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1

Coherent spontaneous emission in high gain free-electron lasers  

Microsoft Academic Search

We investigate finite pulse effects in self-amplified spontaneous emission (SASE), especially the role of coherent spontaneous emission (CSE) in the start and the evolution of the free-electron laser (FEL) process. When the FEL interaction is negligible, we solve the one-dimensional Maxwell equation exactly and clarify the meaning of the slowly varying envelope approximation (SVEA). In the exponential gain regime, we

Zhirong Huang; Kwan-Je Kim

1999-01-01

2

Coherent spontaneous emission in high gain free-electron lasers  

Microsoft Academic Search

The authors investigate finite pulse effects in self-amplified spontaneous emission (SASE), especially the role of coherent spontaneous emission (CSE) in the start and the evolution of the free-electron laser (FEL) process. When the FEL interaction is negligible, they solve the one-dimensional Maxwell equation exactly and clarify the meaning of the slowly varying envelope approximation (SVEA). In the exponential gain regime,

muang

1999-01-01

3

Influence of amplified spontaneous emission on gain lifetime in high-aperture Ti:sapphire amplifiers.  

PubMed

We demonstrate that by lowering gain lifetime, transverse amplified spontaneous emission imposes practical limit on usable aspect ratio of large-aperture amplifiers in a high-energy Ti:sapphire system. PMID:23670763

Yanovsky, Victor; Krushelnick, Karl

2013-04-10

4

Spontaneous emission high-gain harmonic generation free-electron laser  

Microsoft Academic Search

A scheme, spontaneous emission high-gain harmonic generation (SEHG) free-electron laser (FEL), is proposed and analyzed for generating the X-ray FEL. The SEHG scheme works in a similar mechanism as high-gain harmonic generation (HGHG), but without the need for a seed laser. The scheme requires two undulators. The 1st undulator must be sufficiently long so that the energies of electrons are

Qingzi Xing; Xinlu Xu; Chao Feng; Chuanxiang Tang

2011-01-01

5

Multilevel quantum electrodynamic calculation of spontaneous emission and small signal gain in high voltage free electron lasers  

Microsoft Academic Search

Using the Weisskopf-Wigner technique, a self consistent quantum electrodynamic (SCQED) theory of spontaneous emission of radiation and single photon small signal gain is developed for high voltage free electron lasers (FEL). Excellent agreement is obtained simultaneously to our knowledge for the first time between the predictions and the experimental observations for lineshift, linewidth and gain. The SCQED theory predicts lineshift

C. S. Chang; H. U. Fluhler

1991-01-01

6

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

7

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

8

Observation of Anomalously Large Spectral Bandwidth in a High-Gain Self-Amplified Spontaneous Emission Free-Electron Laser  

Microsoft Academic Search

Observation of ultra-wide bandwidth, up to a full width of 15%, high-gain operation of a self- amplified spontaneous emission free-election laser (SASE FEL) is reported. This type of lasing is obtained with a strongly chirped beam (?E\\/E ? 1.7%) emitted from the accelerator. Because of non- linear pulse compression during beam transport, a short, high current pulse with strong mismatch

G. Andonian; A. Murokh; J. B. Rosenzweig; R. Agustsson; M. Babzien; I. Ben-Zvi; P. Frigola; J. Y. Huang; L. Palumbo; C. Pellegrini; S. Reiche; G. Travish; C. Vicario; V. Yakimenko

9

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

10

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

11

High gain solar photovoltaics  

NASA Astrophysics Data System (ADS)

Skyline Solar Inc. has developed a novel silicon-based PV system to simultaneously reduce energy cost and improve scalability of solar energy. The system achieves high gain through a combination of high capacity factor and optical concentration. The design approach drives innovation not only into the details of the system hardware, but also into manufacturing and deployment-related costs and bottlenecks. The result of this philosophy is a modular PV system whose manufacturing strategy relies only on currently existing silicon solar cell, module, reflector and aluminum parts supply chains, as well as turnkey PV module production lines and metal fabrication industries that already exist at enormous scale. Furthermore, with a high gain system design, the generating capacity of all components is multiplied, leading to a rapidly scalable system. The product design and commercialization strategy cooperate synergistically to promise dramatically lower LCOE with substantially lower risk relative to materials-intensive innovations. In this paper, we will present the key design aspects of Skyline's system, including aspects of the optical, mechanical and thermal components, revealing the ease of scalability, low cost and high performance. Additionally, we will present performance and reliability results on modules and the system, using ASTM and UL/IEC methodologies.

MacDonald, B.; Finot, M.; Heiken, B.; Trowbridge, T.; Ackler, H.; Leonard, L.; Johnson, E.; Chang, B.; Keating, T.

2009-08-01

12

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

13

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

14

Hybrid optical antenna with high directivity gain  

NASA Astrophysics Data System (ADS)

Coupling between electronic state and far field light, including absorption and spontaneous emission, is a central issue for applications such as quantum metrology, optical quantum information, single molecule fluorescence spectroscopy, and ultra sensitive detection which demand on high quantum efficiency. In such applications, propagating far field light with diffraction limited spatial distribution has to be coupled to the electronic state of a quantum absorber/emitter with a size far below the diffraction limit. Such a significant contrast between the wavelengths of photon and electron sets limitations on the light-matter interaction strength. The most straight forward solution is to convert far-field modes to near-field modes with dimensional scale closer to the electronic state. The process of converting far field to near field and vice versa can be conducted by an antenna as an intermediate element between far field mode and electronic state in a quantum element (absorber/emitter). Here, we classify optical antenna based on their performance into three categories. Considering each category advantage, we propose a hybrid antenna with superior performance. A quantum efficiency of about 50% is predicted for a semiconductor with volume of ~?3/170. Despite the weak optical absorption coefficient of 2000 cm-1 in the long infrared wavelength of ~8 ?m, very strong far-filed coupling has been achieved, as evidenced by an axial directivity gain of 16 dB, which is only 3 dB bellow of theoretical limit.

Bonakdar, Alireza; Mohseni, Hooman

2013-09-01

15

High-gain photorefractive polymers  

NASA Astrophysics Data System (ADS)

We report on the photorefractive properties of polymer composites based on the dye 2, N, N-dihexylamino-7- dicyanomethylidenyl-3, 4, 5, 6, 10-pentahydronaphthalene (DHADC-MPN). At 633 nm and with 2,4,7-trinitrofluorenone as a sensitizer, the polyvinylcarbazole-based composites show complete internal diffraction at applied electric fields as low as E(pi /2) equals 30 V/micrometer. The sensitivity of the composite could be extended into the infrared by using (2,4,7-trinitro-9-fluorenylidene)malonitrile as a sensitizer, and at 830 nm complete internal diffraction occurred at an applied field of Epi/2 equals 59 V/micrometer. Finally, by using DHADC-MPN as a trifunctional dopant in an inert matrix, we have achieved a dynamic range of (Delta) n equals 0.0085 and a net two-beam coupling gain of (Gamma) equals 202 cm-1 at an applied field of 50 V/micrometer and at 633 nm. The composites are thermally stable or have shelf lifetimes of at least several years at room temperature.

Hendrickx, E.; Herlocker, J.; Maldonado, J. L.; Guillemet, G.; Roeckel, Harold; Erskine, L.; Marder, Seth R.; Kippelen, Bernard; Peyghambarian, Nasser

1998-04-01

16

Single-pass high-gain free electron laser electron beam diagnostics  

Microsoft Academic Search

Consensus reached in the last few years that fourth generation light source will most likely be a X-ray or a UV coherent source based on single-pass high-gain free electron laser (FEL), such as Self Amplified Spontaneous Emission (SASE), or seeded high-gain harmonic-generation (HGHG) free electron lasers. High-gain (>107) required for single-pass FEL puts great constrain on the quality of electron

X. J. Wang

2000-01-01

17

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

18

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

19

Solution to the initial value problem for a high-gain FEL via Van Kampen's method  

NASA Astrophysics Data System (ADS)

Using Van Kampen's normal mode expansion, we solve the initial value problem for a high-gain free-electron laser described by the three-dimensional Maxwell-Klimontovich equations. An expression of the radiation spectrum is given for the process of coherent amplification and self-amplified spontaneous emission. It is noted that the input coupling coefficient for either process increases with the initial beam energy spread. The effective start-up noise is identified as the coherent fraction of the spontaneous undulator radiation in one field gain length, and is larger with increasing energy spread and emittance mainly because of the increase in gain length.

Huang, Zhirong; Kim, Kwang-Je

2001-12-01

20

Solution to the initial value problem for a high-gain FEL via Van Kampen's method.  

SciTech Connect

Using Van Kampen's normal mode expansion, we solve the initial value problem for a high-gain free-electron laser (FEL) described by the three-dimensional Maxwell-Klimontovich equations. An expression of the radiation spectrum is given for the process of coherent amplification and self-amplified spontaneous emission. It is noted that the input coupling coefficient for either process increases with the initial beam energy spread. The effective start-up noise is identified as the coherent fraction of the spontaneous undulator radiation in one field gain length, and is larger with increasing energy spread and emittance mainly because of the increase in gain length.

Huang, Z.; Kim, K.-J.

2000-08-22

21

Effective gain clamping of semiconductor optical amplifiers by injecting broad-band self-generated amplified spontaneous emission  

Microsoft Academic Search

A conventional SOA is effectively gain-clamped by the injection of self-generated broadband amplified spontaneous emission. The gain is clamped up to an input power of-2 dBm with an output power in excess of 11 dBm.

J. M. Oh; D. Lee

2007-01-01

22

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

23

Hybrid optical antenna with high directivity gain.  

PubMed

Coupling of a far-field optical mode to electronic states of a quantum absorber or emitter is a crucial process in many applications, including infrared sensors, single molecule spectroscopy, and quantum metrology. In particular, achieving high quantum efficiency for a system with a deep subwavelength quantum absorber/emitter has remained desirable. In this Letter, a hybrid optical antenna based on coupling of a photonic nanojet to a metallo-dielectric antenna is proposed, which allows such efficient coupling. A quantum efficiency of about 50% is predicted for a semiconductor with volume of ~?³/170. Despite the weak optical absorption coefficient of 2000 cm(-1) in the long infrared wavelength of ~8 ?m, very strong far-field coupling has been achieved, as evidenced by an axial directivity gain of 16 dB, which is only 3 dB below of theoretical limit. Unlike the common phased array antenna, this structure does not require coherent sources to achieve a high directivity. The quantum efficiency and directivity gain are more than an order of magnitude higher than existing metallic, dielectric, or metallo-dielectric optical antenna. PMID:23903124

Bonakdar, Alireza; Mohseni, Hooman

2013-08-01

24

Mechanisms of the Rosetta high gain antenna  

NASA Astrophysics Data System (ADS)

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

Pereira, Carlos

2001-09-01

25

An output amplitude configurable wideband automatic gain control with high gain step accuracy  

Microsoft Academic Search

An output amplitude configurable wideband automatic gain control (AGC) with high gain step accuracy for the GNSS receiver is presented. The amplitude of an AGC is configurable in order to cooperate with baseband chips to achieve interference suppression and be compatible with different full range ADCs. And what's more, the gain-boosting technology is introduced and the circuit is improved to

He Xiaofeng; Mo Taishan; Ma Chengyan; Ye Tianchun

2012-01-01

26

Progress toward high-gain laser fusion  

SciTech Connect

A 1985-1986 Review of the US inertial confinement fusion program by the National Academy of Sciences concluded that five more years might be required to obtain enough data to determine the future course of the program. Since then, data from the Nova laser and from the Halite/Centurion program have resolved most of the outstanding problems identified by the NAS review. In particular, we now believe that we can produce a sufficiently uniform target; that we can keep the energy content in hot electrons and high-energy photons low enough (/approximately/1--10% of drive energy, depending on target design) and achieve enough pulse-shaping accuracy (/approximately/10%, with a dynamic range of 100:1) to keep the fuel on a near-Fermi-degenerate adiabat; that we can produce an /approximately/100-Mbar pressure pulse of sufficient uniformity (/approximately/1%), and can we control hydrodynamic instabilities so that the mix of the pusher into the hot spot is low enough to permit marginal ignition. These results are sufficiently encouraging that the US Department of Energy is planning to complete a 10-MJ laboratory microfusion facility to demonstrate high-gain ICF in the laboratory within a decade. 22 refs., 1 fig.

Storm, E.

1988-09-28

27

High-gain end-pumped lasers  

Microsoft Academic Search

New-generation diode pump sources allow end-pumped cw lasers to achieve gain levels previously reached only in quasi-cw diode-pumped systems. We report end-pumped lasers with single-pass small signal gain G=10, producing Q-switched output at the 16-W level in 6-ns pulses at 20 kHz. We achieved these results with a modified version of the Opto Power Beam Shaper, capable of producing a

M. Fuller; D. Matthews; L. R. Marshall

1998-01-01

28

8 GHz high conversion gain Darlington mixer  

Microsoft Academic Search

This paper describes a new Darlington AC-coupled mixer operating at 8 GHz with improved figure-of-merits. This Darlington AC-coupled mixer along with a simple AC- coupling mixer used for reference are implemented in a 0.35 mum SiGe bipolar process. The supply voltage and current consumption are 3.2 V and 28 mA. In the Darlington AC-coupling mixer, the conversion gain, the operating

Jongsoo Lee; Patrick Roblin; Steven Bibyk; Chang-Woo Kim; Hyo-Dal Park; Young-Gi Kim

2007-01-01

29

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.

2013-10-01

30

Optical gain and spontaneous emission of strain-compensated InGaN-AlGaN quantum wells including carrier screening effect  

NASA Astrophysics Data System (ADS)

Strain-compensated InGaN quantum well (QW) active region employing tensile AlGaN barriers was analyzed as improved gain media for laser diodes emitting at 430-440 nm by taking into account the carrier screening effect. The use of strain-compensated InGaN-AlGaN structure is advantageous because the tensile barriers compensate the compressive strain in the InGaN QW and the larger band offset allows high temperature operation. The band structure is calculated by using a 6-band k times p formalism, taking into account valence band mixing, strain effect, spontaneous and piezoelectric polarizations. The carrier screening effect is incorporated in the calculation, which is solved self-consistently. The spontaneous emission spectra show a significant improvement of the radiative emission for strain-compensated structure. The optical gain analysis shows enhancement in the peak optical gain for the strain-compensated QW structures. Threshold analysis of both the conventional InGaN-GaN QW and strain-compensated InGaN-AlGaN QW active regions indicate a reduction in the threshold carrier density and threshold current density for diode laser employing the strain-compensated QW as its active region.

Zhao, Hongping; Arif, Ronald A.; Ee, Yik Khoon; Tansu, Nelson

2008-03-01

31

Critical elements of high gain laser fusion  

Microsoft Academic Search

Progress toward high laser fusion can be measured by a set of five critical elements. They are: (1) the laser-to-fuel coupling efficiency, (2) the cold fuel isentrope, (3) the implosion symmetry, (4) the ablation pressure, and (5) the ignition concept.

Stephen E. Bodner

1981-01-01

32

Gas Gain Stability of MSGCs Operating at High Rate.  

National Technical Information Service (NTIS)

Micro Strip Gas Counters (MSGCs) with coated and uncoated borosilicate glass substrates have been investigated on their high rate capability and long term gas gain stability. It is shown that the gain remains almost constant at count rates up to (10 to th...

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

1997-01-01

33

Stacking nonenzymatic circuits for high signal gain  

PubMed Central

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

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

2013-01-01

34

Giotto Spacecraft High Gain Antenna Mechanical Design and Development.  

National Technical Information Service (NTIS)

The development approach of the Giotto spacecraft high gain antenna structure is presented. The antenna structure consists of a dynamically and statically balanced offset parabolic reflector and a tripod support structure for the S/X-band feed. The reflec...

R. Halm F. Felici H. J. Schoedel H. Raupp

1986-01-01

35

Studies of high-gain microchannel plate photomultipliers  

SciTech Connect

The characteristics and performance of several kinds of high-gain micro-channel plate photomultipliers have been investigated. Special attention was directed toward (1) lifetime studies, (2) performance in the magnetic field, and (3) timing properties. Lifetime studies include separate investigations of the photocathode quantum efficiency degradation caused by ion feedback, and the deterioration of the micro-channel plate gain. The dependence of the micro-channel plate photomultiplier gain on the intensity and the direction of the magnetic field (up to 7 kGauss) is reported.

Oba, K.; Rehak, P.

1980-01-01

36

Spontaneous nonthermal leptogenesis in high-scale inflation models  

SciTech Connect

We argue that a nonthermal leptogenesis occurs spontaneously, without direct couplings of the inflaton with right-handed neutrinos, in a wide class of high-scale inflation models such as the chaotic and hybrid inflation. It is only a finite vacuum expectation value of the inflaton, or more precisely, a linear term in the Kaehler potential, that is a prerequisite for the spontaneous nonthermal leptogenesis. To exemplify how it works, we show that a chaotic inflation model in supergravity naturally produces a right amount of baryon asymmetry via the spontaneous nonthermal leptogenesis. We also discuss the gravitino production from the inflaton.

Endo, Motoi; Takahashi, Fuminobu [Deutsches Elektronen Synchrotron DESY, Notkestrasse 85, 22607 Hamburg (Germany); Yanagida, T. T. [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Research Center for the Early Universe, University of Tokyo, Tokyo 113-0033 (Japan)

2006-12-15

37

High gain amplifiers: Power oscillations and harmonic generation  

SciTech Connect

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

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

2007-08-01

38

Inflight calibration technique for onboard high-gain antenna pointing  

Microsoft Academic Search

The X-band radio frequency communication system was used for the first time in deep space planetary exploration by the Mariner 10 Venus and Mercury flyby mission. This paper presents the technique utilized for and the results of inflight calibration of high-gain antenna (HGA) pointing. Also discussed is pointing accuracy to maintain a high data transmission rate throughout the mission, including

H. Ohtakay; J. M. Hardman

1975-01-01

39

High gain harmonic generation x-ray free electron laser.  

National Technical Information Service (NTIS)

We present the calculation on the performance of a High Gain Harmonic Generation (HGHG) X-ray Free Electron Laser (FEL) based on the high quality electron beam from the proposed Photoinjected Energy Recovery Linac (PERL) at the NSLS. We consider several s...

Wu Yu

2001-01-01

40

Coherent Amplification of an Ultrashort Pulse in a High- and Swept-Gain Medium with Level Degeneracy  

SciTech Connect

A one-dimensional model of the coherent amplification in a high- and swept-gain amplifier in the presence of strong spontaneous emission is presented and applied to seeding an x-ray laser with a high harmonic pulse. The atomic structure of the amplifying medium includes level degeneracy, and the Maxwell-Bloch equations are used to describe the propagation and interaction processes. This analysis elucidates, in the most comprehensive way, the influence of the random spontaneous emission on the coherent amplification process, as reflected in the basic pulse parameters such as its shape, polarization, and coherence.

Kim, Chul Min; Lee, Jongmin; Janulewicz, Karol A. [Center for Femto-Atto Science and Technology, and Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); School of Photon Science and Technology, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

2010-02-05

41

High-gain bipolar detector on float-zone silicon  

Microsoft Academic Search

Since the float-zone (FZ) silicon has lower contaminations and longer minority-carrier lifetime than those in Czochralski silicon and other semiconductor materials, it has potential advantages to fabricate bipolar detectors on the high-purity FZ silicon substrate to achieve a high gain at ultra-low-signal levels. The authors present preliminary experimental results on a bipolar detector fabricated on an unusual high-purity FZ silicon

D. J. Han; G. Batignani; A. Del Guerra; G.-F. Dalla Betta; M. Boscardinc Betta; L. Bosisio; M. Giorgi; F. Forti

2003-01-01

42

Best Practices for Achieving High, Rapid Reading Gains  

ERIC Educational Resources Information Center

The percentage of students who read at the proficient level on the National Assessment of Educational Progress (NAEP) has not improved, and is appallingly low. In order for students to achieve high reading gains and become life-long readers, reading comprehension and reading enjoyment must be the top two goals. This article presents several…

Carbo, Marie

2008-01-01

43

High current gain HTS Josephson vortex flow transistors  

Microsoft Academic Search

We have fabricated discrete Josephson vortex flow transistors from yttrium barium copper oxide thin-films on 24 degree strontium titanate bicrystals. The devices have an asymmetric design with the control current fed through an independent control line. We have measured high current gains, in excess of 20 at 77 K for a range of several devices, and substantially higher at lower

P. A. C. Tavares; E. J. Romans; C. M. Pegrum

1999-01-01

44

STARS A Two Stage High Gain Harmonic Generation FEL Demonstrator.  

National Technical Information Service (NTIS)

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 cons...

D. Kramer F. Marhauser G. Wuestefeld M. Scheer P. Kuske

2007-01-01

45

Dispersion relations for 1D high-gain FELs  

SciTech Connect

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

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

2010-08-23

46

Waveguide tapering for FEL in high gain regime.  

National Technical Information Service (NTIS)

A Free Electron Laser (FEL) operation in the far infrared or millimeter wave region of the spectrum requires the use of a waveguide to confine the radiation. A new tapering scheme for operation in the high gain regime can thus be utilized in which the wav...

A. Dipace A. Doria G. P. Gallerano E. Sabia

1992-01-01

47

TOPEX High-Gain Antenna System Deployment Actuator Mechanism.  

National Technical Information Service (NTIS)

A deployment actuator mechanism was developed to drive a two-axis gimbal assembly and a high-gain antenna to a deployed and locked position on the Jet Propulsion Laboratory Ocean Topography Experiment (TOPEX) satellite. The Deployment Actuator Mechanism r...

S. R. Jones

1991-01-01

48

UV x-ray free electron lasers through high-gain single pass amplifier: Basic principles and issues  

SciTech Connect

The author reviews the basic principles of high gain free electron laser amplifier in single pass configuration for generation of intense, tunable radiation for wavelength shorter than 1,000 {angstrom}. Two schemes are discussed: for wavelength region between 1,000--100 {angstrom}, the high gain harmonic generation of a coherent input radiation can be used. For x-ray wavelength as short as a few {angstrom}, the self-amplified spontaneous emission is currently the only known free electron laser scheme. The author also presents a brief introduction of various key issues in realizing these schemes, which will be discussed in detail in other papers in these proceedings.

Kim, K.J.

1994-09-01

49

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

50

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

51

The extension of gain spectra and accurate determination of the quasi-Fermi-level separation from measured amplified spontaneous emission spectra  

NASA Astrophysics Data System (ADS)

A method for obtaining the gain spectra of semiconductor lasers in an extended energy range from amplified spontaneous emission (ASE) spectra is presented. Hakki-Paoli gain measurement is first used to determine the quasi-Fermi-level separation. By using the fitting process proposed, a self-consistent correction in determining quasi-Fermi separation leads to a reduced error (<1 meV) and a recalibration of the intrinsic absorption coefficient is also self-consistently possible. Subsequently, with measured gain in a restricted energy range, we can obtain gain spectra in a much wider energy range by our proposed algorithm in conjunction with ASE data. The application of this method in obtaining the extended gain spectra of a double-quantum-well GaInP ridge waveguide laser is demonstrated.

Fu, Liwei; Wu, Linzhang; Schweizer, Heinz

1999-11-01

52

The integral equation for a high gain FEL  

SciTech Connect

The theory of a high gain free electron laser (FEL) is now well developed. In this paper I derive the equation for the electron distribution function, which is valid for FELs with a longitudinally inhomogeneous magnetic system (which may include, in particular, dispersive sections, quadrupole lenses, and simply empty spaces between the undulator sections), magnetic field errors in undulators, and some other options. The integral form of the equation may be useful for numerical calculations.

Vinokurov, N.A. [AN SSSR, Novosibirsk (Russian Federation). Inst. Yadernoj Fiziki][Argonne National Lab., IL (United States)

1996-07-01

53

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

54

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

55

HIGH GAIN HARMONIC GENERATION X-RAY FREE ELECTRON LASER.  

SciTech Connect

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

WU, J.; YU, L.H.

2001-06-18

56

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

57

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

58

Mode control in a high-gain relativistic klystron amplifier  

NASA Astrophysics Data System (ADS)

Middle cavities between the input and output cavity can be used to decrease the required input RF power for the relativistic klystron amplifier. Meanwhile higher modes, which affect the working mode, are also easy to excite in a device with more middle cavities. In order for the positive feedback process for higher modes to be excited, a special measure is taken to increase the threshold current for such modes. Higher modes' excitation will be avoided when the threshold current is significantly larger than the beam current. So a high-gain S-band relativistic klystron amplifier is designed for the beam of current 5 kA and beam voltage 600 kV. Particle in cell simulations show that the gain is 1.6 × 105 with the input RF power of 6.8 kW, and that the output RF power reaches 1.1 GW.

Li, Zheng-Hong; Zhang, Hong; Ju, Bing-Quan; Su, Chang; Wu, Yang

2010-05-01

59

Spontaneous Raman scattering as a high resolution XUV radiation source  

Microsoft Academic Search

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.

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

1983-01-01

60

Coherent X-ray production by cascading stages of a high-gain harmonic generation free-electron laser  

Microsoft Academic Search

Here we study a new approach for producing coherent X-rays by cascading several stages of a High-Gain Harmonic Generation (HGHG) Free-Electron Laser (FEL). Our calculation shows that such a scheme is feasible within the present technology. Compared with the Self-Amplified Spontaneous Emission (SASE) FEL scheme, the HGHG FEL scheme could provide radiation with the following advantages: better longitudinal coherence, narrower

Juhao Wu

2002-01-01

61

Investigations of electron-beam microbunching and beam coalignment using CTR in a high-gain SASEe FEL  

Microsoft Academic Search

We recently extended our experiments on z-dependent electron-beam microbunching using coherent transition radiation (CTR) into the high-gain, self-amplified spontaneous emission free-electron laser (FEL) regime. The UV-visible FEL at the Advanced Photon Source was operated at 530 nm and 385 nm using the bunch-compressed photocathode gun electron beam, linac, and 21.6 m of undulator length. The longitudinal microbunching of the electron

A. H. Lumpkin; W. J. Berg; S. Biedron; M. Borland; Y.-C. Chae; R. Dejus; J. Lewellen; S. Milton; E. Moog; G. Travish; B. Yang

2001-01-01

62

Diamagnetic fields due to finite-dimension intense beams in high-gain free-electron lasers  

Microsoft Academic Search

High-gain, self-amplified spontaneous emission free-electron lasers (SASE FEL's), with proposed operation in wavelengths extending down to x rays, require intense relativistic electron beams, which under certain conditions can generate large diamagnetic fields. The action of these fields has the potential to seriously degrade FEL performance. It is shown here by both analysis and simulation that the finite size of the

J. B. Rosenzweig; P. Musumeci

1998-01-01

63

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

ERIC Educational Resources Information Center

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

Seifert, Tricia A.; Asel, Ashley M.

2011-01-01

64

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

2010-05-30

65

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 22keV 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

66

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

Microsoft Academic Search

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

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

2010-01-01

67

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

68

Limited Geiger-mode silicon photodiode with very high gain  

NASA Astrophysics Data System (ADS)

The novel type of the Silicon Photodiode - Limited Geiger-mode Photodiode (LGP) has been produced and studied. The device consists of many ~104mm-2 independent cells ~10mkm size around n+-``pins'' located between p-substrate and thin SiC layer. Very high gain more than 104 for 0.67mkm wave length light source and up to 6.105 for single electron have been achieved. The LGP photon detection efficiency at the level of one percent has been measured.

Bondarenko, G.; Dolgoshein, B.; Golovin, V.; Ilyin, A.; Klanner, R.; Popova, E.

1997-02-01

69

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

70

A high-gain, low-noise amplifier for EEG  

Microsoft Academic Search

This paper describes an amplifier for an electroencephalograph with gain of 1×104 to 1×106 and made entirely of commercially available IC components. The two-stage amplifier has a preamplifier stage with fixed gain\\u000a of 1000, and a second stage with variable gain from 1 to 100. The final stage, an anti-aliasing filter, adds a gain of 10\\u000a to the signal. The

Michael Wogan; David N. Michael

1988-01-01

71

High-gain harmonic-generation free-electron laser  

PubMed

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 technique and prepares the way for the application of this technique in the vacuum ultraviolet region of the spectrum, with the ultimate goal of extending the approach to provide an intense, highly coherent source of hard x-rays. PMID:10937992

Yu; Babzien; Ben-Zvi; DiMauro; Doyuran; Graves; Johnson; Krinsky; Malone; Pogorelsky; Skaritka; Rakowsky; Solomon; Wang; Woodle; Yakimenko; Biedron; Galayda; Gluskin; Jagger; Sajaev; Vasserman

2000-08-11

72

Enhanced high gain harmonic generation scheme with negative dispersion  

NASA Astrophysics Data System (ADS)

The enhanced high gain harmonic generation (EHGHG) scheme has been proposed and shown to be able to significantly enhance the performance of HGHG FEL. In this paper we investigate the EHGHG scheme with negative dispersion. The bunching factor at the entrance of the radiator is analyzed, which indicates that the scheme with negative dispersion can further weaken the negative effect of the dispersive strength on the energy spread correction factor. The numerical results from GENESIS (3D-code) are presented, and are in good agreement with our analysis. Then we comparatively study the effects of the initial beam energy spread and the relative phase shift on the radiation power. The results show that the EHGHG scheme with negative dispersion has a larger tolerance on the initial beam energy spread and a nearly equal wide good region of the relative phase shift compared with the case of positive dispersion.

Li, He-Ting; Jia, Qi-Ka

2013-02-01

73

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

74

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

75

Superradiance in the high-gain free-electron laser  

SciTech Connect

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

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

1989-10-15

76

High gain single GaAs nanowire photodetector  

NASA Astrophysics Data System (ADS)

An undoped single GaAs nanowire (NW) photodetector based on a metal-semiconductor-metal Schottky diode structure is fabricated by a focused ion beam method. The photoconductive gain of the device reaches 20 000 at low laser excitation. Bias-dependence of gain proves that the surface contributes more to the gain at higher bias because of an increased surface charge region. The spectral response demonstrates not only the band-edge absorption profile of the single GaAs NW, but also the existence of leaky-mode resonance.

Wang, Hao

2013-08-01

77

A Highly Linear Broadband Variable Gain LNA for TV Applications  

Microsoft Academic Search

A broadband variable-gain low noise amplifier with triple output for TV tuners has been demonstrated in a 0.18 mum SiGe technology. The gain varies continuously from 27 dB to -28 dB and has better than 1 dB precision over a 1GHz bandwidth. At 27 dB gain the amplifier shows 6.5 dB NF, 82 dBmV OIP3 and 121 dBmV OIP2. OIP3

D. Manstretta; L. Dauphinee

2007-01-01

78

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

79

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

80

Spontaneous vortex phase (SVP) of ruthenocuprate high Tc magneto- superconductors  

NASA Astrophysics Data System (ADS)

The Ru_{0.9}Sr_2YCu_{2.1}O_{7.9} compound synthesized by HPHT (high pressure high temperature) solid-state reaction route exhibits bulk superconductivity below 30 K. Also the Ru-spins are ordered magnetically above 143 K, with a ferromagnetic component at 5 K. Low field (<1000 Oe) M vs. H plots show that both the superconducting and ferromagnetic components are present in the compound at 5 K. At low temperatures, the compound though remains in spontaneous vortex phase, its M vs. H hysteresis loop is symmetric instead of the theoretically expected asymmetric one. Our results cast doubts on either theoretical model or the intrinsic nature of ferromagnetic superconductivity in studied ruthenate.

Awana, V. P. S.; Kishan, H.

2006-01-01

81

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

SciTech Connect

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

Biedron, S. G.

1999-02-26

82

High spin states in neutron rich nuclei from spontaneous fission  

SciTech Connect

One fragment-{gamma}-{gamma} and three {gamma}-{gamma} coincidence measurements of the prompt {gamma}-rays from the fragments produced in the spontaneous fission (SF) of {sup 252}Cf and very recently of {sup 242}Pu were carried out with a 20 Ge detector ball at HHIRF. With our high statistics, {gamma}-{gamma}-{gamma} coincidences where the two gates are on transitions in the two partner fragments were extracted. Comparing the {sup 252}Cf and {sup 242}Pu data allowed unique placements of many transitions. New, higher spin states were observed in many nuclei, up to 16{sup +} in some of the heavy partners. Levels in several nuclei were observed for the full time. Studies of the fission process included measured relative branchings to the 1n to 6n channels. Much data remains to be analyzed. These data provide new insights into the changing structures at higher spins of many neutron-rich nuclei and the fission process.

Butler-Moore, K.; Zhu, S.; Zhao, X.; Hamilton, J.H.; Ramayya, A.V.; Lu, Q.; Ma, W.C.; Peker, L.K.; Kormicki, J.; Deng, J.K.; Gore, P.; Shi, D.; Jones, E.F.; Xie, H.; Gao, W.B. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Physics; Cole, J.D.; Aryaeinejad, R. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Lee, I.Y.; Johnson, N.R.; McGowan, F.K.; Bemis, C.E. [Oak Ridge National Lab., TN (United States); Ter-Akopian, G.; Oganessian, Yu. [Joint Inst. for Nuclear Research, Dubna (Russian Federation)

1992-12-31

83

High energy ? rays from 252Cf spontaneous fission  

NASA Astrophysics Data System (ADS)

The spontaneous fission decay of 252Cf has been analyzed in a statistical model with emphasis on describing recently reported high energy ?-ray spectra. An enhanced ? emission in the range from 3 to 10 MeV which is observed for nearly symmetric mass splits is readily understood as a result of the different fragment excitation energies. The model includes a viscous motion to the scission point with the possibility of prescission ? emission. It was found that even with saddle-to-scission times of ?sc<66×10-19 s, the maximum consistent with prescission neutron multiplicities, prescission ? rays are overwhelmed by fragment ? rays. Thus, the recently reported strong angular anisotropy of ? rays in the range E?=8-12 MeV is unexplained within the present understanding of the fission process.

Hofman, D. J.; Back, B. B.; Montoya, C. P.; Schadmand, S.; Varma, R.; Paul, P.

1993-03-01

84

High spontaneous intrachromosomal recombination rates in ataxia-telangiectasia  

SciTech Connect

Ataxia-telangiectasia (A-T) is an inherited human disease associated with neurologic degeneration, immune dysfunctions, and high cancer risk. It has been proposed that the underlying abnormality in A-T is a defect in genetic recombination that interferes with immune gene rearrangements and the repair of DNA damage. Recombination was studied in A-T and control human fibroblast lines by means of two recombination vectors. Unexpectedly, spontaneous intrachromosomal recombination rates were 30 to 200 times higher in A-T fibroblast lines than in normal cells, whereas extrachromosomal recombination frequencies were near normal. Increased recombination is thus a component of genetic instability in A-T and may contribute to the cancer risk seen in A-T patients. 2 refs., 1 fig., 3 tabs.

Meyn, M.S. (Yale Univ., New Haven, CT (United States))

1993-05-28

85

High gain multigap avalanche detectors for Cerenkov ring imaging  

SciTech Connect

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

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

1980-10-01

86

Gain and luminescence modeling for high-power laser applications  

NASA Astrophysics Data System (ADS)

A general scheme for the determination of vital operating characteristics of semiconductor lasers from low intensity photo-luminescence spectra is outlined and demonstrated. A fully microscopic model for the optical properties is coupled to a drift-diffusion model for the mesoscopic charge and field distributions to calculate luminescence and gain spectra in barrier-doped laser material. Analyzing experiments on an optically pumped multi quantum-well structure it is shown that the electric fields arising from the charges of ionized dopants lead to strongly excitation dependent optical properties like significant differences between luminescence and gain wavelengths.

Hader, Joerg; Zakharian, Aramais R.; Moloney, Jerome V.; Nelson, Thomas R., Jr.; Ehret, James E.; Koch, Stephan W.

2003-06-01

87

Gaining Traction Gaining Ground: How Some High Schools Accelerate Learning for Struggling Students  

ERIC Educational Resources Information Center

|In recent years, a consensus has emerged on the need to improve America's high schools, especially for students who struggle academically. At every level--from the federal government to the local school board--policymakers are proposing new initiatives to raise standards while helping more students graduate with the knowledge and skills needed…

Education Trust, 2005

2005-01-01

88

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

89

A high-power high-gain single-polarization EDFA  

Microsoft Academic Search

Summary form only given. High power erbium doped fiber amplifiers (EDFAs) are key elements in both fiber optic distribution networks and free-space communications. Single-polarization EDFAs provide additional capabilities for polarization diplexing and improved communication performance since orthogonally polarized amplified spontaneous emission (ASE) can be eliminated at both receiver and transmitter. Such features can offer substantial benefit in free-space links where

D. O. Caplan; F. Hakimi

2000-01-01

90

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

PubMed

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

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

2010-11-12

91

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

Microsoft Academic Search

The vgf gene regulates energy homeostasis and the VGF-derived peptide TLQP-21 centrally exerts catabolic effects in mice and hamsters.\\u000a Here, we investigate the effect of chronic intracerebroventricular (icv) injection of TLQP-21 in mice fed high fat diet (HFD).\\u000a Fast weight-gaining mice injected with the peptide or cerebrospinal fluid were selected for physiological, endocrine, and\\u000a molecular analysis. TLQP-21 selectively inhibited the

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

2009-01-01

92

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

93

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

94

Telescope considered as a very high gain antenna  

NASA Astrophysics Data System (ADS)

A design concept for an optical-antenna telescope to be used in intersatellite communication (in the framework of the ESA SILEX project) is presented. The main technical requirements for a SILEX transmit-receive antennna telescope are reviewed, and a Cassegrain configuration based on a parabolic primary mirror, a hyperbolic secondary mirror, and a five-lense collimator (with baffles to limit stray light) is shown in diagrams and discussed in detail, with particular attention to local angular distortion and transmission-antenna gain. Results from tests on a breadboard version are presented in tables and graphs, including transmission of 92.6 percent at 820 nm, rms wavefront error less than lambda/28, optical gain 114.47 dB, backscattered energy 1.7 x 10 to the -6th at 838 nm, and stray-light intensity slightly above specification at sun aspect angles less than 4.5 deg.

Detaille, Michel; Houmault, Patrice

1990-07-01

95

High-Efficiency DC-DC Converter With High Voltage Gain and Reduced Switch Stress  

Microsoft Academic Search

In this paper, a high-efficiency dc-dc converter with high voltage gain and reduced switch stress is proposed. Generally speaking, the utilization of a coupled inductor is useful for raising the step-up ratio of the conventional boost converter. However, the switch surge voltage may be caused by the leakage inductor so that it will result in the requirement of high-voltage-rated devices.

Rong-Jong Wai; Chung-You Lin; Rou-Yong Duan; Yung-Ruei Chang

2007-01-01

96

Development of high gain three terminal devices - at millimeter wave frequencies  

Microsoft Academic Search

The objectives of this program are: to develop high gain three terminal devices at millimeter wave frequencies. Specifically, InGaAs pseudomorphic high electron mobility transistors (HEMT) will be developed in four key areas: materials, device models, processing, and characterization. The 36 month program consists of two tasks. Task I is to develop the high gain transistor with 6 dB gain, 0.3

E. K. Hsieh

1989-01-01

97

Communicative Spontaneity in Individuals with High Support Needs: An Exploratory Consideration of Causation.  

ERIC Educational Resources Information Center

|Reasons for limited spontaneity of communication in individuals with high support needs are considered and include: it is an inherent characteristic, a product of highly structured teaching programs, a form of learned helplessness, or a product of a failure to systematically program for spontaneity. (Contains references.) (Author/CR)|

Carter, Mark

2002-01-01

98

Optical guiding simulations for high gain-short wavelength FELs  

NASA Astrophysics Data System (ADS)

Optical guiding in the linear growth regime of an FEL amplifier has been reported in simulations by Scharlemann et al., using the LLNL 2D code FRED. We present the results of a parameter space investigation of optical guiding in an FEL using the FRED code with a realistic range of input parameters: optical wavelength, mode size and focus, current density, emittance, and wiggler period. We find that optical guiding has a profound impact on gain, and that within existing mirror technology and for the operating characteristics expected of the Stanford storage ring FEL now in construction, oscillation is achievable from the visible through 300 Å. We also describe the relative importance of guiding in different regimes. In support of these predictions we present ``FRED'' benchmarking results. Lawrence Livermore National Laboratory, University of California, Livermore, CA 94550, USA.

Lasala, J. E.; Deacon, D. A. G.; Scharlemann, E. T.

1986-09-01

99

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

100

Long lifetime, high density single-crystal erbium compound nanowires as a high optical gain material  

NASA Astrophysics Data System (ADS)

Erbium-containing materials of long lifetime and high Er density are important for achieving strong luminescence and high optical gain in compact integrated photonics devices. We have systematically studied the lifetime and crystal quality as a function of growth conditions for an erbium compound that we recently reported, erbium chloride silicate (ECS). The lifetime for the best quality ECS nanowires can be as long as 540 ?s, the longest for high-density Er-materials, representing a lifetime-density product as high as 8.7 × 1018 s cm-3. Such high density, long lifetime erbium materials can find many interesting applications such as compact lasers or amplifiers.

Yin, Leijun; Ning, Hao; Turkdogan, Sunay; Liu, Zhicheng; Nichols, Patricia L.; Ning, C. Z.

2012-06-01

101

High Resolution Stimulated Brillouin Gain Spectroscopy of Liquids, Supercooled Liquids, and Glasses.  

NASA Astrophysics Data System (ADS)

Stimulated Brillouin gain (SBG) spectroscopy is a relatively new light scattering technique based on the coherent excitation of acoustic waves by two laser beams. Compared to conventional Brillouin scattering methods, SBG spectroscopy possesses significant advantages in resolution, scanning range, accuracy, precision, and discrimination against elastic scattering. These advantages are illustrated here through studies of several liquids. The SBG spectra of three simple liquids, carbon disulfide, carbon tetrachloride, and methylene chloride, were shown to be in excellent correspondence with previous spontaneous Brillouin measurements. The narrow Brillouin linewidth for carbon disulfide and the detection of the weak "Mountain mode" in the carbon tetrachloride spectrum illustrate the resolution and sensitivity of the technique, whereas the smooth variation in the Brillouin shift with temperature for methylene chloride illustrates the excellent precision. The dependence of the peak gain and linewidth on scattering angle was evaluated in carbon disulfide. The gain was found to be greatly reduced at angles away from backscattering, and the forward scattering linewidths were shown to be dominated by two instrumental effects, the laser frequency jitter and an uncertainty in the scattering wavevector arising from laser beam focusing. The temperature dependent spectra of carbon disulfide revealed asymmetric lineshapes at low temperatures originating from a dynamic coupling between the rotational and translational motions of the carbon disulfide molecules. These observations were well described by the theory of Chappell and Kivelson. The extreme precision of SBG Brillouin shift measurements was illustrated in a search for a recently proposed "structural transition" in the liquid phase of benzene. Our results show no such transition. Glycerol was studied over the temperature ranges 146-300 K and 401-534 K, which include the supercooled liquid and glassy states. The high resolution and broad tuning range of our SBG instrument allowed for the simultaneous measurement of large Brillouin shifts and narrow linewidths. These measurements revealed two particular noteworthy features, a distinct kink in the temperature dependence of the Brillouin shift at the glass transition and the presence of a relaxation mechanism other than the primary (alpha) process which contributes to the linewidth both above and below the transition.

Grubbs, W. Tandy

102

High-Gradient High-Energy-Gain Inverse Free Electron Laser Experiment Using a Helical Undulator  

SciTech Connect

In this paper we present the design of the high-gradient, high-energy-gain IFEL accelerator proposed for construction at the ATF beamline in BNL. We plan to accelerate the ATF electron beam from 50 MeV to 120 MeV using a 60 cm long tapered permanent magnet helical undulator designed at UCLA and the existing ATF 0.5 TW CO2 laser system. The experiment will obtain a record 120 MV/m gradient and >70 MeV energy gain and will be an important step in the development of compact IFEL accelerators for the mid-high energy range (up to 1-2 GeV).

Musumeci, P.; Westfall, M.; Li, R. K. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California, 90095 (United States); Murokh, A.; Tremaine, A. [Radiabeam Technologies LLC, Santa Monica, CA (United States); Pogorelsky, I. V. [Brookhaven National Laboratory, Upton, NY 11973 (United States)

2010-11-04

103

Low-FPN high-gain capacitive transimpedance amplifier for low-noise CMOS image sensors  

Microsoft Academic Search

In this paper we introduce a low fixed pattern noise (LFPN) capacitive transimpedance amplifier (CTIA) for active pixel CMOS image sensors (APS) with high switchable gain and low read noise. The LFPN CTIA APS uses a switched capacitor voltage divider feedback circuit to achieve high sensitivity, low gain FPN, and low read noise. This paper discusses the operation of the

Boyd A. Fowler; Janusz Balicki; Dana How; Michael Godfrey

2001-01-01

104

Design and Deployment of Five High-Gain, Broad-Band, Long-Period Seismograph Station.  

National Technical Information Service (NTIS)

Five high-gain, broad-band, long period seismograph stations are being installed around the world. The instruments will probably have gains on the order of 100,000 or more at periods of 40 to 50 sec. This high sensitivity, some 50 to 100 times greater tha...

G. Hade P. L. Ward

1970-01-01

105

High-Gain Direct-Drive Target Design for Laser Fusion (Preprint).  

National Technical Information Service (NTIS)

A new laser fusion target concept is presented with a predicted energy gain of 125 using a 1.3 MJ KrF laser. This energy gain is sufficiently high for an economically attractive fusion reactor. X-rays from high- and low-Z materials are used in combination...

A. J. Schmitt D. G. Colombant M. Klapisch S. E. Bodner

2000-01-01

106

Proneness of oils to spontaneous ignition in high-pressure air compressors  

Microsoft Academic Search

A method has been developed to ascertain the propensity of compressor oils to spontaneous ignition, taking into account the processes of oxidation of the oil and spontaneous ignition of the products of its decomposition under the gas-dynamic conditions close to those actually prevailing in the delivery systems of high-pressure piston air compressors. Into a SKVD setup (shown) built for these

Smertyak

1986-01-01

107

Assessing the Impact of Elaborative Strategy Instruction Relative to Spontaneous Strategy Use in High Achievers.  

ERIC Educational Resources Information Center

Comparison of three learning strategies (elaborative interrogation, spontaneous strategy, or repetition control) with 53 high achievers in grades 5 and 6 found that both elaborative interrogation and spontaneous strategy conditions were equally effective and both were superior to the repetition condition. (DB)

Wood, Eileen; Hewitt, Kathryn L.

1993-01-01

108

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

SciTech Connect

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

YU,L.H.

2003-04-17

109

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); Sdrulla, D. [Advanced Power Technology, Bend, OR (United States)

1998-06-01

110

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

111

Reading Styles: High Gains for the Bottom Third.  

ERIC Educational Resources Information Center

Currently, only one-third of U.S. students read at acceptably high levels. Designed for inclusive programs, Reading Styles recognizes that everyone, not just "handicapped" students, has varying strengths and weaknesses. The program identifies youngsters' individual strengths; matches reading methods, materials, and strategies to these strengths;…

Carbo, Marie

1996-01-01

112

High-Gain Avalanche Rushing amorphous Photoconductor (HARP) detector  

Microsoft Academic Search

We have been studying a very sensitive image sensor since the early 1980s. In 1985, the author found for the first time that an experimental pickup tube with an amorphous selenium photoconductive target exhibits high sensitivity with excellent picture quality because of a continuous and stable avalanche multiplication phenomenon. We named the pickup tube with an amorphous photoconductive layer operating

K. Tanioka

2009-01-01

113

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

114

Photon detection with high gain avalanche photodiode arrays  

Microsoft Academic Search

The detection of light emitted in fast scintillating fiber bundles and Cerenkov radiators used for fiber calorimetry and tracking applications requires fast detector arrays with high sensitivity to short-wavelength photons. Photomultiplier tube arrays, the traditional imaging detectors for short-wavelength optical radiation, have limited spatial resolution and require expensive anti-magnetic shielding. We report on short-wavelength sensitivity improvement and detection efficiency performance

S. Vasile; P. Gothoskar; D. Sdrulla; R. Farrell

1997-01-01

115

High-gain InGaAsP-InP heterojunction phototransistors  

SciTech Connect

InGaAsP-InP heterojunction phototransistors have been fabricated by liquid phase epitaxy. The phototransistors have optical gains greater than 100 for 1.26-..mu..m radiation. High internal current gains (>300) have been achieved. Phototransistor relative spectral response has been measured for wavelengths in the range 0.7--1.5 ..mu..m.

Wright, P.D.; Nelson, R.J.; Cella, T.

1980-07-15

116

Integral equation based computer code for high-gain free-electron lasers.  

National Technical Information Service (NTIS)

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...

R. J. Dejus O. A. Shevchenko N. A. Vinokurov

1998-01-01

117

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

118

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

119

High-gain direct-drive target design for laser fusion  

SciTech Connect

A new laser fusion target concept is presented with a predicted energy gain of 127 using a 1.3 MJ KrF laser. This energy gain is sufficiently high for an economically attractive fusion reactor. X rays from high- and low-Z materials are used in combination with a low-opacity ablator to spatially tune the isentrope, thereby providing both high fuel compression and a reduction of the ablative Rayleigh-Taylor instability. (c) 2000 American Institute of Physics.

Bodner, S. E. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Colombant, D. G. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Schmitt, A. J. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Klapisch, M. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States)

2000-06-01

120

A high speed, high gain preamplifier system for silicon strip detectors  

SciTech Connect

A high speed, high gain amplifier system has been designed for silicon strip detectors. The amplifier has been designed using a semicustom bipolar linear array. This paper focuses on a practical integration of this amplifier into a working system. To maximize board density and reduce cost a new, relatively inexpensive custom chip carrier was designed. The design approach could be useful for other custom or semicustom chip designs. Insight into the design of a 128 channel preamplifier circuit board for low noise and low crosstalk using the new carrier is presented. High channel density presents challenges in cabling. A relatively new high density cable with mass termination capability was used for transmitting signals from the preamp to the discriminator boards. As a part of the overall design, the approach taken for shielding of the detector, preamplifier cards, and output cables is discussed.

Yarema, R.J.; Zimmerman, T. (Fermi National Accelerator Lab., Batavia, IL (USA))

1990-04-01

121

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

Microsoft Academic Search

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

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

2009-01-01

122

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

Federal Register 2010, 2011, 2012, 2013

...NUCLEAR WASTE TECHNICAL REVIEW BOARD Board Meeting...Lessons Gained From High-Level Nuclear Waste Disposal Efforts Pursuant to its authority...5051 of Public Law 100-203, Nuclear Waste Policy Amendments Act of 1987, the...

2010-10-04

123

Researchers Gain New Insights into How High Retinoic Acid Levels Affect Skin Development  

MedlinePLUS

... 2003 2002 2001 2000 1999 Spotlight on Research 2012 August 2012 Researchers Gain New Insights into How High Retinoic ... barrier formation and peridermal development. J Cell Sci. 2012 Apr 1;125(Pt 7):1827-36. Epub ...

124

Noise analysis of high-gain, low-noise column readout circuits for CMOS image sensors  

Microsoft Academic Search

The temporal read noise on the signal path of a complementary metal-oxide semiconductor image sensor is analyzed to investigate the effectiveness of high-gain column amplifiers in enhancing sensor sensitivity. The signal path examined includes a pixel source follower, a switched-capacitor, noise-cancelling, high-gain amplifier, and a sample-and-hold circuit in each column. It is revealed that the total random readout noise consists

Nobuhiro Kawai; Shoji Kawahito

2004-01-01

125

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

126

High Gain On-Chip Dielectric Resonator Antennas Using Silicon Technology for Millimeter Wave Wireless Links  

Microsoft Academic Search

A new high gain on-chip dielectric resonator antenna for 60 GHz radio wireless systems is demonstrated. The proposed rectangular integrated dielectric resonator antenna on conductive silicon (resistivity = 10 Omega-cm) has an impedance bandwidth of 1897 MHz at 59.56 GHz and 3.2 dB gain with 54% radiation efficiency, whereas for a similar antenna on high resistance silicon (resistivity = 100

P. V. Bijumon; A. P. Freundorfer; M. Sayer; Y. M. M. Antar

2007-01-01

127

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

128

The influence of inhomogeneous gain on high-frequency phase of chemical laser beam  

NASA Astrophysics Data System (ADS)

By establishing the model of chemical laser cavity, the eigen mode of laser and the phase distribution of output beam have been simulated numerically, and the influence of inhomogeneous gain on phase characteristics of output beam has been discussed detailedly by analyzing the power spectral density of wavefront phase. The results show that the inhomogeneous gain of chemical laser gives rise to the phase distortion of output wavefront and the obvious increase of high-frequency phase in distortion wavefront; in addition, the degree of high-frequency phase distortion is influenced by the ratio of each component in gain mediums. Therefor, the key factor that resulting in the distortion of high-frequency phase is the inhomogeneous gain.

Fu, Fu-xing; Zhang, Bin

2013-08-01

129

High gain S-band semiconductors optical amplifier with double-pass configuration  

NASA Astrophysics Data System (ADS)

In this paper we propose and demonstrate a double-pass configuration of a compact high gain short wavelength (S-) band amplifier based on a semiconductor optical amplifier (SOA) operating from 1480 to 1520 nm. The proposed system provides gain value of 31.07 dB at a signal power level of -40 dBm taken at 1500 nm. The measure gain profile of the double-pass configuration over different power levels and at different signal wavelengths outperforms that of the single-pass configuration. The noise figure of both configurations averages out to 10 dB. This system provides a good alternative as a high-gain and compact amplifier in the S-band region.

Ahmad, H.; Zulkifli, M. Z.; Hassan, N. A.; Latif, A. A.; Harun, S. W.

2011-07-01

130

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

131

A high voltage gain DC\\/DC converter for energy harvesting in single module photovoltaic applications  

Microsoft Academic Search

As PV modules show low voltage outputs, in grid connected applications a converter with high voltage gain is needed. Standard PV conversion systems, addressing PV field composed by a large number of panels, show efficiency values up to 95-96%. Such a high efficiency is hard to reach in small power DC\\/DC converters with high input to output voltage ratio as

Mario Cacciato; Alfio Consoli; Vittorio Crisafulli

2010-01-01

132

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

133

Design of a high gain and low sidelobe coaxial collinear antenna array  

Microsoft Academic Search

A high-gain and low-sidelobe coaxial collinear (COCO) array antenna is developed in the UHF band. The bandwidth of the array element reaches to 5.8% and the gain is 6.054dB. To suppress the grating lobes, a new method of spacing array element is considered and confirmed. A 42×15 coaxial collinear array antenna is designed with this method. The grating lobes of

Qiang Wang; Xiao-Lin Yang; Yan-Tao Li; Zhao-Bo Li; Si-Tao Chen

2011-01-01

134

High-dynamic-range VGA with temperature compensation and linear-in-dB gain control  

Microsoft Academic Search

This paper presents the design and measured performance of a novel intermediate-frequency variable-gain amplifier for wideband code-division multiple access transmitters. A compensation technique for parasitic coupling is proposed which allows a high dynamic range of 77 dB to be attained at 400 MHz while using a single variable-gain stage. Temperature compensation and decibel-linear characteristics are achieved by means of a

Francesco Carrara; Carmelo Santagati; Giuseppe Palmisano

2004-01-01

135

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

Microsoft Academic Search

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

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

1997-01-01

136

High-rate spontaneous reversion to cytoplasmic male sterility in sugar beet: a characterization of the mitochondrial genomes  

Microsoft Academic Search

Among the fertile sugar beet lines with nuclear sterility maintenance genes, rf, in a homozygous recessive state, sublines capable of reverting spontaneously at a high rate to sterility were identified. Of 24 related fertile sublines studied, 6 were found to spontaneously revert to sterility with a frequency of about 19%. Genetic analysis confirmed the cytoplasmic nature of spontaneously arising sterility.

N. A. Dudareva; S. G. Veprev; A. V. Popovsky; S. I. Maletsky; I. P. Gileva; R. I. Salganik

1990-01-01

137

Highly reliable & wideband digital multi beamforming horn array antenna with gain adjustment capabilities for space applications  

Microsoft Academic Search

This paper discusses design & measurement techniques for highly reliable & wideband Digital Multi beamforming Horn Array Antenna with gain adjustment capabilities for Space Applications. Complexity of feeding network has been reduced by many folds with the use of 24 dual coaxial fed circularly polarized conical horn antennas providing an excellent axial ratio of <2 dB for entire array highly

Syed Azhar Hasan

2011-01-01

138

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

139

Low pellet gain and high efficiency icf power plant model by MHD power generation  

Microsoft Academic Search

We propose a low pellet gain and high efficiency inertial confinement fusion (ICF) power generation system using a magnetohydrodynamic (MHD) power generation, and employ analytical comparative studies for power generation system options. When the thermal output at high temperature (about 2000–2400K) can be extracted from a fusion reactor, only an MHD generator can be used and can convert efficiently ICF

Takashi Kikuchi; Nob. Harada

2000-01-01

140

Steam flooding gains status as recovery method for heavy, high viscosity crudes  

Microsoft Academic Search

High-pressure steam injection is rapidly gaining status as an accepted successful procedure for increasing the recovery of oil from wells which have been partially depleted by primary production methods. This operation is particularly well adapted to formations which contain low gravity, high viscosity crude oils. Although the first commercially successful application of the technique was in Venezuela's Bolivar Coastal fields,

J. P. Fanaritis; J. D. Kimmel

1965-01-01

141

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

NASA Astrophysics Data System (ADS)

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 (OPA) and optical parametric generation (OPG), have been widely used for near- and mid-infrared light sources. Most such research so far has been demonstrated in bulk crystals. On the other hand, waveguides can enhance the beam intensity along the whole device and significantly increase the gain in parametric processes, and have been widely applied in processes such as second-harmonic generation. However a thorough study of the use of waveguides in high-gain parametric processes is absent. This dissertation addresses he challenges in such applications and demonstrates how waveguide structures and quasi-phase-matching (QPM) gratings can be tailored to improve the performance of high gain parametric processes. We demonstrate high parametric gain for OPA in reverse-proton-exchange lithium niobate waveguides with periodically-poled QPM gratings. Picojoule OPG threshold with picosecond pump pulses near 780 nm is illustrated, which is over two orders of magnitude lower than that in bulk crystal under similar conditions. Furthermore we demonstrate control over the temporal properties of the output products from OPG with picosecond pump pulses near 780 nm. By synthesizing either the QPM gratings or the waveguide structures we demonstrate one order of magnitude smaller time-bandwidth products at designed wavelengths and obtain near transform-limited output from OPG. We also illustrate mode demultiplexing for OPA using asymmetric Y-junctions, in which the signal and idler in different waveguide modes are separated with a contrast of >27.5 dB. The high gain parametric processes in waveguides may therefore find practical application with the engineerable QPM gratings and waveguide structures.

Xie, Xiuping

142

Spontaneous Raman Scattering Diagnostics for High-Pressure Gaseous Flames.  

National Technical Information Service (NTIS)

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 sponta...

J. Kojima Q. V. Nguyen

2002-01-01

143

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

SciTech Connect

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

Kim, K.J.; Pellegrini, C.

1986-05-01

144

A Low-Voltage High-Gain Quadrature Up-Conversion 5GHz CMOS RF Mixer  

NASA Astrophysics Data System (ADS)

A low-voltage quadrature up-conversion CMOS mixer for 5-GHz wireless communication applications is designed with a TSMC 0.18-µm process. The fold-switching technique is used to implement the low-voltage double balanced quadrature mixer. A miniature lumped-element microwave broadband rat-race hybrid and RLC shift network are used for the local oscillator and the intermediate frequency port design, respectively. The measured results demonstrate that the mixer can reach a high conversion gain, a low noise figure (NF), and a high linearity. The mixer exhibits improvement in noise, conversion gain, and image rejection. The mixer shows a conversion gain of 16dB, a noise figure of 12.8dB, an image rejection of 45dB, while dissipating 15.5mW for an operating voltage at 1V.

Liou, Wan-Rone; Yeh, Mei-Ling; Kuo, Sheng-Hing; Lin, Yao-Chain

145

A Low Voltage High Gain Transformer Noise-Canceling Current Mode Ultrawideband CMOS Low Noise Amplifier  

NASA Astrophysics Data System (ADS)

This paper presents a novel current mode differential UWB LNA. A common-gate stage with transformer realizes a low noise input matching and produces a current gain. The output of the LNA is differential current, which can avoid the current-to-voltage conversion. The LNA is simulated with TSMC 0.18 ?m RF CMOS process. Simulation results show that the max noise figure is only 2.65 dB, transconductance gain is larger than 18.7 dB, input reflection coefficient is lower than -9.9 dB, and third order input intercept point is about 2.8 dBm over 3-5 GHz. With a voltage of 0.8 V, the power consumption is 11 mW. A comparison with conventional UWB LNA shows that this LNA has advantages of low voltage, low noise, high gain, and high linearity.

Sun, Jingru; Cao, Xiaodong; Wang, Chunhua; Liu, Jinjiang; Zhao, Manfeng

2012-03-01

146

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

147

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

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

1999-12-17

148

A Novel Compact Tree-Design Antenna (NCTA) with High Gain Enhancement for UWB Application  

Microsoft Academic Search

In this paper, a novel compact tree-design antenna (NCTA) for ultra-wideband (UWB) application with high gain and impedance matching improvement is analyzed and presented. The novel antenna is composed of a single centered circle connected to seven outer circles via three bridges with partial ground plane execution. Instead of functioning as filters, these seven circles play a major role in

M. Jusoh; M. F. Jamlos; M. R. Kamarudin; F. Malek; M. H. Mat; M. A. Jamlos

2011-01-01

149

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

150

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

151

Design and Analysis of Gain-Flattened Raman Amplifiers with Novel Highly Nonlinear Photonic Crystal Fibers  

Microsoft Academic Search

In order to get a flat gain among the dense wavelength division multiplexing (DWDM) channels, design and numerical analysis of Raman fiber amplifier (RFA) based on photonic crystal fibers (PCFs) have been done. Simple pure silica square PCFs with 5 rings air-hole and hexagonal PCFs with 8 rings air- hole owning high nonlinearity, low flat-dispersion as well as low confinement

Dong Wang; Nianyu Zou; Yoshinori Namihira; Yinghai Zhang; Zhe Kang; Jingjing Liu

2011-01-01

152

Role of electron beam temperature in a high gain Compton free-electron laser  

Microsoft Academic Search

Investigated are the effects of longitudinal electron temperature on the eigenmodes of a high gain Compton free-electron laser. It is noted that the electron beam temperature reduces the growth rate by destroying the refractive guiding property of the electron beam.

Y. Seo; E. K. Choi

1999-01-01

153

Artificial magnetic conductor surfaces and their application to low-profile high-gain planar antennas  

Microsoft Academic Search

Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate and they introduce a zero degrees reflection phase shift to incident waves. In this paper the AMC operation of single-layer arrays without vias is studied using a resonant cavity model and a new application to high-gain printed antennas is presented. A ray

Alexandros P. Feresidis; George Goussetis; Shenhong Wang; J. C. Vardaxoglou

2005-01-01

154

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

155

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 {ge} 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. 9 figs.

Biefeld, R.M.; Dawson, L.R.; Fritz, I.J.; Kurtz, S.R.; Zipperian, T.E.

1989-05-12

156

Spontaneous Emission Lifetime of a Single Trapped Ca+ Ion in a High Finesse Cavity  

NASA Astrophysics Data System (ADS)

We investigate the spontaneous emission lifetime of a single trapped 40Ca+ ion placed at different positions in the vacuum standing wave inside a high finesse cavity which is stabilized to the atomic transition. The lifetime is measured by quantum state detection after ?-pulse excitation. The result for the natural lifetime of the D5/2 metastable state of 1161(22)ms agrees, within 1 standard deviation, with the most precise published value. We observe a reduction of the spontaneous emission lifetime of ?15% in the node of the vacuum field.

Kreuter, A.; Becher, C.; Lancaster, G. P.; Mundt, A. B.; Russo, C.; Häffner, H.; Roos, C.; Eschner, J.; Schmidt-Kaler, F.; Blatt, R.

2004-05-01

157

Demonstrating highly symmetric single-mode, single-photon heralding efficiency in spontaneous parametric downconversion.  

PubMed

We demonstrate a symmetric, single-spatial-mode, single-photon heralding efficiency of 84% for a type-II spontaneous parametric downconversion process. High-efficiency, single-spatial mode collection is key to enabling many quantum information processing and quantum metrology applications. PMID:23938885

Cunha Pereira, Marcelo Da; Becerra, Francisco E; Glebov, Boris L; Fan, Jingyun; Nam, Sae Woo; Migdall, Alan

2013-05-15

158

Spontaneous layering of porous silicon layers formed at high current densities  

Microsoft Academic Search

We report here a curious effect of spontaneous fracturing of the silicon layers formed in galvanostatic conditions at medium and high current densities. Instead of formation of homogeneous p-Si layer as at low currents, a stack of thin layers is formed. Each layer is nearly separated from others and possesses rather flat interfaces. The effects is observed using p+-Si wafers

Vitali Parkhutik; Jorge Curiel-Esparza; Mari-Carmen Millan; Jose Albella

2005-01-01

159

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

160

A Zero-Voltage-Switching DC–DC Converter With High Voltage Gain  

Microsoft Academic Search

A zero-voltage-switching (ZVS) dc-dc converter with high voltage gain is proposed. It consists of a ZVS boost converter stage and a ZVS half-bridge converter stage and two stages are merged into a single stage. The ZVS boost converter stage pro- vides a continuous input current and ZVS operation of the power switches. The ZVS half-bridge converter stage provides a high

Hyun-Lark Do

2011-01-01

161

Properties of high gain GaAs switches for pulsed power applications  

SciTech Connect

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

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

1997-09-01

162

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

NASA Astrophysics Data System (ADS)

The multi-pass amplifier (MPA) is the last subsystem of the NIF preamplifier, which feeds the main amplification stages of the NIF beamline. The MPA is based on a flashlamp pumped 5-cm diameter by 48 cm long Nd:glass rod amplifier operated at a single pass small signal gain of 15 to 17. The MPA is an off-axis multi-pass image relayed system, which uses two gain isolating image relaying telescopes and passive polarization switching using a Faraday rotator to output the pulse. We describe the MPA system, techniques used to avoid parasitic oscillation at high gain, and suppression of pencil beams. The system is used to generate a well- conditioned 22-joule output from one millijoule input. The output pulse requirements include 22 joules in a square, flat topped beam, and with near field spatial contrast of <5% RMS, square pulse temporal distortion <2.3, and an RMS energy stability of <3%. All of these requirements have been exceeded. The largest impediment to successful operation was overcoming parasitic oscillation. Sources of oscillation could be generally divided into two categories: those due to birefringence, which compromised the polarization contrast of the system; and those due to unwanted reflections from optical surfaces. Baffling in the vacuum spatial filters helps to control the system sensitivity to unwanted stray reflections from flat AR coated surfaces. Stress birefringence in the rather large glass volume of the rod (942 cm3) and the four vacuum loaded lenses are significant, as each of these elements is double passed between each polarizing beam splitter pass. This lowers the polarization contrast of the system, which can prevent the system from operating at sufficient gain. Careful analysis and layout of the MPA architecture has allowed us to address the challenges posed by a system small signal gain of approximately equals 33000 and with an output pulse of as high as 27 joules.

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

1998-06-01

163

Spontaneous Raman scattering as a high-resolution XUV radiation source  

Microsoft Academic Search

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.

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

1983-01-01

164

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

165

High-power gain-guided InGaAsP laser array  

SciTech Connect

We have fabricated InGaAsP gain-guided laser arrays emitting at 1.3 ..mu..m. These devices have threshold currents in the range 300--400 mA at 30 /sup 0/C and have been operated to pulsed output powers as high as 400 mW. More than 100 mW of output power has been obtained up to an ambient temperature of 60 /sup 0/C. The lasers emit in multilongitudinal modes with a far-field divergence of 20/sup 0/ x 35/sup 0/. A gain-guided InGaAsP laser array of the type described here can be used in some applications requiring high-power lasers emitting at 1.3 ..mu..m.

Dutta, N.K.; Napholtz, S.G.; Wilson, R.B.; Brown, R.L.; Cella, T.; Craft, D.C.

1984-11-01

166

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

SciTech Connect

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 diameter, was used to drive the Al armature into a Cu stator. The initial current supplied by a capacitor bank was approx.3 MA which produced a final current approx.75 MA. Details of the experiment and a comparison with calculations are presented.

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

1986-01-01

167

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

168

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

Microsoft Academic Search

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

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

2011-01-01

169

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

170

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

171

High gain P-band antenna measurements in multi probe spherical near field range  

Microsoft Academic Search

A feed for a compact antenna test range operating in P-band in single polarization has been manufactured and tested in the SATIMO SG-64 multiprobe spherical near field test range in Paris. The feed consist of an array of 4 high gain log-periodic elements. This paper briefly describes the consideration on antenna design and manufacturing and report on the final testing

L. J. Foged; L. Duchesne; A. Rosa; D. Belot; J. M. Lopez

2010-01-01

172

Three-dimensional analysis of harmonic generation in high-gain free-electron lasers  

Microsoft Academic Search

In a high-gain free-electron laser (FEL) employing a planar undulator, strong bunching at the fundamental wavelength can drive substantial bunching and power levels at the harmonic frequencies. In this paper we investigate the three-dimensional evolution of harmonic radiation based on the coupled Maxwell-Klimontovich equations that take into account nonlinear harmonic interactions. Each harmonic field is a sum of a linear

Zhirong Huang; Kwang-Je Kim

2000-01-01

173

Two-dimensional simulation of a high-gain, generalized self-filtering, unstable resonator  

SciTech Connect

The performance of a high-power excimer laser, generalized self-filtering, unstable resonator has been modeled by means of a numerical code. The spectral method and the Rigrod equations are basic to the numerical procedure, which is quite general because it results from an appropriate combination of independent propagation algorithms. The code can be applied to arbitrary resonator geometry and can be used to take account of gain medium inhomogeneities and instability phenomena. {copyright} 1997 Optical Society of America

Torre, A.; Petrucci, C. [Ente per le Nuove Tecnologie, lEnergia e lAmbiente, Dipartimento Innovazione, Settore Fisica Applicata, Centro Ricerche Frascati, P.O. Box 65, 00044 Frascati, Rome (Italy)

1997-04-01

174

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

175

High Gestational Weight Gain Does Not Improve Birth Weight in a Cohort of African American Adolescents  

Microsoft Academic Search

Background: Because pregnant African American women and teensareatriskoflowbirthweight,theyarefrequentlycounseledto strive for gestational weight gains at the upper limits of the Institute of Medicine's recommended ranges. Objective:Theobjectivewastoexaminewhethersuchweightgains improvebirthoutcomesinacohortofdisadvantagedAfricanAmer- ican adolescents of low (19.8), average (19.8 to26.0), or high (26) prepregnancy body mass index (BMI; in kg\\/m2). Design: Data were extracted from the medical charts of 1120 Afri- can American adolescents who received

Jennifer Notkin Nielsen; Frank R. Witter; Shih-Chen Chang; Jeri Mancini; Maureen Schulman Nathanson; Laura E. Caulfield

2006-01-01

176

An Omnidirectional High-Gain Antenna Element for TD-SCDMA Base Station  

Microsoft Academic Search

A novel printed collinear dipole array antenna element is presented. The antenna comprises 8 back-to-back dipole arrays with balanced microstrip as its feed line. It works in the TD-SCDMA band with a good omnidirectional radiation pattern (with variations less than 1 dB) in the horizontal plane and a high gain level of over 9.5dBi. Simulated results obtained by Ansoft HFSS

Yu Xiaole; Ni Daning; Wang Wutu

2006-01-01

177

Adaptive gain equalizer in high-index-contrast SiON technology  

Microsoft Academic Search

An adaptive gain equalization filter is presented. The filter is based on the resonant coupler principle, a cascade of power couplers and delay lines. Reconfigurability and tuning is achieved by varying coupling strength and delay line length via the thermo optic effect. A device consisting of seven delay line stages was realized in high-index-contrast silicon-oxynitride technology. This device flattens the

B. J. Offrein; F. Horst; G. L. Bona; R. Germann; H. W. M. Salemink; R. Beyeler

2000-01-01

178

Statistical theory of high-gain free-electron laser saturation  

Microsoft Academic Search

We propose an approach, based on statistical mechanics, to predict the saturated state of a single-pass, high-gain free-electron laser. In analogy with the violent relaxation process in self-gravitating systems and in the Euler equation of two-dimensional turbulence, the initial relaxation of the laser can be described by the statistical mechanics of an associated Vlasov equation. The laser field intensity and

Julien Barré; Thierry Dauxois; Giovanni de Ninno; Duccio Fanelli

2004-01-01

179

Gain reduction due to space charge at high counting rates in multiwire proportional chambers  

SciTech Connect

Measurements with a small MWPC of gas gain reduction, due to ion space charge at high counting rates, have been compared with theoretical predictions. The quantity ln(q/q/sub 0/)/(q/q/sub 0/), where (q/q/sub 0/) is the relative reduced avalanche charge, has been found to be closely proportional to count rate, as predicted. The constant of proportionality is in good agreement with calculations made with a modified version of the original, simplified theory.

Smith, G.C.; Mathieson, E.

1986-10-01

180

Single ZnO Microrod Ultraviolet Photodetector with High Photocurrent Gain.  

PubMed

An Ag/ZnO microrod/Ag ultraviolet photodetector is fabricated, the ZnO microrod shows a hexagonal whispering gallery cavity structure. Upon a 325 nm ultraviolet illumination, the device shows a high sensitivity of 4 × 10(4) A/W and a high photocurrent gain of 1.5 × 10(5) at 5 V bias. Under different illumination power P, the photocurrent Ilight obeys a power law relation Ilight ? P(0.69). The high performance is probably attributed to a Schottky barrier at Ag/ZnO interface and optical whispering gallery mode effect in the ZnO microrod. PMID:24063658

Dai, Jun; Xu, Chunxiang; Xu, Xiaoyong; Guo, Jiyuan; Li, Jitao; Zhu, Gangyi; Lin, Yi

2013-09-26

181

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

182

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

183

High-gain GaInP\\/GaAs HBT monolithic transimpedance amplifier for high-speed optoelectronic receivers  

Microsoft Academic Search

A self-aligned GaInP\\/GaAs HBT technology was used to develop a monolithic high-gain transimpedance amplifier suitable for optical communication receivers. On-wafer probe measurements revealed a gain (S 21) of 18.8 dB with a bandwidth of 13.5 GHz and input\\/output matching better than -8 dB. The amplifier showed a sensitivity of -15 dBm for 10 Gb\\/s NRZ 27-1 pseudo-random bit sequence with

S. Mohammadi; J. W. Park; D. Pavlidis; C. Dua; J. L. Guyaux; J. C. Garcia

1998-01-01

184

0.7 W X-Ku-band high-gain, high-efficiency common base power HBT  

NASA Astrophysics Data System (ADS)

Small sized AlGaAs-GaAs HBTs (heterojunction bipolar transistors) have achieved excellent power performance throughout the microwave frequency band. With the implementation of the multi-via-hole design, the HBT performance (gain and efficiency) is maintained as the size increases. A 0.7 W common-base (CB) power HBT with performance around 10 dB gain and 50 percent PAE well into the Ku band is reported. The performance is comparable to the pseudomorphic HEMT in this frequency range. The yield and uniformity are excellent. The high bias voltage (9.3 V Vce) is also desirable from a system viewpoint.

Wang, N. L.; Ho, W. J.; Higgins, J. A.

1991-09-01

185

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

186

High gain broadband amplification of ultraviolet pulses in optical parametric chirped pulse amplifier.  

PubMed

We report on a high gain amplification of broadband ultraviolet femtosecond pulses in an optical parametric chirped pulse amplifier. Broadband ultraviolet seed pulses were obtained by an achromatic frequency doubling of the output from a femtosecond Ti:Sapphire oscillator. Stretched seed pulses were amplified in a multipass parametric amplifier with a single BBO crystal pumped by a ns frequency quadrupled Nd:YAG laser. A noncollinear configuration was used for a broadband amplification. The total (after compression) amplification of 2.510(5) was achieved, with compressed pulse energy of 30 microJ and pulse duration of 24 fs. We found that the measured gain was limited by thermal effects induced by the absorption of the pump laser by color centers created in the BBO crystal. PMID:20588633

Wnuk, Pawe?; Stepanenko, Yuriy; Radzewicz, Czes?aw

2010-04-12

187

Optical gain, loss, and transparency current in high performance mid-infrared interband cascade lasers  

NASA Astrophysics Data System (ADS)

The net modal gain, optical loss, and transparency current of high-performance, narrow ridge waveguide interband cascade (IC) lasers have been measured using the Hakki-Paoli technique in the temperature range from T=78 to 270 K. In this temperature range, the optical loss of IC lasers increases from ?w~17 cm-1 at T=78 K to ?w~35 at T=270 K, the transparency current density rises from Itr=10 to 330 A/cm2, and the differential gain decreases from gd~2.2 cm/A to gd~0.06 cm/A with a characteristic temperature of T0=130 K. The implications of these observed characteristics for IC lasers are discussed.

Soibel, Alex; Mansour, Kamjou; Qiu, Yueming; Hill, Cory J.; Yang, Rui Q.

2007-05-01

188

High Pt loadings dispersed on MWCNTs by spontaneous reduction and intermittent microwave heating assisted polyol reduction  

Microsoft Academic Search

This paper reports intermittent microwave heating (IMH) combine with spontaneous is used to prepare highly dispersed Pt\\/FCNTs catalysts. At first, CNTs were functionalized by oxidation of a mixture consisting of H2SO4\\/H2O2 and formed oxygen containing functional groups such as -COOH, -OH, etc., by which the metal ions (Pt4+) were reduced on the sidewalls of FCNTs. X-ray diffraction (XRD) and transmission

Yao Tan; Zi Dong Wei; Yan Lei; Ming Jia Liao

2011-01-01

189

Theory of highly charged ion energy gain spectroscopy of molecular collective excitations  

NASA Astrophysics Data System (ADS)

This paper discusses the physical mechanism by which a highly charged, energetic ion partly neutralized by electron transfers from a target—a large molecule, a cluster or a solid surface—can create target collective excitations in the process. We develop an analysis for the system of a highly charged ion flying by a fullerene molecule. Our analysis offers a new explanation for the periodic oscillations observed in the high-resolution energy gain spectra of energetic Arq+ ions (q=8, 13, 14, 15) flying by C60 molecules. For the Arq+?Ar(q-s)+ spectra with q=13-15 and s=1 or 2, the observed oscillations of 6 eV periodicity are assigned to energy losses due to multiple, Poissonian excitations of C60 ?-plasmons (6 eV quantum). The excitation energy quanta are subtracted from the kinetic energy gained by the ion when one or at most two electrons are transferred to increasingly deep Rydberg states of the ion. The observed 3 eV periodicity for q=8 arises from the specific Rydberg energy levels of ArVIII (Ar7+). The first few shallow levels of this ion are separated by about 3 eV, while some of the pairs of adjacent, deeper levels are also separated by 3 eV. Each deep-level pair produces two interdigitated, Poissonian series of 6 eV ?-plasmon excitation peaks resulting in an apparent periodicity of 3 eV throughout the spectra. The broad ?-plasmons (25 eV quantum) are found to contribute a background continuum to the medium- and high-energy regions of the observed spectra. The physical model analyzed here indicates that electronic collective excitations in several other systems could be studied by highly charged ion energy gain spectroscopy at sufficient resolution.

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

2011-01-01

190

Shuttle Orbiter Ku-Band Radar/Communications System Design Evaluation: High Gain Antenna/Widebeam Horn.  

National Technical Information Service (NTIS)

The physical characteristics of the high gain antenna reflector and feed elements are described. Deficiencies in the sum feed are discussed, and lack of atmospheric venting is posed as a potential problem area. The measured RF performance of the high gain...

R. Iwasaki J. Dodds P. Broad

1979-01-01

191

Moderate Volume of High Relative Training Intensity Produces Greater Strength Gains Compared With Low and High Volumes in Competitive Weightlifters  

Microsoft Academic Search

Gonzalez-Badillo, J.J., M. Izquierdo, and E.M. Gorostiaga. Moderate volume of high relative training in- tensity produces greater strength gains compared with low and high volumes in competitive weightlifters. J. Strength Cond. Res. 20(1)73-81. 2006.—The purpose of this study was to examine the effect of 3 volumes of heavy resistance, average relative training intensity (expressed as a percentage of 1 repetition

Juan José González-Badillo; Mikel Izquierdo; Esteban M. Gorostiaga

2006-01-01

192

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

PubMed

The use of high fructose corn syrup (HFCS) has increased over the past several decades in the United States while overweight and obesity rates have risen dramatically. Some scientists hypothesize that HFCS consumption has uniquely contributed to the increasing mean body mass index (BMI) of the U.S. population. The Center for Food, Nutrition, and Agriculture Policy convened an expert panel to discuss the published scientific literature examining the relationship between consumption of HFCS or "soft drinks" (proxy for HFCS) and weight gain. The authors conducted original analysis to address certain gaps in the literature. Evidence from ecological studies linking HFCS consumption with rising BMI rates is unreliable. Evidence from epidemiologic studies and randomized controlled trials is inconclusive. Studies analyzing the differences between HFCS and sucrose consumption and their contributions to weight gain do not exist. HFCS and sucrose have similar monosaccharide compositions and sweetness values. The fructose:glucose (F:G) ratio in the U.S. food supply has not appreciably changed since the introduction of HFCS in the 1960s. It is unclear why HFCS would affect satiety or absorption and metabolism of fructose any differently than would sucrose. Based on the currently available evidence, the expert panel concluded that HFCS does not appear to contribute to overweight and obesity any differently than do other energy sources. Research recommendations were made to improve our understanding of the association of HFCS and weight gain. PMID:17653981

Forshee, Richard A; Storey, Maureen L; Allison, David B; Glinsmann, Walter H; Hein, Gayle L; Lineback, David R; Miller, Sanford A; Nicklas, Theresa A; Weaver, Gary A; White, John S

2007-01-01

193

COMPARISON OF TWO DIFFERENT WAVELENGTH TUNING SCHEMES IN A SEEDED HIGH-GAIN FEL.  

SciTech Connect

In the following text we analyze and compare results of the two publications ([1], [2]), dedicated to development of the tunable high-gain Free Electron laser (FEL), seeded by an external source. As a conclusion we summarize similarities and differences between these concepts. This note is initiated by the polemics on the similarity of two different schemes of the wavelength tuning in a seeded high-gain FEL. Below we will be calling the scheme, presented by S. Biedron, S, Milton and H. Freund in Nuclear Instruments and Methods of 2001 ([1]), as the first (1st) scheme. The scheme that we developed and presented in the BNL preprint ([2]) will be called as the second (2nd) scheme. The following analysis provides important information on similarities and differences between both techniques. We start by considering the first approach. As we understand, the goal of the Modular Approach is to make X-ray FEL design more flexible [1]. Usual linac-based FELs begin from a long linac with bunch compressor(s) followed by an FEL magnetic system. The essence of the Modular Approach is to break a machine into modules and then recombine these modules in a more efficient way (from the point of view of monetary and/or time constraints). The chapter 3.5 of [1] presents some basic example of Modular Approach. We have studied the scheme, discussed in [1] and illustrated in Fig. 2. Even though very few details of the scheme were presented, it was still sufficient to obtain a complete qualitative picture. Let us begin with the usual phase space of the microbunched beam, which enters a radiator in a prebunched FEL (Fig. 1). The sharp spike (in blue) represents the longitudinal density bunching, which will be the main subject of interest in this discussion. The key principle of a seeded high-gain FEL optimization is to establish this kind of the electron beam phase space at the entrance of the radiator.

SHAFTAN,T.; YU,L.H.

2004-08-04

194

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

195

High-accuracy picosecond characterization of gain-switched laser diodes  

SciTech Connect

A unique combination of the time-correlated photon-counting technique and single-photon avalanche diode detectors gives an accurate characterization of gain-switched semiconductor lasers with picosecond resolution. The high sensitivity and the clean shape of the time response reveal even small features (reflections and relaxation oscillations), making a true optimization of the laser-diode operation possible. The technique outperforms the standard characterization with ultrafast p-i-n photodiodes and a sampling oscilloscope. In addition, compared with other methods, it has favorable features that greatly simplify the measurement.

Cova, S.; Lacaita, A.; Ghioni, M.; Ripamonti, G. (Dipartimento di Elettronica, Politecnico di Milano, Piazza Leonardo da Vinci, 32 Milano, 20133 Italy (IT))

1989-12-15

196

Howling canceling for high gain speakerphone systems exploiting the loudspeaker redundancy  

NASA Astrophysics Data System (ADS)

Howling of an audio amplifying system is annoying, which may occur when a closed-loop is formed for amplified signals. In this paper, we exploit the space diversity offered by the loudspeaker redundancy and develop a new howling canceling approach for high gain speakerphone systems. The amplified waves are weighted at the two loudspeakers to achieve self-cancellation at the microphone after the propagation. As a result, the echo waves can be completely eliminated at the microphone, which avoids any feedback that yields the howling. Results of simulation and hardware test show effectiveness of the method.

Zhang, Jingjing; Yin, Qinye; Mu, Pengcheng; Song, Tianheng; Wang, Wei; Wu, Junchao

2011-10-01

197

EXPERIMENTAL DEMONSTRATION OF WAVELENGTH TUNING IN HIGH-GAIN HARMONIC GENERATION FREE ELECTRON LASER.  

SciTech Connect

Tunability is one of the key aspects of any laser system. In High-Gain Harmonic Generation Free Electron Laser (HGHG FEL) the seed laser determines the output wavelength. Conventional scheme of tunable HGHG FEL requires tunable seed laser. The alternative scheme [1] is based on compression of the electron bunch with energy-time correlation (chirped bunch) in the FEL dispersive section. The chirped energy modulation, induced by the seed laser with constant wavelength, compressed as the whole bunch undergoes compression. In this paper we discuss experimental verification of the proposed approach at the DUV FEL [2,3] and compare experimental results with analytical estimates.

SHAFTAN,T.; JOHNSON,E.; KRINSKY,S.; LOOS,H.; MURPHY,J.B.; RAKOWSKY,G.; ROSE,J.; SHEEHY,B.; SKARITKA,J.; WANG,X.J.; WU,Z.; YU,L.H.

2004-08-29

198

Effect of crystal-field split-off hole and heavy-hole bands crossover on gain characteristics of high Al-content AlGaN quantum well lasers  

NASA Astrophysics Data System (ADS)

The optical gain characteristics of high Al-content AlGaN quantum wells (QWs) are analyzed for deep UV lasers. The effect of crystal-field split-off hole (CH) and heavy-hole (HH) bands crossover on the gain characteristics of AlGaN QW with AlN barriers is analyzed. Attributing to the strong transition between conduction-CH bands, the TM spontaneous emission recombination rate is enhanced significantly for high Al-content AlGaN QWs. Large TM-polarized material gain is shown as achievable for high Al-content AlGaN QWs, which indicates the feasibility of TM lasing for lasers emitting at ~220-230 nm.

Zhang, Jing; Zhao, Hongping; Tansu, Nelson

2010-09-01

199

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

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

1997-08-01

200

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

201

High gain-bandwidth-product avalanche photodiodes for multigigabit/s data rates  

NASA Astrophysics Data System (ADS)

For long-wavelength (1.3 ?m and 1.5 ?m) high-bit-rate (>~400 Mbit/s) lightwave systems the highest receiver sensitivities have been achieved with III-V compound avalanche photodiodes with separate absorption and multiplication regions (SAM-APDs). Initial APDs of this type exhibited poor frequency response owing to charge accumulation at the heterojunction interfaces. A significant improvement in the bandwidth was achieved by introducing a transition region between the multiplication and absorption layers (SAGM-APDs). Early SAGM-APDs exhibited bandwidths in the range 1 GHz to 3 GHz and gain-bandwidth products as high as 18 GHz. Recently, the progression of new lightwave systems to higher and higher bit rates has stimulated efforts to further increase the bandwidth of these SAGM-APDs. By optimizing the design parameters bandwidths as high as 5 GHz and 7 GHz and gain-bandwidth products of 50 GHz and 60 GHz have been reported for planar and mesa structures, respectively. The improved frequency response of these APDs has contributed to the success of lightwave systems experiments at 2 Gbit/s, 4 Gbit/s, and 8/Gbit/s.

Campbell, J. C.

1987-09-01

202

Insidious weight gain in prepubertal seized rats treated with an atypical neuroleptic: the role of food consumption, fluid consumption, and spontaneous ambulatory activity.  

PubMed

Extreme obesity slowly develops in female rats over the months following seizures induced by a single systemic injection of lithium and pilocarpine if the resulting limbic seizures are treated with the atypical neuroleptic acepromazine (but not with ketamine). To discern the contributions from food consumption, water consumption, and (daytime and nighttime) activity to this weight gain, these behaviors were monitored for 4 months, about 2 months after seizure induction. The results indicated that the rats that underwent the obesity procedure exhibited 50% heavier body weights and consumed 42% more food than the reference group, which included rats that had been induced to seize but treated with ketamine. There were no statistically significant differences between groups with respect to either water consumption or (daytime or nighttime) activity. Factor analyses of data for individual rats verified the dissociation between activity and weight gain for the obese rats. The results suggest that the progressive weight gains are centrally mediated and are not secondary to diminished activity or altered fluid consumption. PMID:19110073

St-Pierre, L S; Bubenik, G A; Parker, G H; Persinger, M A

2008-12-25

203

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

NASA Astrophysics Data System (ADS)

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

Robinson, S. M.; Kiff, S. D.; Ashbaker, E. D.; Flumerfelt, E.; Salvitti, M.

2009-11-01

204

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

205

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

206

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

207

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

208

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

SciTech Connect

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

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

2009-11-01

209

Feasibility of high pressure operation and determination of the optimum gain zone in chemical oxygen-iodine lasers  

SciTech Connect

Use is made of a simple model to theoretically prove that there exist optimum values for small signal gains in chemical Oxygen-Iodine lasers dependent on overall system oxygen pressures. At the same time, the feasibility of chemical oxygen-iodine laser operations under high pressure is discussed. Finally, methods for determining optimum gain zones for chemical oxygen-iodine lasers are given.

Li, F.

1995-11-29

210

A comparative study of the spontaneous social interactions of children with high-functioning autism and children with Asperger's disorder  

Microsoft Academic Search

A comparative observational study was undertaken of the spontaneous social interactions of children with high-functioning autism and Asperger's disorder. The sample comprised 20 children with high-functioning autism, 19 children with Asperger's disorder and 17 typically developing children matched on chronological age and overall mental age. A one–zero time sampling technique was used in live coding of the children's spontaneous social

Kathleen Macintosh; Cheryl Dissanayake

2006-01-01

211

A high gain-bandwidth product transimpedance amplifier for MEMS-based oscillators  

Microsoft Academic Search

A variable gain differential transimpedance amplifier (TIA) optimized for MEMS-based oscillator applications is presented. The TIA achieves a variable gain of 17 kOmega to 290 kOmega, i.e. a gain range of 25 dB. The 3-dB bandwidths corresponding to these gains are 256 MHz and 103 MHz, respectively. The suitability of the TIA for the targeted application is demonstrated by combining

F. Nabki; M. N. El-Gamal

2008-01-01

212

A 30 GHz Variable Gain Amplifier With High Output Voltage Swing for Ultra-Wideband Radar  

Microsoft Academic Search

This paper reports on the analysis, design and characterization of a 30 GHz fully differential variable gain amplifier for ultra-wideband radar systems. The circuit consists of a variable gain differential stage, which is fed by two cascaded emitter followers. Capacitive degeneration and inductive peaking are used to enhance bandwidth. The maximum differential gain is 11.5 dB with plusmn1.5 dB gain

Benjamin Sewiolo; Georg Fischer; Robert Weigel

2009-01-01

213

A novel design for high gain lens antennas with homogeneous media  

NASA Astrophysics Data System (ADS)

A high gain lens antenna is designed by using a new transformation different from the discrete optical transformation. The antenna is composed of two blocks. Each block is made of homogenous and anisotropic materials, and thus can be easily achieved by metamaterial. The numerical results based on full wave simulation indicate that the antenna can be used to realize highly directive radiation beam, and the direction of radiation beam can be controlled artificially by changing the geometry parameters of the device. The electromagnetic field in the transformation region can be either stretched or compressed along both transverse and longitudinal directions by varying the geometry parameters in the virtual space while the distribution of electromagnetic field outside the antenna is little influenced. Moreover, effective medium theory is applied to realize such an antenna with isotropic materials. Also, the multi-beams antenna is investigated. It is indicated that this antenna can generate multi-collimated beams radiating at the desired angles.

Huang, Lujun; Wang, Ziqian; Zhou, Shutong; Li, Guanhai; Ni, Bo; Wang, Xiaofang; Li, Zhifeng; Chen, Xiaoshuang; Lu, Wei

2012-10-01

214

Vertical organic triodes with a high current gain operated in saturation region  

NASA Astrophysics Data System (ADS)

The authors report the fabrication of vertical organic triodes operated in the pronounced saturation regions by using two back-to-back pentacene Schottky diodes. The device with an optimized 0.7 nm LiF hole injection enhancement layer and a 70 nm pentacene emitter can achieve an ultrahigh common-emitter current gain of 48 in the saturation region at a low applied voltage VCE of -4 V and a base current density of 0.25 mA/cm2. In addition, the device exhibits a high output current density of 12.1 mA/cm2 and a high on/off current ratio of 103.

Yang, Chuan-Yi; Ou, Tzu-Min; Cheng, Shiau-Shin; Wu, Meng-Chyi; Lin, Shih-Yen; Chan, I.-Min; Chan, Yi-Jen

2006-10-01

215

Visual tracking control for stereo vision robot with high gain controller and high speed cameras  

Microsoft Academic Search

The paper reports the visual tracking control to a fast moving object for stereo vision robot with using high speed cameras. The tracking delay due to the target motion should be suppressed with several approaches; adoption of the advanced control techniques, adjustment of the controller parameters, introduction of high-performance vision systems, and so on. In this paper, the ways adopting

Masaaki Shibata; Hideki Eto; Masahide Ito

2011-01-01

216

High gain GaAs switches for impulse sources: Measurement of the speed of current filaments  

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 ohm 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 authors have demonstrated that the GaAs switches can be used to produce either a monocycle or a monopulse with a period of 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 ohm 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. This experiment also shows a relationship between the rise time of the voltage across the switch and the required trigger energy and switch jitter. The time evolution of the current filaments in an optically triggered, high gain GaAs switch was studied by recording the infrared photoluminescence from the filaments. When the system is triggered with two laser diode arrays that are activated within 1 ns of each other, two current filaments are observed. By delaying one laser with respect to the other, the evolution of the filament was recorded in a time resolved fashion. The filament that is triggered first crosses the switch, the voltage drops and the other filament ceases to grow. By varying the delay between the trigger lasers, the tip velocity is measured to be up to 5.9 {+-} 1 {times} 10{sup 9} cm/s.

Loubriel, G.M.; Zutavern, F.J.; O`Maliey, M.W.; Gallegos, R.R.; Helgeson, W.D.; Hjalmarson, H.P.; Baca, A.G.; Plut, T.A.

1994-07-01

217

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

SciTech Connect

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

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

1988-01-01

218

Amplified spontaneous emission in an organic semiconductor multilayer waveguide structure including a highly conductive transparent electrode  

NASA Astrophysics Data System (ADS)

We demonstrate that the amplified spontaneous emission (ASE) threshold in multilayer waveguide structures suitable for the use in future organic injection lasers can be drastically reduced by inserting a crosslinked hole transport layer (HTL) between a highly conductive indium tin oxide (ITO) electrode and the polymer emission layer. While no ASE is observed when the active layer material is directly spincoated onto the ITO electrode, it can be completely restored upon insertion of a 300-nm-thick HTL. This observation is attributed to reduced attenuation of the waveguided mode enabling the ASE process and is theoretically confirmed by calculations of the mode intensity fraction propagating in the absorptive ITO electrode.

Reufer, M.; Feldmann, J.; Rudati, P.; Ruhl, A.; Müller, D.; Meerholz, K.; Karnutsch, C.; Gerken, M.; Lemmer, U.

2005-05-01

219

A new L-band, high gain TWT for high performance aircraft requirements  

Microsoft Academic Search

A traveling-wave tube which can meet rigid specifications with regard to performance and durability at high ambient temperatures has been developed. Designed for L band, this tube (the STL-70) is of all metal and ceramic construction with an extremely rigid gun structure capable of being processed at temperatures exceeding 600°C. This tube has a novel input and output match which

W. W. Menke; L. Dombro

1957-01-01

220

Diffractive optical elements for high gain lasers with arbitrary output beam profiles.  

PubMed

We introduce a previously unreported laser cavity configuration, using a diffractive optical element (DOE) in place of the output coupler. Such a configuration allows the DOE to work both in reflection, as a mode shaping element, and in transmission as a beam shaper. Employing dual wavelength DOE optimization techniques and phase delays greater than 2pi, allows the two functions to be designed independently. Thus, an arbitrary output beam profile can be combined with a mode shape which maximizes energy extraction from the gain medium. Devices are designed and their performance modeled for a 1m cavity with 5mm diameter mirrors and a wavelength of 632.8nm. An element with 32 quantization levels and a maximum phase delay of 8pi in transmission produces high quality results. PMID:19547424

Caley, Adam J; Thomson, Martin J; Liu, Jinsong; Waddie, Andrew J; Taghizadeh, Mohammad R

2007-08-20

221

Suppression of higher mode excitation in a high gain relativistic klystron amplifier  

NASA Astrophysics Data System (ADS)

Suppressing higher mode excitation is very important in the high gain relativistic klystron amplifier because higher mode can seriously degrade klystron performance and cause pulse shortening. The mechanism of higher mode self-excitation is explored in the PIC simulation, and it is shown the coupling between cavities is the main cause of higher mode self-excitation. The coupling forms the positive feedback loop for higher mode to be excited just like that in the oscillator circuit. The formula for startup current of higher mode self-excitation is developed based on the coupling between cavities. And the corresponding methods are taken to avoid higher mode self-excitation. Finally, mode control is realized in the RKA with output power up to 1.02 GW when driven power is only few kilowatts.

Wu, Y.; Xu, Z.; Jin, X.; Li, Z. H.; Tang, C. X.

2012-02-01

222

A high gain free electron laser amplifier design for the Alcator-C tokamak. [FRED  

SciTech Connect

We describe an improved wiggler tapering algorithm and the resulting wiggler design for a high-gain free electron laser amplifier to be used for plasma heating and current drive experiments in the Alcator-C tokamak. Unlike the original, this new design limits the growth of the shot noise to insignificant levels. The design goal of at least 8 GW of peak power in the TE/sub 01/ mode was achieved with a 3 kA electron beam with energies in the 7 to 9 MeV range and a beam brightness of 10/sup 5/ A/(rad-cm)/sup 2/. The wiggler was 5 m long with a wiggler wavelength of 8 cm.

Jong, R.A.

1987-02-01

223

A high gain patch fed horn antenna for millimeter wave imaging receiver  

NASA Astrophysics Data System (ADS)

In this paper, antennas that combine transitions from microstrip line / coplanar waveguide (CPW) to horn antenna in a single unit are presented. Conventional single layer microstrip patch antennas inherently suffer narrow operation bandwidth; to widen the frequency bandwidth, stacked patch antennas are used and high gain is achieved from the horn antenna. Here, microstrip line / CPW directly feeds the bottom patch while the top patch couples parasitically to the bottom patch. For -10 dB return loss, 25% bandwidth is achieved for both microstrip line to horn antenna (MSLTHA) at center frequency f0=17.5 GHz and for CPW to horn antenna (CPWTHA) at f0=97 GHz. The designs were optimized using 3D Finite Element Method (FEM) software HFSS by Ansoft Corporation. The optimal design of MSLTHA has been fabricated and characterized. The return loss and far field radiation pattern are measured and has been found in very good agreement with the simulation results.

Shireen, Rownak; Hwang, Timothy; Shi, Shouyuan; Prather, D. W.

2005-11-01

224

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

225

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

226

Dietary calcium attenuation of body fat gain during high-fat feeding in mice.  

PubMed

Human epidemiological studies have supported the hypothesis that a dairy food-rich diet is associated with lower fat accumulation, although prospective studies and intervention trials are not so conclusive and contradictory data exist in animal models. The purpose of this study was to assess the effects on body weight and fat depots of dairy calcium (12 g/kg diet) in wild-type mice under ad libitum high-fat (43%) and normal-fat (12%) diets and to gain comprehension on the underlying mechanism of dairy calcium effects. Our results show that calcium intake decreases body weight and body fat depot gain under high-fat diet and accelerates weight loss under normal-fat diet, without differences in food intake. No differences in gene or protein expression of UCP1 in brown adipose tissue or UCP2 in white adipose tissue were found that could be related with calcium feeding, suggesting that calcium intake contributed to modulate body weight in wild-type mice by a mechanism that is not associated with activation of brown adipose tissue thermogenesis. UCP3 protein but not gene expression increased in muscle due to calcium feeding. In white adipose tissue there were effects of calcium intake decreasing the expression of proteins related to calcium signalling, in particular of stanniocalcin 2. CaSR levels could play a role in decreasing cytosolic calcium in adipocytes and, therefore, contribute to the diminution of fat accretion. Results support the anti-obesity effect of dietary calcium in male mice and indicate that, at least at the time-point studied, activation of thermogenesis is not involved. PMID:17588736

Parra, Pilar; Bruni, Giovanni; Palou, Andreu; Serra, Francisca

2007-06-25

227

High-gain wide-viewing-angle null-hot-spot optical diffuser useful for display screen application  

Microsoft Academic Search

A high-gain, wide-viewing-angle optical diffuser without hot spots is presented. Such type of optical diffuser has potential applications in front and rear projection screens, LED display illumination, LCD backlights, beam homogenizer, etc. By shaping the diffused light pattern to be elliptical, high-gain is achieved by narrowing and thus enhancing 1D intensity distribution while the other dimension satisfies the wide-viewing-angle requirement.

Hoang Yan Lin; Wann-Diiang Tyan; Ying-Tsung Lu

1996-01-01

228

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

SciTech Connect

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

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

2000-07-01

229

Simulated high altitude selectively decreases protein intake and lean mass gain in rats.  

PubMed

The aim of this study was to find out whether high altitude (HA)-induced hypophagia was macronutrient-specific using a self-selection procedure. Body composition was assessed by dual X-ray absorptiometry before and after exposure and by dissection at the end of the experiment. Energy intake, macronutrient selection, body composition, plasma insulin and leptin concentrations were measured in rats (FHx) exposed 16 h daily for 10 days to hypobaric hypoxia (HH) simulating an altitude of 5500 m. Rats were fasted during the exposure to HH and had access to food only during the 8 h of normoxia in their active period. This group was compared to control group (C) with ad libitum access to food and a group of rats submitted only to the 16-h fast (FNx). Results showed that sustained hypophagia was specific to protein (55 +/- 5% of C, P < .05), whereas after a decline, carbohydrate intake reached its basal level on the 5th day. HH dramatically reduced fat-free mass gain (P < .05 and P < .0001 compared to C and FNx, respectively). Plasma leptin concentrations at the onset of the period of access to food were not significantly different from those of controls. Across groups, leptin was positively correlated with fat mass (r = .71, P < .001) and negatively with energy intake (r = -.52, P < .05), more specifically with protein intake (r = -.57, P < .05). These results suggest that HA leads to a reduced preference for protein impairing fat-free mass gain and that leptin may contribute to this hypophagia. PMID:16139314

Morel, Olivier E; Aubert, Roberte; Richalet, Jean-Paul; Chapelot, Didier

2005-09-15

230

A high linearity multi-band and gain adjustable channel-select filter for TV-tuner application  

NASA Astrophysics Data System (ADS)

This paper presents a channel-select filter that employs an active-RC bi-quad structure for TV-tuner application. A design method to optimize the IIP3 of the bi-quad is developed. Multi-band selection and gain adjustment are implemented using switching resistors in the resistor array and capacitors in the capacitor array. Q-factor degradation is compensated by a tuning segmented resistor. A feed-forward OTA with high gain and low third-order distortion is applied in the bi-quad to maximize linearity performance and minimize area by avoiding extra compensation capacitor use. An RC tuning circuit and DC offset cancellation circuit are designed to overcome the process variation and DC offset, respectively. The experimental results yield an in-band IIP3 of more than 31 dBm at 0 dB gain, a 54 dB gain range with 6 dB gain step, and a continuous frequency tuning range from 0.25 to 4 MHz. The in-band ripple is less than 1.4 dB at high gain mode, while the gain error and frequency tuning error are no more than 3.4% and 5%, respectively. The design, which is fabricated in a 0.18 ?m CMOS process, consumes 12.6 mW power at a 1.8 V supply and occupies 1.28 mm2.

Xin, Wang; Tao, Cheng; Jie, Liu; Zhangwen, Tang

2013-09-01

231

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

PubMed

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

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

2005-01-13

232

Experimental characterization of superradiance in a single-pass high-gain laser-seeded free-electron laser amplifier.  

PubMed

In this Letter we report the first experimental characterization of superradiance in a single-pass high-gain free-electron laser (FEL) seeded by a 150 femtosecond (FWHM) Ti:sapphire laser. The nonlinear energy gain after an exponential gain regime was observed. We also measured the evolution of the longitudinal phase space in both the exponential and superradiant regimes. The output FEL pulse duration was measured to be as short as 81 fs, a roughly 50% reduction compared to the input seed laser. The temporal distribution of the FEL radiation as predicted by a numerical simulation was experimentally verified for the first time. PMID:17358688

Watanabe, T; Wang, X J; Murphy, J B; Rose, J; Shen, Y; Tsang, T; Giannessi, L; Musumeci, P; Reiche, S

2007-01-19

233

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

PubMed Central

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 6 mo and then tested for leptin resistance. Half of the rats in each group were then switched to high-fat diet for 2 wk, 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-h food intake in the fructose-free group (73.7 ± 6.3 vs. 58.1 ± 8 kcal, P = 0.02) but had no effect in fructose-fed rats (71.2 ± 6.6 vs. 72.4 ± 6.4 kcal, P = 0.9). Absence of anorexic response to intraperitoneal leptin injection was associated with 25.7% decrease in hypothalamic signal transducer and activator of transcription 3 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 led to exacerbated weight gain (50.2 ± 2 g) compared with correspondingly fed leptin-responsive animals that were pretreated with the fructose-free diet (30.4 ± 5.8 g, P = 0.012). Our data indicate that chronic fructose consumption induces leptin resistance prior to body weight, adiposity, serum leptin, insulin, or glucose increases, and this fructose-induced leptin resistance accelerates high-fat induced obesity.

Shapiro, Alexandra; Mu, Wei; Roncal, Carlos; Cheng, Kit-Yan; Johnson, Richard J.; Scarpace, Philip J.

2008-01-01

234

Gain measurements and high resolution spectroscopy of the 546.1 nm atomic mercury laser transition  

Microsoft Academic Search

An investigation of the gain of a CW atomic mercury laser using a tunable dye laser is reported. Several isotopes are seen to be simultaneously excited and found to lase in multiple isotope mixtures. The nitrogen pressure dependence of the gain is found to be in good agreement with rate equation analyses, provided a pressure dependent loss term due to

S. M. Skippon; T. A. King; M. D. Rabbett

1983-01-01

235

Optimization of a Broadband Gain Element for a Widely Tunable High-Power Semiconductor Disk Laser  

Microsoft Academic Search

The layer structure of the gain element in an optically pumped semiconductor disk laser was parametrically optimized with respect to a target function specifying a desired unsaturated reflectance over a desired wavelength range at a constant pump intensity. Spectral threshold pump intensity measurements confirmed the efficacy of the design, showing a much wider low-threshold regime than a conventional nonbroadband gain

Carl Borgentun; Jörgen Bengtsson; Anders Larsson; Frank Demaria; Alexander Hein; Peter Unger

2010-01-01

236

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

237

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

SciTech Connect

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

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

1987-06-08

238

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

SciTech Connect

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

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

1996-10-01

239

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

240

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

Microsoft Academic Search

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

Jae H. Kim; Steven H. Lin

1991-01-01

241

A low-power high-gain transresistance BiCMOS pulse amplifier for capacitive detector readout  

Microsoft Academic Search

A low-power, high-gain amplifier for detector readout is discussed. The amplifier is balanced, fully differential in circuit topology, and symmetrical in layout, making it radiation tolerant and relatively insensitive to varying magnetic fields in the large detector. Before irradiation, the circuit has a measured differential gain of 110 mV\\/4 fC, an average 10\\/90% rise time t10\\/90% of 19 ns, a

Johan Wulleman

1997-01-01

242

High-dynamic-range decibel-linear IF variable-gain amplifier with temperature compensation for WCDMA applications  

Microsoft Academic Search

This paper presents the design and simulated performance of a novel intermediate-frequency variable-gain amplifier for Wideband Code-Division Multiple Access transmitters. A compensation technique for parasitic coupling is proposed which allows the very high dynamic range of 85 dB to be attained using a single variable-gain stage. Temperature compensation and decibel-linear control are achieved by means of a proper bias network

Francesco Carrara; Pietro Filoramo; Giovanni Palmisano

2003-01-01

243

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

244

Limiting high-frequency hearing aid gain in listeners with and without suspected cochlear dead regions.  

PubMed

The purpose of this study was to compare threshold-matched ears with and without suspected cochlear dead regions in terms of the speech perception benefit from high-frequency amplification. The Threshold Equalizing Noise Test (TEN) was used to assess the presence of dead regions. Speech perception was measured while participants were wearing a hearing aid fit to approximate DSL[i/o] targets. Consonant identification of nonsense vowel-consonant-vowel combinations was measured in quiet using a forced-choice procedure. Phoneme recognition was measured at signal-to-noise ratios ranging from 0 to +15 dB using the Computer-Assisted Speech Perception Assessment test (CASPA). Recognition scores were obtained for unfiltered stimuli and stimuli that were low-pass filtered at the estimated boundary of the suspected dead regions, 1/2 octave above and 1 octave above the boundary. Filter settings for the ears without suspected dead regions were the same as settings of the threshold-matched counterpart. In quiet and in low levels of noise, speech perception scores were significantly higher for the wide-band (unfiltered) condition than for the filtered conditions, and performance was similar for the ears with and without suspected dead regions. In high levels of noise, mean scores were highest in the wide-band condition for the ears without suspected dead regions, but performance reached an asymptote for the ears with suspected dead regions. These results suggest that patients with cochlear dead regions may experience speech perception benefit from wide-band high-frequency gain in quiet and low levels of noise, but not in high levels of noise. PMID:15484599

Mackersie, Carol L; Crocker, Tracy L; Davis, Rebecca A

245

Prospects for high-gain, high yield National Ignition Facility targets driven by 2(omega) (green) light  

SciTech Connect

The National Ignition Facility (NIF), operating at green (2{omega}) light, has the potential to drive ignition targets with significantly more energy than the 1.8 MJ it will produce with its baseline, blue (3{omega}) operations. This results in a greatly increased 'target design space', providing a number of exciting opportunities for fusion research. These include the prospect of ignition experiments with capsules absorbing energies in the vicinity of 1 MJ. This significant increase in capsule absorbed energy over the original designs at {approx}150 kJ could allow high-gain, high yield experiments on NIF. This paper reports the progress made exploring 2{omega} for NIF ignition, including potential 2{omega} laser performance, 2{omega} ignition target designs and 2{omega} Laser Plasma Interaction (LPI) studies.

Suter, L J; Glenzer, S; Haan, S; Hammel, B; Manes, K; Meezan, N; Moody, J; Spaeth, M; Divol, L; Oades, K; Stevenson, M

2003-12-16

246

High-intensity resistance training amplifies muscle hypertrophy and functional gains in persons with Parkinson's disease.  

PubMed

Strength deficits in persons with Parkinson's disease (PD) have been identified as a contributor to bradykinesia. However, there is little research that examines the effect of resistance training on muscle size, muscle force production, and mobility in persons with PD. The purpose of this exploratory study was to examine, in persons with PD, the changes in quadriceps muscle volume, muscle force production, and mobility as a result of a 12-week high-force eccentric resistance training program and to compare the effects to a standard-care control. Nineteen individuals with idiopathic PD were recruited and consented to participate. Matched assignment for age and disease severity resulted in 10 participants in the eccentric group and 9 participants in the control group. All participants were tested prior to and following a 12-week intervention period with testing and training conducted at standardized times in their medication cycle. The eccentric group performed high-force quadriceps contractions on an eccentric ergometer 3 days a week for 12 weeks. The standard-care group exercise program encompassed standard exercise management of PD. The outcome variables were quadriceps muscle volume, muscle force, and mobility measures (6-minute walk, stair ascent/descent time). Each outcome variable was tested using separate one-way analyses of covariance on the difference scores. Muscle volume, muscle force, and functional status improvements occurred in persons with PD as a result of high-force eccentric resistance training. The eccentric group demonstrated significantly greater difference scores for muscle structure, stair descent, and 6-minute walk (P < 0.05). Magnitude of effect size estimators for the eccentric group consistently exceeded those in the standard-care group for all variables. To our knowledge, this is the first clinical trial to investigate and demonstrate the effects of eccentric resistance training on muscle hypertrophy, strength, and mobility in persons with PD. Additional research is needed to determine the anatomical and neurological mechanisms of the observed strength gains and mobility improvements. PMID:16773643

Dibble, Leland E; Hale, Tessa F; Marcus, Robin L; Droge, John; Gerber, J Parry; LaStayo, Paul C

2006-09-01

247

High-gain microstrip gas counters for soft X-ray detection  

NASA Astrophysics Data System (ADS)

This study describes development work in which systematic changes in the pitch of the electrode pattern of a Microstrip Gas Counter (MSGC) are explored in the search for higher gas gains and enhanced stability. We investigated the gas gain, soft X-ray energy resolution and the detector noise with pitch values set between 300?m and 1200?m. With the cathode width set to half of the pitch and anode width at 5?m, gas gains exceeding 50,000 were comfortably achieved. We present the optimised MSGC geometry which permits radiation detection in the sub-keVX-ray region.

Bateman, J. E.; Barlow, R.; Derbyshire, G. E.; Mir, J. A.; Stephenson, R.

2003-11-01

248

The spontaneous generation of magnetic fields at high temperature in a supersymmetric theory  

NASA Astrophysics Data System (ADS)

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the minimal supersymmetric standard model is investigated. The consistent effective potential including the one-loop and the daisy diagrams of all bosons and fermions is calculated and the magnetization of the vacuum is observed. The mixing of the generated fields due to the quark and s-quark loop diagrams and the role of superpartners are studied in detail. It is found that the contribution of these diagrams increases the magnetic and chromomagnetic field strengths as compared with the case of a separate generation of fields. The magnetized vacuum state is found to be stable due to the magnetic masses of gauge fields included in the daisy diagrams. Applications of the results obtained are discussed. A comparison with the standard model case is given.

Demchik, V. I.; Skalozub, V. V.

2003-04-01

249

Microlens array-based high-gain screen design for direct projection head-up displays.  

PubMed

Head-up display (HUD) systems have been used in recent car models to provide essential information to the drivers while keeping their eyes on the road. Virtual image HUD systems have been the preferred method, but they have the drawback of requiring a large volume of space in order to accommodate the relay optics that creates the virtual image. This is especially significant as the desired field of view increases. Direct projection HUD systems have been developed with a separate stand-alone microlens array (MLA)-based transparent screen on the dashboard, offering a compact solution. In this paper, we propose a direct projection HUD system based on a unique, windshield-embedded see-through screen that uses minimal space under the dashboard, offering an elegant and compact solution to the HUD problem. The screen is based on MLAs with varying surface normal angles such that the light from the projector is directed to the viewer's eyes from all positions across the field of view. Varying tilts provide an efficient relay and high brightness even with a low-lumen output projector. The calculated screen gain is about 69 and the eyebox area is about 30 cm×30 cm. PMID:23435009

Hedili, M Kivanc; Freeman, Mark O; Urey, Hakan

2013-02-20

250

High gain GaAs photoconductive semiconductor switches: Measurement of filament velocity and reduced trigger energy  

SciTech Connect

The time evolution of the current filaments in an optically triggered, high gain GaAs switch was studied by recording the infrared photoluminescence from the filaments. When the switch is triggered with two laser diode arrays (through a fiber optic) that are activated within 1 ns of each other, two current filaments are observed, each one emanating from the point of illumination. By delaying one laser with respect to the other, the evolution of the filament was recorded in a time resolved fashion. The first filament that is triggered crosses the switch, the voltage drops and the other filament ceases to grow. By varying the delay between the trigger lasers, the tip velocity is measured to be up to 5.9 {plus_minus} 1 {times} 10{sup 9} cm/s. This speed is 600 times larger than the peak drift velocity of carriers in GaAs. This observation supports switching models that rely on carrier generation at the tip of the filament. The filaments speed up as they cross the switch: for one voltage range initial speeds were 0.7 {plus_minus} 1 {times} 10{sup 9} cm/s and final speeds (the last 100 ps of motion) exceed 5.5 {plus_minus} 1 {times} 10{sup 9} cm/s. 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.; Helgeson, W.D.

1994-11-01

251

Mode splitting and the coherent instability in high-gain lasers  

SciTech Connect

A high-gain continuous-wave laser may exhibit an output instability in the form of a periodic pulse train or chaotic signal. In the time domain, the instability is interpreted as resulting from the inability of the medium's polarization to respond quickly enough to perturbations in the optical field of the cavity. In the frequency domain, it can be interpreted as arising from the splitting of a single longitudinal mode into several oscillating lines, each of which satisfies the same cavity resonance condition as the original mode. We show that the mode-splitting interpretation of the instability yields a new understanding of the complex behavior reported in xenon, helium--xenon, and helium--neon lasers. The fundamental frequencies of the instability and the possibility of chaotic output are shown to be consistent with unequally spaced resonant modes that arise close to the laser threshold. With saturation, nonresonant harmonics of the fundamental frequencies appear in the laser output. These harmonics have fixed phases relative to the resonant modes and lead to the complex asymmetries of the pulse shapes. Interaction between the resonant and nonresonant modes can trigger period doubling in the pulse train.

Minden, M.L.; Casperson, L.W.

1985-01-01

252

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

253

Time-resolved study of Raman gain in highly confined silicon-on-insulator waveguides  

NASA Astrophysics Data System (ADS)

We show time-resolved measurement of Raman gain in Silicon submicron-size planar waveguide using picosecond pump and probe pulses. A net nonlinear gain of 6 dB is obtained in a 7-mm long waveguide with 20.7-W peak pump power. We demonstrate an ultrafast all-optical switch based on the free-carrier dispersion effect in the silicon waveguide, whose transmission is enhanced by more than 13 dB due to the Raman effect.

Xu, Qianfan; Almeida, Vilson R.; Lipson, Michal

2004-09-01

254

Role of neutral base recombination in high gain AlGaAs\\/GaAs HBT's  

Microsoft Academic Search

Neutral base recombination is a limiting factor controlling the maximum gain of AlGaAs\\/GaAs HBT's with base sheet resistances between 100 and 350 ?\\/□. In this work, we investigate five series of AlGaAs\\/GaAs HBT growths in which the base thickness was varied between 500 and 1600 Å and the base doping level between 2.9× and 4.7×1019 cm-3. The dc current gain

Roger E. Welser; Noren Pan; Duy-Phach Vu; Peter J. Zampardi; Brian T. McDermott

1999-01-01

255

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

2013-03-29

256

High-gain Al2O3:Nd3+ channel waveguide amplifiers at 880 nm, 1060 nm, and 1330 nm  

NASA Astrophysics Data System (ADS)

Neodymium-doped aluminum oxide films with a range of Nd3+ concentrations are deposited on silicon wafers by reactive co-sputtering, and single-mode channel waveguides with various lengths are fabricated by reactive ion etching. Photoluminescence at 880, 1060, and 1330 nm from the Nd3+ ions with a lifetime of 325 ?s is observed. Internal net gain at 845-945 nm, 1064, and 1330 nm is experimentally and theoretically investigated under continuous-wave excitation at 802 nm. Net optical gain of 6.3 dB/cm at 1064 nm and 1.93 dB/cm at 1330 nm is obtained in a 1.4-cm-long waveguide with a Nd3+ concentration of 1.68×1020 cm-3 when launching 45 mW of pump power. In longer waveguides a maximum gain of 14.4 dB and 5.1 dB is obtained at these wavelengths, respectively. Net optical gain is also observed in the range 865-930 nm and a peak gain of 1.57 dB/cm in a short and 3.0 dB in a 4.1-cm-long waveguide is obtained at 880 nm with a Nd3+ concentration of 0.65×1020 cm-3. By use of a rate-equation model, the gain on these three transitions is calculated, and the macroscopic parameter of energy-transfer upconversion as a function of Nd3+ concentration is derived. The high internal net gain indicates that Al2O3:Nd3+ channel waveguide amplifiers are suitable for providing gain in many integrated optical devices.

Yang, J.; van Dalfsen, K.; Wörhoff, K.; Ay, F.; Pollnau, M.

2010-10-01

257

Entropy driven spontaneous formation of highly porous films from polymer-nanoparticle composites  

NASA Astrophysics Data System (ADS)

Nanoporous materials have become indispensable in many fields ranging from photonics, catalysis and semiconductor processing to biosensor infrastructure. Rapid and energy efficient process fabrication of these materials is, however, nontrivial. In this communication, we describe a simple method for the rapid fabrication of these materials from colloidal dispersions of Polymethyl Silsesquioxane nanoparticles. Nanoparticle-polymer composites above the decomposition temperature of the polymer are examined and the entropic gain experienced by the nanoparticles in this rubric is harnessed to fabricate novel highly porous films composed of nanoparticles. Optically smooth, hydrophobic films with low refractive indices (as low as 1.048) and high surface areas (as high as 1325 m2 g-1) have been achieved with this approach. In this communication we address the behavior of such systems that are both temperature and substrate surface energy dependent. The method is applicable, in principle, to a variety of nanoparticle-polymer systems to fabricate custom nanoporous materials.

Korampally, Venumadhav; Yun, Minseong; Rajagopalan, Thiruvengadathan; Dasgupta, Purnendu K.; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

2009-10-01

258

LASERS: High-gain Ni-like x-ray laser driven by two laser pulses  

NASA Astrophysics Data System (ADS)

An Ni-like x-ray laser scheme with a double-pulse laser driver is suggested for increasing the gain of the 3p63d94d ?3p63d94p and new 3p53d104p ?3p53d104s lasing transitions, and of a possible 'water-window' inner-shell 3d ?3p (3p53d104p ?3p63d94p) transition. The calculated gain coefficients for tantalum and tungsten are in agreement with the published experimental results for the 4d ?4p transitions. Inner-shell lasing in a material with a relatively low Z, such as caesium, is suggested on the basis of this transition scheme. It is shown that the use of nonthermal electron pumping (by the second laser pulse) leads to higher gains.

Baer, A.; Schwob, J. L.; Zigler, A.; Eliezer, S.; Henis, Z.

1996-05-01

259

Moderate volume of high relative training intensity produces greater strength gains compared with low and high volumes in competitive weightlifters.  

PubMed

The purpose of this study was to examine the effect of 3 volumes of heavy resistance, average relative training intensity (expressed as a percentage of 1 repetition maximum that represented the absolute kilograms lifted divided by the number of repetitions performed) programs on maximal strength (1RM) in Snatch (Sn), Clean & Jerk (C&J), and Squat (Sq). Twenty-nine experienced (>3 years), trained junior weightlifters were randomly assigned into 1 of 3 groups: low-intensity group (LIG; n = 12), moderate-intensity group (MIG; n = 9), and high-intensity group (HIG; n = 8). All subjects trained for 10 weeks, 4-5 days a week, in a periodized routine using the same exercises and training volume (expressed as total number of repetitions performed at intensities equal to or greater than 60% of 1RM), but different programmed total repetitions at intensities of >90-100% of 1RM for the entire 10-week period: LIG (46 repetitions), MIG (93 repetitions), and HIG (184 repetitions). During the training period, MIG and LIG showed a significant increase (p < 0.01-0.05) for C&J (10.5% and 3% for MIG and LIG, respectively) and Sq (9.5% and 5.3% for MIG and LIG, respectively), whereas in HIG the increase took place only in Sq (6.9%, p < 0.05). A calculation of effect sizes revealed greater strength gains in the MIG than in HIG or LIG. There were no significant differences between LIG and HIG training volume-induced strength gains. All the subjects in HIG were unable to fully accomplish the repetitions programmed at relative intensities greater than 90% of 1RM. The present results indicate that short-term resistance training using moderate volumes of high relative intensity tended to produce higher enhancements in weightlifting performance compared with low and high volumes of high relative training intensities of equal total volume in experienced, trained young weightlifters. Therefore, for the present population of weightlifters, it may be beneficial to use the MIG training protocol to improve the weightlifting program at least in a short-term (10 weeks) cycle of training. PMID:16503695

González-Badillo, Juan José; Izquierdo, Mikel; Gorostiaga, Esteban M

2006-02-01

260

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

261

High-impact exercise promotes bone gain in well-trained female athletes.  

PubMed

Maximizing peak bone mass, as well as reducing its loss after menopause, is important for the prevention of osteoporosis. One mode of activity, gymnastics training, invokes high impact loading strains on the skeleton which may have powerful osteogenic effects. To examine the role of athletic activity, specifically gymnastics, on bone mineral density (BMD) accretion, we monitored longitudinal changes in regional and whole body BMD in collegiate women gymnasts and competitive athletes whose skeletons are exposed to differential loading patterns: runners and swimmers. Two cohorts were studied. Cohort I = 26 gymnasts (19.7 +/- 1.2 years), 36 runners (21.1 +/- 2.7 years) and 14 nonathletic women (19.3 +/- 1.7 years) followed over an 8-month period. Cohort II = 8 gymnasts (18.9 +/- 1.1 years), 11 swimmers (20.0 +/- 2.3 years) and 11 nonathletic women (19.0 +/- 1.2 years) followed over a 12-month period. Lumbar spine (L2-4), femoral neck, and whole body BMD (g/cm2) were assessed by dual-energy X-ray absorptiometry. For cohort I, the percent change in lumbar spine BMD after 8 months was significantly greater (p = 0.0001) in the gymnasts (2.8 +/- 2.4%) than in the runners (-0.2 +/- 2.0%) or controls (0.7 +/- 1.3%). An increase in femoral neck BMD of 1.6 +/- 3.6% in gymnasts was also greater (p < 0.05) than runners (-1.2 +/- 3.0%) and approached significance compared with controls (-0.9 +/- 2.2%, p = 0.06). For cohort II, gymnasts gained 2.3 +/- 1.6% at the lumbar spine which differed significantly (p < 0.01) from changes in swimmers (-0.3 +/- 1.5%) and controls (-0.4 +/- 1.7%). Similarly, the change at the femoral neck was greater (p < 0.001) in gymnasts (5.0 +/- 3.4%) than swimmers (-0.6 +/- 2.8%) or controls (2.0 +/- 2.3%). The percent change in BMD at any site did not differ between eumenorrheic and irregularly menstruating athletes. These results indicate that bone mineral at clinically relevant sites, the lumbar spine and femoral neck, can respond dramatically to mechanical loading characteristic of gymnastics training in college-aged women. This occurred despite high initial BMD values and was independent of reproductive hormone status. The results provide evidence to support the view that high impact loading, rather than selection bias, underlies high BMD values characteristic of women gymnasts. Because all athletes underwent resistance training throughout the year of study, muscle strengthening activity did not appear to be a significant factor in the skeletal response observed in gymnasts. We conclude that activities resulting in high skeletal impacts may be particularly osteotropic for young women. PMID:9041058

Taaffe, D R; Robinson, T L; Snow, C M; Marcus, R

1997-02-01

262

Measurement and Simulation of Spontaneous Raman Scattering Spectra in High-Pressure, Fuel-Rich H2-Air Flames.  

National Technical Information Service (NTIS)

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-press...

J. Kojima Q. V. Nguyen

2003-01-01

263

Maternal Locus of Control and Developmental Gain Demonstrated by High Risk Infants: A Longitudinal Analysis.  

ERIC Educational Resources Information Center

Short- and long-term effects of a parent-infant training program for biologically handicapped infants was evaluated in terms of maternal locus of control. Results indicated that maternal locus of control accounted for a substantial portion of the variance in the infants' developmental gains following the program intervention period. (Author/RH)

Maisto, Albert A.; German, Michael L.

1981-01-01

264

High-temporal contrast using low-gain optical parametric amplification  

SciTech Connect

We demonstrate the use of low-gain optical parametric amplification (OPA) as a means of improving temporal contrast to a detection-limited level 10{sup -10}. 250 {mu}J, 500 fs pulses of 1053 nm are frequency doubled and subsequently restored to the original wavelength by OPA with >10% efficiency.

Shah, Rahul C [Los Alamos National Laboratory; Johnson, Randall P [Los Alamos National Laboratory; Shimada, Tsutomu [Los Alamos National Laboratory; Flippo, Kirk A [Los Alamos National Laboratory; Fernandez, Juan C [Los Alamos National Laboratory; Hegelich, Bjorn M [Los Alamos National Laboratory

2008-01-01

265

Liner radius fluctuations in a high-gain Cherenkov free-electron laser  

Microsoft Academic Search

Phase shifts in the propagating electromagnetic field of a Cherenkov free-electron laser (CFEL) can affect its gain. The phase velocity of an electromagnetic wave varies, for example, when the lined waveguide is inhomogeneous along its length. In this paper, we study quantitatively the saturated power of a particular CFEL at both weak and strong electron-beam pumping when the inner radius

I. de La Fuente; P. J. M. van der Slot; K.-J. Boller

2007-01-01

266

Simulation, modeling, and experimental studies of high-gain gallium arsenide photoconductive switches for ultra-wideband applications  

Microsoft Academic Search

This paper describes recent results to better understand the physics of operation of high-gain photoconductive semiconductor switches (PCSSs). Computer simulation is a viable tool in the study of the physics of device operation. Such a study of the PCSS will lead to a better understanding of the device mechanisms and may result in the diagnosis of problems and design of

E. Schamiloglu; N. E. Islam; C. B. Fleddermann; B. Shipley; R. P. Joshi; L. Zheng

1998-01-01

267

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

268

Design methodology for Sievenpiper high-impedance surfaces: an artificial magnetic conductor for positive gain electrically small antennas  

Microsoft Academic Search

The Sievenpiper high-impedance surface is a periodic structure characterized by a substrate filled with an array of vertical vias, capped by a capacitive frequency selective surface (FSS). It functions as the ideal antenna groundplane for wireless applications because it simultaneously enhances the gain of the antenna as it suppresses the surface waves associated with it (thus reducing the undesired back-lobe

Sergio Clavijo; Rodolfo E. Díaz; William E. McKinzie

2003-01-01

269

An SOI CMOS, high gain and low noise transimpedance-limiting amplifier for 10Gb\\/s applications  

Microsoft Academic Search

This paper presents a low noise, high gain transimpedance-limiting amplifier (TIALA) design for 10Gb\\/s applications, implemented in a 0.13mum SOI CMOS technology. Powered from a single 1.5V supply and consuming 165mW, the TIALA features auto-zero DC feedback and has 25muApp input current sensitivity (an estimated -16dBm optical sensitivity) with over 40dB electrical dynamic range and 14 kOhm linear gain

Florin Pera; Sorin P. Voinigescu

2006-01-01

270

A V-band, high gain, low noise, monolithic PHEMT amplifier mounted on a small hermetically sealed metal package  

Microsoft Academic Search

V-band, high gain, low noise, monolithic amplifiers based on 0.15-?m AlGaAs-InGaAs-GaAs pseudomorphic HEMT's have been developed. The four-stage amplifier has been assembled on a small hermetically sealed metal package and has achieved a noise figure of 3 dB with a small signal gain of 42.2 dB at 51 GHz. The overall amplifier measured 14.2×20.0×2.3 mm3. The two-stage amplifier has been

Yasushi Itoh; Yoshie Horiie; Kazuhiko Nakahara; Naohito Yoshida; Takayuki Katoh; Tadashi Takagi

1995-01-01

271

Spontaneous high-gamma band activity reflects functional organization of auditory cortex in the awake macaque  

PubMed Central

Summary In the absence of sensory stimuli, spontaneous activity in the brain has been shown to exhibit organization at multiple spatiotemporal scales. In the macaque auditory cortex, responses to acoustic stimuli are tonotopically organized within multiple, adjacent frequency maps aligned in a caudorostral direction on the supratemporal plane (STP) of the lateral sulcus. Here we used chronic micro-electrocorticography to investigate the correspondence between sensory maps and spontaneous neural fluctuations in the auditory cortex. We first mapped tonotopic organization across 96 electrodes spanning approximately two centimeters along the primary and higher auditory cortex. In separate sessions we then observed that spontaneous activity at the same sites exhibited spatial covariation that reflected the tonotopic map of the STP. This observation demonstrates a close relationship between functional organization and spontaneous neural activity in the sensory cortex of the awake monkey.

Fukushima, Makoto; Saunders, Richard C.; Leopold, David A.; Mishkin, Mortimer; Averbeck, Bruno B.

2012-01-01

272

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

273

Novel Design of a High-gain and Wideband Fabry-Pérot Cavity Antenna Using a Tapered AMC Substrate  

NASA Astrophysics Data System (ADS)

A high-gain and wideband electromagnetic bandgap (EBG) resonator antenna with a tapered artificial magnetic conductor (AMC) ground plane is presented. The proposed EBG resonator antenna is comprised of a frequency selective surface (FSS) superstrate with a strip dipole array and an AMC ground plane with tapered rectangular patches. The realized gain and the bandwidth of the antenna can be improved simultaneously by using the tapered AMC where the phase difference of the reflected waves from the patches with different length is within 180° and the destructive interference among them can be considerably reduced. The maximum gain is increased about 2˜3 dB and the bandwidth is improved about 2.5 times compared to when the uniform AMC is used.

Yeo, Junho; Kim, Dongho

2009-03-01

274

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

275

Stability Evaluation of Direct-Drive Ignition and High-Gain Targets, Based on Hydrodynamic Instability Experiments  

NASA Astrophysics Data System (ADS)

Hydrodynamic stability of the NIF direct-drive target [1] and direct-drive high-gain target [2] has been tested, using the hydro-code ILESTA-1D + mix model. The mix model consists of the rigorously tested imprint model [3], Rayleigh-Taylor (RT) growth [4] followed by the saturation [5]. The stability test indicates that the NIF target is stable if the laser irradiation nonuniformity is similar to or better than that of the partially coherent light [6]. On the other hand, the high-gain target (gain = 140) has been found to be unstable. However, the test also suggests that the high-gain target can be stabilized by imprint suppression by x-ray pre-irradiation and the RT growth rates reduced by non-local heat transport. More stringent test of our understanding of the RT growth rate is necessary to judge whether this stabilization is feasible. [1] C. Verdon, BAPS 38 ('93); S. Weber, Phys. Plasmas 4, 1978 ('97). [2] H. Takabe, JJAP ('93). [3] H. Azechi, Phys. Plasmas 4, 4079 ('97). [4] H. Takabe, Phys. Plasmas 28, 3676 ('85). [5] S. Haan, Phys. Rev. A 39, 5812 ('89). [6] N. Miyanaga, IAEA 1994.

Azechi, Hiroshi; Nagaya, T.; Takabe, H.; Nakai, M.; Miyanaga, N.; Shiraga, H.; Nishimura, H.

1998-11-01

276

Ultrafast laser inscription of a high-gain Er-doped bismuthate glass waveguide amplifier.  

PubMed

An Er-doped bismuthate glass waveguide amplifier has been fabricated using ultrafast laser inscription. Under zero pump conditions, the 87.0 mm long waveguide exhibited a fiber-to-fiber insertion loss of 4.0 dB at 1618 nm, outside the Er(3+) ion absorption band. We attribute approximately 1.8 dB of the insertion loss to coupling losses, 0.2 dB to Fresnel reflections and approximately 2.0 dB to propagation losses. When pumped using 1050 mW of 980 nm light, the amplifier exhibited a peak internal gain per unit length of 2.3 dB.cm(-1) at 1533 nm and a peak fiber-to-fiber net gain of 16.0 dB at 1533 nm. In this paper we also report the results of output power saturation and noise figure measurements. PMID:20588450

Thomson, Robert R; Psaila, Nicholas D; Beecher, Stephen J; Kar, Ajoy K

2010-06-01

277

A high Nugent score but not a positive culture for genital mycoplasmas is a risk factor for spontaneous preterm birth  

PubMed Central

Objective This study was performed to evaluate the relationship among the Nugent score for the diagnosis of bacterial vaginosis (BV), the results of vaginal fluid culture for genital mycoplasma, and the subsequent occurrence of preterm birth. Methods The Nugent score and culture for genital mycoplasmas were performed in vaginal fluid obtained from 977 pregnant women (gestational age 13–30 weeks). Vaginal samples were obtained with sterile cotton swabs. The relationship among the Nugent score, vaginal fluid culture results and the occurrence of spontaneous preterm birth was examined. Results (1) Of the 977 women, 14% (137) had a Nugent score of ? 8; (2) The prevalence of a positive vaginal culture for genital mycoplasmas was 30% (288); Ureaplasma urealyticum was isolated in 252 (88%), Mycoplasma hominis in 9 (3%), and both in 27 (9%) women; (3) Cases with a Nugent score of ? 8 had a higher rate of a positive vaginal culture for genital mycoplasmas than those with the lower Nugent score (55% vs. 25%; p<0.001); (4) Women with a Nugent score of ? 8 had a significantly higher rate of spontaneous preterm birth <37 (10% vs. 4%), <34 (5% vs. 2%), and <32 (4% vs. 1%) weeks of gestation than those with the lower Nugent score (At each gestational age, p<0.05); (5) In contrast, a positive vaginal culture for genital mycoplasmas was not associated with an increased risk for spontaneous preterm birth; (6) Among patients with a positive culture and a Nugent score of ? 8, the frequency of spontaneous preterm delivery (<37 weeks) was 10% (7/72); (7) There was no difference in the incidence of spontaneous preterm delivery according to the results of vaginal culture in patients with a Nugent score of ? 8, as well as in those with a lower Nugent score. Conclusion A high Nugent score (? 8) for the detection of BV but not a positive vaginal culture for genital mycoplasmas is a risk factor for spontaneous preterm birth.

Lee, SE; Romero, R; Kim, EC; Yoon, GH

2013-01-01

278

Effect of two high-oleic oils on the liver lipid composition of spontaneously hypertensive rats.  

PubMed

Despite having similar fatty acid composition and plasma lipid composition after ingestion, olive oil, but not high-oleic sunflower oil (HOSO), is capable of reducing blood pressure. HOSO contains mainly triolein, whereas olive oil contains important amounts of dioleoyl-palmitoyl-glycerol. In order to see if its different triacylglycerol (TAG) composition could be related to the hypotensive effect of olive oil, Spontaneously Hypertensive Rats (SHR) were fed with HOSO and olive oil-rich diets. Liver lipid composition was determined. Total lipid, fatty acid and TAG composition was analyzed. Rats fed olive oil (67.24 +/- 4.23) were observed to retain more dioleoyl-acyl-glycerol species in their liver than those fed HOSO (56.6 +/- 3.95), specially triolein (20.69 +/- 1.77 olive oil, vs. 12.54 +/- 1.97 HOSO), in spite of its lower content of this TAG. On the contrary, rats consuming HOSO had higher amounts of dilinoleoyl-acyl-glycerol species (9.26 +/- 1.57 HOSO, vs.4.02 +/- 0.90 olive oil). In conclusion, olive oil provided a more beneficial TAG profile in the liver of SHR rats than HOSO, probably due to the differences in the TAG composition of both oils. PMID:10794069

Perona, J S; Ruiz-Gutiérrez, V

2000-01-01

279

Spontaneous layering of porous silicon layers formed at high current densities  

NASA Astrophysics Data System (ADS)

We report here a curious effect of spontaneous fracturing of the silicon layers formed in galvanostatic conditions at medium and high current densities. Instead of formation of homogeneous p-Si layer as at low currents, a stack of thin layers is formed. Each layer is nearly separated from others and possesses rather flat interfaces. The effects is observed using p+-Si wafers for the p-Si formation and starts being noticeable at above 100 mA/cm2.We interpret these results in terms of the porous silicon growth model where generation of dynamic mechanical stress during the p-Si growth causes sharp changes in Si dissolution mechanism from anisotropic etching of individual needle-like pores in silicon to their branching and isotropic etching. At this moment p-Si layer loses its adhesion to the surface of Si wafer and another p-Si layer starts growing. One of the mechanisms triggering on the separation of p-Si layers from one another is a fluctuation of local anodic current in the pore bottoms associated with gas bubble evolution during the p-Si formation.

Parkhutik, Vitali; Curiel-Esparza, Jorge; Millan, Mari-Carmen; Albella, Jose

2005-06-01

280

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

281

Theoretical and experimental results of a fully ballistic nano-FET with high gain  

Microsoft Academic Search

We report on the experimental evidence of a fully ballistic nano-FET with a voltage gain higher than 1 which is based on a 1D quantum ballistic conductor. In such a FET, the transconductance and the output conductance are basically modulated by the 1D subbands and the experimental results can theoretically be explained based on the Landauer-Buttiker formalism and the Buttiker

E. Gremion; D. Niepce; U. Gennser; A. Cavanna; Y. Jin

2008-01-01

282

Pulse slippage in high-gain, optically guided free-electron lasers  

Microsoft Academic Search

Using the solution of the fully three-dimensional dispersion relation for the fastest-growing mode an expression for slippage in an optically guided free-electron laser (FEL) amplifier is derived. The FEL operates in the exponential regime and the optical beam is guided by the electron beam. The slippage distance is less than that in the low-gain regime. The reduced slippage arises from

B. Hafizi; P. Sprangle; J. R. Peñano

2007-01-01

283

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

Microsoft Academic Search

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

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

2005-01-01

284

Endothelial Dysfunction and the Development of Renal Injury in Spontaneously Hypertensive Rats Fed a High-Fat Diet  

Microsoft Academic Search

Obesity and hypertension have been identified as cardiovascular risk factors that contribute to the progression of end-stage renal disease. To examine the mechanisms by which a high-fat diet and hypertension contribute to endothelial dysfunction and renal injury, 8-week-old male spontaneously hypertensive rats and Wistar rats were fed a high-fat (36% fat) or a normal-fat (7% fat) diet for 10 weeks.

Sarah F. Knight; Jeffrey E. Quigley; Jianghe Yuan; Siddhartha S. Roy; Ahmed Elmarakby; John D. Imig

2010-01-01

285

Compact 120 TW Ti:sapphire laser system with a high gain final amplifier  

Microsoft Academic Search

A 120TW\\/36fs laser system based on Ti:sapphire chirped-pulse amplification (CPA) has been successfully established in our lab. The final four pass Ti:sapphire amplifier pumped by an energetic single-shot Nd:YAG—Nd:glass laser was designed and optimized. With 24J\\/8ns pump energy at 532nm, 300mJ\\/220ps chirped pulse was amplified to 5.98J in this amplifier, and a total saturated gain of ?20 was achieved. The

Xiaoyan Liang; Yuxin Leng; Lihuang Lin; Haihe Lu; Wenyao Wang; Yunhua Jiang; Bin Shuai; Hanlin Peng; Baozhen Zhao; Cheng Wang; Wenqi Zhang; Zhengquan Zhang; Ruxin Li; Zhizhan Xu

2006-01-01

286

A high gain, time-resolving spectrograph for the diagnosis of laboratory simulated reentry.  

PubMed

To increase the sensitivity of a time-resolving spectrograph, a four-stage, magnetically focused, cascade type image intensifier was coupled to an electron scanning image converter. A radiant intensity gain of more than 500, enough to permit the study of far wake radiation, has been achieved, along with sufficient spectral resolution for the determination of temperature and electron density profiles in the flow behind a hypervelocity object. An example of wake temperature results from the time-resolved vibrational bands of CN is presented. PMID:20072390

Liu, I D; Baskett, J R

1969-06-01

287

[Spontaneous intracardiac contrast and embolic risk].  

PubMed

Spontaneous contrast in the form of smokey echos in the cardiac chambers is considered to be a risk factor for thromboembolism. The aggregation of red blood cells results in larger target which diffuse a measurable in vitro ultrasonic signal. The phenomenon of erythrocytic aggregation is dependent on the red cells themselves, the plasma fibrinogen and conditions of blood flow. The other constituents of the blood only reflect a small amount of ultrasound, usually undetectable. Transoesophageal echocardiography with high frequency transducers (5 MHz) positioned in close proximity to the cardiac chambers, has become the reference method for detecting spontaneous contrast. This phenomenon is almost exclusively observed in the left atrium and left auricle and rarely in the other cardiac chambers or descending aorta. In pathological situations, spontaneous contrast is essentially implicated in two conditions: mitral valve obstacles and non-valvular atrial fibrillation. Conversely, moderate to severe mitral regurgitation is a negative predictive factor of spontaneous contrast. However, a purely qualitative appreciation of spontaneous contrast which may be influenced by the gain setting and technical specifications of the echocardiograph, and the subjectivity of the operator, is an important limitation. Therefore, the identification of quantitative markers of spontaneous contrats and new therapeutic antithrombotic protocols remain essential. PMID:8763005

Lardoux, H; Boynard, M; Cormier, B; Pezzano, M

1996-04-01

288

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

289

Erbium concentration control and optimization in erbium yttrium chloride silicate single crystal nanowires as a high gain material  

NASA Astrophysics Data System (ADS)

Increasing erbium concentration while minimizing the reduction of photoluminescence is an important task for achieving erbium-based high-gain materials for integrated photonics applications. Here, we demonstrate a strategy of controlled variation of Erbium density in the growth of erbium yttrium chloride silicate (EYCS) ((ErxY1-x)3(SiO4)2Cl)) single crystal nanowires by systematically varying x between 0 and 1. We show that, as a trade-off between high Er density and suppressed upconversion, Er composition x = 0.3 provides the best compromise with the strongest photoluminescence. This optimized Er-composition corresponds to an Er density of 5×1021 cm-3, five times larger than the optimized Er density demonstrated previously for other thin film materials. We estimate that this optimized EYCS is promising in achieving optical gain exceeding 100 dB/cm.

Yin, Leijun; Shelhammer, David; Zhao, Gejian; Liu, Zhicheng; Ning, C. Z.

2013-09-01

290

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

291

Development of a hologram-based CATR for testing a very high gain antenna at 650 GHz  

Microsoft Academic Search

A compact antenna test range (CATR) based on a radio frequency hologram is a potential method for testing high-gain antennas at submillimetre wavelengths. Within a European Space Agency (ESA) project, a 1.5 m reflector antenna, ADMIRALS Representative Test Object (RTO), will be tested at 650 GHz during autumn 2006. For these antenna tests, MilliLab \\/ Radio Laboratory at the Helsinki

Juha Ala-Laurinaho; Tomi Koskinen; Janne Hakli; Aki Karttunen; Anne Lonnqvist; Eero Noponen; Juha Mallat; Matti Vaaja; Ville Viikari; Antti Raisanen; Jukka Heinonen; Pekka Hautala; Jerzy Lemanczyk

2006-01-01

292

MODERATE RESISTANCE TRAINING VOLUME PRODUCES MORE FAVORABLE STRENGTH GAINS THAN HIGH OR LOW VOLUMES DURING A SHORT TERM TRAINING CYCLE  

Microsoft Academic Search

Gonzalez-Badillo, J.J., E.M. Gorostiaga, R. Arellano, and M. Izquierdo. Moderate resistance training volume produces more favorable strength gains than high or low volumes during a short-term training cycle. J. Strength Cond. Res. 19(3):689- 697. 2005.—The purpose of this study was to examine the effects of 3 resistance training volumes on maximal strength in the snatch (Sn), clean & jerk (C&J),

JUAN J. GONZALEZ-BADILLO; ESTEBAN M. GOROSTIAGA; RAUL ARELLANO; MIKEL IZQUIERDO

293

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

294

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

295

High temperature and wavelength dependence of avalanche gain of AlAsSb avalanche photodiodes.  

PubMed

The evolution of the dark currents and breakdown at elevated temperatures of up to 450 ?K are studied using thin AlAsSb avalanche regions. While the dark currents increase rapidly as the temperature is increased, the avalanche gain is shown to only have a weak temperature dependence. Temperature coefficients of breakdown voltage of 0.93 and 1.93 ?mV/K were obtained from the diodes of 80 and 230 ?nm avalanche regions (i-regions), respectively. These values are significantly lower than for other available avalanche materials at these temperatures. The wavelength dependence of multiplication characteristics of AlAsSb p-i-n diodes has also been investigated, and it was found that the ionization coefficients for electrons and holes are comparable within the electric field and wavelength ranges measured. PMID:22048393

Sandall, Ian C; Xie, Shiyu; Xie, Jingjing; Tan, Chee Hing

2011-11-01

296

High gain selective amplification in whispering gallery mode resonators: analysis by cavity ring down method  

NASA Astrophysics Data System (ADS)

We study both theoretically and experimentally the dispersive properties of single whispering gallery mode resonators. We present a simple experimental protocol which allows us to obtain in detail its coupling regime and thus their dispersive properties. We demonstrate a compact optical amplifier with a gain up to 20dB in an Erbium doped fluoride microsphere of 135?m in diameter coupled via a tapered fiber. The model is also applied to analyze the dynamic behavior of the modal coupling between two degenerate resonances of the same cavity. In particular, this can be used to describe the coupling of counterpropagating whispering gallery modes (WGM) by Rayleigh scattering. The theory is successfully compared to experiments carried out in silica microspheres

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

2013-03-01

297

Impulse gain and damage from very high dynamic loading using flyer impact  

SciTech Connect

The Lawrence Livermore National Laboratory (LLNL) 1 MJ and 87 kJ electric guns are in use for a variety of shock-wave applications using the hypervelocity impact of dielectric (or dielectric and metal composite) flyer plates on material samples. The 1 MJ electric gun is a newly completed facility and will be described. The specific applications discussed here include a study of momentum gain and spat damage produced by Kapton flyer impact on aluminium 6061-T6. The experimental impact measurements are used to calibrate code calculations that can be applied under more general hypervelocity impact conditions to typical relative orbital velocities near 10 km/s. The analytical results of code calculations supporting these study areas are also reported.

Osher, J.; Chau, H.; Gerassimenko, M.; Lee, R.; Pomykal, G.; Terhune, R.; Weingart, R.

1991-07-01

298

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

Microsoft Academic Search

Rotational and vibrational spontaneous Raman scattering (SRS) spectra of H2, N2 and H2O have been measured in H2-air flames at pressures up to 30.4 bar as a first step towards establishing a comprehensive Raman spectral database for temperatures and species in high-pressure combustion. We have obtained an initial set of measurements that indicate the spectra are of sufficient quality in

Jun Kojima; Quang-Viet Nguyen

2004-01-01

299

High-fat diet augments cardiac hypertrophy and delays blood pressure recovery from stress in spontaneously hypertensive rat  

Microsoft Academic Search

In this study, we investigated the effects of long-term high-fat diet (HFD) administration on heart morphology and cardiovascular system performance under basal and stressful conditions. Sixteen-week old (adult) male spontaneously hypertensive rats were randomly separated into standard diet (SD, n=6) and HFD (n=7) fed groups. After 12 weeks of SD or HFD feeding, mean arterial blood pressure (MAP), heart rate

Lucie Sedova; Bérubé Julie; Denis DeBlois; Johanne Tremblay; Pavel Hamet; Zdenka Pausova

2003-01-01

300

Nanoscale plasmonic resonators with high Purcell factor: spontaneous and stimulated emission  

Microsoft Academic Search

Plasmonic nanoparticles with silver cores and silica shells containing Eu fluorophores near the surface have been produced by wet chemistry method and their spontaneous emission properties characterized. Fluorescence amplification and decreased lifetime is interpreted within the Purcell framework which highlights the role of surface plasmon polariton modes of the nanoparticle. These behave as energy-storing resonators, with values of the Q

Ewa M. Goldys; Wei Deng; Nils P. Calander; K. Drozdowicz-Tomsia; Dayong Jin

2011-01-01

301

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

Microsoft Academic Search

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.

Robert Kolos; Jerzy Sepiol

1989-01-01

302

WEIGHT GAIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

During the last 40 years there have been dramatic changes in the recommendations for optimal maternal weight gain during pregnancy. In the past it was thought that it was necessary to restrict the diet of many pregnant women in order to reduce the perceived risks associated with higher weight gains....

303

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

304

Sigma-delta modulator for a programmable gain, low-power, high-linearity automotive sensor interface  

NASA Astrophysics Data System (ADS)

Smart sensors play a critical role in modern automotive electronic systems, covering a wide range of data capturing functions and operating under adverse environmental conditions - temperature range of [-40ºC,175ºC]. In such sensors, the signal provided by transducers is composed of an offset voltage, which depends on the manufacturing process, and a low-frequency signal carrying the information. In practice, the offset voltage is subject to temperature variations, thus causing a shifting of the signal range to be measured. Therefore, the measuring circuit driving the sensor, normally formed by a low-noise preamplifier and an Analog-to-Digital Converter (ADC), must accommodate the complete range of possible offsets and real signals. In this scenario, the use of ADCs based on Sigma-Delta Modulators (SDMs) is convenient for several reasons. On the one hand, the noise-shaping performed by SDMs allows to achieve high resolution (16-17bits), in the band of interest (10-20kHz), with less power consumption than full Nyquist ADCs. On the other hand, the action of feedback renders SDMs very linear, and high-linearity is a must for automotive applications. Last but not least, the robustness of SDMs with respect to circuit imperfections make them suitable to include programmable gain without significant performance degradation. This feature allows to accommodate the complete range of possible offsets and information signals in a sensor interface with relaxed specifications for the preamplifier circuitry. This paper describes the design and implementation of a third-order cascade (2-1) SDM with programmable gain in a 0.35mm CMOS technology - the type of technology commonly employed for automotive applications (deep submicron is mostly employed for telecom). It is capable of handling signals up to 20-kHz bandwidth with 17-bit resolution. The programmable gain is implemented by a capacitor array whose unitary capacitors are connected or disconnected depending on the value of the selected gain. In order to relax the amplifier dynamics requirements as the modulator gain varies, switchable capacitor arrays have been used for all the capacitors in the first integrator. The design of the modulator building blocks is based upon a top-down CAD methodology which combines simulation and statistical optimization at different levels of the modulator hierarchy. As a result, a dynamic range equal to 105 dB is obtained for all cases of the modulator gain, which corresponds to 17 bit resolution.

de la Rosa, José M.; Medeiro, Fernando; Pérez-Verdú, Belén; del Río, Rocío; Rodríguez-Vázquez, Angel

2003-04-01

305

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

306

Regrowth-free high-gain InGaAsP/InP active-passive platform via ion implantation.  

PubMed

We demonstrate a regrowth-free material platform to create monolithic InGaAsP/InP photonic integrated circuits (PICs) with high-gain active and low-loss passive sections via a PL detuning of >135 nm. We show 2.5 µm wide by 400 µm long semiconductor optical amplifiers with >40 dB/mm gain at 1570 nm, and passive waveguide losses <2.3 dB/mm. The bandgap in the passive section is detuned using low-energy 190 keV channelized phosphorous implantation and subsequent rapid thermal annealing to achieve impurity-induced quantum well intermixing (QWI). The PL wavelengths in the active and passive sections are 1553 and 1417 nm, respectively. Lasing wavelengths for 500 µm Fabry-Perot lasers are 1567 and 1453 nm, respectively. PMID:23037047

Parker, John S; Sivananthan, Abirami; Norberg, Erik; Coldren, Larry A

2012-08-27

307

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

308

Steerable reflective high-gain antenna array based on loaded dipole scatterers  

NASA Astrophysics Data System (ADS)

We present the results of studying experimentally a constructively simple and inexpensive centimeter-wave antenna having a radiation pattern, whose shape can be controlled. Specifically, the main lobe of the pattern can be scanned in a wide angular range, its width can be changed, and minima of the pattern can be formed in specified directions. The feed being the only active element of the antenna is located in front of the mirror made up by a system of steerable passive scatterers, which are dipole antennas loaded by semiconducting diodes. The capacity of the diode loads is changed under the action of controlling signals, which set specific bias voltages at each diode. The studies aimed at testing experimentally the operability of the antenna and assessing the practically achievable parameters of the proposed antenna design. The developed laboratory model of the antenna operates at frequencies near 2.4 GHz with a gain of more than 21 dBi and the possibility of scanning the main lobe of the radiation pattern in the horizontal and vertical planes to ±60° and ±15°, respectively, for the antenna with overall dimensions 100 × 60 × 30 cm.

Mainwaring, A.; Umnov, A. L.; Shuralev, M. O.; Eltsov, A. Yu.

2011-02-01

309

Characterization of system calibration parameters for high gain dual polarization satellite beacon diagnostics of ionospheric variations  

NASA Astrophysics Data System (ADS)

We present complementary methods for calibrating the dual-polarization feed of a ground-based tracking antenna used for ionospheric measurements. Several calibration parameters are defined which describe the state of the measurement equipment. These key parameters then form a transformational Mueller matrix which may be used to remove system bias in data received from known beacons. Several strategies are developed to quantify these time-dependent distortions for the Green Bank 140' diameter antenna and receiver, although these methods could be applied to other similar systems. One approach quantifies the receiver biases in terms of amplitude and gain differentials. This is accomplished by measuring polarimetric differences between channels using a test signal with a known amplitude and phase. Due to variations over time periods on the scale of a beacon track, this procedure is most effective when the calibration signal is injected concurrently with the beacon measurements. To determine antenna feed distortion, including cross-polarization and ellipticity, data is recorded from an external celestial source. An example shows the effectiveness of this calibration technique by comparing calibrated data to data without correction. Error estimates of the calibration parameters in the example establish an upper bound of 0.22 TEC units for measurements at 150 MHz along track.

Anderson, James P.; Phelps, Eric B.; Erickson, Philip J.; Lind, Frank D.; Coster, Anthea J.; Langston, Glen I.

2011-10-01

310

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

311

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

NASA Astrophysics Data System (ADS)

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

Yu, Jin-Jin; Deng, Ruo-Han; Yuan, Hong-Hui; Chen, Yong-Ping

2011-06-01

312

Metastatic Variants are Generated Spontaneously at a High Rate in Mouse KHT Tumor  

Microsoft Academic Search

Using the Luria--Delbruck fluctuation analysis, we have examined the lung tumor-forming ability of a series of parallel clones derived from the KHT tumor, grown to small defined sizes. From these studies, we conclude that metastatic variants arise spontaneously in the clonal lines during their growth, at an apparent rate of ≈ 10-5 per cell per generation. This rapid rate has

John F. Harris; Ann F. Chambers; Richard P. Hill; Victor Ling

1982-01-01

313

High-Energy Gamma Rays from Spontaneous Fission of 238U  

Microsoft Academic Search

A large shielded liquid-scintillation detector operating 3240 m below the surface of the earth was used to detect gamma rays from the spontaneous fission of a 238U source. In an energy range from 8 to 20 MeV, the derived spectrum is: N(E)=(6.99+\\/-0.60)×10-1e- E1.41+\\/-0.12 photons fission-1 MeV-1.

H. W. Sobel; A. A. Hruschka; W. R. Kropp; J. Lathrop; F. Reines; M. F. Crouch; B. S. Meyer; J. P. Sellschop

1973-01-01

314

Clinical significance of the presence of amniotic fluid 'sludge' in asymptomatic high-risk patients for spontaneous preterm delivery  

PubMed Central

Objective To determine the clinical significance of the presence of amniotic fluid (AF) ‘sludge’ among asymptomatic patients at high-risk for spontaneous preterm delivery. Study design This retrospective case-control study included 281 patients with (n=66) and without (n=215) AF ‘sludge’, who underwent transvaginal ultrasound between 13 and 29 completed weeks of gestation. Patients with threatened preterm labor, multiple gestation, fetal anomalies, placenta previa, and uterine contractions were excluded. Results The prevalence of AF ‘sludge’ in the study population was 23.5% (66/281). The rates of spontaneous preterm delivery at <28, <32, <35, and <37 weeks of gestation were 14.7% (29/197), 21.3% (46/216), 28.7% (62/216), and 42.1% (91/216), respectively. Patients with ‘sludge’ had: (1) a higher rate of spontaneous preterm delivery at <28 weeks [46.5% (20/43) vs. 5.8% (9/154), p<0.001], <32 weeks [55.6% (25/45) vs. 12.3% (21/171), p<0.001], and <35 weeks [62.2% (28/45) vs. 19.9% (34/171), p<0.001]; (2) a higher frequency of clinical chorioamnionitis [15.2% (10/66) vs. 5.1% (11/215), p=0.007], histologic chorioamnionitis [61.5% (40/65) vs. 28% (54/193), p<0.001] and funisitis [32.3% (21/65) vs. 19.2% (37/193), p=0.03]; (3) a higher frequency of preterm PROM [(39.4% (26/66) vs. 13.5% (29/215), p<0.001], lower gestational age at preterm PROM [24.7 weeks (22.3-28.1) vs. 32.3 weeks (27.7-34.8); p<0.001]; and (4) shorter ultrasound-to-delivery [‘sludge’ positive: 127 days (95% CI: 120-134) vs. ‘sludge’ negative: 161 days (95% CI: 153-169), p<0.001] and ultrasound-to-preterm PROM intervals [‘sludge’ positive: 23 days (95% CI: 7-39) vs. ‘sludge’ negative: 57 days (95% CI: 38-77), p=0.003] than those without ‘sludge’. AF ‘sludge’ was an independent explanatory variable for the occurrence of spontaneous preterm delivery at <28, <32, and <35 weeks, preterm PROM, MIAC, and histologic chorioamnionitis. Moreover, the combination of a cervical length <25 mm and ‘sludge’ confers an odds ratio of 14.8 and 9.9 for spontaneous preterm delivery at <28 and <32 weeks, respectively. Conclusions AF ‘sludge’ is an independent risk factor for spontaneous preterm delivery, preterm PROM, MIAC, and histologic chorioamnionitis in asymptomatic patients at high risk for spontaneous preterm delivery. Furthermore, the combination of ‘sludge’ and a short cervix confers a higher risk for spontaneous preterm delivery at <28 and <32 weeks than that of a short cervix alone.

Kusanovic, Juan Pedro; Espinoza, Jimmy; Romero, Roberto; Goncalves, Luis F.; Nien, Jyh Kae; Soto, Eleazar; Khalek, Nahla; Camacho, Natalia; Hendler, Israel; Mittal, Pooja; Friel, Lara A.; Gotsch, Francesca; Erez, Offer; Than, Nandor G.; Mazaki-Tovi, Shali; Schoen, Mary L.; Hassan, Sonia

2008-01-01

315

Growth of high-density 1.06-?m InGaAs/GaAs quantum dots for high gain lasers by molecular beamepitaxy  

NASA Astrophysics Data System (ADS)

We have progressed the growth procedure for high-density highly-uniform In(Ga)As/GaAs quantum dots (QDs) by using molecular beam epitaxy and have demonstrated high-gain 1.06-?m QD lasers for consumer electronics. The structural and optical properties of QD crystals have been improved by optimizing the growth temperature, employing InGaAs QDs in place of InAs QDs, and utilizing a height-limiting growth method, which is called the Indium-flush procedure. Lasers containing ten-layer height-limited InGaAs QDs provided a net modal gain as high as 60cm?1, which is one of the largest values for InAs/GaAs QD lasers. These results will promise the development of optoelectronic devices with high-density multiply-stacked QDs in the 1-?mband.

Watanabe, Katsuyuki; Akiyama, Tomoyuki; Yokoyama, Yoshitaka; Takemasa, Keizo; Nishi, Kenichi; Tanaka, Yu; Sugawara, Mitsuru; Arakawa, Yasuhiko

2013-09-01

316

Simulation of DARMSTADT Free Electron Laser and a Comparison of High Gain Free Electron Lasers.  

National Technical Information Service (NTIS)

The Free Electron Laser, with its wavelength tunability unlike any other laser, may be used in numerous future applications. These applications range from high energy laser weapons to surgical lasers for medical use. This thesis covers three separate topi...

D. S. Massey

2000-01-01

317

Low noise and high gain-bandwidth product AlInAs avalanche photodiodes  

Microsoft Academic Search

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

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

2008-01-01

318

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

319

Transverse and temporal characteristics of a high-gain free-electron laser in the saturation regime  

NASA Astrophysics Data System (ADS)

The transverse and the temporal characteristics of a high-gain free-electron laser are governed by refractive guiding and sideband instability, respectively. Using the self-consistent Vlasov-Maxwell equations, we explicitly determine the effective index of refraction and the guided radiation mode for an electron beam with arbitrary transverse size. Electrons trapped by the guided radiation execute synchrotron oscillation and hence are susceptible to the sideband instability. We explain the spectral evolution and determine the sideband growth rate. These theoretical predictions agree well with GINGER simulation results.

Huang, Zhirong; Kim, Kwang-Je

2002-05-01

320

(-)-Epigallocatechin-3-gallate inhibits pancreatic lipase and reduces body weight gain in high fat-fed obese mice.  

PubMed

Tea (Camellia sinensis, Theaceae) has been shown to have obesity preventive effects in laboratory studies. We hypothesized that dietary epigallocatechin-3-gallate (EGCG) could reverse metabolic syndrome in high fat-fed obese C57bl/6J mice, and that these effects were related to inhibition of pancreatic lipase (PL). Following treatment with 0.32% EGCG for 6 weeks, a 44% decrease in body weight (BW) gain in high fat-fed, obese mice (P < 0.01) was observed compared to controls. EGCG treatment increased fecal lipid content by 29.4% (P < 0.05) compared to high fat-fed control, whereas in vitro, EGCG dose-dependently inhibited PL (IC(50) = 7.5 µmol/l) in a noncompetitive manner with respect to substrate concentration. (-)-Epicatechin-3-gallate exhibited similar inhibitory activity, whereas the nonester-containing (-)-epigallocatechin did not. In conclusion, EGCG supplementation reduced final BW and BW gain in obese mice, and some of these effects may be due to inhibition of PL by EGCG. PMID:21633405

Grove, Kimberly A; Sae-tan, Sudathip; Kennett, Mary J; Lambert, Joshua D

2011-06-02

321

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

322

?-Lipoic acid reduced weight gain and improved the lipid profile in rats fed with high fat diet  

PubMed Central

The purpose of this study was to investigate the effects of ?-lipoic acid on body weight and lipid profiles in Sprague-Dawley rats fed a high fat diet (HFD). After 4 weeks of feeding, rats on the HFD were divided into three groups by randomized block design; the first group received the high-fat-diet (n = 10), and the second group received the HFD administered with 0.25% ?-lipoic acid (0.25LA), and the third group received the high-fat diet with 0.5% ?-lipoic acid (0.5LA). The high fat diet with ?-lipoic acid supplemented groups had significantly inhibited body weight gain, compared to that in the HFD group (P < 0.05). Organ weights of rats were also significantly reduced in liver, kidney, spleen, and visible fat tissues in rats supplemented with ?-lipoic acid (P < 0.05). Significant differences in plasma lipid profiles, such as total lipids, total cholesterol, triglycerides, low-density lipoprotein, and high-density lipoprotein, were observed between the HFD and 0.5LA groups. The atherogenic index and the plasma high density lipoprotein-cholesterol/total cholesterol ratio improved significantly with ?-lipoic acid supplementation in a dose-dependent manner (P < 0.05). Total hepatic cholesterol and total lipid concentration decreased significantly in high fat fed rats supplemented with ?-lipoic acid in a dose-dependent manner (P < 0.05), whereas liver triglyceride content was not affected. In conclusion, ?-lipoic acid supplementation had a positive effect on weight gain and plasma and liver lipid profiles in rats.

Seo, Eun Young; Ha, Ae Wha

2012-01-01

323

A Critical Examination of the Evidence Relating High Fructose Corn Syrup and Weight Gain  

Microsoft Academic Search

The use of high fructose corn syrup (HFCS) has increased over the past several decades in the United States while overweight and obesity rates have risen dramatically. Some scientists hypothesize that HFCS consumption has uniquely contributed to the increasing mean body mass index (BMI) of the U.S. population. The Center for Food, Nutrition, and Agriculture Policy convened an expert panel

Richard A. Forshee; Maureen L. Storey; David B. Allison; Walter H. Glinsmann; Gayle L. Hein; David R. Lineback; Sanford A. Miller; Theresa A. Nicklas; Gary A. Weaver; John S. White

2007-01-01

324

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

325

High resolution tri-linear colour TDI CCD image sensor with programmable responsivity gain  

Microsoft Academic Search

We developed a 6032 element, 32 stage Tri-linear Time Delay and Integration Focal Plane Array for high resolution colour imaging applications. The sensor offers an improvement of a factor of 10 over comparable line scan CCD sensors. The imager architecture utilizes three individual TDI arrays, with a new multi-layer dielectric interference film (DIF) color filter or a dyed polyamide patterned

Suhail Agwani; James Miller; Sawas G. Chamberlain; William D. Washkurak

1995-01-01

326

Students Schooling Students: Gaining Professional Benefits While Helping Urban High School Students Achieve Success  

Microsoft Academic Search

This article looks at the educational plight of urban low income children and explores the opportunities for success that small urban high schools provide. It then distills commonalities among successful small schools to demonstrate three central points: 1) that small is essential but not sufficient; 2) that small schools offer an opportunity for urban school districts to help improve educational

Susan P. Leviton; Justin A. Browne

2009-01-01

327

Preliminary Results from High-Gain Wide-Band Long-Period Electromagnetic Seismograph Systems.  

National Technical Information Service (NTIS)

Wide-band long-period seismographs with peak magnification up to 500,000 at 30-40 sec have been installed in an airtight chamber in a deep mine. The rigid environmental control allows for relatively noise-free output at high magnifications. The seismogram...

P. W. Pomeroy G. Hade J. Saving R. Chander

1968-01-01

328

Judicial Setbacks, Material Gains: Terror Litigation at the Israeli High Court of Justice  

Microsoft Academic Search

Recent research indicates that even in countries with strong judicial review, supreme courts have proved reluctant to oppose restrictions on civil liberties in times of war, or in crises that resemble war?like emergencies. Accordingly, most research conducted on the Israeli High Court of Justice argues that despite using the rhetoric of human rights, the HCJ rarely intervenes in security?based decisions

Menachem Hofnung; Keren Weinshall Margel

2010-01-01

329

Electrochemical Biosensors Employing an Internal Electrode Attachment Site Achieve Reversible, High Gain Detection of Specific Nucleic Acid Sequences  

PubMed Central

Electrochemical DNA (E-DNA) sensors, which are rapid, reagentless and readily integrated into microelectronics and microfluidics, appear a promising alternative to optical methods for the detection of specific nucleic acid sequences. Keeping with this, a large number of distinct E-DNA architectures have been reported to date. Most, however, suffer from one or more drawbacks, including low signal gain (the relative signal change in the presence of complementary target), signal-off behavior (target binding reduces the signaling current, leading to poor gain and raising the possibility that sensor fouling or degradation can lead to false positives) or instability (degradation of the sensor during regeneration or storage). To remedy these problems, we report here the development of a signal-on E-DNA architecture that achieves both high signal gain and good stability. This new sensor employs a commercially synthesized, asymmetric hairpin DNA as its recognition and signaling probe, the shorter arm of which is labeled with a redox reporting methylene blue at its free end. Unlike all prior E-DNA architectures, in which the recognition probe is attached via a terminal functional group to its underlying electrode, the probe employed here is affixed using a thiol group located internally, in the turn region of the hairpin. Hybridization of a target DNA to the longer arm of the hairpin displaces the shorter arm, allowing the reporter to approach the electrode surface and transfer electrons. The resulting device achieves signal increases of ~800% at saturating target, a detection limit of just 50 pM and ready discrimination between perfectly matched sequences and those with single nucleotide polymorphisms. Moreover, because the hairpin probe is a single, fully covalent strand of DNA, it is robust to the high stringency washes necessary to remove the target, and thus these devices are fully reusable.

Rowe, Aaron A.; Chuh, Kelly N.; Lubin, Arica A.; Miller, Erin A; Cook, Brett; Hollis, Daniel; Plaxco, Kevin W.

2011-01-01

330

High-gain wide-viewing-angle null-hot-spot optical diffuser useful for display screen application  

NASA Astrophysics Data System (ADS)

A high-gain, wide-viewing-angle optical diffuser without hot spots is presented. Such type of optical diffuser has potential applications in front and rear projection screens, LED display illumination, LCD backlights, beam homogenizer, etc. By shaping the diffused light pattern to be elliptical, high-gain is achieved by narrowing and thus enhancing 1D intensity distribution while the other dimension satisfies the wide-viewing-angle requirement. Optical diffuser can be implemented by illuminating a ground glass and recording the speckle pattern on a photoresist plate. Shaping the diffuser light pattern of resultant optical diffuser can be conveniently controlled by shaping the illuminating light pattern on ground glass. However the diffuser must be optimized such that hot spots can be totally eliminated. For surface relief optical diffusers, surface-roughness is the major factor affecting elimination of hot spots and, hence, efficiency of optical diffuser. Suitable exposure and development conditions for controlling surface roughness are investigated. After this recording process, a nickel plate is electro-formed from the photoresist plate. Under our design conditions, the nickel plate is measured to be with viewing-angle of 100 degree(s) horizontal X 40 degree(s) vertical (full angular width of 1/10 maximum) and gain of 5.24 (relative to 3M's wall screen). Hot spots are totally suppressed. Such plate can be used as master in industrial embossing processes for mass production. Controllability and simplicity in design and manufacture would make such optical diffuser very attractive for display screen as well as other applications mentioned above.

Lin, Hoang Yan; Tyan, Wann-Diiang; Lu, Ying-Tsung

1996-09-01

331

Design of high gain Er3+-Yb3+-Ce3+ co-doped ZELA fluoride glass waveguide amplifier  

NASA Astrophysics Data System (ADS)

This paper reports an accurate design of Er3+-Yb3+-Ce3+ doped ZrF4-ErF3-LaF3-AlF3 (ZELA) fluoride glass channel amplifier operating in the third window of the telecommunication systems. By considering measured spectroscopic and optical parameters, we demonstrate the feasibility of a novel optical waveguide amplifier exhibiting high gain and low noise figure. The electromagnetic investigation has been carried-out by employing a full-vector Finite Element Method (FEM) solver. The mode electromagnetic field, calculated at different wavelengths, constitutes the input data for the home-made numerical code which solves both the power propagation and population rate equations via a Runge-Kutta based iterative algorithm. The dependence of the up-conversion coefficients on erbium concentration are taken into account. In the simulations, the core shape, the waveguide length, the input pump and signal powers, the erbium and the ytterbium concentration are varied with the aim to optimize the amplifier performance. The goal of achieving high gain with a short device length is demonstrated. In particular, the simulation results show that the waveguide amplifier exhibits an optimal internal gain value close to 22.5 dB and a noise figure of 4.1 dB for a waveguide amplifier 5.5 cm long, an erbium concentration of NEr=2.5×1026 ions/m3, ytterbium concentration NYb=2.4×1026 ions/m3, NCe=6×1026 ions/m3, an input pump power Pp=100 mW and an input signal power Ps=1 ?W.

Prudenzano, F.; Allegretti, L.; De Sario, M.; Mescia, L.; Palmisano, T.; Ferrari, M.; Chiasera, A.; Jestin, Y.; Boulard, B.; Péron, O.

2008-05-01

332

The Anorexic Effect of High Altitude on Weight Gain, Nitrogen Retention and Body Composition of Rats  

Microsoft Academic Search

The effects of translocation to high altitude on growth rate, nitro gen retention and body composition were studied in meal-eating albino rats. Ad libi turn-fed, meal-eating rats were rapidly (2.25 hours) translocated from Denver (1,600 meters) to Pikes Peak (4,300 meters), Colorado, and were killed 2, 6 or 14 days later. Identical ad libitum and pair-fed, meal-eating control groups were

D. D. SCHNAKENBERG; L. F. KRABILL; ANDP. C. WEISER

2009-01-01

333

High gain-bandwidth-product avalanche photodiodes for multigigabit\\/s data rates  

Microsoft Academic Search

For long-wavelength (1.3 ?m and 1.5 ?m) high-bit-rate (?400 Mbit\\/s) lightwave systems the highest receiver sensitivities have been achieved with III-V compound avalanche photodiodes with separate absorption and multiplication regions (SAM-APDs). Initial APDs of this type exhibited poor frequency response owing to charge accumulation at the heterojunction interfaces. A significant improvement in the bandwidth was achieved by introducing a transition

J. C. Campbell

1987-01-01

334

High gain-bandwidth-product avalanche photodiodes for multigigabit\\/s data rates  

Microsoft Academic Search

For long-wavelength (1.3 mum and 1.5 mum) high-bit-rate (>~400 Mbit\\/s) lightwave systems the highest receiver sensitivities have been achieved with III-V compound avalanche photodiodes with separate absorption and multiplication regions (SAM-APDs). Initial APDs of this type exhibited poor frequency response owing to charge accumulation at the heterojunction interfaces. A significant improvement in the bandwidth was achieved by introducing a transition

J. C. Campbell

1987-01-01

335

Simulated high altitude selectively decreases protein intake and lean mass gain in rats  

Microsoft Academic Search

The aim of this study was to find out whether high altitude (HA)-induced hypophagia was macronutrient-specific using a self-selection procedure. Body composition was assessed by dual X-ray absorptiometry before and after exposure and by dissection at the end of the experiment. Energy intake, macronutrient selection, body composition, plasma insulin and leptin concentrations were measured in rats (FHx) exposed 16 h

Olivier E. Morel; Roberte Aubert; Jean-Paul Richalet; Didier Chapelot

2005-01-01

336

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

NASA Astrophysics Data System (ADS)

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.

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

1990-09-01

337

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

338

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

339

Bremsstrahlung emission of high energy accompanying spontaneous fission of {sup 252}Cf  

SciTech Connect

The study of the bremsstrahlung photon emission accompanying fragments produced in the spontaneous fission of heavy nuclei by a fully quantum approach is presented for the first time. This kind of problem requires the knowledge of wave functions of the fissioning system leading to a wide distribution of couples of fragments that are the products of fission. With the aim of obtaining these wave functions, the interaction potential between the emitted fragment and residual nucleus is calculated by a standard approach. A new procedure was performed that allows an increase in the accuracy of calculations of radial integrals in the far asymptotic region and the achievement of the convenient convergence in calculations of the spectra. The total probability of the emitted photons in the spontaneous fission of {sup 252}Cf was calculated in such a way. We obtained good agreement between theory and experimental data up to 38 MeV for the bremsstrahlung spectrum of photons while the calculation of the total probability of photon emission accompanying fragments was performed up to an energy of 60 MeV. The analysis of contributions in the bremsstrahlung spectrum accompanying the emission of light, medium, and heavy fragments in the fission of {sup 252}Cf is presented.

Maydanyuk, S. P.; Olkhovsky, V. S.; Mandaglio, G.; Manganaro, M.; Fazio, G.; Giardina, G. [Institute for Nuclear Research, National Academy of Science of Ukraine, Kiev 03680 (Ukraine); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy) and Istituto Nazionale di Fisica Nucleare, Sezione di Catania, I-95123 Catania (Italy)

2010-07-15

340

Bremsstrahlung emission of high energy accompanying spontaneous fission of Cf252  

NASA Astrophysics Data System (ADS)

The study of the bremsstrahlung photon emission accompanying fragments produced in the spontaneous fission of heavy nuclei by a fully quantum approach is presented for the first time. This kind of problem requires the knowledge of wave functions of the fissioning system leading to a wide distribution of couples of fragments that are the products of fission. With the aim of obtaining these wave functions, the interaction potential between the emitted fragment and residual nucleus is calculated by a standard approach. A new procedure was performed that allows an increase in the accuracy of calculations of radial integrals in the far asymptotic region and the achievement of the convenient convergence in calculations of the spectra. The total probability of the emitted photons in the spontaneous fission of Cf252 was calculated in such a way. We obtained good agreement between theory and experimental data up to 38 MeV for the bremsstrahlung spectrum of photons while the calculation of the total probability of photon emission accompanying fragments was performed up to an energy of 60 MeV. The analysis of contributions in the bremsstrahlung spectrum accompanying the emission of light, medium, and heavy fragments in the fission of Cf252 is presented.

Maydanyuk, S. P.; Olkhovsky, V. S.; Mandaglio, G.; Manganaro, M.; Fazio, G.; Giardina, G.

2010-07-01

341

Preparation of highly water-repellent surface by spontaneous formation of double scale roughness pattern.  

PubMed

Hydrophobic organic-inorganic hybrid composite suspensions were prepared by mixing hydrophobic octylsilyl titanium dioxide particles having average diameter of 35 nm with drying oil or moisture cure room temperature vulcanization silicone gum in volatile silicone. They were spread on a glass plate by using a linear motor coater and an applicator. Spatially periodic stripe patterns parallel to the direction of dragging the applicator were usually generated. The phenomenon is called directional viscous fingering, i.e. spontaneous pattern formation by the growth of fluctuation in morphology of mobile interface during the dragging coat. The pattern spontaneously formed on the surface became double scale when stored samples were coated. In this case, the large scale spatially periodic pattern was formed by the directional viscous fingering and the small ragged random pattern may be due to the giant molecules formed by cross-linking of silicone gum. Double scale roughness patterns were also generated by double dragging coat. The large and small scale pattern was formed by the first and second dragging coat, respectively. The formation of double scale roughness enhanced the water-repellent property of the hydrophobic surface. In some cases, water contact angle increased by 20 degrees to realize super water-repellent surface with a value exceeding 150 degrees. PMID:20103981

Joly, Pascal; Kuroda, Akihiro; Asakura, Kouichi

2010-01-01

342

Insights Gained from Modeling High-Grade Glioma in the Mouse  

PubMed Central

High grade gliomas (HGG) are devastating primary brain tumors with universally poor prognoses. Advances toward effective treatments require improved understanding of pathogenesis and relevant model systems for preclinical testing. Mouse models for HGG provide physiologically relevant experimental systems for analysis of HGG pathogenesis. There are advantages and disadvantages to the different methodologies used to generate such models, including implantation, genetic engineering or somatic gene transfer approaches. This review highlights how mouse models have provided insights into the contribution of specific mutations to tumor initiation, progression, and phenotype, the influence of tumor microenviroment, and the analysis of cell types that can give rise to glioma. HGGs are a highly heterogeneous group of tumors, and the complexity of diverse mutations within common signaling pathways as well as the developmental and cell-type context of transformation contribute to the overall diversity of glioma phenotype. Enhanced understanding of the mutations and cell types giving rise to HGG, along with the ability to design increasingly complex mouse models that more closely approximate the process of human gliomagenesis will continue to provide improved experimental systems for dissecting mechanisms of disease pathogenesis and for preclinical testing.

Rankin, Sherri L.; Zhu, Guo; Baker, Suzanne J.

2011-01-01

343

Effects of Dietary Fibers on Weight Gain, Carbohydrate Metabolism and Gastric Ghrelin Gene Expression in High Fat Diet Fed Mice  

PubMed Central

Diets that are high in dietary fiber are reported to have substantial health benefits. We sought to compare the metabolic effects for three types of dietary fibers, i.e. sugar cane fiber (SCF), psyllium (PSY) and cellulose (CEL) on body weight, carbohydrate metabolism and stomach ghrelin gene expression in a high-fat diet fed mouse model. Thirty-six male mice (C57BL/6) were randomly divided into four groups that consumed high fat-diets or high fat diet containing 10% SCF, PSY, and CEL respectively. After baseline measurements were assessed for body weight, plasma insulin, glucose, leptin and glucagon-like peptide-1 (GLP-1), animals were treated for 12 weeks. Parameters were re-evaluated at end of study. Whereas there was no difference at the baseline, body weight gains in the PSY and SCF groups were significantly lower than in CEL group at end of study, No difference in body weight was observed between the PSY and SCF animals. Body composition analysis demonstrated that fat mass in the SCF group was considerably lower than in the CEL and HFD groups. In addition, fasting plasma glucose and insulin and areas under curve of IPGTT were also significantly lower in the SCF and PSY groups than in the CEL and HFD groups. Moreover, fasting plasma concentrations of leptin were significantly lower and GLP-1 level was two-fold higher in the SCF and PSY mice than in the HFD and CEL mice. Ghrelin mRNA levels of stomach in SCF groups were significantly lower than in CEL and HFD groups as well. These results suggest differences in response to dietary fiber intake in this animal model as high fat diets incorporating dietary fibers such as SCF and PSY appeared to attenuate weight gain, enhance insulin sensitivity, and modulate leptin and GLP-1 secretion and gastric ghrelin gene expression.

Wang, Zhong Q.; Zuberi, Aamir; Zhang, Xian H.; Macgowan, Jacalyn; Qin, Jianhua; Ye, Xin; Son, Leslie; Wu, Qinglin; Lian, Kun; Cefalu, William T.

2009-01-01

344

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

345

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

2012-12-06

346

Design considerations of a voltage-fed full bridge DC-DC converter with high voltage gain for fuel cell applications  

Microsoft Academic Search

Fuel cells in the kW range have a high output current and low output voltage. To connect them to the mains, a DC-DC converter with a high voltage gain and an inverter are needed. In this paper an investigation of the voltage-fed full bridge dc-dc converter with high voltage gain is presented. A detailed analysis of the different operating modes,

Andreas AVERBERG; Axel MERTENS

2007-01-01

347

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

348

High-resolution SNP arrays in mental retardation diagnostics: how much do we gain?  

PubMed Central

We used Affymetrix 6.0 GeneChip SNP arrays to characterize copy number variations (CNVs) in a cohort of 70 patients previously characterized on lower-density oligonucleotide arrays affected by idiopathic mental retardation and dysmorphic features. The SNP array platform includes ?900?000 SNP probes and 900?000 non-SNP oligonucleotide probes at an average distance of 0.7?Kb, which facilitates coverage of the whole genome, including coding and noncoding regions. The high density of probes is critical for detecting small CNVs, but it can lead to data interpretation problems. To reduce the number of false positives, parameters were set to consider only imbalances >75?Kb encompassing at least 80 probe sets. The higher resolution of the SNP array platform confirmed the increased ability to detect small CNVs, although more than 80% of these CNVs overlapped to copy number ‘neutral' polymorphism regions and 4.4% of them did not contain known genes. In our cohort of 70 patients, of the 51 previously evaluated as ‘normal' on the Agilent 44K array, the SNP array platform disclosed six additional CNV changes, including three in three patients, which may be pathogenic. This suggests that about 6% of individuals classified as ‘normal' using the lower-density oligonucleotide array could be found to be affected by a genomic disorder when evaluated with the higher-density microarray platforms.

Bernardini, Laura; Alesi, Viola; Loddo, Sara; Novelli, Antonio; Bottillo, Irene; Battaglia, Agatino; Digilio, Maria Cristina; Zampino, Giuseppe; Ertel, Adam; Fortina, Paolo; Surrey, Saul; Dallapiccola, Bruno

2010-01-01

349

Conditioned tone control of brain reward behavior produces highly specific representational gain in the primary auditory cortex  

PubMed Central

Primary sensory cortices have been assumed to serve as stimulus analyzers while cognitive functions such as learning and memory have been allocated to “higher” cortical areas. However, the primary auditory cortex (A1) is now known to encode the acquired significance of sound as indicated by associatively-induced specific shifts of tuning to the frequencies of conditioned stimuli (CS) and gains in area of CS representations. Rewarding brain stimulation can be a very powerful motivator and brain reward systems have been implicated in addictive behavior. Therefore, it is possible that a cue for brain reward will gain cortical territory and perhaps thereby increase its control of subsequent behavior. To investigate the effect of brain reward on cortical organization, adult male rats (n = 11) were first tested with varying amounts of stimulation of the ventral tegmental area (VTAstm) to generate sigmoidal psychometric functions of nose poke (NP) rates as a function of reward magnitude (duration). Next, we attempted to accomplish tone control of NPs by maintaining intertrial NPs using a low reward duration and presenting a 20 s tone (2.0 kHz, 70 dB) which signaled an increase in reward to a high magnitude 10 s after tone onset. Tone control was demonstrated by a significant increase in the rate of NPs during the first 10 s of tone presentation, which anticipated the delivery of the high magnitude of reward. Tone control was achieved in seven of 11 subjects. This was accompanied by a highly specific and significant gain in representational area, specifically for the half-octave range centered on the CS frequency. However, this plasticity developed only in tone-controlled (TC) animals. The auditory cortex of non-tone-controlled subjects (n = 4) did not differ from that of naïve controls (n = 9) although their VTAstm was as rewarding as for the TC group. These findings reveal that auditory instrumental behavior can be controlled by rewarding VTAstm and that such control appears necessary for the highly specific recruitment of cortical cells to increase the representation of a sound that acquires behavioral importance.

Hui, Gabriel K.; Wong, Kwan L.; Chavez, Candice M.; Leon, Matthew I.; Robin, Kinna M.; Weinberger, Norman M.

2010-01-01

350

Multimode theory of pulsed-twin-beam generation using a high-gain fiber-optical parametric amplifier  

NASA Astrophysics Data System (ADS)

We theoretically investigate the quantum-noise properties of a pulse-pumped high-gain-fiber optical parametric amplifiers (FOPAs) by using the Bogoliubov transformation in multiple frequency modes to describe the evolution of the nondegenerate signal and idler twin beams. The results show that the noise figure of the FOPA is generally greater than the 3 dB quantum limit unless the joint spectral function is factorable and the spectrum of the input signal well matches the gain spectrum in the signal band. However, the intensity-difference noise of the twin beams, which weakly depends on the joint spectral function, can be significantly less than the shot-noise limit when the temporal modes of the pump and the input signal are properly matched. Moreover, to closely resemble real experimental conditions, the quantum noise of twin beams generated from a broadband FOPA is numerically studied by taking the various kinds of experimental imperfections into account. Our study is not only useful for developing a compact fiber source of twin beams, but also helpful for understanding the quantum-noise limit of a pulse-pumped FOPA in the fiber communication system.

Guo, Xueshi; Li, Xiaoying; Liu, Nannan; Ou, Z. Y.

2013-08-01

351

Detection of spontaneous class-specific visual stimuli with high temporal accuracy in human electrocorticography.  

PubMed

Most brain-computer interface classification experiments from electrical potential recordings have been focused on the identification of classes of stimuli or behavior where the timing of experimental parameters is known or pre-designated. Real world experience, however, is spontaneous, and to this end we describe an experiment predicting the occurrence, timing, and types of visual stimuli perceived by a human subject from electrocorticographic recordings. All 300 of 300 presented stimuli were correctly detected, with a temporal precision of order 20 ms. The type of stimulus (face/house) was correctly identified in 95% of these cases. There were approximately 20 false alarm events, corresponding to a late 2nd neuronal response to a previously identified event. PMID:19964434

Miller, Kai J; Hermes, Dora; Schalk, Gerwin; Ramsey, Nick F; Jagadeesh, Bharathi; den Nijs, Marcel; Ojemann, Jeffrey G; Rao, Rajesh P N

2009-01-01

352

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

PubMed Central

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

2012-01-01

353

Broadband, high gain two-stage optical parametric chirped pulse amplifier using BBO crystals for a femtosecond high-power Ti:sapphire laser system  

Microsoft Academic Search

We design a two-stage non-collinear optical parametric chirped pulse amplifier using BBO crystals for a high-power Ti:sapphire laser system, and numerically analyze the output characteristics of the OPCPA system. We find optimal phase-matching conditions and calculate the parametric gains as a function of pump intensity and interaction length. By constructing a two-stage OPCPA system using two BBO crystals, we obtain

Jin Woo Yoon; Seong Ku Lee; Tae Jun Yu; Jae Hee Sung; Tae Moon Jeong; Jongmin Lee

354

Renalase mRNA levels in the brain, heart, and kidneys of spontaneously hypertensive rats with moderate and high hypertension.  

PubMed

Background Renalase is a recently discovered secretory protein involved in regulation of arterial blood pressure in humans and animals. Results of animal experiments from independent laboratories indicate that administration of human recombinant renalase decreases blood pressure and some genetically predisposed hypertensive rats have lowered renalase levels. Material and Methods The levels of renalase mRNA expression in brain hemispheres, heart, and kidneys of spontaneously hypertensive rats (SHR) with moderate (140-180 mm Hg) or high (>180 mm Hg) hypertension and of control Wistar-Kyoto (WKY) rats were analyzed using real-time PCR. Results Spontaneously hypertensive rats with high hypertension (>180 mm Hg) had a lower renalase mRNA level in brain hemispheres, and higher heart and kidney renalase mRNA levels compared with control WKY rats. In SHR with a moderate increase in arterial blood pressure (140-180 mm Hg), the tissue renalase mRNA changed in the same direction but did not reach the level of statistical significance as compared with control rats. Conclusions The results indicate that the development of hypertension in SHR is accompanied by altered expression of the renalase gene in the examined organs as compared with control WKY rats. The brain and peripheral tissues renalase mRNA levels demonstrate opposite trends, which are obviously crucial for impaired regulation of blood pressure in SHR. PMID:24113803

Fedchenko, Valerii; Globa, Alexander; Buneeva, Olga; Medvedev, Alexei

2013-10-11

355

Renalase mRNA levels in the brain, heart, and kidneys of spontaneously hypertensive rats with moderate and high hypertension  

PubMed Central

Background Renalase is a recently discovered secretory protein involved in regulation of arterial blood pressure in humans and animals. Results of animal experiments from independent laboratories indicate that administration of human recombinant renalase decreases blood pressure and some genetically predisposed hypertensive rats have lowered renalase levels. Material/Methods The levels of renalase mRNA expression in brain hemispheres, heart, and kidneys of spontaneously hypertensive rats (SHR) with moderate (140–180 mm Hg) or high (>180 mm Hg) hypertension and of control Wistar-Kyoto (WKY) rats were analyzed using real-time PCR. Results Spontaneously hypertensive rats with high hypertension (>180 mm Hg) had a lower renalase mRNA level in brain hemispheres, and higher heart and kidney renalase mRNA levels compared with control WKY rats. In SHR with a moderate increase in arterial blood pressure (140–180 mm Hg), the tissue renalase mRNA changed in the same direction but did not reach the level of statistical significance as compared with control rats. Conclusions The results indicate that the development of hypertension in SHR is accompanied by altered expression of the renalase gene in the examined organs as compared with control WKY rats. The brain and peripheral tissues renalase mRNA levels demonstrate opposite trends, which are obviously crucial for impaired regulation of blood pressure in SHR.

Fedchenko, Valerii; Globa, Alexander; Buneeva, Olga; Medvedev, Alexei

2013-01-01

356

Rats on a high-energy diet showing no weight gain present with ultrastructural changes associated with liver fibrosis.  

PubMed

Sibutramine is widely used as a weight-loss substance in the treatment of obesity and is a selective inhibitor of the neuronal reuptake of serotonin and noradrenaline. Although banned, it is often a hidden ingredient in herbal and dietary supplements that are widely used by the general public. Various weight loss products, including sibutramine, have successfully been tested in animal models of diet-induced obesity. In the female Sprague-Dawley rat model, fed a high-energy diet that did not produce a significant increase in BMI, the cellular structure of the liver was evaluated using transmission electron microscopy. Compared to controls showing no damage, the livers of rats fed a high-energy diet were found to have increased fibrosis without steatosis, while for rats fed high-energy diet with sibutramine, fibrosis was increased and steatosis had developed. In conclusion, in female rats fed a high-energy diet that does not result in weight gain hepatic fibrosis occurs without steatosis. In these rats the co-administration of sibutramine increases the degree of fibrosis and steatosis develops. Although it has been widely believed that sibutramine is not hepatotoxic, this study clearly shows that at an ultrastructural level, rats fed a high-energy diet treated with sibutramine show signs of hepatotoxicity. PMID:23672266

Oberholzer, Hester Magdalena; Bester, Megan Jean; van der Schoor, Ciska

2013-05-14

357

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-rays 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 small 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.; /SLAC; Kim, K.-J.; /Argonne; Piot, P.; /Northern Illinois U. /Fermilab

2006-09-21

358

Interpretation of wave-profile modification measurements in high-gain raman free-electron-laser experiments  

NASA Astrophysics Data System (ADS)

This paper presents a theoretical analysis of wave-profile modification measurements in FELs, using data that was reported recently [Phys. Rev. Lett. 59 (1987) 1177]. The results are related to a high-gain Raman free-electron laser, operating at long wavelengths (~ 3 cm). Two possible mechanisms for wave-profile modification were examined. One is the known e-beam optical guiding effect. The other is that of the transverse electrostatic fields (TEF), excited by the bunched electron beam. The numerical results suggest that in the above-mentioned reference the measured wave-profile modification was predominantly a consequence of the TEF components. An experimental setup for verification of this analysis is proposed.

Jerby, E.; Gover, A.

1989-12-01

359

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

360

Spontaneous and stimulated Raman scattering near metal nanostructures in the ultrafast, high-intensity regime  

NASA Astrophysics Data System (ADS)

The inclusion of atomic inversion in Raman scattering can significantly alter field dynamics in plasmonic settings. Our calculations show that large local fields and femtosecond pulses combine to yield: (i) population inversion within hot spots; (ii) gain saturation; and (iii) conversion efficiencies characterized by a switch-like transition to the stimulated regime that spans twelve orders of magnitude. While in Raman scattering atomic inversion is usually neglected, we demonstrate that in some circumstances full accounting of the dynamics of the Bloch vector is required.

Scalora, M.; Vincenti, M. A.; de Ceglia, D.; Grande, M.; Haus, J. W.

2013-10-01

361

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

Microsoft Academic Search

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

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

2001-01-01

362

A solid immersion interference lithography system for imaging ultra-high numerical apertures with high-aspect ratios in photoresist using resonant enhancement from effective gain media  

NASA Astrophysics Data System (ADS)

In the last year our Solid Immersion Lloyd's Mirror Interference Lithography (SILMIL) system has proved to be a successful tool for evanescent interferometric lithography (EIL). The initial goal was to use SILMIL in conjunction with the surface plasmon polariton (SPP) surface states at the resist-metal interface. Through this resonance, we aimed to counter the decay of evanescent images created using EIL. By analyzing the theory in greater detail we were able to develop a better understanding of the resonance phenomena. In this paper, details of the design of SILMIL and how one may utilize it to produce ultra-high numerical apertures (NAs) are given, as well as an introduction to the resonance phenomena and the mechanism behind it. We introduce a new method that requires a gain medium (one that has a negative loss) to achieve significant enhancements, and present an effective gain medium by using a high-index dielectric on low-index media. We present results at ? = 405 nm using such an effective gain medium and also provide a feasible design example at the lithography standard ? = 193 nm.

Mehrotra, Prateek; Mack, Chris A.; Blaikie, Richard J.

2012-03-01

363

Demagnetization of a Bi-2223 high-temperature superconducting coil in RT-1 through spontaneous temperature rise  

NASA Astrophysics Data System (ADS)

The Ring Trap 1 (RT-1) device produces a magnetospheric configuration for the confinement of a high- ? plasma with a Bi-2223 high-temperature superconducting magnet. Here we report the results of emergency demagnetization of the superconducting coil, where we could not connect current leads, temperature measurement connectors, and connectors for a persistent-current switch (PCS) heater to the coil. The spontaneous warming of the coil caused a rise in the flux-flow resistance of the superconducting coil, and the persistent current slowly decreased as coil resistance increased. Approximately 98% of the total stored magnetic energy was safely released before the quenching of the PCS, and there was no substantial damage to the superconducting coil.

Saitoh, H.; Yoshida, Z.; Ogawa, Y.; Morikawa, J.; Yano, Y.; Mizushima, T.; Mizumaki, S.; Tosaka, T.

2012-01-01

364

Submonolayer InGaAs/GaAs quantum-dot lasers with high modal gain and zero-linewidth enhancement factor  

NASA Astrophysics Data System (ADS)

The gain spectra of a submonolayer (SML) InGaAs/GaAs quantum dot (QD) laser working at 30°C were measured using the Hakki-Paoli method. It is found that the maximum modal gain of QD ground states is as high as 44 cm-1 and no gain saturation occurs below the threshold at the lasing wavelength of 964.1 nm. When the injection current is about 0.98 times the threshold, the gain spectrum becomes symmetric with respect to the lasing wavelength, and zero-linewidth enhancement factor is observed. These properties are attributed to the high density and the high uniformity of SML QDs in our laser diode.

Xu, Zhangcheng; Birkedal, Dan; Juhl, Michael; Hvam, Jørn M.

2004-10-01

365

Purine deoxynucleoside metabolism in human melanoma cells with a high spontaneous mutation rate.  

PubMed

A human melanoma cell line (MM96L) had a spontaneous mutation rate at the HGPRT locus of approx. 7 times normal. The cells had elevated dATP and dGTP pools, lacked purine nucleoside phosphorylase (PNP) and were sensitive to killing by deoxyadenosine, deoxyinosine and related purines but not to inosine or hypoxanthine. Four other melanoma cell lines exhibited a range of nucleoside sensitivities and dNTP pool sizes. Failure of intact MM96L cells to degrade exogenous deoxyadenosine and deoxyinosine to hypoxanthine was confirmed by NMR of culture medium. Normal melanocytes were PNP+ and were insensitive to deoxyinosine. Comparison of the metabolites of [14C]deoxyinosine from MM96L and a PNP+ cell line of similar doubling time (HeLa) showed that both cell types produced 14C-labelled guanine and adenine nucleotides, with [14C]dATP and [14C]dADP being found in MM96L. This indicates that human sAMP synthetase or a similar enzyme catalyses the conversion of dIMP to dAMP, the resultant elevation of dATP causing base misincorporation and a mutator phenotype. PMID:8657185

Musk, P; Clark, J M; Thompson, D; Dunn, I S; Christopherson, R I; Szabados, E; Rose, S E; Parsons, P G

1996-02-19

366

Gain switching of semiconductor injection lasers  

SciTech Connect

The limiting factors in short pulse generation by gain switching of semiconductor lasers are analyzed using an approach parallel to conventional Q switching analysis. The dependence of the gain-switched pulse width and pulse energy on various input parameters such as drive current amplitude, bias current, and spontaneous emission factor, etc., can be predicted in a simple manner.

Lau, K.Y.

1988-01-25

367

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

368

Nonseparable Werner states in spontaneous parametric down-conversion  

SciTech Connect

The multiphoton states generated by high-gain spontaneous parametric down-conversion (SPDC) in the presence of large losses are investigated theoretically and experimentally. The explicit form for the two-photon output state has been found to exhibit a Werner structure very resilient to losses for any value of the nonlinear gain parameter g. The theoretical results are found to be in agreement with experimental data obtained by 'entanglement witness' methods and by the quantum tomography of the state generated by a high-g SPDC.

Caminati, Marco; De Martini, Francesco; Perris, Riccardo; Secondi, Veronica [Dipartimento di Fisica, Universita 'La Sapienza', Rome 00185 (Italy); Sciarrino, Fabio [Centro di Studi e Ricerche 'Enrico Fermi', Via Panisperna 89/A, Compendio del Viminale, Rome 00184 (Italy); Dipartimento di Fisica, Universita 'La Sapienza', Rome 00185 (Italy)

2006-03-15

369

Design of Photomultiplier Socket Assembly with High Gain and Clean Output Signals for Tubes Viewing Organic Scintillator Light Pulses  

Microsoft Academic Search

Two of the major problems in designing a socket assembly for a 56AVP photomultiplier viewing light pulses from an organic scintillator have been investigated. They are (1) optimization of the dynode voltage distributions for gain and pulse shape over a wide range of tube gains, and (2) proper grounding of the dynode bypass capacitors and coupling of the coaxial signal

William A. Gibson

1966-01-01

370

A 71 dB Gain, High Efficiency Relativistic Klystron using a High Current Linear Accelerator Traveling Wave Buncher Output Structure  

NASA Astrophysics Data System (ADS)

After five years of operation, the 17 GHz MKII relativistic klystron in service at the MIT Plasma Science and Fusion Center was upgraded with a new output structure to provide a common source of high peak power for continuing operation of the 17 GHz linac, for RF gun testing and for energizing a recently developed circularly polarized beam deflection RF system to evaluate the ultra short electron bunch performance of the linac. The salient features of the impedance and phase velocity tapered new traveling wave output structure designed for high gain and stability are described; and initial high power test results of the 17 GHz relativistic klystron are presented. The output structure was designed as a beam driven bunching and phase shifting 2?/3 mode circuit using codes that were developed over a 40 year period designing, fabricating and testing high current traveling wave linac bunchers. The electrical length of the new (MKIII) output circuit was extended to 1200 degrees using a group to phase velocity harmonic mean ratio of 0.124 to provide total skin losses of less than 5 percent and a phase/frequency sensitivity of only 0.6 degree/MHz. A dual feed racetrack shaped output cavity having a decelerating gradient of 150 kV/cm and beam apertures substantially larger than ?0/2, to allow reduction of space charge debunching forces, are added advantages of this 25 MW, 71 dB gain RF amplifier.

Haimson, J.; Mecklenburg, B.

2003-12-01

371

Spontaneous nucleophilic addition of hydroxide ions to the meso-position of high-valent antimony-oxo porphyrin complexes.  

PubMed

Bimolecular reactions of the antimony(V) porphyrin complexes SbO(tpp)OH, 1 and SbO(oep)OH, 2 with tetra-n-butylammonium hydroxide were investigated at 298 K in acetonitrile solution (tpp, dianion of 5,10,15,20-tetraphenylporphyrin and oep, dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin). Spontaneous nucleophilic addition of hydroxide ions to the non-oxidized porphyrin macrocycle leads to novel hydroxyphlorin derivatives, which contain a saturated meso-carbon bridge. While this process is a reversible equilibrium reaction for the TPP derivative, the OEP complex undergoes subsequent demetallation and oxidative ring cleavage in the presence of dioxygen. Possible implications for the competitive inhibition of heme-oxygenase by high-valent metalloporphyrin therapeutics are discussed. PMID:11374594

Knör, G

2001-04-01

372

Planar InP-InGaAs avalanche photodetectors with n-multiplication layer exhibiting a very high gain-bandwidth product  

Microsoft Academic Search

A planar separate absorption, grading, charge, and multiplication (SAGCM) avalanche photodiode (APD) structure was designed and fabricated, allowing for an updoped multiplication layer without the use of guard rings. A very high gain-bandwidth (GBW) product of 93 GHz and DC gains exceeding 1000 have been measured for a 30-?m-diameter device. This GBW is, to the author's knowledge, the highest reported

L. E. Tarof

1990-01-01

373

Ultra-high-speed PLL-type clock recovery circuit based on all-optical gain modulation in traveling-wave laser diode amplifier  

Microsoft Academic Search

A new phase lock loop (PLL) is developed for very-high-speed optical timing extraction using traveling-wave laser-diode amplifier (TW-LDA) as a phase detector. The all-optical gain modulation of the TW-LDA is utilized to detect the relative phase difference between an optical signal and an optical clock The frequency response of the optical gain modulation measured with the optical heterodyne technique agrees

Satoki Kawanishi; Masatoshi Saruwatari

1993-01-01

374

Ultraviolet bandpass Al0.17Ga0.83N?GaN heterojunction phototransitors with high optical gain and high rejection ratio  

Microsoft Academic Search

Ultraviolet Al0.17Ga0.83N?GaN-based heterojunction phototransistors (HPTs) grown by metal-organic vapor-phase epitaxy were demonstrated. The HPTs showed a bandpass spectral responsivity ranging from 280 to 390 nm. With a bias voltage of 6 V, the responsivity at an incident of 340 nm was as high as 1500 A?W, corresponding to a quantum gain of 5.47×103. In contrast to GaN-based photoconductors, the HPTs

M. L. Lee; J. K. Sheu; Yung-Ru Shu

2008-01-01

375

Ultraviolet bandpass Al0.17Ga0.83N\\/GaN heterojunction phototransitors with high optical gain and high rejection ratio  

Microsoft Academic Search

Ultraviolet Al0.17Ga0.83N\\/GaN-based heterojunction phototransistors (HPTs) grown by metal-organic vapor-phase epitaxy were demonstrated. The HPTs showed a bandpass spectral responsivity ranging from 280 to 390 nm. With a bias voltage of 6 V, the responsivity at an incident of 340 nm was as high as 1500 A\\/W, corresponding to a quantum gain of 5.47×103. In contrast to GaN-based photoconductors, the HPTs

M. L. Lee; J. K. Sheu; Yung-Ru Shu

2008-01-01

376

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

2011-04-17

377

A study of the Rayleigh-Taylor instability in direct drive for LMJ high gain fusion targets  

NASA Astrophysics Data System (ADS)

A comparative study of the Rayleigh-Taylor instability at the ablation front during the acceleration stage was undertaken. The hydrodynamic behavior of two different types of high gain fusion capsules was investigated. The growth rate and surface roughness were inferred through the use of 1D simulations carried out with the hydrodynamics code FCI2, coupled to the Goncharov-Betti, Takabe and Haan models. The growth rates obtained by the Goncharov-Betti model are in good agreement with 2D simulation results. It is also shown that the ablative stabilisation term used in the Takabe relation is strongly material dependent with a value of 1.5 for CH and 2.5 for cryogenic DT. It appears clearly from this study that the 'all DT' target produces lower growth rates (1.9 ns-1) than the plastic target (3.9 ns-1). Finally, by applying the Haan saturation model, we reveal that the CH target is very likely to break-up while perturbations from the 'all DT' target are still kept below a safe level.

Meyer, Christophe; Canaud, Benoit; Fortin, Xavier; Garaude, Florence

2002-11-01

378

Kick and phase errors in spontaneous and amplified radiation.  

SciTech Connect

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

Kim, K.-J.

1999-08-31

379

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

380

The Relationship between the Degree of Participation in Online Embedded Professional Development Communities for High School Mathematics Teachers and Student Achievement Gains in College Algebra  

ERIC Educational Resources Information Center

This correlation study examines the relationship between participation in online embedded professional development communities and student achievement gains in a College Algebra course taught by high school teachers to high school students for college credit. The participating teachers met weekly through a web-based meeting format using…

Roher, Lee Alan Hanawalt

2009-01-01

381

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

Microsoft Academic Search

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

Peter C Rimensberger

2006-01-01

382

High-power short-pulse xenon dimer spontaneous radiation source  

SciTech Connect

A high-power VUV radiation source based on a self-sustained nanosecond volume discharge in an inhomogeneous electric field is developed. It is shown that the volume discharge can be formed at high xenon and helium pressures without using a preionisation source. The 8-ns (FWHM), 172-nm, 1-MW radiation pulses emitted into a total solid angle are obtained in xenon at a pressure of 12 atm. (vuv radiation sources)

Lomaev, Mikhail I; Rybka, D V; Tarasenko, Viktor F; Baksht, E Kh [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation); Mesyats, Gennadii A [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2007-06-30

383

Reconstitution of Spontaneous Neutralizing Antibody Response against Autologous Human Immunodeficiency Virus during Highly Active Antiretroviral Therapy  

Microsoft Academic Search

Longitudinal changes in neutralizing antibody responses against autologous human immuno- deficiency virus (HIV) type 1 were investigated in 19 chronically infected patients who were undergoing highly active antiretroviral therapy (HAART). Reconstitution of or increase in neutralization activity was observed in 4 of 19 patients during HAART, but neutralization activity was more or less unchanged in most patients. Three of 4

Tetsuya Kimura; Kazuhisa Yoshimura; Kumiko Nishihara; Yosuke Maeda; Shintaro Matsumi; Atsushi Koito; Shuzo Matsushita

2002-01-01

384

Polarization-sensitive opto-electronic devices based on spontaneous self-ordering in semiconductor alloys  

Microsoft Academic Search

Spontaneous self-ordering in semiconductor alloys is not only very interesting from the fundamental point of view but can also be exploited for device applications. We report on monolithically integrated opto-electronic switching devices with high photoconductive gain. The most interesting aspect of these devices is the fact that the switching behavior depends only on the polarization angle and not on the

Peter Kiesel; Jochen Spieler; Thomas Kippenberg; Moritz Müller; Gottfried H Döhler

2002-01-01

385

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

386

High frequency spontaneous production of doubled haploid plants in microspore cultures of Brassica rapa ssp. chinensis  

Microsoft Academic Search

Brassica rapa (syn. Brassica campestris) ssp. chinensis is an important vegetable crop, but it is relatively recalcitrant to microspore culture. One genotype each of B. rapa ssp. chinensis var. communisand var. utilis were used formicrospore culture. Embryo production of3.8–42.4 embryos\\/bud was obtained. A high rate of plant regeneration\\u000a directly from microspore-derived embryos without subculture was achieved by an improved protocol

H. H. Gu; W. J. Zhou; P. Hagberg

2003-01-01

387

Spontaneous division of dissipative solitons in a planar gas-discharge system with high ohmic electrode  

NASA Astrophysics Data System (ADS)

In this Letter we report on the division of electrical current filaments in a planar semiconductor gas-discharge system with high ohmic electrode that we refer to as dissipative solitons. The effect is observed for stationary and propagating, as well as for isolated and for dense arrangements of filaments. For large spatial density of dissipative solitons, processes of their generation and annihilation seem to give rise to a specific kind of spatio-temporal chaotic dynamics.

Astrov, Yu. A.; Purwins, H.-G.

2006-10-01

388

High-energy gamma-rays accompanying the spontaneous fission of $^{252}$ Cf  

Microsoft Academic Search

The $\\\\gamma $-ray spectrum of $^{252}$Cf(sf) was measured in the Darmstadt-Heidelberg Crystal Ball specrometer, with a double ionization chamber mounted inside to detect the fission fragments. The measurement was aimed at a better understanding of an unusual component found in the high-energy region between 3 and 8 MeV, with fragment mass splits near symmetry. This component was proved to be

A. Hotzel; P. Thirolf; Ch. Ender; D. Schwalm; M. Mutterer; P. Singer; M. Klemens; J. P. Theobald; M. Hesse; F. Gönnenwein; H. v. d. Ploeg

1996-01-01

389

Metamaterials with Gain  

NASA Astrophysics Data System (ADS)

Nanoplasmonic metamaterials are the key to an extreme control of light and allow us to conceive materials with negative or vanishing refractive index. Indeed, metamaterials enable a multitude of exciting and useful applications, such as subwavelength focusing, invisibility cloaking, and ``trapped rainbow'' stopping of light. The realization of these materials has recently advanced from the microwave to the optical regime. However, at optical wavelengths, metamaterials may suffer from high dissipative losses owing to the metallic nature of their constituent nanoplasmonic meta-molecules. It is therefore not surprising that overcoming loss restrictions by gain is currently one of the most important topics in metamaterials' research. At the same time, providing gain on the nanoplasmonic (metamolecular) level opens up exciting new possibilities such as a whole new type of metamaterial nano-laser with a cavity length of about a tenth of the wavelength. The talk gives an overview of the state of the art of gain-enhanced metamaterials. Particular focus will be placed on nano-plasmonic metamaterials (such as double-fishnet metamaterials) with integrated laser dyes as gain medium. The successful compensation of loss by gain is demonstrated on the meta-molecular level. On the basis of a comprehensive, microscopic Maxwell-Bloch Langevin approach of spatio-temporal light amplification and lasing in gain-enhanced nanoplasmonic (negative-index) metamaterials a methodology based on the discrete Poynting's theorem is introduced that allows dynamic tracing of the flow of electromagnetic energy into and out of ``microscopic'' channels (light field, plasmons, gain medium). It is shown that steady-state amplification can be achieved in nanoplasmonic metamaterials. Finally, a complex spatio-temporal interplay of light-field and coherent absorption dynamics is revealed in the lasing dynamics of a nanoplasmonic gain-enhanced double-fishnet metamaterial.

Hess, Ortwin

2012-02-01

390

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

391

Spontaneous Breakdown of Translational Symmetry in Quantum Hall Systems: Crystalline Order in High Landau Levels  

NASA Astrophysics Data System (ADS)

We report on results of systematic numerical studies of two-dimensional electron gas systems subject to a perpendicular magnetic field, with a high Landau level partially filled by electrons. Our results are strongly suggestive of a breakdown of translational symmetry and the presence of crystalline order in the ground state. This is in sharp contrast with the physics of the lowest and first excited Landau levels, and in good qualitative agreement with earlier Hartree-Fock studies. Experimental implications of our results are discussed.

Haldane, F. D. M.; Rezayi, E. H.; Yang, Kun

2000-12-01

392

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

393

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

PubMed

In this paper, we report, for the first time, an inherently gain-flattened discrete highly nonlinear photonic crystal fiber (HNPCF) Raman amplifier (HNPCF-RA) design which shows 13.7 dB of net gain (with +/-0.85-dB gain ripple) over 28-nm bandwidth. The wavelength dependent leakage loss property of HNPCF is used to flatten the Raman gain of the amplifier module. The PCF structural design is based on W-shaped refractive index profile where the fiber parameters are well optimized by homely developed genetic algorithm optimization tool integrated with an efficient vectorial finite element method (V-FEM). The proposed fiber design has a high Raman gain efficiency of 4.88 W(-1) . km(-1) at a frequency shift of 13.1 THz, which is precisely evaluated through V-FEM. Additionally, the designed module, which shows ultra-wide single mode operation, has a slowly varying negative dispersion coefficient (-107.5 ps/nm/km at 1550 nm) over the operating range of wavelengths. Therefore, our proposed HNPCF-RA module acts as a composite amplifier with dispersion compensator functionality in a single component using a single pump. PMID:19503154

Varshney, Shailendra; Fujisawa, Takeshi; Saitoh, Kunimasa; Koshiba, Masanori

2005-11-14

394

Gaining Acceptance  

ERIC Educational Resources Information Center

Back in the 1990s, when Bill Clinton was president and the internet was still a novelty, college recruitment was remarkably low-tech. Most prospective students visited high school guidance offices, wrote away for information about schools, attended college fairs, and visited campuses they were considering. Most admissions and recruiting activities…

Villano, Matt

2007-01-01

395

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

396

SPONTANEOUS CATALYTIC WET AIR OXIDATION DURING PRE-TREATMENT OF HIGH-LEVEL RADIOACTIVE WASTE SLUDGE  

SciTech Connect

Savannah River Remediation, LLC (SRR) operates the Defense Waste Processing Facility for the U.S. Department of Energy at the Savannah River Site. This facility immobilizes high-level radioactive waste through vitrification following chemical pretreatment. Catalytic destruction of formate and oxalate ions to carbon dioxide has been observed during qualification testing of non-radioactive analog systems. Carbon dioxide production greatly exceeded hydrogen production, indicating the occurrence of a process other than the catalytic decomposition of formic acid. Statistical modeling was used to relate the new reaction chemistry to partial catalytic wet air oxidation of both formate and oxalate ions driven by the low concentrations of palladium, rhodium, and/or ruthenium in the waste. Variations in process conditions led to increases or decreases in the total oxidative destruction, as well as partially shifting the preferred species undergoing destruction from oxalate ion to formate ion.

Koopman, D.; Herman, C.; Pareizs, J.; Bannochie, C.; Best, D.; Bibler, N.; Fellinger, T.

2009-10-01

397

The shock-wave mechanism of spontaneous ignition of hydrogen under conditions of sudden efflux from reservoir at high pressure  

Microsoft Academic Search

Analysis is made of the conditions of spontaneous ignition of hydrogen as a result of emergence of a starting shock wave in\\u000a air before an expanding cold flow of gas. The rise of temperature behind the shock wave causes ignition of the mixture of\\u000a combustible gas with air, which forms on the contact surface. The condition for spontaneous ignition is

T. V. Bazhenova; M. V. Bragin; V. V. Golub; M. F. Ivanov

2007-01-01

398

Performance results of the high gain, Nd: glass, engineering prototype preamplifier module (PAM) for the National Ignition Facility (NIF)  

SciTech Connect

We describe recent, energetics performance results on the engineering preamplifier module (PAM) prototype located in the front end of the 1.8MJ National Ignition Facility (NIF) laser system. Three vertically mounted subsystem located in the PAM provide laser gain as well as spatial beam shaping. The first subsystem in the PAM prototype is a diode pumped, Nd:glass, linear, TEM{sub 00}, 4.5m long regenerative amplifier cavity. With a single diode pumped head, we amplify a 1nJ, mode matched, temporally shaped ({approx} 20ns) seed pulse by a factor of approximately 10{sup 7} to 20mJ. The second subsystem in the PAM is the beam shaping module, which magnifies the gaussian output beam of the regenerative amplifier to provide a 30mm x 30mm square beam that is spatially shaped in two dimensions to pre-compensate for radial gain profiles in the main amplifiers. The final subsystem in the PAM is the 4-pass amplifier which relay images the 1mJ output of the beam shaper through four gain passes in a {phi}5cm x 48cm flashlamp pumped rod amplifier, amplifying the energy to 175. The system gain of the PAM is 10{sup 10}. Each PAM provides 35 of injected energy to four separate main amplifier chains which in turn delivers 1.8MJ in 192 frequency converted laser beams to the target for a broad range of laser fusion experiments.

Braucht, J; Browning, D; Crane, J K; Crawford, J; Deadrick, F J; Hawkins, S; Jones, B; Martinez, M D; Moran, B; Penko, F; Skulina, K M; Tilley, R

1999-02-09

399

Digestible Lysine Requirement of Gilts with High Genetic Potential for Lean Gain, in Relation to the Level of Energy Intake1  

Microsoft Academic Search

One hundred gilts were used to determine the optimal ratio between ileal digestible lysine and digestible energy in the diet, and the effect of energy intake level on this optimal ratio for gilts with high genetic potential for lean gain, between 20 and 45 kg BW. In a 2 x 15 factorial arrangement the pigs were fed either 2.5 or

P. Bikker; M. W. A. Verstegen; R. G. Campbell; B. Kemp

2010-01-01

400

Physics Based Analysis of Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) for Radio Frequency (RF) Power and Gain Optimization.  

National Technical Information Service (NTIS)

The power and gain characteristics of a power radio-frequency (RF) gallium nitride (GaN) high electron mobility transistor (HEMT) were investigated by using drift-diffusion model simulations that were self consistently solved with the current-voltage (I-V...

J. X. Qiu P. B. Shah

2011-01-01

401

Changes in growth, appetite, food conversion efficiency and body composition in mice selected for high post-weaning weight gain on restricted feeding  

Microsoft Academic Search

This study aimed to test the hypothesis that if animals were fed the same amount over the same time period, selection of the fastest growers would result in a change in the partitioning of metabolisable energy toward more protein and less fat deposition. Two mouse lines (S1 and S2) were selected for high 5 to 9 week weight gain corrected

C. P. McPhee; P. C. Trappett; A. R. Neill; F. Duncalfe

1980-01-01

402

Intraoperative versus postoperative electrochemotherapy in high grade soft tissue sarcomas: a preliminary study in a spontaneous feline model.  

PubMed

Feline soft tissue sarcomas are spontaneous, rapidly growing, and aggressive neoplasms that mimic their human counterpart. The purpose of this study was to evaluate the feasibility and efficacy of electrochemotherapy (ECT) in an adjuvant fashion for the treatment of feline sarcomas, and the possibility of repeated treatments in the case of recurrence. Cats with fibrosarcoma (FSA) were assigned to receive surgery or surgery plus ECT. Feline patients recruited in the ECT study were enrolled in a microscopic arm (39 patients) or a macroscopic arm (19 patients) on the basis of their tumor status (absence or presence of gross disease). Patients received local injection of bleomycin followed by bursts of eight biphasic pulses at a voltage of 1,300 V/cm for postoperative and of 800 V/cm for intraoperative treatments. The median time to recurrence was 4 months for cats treated with surgery alone, 19 months for the postoperative cohort, and 12 months for the intraoperative group. Moreover, ten patients with recurring neoplasms were retreated and experienced responses lasting 6 to 28+ months. Side effects were minimal. Of interest, the metastatic rate (1.7%) in our patients was negligible: only one cat had distant spread. The results suggest that ECT is a well tolerated and potentially useful addition to surgery in controlling high-grade sarcomas. On the basis of these results, additional evaluations are warranted in pets and in humans. PMID:16807731

Spugnini, Enrico P; Baldi, Alfonso; Vincenzi, Bruno; Bongiorni, Franco; Bellelli, Corrado; Citro, Gennaro; Porrello, Alessandro

2006-06-29

403

Fast Ionic Diffusion-Enabled Nanoflake Electrode by Spontaneous Electrochemical Pre-Intercalation for High-Performance Supercapacitor  

PubMed Central

Layered intercalation compounds NaxMnO2 (x = 0.7 and 0.91) nanoflakes have been prepared directly through wet electrochemical process with Na+ ions intercalated into MnO2 interlayers spontaneously. The as-prepared NaxMnO2 nanoflake based supercapacitors exhibit faster ionic diffusion with enhanced redox peaks, tenfold-higher energy densities up to 110?Wh·kg?1 and higher capacitances over 1000?F·g?1 in aqueous sodium system compared with traditional MnO2 supercapacitors. Due to the free-standing electrode structure and suitable crystal structure, NaxMnO2 nanoflake electrodes also maintain outstanding electrochemical stability with capacitance retention up to 99.9% after 1000 cycles. Besides, pre-intercalation effect is further studied to explain this enhanced electrochemical performance. This study indicates that the suitable pre-intercalation is effective to improve the diffusion of electrolyte cations and other electrochemical performance for layered oxides, and suggests that the as-obtained nanoflakes are promising materials to achieve the hybridization of both high energy and power density for advanced supercapacitors.

Mai, Liqiang; Li, Han; Zhao, Yunlong; Xu, Lin; Xu, Xu; Luo, Yanzhu; Zhang, Zhengfei; Ke, Wang; Niu, Chaojiang; Zhang, Qingjie

2013-01-01

404

Fast Ionic Diffusion-Enabled Nanoflake Electrode by Spontaneous Electrochemical Pre-Intercalation for High-Performance Supercapacitor  

NASA Astrophysics Data System (ADS)

Layered intercalation compounds NaxMnO2 (x = 0.7 and 0.91) nanoflakes have been prepared directly through wet electrochemical process with Na+ ions intercalated into MnO2 interlayers spontaneously. The as-prepared NaxMnO2 nanoflake based supercapacitors exhibit faster ionic diffusion with enhanced redox peaks, tenfold-higher energy densities up to 110 Wh.kg-1 and higher capacitances over 1000 F.g-1 in aqueous sodium system compared with traditional MnO2 supercapacitors. Due to the free-standing electrode structure and suitable crystal structure, NaxMnO2 nanoflake electrodes also maintain outstanding electrochemical stability with capacitance retention up to 99.9% after 1000 cycles. Besides, pre-intercalation effect is further studied to explain this enhanced electrochemical performance. This study indicates that the suitable pre-intercalation is effective to improve the diffusion of electrolyte cations and other electrochemical performance for layered oxides, and suggests that the as-obtained nanoflakes are promising materials to achieve the hybridization of both high energy and power density for advanced supercapacitors.

Mai, Liqiang; Li, Han; Zhao, Yunlong; Xu, Lin; Xu, Xu; Luo, Yanzhu; Zhang, Zhengfei; Ke, Wang; Niu, Chaojiang; Zhang, Qingjie

2013-04-01

405

Soluble epoxide hydrolase in the generation and maintenance of high blood pressure in spontaneously hypertensive rats.  

PubMed

We hypothesized that perinatal inhibition of soluble epoxide hydrolase (SEH), which metabolizes epoxyeicosatrienoic acids in the arachidonic acid (AA) cascade, with an orally active SEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), would persistently reduce blood pressure (BP) in adult SHR despite discontinuation of AUDA at 4 wk of age. Renal cytoplasmic epoxide hydrolase-2 (Ephx2) gene expression was enhanced in SHR vs. WKY from 2 days to 24 wk. Effects of perinatal treatment with AUDA, supplied to SHR dams until 4 wk after birth, on BP in female and male offspring and renal oxylipin metabolome in female offspring were observed and contrasted to female SHR for direct effects of AUDA (8-12 wk). Briefly, inhibition of SEH was effective in persistently reducing BP in female SHR when applied during the perinatal phase. This was accompanied by marked increases in major renal AA epoxides and decreases in renal lipoxygenase products of AA. Early inhibition of SEH induced a delayed increase in renal 5-HETE at 24 wk, in contrast to a decrease at 2 wk. Inhibition of SEH in female SHR from 8 to 12 wk did not reduce BP but caused profound decreases in renal 15(S)-HETrE, LTB4, TBX2, 5-HETE, and 20-HETE and increases in TriHOMEs. In male SHR, BP reduction after perinatal AUDA was transient. Thus, Ephx2 transcription and SEH activity in early life may initiate mechanisms that eventually contribute to high BP in adult female SHR. However, programmed BP-lowering effects of perinatal SEH inhibition in female SHR cannot be simply explained by persistent reduction in renal SEH activity but rather by more complex and temporally dynamic interactions between the renal SEH, lipoxygenase, and cyclooxygenase pathways. PMID:21266668

Koeners, Maarten P; Wesseling, Sebastiaan; Ulu, Arzu; Sepúlveda, Rocío López; Morisseau, Christophe; Braam, Branko; Hammock, Bruce D; Joles, Jaap A

2011-01-25

406

V-Band Flip-Chip Assembled Gain Block Using In0.6Ga0.4As Metamorphic High-Electron-Mobility Transistor Technology  

Microsoft Academic Search

This study fabricated a 150 nm In0.6Ga0.4As metamorphic high-electron-mobility transistor (mHEMT) device with flip-chip packaging. The packaged device exhibited favorable DC characteristics with IDS = 350 mA\\/mm and a transconductance of 600 mS\\/mm at VDS = 0.5 V. A maximum available gain (MAG) of 6.5 dB at 60 GHz was achieved with 10 mW DC power consumption. A two-stage gain

Che-Yang Chiang; Heng-Tung Hsu; Chin-Te Wang; Chien-I Kuo; Heng-Shou Hsu; Edward Yi Chang

2011-01-01

407

Merged beam laser design for reduction of gain-saturation and two-photon absorption in high power single mode semiconductor lasers.  

PubMed

In this paper we report a method to overcome the limitations of gain-saturation and two-photon absorption faced by developers of high power single mode InP-based lasers and semiconductor optical amplifiers (SOA) including those based on wide-waveguide or slab-coupled optical waveguide laser (SCOWL) technology. The method is based on Y-coupling design of the laser cavity. The reduction in gain-saturation and two-photon absorption in the merged beam laser structures (MBL) are obtained by reducing the intensity of electromagnetic field in the laser cavity. Standard ridge-waveguide lasers and MBLs were fabricated, tested and compared. Despite a slightly higher threshold current, the reduced gain-saturation in MBLs results in higher output power. The MBLs also produced a single spatial mode, as well as a strongly dominating single spectral mode which is the inherent feature of MBL-type cavity. PMID:23571918

Lysevych, M; Tan, H H; Karouta, F; Fu, L; Jagadish, C

2013-04-01

408

Spontaneous pneumothorax management.  

PubMed

Guidelines for the management of spontaneous pneumothorax were published by the British Thoracic Society (BTS) in 2003. The aim of our study was to assess compliance with the BTS guidelines. A retrospective review was performed on all spontaneous pneumothoraces admitted to our hospital between June 2006 and December 2007. There were 29 pneumothoraces during the study period, 20 of which were primary spontaneous pneumothoraces (PSPs). All 15 (100%) large PSPs had an intercostal drain (ICD) inserted with a mean calibre of 20Fr, however only 1 of the 15 (6.7%) had a prior attempt at aspiration. High flow oxygen was used in 3/20 (15%) PSPs and 1/9 (11%) secondary spontaneous pneumothoraces (SSPs). 5/6 (83%) of large SSPs had ICDs placed with a mean calibre of 23.3Fr. Compliance with BTS guidelines was suboptimal. In particular, simple aspiration was underutilised with an over-reliance on unnecessary tube thoracostomy. Moreover, the calibre of intercostal drains used was in excess of BTS recommendations. This study highlights the need to formally adopt BTS guidelines, thereby establishing a more standardised practice which should improve management of spontaneous pneumothoraces. PMID:21186751

Pallin, M; Open, M; Moloney, E; Lane, S J

2010-10-01

409

Analysis of gain difference between forward- and backward-pumped erbium-doped fiber amplifiers in the saturation regime  

Microsoft Academic Search

In saturated erbium-doped fiber amplifiers (EDFAs), signal gain and power conversion efficiency are known to be greater in the backward pumping configuration. This study shows that the difference between pumping schemes is primarily an effect of amplified spontaneous emission. It is concluded that the highest conversion efficiency achievable in highly saturated EDFAs is predicted with fair accuracy by ASE noise-free

E. Desurvire; J. M. Wiesenfeld; D. S. Chemla; G. Raybon; G. Sucha; M. Wegener; G. Eisenstein; C. A. Bums; A. G. Dentai; U. Koren; B. I. Miller; H. Temkin; R. A. Logan; T. Tanbun-Ek; A. H. Gnauck; C. R. Giles; L. J. Cimini; J. Stone; L. W. Stulz

1992-01-01

410

Monte Carlo simulation of gain, noise, and speed of low-noise and high-speed avalanche photodiodes  

Microsoft Academic Search

A Monte Carlo simulation model is developed. The low-noise behavior of AlGaAs\\/GaAs avalanche photodiodes (APDs) is successfully simulated and is explained as spatial localization of impact ionization events. The noise is sensitive to initial carrier energy and we point out that energetic and hot electrons should be distinguished. This model also successfully explains the measured exponential gain curve and \\

Feng Ma

2003-01-01

411

Based simulation of high gain and low breakdown voltage InGaAs\\/InP avalanche photodiode  

Microsoft Academic Search

The InGaAs\\/InP avalanche photodiode (APD) of thin heterostructure charge layer has studied. Apsys software is used for simulation. For reducing the dark current and achieving higher avalanche gain, a 30 nm InP charge layer and 100 nm InGaAsP grade charge layer used between 400 nm multiplication and absorption layers. Simulation results demonstrated that the low dark current properties and low

W. Lei; F. M. Guo; W. Lu; D. Y. Xiong; Z. Q. Zhu; J. H. Chu

2008-01-01

412

Ultrabroad-band Raman amplifiers pumped and gain-equalized by wavelength-division-multiplexed high-power laser diodes  

Microsoft Academic Search

This paper reviews recent progress in broad-band Raman amplifiers for wavelength-division-multiplexed (WDM) applications. After the fundamentals of Raman amplifiers are discussed in contrast to erbium-doped fiber amplifiers, a new technique called “WDM pumping” is introduced to obtain ultrabroad and flat gain in Raman amplifiers only using WDM diode pumps. The design issues of this technique are then developed to realize

Shu Namiki; Yoshihiro Emori

2001-01-01

413

Comparative genomic hybridization in chronic B-cell leukemias shows a high incidence of chromosomal gains and losses.  

PubMed

In chronic B-cell leukemias, fluorescence in situ hybridization has greatly improved the ability to detect certain chromosomal aberrations, as cells in all phases of the cell cycle are analyzed. To obtain a comprehensive view of chromosomal gains and losses, we applied the recently developed technique of comparative genomic hybridization (CGH) to 28 patients with chronic B-cell leukemias. CGH results were compared with those obtained by chromosome banding analysis and interphase cytogenetics. In 19 of the 28 cases, chromosomal imbalances were detected, including amplified DNA sequences in three instances. The most common aberrations included gains of chromosomal material on 8q and 12 as well as losses of 6q, 11q, 13q, and 17p. In 13 cases, CGH revealed chromosomal gains and losses not detected by banding analysis. In 8 of these 13 cases, discrepancies were further investigated using other methods, and in all instances, the CGH findings were confirmed. A limitation of detecting small deleted regions by CGH was found in one example of 18p. In conclusion, our data show that the results of banding analysis in chronic B-cell leukemias often do not reflect the chromosomal changes in the predominant cell clone. This may be one explanation for the as yet poor correlation between cytogenetic findings and clinical course in this group of neoplasms. PMID:7780145

Bentz, M; Huck, K; du Manoir, S; Joos, S; Werner, C A; Fischer, K; Döhner, H; Lichter, P

1995-06-15

414

Compositional effect of WO3, MoO3, and P2O5 on Raman spectroscopy of tellurite glass for broadband and high gain Raman amplifier  

NASA Astrophysics Data System (ADS)

In order to obtain broadband and high Raman gain coefficient in the tellurite glass, a detailed study of the effects of WO3, MoO3, and P2O5 in TeO2-ZnO-Na2O-Nb2O5 (TZNN) glass system on the thermal stabilities and Raman spectroscopic was performed. It was found that both WO3 and MoO3 improved the glass thermal stability and enhanced the bandwidth significantly. Higher Raman gain coefficients and broader bandwidth were realized in the MoO3 modified glasses than those of WO3 added glass. The tellurite glass containing 15 mol. % MoO3 exhibits the bandwidth 1.7 times larger than the silica glass and the Raman gain coefficient is as high as 38 times that of the silica glass. Moreover, with the addition of P2O5 in TeO2-ZnO-Na2O-Nb2O5-WO3 (TZNNW) and TeO2-ZnO-Na2O-Nb2O5-MoO3 (TZNNM) glass systems, the thermal stabilities can further be improved. On the other hand, the Raman bandwidth can further be broadened, especially in the TZNNMP glass system. The tellurite glass containing 15 mol. % MoO3 and 15 mol. % P2O5 shows the bandwidth 1.9 times larger than the silica glass and maintains high Raman gain coefficient which is as high as 37 times that of the silica glass, indicating this glass is a promising candidate as new gain media for broadband Raman fiber amplifier.

Yuan, J.; Yang, Q.; Chen, D. D.; Qian, Q.; Shen, S. X.; Zhang, Q. Y.; Jiang, Z. H.

2012-05-01

415

Modeling and mitigation of dynamic load beat-frequency oscillation in multiphase voltage regulators with high-gain peak current control scheme  

Microsoft Academic Search

High-frequency dynamic load may cause phase current oscillation in multiphase interleaved voltage regulators. A model is presented in this paper to investigate this phenomenon in the recently reported high-gain peak current control (HGPCC) voltage regulators. Based on the analysis, it is concluded that HGPCC scheme suffers from beat-frequency oscillation problems, similarly to conventional peak current control scheme. A modified HGPCC

Chen-Hua Chiu; Dan Chen; Ching-Jan Chen; Wei-Hsu Chang

2010-01-01

416

Spontaneous fission  

SciTech Connect

The spontaneous fission (SF) of the heaviest actinides and the transactinides is of particular interest because of the dramatic changes in properties observed in the region of the heavy fermion isotopes and for still heavier elements. The existing experimental information on SF properties including half-life systematics, fragment kinetic-energy and mass-yield distributions, prompt neutron emission, and gamma emission will be reviewed. Possibility for extending studies of SF properties to other regions are considered and the potential for obtaining additional information about low-energy fission properties is discussed.

Hoffman, D.C. [Lawrence Berkeley Lab., CA (United States)

1993-09-01

417

Spontaneous fission  

NASA Astrophysics Data System (ADS)

The spontaneous fission (SF) of the heaviest actinides and the transactinides is of particular interest, because of the dramatic changes in properties observed in the region of the heavy fermium isotopes and for still heavier elements. The existing experimental information on SF properties, including half-life systematics, fragment kinetic energy and mass yield distributions, prompt neutron emission and gamma emission, will be reviewed. Possibilities for extending studies of SF properties to other regions are considered, and the potential for obtaining additional information about low-energy fission properties is discussed.

Hoffman, Darleane C.

1994-10-01

418

Very high-gain and low-excess noise near-infrared single-photon avalanche detector: an NIR solid state photomultiplier  

NASA Astrophysics Data System (ADS)

A new family of photodetectors with a Discrete Amplification (DA) mechanism allows the realization of very high gain and low excess noise factor in the visible and near infrared spectral regions and offers an alternative to conventional photomultiplier tubes and Geiger mode avalanche photodetectors. These photodetectors can operate in linear detection mode with gain-bandwidth product in excess of 4X1014 and in photon counting mode with count rates up to 108 counts/sec. Potential benefits of this technology over conventional avalanche photodetectors include ultra low excess noise factor, very high gain, and lower reset time (<< 1 ?s). In the photon counting mode, the devices can be operated in the non-gated mode under a constant dc bias. Because of its unique characteristics of self-quenching and self-recovery, no external quenching circuit is needed. We present the discrete amplification design approach used for the development of a solid state photomultiplier in the near infrared wavelength region. The demonstrated device performance far exceeds any available solid state photodetectors in the near infrared wavelength range. The measured devices have the following performance characteristics: gain > 2X105, excess noise factor < 1.05, rise time < 350ps, fall time < 500ps, dark current < 2X106 cps, operating voltage < 60V. These devices are ideal for researchers in the field of deep space optical communication, spectroscopy, industrial and scientific instrumentation, Ladar/Lidar, quantum cryptography, night vision and other military, defence and aerospace applications.

Linga, Krishna; Yevtukhov, Yuriy; Liang, Bing

2009-05-01

419

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

NASA Astrophysics Data System (ADS)

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

Kojima, Jun; Nguyen, Quang-Viet

2004-03-01

420

Effects of high-sucrose feeding on insulin resistance and hemodynamic responses to insulin in spontaneously hypertensive rats.  

PubMed

This study was designed to investigate the effects of a sucrose diet on vascular and metabolic actions of insulin in spontaneously hypertensive rats (SHR). Male SHR were randomized to receive a sucrose or regular chow diet for 4 wk. Age-matched, chow-fed Wistar-Kyoto (WKY) rats were used as normotensive control. In a first series of experiments, the three groups of rats had pulsed Doppler flow probes and intravascular catheters implanted to determine blood pressure, heart rate, and blood flows. Insulin sensitivity was assessed during a euglycemic hyperinsulinemic clamp performed in conscious rats. In a second series of experiments, new groups of rats were used to examine glucose transport activity in isolated muscles and to determine endothelial nitric oxide synthase (eNOS) protein expression in muscles and endothelin content in vascular tissues. Sucrose feeding was shown to markedly enhance the pressor response to insulin and its hindquarter vasoconstrictor effect when compared with chow-fed SHR. A reduction in eNOS protein content in muscle, but no change in vascular endothelin-1 protein, was noted in sucrose-fed SHR when compared with WKY rats, but these changes were not different from those noted in chow-fed SHR. Similar reductions in insulin-stimulated glucose transport were observed in soleus muscles from both groups of SHR when compared with WKY rats. In extensor digitorum longus muscles, a significant reduction in insulin-stimulated glucose transport was only seen in sucrose-fed rats when compared with the other two groups. Environmental factors, that is, high intake of simple sugars, could possibly potentiate the genetic predisposition in SHR to endothelial dysfunction and insulin resistance. PMID:16443676

Mélançon, Sébastien; Bachelard, Hélène; Badeau, Mylène; Bourgoin, Frédéric; Pitre, Maryse; Larivière, Richard; Nadeau, André

2006-01-27

421

A power efficient bandwidth regulation technique for a low-noise high-gain RF wideband amplifier  

NASA Astrophysics Data System (ADS)

In this paper, a single-stage deep sub-micron wideband amplifier (LNA) using a reactive resonance tank and passive port-matching techniques is demonstrated operating in the microwave frequency range (K band). A novel power-efficient bandwidth (BW) regulation technique is proposed by incorporating a small impedance in the resonance tank of the amplifier configuration. It manifests a forward gain in the range of 5.9-10.7 dB covering a message bandwidth of 10.6-6.3 GHz. With regulation, input-output reflection parameters ( S 11, S 22) and noise figure can be manipulated by -12.7 dB, -22.7 dB and 0.36 dB, respectively. Symmetric regulation is achieved for bandwidth and small signal gain with respect to moderate tank impedance (36.5% and -26.8%, respectively) but the effect on noise contribution remains relatively low (increase of 7% from a base value of 2.39 dB). The regulated architecture, when analyzed with 90 nm silicon CMOS process, supports low power (9.1 mW) on-chip communication. The circuit is tested with a number of combinations for tank (drain) impedance to verify the efficiency of the proposed technique and achieves better figures of merit when compared with published literature.

Roy, Apratim; Rashid, S. M. S.

2012-09-01

422

Targeting Binge Eating for the Prevention of Excessive Weight Gain: Interpersonal Psychotherapy for Adolescents at High-Risk for Adult Obesity  

PubMed Central

The most prevalent disordered eating pattern described in overweight youth is loss of control (LOC) eating, during which individuals experience an inability to control the type or amount of food they consume. LOC eating is associated cross-sectionally with greater adiposity in children and adolescents, and appears to predispose youth to gain weight or body fat above that expected during normal growth, thus likely contributing to obesity in susceptible individuals. No prior studies have examined whether LOC eating can be decreased by interventions in children or adolescents without full-syndrome eating disorders, or whether programs reducing LOC eating prevent inappropriate weight gain attributable to LOC eating. Interpersonal psychotherapy, a form of therapy that was designed to treat depression and has been adapted for the treatment of eating disorders, has demonstrated efficacy in reducing binge eating episodes and inducing weight stabilization among adults diagnosed with binge eating disorder. In this paper, we propose a theoretical model of excessive weight gain in adolescents at high-risk for adult obesity who engage in LOC eating and associated overeating patterns. A rationale is provided for interpersonal psychotherapy as an intervention to slow the trajectory of weight gain in at-risk youth, with the aim of preventing or ameliorating obesity in adulthood.

Tanofsky-Kraff, Marian; Wilfley, Denise E.; Young, Jami F.; Mufson, Laura; Yanovski, Susan Z.; Glasofer, Deborah R.; Salaita, Christine G.

2007-01-01

423

Time resolved gain/loss studies under low and high power loading for the XeF C-A transition  

SciTech Connect

The behavior of gain versus peak power deposition and the gain-length product versus total energy deposited are measured for devices with power deposition levels from 1 to 13 MW/cm{sup 3} under a variety of gas mixtures. The temporal correlation between the power deposition and gain shows that both the fluorescence and the gain occur after the power deposition has concluded for excitation pulses in the range of 10--30 ns. We find that both B-X and C-A fluorescence takes place in the afterglow and their temporal shapes are similar. This indicates that the C and B states are tightly coupled. This tight coupling has two detrimental consequences for C-state lasing. First is that the population of the B and C states are approximately equal rather than 90% in the C state believed to exist for short pulse electron beam excitation. We believe this close coupling is due to the presence of electric fields in the afterglow which keep the electron temperature relatively hot. The relative populations of the B and C states are determined by a Boltzman distribution governed by the electron temperature and their relative energy separation. Second is that with the C state lifetime approximately the same as the B state lifetime the C-A saturation intensity is very high and efficient energy extraction is substantially more difficult. 5 refs., 10 figs.

Sze, R.C. (Los Alamos National Lab., NM (USA)); Sentis, M. (Institut de Mecanique des Fluides, 13 - Marseille (France)); Vannini, M. (Consiglio Nazionale delle Ricerche, Florence (Italy). Ist. di Elettronica Quantistica)

1990-01-01

424

Topiramate reduces abnormally high extracellular levels of glutamate and aspartate in the hippocampus of spontaneously epileptic rats (SER)  

Microsoft Academic Search

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

Tomoyuki Kanda; Masako Kurokawa; Sachiko Tamura; Joji Nakamura; Akio Ishii; Yoshihisa Kuwana; Tadao Serikawa; Junzo Yamada; Kumatoshi Ishihara; Masashi Sasa

1996-01-01

425

High D(+)-Fructose Diet Adversely Affects Testicular Weight Gain in Weaning Rats-Protection by Moderate D(+)-Glucose Diet  

PubMed Central

The use of high D(+)-fructose corn syrup has increased over the past several decades in the developed countries, while overweight and obesity rates and the related diseases have risen dramatically. However, we found that feeding a high D(+)-fructose diet (80% D(+)-fructose as part of the diet) to weaning rats for 21 days led to reduced food intake (50% less, P < 0.0001) and thus delayed the weight gains in the body (40% less, P < 0.0001) and testes (40% less, P < 0.0001) compared to the no D(+)-fructose diet. We also challenged a minimum requirement of dietary D(+)-glucose for preventing the adverse effects of D(+)-fructose, such as lower food intake and reduction of body weight and testicular weight; the minimum requirement of D(+)-glucose was ?23% of the diet. This glucose amount may be the minimum requirement of exogenous glucose for reducing weight gain.

Shibata, Katsumi; Fukuwatari, Tsutomu

2013-01-01

426

High d(+)-fructose diet adversely affects testicular weight gain in weaning rats?protection by moderate d(+)-glucose diet.  

PubMed

The use of high D(+)-fructose corn syrup has increased over the past several decades in the developed countries, while overweight and obesity rates and the related diseases have risen dramatically. However, we found that feeding a high D(+)-fructose diet (80% D(+)-fructose as part of the diet) to weaning rats for 21 days led to reduced food intake (50% less, P < 0.0001) and thus delayed the weight gains in the body (40% less, P < 0.0001) and testes (40% less, P < 0.0001) compared to the no D(+)-fructose diet. We also challenged a minimum requirement of dietary D(+)-glucose for preventing the adverse effects of D(+)-fructose, such as lower food intake and reduction of body weight and testicular weight; the minimum requirement of D(+)-glucose was ?23% of the diet. This glucose amount may be the minimum requirement of exogenous glucose for reducing weight gain. PMID:23935370

Shibata, Katsumi; Fukuwatari, Tsutomu

2013-07-15

427

Ultra-Wideband Ultra-Low-DC-Power High Gain Differential-Input Low Noise Amplifier MMIC Using InAs\\/AlSb HEMT  

Microsoft Academic Search

This paper reports an ultra-wideband ultra-low-DC power high gain MMIC low noise amplifier (LNA) with differential RF input using 0.1-mum gate length InAs\\/AlSb metamorphic HEMTs, fabricated and characterized on a GaAs substrate. For testing purpose and for generating a differential RF input, a 3-12 GHz wideband on-chip MMIC balun is connected to the differential input. Even with the loss of

Bob Y. Ma; Joshua Bergman; Peter S. Chen; Jonathan B. Hacker; Gerard Sullivan; Bobby Brar

2007-01-01

428

MATERNAL ALCOHOL CONSUMPTION AND SPONTANEOUS ABORTION  

Microsoft Academic Search

This review examines the relationship between maternal alcohol consumption during pregnancy and spontaneous abortions. Although very high spontaneous abortion rates have been reported for alcoholic women, it is still uncertain if this is due to the direct effects of alcohol or the indirect effects of alcoholism-re lated disorders such as cirrhosis. The higher rates of spontaneous abortion among alcoholics may

ERNEST L. ABEL

429

Photoluminescence enhancement and high gain amplification of ErxY2-xSiO5 waveguide  

NASA Astrophysics Data System (ADS)

ErxY2-xSiO5 (x=0-2) films have been fabricated on Si(100) substrates by the sol-gel method. Enhanced Er3+ photoluminescence of around 30 times for the ErxY2-xSiO5 (x=0.1) film was observed compared with pure Er2SiO5 film at the wavelength pump of 654 nm. Reduced upconversion effect and decreased nonradiative transient rate are two main reasons for the enhanced Er3+ luminescence in the new film of ErxY2-xSiO5. Above 10 dB optical gain can be achieved at the 1 mm length ErxY2-xSiO5 (x=0.1) waveguide under 30 mW pumping power, indicating it is sought candidate material for compact waveguide amplifiers and emitters in silicon photonics integration.

Wang, X. J.; Yuan, G.; Isshiki, H.; Kimura, T.; Zhou, Z.

2010-07-01

430

Impact of Korean pine nut oil on weight gain and immune responses in high-fat diet-induced obese mice  

PubMed Central

Korean pine nut oil (PNO) has been reported to have favorable effects on lipid metabolism and appetite control. We investigated whether PNO consumption could influence weight gain, and whether the PNO-induced effect would result in an improvement of immune function in high-fat diet (HFD)-induced obese mice. C57BL/6 mice were fed control diets with 10% energy fat from either PNO or soybean oil (SBO), or HFDs with 45% energy fat from 10% PNO or SBO and 35% lard, 20% PNO or SBO and 25% lard, or 30% PNO or SBO and 15% lard for 12 weeks. The proliferative responses of splenocytes upon stimulation with concanavalin A (Con A) or lipopolysaccharide (LPS), Con A-stimulated production of interleukin (IL)-2 and interferon (IFN)-?, and LPS-stimulated production of IL-6, IL-1?, and prostaglandin E2 (PGE2) by splenocytes were determined. Consumption of HFDs containing PNO resulted in significantly less weight gain (17% less, P < 0.001), and lower weight gain was mainly due to less white adipose tissue (18% less, P = 0.001). The reduction in weight gain did not result in the overall enhancement in splenocyte proliferation. Overall, PNO consumption resulted in a higher production of IL-1? (P = 0.04). Replacement of SBO with PNO had no effect on the production of IL-2, IFN-?, IL-6, or PGE2 in mice fed with either the control diets or HFDs. In conclusion, consumption of PNO reduced weight gain in mice fed with HFD, but this effect did not result in the overall improvement in immune responses.

Park, Soyoung; Lim, Yeseo; Shin, Sunhye

2013-01-01

431

Impact of Korean pine nut oil on weight gain and immune responses in high-fat diet-induced obese mice.  

PubMed

Korean pine nut oil (PNO) has been reported to have favorable effects on lipid metabolism and appetite control. We investigated whether PNO consumption could influence weight gain, and whether the PNO-induced effect would result in an improvement of immune function in high-fat diet (HFD)-induced obese mice. C57BL/6 mice were fed control diets with 10% energy fat from either PNO or soybean oil (SBO), or HFDs with 45% energy fat from 10% PNO or SBO and 35% lard, 20% PNO or SBO and 25% lard, or 30% PNO or SBO and 15% lard for 12 weeks. The proliferative responses of splenocytes upon stimulation with concanavalin A (Con A) or lipopolysaccharide (LPS), Con A-stimulated production of interleukin (IL)-2 and interferon (IFN)-?, and LPS-stimulated production of IL-6, IL-1?, and prostaglandin E2 (PGE2) by splenocytes were determined. Consumption of HFDs containing PNO resulted in significantly less weight gain (17% less, P < 0.001), and lower weight gain was mainly due to less white adipose tissue (18% less, P = 0.001). The reduction in weight gain did not result in the overall enhancement in splenocyte proliferation. Overall, PNO consumption resulted in a higher production of IL-1? (P = 0.04). Replacement of SBO with PNO had no effect on the production of IL-2, IFN-?, IL-6, or PGE2 in mice fed with either the control diets or HFDs. In conclusion, consumption of PNO reduced weight gain in mice fed with HFD, but this effect did not result in the overall improvement in immune responses. PMID:24133613

Park, Soyoung; Lim, Yeseo; Shin, Sunhye; Han, Sung Nim

2013-10-01

432

A gain-coefficient switched Alexandrite laser  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

433

Early Metabolic Adaptation in C57BL/6 Mice Resistant to High Fat Diet Induced Weight Gain Involves an Activation of Mitochondrial Oxidative Pathways.  

PubMed

We investigated the short-term (7 days) and long-term (60 days) metabolic effect of high fat diet induced obesity (DIO) and weight gain in isogenic C57BL/6 mice and examined the specific metabolic differentiation between mice that were either strong-responders (SR), or non-responders (NR) to weight gain. Mice (n = 80) were fed a standard chow diet for 7 days prior to randomization into a high-fat (HF) (n = 56) or a low-fat (LF) (n = 24) diet group. The (1)H NMR urinary metabolic profiles of LF and HF mice were recorded 7 and 60 days after the diet switch. On the basis of the body weight gain (BWG) distribution of HF group, we identified NR mice (n = 10) and SR mice (n = 14) to DIO. Compared with LF, HF feeding increased urinary excretion of glycine conjugates of ?-oxidation intermediate (hexanoylglycine), branched chain amino acid (BCAA) catabolism intermediates (isovalerylglycine, ?-keto-?-methylvalerate and ?-ketoisovalerate) and end-products of nicotinamide adenine dinucleotide (NAD) metabolism (N1-methyl-2-pyridone-5-carboxamide, N1-methyl-4-pyridone-3-carboxamide) suggesting up-regulation of mitochondrial oxidative pathways. In the HF group, NR mice excreted relatively more hexanoylglycine, isovalerylglycine, and fewer tricarboxylic acid (TCA) cycle intermediate (succinate) in comparison to SR mice. Thus, subtle regulation of ketogenic pathways in DIO may alleviate the saturation of the TCA cycle and mitochondrial oxidative metabolism. PMID:23473242

Boulangé, Claire L; Claus, Sandrine P; Chou, Chieh J; Collino, Sebastiano; Montoliu, Ivan; Kochhar, Sunil; Holmes, Elaine; Rezzi, Serge; Nicholson, Jeremy K; Dumas, Marc E; Martin, François-Pierre J

2013-03-01

434

Diffusion tensor imaging using a high-temperature superconducting resonator in a 3 T magnetic resonance imaging for a spontaneous rat brain tumor  

NASA Astrophysics Data System (ADS)

This study investigates the peri-tumor signal abnormalities of a spontaneous brain tumor in a rat by using a 4 cm high-temperature superconducting (HTS) surface resonator. Fractional anisotropy (FA) values derived from diffusion tensor imaging reflect the interstitial characteristic of the peri-lesional tissues of brain tumors. Low FA indicates interstitial tumor infiltration and tissue injury, while high FA indicates better tissue integrity. Better delineation of tissue contents obtained by the HTS surface resonator at 77 K may facilitate therapeutic strategy and improve clinical outcomes.

Lin, In-Tsang; Yang, Hong-Chang; Chen, Jyh-Horng

2013-02-01

435

High spin studies of neutron-rich nuclei produced in the spontaneous fission process of californium-252  

NASA Astrophysics Data System (ADS)

From an experiment with GAMMMASPHERE and a 252Cf spontaneous fission source, high spin studies of several neutron-rich nuclei have been carried out. In the mass region A ~ 150, a new negative-parity band in 154Nd and new negative-parity levels in 152Nd were identified and the yrast bands were extended to 18+ in 154Nd and 20+ 152Nd in a triple gamma coincidence study. These new negative-parity bands are consistent with octupole vibrational mode rather than the stable octupole deformation seen in Ba and Ce nuclei. There is a constant difference as a function of spin between the J1 values for the negative-parity band in 152Nd and J1 for the similar negative-parity band in 154Nd, however, their J2 values are essentially identical above the 4 + state. These bands indicate a new kind of identical bands associated with an octupole vibrational mode. In mass region A ~ 110, we have observed new bands in 113,115,117,118 Pd up to moderately high spin. The newly identified negative-parity yrast band energy level systematics built on the / isomeric states fit smoothly with the known systematic for other Pd isotopes, and show a minimum excitation energy at N = 68 related to a mid-shell closure. These new negative- parity yrast bands indicate a first band crossing at ¢? ~ 0.45 MeV, nearly identical to those seen in 109,111Pd, but significantly higher than those in the positive yrast parity bands in 113,115Pd and in the even-even Pd isotopes. We have interpreted the new negative-parity yrast bands as having band crossings from the alignment of a nh/ pair, and this suggests that 113,115,117Pd maintain a prolate shape. Additionally, we have observed two new bands in 113,115 Pd, which are tentatively assigned positive parity with band crossings about 0.25 and 0.32 MeV. These lower frequencies are consistent with a nh/ pair alignment. In the neutron-rich 118Pd, the first band crossing at a frequency of ¢? ~ 0.29 MeV was observed in its yrast band. This band crossing frequency is substantially lower than the first band crossing frequency of ¢? ~ 0.45 MeV observed the yrast bands in the lighter odd mass Pd isotopes and the crossing at ¢? = 0.35 in the yrast bands in 112,114,116Pd. This lower crossing frequency is well reproduced by the quasi- neutron Routhian calculation by assuming that the neutron-pairing gap is reduced in 118Pd. The calculation show a two nh/ band crossing at ¢? ~ 0.3 in agreement with the experimental value. A reduction in neutron pairing is responsible in Cranking model for lowering the crossing frequency. This band crossing in the new yrast cascade in 118Pd as well as those in 112,114,116Pd are interpreted based on a two h/ neutron configuration. Our result indicates 118 Pd still maintains a prolate shape. It's found that the crossing frequency in 118Pd is considerably lower and weaker than for the other even Pd isotopes. In the even-even 88,90,92Kr, all yrast bands were studied and extended to 8+, 10+, 12+, respectively. Quasi-gamma bands in 90,92Kr, and possibly one in 88Kr were identified. These data provide useful information about the interplay of collective and independent particle excitations in these three nuclei. Additionally, the coexisting of vibrational motion near the ground state and rotational collective motion at intermediate spins is observed in neutron-rich 90Kr.

Zhang, Xueqian

2001-08-01

436

Supplementation of whole persimmon leaf improves lipid profiles and suppresses body weight gain in rats fed high-fat diet  

Microsoft Academic Search

The objective of this study was to investigate the hypolipidemic effects of powdered whole persimmon leaf supplement in rats fed high-fat diet. Three groups of male Sprague–Dawley rats during 6 weeks were fed different diet: normal control (NC), high-fat (HF), and high-fat supplemented with powdered whole persimmon leaf (PL; 5%, wt\\/wt) groups. Body weight and relative weight of interscapular brown

J. S. Lee; M. K. Lee; T. Y. Ha; S. H. Bok; H. M. Park; K. S. Jeong; M. N. Woo; G.-M. Do; J.-Y. Yeo; M.-S. Choi

2006-01-01

437

All-fiber dynamic gain equalizer based on a twisted long-period grating written by high-frequency CO2 laser pulses.  

PubMed

A novel dynamic gain equalizer for flattening Er-doped fiber amplifiers based on a twisted long-period fiber grating (LPFG) induced by high-frequency CO(2) laser pulses is reported for the first time to our knowledge. Experimental results show that its transverse-load sensitivity is up to 0.34 dB/(g.mm(-1)), while the twist ratio of the twisted LPFG is approximately 20 rad/m, which is 7 times higher than that of a torsion-free LPFG. In addition, it is found that the strong orientation dependence of the transverse-load sensitivity of the torsion-free LPFG reported previously has been weakened considerably. Therefore such a dynamic gain equalizer based on the unique transverse-load characteristics of the twisted LPFG provides a much larger adjustable range and makes packaging of the gain equalizer much easier. A demonstration has been carried out to flatten an Er-doped fiber amplifier to +/-0.5 dB over a 32 nm bandwidth. PMID:17228383

Zhu, T; Rao, Y J; Wang, J L

2007-01-20

438

Step-up switching-mode converter with high voltage gain using a switched-capacitor circuit  

Microsoft Academic Search

A new circuit is proposed for a steep step-up of the line voltage. It integrates a switched-capacitor (SC) circuit within a boost converter. An SC circuit can achieve any voltage ratio, allowing for a boost of the input voltage to high values. It is unregulated to allow for a very high efficiency. The boost stage has a regulation purpose. It

Oded Abutbul; Amir Gherlitz; Yefim Berkovich; Adrian Ioinovici

2003-01-01

439

Experiment on suppression of spontaneous undulator radiation at ATF  

SciTech Connect

We propose undertaking a demonstration experiment on suppressing spontaneous undulator radiation from an electron beam at BNL's Accelerator Test Facility (ATF). We describe the method, the proposed layout, and a possible schedule. There are several advantages in strongly suppressing shot noise in the electron beam, and the corresponding spontaneous radiation. The self-amplified spontaneous (SASE) emission originating from shot noise in the electron beam is the main source of noise in high-gain FEL amplifiers. It may negatively affect several HG FEL applications ranging from single- to multi-stage HGHG FELs. SASE saturation also imposes a fundamental hard limit on the gain of an FEL amplifier in a coherent electron-cooling scheme. A novel active method for suppressing shot noise in relativistic electron beams by many orders-of-magnitude was recently proposed. While theoretically such strong suppression appears feasible, the performance and applicability of this novel method must be evaluated experimentally. Several practical questions about the proposed noise suppressor, such as 3D effects and/or sensitivity to the e-beam parameters also require experimental clarification. To do this, we propose here a proof-of-principle experiment using elements of the VISA FEL at BNL's Accelerator Test Facility.

Litvinenko,V.; Yakimenko, V.

2009-08-23

440

At-Risk High School Students in the “Gaining Early Awareness and Readiness” Program (GEAR UP): Academic and Behavioral Outcomes  

Microsoft Academic Search

  The purpose of this study was to assess the effects of a GEAR UP intervention with at-risk high school students at a large urban high school in Florida. The goals of the GEAR UP program were to improve academic performance, decrease behavior-related problems, and reduce truancy and absenteeism. The study design consisted of a three-group comparison of the 447 students

Svetlana Yampolskaya; Oliver T. Massey; Paul E. Greenbaum

2006-01-01

441

Heat resistance and salt hypersensitivity in Lactococcus lactis due to spontaneous mutation of llmg_1816 (gdpP) induced by high-temperature growth.  

PubMed

During construction of several gene deletion mutants in Lactococcus lactis MG1363 which involved a high-temperature (37.5°C) incubation step, additional spontaneous mutations were observed which resulted in stable heat resistance and in some cases salt-hypersensitive phenotypes. Whole-genome sequencing of one strain which was both heat resistant and salt hypersensitive, followed by PCR and sequencing of four other mutants which shared these phenotypes, revealed independent mutations in llmg_1816 in all cases. This gene encodes a membrane-bound stress signaling protein of the GdpP family, members of which exhibit cyclic dimeric AMP (c-di-AMP)-specific phosphodiesterase activity. Mutations were predicted to lead to single amino acid substitutions or protein truncations. An independent llmg_1816 mutant (?1816), created using a suicide vector, also displayed heat resistance and salt hypersensitivity phenotypes which could be restored to wild-type levels following plasmid excision. L. lactis ?1816 also displayed improved growth in response to sublethal concentrations of penicillin G. High-temperature incubation of a wild-type industrial L. lactis strain also resulted in spontaneous mutation of llmg_1816 and heat-resistant and salt-hypersensitive phenotypes, suggesting that this is not a strain-specific phenomenon and that it is independent of a plasmid integration event. Acidification of milk by the llmg_1816-altered strain was inhibited by lower salt concentrations than the parent strain. This study demonstrates that spontaneous mutations can occur during high-temperature growth of L. lactis and that inactivation of llmg_1816 leads to temperature resistance and salt hypersensitivity. PMID:22923415

Smith, William M; Pham, Thi Huong; Lei, Lin; Dou, Junchao; Soomro, Aijaz H; Beatson, Scott A; Dykes, Gary A; Turner, Mark S

2012-08-24

442

High gain pulsed erbium-doped fiber amplifier for the nonlinear characterization of SWCNTs photodeposited on optical fibers  

NASA Astrophysics Data System (ADS)

We report the experimental setup of a high power pulsed erbium-doped fiber amplifier. An optical signal at 1550 nm emitted by a distributed feedback laser is amplified by two identical stages in reflective configuration using one fiber Bragg grating at each one of those. We demonstrated that for pulses with a frequency of 20 kHz and temporal duration of 10, 50, 100, and 500 ns, it is possible to obtain output peak powers of 41, 22, 18, and 11 W, respectively. We applied our high power amplifier in the characterization of nonlinear optical transmission of single-wall carbon nanotubes deposited on single mode optical fibers end-face by the photodeposition technique. Our results show that the high power system is ideal for carrying out studies of nonlinear effects in optical fibers as well as nonlinear characterization of nanostructured materials deposited on optical fibers.

Zaca-Morán, P.; Kuzin, E.; Torres-Turiján, J.; Ortega-Mendoza, J. G.; Chávez, F.; Pérez-Sánchez, G. F.; Gómez-Pavón, L. C.

2013-11-01

443

Gain characteristics of deep UV AlGaN quantum wells lasers  

NASA Astrophysics Data System (ADS)

The optical gain characteristics of high Al-content AlGaN quantum wells (QWs) are analyzed for deep UV lasers. The effect of crystal-field split-off hole (CH) and heavy-hole (HH) bands crossover on the gain characteristics of AlGaN QW with AlN barriers is analyzed. Attributing to the strong transition between conduction - CH bands, the TM spontaneous emission recombination rate is enhanced significantly for high Al-content AlGaN QWs. Large TM-polarized material gain is shown as achievable for high Al-content AlGaN QWs, which indicates the feasibility of TM lasing for lasers emitting at ~220-230 nm.

Zhang, Jing; Zhao, Hongping; Tansu, Nelson

2011-02-01

444

High Magnetic Shear Gain in a Liquid Sodium Stable Couette Flow Experiment: A Prelude to an alpha-Omega Dynamo  

Microsoft Academic Search

The Omega phase of the liquid sodium alpha-Omega dynamo experiment at New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field Bvarphi that is ~=8×Br, where Br is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette

Stirling A. Colgate; Howard Beckley; Jiahe Si; Joe Martinic; David Westpfahl; James Slutz; Cebastian Westrom; Brianna Klein; Paul Schendel; Cletus Scharle; Travis McKinney; Rocky Ginanni; Ian Bentley; Timothy Mickey; Regnar Ferrel; Hui Li; Vladimir Pariev; John Finn

2011-01-01

445

How Much Professional Development Is Needed to Effect Positive Gains in K-6 Student Achievement on High Stakes Science Tests?  

ERIC Educational Resources Information Center

|This paper is a report of a study that examines the relationship between teacher participation in a multi-year, K-6 professional development effort and the "high stakes" science test scores of different student groups in 33 rural mid-west school districts in the USA. The professional development program involved 1,269 elementary school teachers…

Shymansky, James A.; Wang, Tzu-Ling; Annetta, Leonard A.; Yore, Larry D.; Everett, Susan A.

2012-01-01

446

Porcine Adiponectin Receptor 1 Transgene Resists High-fat/Sucrose Diet-Induced Weight Gain, Hepatosteatosis and Insulin Resistance in Mice.  

PubMed

Adiponectin and its receptors have been demonstrated to play important roles in regulating glucose and lipid metabolism in mice. Obesity, type II diabetes and cardiovascular disease are highly correlated with down-regulated adiponectin signaling. In this study, we generated mice overexpressing the porcine Adipor1 transgene (pAdipor1) to study its beneficial effects in metabolic syndromes as expressed in diet-induced obesity, hepatosteatosis and insulin resistance. Wild-type (WT) and pAdipor1 transgenic mice were fed ad libitum with a standard chow diet (Chow) or a high-fat/sucrose diet (HFSD) for 24 weeks, beginning at 6 to 7 weeks of age. There were 12 mice per genetic/diet/sex group. When challenged with HFSD to induce obesity, the pAdipor1 transgenic mice resisted development of weight gain, hepatosteatosis and insulin resistance. These mice had lowered plasma adiponectin, triglyceride and glycerol concentrations compared to WT mice. Moreover, we found that (indicated by mRNA levels) fatty acid oxidation was enhanced in skeletal muscle and adipose tissue, and liver lipogenesis was inhibited. The pAdipor1 transgene also restored HFSD-reduced phosphoenolpyruvate carboxykinase 1 (Pck1) and glucose transporter 4 mRNA in the adipose tissues, implying that the increased Pck1 may promote glyceroneogenesis to reduce glucose intolerance and thus activate the flux of glyceride-glycerol to resist diet-induced weight gain in the adipose tissues. Taken together, we demonstrated that pAdipor1 can prevent diet-induced weight gain and insulin resistance. Our findings may provide potential therapeutic strategies for treating metabolic syndromes and obesity, such as treatment with an ADIPOR1 agonist or activation of Adipor1 downstream targets. PMID:24172199

Liu, Bing-Hsien; Lin, Yuan-Yu; Wang, Ya-Chin; Huang, Chao-Wei; Chen, Chih-Chien; Wu, Shinn-Chih; Mersmann, Harry J; Cheng, Winston T K; Ding, Shih-Torng

2013-01-01

447

Double pulse quasi-collinear high harmonic generation scheme as a tool for X-ray laser plasma gain probing  

NASA Astrophysics Data System (ADS)

We have investigated high harmonic generation in an argon gas cell driven by two femtosecond laser pulses separated by a variable delay ranging from 500 fs to 100 ps. Experiments were performed at the LASERIX IR-EUV facility using an amplified 10 Hz CPA Ti:Sapphire laser system on a beamline delivering 50 fs pulses at 800 nm with energy up to 25 mJ. In the case of a non-zero time delay we studied the optimal conditions for equilibrated double pulse generation despite perturbation of the generating medium induced by the first pulse. We showed how high harmonic double pulse generation varies with the gas pressure, the excitation energy, the delay and the relative polarization between the two laser pulses.

Daboussi, Sameh; Kazamias, Sophie; Cassou, Kevin; Guilbaud, Olivier; Pittman, Moana; Delmas, Olivier; Neveu, Olivier; Cros, Brigitte; Maynard, Gilles; Ros, David

2013-04-01

448

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

Microsoft Academic Search

The Ω-phase of the liquid sodium α-Ω dynamo experiment at NMIMT in cooperation with LANL has successfully demonstrated the production of a high toroidal field, B{sub Ï} â 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

Stirling A. Colgate; Jui Li; John Finn; Vladimir Pariev; Howard Beckley; Jiahe Si; Joe Martinic; David Westpfahl; James Slutz; Zeb Westrom; Brianna Klein; Paul Schendel; Cletus Scharle; Travis McKinney; Rocky Ginanni; Ian Bentley; Timothy Mickey; Ragnar Ferrel

2010-01-01

449

High Magnetic Shear Gain in a Liquid Sodium Stable Couette Flow Experiment: A Prelude to an - Dynamo  

Microsoft Academic Search

The phase of the liquid sodium - dynamo experiment at New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field B{sub } that is 8xB{sub r}, where B{sub r} is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in

Stirling A. Colgate; Howard Beckley; Jiahe Si; Joe Martinic; David Westpfahl; James Slutz; Cebastian Westrom; Brianna Klein; Paul Schendel; Cletus Scharle; Travis McKinney; Rocky Ginanni; Ian Bentley; Timothy Mickey; Regnar Ferrel; Hui Li; Vladimir Pariev; John Finn

2011-01-01

450

How Can Obese Weight Controllers Minimize Weight Gain During the High Risk Holiday Season? By Self-Monitoring Very Consistently  

Microsoft Academic Search

This study examined the efficacy of augmenting standard weekly cognitive–behavioral treatment for obesity with a self-monitoring intervention during the high risk holiday season. Fifty-seven participants in a long-term cognitive–behavioral treatment program were randomly assigned to self-monitoring intervention or comparison groups. During 2 holiday weeks (Christmas–New Years), the intervention group's treatment was supplemented with additional phone calls and daily mailings, all

Kerri N. Boutelle; Daniel S. Kirschenbaum; Raymond C. Baker; M. Ellen Mitchell

1999-01-01

451

High-Resolution Mapping of Spontaneous Mitotic Recombination Hotspots on the 1.1 Mb Arm of Yeast Chromosome IV  

PubMed Central

Although homologous recombination is an important pathway for the repair of double-stranded DNA breaks in mitotically dividing eukaryotic cells, these events can also have negative consequences, such as loss of heterozygosity (LOH) of deleterious mutations. We mapped about 140 spontaneous reciprocal crossovers on the right arm of the yeast chromosome IV using single-nucleotide-polymorphism (SNP) microarrays. Our mapping and subsequent experiments demonstrate that inverted repeats of Ty retrotransposable elements are mitotic recombination hotspots. We found that the mitotic recombination maps on the two homologs were substantially different and were unrelated to meiotic recombination maps. Additionally, about 70% of the DNA lesions that result in LOH are likely generated during G1 of the cell cycle and repaired during S or G2. We also show that different genetic elements are associated with reciprocal crossover conversion tracts depending on the cell cycle timing of the initiating DSB.

St. Charles, Jordan; Petes, Thomas D.

2013-01-01

452

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 New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field B{sub {phi}} that is {approx_equal}8xB{sub r}, where B{sub r} is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette flow within liquid sodium at a magnetic Reynolds number Rm{approx_equal}120. Small turbulence in stable Taylor-Couette flow is caused by Ekman flow at the end walls, which causes an estimated turbulence energy fraction of ({delta}v/v){sup 2{approx}}10{sup -3}.

Colgate, Stirling A. [T-2, MS B-227, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Department of Physics, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 (United States); Beckley, Howard; Si, Jiahe; Martinic, Joe; Westpfahl, David; Slutz, James; Westrom, Cebastian; Klein, Brianna; Schendel, Paul; Scharle, Cletus; McKinney, Travis; Ginanni, Rocky; Bentley, Ian; Mickey, Timothy; Ferrel, Regnar [Department of Physics, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 (United States); Li, Hui; Pariev, Vladimir [T-2, MS B-227, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Finn, John [T-5, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2011-04-29

453

Factors predicting nongenetic variability in body weight gain induced by a high-fat diet in inbred C57BL/6J mice.  

PubMed

Inbred C57BL/6J mice displayed large individual variations in weight gain when fed a high-fat diet (HFD). The objective of this study was to examine whether this predominantly nongenetic variability could be predicted by relevant baseline features and to explore whether variations in these significant features were influenced during pregnancy and/or lactation. Fat mass (FM), fat-free mass (FFM), food intake (FI), resting metabolic rate (RMR), physical activity (PA), and body temperature (T(b)) were all evaluated at baseline in 60 mice (aged 10-12 weeks) before HFD feeding. Regression analyses showed that baseline FM was a strong positive predictor of weight gain between 4 and 16 weeks of HFD. Baseline PA was negatively associated with weight gain at week 8, 12, and 16, and baseline FFM had a positive effect at week 12 and 16. In a second experiment, 40 female mice were mated and litter sizes (LS) were manipulated on day 3 of lactation. Weaning weight and postweaning growth rate (GR) had positive impacts on FM and FFM at age 9 weeks (FM, P = 0.001; FFM, P < 0.001: n = 97). Lactation LS had a negative effect on weaning weight and a positive effect on postweaning GR. In conclusion, our results show that obesity induced by HFD was associated with a higher baseline FM, a higher baseline FFM and a lower baseline PA level before the exposure of HFD. Two of these traits (FM and FFM) were influenced by lactation LS via weaning weight and postweaning GR. PMID:21720432

Zhang, Li-Na; Morgan, David G; Clapham, John C; Speakman, John R

2011-06-30

454

Low-frequency electrical noise of high-speed, high-performance 1.3 ?m strained multiquantum well gain-coupled distributed feedback lasers  

NASA Astrophysics Data System (ADS)

Measurements of low-frequency electrical noise (LFN) in an in-phase gain-coupled distributed feedback lasers with etched quantum-well active-layers emitting at 1.3 ?m wavelength have been conducted. In particular, the injected current dependence of LFN is investigated over a wide range of injection current (from 10-2 ?A to 60 mA). Pure 1/f noise spectra were observed in all measurements. The current dependence of the 1/f noise strongly correlates to the I-V characteristics. We find that noise from different mechanisms dominates when the lasers operate in different ranges of injection currents.

Chen, X. Y.; Deen, M. J.; Peng, C. X.

2000-12-01

455

New insights into hydrochemical processes in lowland river systems gained from in situ, high-resolution monitoring  

NASA Astrophysics Data System (ADS)

This work focuses on the insights obtained from in situ, high-resolution hydrochemical monitoring in three lowland UK catchments experiencing different levels of nutrient enrichment. Between November 2009 and February 2012, the upper River Kennet, the River Enborne and The Cut, all located within the Thames basin, southeast England, were instrumented with in situ analytical equipment to make hourly measurements of a range of hydrochemical determinands. The upper River Kennet is a rural catchment with limited effluent inputs above the selected monitoring point. The River Enborne is a rural catchment, impacted by agricultural runoff, and septic tank and sewage treatment works (STWs) discharges. The Cut is a highly urbanised system significantly affected by STW discharges. On the upper River Kennet and the River Enborne hourly measurements of Total Reactive Phosphorus (TRP) were made using a Systea Micromac C. In addition on the River Enborne, a Hach Lange Nitratax was used to measure nitrate (NO3). On The Cut both Total P and TRP were measured using a Hach Lange Phosphax Sigma. At all stations nutrient monitoring was supplemented with hourly pH, chlorophyll, dissolved oxygen, conductivity, turbidity and water temperature using YSI 6600 Multi-parameter sondes. Instream hydrochemical dynamics were investigated using non-stationary time-series analysis techniques. The results reveal complex nutrient dynamics, with diurnal patterns which exhibit seasonal changes in phase and amplitude, and are influenced by flow conditions, shading and nutrient sources. On the River Enborne a marked diurnal cycle was present within the streamwater NO3 time-series. The cycle was strongest in the spring before riparian shading developed. At times of low flow a two peak diurnal cycle was also evident in the streamwater NO3 time-series. The reduction in diurnal NO3 processing after the development of riparian shading was also accompanied by a marked drop in dissolved oxygen at this time. The presence of a two peak diurnal cycle is indicative of the dominance of STW discharges to the system, as STW discharges exhibit a marked two peak diurnal cycle associated with peak water usage. This two peak diurnal cycling can also been seen in the River Enborne TRP data. The dominance of effluent discharges was also evident in the River Enborne seasonal NO3 and TRP dynamics. Both determinands displayed summer time peaks caused by the reduced dilution capacity of the system and increased water residence time during the low flow summer months. The TP and TRP dynamics on The Cut were highly complex with significant diurnal fluctuations. Although, a two peak diurnal signal was evident within the TRP time-series it was difficult to characterise due to the complexity of the dynamics observed. Monitoring on the upper River Kennet highlighted the challenges associated with undertaking in situ analytical monitoring without mains electricity. Resampling of the data at lower sampling frequencies demonstrated that within the point-source dominated catchments, daily monitoring was sufficient for accurate load estimation.

Wade, Andrew; Palmer-Felgate, Elizabeth; Halliday, Sarah; Skeffington, Richard; Loewenthal, Matthew; Jarvie, Helen; Bowes, Michael; Greenway, Gillian; Haswell, Stephen; Bell, Ian; Joly, Etienne; Fallatah, Ahmed; Neal, Colin; Williams, Richard; Gozzard, Emma; Newman, Jonathan

2013-04-01

456

Superimposed high-frequency jet ventilation combined with continuous positive airway pressure/assisted spontaneous breathing improves oxygenation in patients with H1N1-associated ARDS  

PubMed Central

Background Numerous cases of swine-origin 2009 H1N1 influenza A virus (H1N1)-associated acute respiratory distress syndrome (ARDS) bridged by extracorporeal membrane oxygenation (ECMO) therapy have been reported; however, complication rates are high. We present our experience with H1N1-associated ARDS and successful bridging of lung function using superimposed high-frequency jet ventilation (SHFJV) in combination with continuous positive airway pressure/assisted spontaneous breathing (CPAP/ASB). Methods We admitted five patients with H1N1 infection and ARDS to our intensive care unit. Although all patients required pure oxygen and controlled ventilation, oxygenation was insufficient. We applied SHFJV/CPAP/ASB to improve oxygenation. Results Initial PaO2/FiO2 ratio prior SHFJV was 58-79 mmHg. In all patients, successful oxygenation was achieved by SHFJV (PaO2/FiO2 ratio 105-306 mmHg within 24 h). Spontaneous breathing was set during first hours after admission. SHFJV could be stopped after 39, 40, 72, 100, or 240 h. Concomitant pulmonary herpes simplex virus (HSV) infection was observed in all patients. Two patients were successfully discharged. The other three patients relapsed and died within 7 weeks mainly due to combined HSV infection and in two cases reoccurring H1N1 infection. Conclusions SHFJV represents an alternative to bridge lung function successfully and improve oxygenation in the critically ill.

2012-01-01

457

Transient hot-carrier optical gain in a gain-switched semiconductor laser  

NASA Astrophysics Data System (ADS)

The transient optical gain was quantitatively determined from the rise time of output pulses of a gain-switched semiconductor laser via impulsive optical pumping. The optical gain for a high carrier density during gain switching was greatly reduced from that during steady-state operation because of hot carriers.

Ito, Takashi; Chen, Shaoqiang; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Pfeiffer, Loren N.; West, Ken W.

2013-08-01

458

Development of sub-nanosecond, high gain structures for time-of-flight ring imaging in large area detectors  

NASA Astrophysics Data System (ADS)

Microchannel plate photomultiplier tubes (MCPs) are compact, imaging detectors, capable of micron-level spatial imaging and timing measurements with resolutions below 10 ps. Conventional fabrication methods are too expensive for making MCPs in the quantities and sizes necessary for typical HEP applications, such as time-of-flight ring-imaging Cherenkov detectors (TOF-RICH) or water Cherenkov-based neutrino experiments. The Large Area Picosecond Photodetector Collaboration (LAPPD) is developing new, commercializable methods to fabricate 20 cm2 thin planar MCPs at costs comparable to those of traditional photo-multiplier tubes. Transmission-line readout with waveform sampling on both ends of each line allows the efficient coverage of large areas while maintaining excellent time and space resolution. Rather than fabricating channel plates from active, high secondary electron emission materials, we produce plates from passive substrates, and coat them using atomic layer deposition (ALD), a well established industrial batch process. In addition to possible reductions in cost and conditioning time, this allows greater control to optimize the composition of active materials for performance. We present details of the MCP fabrication method, preliminary results from testing and characterization facilities, and possible HEP applications.

Wetstein, Matthew; Lappd Collaboration

2011-05-01

459