Experiment (HEXTE), currently under development for the X-Ray Timing Explorer (XTE) mission, employs a closed loop gain control system to attain 0.5 percent stabilization of each of eight-phoswich detector gains. This Automatic Gain Control (AGC) system utilizes a split window discriminator scheme to control the response of each detector pulse height analyzer to gated Am-241 X-ray events at 60 keV. A prototype AGC system has been implemented and tested within the gain perturbation environment expected to be experienced by the HEXTE instrument in flight. The AGC system and test configuration are described. Response, stability and noise characteristics are measured and compared with theoretical predictions. The system is found to be generally suitable for the HEXTE application.

Pelling, Michael R.; Rothschild, Richard E.; Macdonald, Daniel R.; Hertel, Robert; Nishiie, Edward

1991-01-01

302

High spatial resolution BOTDA using simultaneously launched gain and loss pump pulses  

NASA Astrophysics Data System (ADS)

We report a 10cm spatial resolution in a Brillouin-based distributed sensing system using two simultaneously launched gain and loss pump pulses, having slightly different durations. Post-recording subtraction of the probe signal, excited by the shorter pulse, from the corresponding one, obtained from the longer pump pulse, is no longer required, since it is done automatically by the overlapping parts of the gain and loss pump pulses. Using a 30ns gain pump pulse and a 29ns loss pump pulse we were able to improve upon previously published results, achieving a distributed strain measurement along a standard single mode optical fiber with a spatial resolution of ~10cm. This technique does not broaden the involved Brillouin gain spectra so that the strain/temperature sensitivity is not compromised.

Motil, A.; Danon, O.; Peled, Y.; Tur, M.

2013-05-01

303

High-gain 150-215GHz MMIC amplifier with integral waveguide transitions  

Microsoft Academic Search

The design and measured results of a six-stage InP monolithic microwave integrated circuit (MMIC) amplifier with 20±6 dB gain from 150 to 215 GHz is reported. The MMIC has integral probes for direct coupling to 140-220 GHz WR5 waveguide without bond wires or external transitions. This is the first amplifier operating above 140 GHz with sufficient gain to be useful

S. Weinreb; T. Gaier; M. Barsky; Y. C. Leong; L. Samoska

1999-01-01

304

Ultra-high current gain InGaAsP/InP heterojunction bipolar transistor  

NASA Astrophysics Data System (ADS)

A maximum dc current gain of 112,000 was obtained by a double-layer base HBT with a thin base layer of 0.1 micron thickness. A breakdown voltage with a common-emitter configuration was found to be 1.3 V, which is smaller than for conventional HPTs owing to the ultrahigh current gain and a carrier multiplication at a base-collector junction.

Ohishi, T.; Abe, Y.; Sugimoto, H.; Ohtsuka, K.; Matsui, T.

1990-03-01

305

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

PubMed

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

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

306

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

NASA Technical Reports Server (NTRS)

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.

Bourkland, Kristin L.; Liu, Kuo-Chia

2011-01-01

307

High-Gain Wide-Band Gyrotron Traveling Wave Amplifier with a Helically Corrugated Waveguide  

NASA Astrophysics Data System (ADS)

First bandwidth measurements of a novel gyrotron amplifier are presented. The coupling between the second harmonic cyclotron mode of a gyrating electron beam and the radiation field occurred in the region of near infinite phase velocity over a broad bandwidth by using a cylindrical waveguide with a helical corrugation on its internal surface. With a beam energy of 185 keV, the amplifier achieved a maximum output power of 1.1 MW, saturated gain of 37 dB, linear gain of 47 dB, saturated bandwidth of 8.4 to 10.4 GHz ( 21% relative bandwidth), and an efficiency of 29%, in good agreement with theory.

Bratman, V. L.; Cross, A. W.; Denisov, G. G.; He, W.; Phelps, A. D. R.; Ronald, K.; Samsonov, S. V.; Whyte, C. G.; Young, A. R.

2000-03-01

308

Gain saturation in InGaN superluminescent diodes  

NASA Astrophysics Data System (ADS)

The gain saturation is a crucial factor limiting achievable output power of superluminescent diodes (SLD), as it exponentially depends on optical gain value. Contrary to laser diodes, in SLDs gain is increasing with the increasing current even much above the transparency conditions. Therefore, SLDs provide us with an unique possibility to examine gain under high current densities (high carrier injection). In our work we examined SLDs fabricated in a "j-shape" ridge-waveguide geometry having chips of the length of 700 ?m and 1000 ?m, emitting in the blue-violet region. By comparing the amplified spontaneous emission measured along the device waveguide with true spontaneous emission measured in perpendicular direction, we are able to extract optical gain as a function of injected current. We show, that in our devices spontaneous emission exhibits a square-root-like dependence on current which is commonly associated with the presence of "droop" in case of nitride light emitting diodes. However, along the waveguide axis, fast processes of stimulated recombination dominate which eliminates the efficiency reduction. Calculated optical gain shows a substantial saturation for current densities above 8 kA/cm2.

Kafar, Anna; Stanczyk, Szymon; Targowski, Grzegorz; Suski, Tadek; Perlin, Piotr

2014-03-01

309

High mobility polymer based on a ?-extended benzodithiophene and its application for fast switching transistor and high gain photoconductor.  

PubMed

Here we present synthesis and electronic properties of a new alternating copolymer composed of dithieno[2,3-d;2',3'-d']benzo[1,2-b;4,5-b']dithiophene (DTBDT) and diketopyrrolopyrrole units, poly dithienobenzodithiophene-co-diketopyrrolopyrrolebithiophene (PDPDBD). The resulting polymer showed hysteresis free, fast switching and highly reliable organic thin-film transistor properties comparable to a-Si. Hole mobility of the polymer is about 2.7?cm(2)V(-1)s(-1), which is remarkably improved compared with its benzodithiophene (BDT)-analougue that contains a smaller aromatic ring of BDT in the place of DTBDT. This is mainly due to much increased intramolecular charge transport originated from PDPDBD's rigid molecular backbone. Furthermore, photoconductor devices fabricated by using PDPDBD as an active layer showed a high performance with the highest photoconductive gain of ~10(5). Taken together, the successful PDPDBD's transistor and photoconductor performances with high device stability demonstrated practical applicability of PDPDBD in low-cost and flexible optoelectronic devices. PMID:24970637

Park, Sungmin; Lim, Byung Tack; Kim, BongSoo; Son, Hae Jung; Chung, Dae Sung

2014-01-01

310

High mobility polymer based on a ?-extended benzodithiophene and its application for fast switching transistor and high gain photoconductor  

PubMed Central

Here we present synthesis and electronic properties of a new alternating copolymer composed of dithieno[2,3-d;2?,3?-d?]benzo[1,2-b;4,5-b?]dithiophene (DTBDT) and diketopyrrolopyrrole units, poly dithienobenzodithiophene-co-diketopyrrolopyrrolebithiophene (PDPDBD). The resulting polymer showed hysteresis free, fast switching and highly reliable organic thin-film transistor properties comparable to a-Si. Hole mobility of the polymer is about 2.7?cm2V?1s?1, which is remarkably improved compared with its benzodithiophene (BDT)-analougue that contains a smaller aromatic ring of BDT in the place of DTBDT. This is mainly due to much increased intramolecular charge transport originated from PDPDBD's rigid molecular backbone. Furthermore, photoconductor devices fabricated by using PDPDBD as an active layer showed a high performance with the highest photoconductive gain of ~105. Taken together, the successful PDPDBD's transistor and photoconductor performances with high device stability demonstrated practical applicability of PDPDBD in low-cost and flexible optoelectronic devices.

Park, Sungmin; Lim, Byung Tack; Kim, BongSoo; Son, Hae Jung; Chung, Dae Sung

2014-01-01

311

Light-controlled resistors provide quadrature signal rejection for high-gain servo systems  

NASA Technical Reports Server (NTRS)

Servo amplifier feedback system, in which the phase sensitive detection, low pass filtering, and multiplication functions required for quadrature rejection, are preformed by light-controlled photoresistors, eliminates complex circuitry. System increases gain, improves signal-to-noise ratio, and eliminates the necessity for compensation.

Mc Cauley, D. D.

1967-01-01

312

High Gain, Fast Scan, Broad Spectrum, Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM  

Microsoft Academic Search

Parallax Research, Inc. proposes to produce a new type of x-ray spectrometer for use with Scanning Electron Microscopy (SEM) that would have the energy resolution of WDS and the ease of use of EDS with sufficient gain for lower energies that it can be used at low beam currents as is EDS. Parallax proposes to do this by development of

David OHara; Eric Lochmer

2003-01-01

313

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

Microsoft Academic Search

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

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

1987-01-01

314

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

Microsoft Academic Search

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%.

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

1984-01-01

315

High power LED pulser for gain monitoring in a multicounter experiment  

NASA Astrophysics Data System (ADS)

A powerful source of light pulses, based on GL56 LEDs is described. It is used for monitoring the gain stability of scintillation counters. The shape of the light pulse is similar to the response of the plastic scintillator to particles. The source stability is checked with a PIN photodiode. A preamplifier for this diode is presented.

Zabierowski, Janusz

1994-01-01

316

Differences in Personality Characteristics between Groups Having High and Low Mathematical Achievement Gain under Individualized Instruction.  

ERIC Educational Resources Information Center

The problem of this study was to determine the relationship of selected characteristics of pupils to achievement gain in elementary school mathematics classes using the Individualized Mathematics Curriculum Project (IMCP) approach. Analysis o f data was based primarily on pre-achievement and post-achievement scores. The hypothesis that there was…

Neufeld, K. Allen

317

HIGH-GAIN APERTURE-COUPLED DIELECTRIC-RESONATOR ANTENNA WITH SURFACE MOUNTED HORN  

Microsoft Academic Search

In this presentation we propose a novel gain enhancement technique of the DRA by using a surface mount quasi-planar horn. The geometry of the proposed antenna is shown in Figure 1. In the proposed structure, the aperture coupled DRA works as a feed to the surface mounted horn antenna. Note that the rectangular DRA is located over the centre of

Esselle Karu

318

High frequency, spontaneous motA mutations in Campylobacter jejuni strain 81-176.  

PubMed

Campylobacter jejuni is an important cause of bacterial diarrhea worldwide. The pathogenesis of C. jejuni is poorly understood and complicated by phase variation of multiple surface structures including lipooligosaccharide, capsule, and flagellum. When C. jejuni strain 81-176 was plated on blood agar for single colonies, the presence of translucent, non-motile colonial variants was noted among the majority of opaque, motile colonies. High-throughput genomic sequencing of two flagellated translucent and two opaque variants as well as the parent strain revealed multiple genetic changes compared to the published genome. However, the only mutated open reading frame common between the two translucent variants and absent from the opaque variants and the parent was motA, encoding a flagellar motor protein. A total of 18 spontaneous motA mutations were found that mapped to four distinct sites in the gene, with only one class of mutation present in a phase variable region. This study exemplifies the mutative/adaptive properties of C. jejuni and demonstrates additional variability in C. jejuni beyond phase variation. PMID:24558375

Mohawk, Krystle L; Poly, Frédéric; Sahl, Jason W; Rasko, David A; Guerry, Patricia

2014-01-01

319

Development of a High Gain Observer for In-Line Monitoring of Sublimation in Vial Freeze Drying  

Microsoft Academic Search

In-line monitoring of the primary drying of the lyophilization process of a pharmaceutical product in vials is addressed in this article. A soft sensor (observer) based on the high gain concept is designed to this purpose. The proposed observer combines the physical measure of the frozen product temperature at the bottom of the vial with a simplified mathematical model of

Salvatore A. Velardi; Hassan Hammouri; Antonello A. Barresi

2010-01-01

320

Novel Parameter Identification by Using a High-Gain Observer With Application to a Gas Turbine Engine  

Microsoft Academic Search

In this study, a novel identification technique, that is high-gain observer-based identification approach, is proposed for systems with bounded process and measurement noises. For system parameters with abnormal changes, an adaptive change detection and parameter identification algorithm is next presented. The presented technique and algorithm are finally applied to the parameter identification of the gas turbine engine by using the

Zhiwei Gao; Xuewu Dai; Tim Breikin; Hong Wang

2008-01-01

321

Modeling and output tracking of transverse flux permanent magnet machines using high gain observer and RBF Neural network  

Microsoft Academic Search

This paper deals with modeling and adaptive output tracking of a transverse flux permanent magnet machine as a nonlinear system with unknown nonlinearities by utilizing high gain observer and radial basis function networks. The proposed model is developed based on computing the permeance between rotor and stator using quasiflux tubes. Based on this model, the techniques of feedback linearization and

H. R. Karimi; A. Babazadeh

2005-01-01

322

A note on the robustness of high-gain-observer-based controllers to unmodeled actuator and sensor dynamics  

Microsoft Academic Search

It is shown that a nonlinear output feedback stabilizing controller, which combines a globally bounded state feedback controller with a high-gain observer, is robust with respect to unmodeled fast actuator and sensor dynamics. The actuator and sensor dynamics need to be sufficiently fast relative to the dynamics of the nominal closed-loop system under state feedback, but they need not be

Hassan K. Khalil

2005-01-01

323

Design and Analysis of a High-Gain Observer for the Operation of SPM Machines Under Saturation  

Microsoft Academic Search

This paper presents a high-gain observer of the rotor position for the control of surface permanent magnet synchronous machines under loaded conditions, e.g., saturation. Determining the rotor flux position of permanent magnet AC machines under no load is simpler, since its flux and rotor position coincide. How- ever under load and in the presence of saturation in particular, the flux

Sinisa Jurkovic; Elias G. Strangas

2011-01-01

324

Design of cascading two stages of high gain harmonic generation scheme based on Shanghai deep ultraviolet free electron laser  

Microsoft Academic Search

Cascading stages of high gain harmonic generation free electron laser (FEL) seem to be a feasible way to generate short wavelength radiation. With help of the analytical estimates, we design a two-stage cascading scheme to achieve 131 nm DUV radiation on the basis of the Shanghai deep ultraviolet free electron laser test facility. Detailed studies on the FEL performance, the

Hai-Xiao Deng; Zhi-Min Dai

2008-01-01

325

Simple Indirect Adaptive Control Without a Diophantine Equation and Without The Sign of The High Frequency Gain  

Microsoft Academic Search

The adaptive control of general delay, linear time-varying systems is addressed. We devise a new model reference adaptive control law which does not require the solution of a Diophantine equation, and does not require a priori knowledge of the sign of the high frequency gain. This control law coupled with the parameter estimation equations allows a simple representation of the

Sean P. Meyn; Lyndon J. Brown

1992-01-01

326

High-gain wavelength-selective amplification and cavity ring down spectroscopy in a fluoride glass erbium-doped microsphere.  

PubMed

We experimentally demonstrate a compact optical amplifier consisting of a rare-earth-doped whispering-gallery-mode microsphere coupled via a tapered fiber. A gain up to 20 dB is reported in an erbium-doped fluoride glass microsphere 135 ?m in diameter. Below the amplification regime, the optical gain is used to compensate for unavoidable losses due to surface contamination or scattering. Quality factor as high as 2×10(9) has been measured by analyzing the transient response of the microsphere excited by a dynamically shifted frequency input signal. PMID:23164896

Rasoloniaina, A; Trebaol, S; Huet, V; Le Cren, E; Nunzi Conti, G; Serier-Brault, H; Mortier, M; Dumeige, Y; Féron, P

2012-11-15

327

Raman gain from waveguides inscribed in KGd(WO4)2 by high repetition rate femtosecond laser  

NASA Astrophysics Data System (ADS)

We report the formation of waveguides in Raman-active KGd(WO4)2 with a focused, high repetition rate femtosecond laser. Parallel guiding regions, formed to either side of the laser-induced damage track, supported TE and TM modes that coupled efficiently to optical fiber at telecom wavelengths. Micro-Raman spectroscopy of the guiding regions revealed the preservation of the characteristic 768 and 901 cm-1 Raman mode intensities. Raman gain with 6% efficiency was demonstrated for the 768 cm-1 Raman line by pumping the waveguide with an infrared 80 ps source, the first time Raman gain has been reported in laser formed waveguides.

Eaton, S. M.; Merchant, C. A.; Iyer, R.; Zilkie, A. J.; Helmy, A. S.; Aitchison, J. S.; Herman, P. R.; Kraemer, D.; Miller, R. J. D.; Hnatovsky, C.; Taylor, R. S.

2008-02-01

328

Wideband and flat-gain amplifier based on high concentration erbium-doped fibres in parallel double-pass configuration  

SciTech Connect

A wideband and flat gain erbium-doped fibre amplifier (EDFA) is demonstrated using a hybrid gain medium of a zirconiabased erbium-doped fibre (Zr-EDF) and a high concentration erbium-doped fibre (EDF). The amplifier has two stages comprising a 2-m-long ZEDF and 9-m-long EDF optimised for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fibre Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achieved with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.

Hamida, B A; Cheng, X S; Harun, S W; Naji, A W; Arof, H; Al-Khateeb, W; Khan, S; Ahmad, H

2012-03-31

329

Wideband and flat-gain amplifier based on high concentration erbium-doped fibres in parallel double-pass configuration  

NASA Astrophysics Data System (ADS)

A wideband and flat gain erbium-doped fibre amplifier (EDFA) is demonstrated using a hybrid gain medium of a zirconiabased erbium-doped fibre (Zr-EDF) and a high concentration erbium-doped fibre (EDF). The amplifier has two stages comprising a 2-m-long ZEDF and 9-m-long EDF optimised for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fibre Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achieved with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.

Hamida, B. A.; Cheng, X. S.; Harun, S. W.; Naji, A. W.; Arof, H.; Al-Khateeb, W.; Khan, S.; Ahmad, H.

2012-03-01

330

Prediction of the mass gain during high temperature oxidation of aluminized nanostructured nickel using adaptive neuro-fuzzy inference system  

NASA Astrophysics Data System (ADS)

In this paper, the applicability of ANFIS as an accurate model for the prediction of the mass gain during high temperature oxidation using experimental data obtained for aluminized nanostructured (NS) nickel is presented. For developing the model, exposure time and temperature are taken as input and the mass gain as output. A hybrid learning algorithm consists of back-propagation and least-squares estimation is used for training the network. We have compared the proposed ANFIS model with experimental data. The predicted data are found to be in good agreement with the experimental data with mean relative error less than 1.1%. Therefore, we can use ANFIS model to predict the performances of thermal systems in engineering applications, such as modeling the mass gain for NS materials.

Hayati, M.; Rashidi, A. M.; Rezaei, A.

2012-10-01

331

Compact tunable high power picosecond source based on Yb-doped fiber amplification of gain switch laser diode.  

PubMed

A compact tunable high power picosecond source based on Yb-doped fiber amplification of gain switch laser diode is demonstrated. A multi-stage single mode Yb-doped fiber preamplifier was combined with a single mode double-clad Yb-doped fiber main amplifier to construct the amplification system, which is seeded by a gain switch laser diode. By optimizing preamplifier???s parameters to compensate the seed spectrum gain, a "flat top" broadband spectrum is obtained to realize wavelength tunable output with a self-made tunable filter. The tunable pulses were further amplified to 3.5 W average power 90 ps pulses at 1 MHz repetition rate, and the center wavelength was tunable in the ranges from 1053 nm to 1073 nm with excellent beam quality. PMID:18545499

Liu, Hongjun; Gao, Cunxiao; Tao, Jintao; Zhao, Wei; Wang, Yishan

2008-05-26

332

Gain mechanism of the vertical-cavity surface-emitting semiconductor laser  

SciTech Connect

The vertical-cavity surface-emitting single quantum well laser is examined in terms of the short Fabry--Perot cavity's effect on optical gain. It is suggested that for this vertical- cavity structure the optical gain mechanism is fundamentally altered as compared to the case of the more standard edge-emitting device with longer cavity lengths. The short cavity and highly reflecting mirrors of the vertical cavity structure lead to an enhanced gain coefficient at fixed carrier densities, due to enhanced spontaneous emission into the Fabry--Perot modes of the optical cavity, and the resultantly reduced spontaneous linewidth.

Deppe, D.G. (Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712-1084 (USA))

1990-10-22

333

Numerical analysis of the mode competition in high-gain unstable resonators using the exact cavity equations of motion with dynamic gain  

NASA Astrophysics Data System (ADS)

The dynamic coupled modes (DCM) method has been applied to study the transverse mode competition in optical resonators. In this work a differential equation for the homogeneously saturating dynamic gain is included in the original dynamic coupled modes method, thus increasing its physical resemblance and allowing the retrieval of gain temporal evolution at every point within the lasing medium. This new model provides a realistic temporal evolution of the mode competition and gain saturation within the resonator, which can give further information of spatial coherence properties. The temporal information becomes particularly valuable when the laser transient is a matter of interest or when a continuous wave steady output is never reached, as occurs in pulsed lasers. Additionally, transverse spatial hole burning and inhomogeneous line broadening is straightforwardly included in the gain model. The application of the method to a typical CO2 unstable confocal resonator is fully described, results and their connection to relevant physical properties of gas lasers, such as spiking and relaxation oscillations are discussed. Results of the numerical implementation of the DCM method with dynamic gain are in very good agreement with experimental measurements reported previously.

Guizar-Sicairos, Manuel; Gutierrez-Vega, Julio C.

2005-01-01

334

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

NASA Technical Reports Server (NTRS)

The Solar Dynamics Observatory (SDO) is a NASA spacecraft designed to study the Sun. It was launched on February 11, 2010 into a geosynchronous orbit, and uses a suite of attitude sensors and actuators to finely point the spacecraft at the Sun. SDO has three science instruments: the Atmospheric Imaging Assembly (AIA), the Helioseismic and Magnetic Imager (HMI), and the Extreme Ultraviolet Variability Experiment (EVE). SDO uses two High Gain Antennas (HGAs) to send science data to a dedicated ground station in White Sands, New Mexico. In order to meet the science data capture budget, the HGAs must be able to transmit data to the ground for a very large percentage of the time. Each HGA is a dual-axis antenna driven by stepper motors. Both antennas transmit data at all times, but only a single antenna is required in order to meet the transmission rate requirement. For portions of the year, one antenna or the other has an unobstructed view of the White Sands ground station. During other periods, however, the view from both antennas to the Earth is blocked for different portions of the day. During these times of blockage, the two HGAs take turns pointing to White Sands, with the other antenna pointing out to space. The HGAs handover White Sands transmission responsibilities to the unblocked antenna. There are two handover seasons per year, each lasting about 72 days, where the antennas hand off control every twelve hours. The non-tracking antenna slews back to the ground station by following a ground commanded trajectory and arrives approximately 5 minutes before the formerly tracking antenna slews away to point out into space. The SDO Attitude Control System (ACS) runs at 5 Hz, and the HGA Gimbal Control Electronics (GCE) run at 200 Hz. There are 40 opportunities for the gimbals to step each ACS cycle, with a hardware limitation of no more than one step every three GCE cycles. The ACS calculates the desired gimbal motion for tracking the ground station or for slewing, and sends the command to the GCE at 5 Hz. This command contains the number of gimbals steps for that ACS cycle, the direction of motion, the spacing of the steps, and the delay before taking the first step. The AIA and HMI instruments are sensitive to spacecraft jitter. Pre-flight analysis showed that jitter from the motion of the HGAs was a cause of concern. Three jitter mitigation techniques were developed to overcome the effects of jitter from different sources. The first method is the random step delay, which avoids gimbal steps hitting a cadence on a jitter-critical mode by pseudo-randomly delaying the first gimbal step in an ACS cycle. The second method of jitter mitigation is stagger stepping, which forbids the two antennas from taking steps during the same ACS cycle in order to avoid constructively adding jitter from two antennas. The third method is the inclusion of an instrument No Step Request (NSR), which allows the instruments to request a stoppage in gimbal stepping during the times when they are taking images. During the commissioning phase of the mission, a jitter test was performed onboard the spacecraft. Various sources of jitter, such as the reaction wheels, the High Gain Antenna motors, and the motion of the instrument filter wheels, were examined to determine the level of their 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. These jitter levels are compared with the gimbal jitter allocations for each instrument. Additionally, the jitter test provided insight into a readback delay that exists with the GCE. Pre-flight analysis suggested that gimbal steps scheduled to occur during the later portion of an ACS cycle would not be read during that cycle, resulting in a delay in the telemetered current gimbal position. Flight data from the jitter test confirmed this expectation. Analysis is presentehat shows the readback delay does not have a negative impact on gimbal control. The decision was

Bourkland, Kristin L.; Liu, Kuo-Chia

2011-01-01

335

High-gain wide-band gyrotron traveling wave amplifier with a helically corrugated waveguide  

PubMed

First bandwidth measurements of a novel gyrotron amplifier are presented. The coupling between the second harmonic cyclotron mode of a gyrating electron beam and the radiation field occurred in the region of near infinite phase velocity over a broad bandwidth by using a cylindrical waveguide with a helical corrugation on its internal surface. With a beam energy of 185 keV, the amplifier achieved a maximum output power of 1.1 MW, saturated gain of 37 dB, linear gain of 47 dB, saturated bandwidth of 8.4 to 10.4 GHz ( 21% relative bandwidth), and an efficiency of 29%, in good agreement with theory. PMID:11017315

Bratman; Cross; Denisov; He; Phelps; Ronald; Samsonov; Whyte; Young

2000-03-20

336

Plasmonic Amplification with Ultra-High Optical Gain at Room Temperature  

PubMed Central

Nanoplasmonic devices are promising for next generation information and communication technologies because of their capability to confine light at subwavelength scale and transport signals with ultrahigh speeds. However, ohmic losses are inherent to all plasmonic devices so that further development of integrated plasmonics requires efficient in situ loss compensation of signals with a wavelength and polarization of choice. Here we show that CdSe nanobelt/Al2O3/Ag hybrid plasmonic waveguides allow for efficient broadband loss compensation of propagating hybrid plasmonic signals of different polarizations using an optical pump and probe technique. With an internal gain coefficient of 6755?cm?1 at ambient condition, almost 100% of the propagation loss of TM-dominant plasmonic signals is compensated. From comparison with a similar photonic structure we attribute the fast-increasing gain at low pump intensity in hybrid plasmonic waveguides to the transfer across the metal-oxide-semiconductor interface of ‘hot' electrons photogenerated by the pump light.

Liu, Ning; Wei, Hong; Li, Jing; Wang, Zhuoxian; Tian, Xiaorui; Pan, Anlian; Xu, Hongxing

2013-01-01

337

High gain micro-channel plate multipliers for particle tracking or single photo-electron counting  

SciTech Connect

Micro-channel plate multipliers have been used to detect the passage of relativistic charged particles. Measurements of the detection efficiency and pulse height response versus micro-channel plate gain are presented for one, two and three micro-channel plate arrays. Values describing temporal response and transit time jitter are also given. In a separate measurement, the response of a single micro-channel plate to individual slow electrons (less than or equal to 1 keV) was studied. By using a special technique output bunches as small as three electrons may be seen for low average micro-channel plate gain. The results of attempts to improve the micro-channel plate response are also presented.

Oba, K.; Rehak, P.; Smith, S.D.

1980-01-01

338

Polymer-nanocrystal hybrid photodetectors with planar heterojunctions designed strategically to yield a high photoconductive gain  

NASA Astrophysics Data System (ADS)

We demonstrate an approach to enhancing the photoresponsivity of a polymer photodetector (PPD). Both conventional bulk heterojunction (BHJ) and planar heterojunction (PHJ) PPDs were fabricated considering that the interface between a CdSe nanocrystal and a polymer can create photoconductive gain. A systematic study of the illumination wavelength and light power dependence of the photocurrent gain, combined with the charge carrier transport analysis, suggested that the PHJ-PPD could yield a higher hole mobility than could be achieved in a BHJ-PPD without compromising on the selective electron trapping effects. The optimized PHJ-PPD led to a photoconductive detectivity of 1.3 × 1010 cm Hz1/2/W.

Kyu An, Tae; Eon Park, Chan; Sung Chung, Dae

2013-05-01

339

An integrated Ku-band linearizer driver amplifier for TWTAs with high gain and wide bandwidth  

NASA Astrophysics Data System (ADS)

An integrated linearizer driver amplifier (LDA) has been developed for Ku-band traveling wave tube amplifier (TWTA) satellite applications. This LDA utilizes a passive FET linearizer that is small in size and weight and has a bandwidth greater than 1 GHz and low loss. An improvement of 10 dB in TWTA carrier-to-intermodulation ratio (C/I) at 3-dB output power backoff and a phase change of less than 5 degrees for drive levels up to 3 dB over saturation is provided. A gain of 40 dB (minimum), 32 steps of gain control, and 20 dB of overdrive protection is furnished. The integrated LDA consumes only 1.5 watts of dc power, and the LDA RF section weighs only 1.3 pounds.

Moochalla, Shabbir S.; Katz, Allen; Aubert, Donald E.; Ernandez, John; Pallas, George

1992-03-01

340

Modeling of short, single-frequency, fiber lasers in high-gain fiber  

Microsoft Academic Search

Grating gain must be accounted for when designing single-frequency fiber lasers which utilize intracore, erbium-doped, Bragg reflectors for cavity feedback, and mode selectivity. A closed-form solution, derived through coupled mode theory for the spectral reflectivity of an intracore Bragg phase grating in an amplifying fiber is derived and applied to the design of single-mode fiber lasers. Both analytical and experimental

G. A. Ball; W. H. Glenn; W. W. Morey; P. K. Cheo

1993-01-01

341

A concept for a high gain light water breeder on the uranium\\/plutonium cycle  

Microsoft Academic Search

Contrary to the prevailing view, breeding in a light water reactor on the uranium\\/plutonium cycle can be achieved if one takes advantage of the potential neutronic gains from the buildup and depletion of higher isotopes formed from neutron absorption in ²³⁹Pu. To accomplish this, a combination of Prebreeder and Breeder cycles is proposed. The concept employs a novel core loading

A. Radkowsky; A. G. Adamantiades; Z. Sheider

1984-01-01

342

CMOS low-distortion high-frequency variable-gain amplifier  

Microsoft Academic Search

The overall system performance of mixed-signal CMOS IC's is largely determined by the dynamic performance of the analog front-ends. System features are, in contrast, mainly set by the digital architecture. In order to optimize the dynamic range of the system and to minimize the sensitivity to substrate noise, the analog-to-digital converter (ADC) has to be preceded by a variable-gain amplifier

J. J. F. Rijns

1996-01-01

343

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

Microsoft Academic Search

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

David R. Jackson; Arthur A. Oliner

1988-01-01

344

High Gain, Fast Scan, Broad Spectrum, Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM  

SciTech Connect

Parallax Research, Inc. proposes to produce a new type of x-ray spectrometer for use with Scanning Electron Microscopy (SEM) that would have the energy resolution of WDS and the ease of use of EDS with sufficient gain for lower energies that it can be used at low beam currents as is EDS. Parallax proposes to do this by development of new multiple reflection x-ray collimation optics, new diffractor technology, new detector technology and new scan algorithms.

David OHara; Dr. Eric Lochmer

2003-09-12

345

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

346

Perturbation Expansion for High-Gain Free-Electron Laser Saturation  

SciTech Connect

We develop a perturbation expansion for the solution of the nonlinear one-dimensional free-electron laser equations. For a monochromatic wave, the radiation field is expanded in a Taylor series having a finite radius of convergence. Analytic continuation using Pade' approximates yields accurate results well into the saturation regime. We also formulate the perturbation expansion for finite bandwidth, self-amplified spontaneous-emission (SASE), and determine the lowest order correction to the well-known linear theory. Motivated by an approximation to the expansion coefficients, we introduce a simplified model for the SASE radiation field, and use it to discuss SASE statistics in the saturation regime, before the onset of the sideband instability.

Krinsky, Samuel

2003-01-02

347

Silicon Single-Hole Transistor with Large Coulomb Blockade Oscillations and High Voltage Gain at Room Temperature  

Microsoft Academic Search

We propose a new approach for realizing single-electron and single-hole transistors with both large Coulomb blockade oscillations and high voltage gain at room temperature. A thin gate oxide is adopted to increase gate capacitance and ultra-narrow channel is formed to reduce source and drain capacitance. The fabricated single-hole transistor shows large Coulomb blockade oscillations with peak-to-valley-current-ratio of 32 and high

Hidehiro Harata; Masumi Saitoh; Toshiro Hiramoto

2005-01-01

348

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

PubMed

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

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

2009-09-01

349

High attenuating external cavity for picosecond-tunable pulse generation from gain/Q-switched laser diodes  

SciTech Connect

The authors analyze in detail the behavior of gain/Q-switched Fabry-Perot laser diodes coupled to a highly attenuating, selective external cavity. Radical differences are shown as compared to the case of strong external feedback used in mode locking. Actually, they evidence a strong analogy with the case of pulsed lasers with a small quasi-monochromatic injection signal. Unlike previous experiments on laser diodes with selective external cavity, strong chirping is observed in single-mode emission, leading to tunable picosecond pulses after compression. Experiments are carried out on two types of devices. Picosecond pulses with very high tunability (40 nm) and repetition rates ([gt]10 GHz) are obtained from 1.3 [mu]m gain-switched laser diodes, the minimum pulsewidth being 2.5 ps. Ultrashort ([approximately]1 ps), high-power ([gt]5 W) tunable pulses are achieved with 0.8 [mu]m Q-switched lasers.

Bouchoule, S.; Stelmakh, N.; Cavelier, M.; Lourtioz, J.M. (Univ. Paris XI, Orsay (France))

1993-06-01

350

Characterization of a highly invasive and spontaneously metastatic human malignant melanoma cell line.  

PubMed

Although the incidence of, and deaths due to, malignant melanoma are rising at a rapid rate, few experimental models mimic the highly metastatic properties associated with the pathogenesis of the human disease, making study of the disease difficult. Thus, new human models are required to understand melanoma biology, especially its metastatic properties. Here we describe C8161, a highly invasive and spontaneously metastatic human melanoma cell line, which grows progressively in the subcutis of athymic nude mice with an average doubling time of approximately 6 days. By the time the tumor reaches a diameter of 1 cm, amelanotic metastases in lymph nodes, skin, peritoneal wall, spleen and lungs have formed. By comparing C8161 to variants from other well-characterized human malignant melanomas (A375 and MeWo) with differing metastatic traits, properties presumed to be involved in metastatic propensity were examined. C8161 showed a 2- to 14-fold higher ability to invade reconstituted basement membrane barriers in the MICS and correspondingly high type-IV collagenase mRNA levels and collagenolytic activity, as compared with other melanoma cell lines. Likewise, differential adhesion to immobilized RBM or HUVEC monolayers was observed, but did not correlate to rank orders of malignant properties. Recently, a correlation between surface expression of ICAM-1 and secondary tumor formation by human melanomas has been described in several laboratories. Basal levels of ICAM-1 on C8161, A375 and MeWo human melanomas were compared, but no correlation with metastatic potential was noted. Proto-oncogene expression in C8161 cells was compared with A375P and A375M variants using Northern blot analysis. c-myc expression was 6-fold greater than both A375 variants; c-fos expression was 3.4-fold less than A375P and 1.7-fold less than A375M; c-jun in C8161 cells was 2.5-fold and 2.1-fold greater than expression in A375P and A375M, respectively. Because C8161 is so highly malignant, amenable to experimental manipulation, and its behavior in nude mice mimics the clinical course of malignant melanoma, this cell line will prove valuable for studying properties associated with human melanoma tumor progression. PMID:1671030

Welch, D R; Bisi, J E; Miller, B E; Conaway, D; Seftor, E A; Yohem, K H; Gilmore, L B; Seftor, R E; Nakajima, M; Hendrix, M J

1991-01-21

351

High-salt intake and the renal expression of amino acid transporters in spontaneously hypertensive rats.  

PubMed

This study evaluated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) the response to salt loading of the renal dopaminergic system and transcript abundance of Na(+)-independent (LAT1 and LAT2) and Na(+)-dependent (ASCT2 and B(0)AT1) amino acid transporters potentially involved in renal tubular uptake of L-DOPA. Rats were fed normal (NS)- or high (HS; 1% saline as drinking water)-salt intake for 24 h. Transcript abundance of amino acid transporters was age dependent, differently regulated in WKY and SHR and responded differently to salt intake. HS intake similarly increased urinary dopamine in 4-wk-old SHR and WKY. At 12 wk of age, HS intake increased urinary dopamine in SHR, but not in WKY. Changes in urinary dopamine paralleled changes in the uptake of l-DOPA in isolated renal tubules from 4- and 12-wk-old WKY and SHR on NS and HS intake. At 12 wk of age, HS intake was accompanied by decreases in LAT1 and LAT2 transcript abundance in WKY and SHR. ASCT2 and B(0)AT1 expression was significantly decreased in both 4- and 12-wk-old WKY and in 4-wk-old SHR on HS intake. By contrast, HS intake increased ASCT2 and B(0)AT1 expression in 12-wk-old SHR. It is concluded that salt-sensitive mechanisms influence LAT1, LAT2, ASCT2, and B(0)AT1 gene transcription. Differences in urinary dopamine and tubular uptake of L-DOPA between WKY and SHR during HS intake, namely in 12-wk-old animals, may result from increases in the ASCT2 and B(0)AT1 mRNA levels and less pronounced decreases in LAT2 expression. PMID:17264310

Pinho, Maria João; Serrão, Maria Paula; Soares-da-Silva, Patrício

2007-05-01

352

A low voltage high unity-gain bandwidth CMOS op-amp  

Microsoft Academic Search

This work presents a ±1V CMOS operation amplifier with constant-gm rail-to-rail input stage and class-AB output stage. The designed op-amp has been implemented in TSMC 2P4M 0.35 ?m CMOS technology and simulated by Hspice. The unity-gain bandwidth of the op-amp is 13.1 MHz with Miller compensation. The slew-rate and settling time are 24V\\/?s and 0.48 ?s, respectively. The open loop

Chih-Min Yu; Zhi-Ming Lin; Jun-Da Chen

2004-01-01

353

High Efficiency Automatic-Power-Controlled and Gain-Clamped EDFA for Broadband Passive Optical Networking Systems  

NASA Astrophysics Data System (ADS)

The configuration of a simple improved high efficiency automatic-power-controlled and gain-clamped EDFA (APC-GC-EDFA) for broadband passive optical networking systems (BPON) is presented here. In order to compensate the phase and amplitude variation due to the different distance between the optical line terminal (OLT) and optical network units (ONU), the APC-GC-EDFA need to be employed. A single 980 nm laser module is employed as the primary pump. To extend the bandwidth, all C-band ASE is recycled as the secondary pump to enhance the gain efficiency. An electrical feedback circuit is used as a multi-wavelength channel transmitter monitor for the automatic power control to improve the gain-flattened flatness for stable amplification. The experimental results prove that the EDFA system can provide flatter clamped gain in both C-band and L-band configurations. The gain flatness wavelength ranging from 1530 to 1610 nm is within 32.83 ± 0.64 dB, i.e. below 1.95 %. The gains are clamped at 33.85 ± 0.65 dB for the input signal power of -40 dBm to -10 dBm. The range of noise figure is between 6.37 and 6.56, which is slightly lower compared to that of unclamped amplifiers. This will be very useful for measuring the gain flatness of APC-GC-EDFA. Finally, we have also demonstrated the records of the overall simultaneous dynamics measurements for the new system stabilization. The carrier to noise ratio (CNR) is 49.5 to 50.8 dBc which is above the National Television System Committee (NTSC) standard of 43 dBc, and both composite second order (CSO) 69.2 to 71.5 dBc and composite triple beat (CTB) of 69.8 to 72.2 dBc are above 53 dBc. The recorded corresponding rise-time of 1.087 ms indicates that the system does not exhibit any overshoot of gain or ASE variation due to the signal at the beginning of the pulse.

Shen, Jyi-Lai; Wei, Shui-Ken; Lin, Chin-Yuan; Iong Li, Ssu; Huang, Chih-Chuan

2010-04-01

354

Gain engineering for all-optical microwave and high speed pulse generation in mode-locked fiber lasers  

NASA Astrophysics Data System (ADS)

Pulsed sources based on approaches that employ only photonic components and no RF components will be discussed in this talk. Several technologies have been explored to generate actively mode-locked sources using electronically driven fiber ring cavities. However, for these sources the pulse repetition rate is usually limited by the bandwidth of the intracavity modulator. Filtering of highly-stable low repetition rate optical combs utilizing cavities such as Fabry-Perot etalons can be used to overcome this limitation. This scheme is not flexible as it requires highly precise control of ultrahigh finesse etalons which limits the repetition rate to the free spectral range of the filter. Pulsed sources based on semiconductor devices offer many advantages, including large gain bandwidth, rapid tunability, long-term stability. In this work we introduce a novel, simple method to generate optical clock with wavelength tunability using two continuous wave (CW) lasers. The lasers are injected into a conventional SOAs-based fiber ring laser. The beating signal generated by these two lasers causes the modulation of the SOA gain saturation inside the cavity. Thus, the SOA provides gain and functions as the modulator as well as the gain medium. When the lasing mode inside the cavity is amplified, it also results in gain-induced four wave mixing. The proposed technique is particularly versatile, overcoming the bandwidth limitation of other techniques, which require RF sources. Moreover, this technique provides the possibility for hybrid integration as it is comprised of semiconductor chips that can be heterogeneously integrated on a Si platform.

Li, Fangxin; Helmy, Amr S.

2014-03-01

355

Energy Gain in Collisions of Highly Charged Ions with C_60  

NASA Astrophysics Data System (ADS)

Within the dynamical classical over--barrier model for charge transfer in soft ion--cluster collisions [1], we have simulated [2] the kinetic energy gain Q of 3.3 q keV Ar^q+ ions in collisions with neutral C_60 targets. Our semi--classical theory allows for the calculation of Q in two different ways, either as difference of electronic binding energies before and after the collision or by integrating the dynamically changing force between the collision partners along the trajectory. A comparison between the two ways provides an intrinsic test of the model calculation. Comparison with recent experimental data [3] shows good agreement in the main features of the energy gain spectra and facilitates their interpretation in terms of the number and final states of transferred electrons. [1] U. Thumm, J. Phys. B27 3515 (1994); Phys. Rev. A55 (Jan.1997). [2] U. Thumm, A. Bárány and H. Cederquist, to be published. [3] N. Selberg et al., Phys. Rev. A 53, 874 (1996). description U.T. is supported by the Division of Chemical Sciences, Basis Energy Sciences, Office of Energy Research, U.S. Department of Energy.

Thumm, Uwe; Bárány, Anders; Cederquist, Henrik

1997-04-01

356

Novel nanosecond spectral continuum source — high intensity mode-less amplified spontaneous emission  

NASA Astrophysics Data System (ADS)

A broadband (up to about 70 nm) amplified spontaneous emission source giving an energy output of several milijoules and the very good spectral continuum has been developed. Its construction is fairly simple, the unit consists of two rectangular 1 cm cuvettes containing suitable dye solutions one of which is pumped by an excimer laser.

Ko?; os, Robert; Sepio?, Jerzy

1989-01-01

357

Interplay of the chirps and chirped pulse compression in a high-gain seeded free-electron laser  

SciTech Connect

In a seeded high-gain free-electron laser (FEL), where a coherent laser pulse interacts with an ultrarelativistic electron beam, the seed laser pulse can be frequency chirped, and the electron beam can be energy chirped. Besides these two chirps, the FEL interaction introduces an intrinsic frequency chirp in the FEL even if the above-mentioned two chirps are absent. We examine the interplay of these three chirps. The problem is formulated as an initial value problem and solved via a Green function approach. Besides the chirp evolution, we also give analytical expressions for the pulse duration and bandwidth of the FEL, which remains fully longitudinally coherent in the high-gain exponential growth regime. Because the chirps are normally introduced for a final compression of the FEL pulse, some conceptual issues are discussed. We show that to get a short pulse duration, an energy chirp in the electron beam is important.

Wu Juhao; Murphy, James B.; Emma, Paul J.; Wang Xijie; Watanabe, Takahiro; Zhong Xinming [Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Institute of Low Energy Nuclear Physics, Beijing Normal University, Beijing 100875 (China)

2007-03-15

358

Interplay of the Chirps and Chirped Pulse Compression in a High-gain Seeded Free-electron Laser  

SciTech Connect

In a seeded high-gain Free-electron Laser (FEL), where a coherent laser pulse interacts with an ultra-relativistic electron beam, the seed laser pulse can be frequency chirped, and the electron beam can be energy chirped. Besides these two chirps, the FEL interaction introduces an intrinsic frequency chirp in the FEL even if the above mentioned two chirps are absent. In this paper we examine the interplay of these three chirps. The problem is formulated as an initial value problem, and solved via a Green function approach. Besides the chirp evolution, we also give analytical expressions for the pulse duration and bandwidth of the FEL, which remains fully longitudinally coherent in the high gain exponential growth regime. Because the chirps are normally introduced for a final compression of the FEL pulse, some conceptual issues are discussed. We show that in order to get a short pulse duration, an energy chirp in the electron beam is necessary.

Wu, Juhao; /SLAC; Murphy, J.B.; /LBNL, ALS; Emma, P.J.; /SLAC; Wang, X.J.; Watanabe, T.; /LBNL, ALS; Zhong, Xinming; /Beijing Normal U.

2007-01-03

359

High magnetic shear gain in a liquid sodium stable couette flow experiment A prelude to an alpha - omega dynamo  

SciTech Connect

The {Omega}-phase of the liquid sodium {alpha}-{Omega} dynamo experiment at NMIMT in cooperation with LANL has successfully demonstrated the production of a high toroidal field, B{sub {phi}} {approx_equal} 8 x B{sub r} from the radial component of an applied poloidal magnetic field, B{sub r}. This enhanced toroidal field is produced by rotational shear in stable Couette Row within liquid sodium at Rm {approx_equal} 120. The small turbulence in stable Taylor-Couette Row is caused by Ekman Row where ({delta}v/v){sup 2} {approx} 10{sup -3}. This high {Omega}-gain in low turbulence flow contrasts with a smaller {Omega}-gain in higher turbulence, Helmholtz-unstable shear flows. This result supports the ansatz that large scale astrophysical magnetic fields are created within semi-coherent large scale motions in which turbulence plays a diffusive role that enables magnetic flux linkage.

Colgate, Stirling [Los Alamos National Laboratory; Li, Jui [Los Alamos National Laboratory; Finn, John [Los Alamos National Laboratory; Pariev, Vladimir [Los Alamos National Laboratory; Beckley, Howard [NM INSTIT. OF MINING AND TECH; Si, Jiahe [NM INSTIT. OF MINING AND TECH.; Martinic, Joe [NM INSTIT. OF MINING AND TECH.; Westpfahl, David [NM INSTIT. OF TECH.; Slutz, James [NM INSTIT. OF MINING AND TECH.; Westrom, Zeb [NM INSTIT. OF TECH.; Klein, Brianna [NM INSTIT. OF MINING AND TECH.

2010-11-08

360

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

Microsoft Academic Search

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

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

2011-01-01

361

Global tracking output-feedback sliding mode control design via norm estimators and variable high gain observer  

Microsoft Academic Search

An output-feedback sliding mode controller is proposed for a widely general class of single-input-single-output (SISO) time-varying uncertain nonlinear systems. Such a class encompasses plants in the state-of-the-art of global output-feedback control framework, possibly including strong polynomial nonlinearities in the unmeasured states. The sliding surface is generated by using the state of a high gain observer (HGO) while the control signal

Alessandro Jacoud Peixoto; Tiago Roux Oliveira; Liu Hsu

2009-01-01

362

Robustness property of high-gain observers for closed-loop nonlinear systems: theoretical study and robotics control application  

Microsoft Academic Search

The robust stability problem for a wide class of closed-loop nonlinear systems is considered. A nonlinear feedback is assumed to be a function of current state estimates obtained by a nonlinear high-gain observer. The problem is solved in the presence of essential parametric uncertainties as well as external perturbation noise (mixed uncertainties). A two Riccati-equation approach is applied. We demonstrate

Rafael Martinez Guerra; Alexander Poznyak; Vicente Diaz De Leon

2000-01-01

363

PARAMETER ANALYSIS FOR A HIGH-GAIN HARMONIC GENERATION FEL BY NUMERICAL CALCULATION BASED ON 1D THEORY  

Microsoft Academic Search

High-gain harmonic generation (HGHG) free-electron laser (FEL) is an important candidate for fourth- generation light source. Lots of research works about it have been done all along. Recently a further 1D theory about HGHG FEL has been developed. It considers the effects of different parameters for the whole process. An initial program based on this theory has been made. In

Li Yuhui; Jia Qika; Zhang Shancai

364

A high gain n-well\\/gate tied PMOSFET image sensor fabricated from a standard CMOS process  

Microsoft Academic Search

The performance of a high gain photodetector fabricated using a standard 0.8-?m, triple metal, n-well CMOS process is reported, The photodetector is formed by connecting the gate of the PMOSFET and n-well together while keeping both floating. The depletion region induced by the floating gate and the well-to-substrate p-n junction separate the optically generated electron-hole pairs in the direction perpendicular

Weiquan Zhang; Mansun Chan

2001-01-01

365

A Low Profile, MultiBand Yagi Antenna with High Gain Characteristic over an EBG Ground Plane  

Microsoft Academic Search

Design of a closely spaced Yagi antenna over an electromagnetic band-gap (EBG) ground plane is suggested to achieve multi-bands with high gains. The total height from the top of the EBG ground plane to the director is 0.03?. The first resonance occurs due to the driver of the Yagi over the EBG ground plane (dipole mode). The second resonance is

JinHui Kim; Sungkyun Lim; Magdy F. Iskander; Jodie M. Bell

366

Investigation of Larger Poly({alpha}-Methylstyrene) Mandrels for High Gain Designs Using Microencapsulation  

SciTech Connect

In recent years we have demonstrated that 2-mm-diameter poly({alpha}-methylstyrene) mandrels meeting indirect drive NIF surface symmetry specifications can be produced using microencapsulation methods. Recently higher gain target designs have been introduced that rely on frequency doubled (green) laser energy and require capsules up to 4 mm in diameter, nominally meeting the same surface finish and symmetry requirements as the existing 2-mm-diameter capsule designs. Direct drive on the NIF also requires larger capsules. In order to evaluate whether the current microencapsulation-based mandrel fabrication techniques will adequately scale to these larger capsules, we have explored extending the techniques to 4-mm-diameter capsules. We find that microencapsulated shells meeting NIF symmetry specifications can be produced, the processing changes necessary to accomplish this are presented here.

Takagi, Masaru [Lawrence Livermore National Laboratory (United States); Cook, Robert [Lawrence Livermore National Laboratory (United States); McQuillan, Barry [General Atomics (United States); Gibson, Jane [General Atomics (United States); Paguio, Sally [General Atomics (United States)

2004-03-15

367

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

SciTech Connect

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.

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

368

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

NASA Astrophysics Data System (ADS)

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.

Atzeni, Stefano; Marocchino, Alberto; Schiavi, Angelo

2012-09-01

369

High gain-production efficiency and large brightness X-UV laser at Palaiseau  

SciTech Connect

A large gain has been measured for the J=0-1 line of neonlike Zn at {lambda}=21.2 nm. The time evolutions and the localization of emission zones of the J=0-1 and J=2-1 lines are compared. It is shown that a train of very small prepulses before the main pulse has an important role in the J=0=1 emission. A half-cavity has been successfully used to attain a nearly saturated intensity with a 2 cm long plasma. The X-UV pulse energy is of 400 {mu}J, the laser power of 5 MW. The driving laser is the 0.4 KJ, 600 ps laser of LULI.

Jaegle, P.; Carillon, A.; Dhez, P.; Goedtkindt, P.; Jamelot, G.; Klisnick, A.; Rus, B.; Zeitoun, Ph.; Jacquemot, S.; Mazataud, D.; Mens, A.; Chauvineau, J. P. [Laboratorie de Spectroscopie Atomique et Ionique, Bat 350, Universite Paris-Sud, 91405 Orsay (France); C. E. A., Centre d'Etudes de Limeil-Valenton, 94190 Villeneuve-St.-Georges (France); Institut d'Optique Theorique et Appliquee, 91405 Orsay (France)

1995-05-01

370

On the Fielding of a High Gain, Shock-Ignited Target on the National Ignitiion Facility in the Near Term  

SciTech Connect

Shock ignition, a new concept for igniting thermonuclear fuel, offers the possibility for a near-term ({approx}3-4 years) test of high gain inertial confinement fusion on the National Ignition Facility at less than 1MJ drive energy and without the need for new laser hardware. In shock ignition, compressed fusion fuel is separately ignited by a strong spherically converging shock and, because capsule implosion velocities are significantly lower than those required for conventional hotpot ignition, fusion energy gains of {approx}60 may be achievable on NIF at laser drive energies around {approx}0.5MJ. Because of the simple all-DT target design, its in-flight robustness, the potential need for only 1D SSD beam smoothing, minimal early time LPI preheat, and use of present (indirect drive) laser hardware, this target may be easier to field on NIF than a conventional (polar) direct drive hotspot ignition target. Like fast ignition, shock ignition has the potential for high fusion yields at low drive energy, but requires only a single laser with less demanding timing and spatial focusing requirements. Of course, conventional symmetry and stability constraints still apply. In this paper we present initial target performance simulations, delineate the critical issues and describe the immediate-term R&D program that must be performed in order to test the potential of a high gain shock ignition target on NIF in the near term.

Perkins, L J; Betti, R; Schurtz, G P; Craxton, R S; Dunne, A M; LaFortune, K N; Schmitt, A J; McKenty, P W; Bailey, D S; Lambert, M A; Ribeyre, X; Theobald, W R; Strozzi, D J; Harding, D R; Casner, A; Atzemi, S; Erbert, G V; Andersen, K S; Murakami, M; Comley, A J; Cook, R C; Stephens, R B

2010-04-12

371

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

NASA Astrophysics Data System (ADS)

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.

Linga, Krishna; Yevtukhov, Yuriy; Liang, Bing

2010-04-01

372

Quercetin decreases high-fat diet induced body weight gain and accumulation of hepatic and circulating lipids in mice.  

PubMed

Dietary flavonoids may protect against cardiovascular diseases (CVD). Increased circulating lipid levels and hepatic lipid accumulation are known risk factors for CVD. The aim of this study was to investigate the effects and underlying molecular mechanisms of the flavonoid quercetin on hepatic lipid metabolism in mice with high-fat diet induced body weight gain and hepatic lipid accumulation. Adult male mice received a 40 energy% high-fat diet without or with supplementation of 0.33 % (w/w) quercetin for 12 weeks. Body weight gain was 29 % lower in quercetin fed mice (p < 0.01), while the energy intake was not significantly different. Quercetin supplementation lowered hepatic lipid accumulation to 29 % of the amount present in the control mice (p < 0.01). (1)H nuclear magnetic resonance serum lipid profiling revealed that the supplementation significantly lowered serum lipid levels. Global gene expression profiling of liver showed that cytochrome P450 2b (Cyp2b) genes, key target genes of the transcription factor constitutive androstane receptor (Car; official symbol Nr1i3), were downregulated. Quercetin decreased high-fat diet induced body weight gain, hepatic lipid accumulation and serum lipid levels. This was accompanied by regulation of cytochrome P450 2b genes in liver, which are possibly under transcriptional control of CAR. The quercetin effects are likely dependent on the fat content of the diet. PMID:25047408

Hoek-van den Hil, E F; van Schothorst, E M; van der Stelt, I; Swarts, H J M; Venema, D; Sailer, M; Vervoort, J J M; Hollman, P C H; Rietjens, I M C M; Keijer, J

2014-09-01

373

High-voltage operation with high current gain of pnp AlGaN/GaN heterojunction bipolar transistors with thin n-type GaN base  

NASA Astrophysics Data System (ADS)

A pnp AlGaN/GaN heterojunction bipolar transistor (HBT) with a thin n-GaN base shows high-voltage operation with high current gain in the common-emitter configuration at room temperature. The device structure was grown by metalorganic vapor phase epitaxy on a sapphire substrate. The emitter area is 30 ?m×50 ?m. The HBT can operate at high voltage of 70 V with the maximum current gain of 40 at the collector current of 10 mA. The maximum output power density is 172 kW/cm2. Transport characteristics in the HBT were also investigated. At small collector current, the current gain is dominated by the recombination current at the emitter-base heterojunction. At moderate collector current, the calculated minority hole diffusion length well agreed with that determined from electron beam induced current measurements, indicating the current gain is dominated by the minority carrier diffusion. At large collector current, a high injection effect was observed in the current gain characteristics.

Kumakura, Kazuhide; Makimoto, Toshiki

2005-01-01

374

Spontaneous formation of highly regular superlattice structure in InGaN epilayers grown by molecular beam epitaxy  

SciTech Connect

In this letter, we have investigated the structural properties of thick InGaN layers grown on GaN by plasma-assisted molecular beam epitaxy, using two growth rates of 1.0 and 3.6 A/s. A highly regular superlattice (SL) structure is found to be spontaneously formed in the film grown at 3.6 A/s but not in the film grown at 1.0 A/s. The faster grown film also exhibits superior structural quality, which could be due to the surface roughness suppression caused by kinetic limitation, and the inhibition of the Frank-Read dislocation generation mechanism within the spontaneously formed SL structure.

Wu, Z. H. [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Graduate School of Engineering, Akasaki Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Kawai, Y.; Honda, Y.; Yamaguchi, M.; Amano, H. [Graduate School of Engineering, Akasaki Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Fang, Y.-Y.; Chen, C. Q. [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Kondo, H.; Hori, M. [Graduate School of Engineering, Plasma Nanotechnology Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan)

2011-04-04

375

Dynamic high-gain scaling: State and output feedback with application to systems with ISS appended dynamics driven by all States  

Microsoft Academic Search

We propose a dynamic high-gain scaling technique and solutions to coupled Lyapunov equations leading to results on state-feedback, output-feedback, and input-to-state stable (ISS) appended dynamics with nonzero gains from all states and input. The observer and controller designs have a dual architecture and utilize a single dynamic scaling. A novel procedure for designing the dynamics of the high-gain parameter is

P. Krishnamurthy; F. Khorrami

2004-01-01

376

Experimental verification of high spectral entanglement for pulsed waveguided spontaneous parametric down-conversion  

Microsoft Academic Search

We study the spectral properties of spontaneous parametric down-conversion (SPDC) in a periodically poled waveguided structure of potassium-titanyl-phosphate (KTP) crystal pumped by ultrashort pulses. Our theoretical analysis reveals a strongly entangled and asymmetric structure of the two-photon spectral amplitude for type-II SPDC. We confirm these predictions experimentally by measuring single-photon spectra, on one hand, and the dependence of Hong-Ou-Mandel interference

Malte Avenhaus; Maria V. Chekhova; Leonid A. Krivitsky; Gerd Leuchs; Christine Silberhorn

2009-01-01

377

Optical parametric gain and bandwidth in highly nonlinear tellurite hybrid microstructured optical fiber with four zero-dispersion wavelengths.  

PubMed

The parametric amplification gain and bandwidth in highly nonlinear tellurite hybrid microstructured optical fiber (HMOF) are simulated based on four wave mixing process. The fiber core and cladding materials are made of TeO(2)–Li(2)O–WO(3)–MoO(3)–Nb(2)O(5) and TeO(2)–ZnO–Na(2)O–P(2)O(5) glass, respectively. The fiber has four zero-dispersion wavelengths and the chromatic dispersion is flattened near the zerodispersion wavelengths. A broad gain bandwidth as wide as 1200 nm from 1290 to 2490 nm can be realized in the near infrared window by using a tellurite HMOF as short as 25 cm. PMID:24105576

Tuan, Tong Hoang; Cheng, Tonglei; Asano, Koji; Duan, Zhongchao; Gao, Weiqing; Deng, Dinghuan; Suzuki, Takenobu; Ohishi, Yasutake

2013-08-26

378

3D theory of a high-gain free-electron laser based on a transverse gradient undulator  

NASA Astrophysics Data System (ADS)

The performance of a free-electron laser (FEL) depends significantly on the various parameters of the driving electron beam. In particular, a large energy spread in the beam results in a substantial reduction of the FEL gain, an effect which is especially relevant when one considers FELs driven by plasma accelerators or ultimate storage rings. For such cases, one possible solution is to use a transverse gradient undulator (TGU). In this concept, the energy spread problem is mitigated by properly dispersing the electron beam and introducing a linear, transverse field dependence in the undulator. This paper presents a self-consistent theoretical analysis of a TGU-based, high-gain FEL which takes into account three-dimensional (3D) effects, including beam size variations along the undulator. The results of our theory compare favorably with simulation and are used in fast optimization studies of various x-ray FEL configurations.

Baxevanis, Panagiotis; Ding, Yuantao; Huang, Zhirong; Ruth, Ronald

2014-02-01

379

High-gain amplification in Yb:CaF2 crystals pumped by a high-brightness Yb-doped 976 nm fiber laser  

NASA Astrophysics Data System (ADS)

We report on high single-pass gain in Yb:CaF2 crystal longitudinally pumped with a 40 W high-brightness fiber laser source based on an ytterbium-doped ultra-large core photonic crystal rod-type fiber operating at 976 nm. A single-pass small-signal gain of 3.2 has been achieved in a 6 % Yb-doped 10-mm-long CaF2 crystal at room temperature, outperforming any CW-diode-pumped scheme and paving the way towards very promising innovative lasers and amplifiers schemes merging the Yb-doped solid-state and fiber technologies.

Machinet, G.; Andriukaitis, G.; Sévillano, P.; Lhermite, J.; Descamps, D.; Pugžlys, A.; Baltuška, A.; Cormier, E.

2013-05-01

380

Tunability of Injection Seeded High-Repetition Rate Ti:Sapphire Laser Far Off the Gain Peak  

SciTech Connect

We have investigated a tunability of a high-repetition rate Ti:Sapphire laser seeded off the gain peak. By applying a birefringent filter, the 7 kHz injection seeded Ti:Sapphire laser system was operated with the average seeding efficiency of over 90% and the output power of over 1 W on the spectral range of 900-930 nm. We conclude that the birefringent filter suited for widely tunable operation of the injection seeded Ti:Sapphire laser system operated at high repetition rate.

Tomita, H.; Muramatsu, T.; Watanabe, K.; Iguchi, T. [Graduate School of Engineering, Nagoya University, Nagoya, 464-8603 (Japan); Mattolat, Ch.; Wendt, K. [Institute of Physics, Johannes Gutenberg-Universitaet Mainz, 55099, Mainz (Germany); Kessler, Th. [Institute of Physics, Johannes Gutenberg-Universitaet Mainz, 55099, Mainz (Germany); Department of Physics, University of Jyvaeskylae, 40014 (Finland)

2009-03-17

381

Study of ageing and gain limits of Microstrip Gas Chambers at high rates  

Microsoft Academic Search

The CMS experiment comprises MSGCs as one of the key detection elements for high luminosity tracking at LHC. In addition to the high dose rate of 10mC\\/year per cm of strip, these detectors have to survive the hostile presence of highly ionizing particles, neutrons low energy gammas and hadrons. In this report we present the results of systematic tests on

B. Boimska; R. Bouclier; M. Capeáns; S. Claes; W. Dominik; M. Hoch; G. Million; L. Ropelewski; F. Sauli; A. Sharma; L. Shekhtman; W. van Doninck; Luk van Lancker

1997-01-01

382

Oscillator seeding of a high gain harmonic generation free electron laser in a radiator-first configuration  

NASA Astrophysics Data System (ADS)

A longitudinally and transversely coherent, high repetition rate x-ray source with widely tunable wavelength is desired for a variety of experimental applications. A free electron laser (FEL) powered by an electron beam from a superconducting linac can reach the desired peak and average x-ray power levels with transverse coherence. However, generating longitudinally coherent x-ray pulses is a significant challenge, especially at high repetition rate. This paper presents a one-dimensional theoretical and numerical investigation of a method to achieve longitudinal coherence and high repetition rate simultaneously. We propose a “radiator-first” configuration, wherein an FEL oscillator follows a high gain harmonic generation (HGHG) FEL. The oscillator generates seed power that is directed upstream to initiate the HGHG process in a following electron bunch. This configuration allows for the generation of radiation at short wavelength, which is highly sensitive to energy spread, to occur before the longer wavelength oscillator, whose performance is not seriously degraded by the beam heating in the upstream radiator. The dynamics and stability of this radiator-first scheme is explored analytically and numerically. A single-pass, 1D map is derived using a semianalytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations. A numerical example is presented for a soft x-ray FEL.

Gandhi, P.; Penn, G.; Reinsch, M.; Wurtele, J. S.; Fawley, W. M.

2013-02-01

383

Effects of vitamin C on high blood pressure induced by salt in spontaneously hypertensive rats.  

PubMed

By breeding and feeding salt to spontaneously hypertensive rats (SHR) continuously over a long period (until 60 wk old), rats with systolic blood pressures (SBP) of over 270 mmHg were prepared. It was studied whether or not supplying large amounts of vitamin C (200 mg/rat/d) over this period might bring any beneficial effect to blood pressure. Moreover, physico-chemical studies were performed to measure the components and enzymes in the blood and urine at 53 and 60 wk-old, and biochemical studies on vitamin C were also carried out in this experiment. Male (14 rats: 7 wk-old, 100-105 g) and female (15 rats: 7 wk-old, 95-100 g) SHR were divided into three groups and bred continuously for 53 wk. The A group rats were given salt (2.5 g/100 g of diet), the B group rats were given salt and vitamin C (500 mg/100 mL of drinking water), and the C group rats were controls. The results showed almost the same tendencies between male and female rats. The body weights of the SHR in groups A and B were slightly lower than group C. The amount of food intake in groups A and B was almost the same as group C. The amount of water intake was, in the order from highest to lowest, group A, B and C. The SBP of group A rats exhibited the highest value among the three groups. The SBP of group B rats given vitamin C simultaneously with the salt resulted in a low blood pressure level close to that of the controls (group C). Furthermore, the DBP (diastolic blood pressure) also reflected the antihypertensive effect of vitamin C as well. The heartbeat of the rats was highest in group A, and was comparable to the value in the rats receiving vitamin C simultaneously with salt. For the tests on occult blood and protein in the urine, group A rats showed strong positive reactions, whereas the group B and C rats had decreased results for both tests. The organ weights of the liver, stomach, spleen, adrenal gland and kidneys per 100 g rat body weight were not different among the three groups. The values for the bilirubin content, and the enzyme activities of ALT and AST in the blood showed to be the highest in the male rats of group A. The values from the group B rats decreased near to the normal value like the control group. Vitamin C was found to decrease the blood pressure in SHR, and also to work effectively to protect liver and kidney functions even under the condition of very high blood pressure, as high as 250 mmHg. PMID:14703303

Nishikawa, Yoshiyuki; Tatsumi, Kaori; Matsuura, Takeshi; Yamamoto, Ayako; Nadamoto, Tomonori; Urabe, Kimiko

2003-10-01

384

Testing and performance of a high-gain flux-compression generator  

Microsoft Academic Search

A workable high-grain, high-explosive helical magnetic-flux-compression generator (HEG) must be fabricated with the required tolerances, and the expanding high explosive and armature must be centered and radically uniform. The tolerance and expansion issues were tested with a mini-HEG having a constant density of stator turns that would simulate the first part of a full-scale generator, which also has a constant

P. A. Pincosy; J. L. Cutting; J. B. Chase

1989-01-01

385

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

Microsoft Academic Search

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

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

386

Surface plasmon resonance-induced color-selective Au-peapodded silica nanowire photodetectors with high photoconductive gain  

NASA Astrophysics Data System (ADS)

We report the optoelectronic device properties of individual Au-silica hybrid nanowires prepared by microwave plasma enhanced chemical vapor deposition. Due to the surface plasmon resonance (SPR) effect the photo-responsivity peak strongly depends on the shape of the embedded gold nanostructures in the silica nanowire in which the shape can be modified by controlling the growth time of Au-silica nanowires. Finite difference time domain (FDTD) simulation shows that the electric field distribution profiles of Au-silica hybrid nanowires support the photo-responsivity spectrum results. The photodetector performance of the Au-NPs@silica nanowire is investigated. The single Au-NPs@silica nanowire exhibits unique photo-responsivity in the visible range (500 nm), high selectivity, high photoconductive gain, and very fast rise (141 ?s) and decay (298 ?s) time constants. Furthermore, the mechanism for the high photoconductive gain is also discussed. This result implies that the Au-NPs@silica nanowire can be applied for future nanoscale optoelectronic devices.We report the optoelectronic device properties of individual Au-silica hybrid nanowires prepared by microwave plasma enhanced chemical vapor deposition. Due to the surface plasmon resonance (SPR) effect the photo-responsivity peak strongly depends on the shape of the embedded gold nanostructures in the silica nanowire in which the shape can be modified by controlling the growth time of Au-silica nanowires. Finite difference time domain (FDTD) simulation shows that the electric field distribution profiles of Au-silica hybrid nanowires support the photo-responsivity spectrum results. The photodetector performance of the Au-NPs@silica nanowire is investigated. The single Au-NPs@silica nanowire exhibits unique photo-responsivity in the visible range (500 nm), high selectivity, high photoconductive gain, and very fast rise (141 ?s) and decay (298 ?s) time constants. Furthermore, the mechanism for the high photoconductive gain is also discussed. This result implies that the Au-NPs@silica nanowire can be applied for future nanoscale optoelectronic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04533a

Wang, Sheng-Bo; Chen, Ruei-San; Chang, Shoou Jinn; Han, Hsieh-Cheng; Hu, Ming-Shien; Chen, Kuei-Hsien; Chen, Li-Chyong

2014-01-01

387

On the ignition of high gain thermonuclear microexplosions with electric pulse power  

Microsoft Academic Search

It was recently shown that the ignition of thermonuclear microexplosions seems possible with two Marx generators of modest size, one with a high current lower voltage for compression and confinement, and one with a high voltage lower current for ignition, transmitting their energy to the thermonuclear target by two nested magnetically insulated transmission lines. Here it is shown in much

F. Winterberg

2004-01-01

388

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

PubMed Central

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.

2012-01-01

389

Experimental verification of high spectral entanglement for pulsed waveguided spontaneous parametric down-conversion  

NASA Astrophysics Data System (ADS)

We study the spectral properties of spontaneous parametric down-conversion (SPDC) in a periodically poled waveguided structure of potassium-titanyl-phosphate (KTP) crystal pumped by ultrashort pulses. Our theoretical analysis reveals a strongly entangled and asymmetric structure of the two-photon spectral amplitude for type-II SPDC. We confirm these predictions experimentally by measuring single-photon spectra, on one hand, and the dependence of Hong-Ou-Mandel interference visibility on the width of spectral filtering, on the other hand.

Avenhaus, Malte; Chekhova, Maria V.; Krivitsky, Leonid A.; Leuchs, Gerd; Silberhorn, Christine

2009-04-01

390

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

Microsoft Academic Search

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

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

391

Weight Gain Induced by High-Fat Feeding Involves Increased Liver Oxidative Stress  

Microsoft Academic Search

Objective: To assess the effects of high-fat feeding on white adipose tissue gene expression and liver oxidative stress.Research Methods and Procedures: Male Wistar rats were fed on standard pelleted or high-fat diet to produce a diet-induced obesity model. Therefore, body composition, serum biochemical values and liver malondialdehyde (MDA) were determined after 56 days of feeding. Expression (mRNA) values of three

Fermín I. Milagro; Javier Campión; J. Alfredo Martínez

2006-01-01

392

An overview of feed-forward design techniques for high-gain wideband operational transconductance amplifiers  

Microsoft Academic Search

In this paper, feed-forward techniques are revised and used for the design of high-frequency operational transconductance amplifiers (OTA). For the same power consumption and similar transistor dimensions, the two- and three-path folded-cascode OTA's present both smaller settling error and faster response as compared to the typical folded-cascode topology. Also, a no-capacitor feed-forward (NCFF) compensation which uses a high-frequency pole-zero doublet

Bharath Kumar Thandri; José Silva-martinez

2006-01-01

393

High-power Er-Yb-doped fiber amplifier with multichannel gain flatness within 0.2 dB over 14 nm  

Microsoft Academic Search

A high-power Er-Yb fiber amplifier for WDM applications has been constructed using a matched mid-stage gain shaping filter. Using precise measurements and careful design considerations, excellent gain flatness, with less than 0.2-dB variation, was obtained over a 14-nm spectral bandwidth. By simply adjusting the pump power to the amplifier, it was possible to maintain the flattened amplifier gain shape over

Paul Wysocki; Renee Pedrazzani; Steve Grubb; David DiGiovanni; Ken Walker

1996-01-01

394

Statistical properties of radiation power levels from a high-gain free-electron laser at and beyond saturation  

NASA Astrophysics Data System (ADS)

We investigate the statistical properties (e.g., shot-to-shot power fluctuations) of the radiation from a high-gain free-electron laser (FEL) operating in the nonlinear regime. We consider the case of an FEL amplifier reaching saturation whose shot-to-shot fluctuations in input radiation power follow a gamma distribution. We analyze the corresponding output power fluctuations at and beyond saturation, including beam energy spread effects, and find that there are well-characterized values of undulator length for which the fluctuations reach a minimum.

Schroeder, C. B.; Fawley, W. M.; Esarey, E.

2003-07-01

395

Statistical properties of radiation power levels from a high-gain free-electron laser at and beyond saturation  

SciTech Connect

We investigate the statistical properties (e.g., shot-to-shot power fluctuations) of the radiation from a high-gain free-electron laser (FEL) operating in the nonlinear regime. We consider the case of an FEL amplifier reaching saturation whose shot-to-shot fluctuations in input radiation power follow a gamma distribution. We analyze the corresponding output power fluctuations at and beyond first saturation, including beam energy spread effects, and find that there are well-characterized values of undulator length for which the fluctuation level reaches a minimum.

Schroeder, Carl B.; Fawley, William M.; Esarey, Eric

2002-09-24

396

Surface plasmon resonance-induced color-selective Au-peapodded silica nanowire photodetectors with high photoconductive gain.  

PubMed

We report the optoelectronic device properties of individual Au-silica hybrid nanowires prepared by microwave plasma enhanced chemical vapor deposition. Due to the surface plasmon resonance (SPR) effect the photo-responsivity peak strongly depends on the shape of the embedded gold nanostructures in the silica nanowire in which the shape can be modified by controlling the growth time of Au-silica nanowires. Finite difference time domain (FDTD) simulation shows that the electric field distribution profiles of Au-silica hybrid nanowires support the photo-responsivity spectrum results. The photodetector performance of the Au-NPs@silica nanowire is investigated. The single Au-NPs@silica nanowire exhibits unique photo-responsivity in the visible range (500 nm), high selectivity, high photoconductive gain, and very fast rise (141 ?s) and decay (298 ?s) time constants. Furthermore, the mechanism for the high photoconductive gain is also discussed. This result implies that the Au-NPs@silica nanowire can be applied for future nanoscale optoelectronic devices. PMID:24326397

Wang, Sheng-Bo; Chen, Ruei-San; Chang, Shoou Jinn; Han, Hsieh-Cheng; Hu, Ming-Shien; Chen, Kuei-Hsien; Chen, Li-Chyong

2014-01-16

397

Antagonism of T-type calcium channels inhibits high-fat diet-induced weight gain in mice  

PubMed Central

The epidemics of obesity and metabolic disorders have well-recognized health and economic burdens. Pharmacologic treatments for these diseases remain unsatisfactory with respect to both efficacy and side-effect profiles. Here, we have identified a potential central role for T-type calcium channels in regulating body weight maintenance and sleep. Previously, it was shown that mice lacking CaV3.1 T-type calcium channels have altered sleep/wake activity. We found that these mice were also resistant to high-fat diet–induced weight gain, without changes in food intake or sensitivity to high-fat diet–induced disruptions of diurnal rhythm. Administration of a potent and selective antagonist of T-type calcium channels, TTA-A2, to normal-weight animals prior to the inactive phase acutely increased sleep, decreased body core temperature, and prevented high-fat diet–induced weight gain. Administration of TTA-A2 to obese rodents reduced body weight and fat mass while concurrently increasing lean muscle mass. These effects likely result from better alignment of diurnal feeding patterns with daily changes in circadian physiology and potentially an increased metabolic rate during the active phase. Together, these studies reveal what we believe to be a previously unknown role for T-type calcium channels in the regulation of sleep and weight maintenance and suggest the potential for a novel therapeutic approach to treating obesity.

Uebele, Victor N.; Gotter, Anthony L.; Nuss, Cindy E.; Kraus, Richard L.; Doran, Scott M.; Garson, Susan L.; Reiss, Duane R.; Li, Yuxing; Barrow, James C.; Reger, Thomas S.; Yang, Zhi-Qiang; Ballard, Jeanine E.; Tang, Cuyue; Metzger, Joseph M.; Wang, Sheng-Ping; Koblan, Kenneth S.; Renger, John J.

2009-01-01

398

High-Pass Filtering and Dynamic Gain Regulation Enhance Vertical Bursts Transmission along the Mossy Fiber Pathway of Cerebellum.  

PubMed

Signal elaboration in the cerebellum mossy fiber input pathway presents controversial aspects, especially concerning gain regulation and the spot-like (rather than beam-like) appearance of granular to molecular layer transmission. By using voltage-sensitive dye imaging in rat cerebellar slices (Mapelli et al., 2010), we found that mossy fiber bursts optimally excited the granular layer above approximately 50 Hz and the overlaying molecular layer above approximately 100 Hz, thus generating a cascade of high-pass filters. NMDA receptors enhanced transmission in the granular, while GABA-A receptors depressed transmission in both the granular and molecular layer. Burst transmission gain was controlled through a dynamic frequency-dependent involvement of these receptors. Moreover, while high-frequency transmission was enhanced along vertical lines connecting the granular to molecular layer, no high-frequency enhancement was observed along the parallel fiber axis in the molecular layer. This was probably due to the stronger effect of Purkinje cell GABA-A receptor-mediated inhibition occurring along the parallel fibers than along the granule cell axon ascending branch. The consequent amplification of burst responses along vertical transmission lines could explain the spot-like activation of Purkinje cells observed following punctuate stimulation in vivo. PMID:20577586

Mapelli, Jonathan; Gandolfi, Daniela; D'Angelo, Egidio

2010-01-01

399

Evolution of electron beam phase space distribution in a high-gain FEL  

SciTech Connect

FEL-based coherent electron cooling (CEC) offers a new avenue to achieve high luminosities in high energy colliders such as RHIC, LHC, and eRHIC. Traditional treatments consider the FEL as an amplifier of optical waves with specific initial conditions, focusing on the resulting field. CEC requires knowledge of the phase space distribution of the electron beam in the FEL. We present 1D analytical results for the phase space distribution of an electron beam with an arbitrary initial current profile, and discuss approaches of expanding to 3D results.

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

2009-08-23

400

Gain measurements of the superconducting vortex flow transistor at high frequencies  

SciTech Connect

This paper presents measurements of transresistance of the vortex flow transistor (VFT). These measurements were obtained at frequencies up to 500 MHz which was one-tenth of the transit time cutoff frequency. A signal tagging scheme was developed to detect these high-frequency signals that would otherwise be obscured by high crosstalk levels. The measured frequency response of the VFT indicates that the transresistance signal is present at frequencies greater than one-tenth of the transit time cutoff frequency. Thus, the VFT is a viable active device candidate for rf superconducting electronic systems.

McGinnis, D.P.; Beyer, J.B.; Nordman, J.E.

1988-04-15

401

High gain optical detection with GaAs field effect transistors.  

PubMed

The photoresponse of GaAs field effect transistor (FET) optical detectors to optical intensity modulation signals of moderate frequency is investigated. High ac responsivity is available at frequencies of interest in optical communications: more than 6 A/W can be obtained up to 100 MHz, with a noise equivalent power of <10(-12) W/ radicalHz. The slope of the frequency response is dependent on the otpical bias power, an effect that can be attributed to traps. The GaAs FET optical detector complements the performance of available P-I-N and avalanche photodiode photodetectors for communications by providing high photoresponse at low bias voltages. PMID:20309161

Macdonald, R I

1981-02-15

402

High gain CMOS image sensor design and fabrication on SOI and bulk technology  

Microsoft Academic Search

The CMOS imager is now competing with the CCD imager, which still dominates the electronic imaging market. By taking advantage of the mature CMOS technology, the CMOS imager can integrate AID converters, digital signal processing (DSP) and timing control circuits on the same chip. This low cost and high-density integration solution to the image capture is the strong driving force

Weiquan Zhang

2000-01-01

403

Performance optimization of diffused Li on Ga/In eutectic, In/Sn solder and eutectic Ga/In Ohmic contacts to n-high purity-crystalline (100) Ge  

NASA Astrophysics Data System (ADS)

Performance optimization study of novel contacts such as diffused lithium on Ga/In eutectic (75.5/24.5 wt%), In/Sn solder (95.0/5.0 wt%) and Ga/In eutectic (75.5/24.5 wt%) to n-high purity-crystalline <100> Ge (HP-SC-Ge) has been presented. Ultrasonically clean samples taken from same substrate were used to process the contacts followed by their characterization utilizing current--voltage (I--V), Hall-effect and AFM measurements. Extreme care was introduced to minimize the effect of parasitic oxide layers. Contacts such as diffused Li on eutectic Ga/In and In/Sn solder were processed in an inert glove box and characterized at 305 K (RT) and 77 K (LN) respectively. Comparative study revealed that Ga/In eutectics contacts behave throughout linear and stable, showing strong hall-effect to that of its counter parts. This was attributed due to the high adsorption behavior of anions at liquid (Ga--In) contacts and improved wettability. Whereas, for In/Sn solder case, the contacts processing considerations were substantially different, mainly because of its poor solder flow, excessive void formation, and heterogeneous phase distribution responsible for process yield loss. For diffused Li on Ga/In eutectic contacts, the linearity of the obtained Ohmic profiles was not consistent due to the high reactivity of the Li with HP-SC-Ge substrate. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

Khan, Khizar; Gang, Yang; Wang, Guojian; Xiang, Wenchang; Guan, Yutong; Mei, Dongming

2012-02-01

404

Sinusoidal voltage control of a single phase uninterruptible power supply by a high gain PI circuit  

Microsoft Academic Search

This paper presents analysis and design of a new control method of a single-phase voltage-source uninterruptible power supply (UPS) inverter with a high Q L-C low-pass filter. When a PWM inverter is used to feed the load, a L-C low-pass filter must be employed to eliminate the switching frequency component of output voltage harmonics. But, it may be observed that

Akira Moriyama; I. Ando; I. Takahashi

1998-01-01

405

The Shanghai high-gain harmonic generation DUV free-electron laser  

Microsoft Academic Search

The Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) is an HGHG FEL facility designed for generating coherent output with wavelength down to 88nm. The design and the relevant R&D of this HGHG FEL source have been under way since 2000. Currently, a 150MeV S-band electron injector is under construction as the first linac section to produce a high brightness beam.

Z. T. Zhao; Z. M. Dai; X. F. Zhao; D. K. Liu; Q. G. Zhou; D. H. He; Q. K. Jia; S. Y. Chen; J. P. Dai

2004-01-01

406

A high current gain 4H-SiC NPN power bipolar junction transistor  

Microsoft Academic Search

This work reports the development of high power 4H-SiC bipolar junction transistors (BJTs) by using reduced implantation dose for p+ base contact region and annealing in nitric oxide of base-to-emitter junction passivation oxide for 2 hours at 1150°C. The transistor blocks larger than 480 V and conducts 2.1 A (Jc=239 A\\/cm2) at Vce=3.4 V, corresponding to a specific on-resistance (Rsp

Jianhui Zhang; Yanbin Luo; Petre Alexandrov; Leonid Fursin; Jian H. Zhao

2003-01-01

407

A novel high-gain CMOS image sensor using floating N-well\\/gate tied PMOSFET  

Microsoft Academic Search

The development of low power CMOS imaging systems has received a lot of attention. The main obstacle comes from the low responsivity and unscalability of the photo sensor. In this work, we have designed and fabricated a highly responsive photo sensor from a standard MOSIS HP0.8 ?m n-well CMOS process. The photo sensor is obtained by connecting the n-well with

Weiquan Zhang; Mansun Chan; P. K. Ko

1998-01-01

408

The high gain light water breeder reactor with a uranium-plutonium cycle  

Microsoft Academic Search

In the design concept presented, two seed-blanket cores are utilized, a prebreeder and a breeder. The prebreeder core is fueled with plutonium obtained from standard LWR spent fuel and generates plutonium with a high isotopic content of ²⁴°Pu and ²⁴¹Pu, which is used to fuel the breeder core. The initial fissile fuel for a 950-MW(electric) prebreeder is between 3000 and

A. Radkowsky; Z. Shayer

1988-01-01

409

A low noise, high gain Q-band monolithic HEMT receiver  

Microsoft Academic Search

A fully integrated MMIC receiver for Q-band was designed and fabricated using a 0.2 ?m pseudomorphic InGaAs HEMT technology process. This incorporates 3 microcells into a single macrocell. It contains a front end LNA which consists of a four stage balanced HEMT amplifier, a double-balanced HEMT diode mixer, and a 2 stage HEMT IF amplifier. This forms a highly compact

M. V. Aust; B. Alien; G. S. Dow; R. Kasody; M. Biedenbender; N. Wang

1994-01-01

410

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

SciTech Connect

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. 11 refs., 4 figs.

Harris, D.B.; Sullivan, J.A.; Figueiro, J.F.; Cartwright, D.C.; McDonald, T.E.; Hauer, A.A.; Coggeshall, S.V.; Younger, S.M.

1990-01-01

411

Reducing DAC noise to sub-millivolt level in an effort to lock a high gain Fabry-Perot cavity  

NASA Astrophysics Data System (ADS)

Several pending experiments at JLAB Hall A require Compton polarimetry at a higher precision than currently obtainable in the hall, requiring ˜1% error electron polarization measurements. As the frequency of light scattered from the electron beam is increased, the longitudinal asymmetry is decreased as understood within the framework of QED, lowering experimental error. The goal of the project is to create a cavity that resonates with more power and at a higher frequency than the currently implemented setup. Obtaining a PDH-locked, high gain Fabry-Perot cavity that resonates at 1.5 kW of green (532 nm) laser is desired. To combat mechanical fluctuations of the cavity at atomic scales, the feedback loop used tunes the frequency of the input laser. Many upgrades to our hardware and software are required to lock the cavity over long time periods. To this effect, a digital-to-analog converter upgrade was performed to implement a 16-bit DAC setup over the current 12-bit DACs to reduce the effect of bit-noise, which currently rivals the bandwidth of the high-gain cavity. The reduction of noise to a level well within the cavity's bandwidth should allow a more stable lock of the cavity.

Lee, Lawrence

2008-10-01

412

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

PubMed

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 (13)C-(13)C correlation spectra. We demonstrate on model compounds and on 1-73-(U-(13)C,(15)N)/74-108-(U-(15)N) 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 (13)C-(13)C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

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

2014-06-01

413

High gain CMOS image sensor design and fabrication on SOI and bulk technology  

NASA Astrophysics Data System (ADS)

The CMOS imager is now competing with the CCD imager, which still dominates the electronic imaging market. By taking advantage of the mature CMOS technology, the CMOS imager can integrate AID converters, digital signal processing (DSP) and timing control circuits on the same chip. This low cost and high-density integration solution to the image capture is the strong driving force in industry. Silicon on insulator (SOI) is considered as the coming mainstream technology. It challenges the current bulk CMOS technology because of its reduced power consumption, high speed, radiation hardness etc. Moving the CMOS imager from the bulk to the SOI substrate will benefit from these intrinsic advantages. In addition, the blooming and the cross-talk between the pixels of the sensor array can be ideally eliminated, unlike those on the bulk technology. Though there are many advantages to integrate CMOS imager on SOI, the problem is that the top silicon film is very thin, such as 2000Å. Many photons can just pass through this layer without being absorbed. A good photo-detector on SOI is critical to integrate SOI CMOS imagers. In this thesis, several methods to make photo-detectors on SOI substrate are investigated. A floating gate MOSFET on SOI substrate, operating in its lateral bipolar mode, is photon sensitive. One step further, the SOI MOSFET gate and body can be tied together. The positive feedback between the body and gate enables this device have a high responsivity. A similar device can be found on the bulk CMOS technology: the gate-well tied PMOSFET. A 32 x 32 CMOS imager is designed and characterized using such a device as the light-sensing element. I also proposed the idea of building hybrid active pixels on SOI substrate. Such devices are fabricated and characterized. The work here represents my contribution on the CMOS imager, especially moving the CMOS imager onto the SOI substrate.

Zhang, Weiquan

2000-12-01

414

The Shanghai high-gain harmonic generation DUV free-electron laser  

NASA Astrophysics Data System (ADS)

The Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) is an HGHG FEL facility designed for generating coherent output with wavelength down to 88 nm. The design and the relevant R&D of this HGHG FEL source have been under way since 2000. Currently, a 150 MeV S-band electron injector is under construction as the first linac section to produce a high brightness beam. The design study and the present R&D status of the SDUV-FEL have been presented in this paper.

Zhao, Z. T.; Dai, Z. M.; Zhao, X. F.; Liu, D. K.; Zhou, Q. G.; He, D. H.; Jia, Q. K.; Chen, S. Y.; Dai, J. P.

2004-08-01

415

High frequency of large spontaneous deletions of DNA in tumor-derived CHEF cells.  

PubMed

Spontaneous mutations arising at the HPRT locus were examined in 126 mutants recovered from a series of six CHEF-derived cell lines. Altered restriction fragment patterns were characterized by Southern blot hybridization, and gene expression by RNA blot hybridization. Point mutants and gene-expression mutants predominated in the control (nontumorigenic) 18-1D-3 cell line and in two tumor-derived lines, one of which (16-2 Tuk 4) displayed a mutator phenotype. In the other three lines, the majority of mutants had large partial or whole gene deletions. These results suggest that mutant enzymes in DNA replication or repair play an important role in neoplastic progression by causing extensive deletions in DNA, including excision of genes that encode tumor-suppressor functions, and deletion of regulatory sequences in protooncogenes. PMID:2928335

Kaden, D A; Bardwell, L; Newmark, P; Anisowicz, A; Skopek, T R; Sager, R

1989-04-01

416

On the long-memory filtering gain in optical high-order QAM transmission systems.  

PubMed

In this paper, we verify the effectiveness of the last-stage long memory filter (LMF) in mitigating the long-memory response (LMR) of hardware, i.e. the transmitter and receiver. Based on the experimental results, we draw the following conclusions: 1) LMF can effectively mitigate the LMR impact, such as transmitter reflections, and its efficiency is more significant for high-order QAM signals. 2) Using LMF, a partially-correlated pattern exhibits similar performance to that of an uncorrelated pattern both in back-to-back and after 320-km standard single mode fiber (SSMF) transmission. Moreover, a simple solution to the computational complexity of LMF, effective-tap (ET) LMF, is proposed and demonstrated. PMID:23669958

Peng, Wei-Ren; Takahashi, Hidenori; Tsuritani, Takehiro; Morita, Itsuro

2013-05-01

417

Caffeine prevents weight gain and cognitive impairment caused by a high-fat diet while elevating hippocampal BDNF.  

PubMed

Obesity, high-fat diets, and subsequent type 2 diabetes (T2DM) are associated with cognitive impairment. Moreover, T2DM increases the risk of Alzheimer's disease (AD) and leads to abnormal elevation of brain beta-amyloid levels, one of the hallmarks of AD. The psychoactive alkaloid caffeine has been shown to have therapeutic potential in AD but the central impact of caffeine has not been well-studied in the context of a high-fat diet. Here we investigated the impact of caffeine administration on metabolism and cognitive performance, both in control rats and in rats placed on a high-fat diet. The effects of caffeine were significant: caffeine both (i) prevented the weight-gain associated with the high-fat diet and (ii) prevented cognitive impairment. Caffeine did not alter hippocampal metabolism or insulin signaling, likely because the high-fat-fed animals did not develop full-blown diabetes; however, caffeine did prevent or reverse a decrease in hippocampal brain-derived neurotrophic factor (BDNF) seen in high-fat-fed animals. These data confirm that caffeine may serve as a neuroprotective agent against cognitive impairment caused by obesity and/or a high-fat diet. Increased hippocampal BDNF following caffeine administration could explain, at least in part, the effects of caffeine on cognition and metabolism. PMID:23220362

Moy, Gregory A; McNay, Ewan C

2013-01-17

418

Imaging at soft X-ray wavelengths with high-gain microchannel plate detector systems  

NASA Astrophysics Data System (ADS)

Multianode microchannel array (MAMA) detector systems with formats of 256 x 1024 pixels and active areas of 6 x 26 mm are now under evaluation at visible, UV and soft X-ray wavelengths. Very-large-format versions of the MAMA detectors with formats of 2048 x 2048 pixels and active areas of 52 x 52 mm are under development for use in the NASA Goddard Space Telescope Imaging Spectrograph (STIS). Open-structure versions of these detectors with Cs I photocathodes can provide a high-resolution imaging capability at EUV and soft X-ray wavelengths and can deliver a maximum count rate from each array in excess of 10 to the 6th counts/s. In addition, these detector systems have the unique capability to determine the arrival time of a detected photon to an accuracy of 100 ns or better. The construction, mode of operation, and performance characteristics of the MAMA detectors are described, and the program for the development of the very-large-format detectors is outlined.

Timothy, J. Gethyn

1986-01-01

419

Comparative study of nonideal beam effects in high gain harmonic generation and self-seeded free electron lasers  

NASA Astrophysics Data System (ADS)

In this paper we investigate and compare the properties of two narrow-bandwidth free-electron laser (FEL) schemes, one using self-seeding and the other high gain harmonic generation (HGHG). The two systems have been thoroughly studied analytically and numerically in the past. The aim of this work is to compare their performances when the FEL is driven by an electron beam with nonideal properties, thus including effects such as shot-to-shot energy fluctuations and nonlinear energy chirp. In both cases nonlinearities produce a bandwidth larger than the Fourier transform limited value. However, our analysis indicates that, for approximately the same output power levels, the self-seeding scheme is less affected than the HGHG scheme by quadratic energy chirps in the electron beam longitudinal phase space. This is confirmed by a specific numerical example corresponding to SPARX parameters where the electron beam was optimized to minimize the FEL gain length. The work has been carried out with the aid of the time dependent FEL codes GENESIS 1.3 (3D) and PERSEO (1D).

Marinelli, Agostino; Pellegrini, Claudio; Giannessi, Luca; Reiche, Sven

2010-07-01

420

College Expectations in High School Mitigate Weight Gain over Early Adulthood: Findings from a National Study of American Youth  

PubMed Central

Objective Research conducted on school-based interventions suggests that school connectedness protects against a variety of risk behaviors, including substance abuse, delinquency and sedentary behavior. We extend this line of research by examining the link between college expectations and early adult weight gain using nationally representative panel data from thirty cohorts of American high school seniors followed prospectively to age 30 in the Monitoring the Future Study (1986–2009). Design and Methods Growth mixture models identified two latent classes of trajectories of body mass index (BMI) from age 19 to 30: a persistently overweight class (BMI?25) and a second class exhibiting more moderate growth in BMI to age 30. Results Compared to those who did not expect to graduate from college, students fully expecting to graduate from college had 34% lower odds of being in the persistently overweight class (adjusted odds ratio = 0.66, 95% confidence interval = 0.54, 0.81), controlling for academic performance and socioeconomic status. Conclusions Successful prevention of obesity early in the life course is based on a multifactorial approach incorporating strategies that address the contexts in which adolescents are embedded. The school setting may be one avenue where successful educational attachment could have positive consequences for subsequent weight gain in early adulthood.

Clarke, Philippa J.; O'Malley, Patrick M.; Schulenberg, John E.; Lee, Hedwig; Colabianchi, Natalie; Johnston, Lloyd D.

2012-01-01

421

Impact of radiator length in the emitted power for a high gain harmonic generation free-electron laser  

NASA Astrophysics Data System (ADS)

We present a numerical study that characterizes the dependence on the radiator length of the output power produced by a free-electron laser (FEL) operated in the high gain harmonic generation (HGHG) configuration. Using the main parameters of the FERMI@Elettra FEL, numerical simulations of the FEL process have been performed for different lengths of the radiator. Our results show that in the case of HGHG the achievable output power has a dependence on the radiator length that is linear. The impact of the electron beam parameters on the achievable maximum power vs radiator length dependence is also studied. A normalization of the results to the FEL saturation power and to the FEL gain length shows that this dependence can be expressed by a universal linear equation that, in some conditions, is independent on the electron beam current and brightness. The reported results could be useful for the design of future FELs based on the HGHG scheme and could be used for a quick estimate of the best undulator length.

Allaria, Enrico

2013-03-01

422

Self-amplified spontaneous emission for a single pass free-electron laser  

NASA Astrophysics Data System (ADS)

SPARC (acronym of “Sorgente Pulsata ed Amplificata di Radiazione Coerente”, i.e. Pulsed and Amplified Source of Coherent Radiation) is a single pass free-electron laser designed to obtain high gain amplification at a radiation wavelength of 500 nm. Self-amplified spontaneous emission has been observed driving the amplifier with the high-brightness beam of the SPARC linac. We report measurements of energy, spectra, and exponential gain. Experimental results are compared with simulations from several numerical codes.

Giannessi, L.; Alesini, D.; Antici, P.; Bacci, A.; Bellaveglia, M.; Boni, R.; Boscolo, M.; Briquez, F.; Castellano, M.; Catani, L.; Chiadroni, E.; Cianchi, A.; Ciocci, F.; Clozza, A.; Couprie, M. E.; Cultrera, L.; Dattoli, G.; Del Franco, M.; Dipace, A.; di Pirro, G.; Doria, A.; Drago, A.; Fawley, W. M.; Ferrario, M.; Ficcadenti, L.; Filippetto, D.; Frassetto, F.; Freund, H. P.; Fusco, V.; Gallerano, G.; Gallo, A.; Gatti, G.; Ghigo, A.; Giovenale, E.; Marinelli, A.; Labat, M.; Marchetti, B.; Marcus, G.; Marrelli, C.; Mattioli, M.; Migliorati, M.; Moreno, M.; Mostacci, A.; Orlandi, G.; Pace, E.; Palumbo, L.; Petralia, A.; Petrarca, M.; Petrillo, V.; Poletto, L.; Quattromini, M.; Rau, J. V.; Reiche, S.; Ronsivalle, C.; Rosenzweig, J.; Rossi, A. R.; Rossi Albertini, V.; Sabia, E.; Serafini, L.; Serluca, M.; Spassovsky, I.; Spataro, B.; Surrenti, V.; Vaccarezza, C.; Vescovi, M.; Vicario, C.

2011-06-01

423

The pronociceptive dorsal reticular nucleus contains mostly tonic neurons and shows a high prevalence of spontaneous activity in block preparation.  

PubMed

Despite the importance and significant clinical impact of understanding information processing in the nociceptive system, the functional properties of neurons in many parts of this system are still unknown. In this work we performed whole cell patch-clamp recording in rat brain stem blocks to characterize the electrophysiological properties of neurons in the dorsal reticular nucleus (DRt), a region known to be involved in pronociceptive modulation. We also compared properties of DRt neurons with those in the adjacent parvicellular reticular nucleus and in neighboring regions outside the reticular formation. We found that neurons in the DRt and parvicellular reticular nucleus had similar electrophysiological properties and exhibited mostly toniclike firing patterns, whereas neurons outside the reticular formation showed a larger diversity of firing patterns. Interestingly, more than one-half of the neurons also showed spontaneous activity. While the general view of the reticular formation, being a loosely associated mesh of groups of neurons with diverse function, and earlier reports suggests more electrophysiological heterogeneity, we showed that this is indeed not the case. Our results indicate that functional difference of neurons in the reticular formation may mostly be determined by their connectivity profiles and not by their intrinsic electrophysiological properties. The dominance of tonic neurons in the DRt supports previous conclusions that these neurons encode stimulus intensity through their firing frequency, while the high prevalence of spontaneous activity most likely shapes nociceptive modulation by this brain stem region. PMID:24431401

Sousa, Mafalda; Szucs, Peter; Lima, Deolinda; Aguiar, Paulo

2014-04-01

424

Escherichia coli DNA polymerase III is responsible for the high level of spontaneous mutations in mutT strains  

PubMed Central

Reactive oxygen species induce oxidative damage in DNA precursors, i.e. dNTPs, leading to point mutations upon incorporation. Escherichia coli mutT strains, deficient in the activity hydrolysing 8-oxo-7,8-dihydro-2?-deoxyguanosine 5?-triphosphate (8-oxo-dGTP), display more than a 100-fold higher spontaneous mutation frequency over the wild-type strain. 8-oxo-dGTP induces A to C transversions when misincorporated opposite template A. Here, we report that DNA pol III incorporates 8-oxo-dGTP ? 20 times more efficiently opposite template A compared with template C. Single, double or triple deletions of pol I, pol II, pol IV or pol V had modest effects on the mutT mutator phenotype. Only the deletion of all four polymerases led to a 70% reduction of the mutator phenotype. While pol III may account for nearly all 8-oxo-dGTP incorporation opposite template A, it only extends ? 30% of them, the remaining 70% being extended by the combined action of pol I, pol II, pol IV or pol V. The unique property of pol III, a C-family DNA polymerase present only in eubacteria, to preferentially incorporate 8-oxo-dGTP opposite template A during replication might explain the high spontaneous mutation frequency in E. coli mutT compared with the mammalian counterparts lacking the 8-oxo-dGTP hydrolysing activities.

Yamada, Masami; Shimizu, Masatomi; Katafuchi, Atsushi; Gruz, Petr; Fujii, Shingo; Usui, Yukio; Fuchs, Robert P; Nohmi, Takehiko

2012-01-01

425

High Spontaneous Mutation Rate in the Hyperthermophilic Archaeon Sulfolobus solfataricus Is Mediated by Transposable Elements†  

PubMed Central

We have isolated uracil-auxotrophic mutants of the hyperthermophilic archaeon Sulfolobus solfataricus in order to explore the genomic stability and mutational frequencies of this organism and to identify complementable recipients for a selectable genetic transformation system. Positive selection of spontaneous mutants resistant to 5-fluoroorotate yielded uracil auxotrophs with frequencies of between 10?4 and 10?5 per sensitive, viable cell. Four different, nonhomologous insertion sequences (ISs) were identified at different positions within the chromosomal pyrEF locus of these mutants. They ranged in size from 1,058 to 1,439 bp and possessed properties typical of known transposable elements, i.e., terminal inverted repeats, flanking duplicated target sequences, and putative transposase genes encoding motifs that are indicative of the IS4-IS5 IS element families. Between 12 and 25 copies of each IS element were found in chromosomal DNAs by Southern analyses. While characteristic fingerprint patterns created by IS element-specific probes were observed with genomic DNA of different S. solfataricus strains, no homologous sequences were identified in DNA of other well-characterized strains of the order Sulfolobales.

Martusewitsch, Erika; Sensen, Christoph W.; Schleper, Christa

2000-01-01

426

Modeling and output tracking of transverse flux permanent magnet machines using high gain observer and RBF neural network.  

PubMed

This paper deals with modeling and adaptive output tracking of a transverse flux permanent magnet machine as a nonlinear system with unknown nonlinearities by utilizing high gain observer and radial basis function networks. The proposed model is developed based on computing the permeance between rotor and stator using quasiflux tubes. Based on this model, the techniques of feedback linearization and Hinfinity control are used to design an adaptive control law for compensating the unknown nonlinear parts, such as the effect of cogging torque, as a disturbance is decreased onto the rotor angle and angular velocity tracking performances. Finally, the capability of the proposed method in tracking both the angle and the angular velocity is shown in the simulation results. PMID:16294772

Karimi, H R; Babazadeh, A

2005-10-01

427

Transverse-to-longitudinal emittance exchange to improve performance of high-gain free-electron lasers.  

SciTech Connect

The ability to generate small transverse emittance is perhaps the main limiting factor for the performance of high-gain x-ray free-electron lasers (FELs). Noting that beams from an rf photocathode gun can have energy spread much smaller than required for efficient FEL interaction, we present a method to produce normalized transverse emittance at or below about 0.1 {micro}m, which will lead to a significantly shorter length undulator as well as a lower electron beam energy for an x-ray FEL project. The beam manipulation consists of producing an unequal partition of the initially equal emittances into two dissimilar emittances by a flat-beam technique and exchanging the larger transverse emittance with a smaller longitudinal emittance. We study various issues involved in the manipulation. In particular, a new emittance exchange optics we found enables an exact emittance exchange necessary for this scheme.

Emma, P.; Huang, Z.; Kim, K.-J.; Piot, P.; Accelerator Systems Division (APS); SLAC; Northern Illinois Univ.; FNAL

2006-10-01

428

Parallel array of YBa2Cu3O7-? superconducting Josephson vortex-flow transistors with high current gains  

NASA Astrophysics Data System (ADS)

We have developed a Josephson vortex-flow transistor based on a parallel array of 440 YBa2Cu3O7-? bicrystal grain boundary Josephson junctions. The array's critical current Ic was measured as a function of the control current Ictrl through a control line that is inductively coupled to the array. The device has a highly asymmetric Ic(Ictrl) curve with several regions where a switching behaviour is observed characterized by a maximum current gain gmax = ?Ic/?Ictrl of 19 and a significant dynamic range of 20 ?A at 77 K. In the range 4.7-92 K gmax versus temperature is non-monotonic with a maximum recorded at 77 K.

Chesca, Boris; John, Daniel; Kemp, Matthew; Brown, Jeffrey; Mellor, Christopher

2013-08-01

429

Highly entangled photons and rapidly responding polarization qubit phase gates in a room-temperature active Raman gain medium  

SciTech Connect

We present a scheme for obtaining entangled photons and quantum phase gates in a room-temperature four-state tripod-type atomic system with two-mode active Raman gain (ARG). We analyze the linear and nonlinear optical responses of this ARG system and show that the scheme is fundamentally different from those based on electromagnetically induced transparency and hence can avoid significant probe-field absorption as well as a temperature-related Doppler effect. We demonstrate that highly entangled photon pairs can be produced and rapidly responding polarization qubit phase gates can be constructed based on the unique features of the enhanced cross-phase-modulation and superluminal probe-field propagation of the system.

Hang Chao [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Centro de Fisica Teorica e Computacional, Universidade de Lisbon, Complex Interdisciplinary, Avenida Professor Gama Pinto 2, Lisbon P-1649-003 (Portugal); Huang Guoxiang [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Institute of Nonlinear Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China)

2010-11-15

430

Flexible high gain complementary inverter using n-ZnO and p-pentacene channels on polyethersulfone substrate  

NASA Astrophysics Data System (ADS)

We report on the fabrication of complementary inverters that have ZnO and pentacene as n-type and p-type channels on a polyethersulfone substrate operating under 7 V. Patterned Al and AlOx thin film were deposited at room temperature on the plastic as a common gate electrode and dielectric, respectively. After initial gate instability between ZnO channel and AlOx dielectric was controlled, our n-type thin-film transistors (TFTs) displayed quite a similar drain current level to that of p-type TFTs. Our flexible complementary device showed much high voltage gain of ~100 even under a bent condition (56 mm radius of curvature). Our complementary inverter also demonstrates a promising dynamic behavior of ~20 ms.

Oh, Min Suk; Choi, Wonjun; Lee, Kimoon; Hwang, D. K.; Im, Seongil

2008-07-01

431

Adaptive fuzzy backstepping output feedback control for a class of MIMO time-delay nonlinear systems based on high-gain observer  

Microsoft Academic Search

In this paper, an adaptive fuzzy backstepping output feedback control approach is developed for a class of multiinput and\\u000a multioutput (MIMO) nonlinear systems with time delays and immeasurable states. Fuzzy logic systems are employed to approximate\\u000a the unknown nonlinear functions, and an adaptive fuzzy high-gain observer is developed to estimate the unmeasured states.\\u000a Using the designed high-gain observer, and combining

Yongming Li; Chang’e Ren; Shaocheng Tong

432

Simultaneous bilateral spontaneous pneumothorax following high-dose chemotherapy and bone marrow transplantation for mantle cell lymphoma without evidence of pulmonary disease.  

PubMed

Simultaneous bilateral spontaneous pneumothorax (SBSP) during high-dose chemotherapy has been described in patients with pulmonary involvement by malignancy, including sarcoma, trophoblastic tumor, non-seminomatous testicular cancer, and non-Hodgkin lymphoma. We present a case of SBSP developing in a patient 11 days after a high-dose chemotherapy preparative regimen and stem cell transplantation without underlying pulmonary disease or evidence of lung lesions. It is important to recognize spontaneous pneumothorax as a potential complication of high-dose chemotherapy, especially in patients with known pulmonary lesions. PMID:20589405

Schneider, Ashley E; Talmon, Geoffrey A

2010-12-01

433

Topiramate reduces abnormally high extracellular levels of glutamate and aspartate in the hippocampus of spontaneously epileptic rats (SER).  

PubMed

The spontaneously epileptic rat (SER), a double mutant, manifests both tonic and absence-like seizures. The effect of topiramate, a novel antiepileptic drug, on the extracellular levels of excitatory amino acids (EAA) in the hippocampus of SER was investigated using in vivo microdialysis. The basal levels of glutamate and aspartate in dialysates of hippocampus in SER were 2- to 3-fold higher than those in normal Wistar rats. Both the dose-response relationship and the time course of the suppression of tonic seizures by topiramate were similar to the attenuation of glutamate level in SER. Topiramate (40 mg/kg i.p.) significantly (P < 0.05) reduced both glutamate and aspartate levels in SER while showing no effect on normal Wistar rats. These findings suggest that topiramate reduces abnormally high extracellular levels of glutamate and aspartate in the hippocampus of SER. This effect may, at least in part, be related to the anticonvulsant activity of topiramate. PMID:8913326

Kanda, T; Kurokawa, M; Tamura, S; Nakamura, J; Ishii, A; Kuwana, Y; Serikawa, T; Yamada, J; Ishihara, K; Sasa, M

1996-01-01

434

A highly efficient broadband picosecond pump high-gain OPCPA system for Ti-sapphire seed pulses; an ideal seed for high-contrast, large-energy/aperture CPA laser system: Vulcan  

NASA Astrophysics Data System (ADS)

The achievement of high contrast, high efficiency OPCPA systems has been a long established goal. We achieve close to ~20% conversion in a picosecond OPCPA system. This is now the standard seed for our petawatt pre-amplifier laser system which had a conventional 108 nanosecond gain. We thereby eliminate the need to the first nanosecond gain stage. We achieve a contrast at the 10-8 level when using the petawatt system in this configuration. We have also demonstrated a second stage of picosecond amplification with an extra gain of >2, maintaining the bandwidth and transform limited nature of the pulses, providing the potential for further improvements.

Shaikh, W.; Musgrave, I. O.; Galimberti, M.; Boyle, A.

2012-02-01

435

High-Gain, Polarization-Perserving, Yb-Doped Fiber Amplifier for Low-Duty-Cycle Pulse Amplification  

SciTech Connect

An alignment-free, dual-pass, ytterbium-doped fiber amplifier with 25-dB gain and -44 dB noise floor is demonstrated for amplifying linearly polarized optical pulses with low duty cycle at a wavelength 23 nm off the gain peak.

Marciante, J.R.; Zuegel, J.D.

2005-09-30

436

High-gain, polarization-preserving, Yb-doped fiber amplifier for low-duty-cycle pulse amplification  

Microsoft Academic Search

An alignment-free, dual-pass, ytterbium-doped fiber amplifier with 25-dB gain and -44 dB noise floor is demonstrated for amplifying linearly polarized optical pulses with low duty cycle at a wavelength 23 nm off the gain peak.

J. R. Marciante; J. D. Zuegel

2005-01-01

437

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

Microsoft Academic Search

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

Venu Gopinathan; Maurice Tarsia; Davy Choi

1999-01-01

438

High-Gain, Polarization-Preserving, Yb-Doped Fiber Amplifier for Low-Duty-Cycle Pulse Amplification  

SciTech Connect

Amplified spontaneous emission (ASE) suppression techniques were utilized to fabricate a double-pass, Yb-doped amplifier with the noise properties of a single-pass amplifier. Simulations based on a rate equation model were used to analyze the ASE and the effectiveness of the suppression techniques.

Marciante, J.R.; Zuegel, J.D.

2006-08-22

439

High-Gain, Polarization-Preserving, Yb-Doped Fiber Amplifier for Low-Duty-Cycle Pulse Amplification  

Microsoft Academic Search

Amplified spontaneous emission (ASE) suppression techniques were utilized to fabricate a double-pass, Yb-doped amplifier with the noise properties of a single-pass amplifier. Simulations based on a rate equation model were used to analyze the ASE and the effectiveness of the suppression techniques.

J. R. Marciante; J. D. Zuegel

2006-01-01

440

Self-amplified spontaneous emission for short wavelength coherent radiation  

SciTech Connect

We review the recent progress in our understanding of the self-amplified spontaneous emission (SASE), emphasizing the application to short wavelength generation. Simple formulae are given for the start-up, exponential gain and the saturation of SASE. Accelerator technologies producing high brightness electron beams required for short wavelength SASE are discussed. An example utilizing electron beams from a photocathode-linac system to produce 4nm SASE in the multigigawatt range is presented.

Kim, K.J.; Xie, M.

1992-09-01

441

Highly-stable and efficient polymer solar cells incorporating nanoscale buffer layers induced by spontaneous vertical phase separation  

Microsoft Academic Search

A nanoscale interlayer formed through spontaneous vertical phase separation enhances the efficiency and stability of polymer solar cells. Poly(ethylene glycol) molecules blended into the photoactive layer spontaneously migrate to the surface of the polymer blend to form the interfacial buffer, thereby reducing the contact resistance after undergoing chemical reactions with the Al atoms of the cathode. The vertical phase separation

Shang-Chieh Chien; Hau-Chih Yang; Fang-Chung Chen

2010-01-01

442

Asymmetric Two-Beam Coupling with High Optical Gain and High Beam Diffraction in External-Electric-Field-Free Polymer Composites  

NASA Astrophysics Data System (ADS)

This paper presents high-performance asymmetric two-beam coupling, beam diffraction and holographic recording in polymeric composites without poling and applying an external electric field. The polymer composites are based on poly(2-(9-carbazoyl)ethyl methacrylate) (PCzEMA) and poly(N-vinyl carbazole) (PVCz) as host matrices with 2,4,7-trinitro-9-fluorenone (TNF) as a sensitizer, four kinds of plasticizer; tricresyl phosphate (TCP), n-butyl benzyl phthalate (BBP), diphenyl phthalate (DPP), and dicyclohexyl phthalate (DCP); and (s)-(-)-1-(4-nitrophenyl)-2-pyrrolidine-methanol (NPP) as a nonlinear optical dye. The gain coefficient and diffraction efficiency increased markedly with increasing TNF and NPP concentrations. The highest net gain coefficient of 101.9 cm-1 with optical gain of 224 cm-1 and absorption coefficient of 122.1 cm-1 was obtained for PVCz/NPP/DDP/TNF (35/20/40/5), and the highest diffraction efficiency of 88% was achieved for PCzEMA/NPP/TCP/TNF (35/30/30/5) and PVCz/NPP/DDP/TNF (35/20/39/6) composites. The BBP plasticizer significantly enhanced the speed of two-beam coupling and diffraction grating formation for both PVCz and PCzEMA composites. Holographic images stored in the polymer composites were clearly read out using a probe beam. The key point for achieving the external-electric-field-free high performance of asymmetric energy transfer and diffraction efficiency is to have a high concentration of TNF (5 or 7 wt%).

Tsutsumi, Naoto; Shimizu, Yusuke

2004-06-01

443

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

PubMed

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

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

2011-07-01

444

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

NASA Astrophysics Data System (ADS)

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 desired. Since Ce:LiCAF has a tunability of 281nm to 315nm, it holds promise for 3-fs pulse generation which are required for seeding TW-class Ce:LiCAF lasers. The pulse-width of the frequency-tripled Ti:sapphire regenerative amplifier was measured to be 210 fs. The seed pulses were then focused into a hollow fiber filled with argon to spectrally broaden the pulses due to self-phase-modulation. The pulses were then compressed to 25 fs by dispersion-compensation. The fourth harmonics of a Nd:YAG laser (266 nm) is an ideal pump source as it falls within the absorption band Ce:LiCAF. We have generated 430 mJ fourth harmonics with a total conversion efficiency of 30.5% using Li2B4O7(LB4) crystals. A Ce:LiCAFdouble-pass power-amplifier was then designed with a peak energy of 98 mJ for a 13 mJ seed pulse and an extraction efficiency of 25%.

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

2006-03-01

445

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

SciTech Connect

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.

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

2009-01-01

446

A High Dynamic Range 100Mhz AGC-Amplifier with a Linear and Temperature Compensated Gain Control  

Microsoft Academic Search

In this paper the control voltage related temperature dependencies of a current deviation based AGC amplifier are studied. A control circuit with linear and temperature compensating gain control is presented

H. Riihihuhta; Kari Halonen; Kari Koli

1994-01-01

447

A sub-1V high-gain two-stage OTA using bulk-driven and positive feedback techniques  

Microsoft Academic Search

This paper presents the design and simulation of a fully differential two-stage operational trans-conductance amplifier (OTA) in a 0.18?m CMOS process with a 0.9V supply voltage. For this purpose, both the bulk-driven and positive feedback techniques are employed. These techniques increase the dc gain about 18.4 dB without any change in the power dissipation, unity-gain bandwidth, phase margin, and other

H. Khameh; H. Shamsi

2010-01-01

448

Two-photon-pumped optical gain in dye-polymer composite materials  

NASA Astrophysics Data System (ADS)

Optical gain with two-photon pumping has been quantitatively characterized in the energy-transfer-coupled dye-polymer composite materials. Using femtosecond transient absorption spectroscopy, we observed frequency up-converted optical amplification in the dye-doped polymer films. Net optical gain coefficient in the polymer films with optimized doping is evaluated to be about 25 cm-1 by the variable-stripe-length measurements, which induces spectral narrowing of emission with linewidth changing from 42 nm to 9 nm. The intrinsic mechanisms for the optical gain in such composite system have been assigned to the amplified spontaneous emission and superfluorescence at relatively low and high excitation regimes, respectively.

Li, Wei; Zhang, Chunfeng; Chen, Qi; Wang, Xiaoyong; Xiao, Min

2012-03-01

449

Green tea decoction improves glucose tolerance and reduces weight gain of rats fed normal and high-fat diet.  

PubMed

Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis. PMID:24656388

Snoussi, Chahira; Ducroc, Robert; Hamdaoui, Mohamed Hédi; Dhaouadi, Karima; Abaidi, Houda; Cluzeaud, Francoise; Nazaret, Corinne; Le Gall, Maude; Bado, André

2014-05-01

450

Measurement and Simulation of Spontaneous Raman Scattering Spectra in High-Pressure, Fuel-Rich H2-Air Flames  

NASA Technical Reports Server (NTRS)

Rotational vibrational spontaneous Raman spectra (SRS) of H2, N2, and H2O have been measured in H2-air flames at pressures up to 30 atm as a first stem towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. A newly developed high-pressure burner facility provides steady, reproducible flames with a high degree of flow precision. 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 future reference standards. The fully resolved Stokes and anti-Stokes shifted SRS spectra were collected in the visible wavelength range (400-700 nm) using pulse-stretched 532 nm excitation and a non-intensified CCD spectrograph with a high-speed shutter. Reasonable temperatures were determined via the intensity distribution of rotational H2 lines at stoichiometry and fuel-rich conditions. Theoretical Raman spectra of H2 were computed using a semi-classical harmonic-oscillator model with recent pressure broadening data and were compared with experimental results. The data and simulation indicated that high-J rotational lines of H2 might interfere with the N2 vibrational Q-branch lines, and this could lead to errors in N2-Raman thermometry based on the line-fitting method. From a comparison of N2 Q-branch spectra in lean H2 low-pressure (1.2 atm) and high-pressure (30 atm) flames, we found no significant line-narrowing or -broadening effects at the current spectrometer resolution of 0.04 nm.

Kojima, Jun; Nguyen, Quang-Viet

2003-01-01

451

Radiation Susceptibility of High Power (>200 mW) Spontaneous Infrared Emitters.  

National Technical Information Service (NTIS)

The effects of neutron and gamma irradiation on high-power (>200 mW) GaAs dome infrared emitters are reported. The threshold radiation levels for degradation of radiated power output, power efficiency, and external quantum efficiency are observed for neut...

R. A. Polimadei S. Share A. S. Epstein G. E. Gowins

1974-01-01

452

High-dose misoprostol used in outpatient management of first trimester spontaneous abortion  

Microsoft Academic Search

Aim: The aim of this study was to evaluate the efficacy and tolerance of a high dose of vaginal misoprostol for outpatient medical management of missed abortion. Methods: Three doses of 400 lg misoprostol were administered intravaginally every 4 h daily, for a maximum period of 3 days, to 108 women with uneventful first trimester pregnancy failure. Results: A total

Stavros Sifakis; Emmanuel Angelakis; Elpida Vardaki; Yvoni Fragouli; Eugenios Koumantakis

2005-01-01

453

Ytterbium-doped large-mode-area photonic crystal fiber amplifier with gain shaping for use at long wavelengths  

NASA Astrophysics Data System (ADS)

A large-mode-area Ytterbium-doped photonic crystal fiber amplifier with efficient suppression of amplified spontaneous emission is presented. The fiber cladding consists of a hexagonal lattice of air holes, where three rows are replaced with circular high-index inclusions. Seven missing air holes define the large-mode-area core. Light confinement is achieved by combined index and bandgap guiding, which allows for single-mode operation and distributed spectral filtering of amplified spontaneous. The fiber properties give control of the gain shape and are ideal for amplification in the long wavelength regime of the Ytterbium gain spectrum above 1100 nm.

Petersen, Sidsel R.; Alkeskjold, Thomas T.; Poli, Federica; Coscelli, Enrico; Jørgensen, Mette M.; Laurila, Marko; Lægsgaard, Jesper; Broeng, Jes

2012-02-01

454

Do High-Functioning People with Autism Spectrum Disorder Spontaneously Use Event Knowledge to Selectively Attend to and Remember Context-Relevant Aspects in Scenes?  

ERIC Educational Resources Information Center

This study combined an event schema approach with top-down processing perspectives to investigate whether high-functioning children and adults with autism spectrum disorder (ASD) spontaneously attend to and remember context-relevant aspects of scenes. Participants read one story of story-pairs (e.g., burglary or tea party). They then inspected a…

Loth, Eva; Gomez, Juan Carlos; Happe, Francesca

2011-01-01

455

Severe obesity, gestational weight gain, and adverse birth outcomes123  

PubMed Central

Background: The 2009 Institute of Medicine (IOM) Committee to Reevaluate Gestational Weight Gain Guidelines concluded that there were too few data to inform weight-gain guidelines by obesity severity. Therefore, the committee recommended a single range, 5–9 kg at term, for all obese women. Objective: We explored associations between gestational weight gain and small-for-gestational-age (SGA) births, large-for-gestational-age (LGA) births, spontaneous preterm births (sPTBs), and medically indicated preterm births (iPTBs) among obese women who were stratified by severity of obesity. Design: We studied a cohort of singleton, live-born infants without congenital anomalies born to obesity class 1 (prepregnancy body mass index [BMI (in kg/m2)]: 30–34.9; n = 3254), class 2 (BMI: 35–39.9; n = 1451), and class 3 (BMI: ?40; n = 845) mothers. We defined the adequacy of gestational weight gain as the ratio of observed weight gain to IOM-recommended gestational weight gain. Results: The prevalence of excessive gestational weight gain declined, and weight loss increased, as obesity became more severe. Generally, weight loss was associated with an elevated risk of SGA, iPTB, and sPTB, and a high weight gain tended to increase the risk of LGA and iPTB. Weight gains associated with probabilities of SGA and LGA of ?10% and a minimal risk of iPTB and sPTB were as follows: 9.1–13.5 kg (obesity class 1), 5.0–9 kg (obesity class 2), 2.2 to <5.0 kg (obesity class 3 white women), and <2.2 kg (obesity class 3 black women). Conclusion: These data suggest that the range of gestational weight gain to balance risks of SGA, LGA, sPTB, and iPTB may vary by severity of obesity.

Bodnar, Lisa M; Siega-Riz, Anna Maria; Simhan, Hyagriv N; Himes, Katherine P; Abrams, Barbara

2010-01-01

456

Clinical Relevance of Gain-Of-Function Mutations of p53 in High-Grade Serous Ovarian Carcinoma  

PubMed Central

Purpose Inactivation of TP53, which occurs predominantly by missense mutations in exons 4–9, is a major genetic alteration in a subset of human cancer. In spite of growing evidence that gain-of-function (GOF) mutations of p53 also have oncogenic activity, little is known about the clinical relevance of these mutations. Methods The clinicopathological features of high-grade serous ovarian carcinoma (HGS-OvCa) patients with GOF p53 mutations were evaluated according to a comprehensive somatic mutation profile comprised of whole exome sequencing, mRNA expression, and protein expression profiles obtained from the Cancer Genome Atlas (TCGA). Results Patients with a mutant p53 protein (mutp53) with a GOF mutation showed higher p53 mRNA and protein expression levels than patients with p53 mutation with no evidence of GOF (NE-GOF). GOF mutations were more likely to occur within mutational hotspots, and at CpG sites, and resulted in mutp53 with higher functional severity (FS) scores. Clinically, patients with GOF mutations showed a higher frequency of platinum resistance (22/58, 37.9%) than patients with NE-GOF mutations (12/56, 21.4%) (p=0.054). Furthermore, patients with GOF mutations were more likely to develop distant metastasis (36/55, 65.5%) than local recurrence (19/55, 34.5%), whereas patients with NE-GOF mutations showed a higher frequency of locoregional recurrence (26/47, 55.3%) than distant metastasis (21/47, 44.7%) (p=0.035). There were no differences in overall or progression-free survival between patients with GOF or NE-GOF mutp53. Conclusion This study demonstrates that patient with GOF mutp53 is characterized by a greater likelihood of platinum treatment resistance and distant metastatic properties in HGS-OvCa.

Kim, Kyu-Rae; Sohn, Insuk; Sung, Chang Ohk

2013-01-01

457

The X-Target: A novel high gain target with single-sided heavy-ion beam illumination  

NASA Astrophysics Data System (ADS)

A new inertial-fusion target configuration, the X-target, using one-sided heavy ion axial illumination has been explored [1]. It takes advantage of the unique energy deposition properties of heavy ion beams that have a classical, long penetration range. This class of target uses heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an ``X''. X-targets that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT are capable of assembling fuel areal densities ˜2 g/cm^2 using two MJ-scale annular beams to implode quasi-spherically the target to peak DT densities ˜100 g/cm^3. A 3MJ fast-ignition solid ion beam heats the fuel to thermonuclear temperatures in ˜200 ps to start the burn propagation, obtaining gains of ˜300. The main concern for the X-target is the amount of high-Z atomic mixing at the ignition zone produced by hydro-instabilities, which, if large enough, could cool the fuel during the ignition process and prevent the propagation of the fusion burn. Analytic estimates and implosion calculations using the radiation hydrodynamics code HYDRA in 2D (RZ), at typical Eulerian mesh resolutions of a few microns, have shown that for the relatively low implosion velocities, low stagnation fuel densities, and low quasi-spherical fuel convergence ratios of the X-target, these hydro-instabilities do not have a large effect on the burning process. These preliminary studies need to be extended by further hydrodynamic calculations using finer resolution, complemented with turbulent mix modeling and validated by experiments, to ascertain the stability of the X-target design. We will present the current status of the X-target. [4pt] [1] E. Henestroza and B. G. Logan, Phys. Plasmas 19, 072706 (2012)

Henestroza, Enrique

2012-10-01

458

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

SciTech Connect

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}}.

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

459

A low-carbohydrate/high-fat diet reduces blood pressure in spontaneously hypertensive rats without deleterious changes in insulin resistance  

PubMed Central

Previous studies reported that diets high in simple carbohydrates could increase blood pressure in rodents. We hypothesized that the converse, a low-carbohydrate/high-fat diet, might reduce blood pressure. Six-week-old spontaneously hypertensive rats (SHR; n = 54) and Wistar-Kyoto rats (WKY; n = 53, normotensive control) were fed either a control diet (C; 10% fat, 70% carbohydrate, 20% protein) or a low-carbohydrate/high-fat diet (HF; 20% carbohydrate, 60% fat, 20% protein). After 10 wk, SHR-HF had lower (P < 0.05) mean arterial pressure than SHR-C (148 ± 3 vs. 159 ± 3 mmHg) but a similar degree of cardiac hypertrophy (33.4 ± 0.4 vs. 33.1 ± 0.4 heart weight/tibia length, mg/mm). Mesenteric arteries and the entire aorta were used to assess vascular function and endothelial nitric oxide synthase (eNOS) signaling, respectively. Endothelium-dependent (acetylcholine) relaxation of mesenteric arteries was improved (P < 0.05) in SHR-HF vs. SHR-C, whereas contraction (potassium chloride, phenylephrine) was reduced (P < 0.05). Phosphorylation of eNOSSer1177 increased (P < 0.05) in arteries from SHR-HF vs. SHR-C. Plasma glucose, insulin, and homoeostatic model of insulin assessment were lower (P < 0.05) in SHR-HF vs. SHR-C, whereas peripheral insulin sensitivity (insulin tolerance test) was similar. After a 10-h fast, insulin stimulation (2 U/kg ip) increased (P < 0.05) phosphorylation of AktSer473 and S6 in heart and gastrocnemius similarly in SHR-C vs. SHR-HF. In conclusion, a low-carbohydrate/high-fat diet reduced blood pressure and improved arterial function in SHR without producing signs of insulin resistance or altering insulin-mediated signaling in the heart, skeletal muscle, or vasculature.

Bosse, John D.; Lin, Han Yi; Sloan, Crystal; Zhang, Quan-Jiang; Abel, E. Dale; Pereira, Troy J.; Dolinsky, Vernon W.; Symons, J. David

2013-01-01

460

Optical gain spectra of high density electron-hole plasma in GaSe and InSe  

NASA Astrophysics Data System (ADS)

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.

Cingolani, R.; Ferrara, M.; Lugarà, M.

1988-04-01

461

Aripiprazole Partial Agonism at 5-HT2C: A Comparison of Weight Gain Associated With Aripiprazole Adjunctive to Antidepressants With High Versus Low Serotonergic Activities  

PubMed Central

Objective: 5-HT2C receptor antagonists are thought to contribute toward increased appetite and obesity. Aripiprazole acts as a partial agonist at the 5-HT2C receptor; hence, it is thought to cause little or no significant weight gain when used alone. We theorize that, in the presence of antidepressants with high serotonergic activity, aripiprazole acts as an antagonist at the 5-HT2C receptor, thus increasing the potential for weight gain. Conversely, in environments with low serotonergic activity, aripiprazole acts as an agonist at the 5-HT2C receptor, therefore having less potential for weight gain. Method: A retrospective electronic medical record chart review of the Veterans Integrated Service Network 22 Veterans Affairs database was performed comparing patients’ weight and body mass index (BMI) while taking aripiprazole alone (n = 1,177), versus aripiprazole plus a high-serotonergic antidepressant (citalopram, fluoxetine, paroxetine, sertraline, or venlafaxine) (n = 145), versus aripiprazole plus a low-serotonergic antidepressant (bupropion) (n = 77) for a minimum continuous duration of 6 months of aripiprazole monotherapy or combination treatment. The study was conducted from January 2010 through June 2011. Results: In our patient population, only the aripiprazole plus high-serotonergic antidepressants group had a statistically significant increase in weight (P = .0027) and BMI (P = .0016). Conclusions: Our data suggest that, in the presence of antidepressants with high serotonergic activity, aripiprazole may act as an antagonist at the 5-HT2C receptor, resulting in weight gain. Conversely, when aripiprazole is used in the presence of antidepressants with low serotonergic activity, it may act as an agonist and result in little or no weight gain. This varying effect at the 5-HT2C receptor may explain why aripiprazole has not been associated with significant weight gain in previous studies focusing on schizophrenia and bipolar disorder.

Nguyen, Charles T.; Bota, Robert G.

2012-01-01

462

Properties of laser gain of Li:CdZnO/ZnMgO quantum well  

NASA Astrophysics Data System (ADS)

The many-body optical gain in Li:CdZnO/MgZnO quantum well (QW) structures with spontaneous polarization and piezoelectric polarization, and ferroelectric dipole moment is investigated by using the non-Markovian gain model with many-body effects. The CdZnO/MgZnO QW structure with high Cd composition is found to have smaller optical gain because the strain-induced piezoelectric polarization and the spontaneous polarization in the well increase with the inclusion of Cd. The internal field is reduced due to the additional polarization by Li in the CdZnO/MgZnO QW structure. These results show that Li:CdZnO-based QW lasers are promising candidates for optoelectric applications in visible and UV regions.

Jeon, H. C.; Lee, S. J.; Park, S. H.; Kang, T. W.

2009-12-01

463

Many-body optical gain in CdZnO/ZnMgO quantum well lasers  

NASA Astrophysics Data System (ADS)

The Many-body optical gain in CdZnO/MgZnO quantum well (QW) structures with spontaneous and piezoelectric polarizations are investigated by using the non-Markovian gain model with many-body effects. As the Cd composition increases, the sign change of the internal field is observed and the bottom of the potential well in the conduction band is shown to exist on the right side in the well. The CdZnO/MgZnO QW structure with high Cd composition is found to have smaller optical gain because the strain-induced piezoelectric polarization and the spontaneous polarization in the well increase with the inclusion of Cd.

Li, Mingkai; Won Kang, Tae; Joo Lee, Seung; Park, Seoung-Hwan; Ahn, Doyeol; Ihm, Gukhyung

2010-01-01

464

Spontaneous generation  

NSDL National Science Digital Library

This lesson demonstrates that scientific knowledge is stable, but also prone to change. Students will understand how those changes can happen in the context of the history of spontaneous generation. This lesson from the American Association for the Advancement of Science aligns with Benchmarks 1 and 10, Nature of Science, and History of Science. It can be done as a class or via student independent study. Part of the lesson involves students accessing related information on the Internet. Thorough teacher background information and pedagogically sound, structured discussion questions are provided.

2001-01-01

465

High temporal resolution of ion fluxes in semi-natural ecosystems – gain of information or waste of resources?  

Microsoft Academic Search

Monitoring programs of ion concentrations and fluxes in semi-natural ecosystems are confronted with the task to gain as much information as possible with simultaneously minimizing costs and efforts. The aim of this study was (i) to assess how much of the heterogeneity of solution concentrations is lost because of temporal integration of measurements and (ii) to estimate the error in

C. Alewell; G. Lischeid; U. Hell; B. Manderscheid

2004-01-01

466

A Novel Precision Real-Time Material Inspection System Using Cascaded Wide Gain Range Amplifiers With High Modulation Bandwidth  

Microsoft Academic Search

In this paper, the authors present the design and implementation of a microwave oscillator circuit with ultra-fast amplitude control for an inspection system appropriate for real-time measurements of continously streaming materials. The material passing through the resonator of the oscillator changes the resonance frequency and the quality factor of the resonator. This influences the oscillation frequency and the loop gain

Christian Hoffmann; Tobias Hermann; Peter Russer

2009-01-01

467

Interplay of nonlinearity and gain-shaping in high-energy femtosecond Yb-doped fiber amplifiers  

Microsoft Academic Search

Spectral shaping in a fiber amplifier in the presence of finite gain bandwidth (15 nm) and large nonlinear phase shifts (up to ~12 phi) is studied numerically and experimentally. Pulses amplified to 30 muJ are dechirped to ~250 fs duration

L. Kuznetsova; A. Chong; R. W. Wise

2006-01-01

468

Use of a magnetron as a high-gain, phased-locked amplifier in an electronically-steerable phased array for wireless power transmission  

Microsoft Academic Search

A conventional microwave oven magnetron is combined with a ferrite circulator to create a high-gain phase-locked amplifier with independent control of frequency and power output. The intended application is for electronically-steerable phased arrays for wireless power transmission

M. C. Hatfield; J. G. Hawkins; W. C. Brown

1998-01-01

469

Significant progression of load on the musculoskeletal system with extremely high loads, with rapid weekly weight gains, using the Anatoly Gravitational System, in a 10-week training period  

PubMed Central

In an age of increasing numbers of lifestyle diseases and plasticity of longevity, exercise and weight training have been increasingly recognized as both preventing and mitigating the severity of many illnesses. This study was designed to determine whether significant weight-lifting gains could be realized through the Anatoly Gravitational System. Specifically, this study sought to determine whether this once-weekly weight-training system could result in significant weekly strength gains during a 10-week training period. A total of 50 participants, ranging in age from 17 to 67 years, completed at least 10 weekly 30-minute training sessions. The results suggest participants could, on average, double their weight-lifting capacity within 10 sessions. This preliminary study, which would require further scrutiny, suggests the Anatoly Gravitational System provides a rather unique opportunity to load the musculoskeletal system with extremely high loads, with rapid weekly weight gains, using only short weekly training sessions. More studies are warranted to scrutinize these findings.

Burke, David T; Tran, David; Cui, Di; Burke, Daniel P; Al-Adawi, Samir; Dorvlo, Atsu SS

2013-01-01

470

Dietary supplementation with purified mulberry (Morus australis Poir) anthocyanins suppresses body weight gain in high-fat diet fed C57BL/6 mice.  

PubMed

We present our experiment about adding anthocyanins to the daily food of mice. Three kinds of anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutinoside and pelargonidin-3-glucoside) purified from Chinese mulberry (Morus australis Poir) were evaluated for suppressing body weight gain of the male C57BL/6 mice fed with high-fat diet (HFD). The results from a 12-week experiment show that consumption of purified mulberry anthocyanins (MACN) of 40 or 200mg/kg can significantly inhibit body weight gain, reduce the resistance to insulin, lower the size of adipocytes, attenuate lipid accumulation and decrease the leptin secretion. Thus, dietary supplementation with MACN can protect against body weight gain of the diet-induced obese mice. PMID:23768383

Wu, Tao; Qi, Xueming; Liu, Yan; Guo, Jun; Zhu, Ruiyu; Chen, Wei; Zheng, Xiaodong; Yu, Ting

2013-11-01

471

High net modal gain (>100 cm(-1)) in 19-stacked InGaAs quantum dot laser diodes at 1000 nm wavelength band.  

PubMed

An InGaAs quantum dot (QD) laser diode with 19-stacked QDs separated by 20 nm-thick GaAs spacers was fabricated using an ultrahigh-rate molecular beam epitaxial growth technique, and the laser characteristics were evaluated. A 19-stacked simple broad area QD laser diode was lased at the 1000 nm waveband. A net modal gain of 103 cm(-1) was obtained at 2.25 kA/cm(2), and the saturated modal gain was 145.6 cm(-1); these are the highest values obtained to our knowledge. These results indicate