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


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)



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


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)



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.



Helicopter high gain control  

NASA Technical Reports Server (NTRS)

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

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



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



Spatially-selective amplified spontaneous emission source derived from an ultrahigh gain solid-state amplifier.  


An investigation is made into the performance of a high power solid-state amplified spontaneous emission (ASE) source with near-diffraction-limited beam quality. The radiation from this ASE source has high spatial quality and power, but unlike a laser it has a high misalignment tolerance and does not require a precisely aligned cavity. The source is based on a diode-pumped Nd:YVO4 laser crystal in a bounce amplifier geometry with a uniquely ultra-high gain (~104-105). Double-pass ASE radiation with high power levels (>6W) is achieved in a near-diffraction-limited spatial quality. We further demonstrate that the double-pass ASE source also displays high spatial selectivity and capability to compensate for a phase diffuser, inserted in the double-pass arm, with only a small degradation in beam quality and power. PMID:19516475

Smith, G; Damzen, M J



Unidirectional high gain brake stop  

NASA Technical Reports Server (NTRS)

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

Lang, David J. (Inventor)



High-gain high-pressure highly efficient COIL  

Microsoft Academic Search

The activity of development a COIL with high potential recovered pressure, high gain and efficiency is described. Two nozzle banks with conical supersonic nozzles for the driver nitrogen but with different nozzle arrangements have been developed for generation of the gain flow of chemical oxygen-iodine laser. The nozzle banks were supplied by oxygen flow from the cross-flow singlet oxygen generator

Marsel V. Zagidullin; Valery D. Nikolaev; Michael I. Svistun; Nikolai A. Khvatov; Gordon D. Hager



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

Microsoft Academic Search

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

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



Undulator interruption in high-gain free electron lasers  

SciTech Connect

The effect of interrupting an undulator on the performance of high-gain free-electron lasers (FELs) is evaluated by analyzing 1-D Maxwell-Vlasov equations. It is found that the effect is small for a reasonable length of the interruptions for FEL parameters envisaged for short wavelength self-amplified spontaneous emission (SASE). Since the interruptions provide valuable space for quadrupoles and diagnostics, and at the same time permit a greater flexibility in mechanical design, the result of this paper is encouraging for construction of long undulator magnets required for SASE.

Kim, K.J.



High-Gain Magnetized Inertial Fusion  

NASA Astrophysics Data System (ADS)

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

Slutz, Stephen A.; Vesey, Roger A.



High-gain magnetized inertial fusion.  


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

Slutz, Stephen A; Vesey, Roger A



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.



The Arabidopsis gain-of-function mutant dll1 spontaneously develops lesions mimicking cell death associated with  

E-print Network

The Arabidopsis gain-of-function mutant dll1 spontaneously develops lesions mimicking cell death contributed equally to this work. Summary We describe the characterization of a novel gain®cant overlap exist between the signalling pathways leading to resistance- and disease-associated cell death

Raina, Ramesh


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

SciTech Connect

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

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



Ignition and high gain with ultrapowerful lasers  

Microsoft Academic Search

Ultrahigh intensity lasers can potentially be used in conjunction with conventional fusion lasers to ignite inertial confinement fusion (ICF) capsules with a total energy of a few tens of kilojoules of laser light, and can possibly lead to high gain with as little as 100 kJ. A scheme is proposed with three phases. First, a capsule is imploded as in

Max Tabak; James Hammer; Michael E. Glinsky; William L. Kruer; Scott C. Wilks; John Woodworth; E. Michael Campbell; Michael D. Perry; Rodney J. Mason



Theoretical study of amplified spontaneous emission using a model based on a geometrically dependent gain coefficient  

NASA Astrophysics Data System (ADS)

It is shown that a model based on a geometrically dependent gain coefficient (GDGC), which is characterized by gain parameters (m?, {\\gamma }_{L}^{\\max }, b), introduces a powerful method to describe amplified spontaneous emission (ASE) intensity behavior and its bandwidth reduction when the ASE is propagating along the z-direction. The model also gives correct predictions for unsaturated and saturated gain coefficients and the frequency dependence of the ASE output intensity in a given laser system. For the calculation, the GDGC model in saturated and unsaturated conditions along with the intensity rate equation were applied, and for verification of the model the reported ASE intensity measurements and the measured bandwidth reduction in KrF lasers were utilized. The present model will have applications in any type of pulsed laser system of different active media and different dimensions without going through complicated analysis or utilizing heavy computer numerical computations. Details of the present approach will be given and the excellent agreement with the available and typical experimental measurements for KrF lasers confirms the validity of the proposed GDGC model.

Hariri, A.; Sarikhani, S.



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



High Gain Fast Ignition Point Design  

NASA Astrophysics Data System (ADS)

The fast ignition (FI) approach to inertial confinement fusion offers the potential for achieving the high target gains required for Inertial Fusion Energy (IFE). In FI a D-T fuel capsule is first compressed via a quasi-isochoric implosion to form a high density core, and then ignited with a short-pulse laser-generated relativistic electron beam. This paper reports progress on the development of a point design for an indirect-drive re-entrant cone FI target. The design incorporates 2-D radiation-hydrodynamics modeling of the capsule implosion around a cone, particle-in-cell (PIC) modeling of the short-pulse laser absorption and electron generation at the cone tip, and hybrid-PIC modeling of the electron transport and heating in the compressed fuel. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Patel, P. K.; Amendt, P.; Chen, C. D.; Clark, D.; Cohen, B.; Hey, D. S.; Divol, L.; Higginson, D.; Ho, D.; Homoelle, D.; Kemp, A. J.; Key, M. H.; Larson, D.; Lasinski, B.; Le Pape, S.; Ma, T.; McLean, H.; Meeker, D. J.; Ping, Y.; Shay, H.; Strozzi, D. J.; Tabak, M.; Town, R. P. J.; Westover, B.; Wilks, S. C.



Ignition and high gain with ultrapowerful lasers  

SciTech Connect

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

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



Progress toward high-gain laser fusion  

NASA Astrophysics Data System (ADS)

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

Storm, Erik



High gain double-pass L-band EDFA with dispersion compensation as feedback loop  

NASA Astrophysics Data System (ADS)

We demonstrate an efficient double-pass L-band erbium-doped fiber amplifier (EDFA) incorporating chirped fiber Bragg grating (CFBG). The amplifier structure exploits the characteristics of CFBG to reflect the amplified signal back into the gain medium, filter out the recycled forward amplified spontaneous emission and block the residual 1480 nm pump power. The amplifier configuration has high gain and low noise figures as compared to double-pass EDFA using broadband mirror. The demonstrated amplifier has gain of more than 48 dB and low noise figure of less than 4 dB at low input signal power of -40 dBm.

Haleem, M. R.; Al-Mansoori, M. H.; Jamaludin, M. Z.; Abdullah, F.; Din, N. Md



A very high frequency CMOS Variable Gain Amplifier  

E-print Network

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

Tan, Siang Tong



The Nature of Spontaneity in High Quality Mathematics Learning Experiences  

ERIC Educational Resources Information Center

Spontaneity has been linked to high quality learning experiences in mathematics (Csikszentmihalyi & Csikszentmihalyi, 1992; Williams, 2002).This paper shows how spontaneity can be identified by attending to the nature of social elements in the process of abstracting (Dreyfus, Hershkowitz, & Schwarz, 2001). This process is elaborated through an…

Williams, Gaye



High gain feedback and telerobotic tracking  

NASA Technical Reports Server (NTRS)

Asymptotically stable linear time invariant systems are capable of tracking arbitrary reference signals with a bounded error proportional to the magnitude of the reference signal (and its derivatives). It is shown that a similar property holds for a general class of nonlinear dynamical systems which includes all robots. As in the linear case, the error bound may be made arbitrarily small by increasing the magnitude of the feedback gains which stabilize the system.

Koditschek, D. E.



High-fidelity all-fiber amplification of a gain-switched laser diode.  


We demonstrate a multistage erbium fiber amplifier seeded by a gain-switched laser diode operating at a wavelength of 1550 nm and a repetition rate of 1 MHz. The pulse energy is 0.5 ?J, and the pulse duration is 40 ps, resulting in a peak power of 11.4 kW. The three-stage all-fiber amplifier system is designed to avoid any spectral distortions induced by gain saturation or nonlinear effects and high levels of amplified spontaneous emission. The output pulses are close to transform limited with a Gaussian pulse envelope. PMID:25090084

Abrardi, Laura; Gusowski, Marek A; Feurer, Thomas



Resonator modes in high gain free electron lasers  

SciTech Connect

When the gain in a free electron laser is high enough to produce optical guiding, the resonator mode distorts and loses its forward-backward symmetry. We show that the resonator mode in a high gain FEL can be easily constructed using the mode expansion technique taken separately in the interaction and the free-space regions. We propose design strategies to achieve maximal gain and optimal mode quality, and discuss the stability of the optimized mode. 11 refs., 4 figs.

Xie, Ming (Lawrence Berkeley Lab., CA (USA)); Deacon, D.A.G. (Deacon Research, Palo Alto, CA (USA)); Madey, J.M.J. (Duke Univ., Durham, NC (USA). Dept. of Physics)



Optical gain, spontaneous and stimulated emission of surface plasmon polaritons in confined plasmonic waveguide.  


We develop a theoretical model to compute the local density of states in a confined plasmonic waveguide. Based on this model, we derive a simple formula with a clear physical interpretation for the lifetime modification of emitters embedded in the waveguide. The gain distribution within the active medium is then computed following the formalism developed in a recent work [Phys. Rev. B 78, 161401 (2008)], by taking rigorously into account the pump irradiance and emitters lifetime modifications in the system. We finally apply this formalism to describe gain-assisted propagation in a dielectric-loaded surface plasmon polariton waveguide. PMID:20721019

Colas des Francs, G; Bramant, P; Grandidier, J; Bouhelier, A; Weeber, J-C; Dereux, A



High-gain volume ignition for inertial confinement fusion (ICF)  

Microsoft Academic Search

Since 1976, volume ignition calculations of pellet-fueled inertial confinement fusion have shown very high fusion gains due to the strong temperature increases caused by self-heating. This phenomenon was first reported in 1978 (Hora & Ray) and subsequently named the ‘‘Wheeler modes.’’ The very low optimum initial temperatures (≊1 keV) and the fuel burn of up to 80% permit gains of

H. Hora; S. Eliezer; J. M. Martinez-Val; G. H. Miley



Superradiance in the high-gain free-electron laser  

Microsoft Academic Search

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

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



Caustic Singularities Of High-Gain, Dual-Shaped Reflectors  

NASA Technical Reports Server (NTRS)

Report presents study of some sources of error in analysis, by geometric theory of diffraction (GTD), of performance of high-gain, dual-shaped antenna reflector. Study probes into underlying analytic causes of singularity, with view toward devising and testing practical methods to avoid problems caused by singularity. Hybrid physical optics (PO) approach used to study near-field spillover or noise-temperature characteristics of high-gain relector antenna efficiently and accurately. Report illustrates this approach and underlying principles by presenting numerical results, for both offset and symmetrical reflector systems, computed by GTD, PO, and PO/GO methods.

Galindo, Victor; Veruttipong, Thavath W.; Imbriale, William A.; Rengarajan, Sambiam



High gain proportional rf control stability at TESLA cavities  

NASA Astrophysics Data System (ADS)

Fast proportional rf control is used as the basis for rf field regulation in actual linear accelerator projects like the international linear collider (ILC) and the European x-ray free electron laser (XFEL) based on TESLA technology. Additional control loops improve the field regulation by treating repetitive effects and compensating the beam loading. Nevertheless, the ability for high gain operation of the fast loops is desirable for the strong suppression of nonpredictive and nonrepetitive disturbances. TESLA cavities host nine fundamental modes (FMs) where only one is used for beam acceleration. The unwanted FMs have a significant influence on the proportional rf control loop stability at high gains. Within this paper, the stability of proportional rf control loops taking the FMs and digitalization effects into account will be discussed in detail together with measures enabling a significant increase of the gain values.

Vogel, Elmar



High gain proportional rf control stability at TESLA cavities  

Microsoft Academic Search

Fast proportional rf control is used as the basis for rf field regulation in actual linear accelerator projects like the international linear collider (ILC) and the European x-ray free electron laser (XFEL) based on TESLA technology. Additional control loops improve the field regulation by treating repetitive effects and compensating the beam loading. Nevertheless, the ability for high gain operation of

Elmar Vogel



Reducing the convergence ratio of high gain ICF targets  

Microsoft Academic Search

Two ways of reducing the convergence ratio of high gain inertially confined fusion (ICF) targets have been studied using computer simulations. The convergence ratio decreases faster than predicted by the simple geometrical scaling law when the initial gaseous D-T density of the target is increased. Reducing the convergence ratio by changing the driver pulse shape is not energy efficient because

Yuli Pan



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.



High Gain Microstrip Antenna Using Planar Circularly Symmetric EBG Structures  

Microsoft Academic Search

In this paper, a design of high gain microstrip antenna using planar circularly symmetric electromagnetic band gap structures (PCS-EBG) is presented. The EBG rings round the antenna reduce surface waves propagating along the substrate and support the radiation of electromagnetic (EM) energy in plane perpendicular to the antenna. Because of the circularly symmetry the surface waves are supressed in all




Radiation Response of Emerging High Gain, Low Noise Detectors  

NASA Technical Reports Server (NTRS)

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

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



High-Resolution Stimulated Raman Gain Spectroscopy of Parahydrogen Crystals  

E-print Network

High-Resolution Stimulated Raman Gain Spectroscopy of Parahydrogen Crystals Takamasa Momose1-H2 crystals with varying ortho-H2 concentrations is reported. A crys- tal containing 0.06% of ortho in a para-H2 crystal.5 The sharpness of infrared transition stems from the weak intermolecular interaction

Oka, Takeshi


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

NASA Astrophysics Data System (ADS)

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

Chvykov, Vladimir; Nees, John; Krushelnick, Karl



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

NASA Astrophysics Data System (ADS)

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 beam, and demands detailed distribution information of electron beam in six-dimension. The typical accelerator system for single-pass FEL consists of a photocathode RF gun injection system, a linac and magnetic bunch compressors, and a long undulator. The major challenges in beam diagnostics for single-pass FEL are to characterize the pico-seconds high-brightness electron beam in six-dimension produced by photocathode RF gun injector, and improve the stability and reliability of the photocathode RF gun injection system. Characterization of short electron bunch (˜100 fs) produced by the compressors, and co-align the electron beam with FEL radiation inside long undulator are also critical for FEL performance. We will discuss many diagnostic techniques developed at the Brookhaven Accelerator Test Facility (ATF) for the photocathode RF gun injection system, present several techniques for femto-seconds bunch length measurement, especially RF kicker cavity. Tomography technique for both transverse and longitudinal phase space measurements is discussed. Concept of multiple alignment-laser stations is present for beam alignment in the long undulator.

Wang, X. J.



Cathode driven high gain crossed-field amplifier  

NASA Astrophysics Data System (ADS)

The objective of this three-phase program is to achieve the design of a cathode driven high gain re-entrant Crossed Field Amplifier capable of meeting the parameters of Raytheon Company specification No. 968838 dated 10 May 1978. The effort includes the fabrication and test of three developmental and four final configuration tubes. One final configuration tube will be life tested and two will be delivered to the Navy. The tasks discussed during this report period relate to the cold tests performed on various subassemblies of model no. 4 and on the sealed-in model no. 4 of the S-band high gain cathode driven crossed field amplifier. Based on the performance of model no. 3 certain remedial measures have been implemented in model no. 4 that have resulted in the elimination of key resonances within the tube and an improvement in the isolation between the cathode and anode circuits.



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.



High-Gain Harmonic-Generation Free-Electron Laser  

Microsoft Academic Search

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

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



High-power near-diffraction-limited solid-state amplified spontaneous emission laser devices.  


We present investigations into high-power scaling of solid-state amplified spontaneous emission (ASE) laser sources by use of two high-gain (~10(4)) Nd:YVO(4) bounce amplifiers. The sources deliver high power with a high-quality spatial output, but unlike a laser they have a high misalignment tolerance and do not require a precisely aligned cavity. In one system with two amplifiers, we demonstrate an ASE source with 24.5W of output power with good spatial quality, M(2)<2.5 in the horizontal and M(2)<1.2 in the vertical. In a more sophisticated setup, the two amplifiers are arranged in a loop configuration producing 30W of ASE output with near-diffraction-limited spatial quality, with M(2)<1.3 in the horizontal and M(2)<1.2 in the vertical, at an ~38% optical-to-optical conversion efficiency. PMID:17603611

Smith, G; Shardlow, P C; Damzen, M J



High gain/broadband oxide glasses for next generation Raman amplifiers  

NASA Astrophysics Data System (ADS)

Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are larger and the operating wavelength is fixed only by the pump wavelength and the bandwidth of the Raman active medium. In this context, glasses are the material of choice for this application due to their relatively broad spectral response, and ability of making them into optical fiber. This dissertation summarizes findings on different oxide-based glasses that have been synthesized and characterized for their potential application as Raman gain media. Two main glass families were investigated: phosphate-based glass matrices for broadband Raman gain application and TeO2-based glasses for high Raman gain amplification. A phosphate network was preferred for the broadband application since the phosphate Raman active modes can provide amplification above 1000 cm-1, whilst TeO2-based glasses were selected for the high gain application due to their enhanced nonlinearities and polarizabilities among the other oxide-based network formers. The results summarized in this dissertation show that phosphate-based glasses can provide Raman amplification bandwidths of up to 40 THz, an improvement of almost 5 times the bandwidth of SiO2. On the other hand, tellurite-based glasses appear to be promising candidates for high gain discrete Raman applications, providing peak Raman gain coefficients of up to 50 times higher than SiO 2, at 1064 nm. Although, visible spontaneous Raman scattering cross-section measurement is the most frequently used tool for estimating the strength and spectral distribution of Raman gain in materials, especially glasses, there are some issues that one needs to be aware when conducting these measurements near the absorption band edge of the material. This led to the detection of an inherent frequency-dispersion in the Raman susceptibility and a resonant enhancement phenomenon when measurements were conducted near the absorption edge of the material.

Rivero, Clara A.


High-Gain Shock Ignition on the National Ignition Facility  

NASA Astrophysics Data System (ADS)

Shock ignition offers the possibility for a near-term test of high-gain ICF on the NIF at less than 1MJ drive energy and with day-1 laser hardware. We will summarize the status of target performance simulations, delineate the critical issues and describe the R&D program to be performed in order to test the potential of a shock-ignited target on NIF. In shock ignition, compressed fuel is separately ignited by a late-time laser-driven shock and, because capsule implosion velocities are significantly lower than those required for conventional hotpot ignition, simulations indicate that fusion energy gains of 60 may be achievable at laser energies around 0.5MJ. Like fast ignition, shock ignition offers high gain but requires only a single laser with less demanding timing and focusing requirements. Conventional symmetry and stability constraints apply, thus a key immediate step towards attempting shock ignition on NIF is to demonstrate adequacy of low-mode uniformity and shock symmetry under polar drive

Perkins, L. J.; Lafortune, K.; Bailey, D.; Lambert, M.; MacKinnon, A.; Blackfield, D.; Comley, A.; Schurtz, G.; Ribeyre, X.; Lebel, E.; Casner, A.; Craxton, R. S.; Betti, R.; McKenty, P.; Anderson, K.; Theobald, W.; Schmitt, A.; Atzeni, S.; Schiavi, A.



L-band automatic-gain-controlled erbium-doped fiber amplifier utilizing C-band backward-amplified spontaneous emission and electrical feedback monitor.  


A new L-band automatic-gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) for dense wavelength-division-multiplexing transmission systems is presented, in which a single 1480 nm laser with an internal thermoelectric cooler is used as a primary pump for stable amplification. All C-band amplified spontaneous emission (ASE) is recycled by the secondary pump to enhance the gain efficiency. A fraction of the output signal is used as an electrical feedback monitor for the AGC to improve the gain-clamped (GC) flatness. Experimental results prove that the AGC EDFA has a gain flatness of better than 0.46 dB/40 nm, i.e., below 1.5%, and a higher gain of approximately 36.5 dB compared to that of approximately 35.3 dB for the conventional GC EDFA at -30 dBm input signal power. The best gain flatness of +/-0.25 dB can be achieved over the dynamic range greater than 20 dB. The dynamic range of noise figure is between 6.7 and 7.1. The 3 dB down bandwidth is more than 40 nm. Overall dynamics measurements for the AGC EDFA feedback stabilization have been carried out. The recorded corresponding rise time of 1.565 ms indicates that the system does not exhibit any overshoot of gain or ASE variation due to the signal at the beginning of the pulse. PMID:19209194

Shen, Jyi-Lai; Lee, Yueh-Chien; Huang, Chia-Chih



A high gain antenna system for airborne satellite communication applications  

NASA Technical Reports Server (NTRS)

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

Maritan, M.; Borgford, M.



Avoiding Obstructions in Aiming a High-Gain Antenna  

NASA Technical Reports Server (NTRS)

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

Edmonds, Karina



Spontaneous Raman scattering as a high resolution XUV radiation source  

NASA Technical Reports Server (NTRS)

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

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



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



Possibility of a high-power, high-gain FEL amplifier  

Microsoft Academic Search

High-gain FEL amplifiers offer many unique advantages such as robust operation without a high-Q optical cavity and potentially high extraction efficiencies with the use of tapered wigglers. Although a high average power, cw FEL amplifier has not been demonstrated, many key physics issues such as electron beam brightness requirements, single-pass gain, saturation, etc. have been resolved. In this paper, we

Dinh C. Nguyen; Henry P. Freund



Possibility of a high-power, high-gain amplifier FEL  

Microsoft Academic Search

High-gain amplifier FEL offer many unique advantages such as robust operation without a high-Q optical cavity and potentially high extraction eaciencies with the use of tapered wigglers. Although a high average power, cw amplifier FEL has not been demonstrated, many key physics issues such as electron beam brightness requirements, single-pass gains, saturation, etc. have been resolved. In this paper, we

D. C. Nguyen; H. P. Freund



Spontaneous quenches of a high temperature superconducting pancake coil  

SciTech Connect

A double-pancake coil made of Bi-2223/Ag high temperature superconducting (HTS) tape was constructed with an embedded heater and graded conductors to study the stability and quench propagation in HTS coils. The experiments were performed with liquid nitrogen and gaseous helium cooling in temperatures ranging from 5 to 77 K. The coil was very stable, and no ``normal`` zone was sustained or propagated with local pulsed heating. However, spontaneous quenches of the cod were experienced. This was found to be the result of having the coil current higher than that of the lower I{sub c} sections of the coil for a long time. This quench process took minutes to develop--much longer than would be expected in a low temperature superconducting coil. The quench behaved more like a spreading and continuous heating of an increasingly larger partially resistive section of the coil than like a sequential ``normal`` front propagation.

Lue, J.W.; Lubell, M.S. [Oak Ridge National Lab., TN (United States); Aized, D.; Campbell, J.M.; Schwall, R.E. [American Superconductor Corp., Westborough, MA (United States)



Spontaneous Raman Scattering Diagnostics for High-pressure Gaseous Flames  

NASA Technical Reports Server (NTRS)

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

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



Estimation of peak Raman gain coefficients for Barium-Bismuth-Tellurite glasses from spontaneous Raman cross-section experiments.  


In this paper we explore the TeO(2)-Bi(2)O(3)-BaO glass family with varied TeO(2) concentration for Raman gain applications, and we report, for the first time, the peak Raman gain coefficients of glasses within this glass family extrapolated from non-resonant absolute Raman cross-section measurements at 785 nm. Estimated Raman gain coefficients show peak values of up to 40 times higher than silica for the main TeO(2) bands. Other optical properties, including index dispersion from the visible to the long wave Infrared (LWIR) are also summarized in this paper. PMID:19466157

Jackson, Jessica; Smith, Charmayne; Massera, Jonathan; Rivero-Baleine, Clara; Bungay, Corey; Petit, Laeticia; Richardson, Kathleen



Optical resonator design studies for high gain free electron lasers  

SciTech Connect

Optical resonator design studies have been performed for free electron laser oscillator configurations driven by an rf linac. The resonator designs were for an FEL configuration with large saturated gain (50 to 100%) through the electron beam-wiggler region. For the case of large saturated gain, the power loading on the mirrors is reduced, however, the resonator design must compensate for the optical gain and refractive properties of the electron beam.

McVey, B.D.; Tokar, R.L.; Bender, S.C.



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


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



High-Power High-Gain Diffraction-Limited Emission from Single-Mode Tapered Semiconductor Optical Amplifiers  

NASA Astrophysics Data System (ADS)

The realization of high-power (over 1 Watt), coherent diode lasers will open up new possibilities in printing, biomedicine, efficient pumping of solid state lasers and rare-earth doped fiber amplifiers, free-space optical communication, and nonlinear frequency conversion to the blue spectral region. The most successful approach toward high-power coherent light sources to date is the master oscillator power amplifier (MOPA) configuration which consists of a single-mode master laser source and a large-area traveling -wave-amplifier (TWA). The design and fabrication of this large-area TWA plays a determining role in the overall characteristics and performance of the device. In my research work, high-power tapered semiconductor optical amplifiers have been investigated and fabricated. High -power, high-gain, single-mode and diffraction-limited emission has been obtained. Several approaches to improve the amplifier's performance have been proposed and demonstrated, including: (1) the integration of a single-mode preamplifier with the tapered amplifier leads to single-mode operation even when the amplifier is pumped at high currents, (2) a self -aligned dissipating grid efficiently suppresses high-order spatial modes oscillation and reduces amplified spontaneous emission power, and (3) an angled-facet tapered amplifier with very low effective reflectivity was demonstrated. As much as 5-W pulsed power with a 0.94-W/A slope efficiency was achieved from a 2-mm-long amplifier, by injecting an incident power of only 20-mW from a laser diode. Low effective reflectivity of less than 4 times 10^{-5} can be obtained routinely. Record high gains have been achieved, including an internal small-signal gain of 35-dB, and external and internal saturated gains of 23 dB and 29 dB, respectively. The far-field pattern was found to be dominated by a diffraction -limited single lobe containing more than 85% of the total emitted output power. Additionally, we have developed a new die attach process. CW powers of 400 mW and 800 mW were obtained from a 1-mm-long and 2-mm-long amplifier, respectively, when injected with an incident power of 10 mW.

Yeh, Ping-Hui Sophia



Dual-Band Plasmonic Enhancement of Ag-NS@SiO 2 on Gain Medium’s Spontaneous Emission  

Microsoft Academic Search

We present a theoretical study on plasmonic enhancement of molecular fluorescence near a nanocomposite, Ag nanoshell (Ag-NS)\\u000a coated by a gain medium of molecule-doped SiO2 layer. We use an average enhancement factor (AEF), which considers contributions from all possible orientations and locations\\u000a of molecules in the silica layer to estimate the overall performance of Ag-NS@SiO2 at specific excitation and emission

Jiunn-Woei Liaw; Chuan-Li Liu; Mao-Kuen Kuo


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

NASA Astrophysics Data System (ADS)

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

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



High Gain Transformerless DC-DC Converters for Renewable Energy Sources  

E-print Network

coupled inductors to extend gain, assist in turning off rectifier diodes, or both. Wai et al. [2] propose a 6 boost converter with a coupled inductor that provides both additional gain and regenerative snubbing. Wuhua et al. [3] propose a converter... using a complicated coupled inductor to provide high gains and lossless snubbing. Wai et al. [4] propose a multiple- input converter for fuel cell vehicles that uses coupled inductors to provide additional gain and alleviate reverse recovery problems...

Denniston, Nicholas Aaron



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

NASA Astrophysics Data System (ADS)

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

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



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



High peak power conversion and high gain in pulsed cladding-pumped fiber Raman amplifier  

Microsoft Academic Search

We demonstrate an efficient high peak power pulsed cladding-pumped fiber Raman amplifier. The output Stokes peak power is over 200 W. The peak power conversion efficiency exceeds 75% and the on-off peak gain is nearly 65 dB.

J. Ji; C. A. Codemard; J. K. Sahu; M. Ibsen; J. Nilsson



High-gain Tm-doped fluoride fiber amplifier  

Microsoft Academic Search

A diode-pumped Tm-doped fiber-optic amplifier that has a small-signal gain of >30 dB at 1870 nm is reported. Output pulses of up to 3-W peak power at a 1-60-kHz repetition rate can be generated by amplification of 20-40-ns laser diode pulses of up to 2-mW launched peak power. The output signal quality, i.e., the ratio of the output pulse energy

Marc Eichhorn



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




[Basic concepts on the assessment of arterial baroreceptor sensitivity with non invasive methods. Estimate of the spontaneous gain of the arterial baroreceptor].  


Arterial baroreceptors are sensitive to variation in both blood and pulse pressure. When there is an increase in those pressures, the baroreceptors increase the rhythm in which electric impulses are discharged. The impulses are transmitted by the receptors to the nervous centres of the brainstem. Once processed, these signals turn into sympathetic and vagal impulses. The vagal efferents control heart rate and the sympathetic efferents control heart rate, myocardial contractility and peripheral resistance. If there is an increase in blood pressure, then there will be a reflex decrease in the sympathetic activity and an increase in the parasympathetic one. The cardiac cronotropic response to blood pressure variation is very fast-with a delay of one or two beats. The amplitude of the response is a sigmoidal function. The greatest inclination of the response curve, that is to say, the area of greatest variation of the RR interval per unit of pressure, characterises the gain of the baroreceptors. The traditional method for obtaining the gain of the baroreceptor is a pharmacological one. Generally, the patient is given phenilephrine intravenously, in bolus and then the correlation between heart rate and the increase in intra-arterial blood pressure (reflex bradycardia) is calculated. Lately, it has been used the calculation of the spontaneous gain of the baroreceptor starting from a study carried out on the normal fluctuations in blood pressure and in the pulse interval both in time and frequency domain. The first case deals with the calculation of the gain of the function of transfer between the variations both in blood pressure and the RR intervals in the LF and the HF bands. The second case deals with the analysis of the occurrence of sequences of three beats with successive increases or decreases in blood pressure and in the RR interval. The gain is obtained from the linear regression of all the sequences. The application of these techniques to the recordings of blood pressure obtained by non-invasive methods (Finapress) makes possible that this procedure be followed under real conditions since it requires no previous stimulation of the cardiovascular system, which would probably interfere with the mechanisms to be evaluated, and requires no equipment in the condition which is normally required by experimental methodology. PMID:8763511

Costa, O; Lago, P; Miranda, F; Freitas, J; Puig, J; Freitas, A F



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

NASA Astrophysics Data System (ADS)

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

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



High gain ytterbium doped Ge pedestal large pitch fiber  

NASA Astrophysics Data System (ADS)

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

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



Spontaneous Activity, Economy of Activity, and Resistance to Diet-Induced Obesity in Rats Bred for High Intrinsic Aerobic Capacity  

PubMed Central

Though obesity is common, some people remain resistant to weight gain even in an obesogenic environment. The propensity to remain lean may be partly associated with high endurance capacity along with high spontaneous physical activity and the energy expenditure of activity, called non-exercise activity thermogenesis (NEAT). Previous studies have shown that high-capacity running rats (HCR) are lean compared to low-capacity runners (LCR), which are susceptible to cardiovascular disease and metabolic syndrome. Here, we examine the effect of diet on spontaneous activity and NEAT, as well as potential mechanisms underlying these traits, in rats selectively bred for high or low intrinsic aerobic endurance capacity. Compared to LCR, HCR were resistant to the sizeable increases in body mass and fat mass induced by a high-fat diet; HCR also had lower levels of circulating leptin. HCR were consistently more active than LCR, and had lower fuel economy of activity, regardless of diet. Nonetheless, both HCR and LCR showed a similar decrease in daily activity levels after high-fat feeding, as well as decreases in hypothalamic orexin-A content. The HCR were more sensitive to the NEAT-activating effects of intra-paraventricular orexin-A compared to LCR, especially after high-fat feeding. Lastly, levels of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in the skeletal muscle of HCR were consistently higher than LCR, and the high-fat diet decreased skeletal muscle PEPCK-C in both groups of rats. Differences in muscle PEPCK were not secondary to the differing amount of activity. This suggests the possibility that intrinsic differences in physical activity levels may originate at the level of the skeletal muscle, which could alter brain responsiveness to neuropeptides and other factors that regulate spontaneous daily activity and NEAT. PMID:20350549

Novak, Colleen M.; Escande, Carlos; Burghardt, Paul R.; Zhang, Minzhi; Barbosa, Maria Teresa; Chini, Eduardo N.; Britton, Steven L.; Koch, Lauren G.; Akil, Huda; Levine, James A.



High gain observer based synchronization for a class of time-delay chaotic systems. Application to  

E-print Network

High gain observer based synchronization for a class of time-delay chaotic systems. Application observer design to synchronize a time-delay chaotic system. It is shown that the underlying class. Index Terms--Chaos synchronization, high-gain observer, time- delay system I. INTRODUCTION If state

Boyer, Edmond


Signal output characteristics in a fiber optical parametric amplifier in high-gain-saturation region  

Microsoft Academic Search

This paper studies a fiber parametric amplifier in region of high gain saturation, and demonstrates, for the first time to the authors' knowledge, that optical power transfer from the signal and idler to the pump occurs at high signal input. Wavelength dependency is given special consideration, and it is shown that the signal gain saturates sooner on the farther wavelength

K. Inoue; T. Mukai



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

E-print Network

High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis H. Ouadi1 , F. Giri2 , L in induction motors is considered in this paper. In most previous works, motor observers have been designed significant load torque changes. In this paper, a high gain observer is designed for induction motors based

Paris-Sud XI, Université de


Photon detection with high gain avalanche photodiode arrays  

Microsoft Academic Search

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. We report on short wavelength sensitivity

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



A Combined High Gain Observer and High-Order Sliding Mode Controller for a DFIG-Based Wind  

E-print Network

A Combined High Gain Observer and High-Order Sliding Mode Controller for a DFIG-Based Wind Turbine optimization of a DFIG- based wind turbine. The proposed control strategy combines an MPPT using a high gain observer and second-order sliding mode for the DFIG control. This strategy presents attractive features

Paris-Sud XI, Université de


A new omnidirectional vertical polarization antenna with low profile and high gain  

Microsoft Academic Search

A new omnidirectional vertical polarization antenna array with low profile and high gain is presented. The antenna exhibits good radiation performance and the measured gain is more than 10dBi despite the miniaturized volume, which shows attractive future for HDTV on vehicles.

Junping Geng; Ronghong Jin; Zhiguo Wang; Zhihao Yuan; Jinliang Dong; Jiaqiang Li; Wei Wang; Wei He; Min Ding



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

E-print Network

is designed for high frequency and low power communication applications, such as an Ultra Wideband (UWB) receiver system. The gain can be programmed from 0dB to 42dB in 2dB increments with -3dB bandwidth greater than 425MHz for the entire range of gain. The 3...

Chen, Lin



High current gain 4H-SiC npn bipolar junction transistors  

Microsoft Academic Search

The authors report a common emitter current gain ? of 55 in npn epitaxial-emitter 4H-SiC bipolar junction transistors. The spacing between the p+ base contact implant and the edge of the emitter finger is critical in obtaining high-current gain. VCEO of these devices is 500 V, and VCBO is 700 V.

Chih-Fang Huang; James A. Cooper



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

Microsoft Academic Search

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

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



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

NASA Technical Reports Server (NTRS)

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

Lecha, Javier; Woods, Claudia; Phan, Minh



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

E-print Network

a hybrid quantum well/quantum dot laser structure Appl. Phys. Lett. 100, 041118 (2012) Time-dynamicsO/SnO nanocomposites AIP Advances 2, 012133 (2012) Ultra-broad spontaneous emission and modal gain spectrum from of high Al-content AlGaN quantum well lasers Jing Zhang, Hongping Zhao, and Nelson Tansu Citation: Appl

Gilchrist, James F.


High gain photoconductive semiconductor switch having tailored doping profile zones  


A photoconductive semiconductor switch with tailored doping profile zones beneath and extending laterally from the electrical contacts to the device. The zones are of sufficient depth and lateral extent to isolate the contacts from damage caused by the high current filaments that are created in the device when it is turned on. The zones may be formed by etching depressions into the substrate, then conducting epitaxial regrowth in the depressions with material of the desired doping profile. They may be formed by surface epitaxy. They may also be formed by deep diffusion processes. The zones act to reduce the energy density at the contacts by suppressing collective impact ionization and formation of filaments near the contact and by reducing current intensity at the contact through enhanced current spreading within the zones.

Baca, Albert G. (Albuquerque, NM); Loubriel, Guillermo M. (Albuquerque, NM); Mar, Alan (Albuquerque, NM); Zutavern, Fred J (Albuquerque, NM); Hjalmarson, Harold P. (Albuquerque, NM); Allerman, Andrew A. (Albuquerque, NM); Zipperian, Thomas E. (Edgewood, NM); O'Malley, Martin W. (Edgewood, NM); Helgeson, Wesley D. (Albuquerque, NM); Denison, Gary J. (Sandia Park, NM); Brown, Darwin J. (Albuquerque, NM); Sullivan, Charles T. (Albuquerque, NM); Hou, Hong Q. (Albuquerque, NM)



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

PubMed Central

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

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



High gain proportional rf control stability at TESLA cavities Elmar Vogel  

E-print Network

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


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...5051 of Public Law 100-203, Nuclear Waste Policy Amendments Act of...



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

Microsoft Academic Search

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

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



Gain Characteristics of Erbium-Doped Fiber Amplifiers with High Erbium Concentration  

Microsoft Academic Search

The gain characteristics of erbium-doped fiber amplifiers (EDFAs) with erbium concentrations as high as 8900 ppm have been investigated in detail with 0.98 mum and 1.48 mum pumping schemes. Although the emission cross section at 1.532 mum is 24% less than that with low erbium concentration as a result of concentration quenching, a gain as high as 24 dB was

Yasuo Kimura; Masataka Nakazawa



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

Microsoft Academic Search

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

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



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

NASA Astrophysics Data System (ADS)

We have developed and measured a high-gain quantum-limited microwave parametric amplifier based on a superconducting lumped LC resonator with the inductor L including an array of eight superconducting quantum interference devices (SQUIDs). This amplifier is parametrically pumped by modulating the flux threading the SQUIDs at twice the resonator frequency. Around 5 GHz, a maximum gain of 31 dB, a product amplitude gain × bandwidth above 60 MHz, and a 1 dB compression point of -123 dBm at 20 dB gain are obtained in the nondegenerate mode of operation. Phase-sensitive amplification-deamplification is also measured in the degenerate mode and yields a maximum gain of 37 dB. The compression point obtained is 18 dB above what would be obtained with a single SQUID of the same inductance, due to the smaller nonlinearity of the SQUID array.

Zhou, X.; Schmitt, V.; Bertet, P.; Vion, D.; Wustmann, W.; Shumeiko, V.; Esteve, D.



Energy gain of highly charged ions in front of LiF  

SciTech Connect

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

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



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



Target design for ignition and high gain in direct drive ICF  

Microsoft Academic Search

Present status of ignition and high-gain target design is presented. A simple scalings of target design by one-dimensional hydrodynamic code is shown in the range from 1 kJ to 10 MJ of driver energy. The sensitivity of the pellet gain is studied with a two-dimensional code and the Rayleigh-Taylor growth factor is evaluated. It is concluded that the mixing may

H Takabe; H Nagatomo; A Sunahara; N Ohnishi; S Kato; A. I Mahdy; H Azechi; K Mima



High-gain, low-intensity ICF targets for a charged-particle beam fusion driver  

Microsoft Academic Search

A class of high-gain ICF targets driven by electrons or light ions is discussed. The targets are characterized by a low-beam-intensity requirement and large size. A magnetic field provides thermal insulation of pre-heated, low-density fuel. The addition of a cryogenic fuel layer increases the gain without requiring significantly increased beam power and intensity. The higher fuel adiabat and reduced fuel

M. A. Sweeney; A. V. Farnsworth Jr.



High-Speed Switched-Capacitor Filters Based on Unity Gain Buffers David Bruneau1  

E-print Network

High-Speed Switched-Capacitor Filters Based on Unity Gain Buffers David Bruneau1 , Adrian Early2Systems Abstract- In this work a new voltage buffer, the drain-follower, achieves 300MHz bandwidth with 2pF load and 6.5mW power dissipation from 5V supply. A unity-gain buffer switched-capacitor biquad filter has

Moon, Un-Ku


3-D numerical analysis of a high-gain free-electron laser  

SciTech Connect

We present a novel approach to the 3-dimensional high-gain free- electron laser amplifier problem. The method allows us to write the laser field as an integral equation which can be efficiently and accurately evaluated on a small computer. The model is general enough to allow the inclusion of various initial electron beam distributions to study the gain reduction mechanism and its dependence on the physical parameters. 16 refs., 8 figs., 1 tab.

Gallardo, J.C.



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

Microsoft Academic Search

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

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



High gain erbium-doped fiber amplifier for the investigation of nonlinear processes in fibers  

Microsoft Academic Search

In this work we present a novel design of an optical amplifier with high gain elaborated from erbium-doped fiber (EDF). Its purpose is the amplification of low power pulses from laser diodes. The high power of the output pulses allows the investigation of nonlinear processes in optical fibers. The optical amplifier consists of two stages. The first stage uses a

S. Mendoza v; E. Kuzin; O. Pottiez



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

SciTech Connect

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

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




Microsoft Academic Search

We searched for high energy ?-particles emitted from spontaneous fission products of 252 Cf by the measurement of the high energy part of the ?-spectrum with a very low background ?E1-?E2-Et -scintillation spectrometer. It is found that ?-emissions in the energy region higher than 20 MeV exist with the relative probability of Y? = (4.5±0.6 stat.±1.2 syst.) x10 -9 ?\\/fission.

Yu. V. Ryabov


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

ERIC Educational Resources Information Center

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

Klasek, Catherine Huey



Experiments of high gain C VI x-ray lasing in rapidly recombining plasmas  

SciTech Connect

Recent experimental results of high gain C VI x-ray lasing in rapidly recombining plasmas are described. 7 {mu}m diameter carbon fiber targets of up to 5 mm length were irradiated at intensities between 3x10{sup 15}{approx}1x10{sup 16} W/cm{sup 2} by a 2 ps, 20 TW chirped pulse amplification (CPA) beam from the VULCAN Nd-glass laser ({lambda}=1.053 {mu}m) at RAL. The gain length product on the 18.2 nm Balmer {alpha} transition of C VI ions was measured to be 6.5{+-}1. The ratio of intensities of resonance lines of H-like and He-like ions in the rapidly recombining plasmas was used as a useful diagnostic of initial conditions for high gain operation of the C VI recombination x-ray lasing.

Zhang, J.; Key, M. H.; Norreys, P. A.; Tallents, G. J.; Behjat, A.; Danson, C.; Demir, A.; Dwivedi, L.; Holden, M.; Holden, P. B.; Lewis, C. L. S.; MacPhee, A. G.; Neely, D.; Pert, G. J.; Ramsden, S. A.; Rose, S. J.; Shao, Y. F.; Thomas, O.; Walsh, F.; You, Y. L. [Department of Atomic and Laser Physics, University of Oxford, Oxford, OX1 3PU (United Kingdom) and Department of Atomic and Laser Physics, University of Oxford, Oxford, OX1 3PU (United Kingdom) and Central Laser Facility, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Central Laser Facility, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom) and Department of Physics, University of Essex, Colchester, CO4 3SQ (United Kingdom) and Central Laser Facility, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom) and Department of Physics, University of Essex, Colchester, CO4 3SQ (United Kingdom); Department of Physics, University of York, York, YO1 5DD (United Kingdom); Department of Pure and Applied Physics, Queen's University, Belfast, BT7 1NN (United Kingdom); Central Laser Facility, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Department of Physics, University of York, York, YO1 5DD (United Kingdom); Central Laser Facility, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Institute of Applied Physics and Computational Mathematics (China); Central Laser Facility, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Institute of Nuclear Physics and Chemistry, Chengdu (China)



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

NASA Technical Reports Server (NTRS)

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

Ostroff, Aaron J.



A high-gain, high-output saturation power erbium-doped fiber amplifier pumped at 532 nm  

Microsoft Academic Search

An erbium-doped fiber amplifier with a high small-signal gain of 42 dB at the gain peak of 1536.4 nm, a pumping efficiency of 1.6 dB\\/mW, and an output saturation power of 10 dBm is obtained with a pump power of 60 mW at 532 nm using the second harmonic of a Nd:YAG laser as the pump source. These experimental results

M. M. Choy; C. Y. Chen; M. Andrejco; M. Saifi; C. Lin



Fabrication and assembly of high gain MEMS antennas for wireless communications  

Microsoft Academic Search

Polymer based fabrication and assembly processes for producing suspended antenna devices have been developed. Stacked high gain patch antenna devices have been assembled using millimeter thick micromachined SU8 polymer ring spacers. Thin polyimide substrates (125 mum) were used for supporting the radiating and parasitic patch elements. The SU8 based polymer rings were used to create air space between the patches

C. H. Wang; S. K. Pavuluri



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

SciTech Connect

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

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



Neural Computation 9, 971983 (1997) Physiological Gain Leads to High ISI Variability in  

E-print Network

Neural Computation 9, 971­983 (1997) Physiological Gain Leads to High ISI Variability in a, Abstract To understand the interspike interval (ISI) variability displayed by visual that have previously been proposed. When ISI's are dominated by post­spike recovery, 1= p N arguments hold

Columbia University


Conceptual design of a 10 MJ driver for a high gain Target Development Facility  

Microsoft Academic Search

Commercial application of inertial confinement fusion (ICF) will require inexpensive, high gain (>80) fusion targets. It is thought that the development of such targets will require a 5 to 10 year research effort utilizing a dedicated nuclear research facility with a driver capable of providing a 10 MJ, 300 to 1000 TW pulse of on-target energy. The ''Target Development Facility''



Conceptual design of a 6-10 MJ driver for a high gain Target Development Facility  

Microsoft Academic Search

Commercial application of inertial confinement fusion will require low yield (approx.200 to 500 MJ), high gain (greater than or equal to80) fusion targets. It is thought that the development of such targets will require a 5 to 10 year research program utilizing one or more dedicated nuclear facilities with drivers capable of delivering on-target pulses of 6 to 10 MJ



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

Microsoft Academic Search

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

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



The Physics of Advanced High-Gain Targets for Inertial Fusion Energy  

Microsoft Academic Search

In ca. 2011-2012, the National Ignition Facility is poised to demonstrate fusion ignition and gain in the laboratory for the first time. This key milestone in the development of inertial confinement fusion (ICF) can be expected to engender interest in the development of inertial fusion energy (IFE) and expanded efforts on a number of advanced targets that may achieve high

L. John Perkins



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

Microsoft Academic Search

Plasma formed in the immediate vicinity of a meteoroid as it descends through Earth's atmosphere enables high-gain radars such as those found at Kwajalein, Arecibo, and Jicamarca to detect ablating meteoroids. In the work presented here, we show that these head echo measurements preferentially detect more energetic meteoroids over less energetic ones and present a method of estimating the effects

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



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

E-print Network

Science, Northwestern University, Evanston, IL 60208 We present the near-infrared injection photodetectors in short wave infrared (SWIR) spectrum, particularly focusing at 1.55 m wavelength. Spanning a wide rangeLow Noise, High Gain Short-Wave Infrared Nano-Injection Photon Detectors with Low Jitter Omer

Mohseni, Hooman


A broadband and high-gain metamaterial microstrip antenna Le-Wei Li,1,a  

E-print Network

A broadband and high-gain metamaterial microstrip antenna Le-Wei Li,1,a Ya-Nan Li,2 Tat Soon Yeo,2 Juan R. Mosig,3 and Olivier J. F. Martin3 1 Institute of Electromagnetics, University of Electronic-patterned metamaterial concepts. Based on an ordinary patch antenna, the antenna has isolated triangle gaps and crossed

Floreano, Dario


Analytical treatment of the high-gain free electron laser equation  

Microsoft Academic Search

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

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



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



Plasmonic Amplification with Ultra-High Optical Gain at Room Temperature  

E-print Network

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

Wang, Wei Hua


Dynamic Receptor Team Formation Can Explain the High Signal Transduction Gain in Escherichia coli  

E-print Network

Dynamic Receptor Team Formation Can Explain the High Signal Transduction Gain in Escherichia coli in the peritrichous bacterium Escherichia coli, which has four helical flagella distributed over the cell surface explain this observation. INTRODUCTION Escherichia coli has five receptor types, but most is known about

Othmer, Hans


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

NASA Technical Reports Server (NTRS)

This paper describes a variable-gain optimal discrete output-feedback design approach that is applied to a nonlinear flight regime covering a wide angle-of-attack range that includes stall and poststall. The paper includes brief descriptions of the variable-gain formulation, the discrete-control structure and flight equations used to apply the design approach, and the high performance airplane model used in the application. Both linear and nonlinear analyses are shown for a longitudinal four-model design case with angles of attack of 5, 15, 35, and 60 deg.

Ostroff, Aaron J.



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


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

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



High-gain on-chip antenna using a sapphire substrate for implantable wireless medical systems  

NASA Astrophysics Data System (ADS)

This paper presents a high-gain on-chip antenna using a sapphire substrate for implantable wireless medical systems. The antenna model is based on a dipole and the antenna elements are appropriately rolled for impedance matching. The center frequency of the fabricated on-chip antenna was measured as 360 MHz. The return loss was -3.58 dB and the input impedance was 190.5 - j74.7 ? at 360 MHz. The maximum antenna gain of the fabricated on-chip antenna was -29.2 dBi. The on-chip antenna using a sapphire substrate achieved a 12.9 dB higher gain than that using a silicon substrate and successfully induced signal transmission at a distance of 10 cm with a transmitter chip. The implemented on-chip antenna can improve the power efficiency of implantable wireless medical systems by 95%.

Okabe, Kenji; Akita, Ippei; Ishida, Makoto



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)



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

SciTech Connect

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

OHara, David



Geometrical effects in high current gain 1100-V 4H-SiC BJTs  

Microsoft Academic Search

This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain ?=64 and a breakdown voltage of 1100 V. The high ? value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The BJTs show a clear emitter-size effect indicating that surface recombination has a significant influence

M. Domeij; H.-S. Lee; E. Danielsson; C.-M. Zetterling; M. Ostling; A. Schoner



The Physics of Advanced High-Gain Targets for Inertial Fusion Energy  

NASA Astrophysics Data System (ADS)

In ca. 2011-2012, the National Ignition Facility is poised to demonstrate fusion ignition and gain in the laboratory for the first time. This key milestone in the development of inertial confinement fusion (ICF) can be expected to engender interest in the development of inertial fusion energy (IFE) and expanded efforts on a number of advanced targets that may achieve high fusion energy gain at lower driver energies. In this tutorial talk, we will discuss the physics underlying ICF ignition and thermonuclear burn, examine the requirements for high gain, and outline candidate R&D programs that will be required to assess the performance of these target concepts under various driver systems including lasers, heavy-ions and pulsed power. Such target concepts include those operating by fast ignition, shock ignition, impact ignition, dual-density, magnetically-insulated, one- and two-sided drive, etc., some of which may have potential to burn advanced, non-DT fusion fuels. We will then delineate the role of such targets in their application to the production of high average fusion power. Here, systems studies of IFE economics suggest that we should strive for target fusion gains of around 100 at drive energies of 1MJ, together with corresponding rep-rates of up to 10Hz and driver electrical efficiencies around 15%. In future years, there may be exciting opportunities to study such ``innovative confinement concepts'' with prospects of fielding them on facilities such as NIF to obtain high fusion energy gains on a single shot basis.

Perkins, L. John



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

E-print Network

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

Brest, Université de


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)



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



Investigations of SBS and laser gain competition in high-power phase modulated fiber amplifiers  

NASA Astrophysics Data System (ADS)

We present experimental results of SBS suppression in high power, monolithic, Yb-doped fiber amplifiers via phase modulated laser gain competition. To narrow the linewidth, two-tone laser gain competition between broad (1036 nm) and narrow linewidth (1064 nm) laser signals is investigated in conjunction with phase modulation and yields pump limited output powers of 600 W. Here integration of both two-tone and pseudo random bit sequence (PRBS) phase modulation concepts, generated SBS enhancement factors of greater than 17x at a modulation frequency of 500 MHz, without reaching the SBS threshold. Significantly, the results represent a near order of magnitude reduction in linewidth over current high-power, monolithic, Yb-doped fiber amplifiers.

Flores, Angel; Dajani, Iyad; Hult, Dane; Robin, Craig



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

NASA Astrophysics Data System (ADS)

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

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



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.



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 iotan(q/q/sub o/)/(q/q/sub o/), where (q/q/sub o/) 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.



High gain dual-band antenna using photovoltaic panel as metamaterial superstrate  

Microsoft Academic Search

A novel planar dual-band antenna by using a panel of photovoltaic cells as a metamaterial layer for dual-band operation is presented. A 10-Watt, 72-cell unmodified commercial photovoltaic panel is applied as a transparent layer in the first operation band and as a semi-transparent layer for ??? 2 Fabry-Pérot cavity in the second operation band to achieve high antenna gain. Unit-cell

Chun-Yih Wu; Hung-Hsuan Lin; Ta-Chun Pu; Jui-Hung Chen



Decentralized nonlinear adaptive control for multimachine power systems via high-gain perturbation observer  

Microsoft Academic Search

This paper presents two novel decentralized nonlinear adaptive controllers (DNAC) for large-scale interconnected power systems, via state-feedback and output-feedback strategies respectively. In the both controllers, system perturbation, which includes all subsystem nonlinearities and interactions between subsystems, is estimated by a high-gain observer and then involved the decentralized adaptive feedback linearizing control law. For the first DNAC, when all subsystem states

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



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

Microsoft Academic Search

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

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



Marker Polypeptides Distinguishing between Cancer Cell Clones with High and Low Potential for Spontaneous Metastasis in Murine Fibrosarcoma Cells1  

Microsoft Academic Search

Consistent differences in expression of specific proteins were observed between numerous cancer cell clones with high and low potential for spontaneous metastasis. Seventeen clones from two unrelated murine fibrosareomas were examined concomitantly for spontaneous formation of lung métastasesand for occurrence of individual polypeptide differ ences by high resolution two-dimensional gel electrophoresis. One of the identified marker polypeptides, designated Hi:2, was

Ivar Amund Grimstad; Anne Karine Thorsrud; Egil Jellum



Spontaneous High Piezoelectricity in Poly(vinylidene fluoride) Nanoribbons Produced by Iterative Thermal Size Reduction Technique.  


We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar ? phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar ? phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 ?A peak short-circuit current output. PMID:25133594

Kanik, Mehmet; Aktas, Ozan; Sen, Huseyin Sener; Durgun, Engin; Bayindir, Mehmet



Stability requirement FOT ignition and high gain implosion = 2-D simulation for high neutron yield experiment =  

Microsoft Academic Search

Implosion stability is the essential problem for Inertial Confinement Fusion (ICF) scenario, in which ignition by use of a 100 kJ class driver will be demonstrated and the pellet gain 100 will be realized with MJ class driver. In order to study the stability requirement, a two dimensional fluid code, ILESTA-2D was developed. Preliminary results obtained by using the 2-D

H. Takabe



High Adherence Is Necessary to Realize Health Gains from Water Quality Interventions  

PubMed Central

Background Safe drinking water is critical for health. Household water treatment (HWT) has been recommended for improving access to potable water where existing sources are unsafe. Reports of low adherence to HWT may limit the usefulness of this approach, however. Methods and Findings We constructed a quantitative microbial risk model to predict gains in health attributable to water quality interventions based on a range of assumptions about pre-treatment water quality; treatment effectiveness in reducing bacteria, viruses, and protozoan parasites; adherence to treatment interventions; volume of water consumed per person per day; and other variables. According to mean estimates, greater than 500 DALYs may be averted per 100,000 person-years with increased access to safe water, assuming moderately poor pre-treatment water quality that is a source of risk and high treatment adherence (>90% of water consumed is treated). A decline in adherence from 100% to 90% reduces predicted health gains by up to 96%, with sharpest declines when pre-treatment water quality is of higher risk. Conclusions Results suggest that high adherence is essential in order to realize potential health gains from HWT. PMID:22586491

Brown, Joe; Clasen, Thomas



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


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



Effects of Bandwidth, Compression Speed, and Gain at High Frequencies on Preferences for Amplified Music  

PubMed Central

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



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


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

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



High-gain 1310 nm semiconductor optical amplifier modules with a built-in amplified signal monitor for optical gain control  

Microsoft Academic Search

A compact high-gain 1310-nm semiconductor optical amplifier (SOA) module incorporating two photodiodes to detect radiation emitted from the two opposite facets of the amplifier chip is reported. By subtracting their signals, a measure of the amplified signal is obtained without the need for optical filtering, Using this, amplified signals can be stabilized within 0.5 dB over a 25-dB range of

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



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)



Pulse compression using angular multiplexing in a high-gain 1.7 kJ amplifier  

NASA Astrophysics Data System (ADS)

Pulse compression using angular multiplexing is demonstrated on a large-scale hydrogen-fluoride laser system. For a train of two 24 ns pulses, the essential elements of this scheme are evaluated as a function of interpulse separation time. Included are energy-extraction efficiency, overall temporal pulse distortion, leading-edge contrast-ratio distortion, and suppression of amplified spontaneous emission relative to a single long-duration input pulse. For appropriate interpulse delay time, it is shown that distortionless amplification is possible with energy-extraction efficiency, as is obtained using a single input beam having a pulsewidth equal to the duration of the amplifier gain.

Hays, G. N.; Hoffman, J. M.



A K-Band High-Gain Down-Conversion Mixer in 0.18 m CMOS Technology  

Microsoft Academic Search

A high gain CMOS down conversion mixer with a gain enhancement technique is presented. This technique includes negative resistance generation, parasitic capacitance cancellation and current-injection. These are implemented with an additional circuitry. This mixer has a conversion gain of 9.12 dB, input 1 dB compression point of -11 dBm at 24 GHz, while consuming 16.2 mW from 1.8 V supply.

Dukju Ahn; Dong-Wook Kim; Songcheol Hong



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.



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



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.



High perceptual load leads to both reduced gain and broader orientation tuning  

PubMed Central

Due to its limited capacity, visual perception depends on the allocation of attention. The resultant phenomena of inattentional blindness, accompanied by reduced sensory visual cortex response to unattended stimuli in conditions of high perceptual load in the attended task, are now well established (Lavie, 2005; Lavie, 2010, for reviews). However, the underlying mechanisms for these effects remain to be elucidated. Specifically, is reduced perceptual processing under high perceptual load a result of reduced sensory signal gain, broader tuning, or both? We examined this question with psychophysical measures of orientation tuning under different levels of perceptual load in the task performed. Our results show that increased perceptual load leads to both reduced sensory signal and broadening of tuning. These results clarify the effects of attention on elementary visual perception and suggest that high perceptual load is critical for attentional effects on sensory tuning. PMID:24610952

Stolte, Moritz; Bahrami, Bahador; Lavie, Nilli



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


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



A high gain, high output saturation power Pr3+-doped fluoride fiber amplifier operating at 1.3 mu m  

Microsoft Academic Search

A high net gain of 30.1 dB at 1.309 mu m and an output saturation of 13 dBm are obtained using a Pr3+-doped fluoride fiber amplifier pumped at 1.017 mu m. The critical Pr3+ concentration at which concentration quenching begins to occur was obtained by fluorescence lifetime measurement. The Pr3+ concentration should be less than 1000 ppm to suppress the

Yasutake Ohishi; Terutoshi Kanamori; Toshihiro Nishi; Shiro Takahashi



Chorus waves: a high-gain free-electron laser in the Earth's magnetosphere  

NASA Astrophysics Data System (ADS)

Chorus waves in the magnetosphere are very-low-frequency (VLF) phenomena that arise due to the interaction of gyro-resonant electrons with whistler waves. These waves typically have frequencies equal to half the electron gyro-frequency at the geomagnetic equator, are amplified to amplitudes of more than 30dB, and exhibit a continuous frequency chirp. The study of these waves, and their role in energizing particles, is one of the principal objectives of the upcoming Radiation Belt Storm Probes (RBSP) mission. Here we present a new model of chorus waves based on the high-gain free-electron laser mechanism. We derive a new closed set of self-consistent relativistic equations that couple the Hamiltonian single-particle equations with Maxwell's equations for the radiation field, assuming that the latter is slowly varying. We demonstrate, neglecting slippage between the electrons and the radiation field, that in the exponential high-gain regime, these differential equations yield an exact cubic algebraic equation that predicts whistler wave amplification levels in good agreement with observations. When slippage is included in the theory, the radiation field phase evolves in time, predicting a frequency chirp.

Bhattacharjee, A.; Soto-Chavez, R.



Recent progress in high-gain, high-output-power praseodymium-doped fluoride fiber amplifiers for the 1.3-um spectral region  

Microsoft Academic Search

This paper describes recent progress at BTLabs in high gain high output power praseodymium doped fluoride fiber amplifiers around 1.3 micrometers . Firstly, results using Ti:sapphire pumping will be described; using a high numerical aperture fiber, a net gain of 15 dB was achieved for 200 mW pump power, with a maximum small signal net gain of 29.5 dB. When

Richard R. Wyatt; Tim J. Whitley; Steven T. Davey; Daryl Szebesta



Some observations on spin detector response during Galileo high gain antenna deployment  

NASA Technical Reports Server (NTRS)

This paper summarizes a dynamic analysis conducted in support of the investigation of the anomalous deployment of the Galileo High Gain Antenna on April 11, 1991. The work was focused on modeling the spacecraft spin dynamics to predict and compare the spin detector telemetry during the antenna deployment for possible cause scenarios. The effects of analog and digital low-pass filtering, digitization, and telemetry on the reported spin rate were studied as well. The high frequency phenomena in the spin detector response are masked by the filtering and sampling of the telemetry data. However, the observed spin detector telemetery is consistent with a single rib popping free, and is most likely associated with a rib near the spin detector, or 180 deg opposite.

Peng, Chia-Yen; Smith, Kenneth S.



Spontaneous airways constrict during breath holding studied by high-resolution computed tomography.  


Airway constriction during a breath hold could not be examined previously using standard methods. We used high-resolution computed tomography (HRCT) in vivo to assess the temporal changes in airway area and the effects of a deep inspiration with and without vagal suppression. Five dogs were anesthetized, intubated, and their lungs ventilated with 100 percent oxygen. Fifteen HRCT slices were obtained at functional residual capacity (FRC) either immediately after stopping ventilation at end expiration after either a tidal volume breath or three deep inspirations. Subsequently the dogs were given atropine, 0.2 mg/kg, and the scans were repeated. The cross-sectional areas of 33 airways ranging in size from 1.6 to 9.7 mm in diameter were measured. Airways were separated in three groups based on size: small (< 3 mm in diameter); medium (3 to 6-mm in diameter); and large (> 6 mm in diameter). The small, medium, and large airways showed a spontaneous constriction over time to 49 +/- 8 percent, 83 +/- 4 percent, and 82 +/- 4 percent of initial airway size, respectively (p < 0.01), (p < 0.0001). The deep inspiration caused an initial dilation only in the smallest airways to 133.3 +/- 4 percent. The subsequent constrictions were even greater than after the tidal volume breath averaging 67 +/- 15 percent, 61 +/- 6 percent, and 60 +/- 9 percent of initial airway area in the small, medium, and large airways, respectively (p = 0.001). Atropine caused an average increase in baseline airway area of 115 +/- 5 percent and 121 +/- 6 percent after a tidal volume breath and deep inspiration, respectively, compared with the preatropine controls, with no difference between the three groups. Atropine also completely abolished the spontaneous airway constriction observed after either a tidal volume breath or a deep inspiration in all three groups equally. In conclusion, using direct airway imaging in vivo, we found that airways spontaneously constrict during a prolonged expiratory pause, and a deep inspiration significantly augments this airway constriction. These responses are mediated via vagal afferent pathways, likely arising from progressively decreasing slow-adapting receptor activity. PMID:8082378

Brown, R H; Herold, C; Zerhouni, E A; Mitzner, W



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



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

NASA Astrophysics Data System (ADS)

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

Zhigadlo, N. D.



Nanoparticle-assisted high photoconductive gain in polymer/fullerene matrix  

PubMed Central

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

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



An implanted-emitter 4H-SiC bipolar transistor with high current gain  

Microsoft Academic Search

An epi-base, implanted-emitter, npn bipolar transistor which showed a maximum common emitter current gain (?) of ~40, the highest current gain reported for BJT in any polytype of SiC has been experimentally demonstrated in 4H-SiC. The forward drop was ~1 V at forward current density of 50 A\\/cm2. The current gain decreases hence specific on-resistance increases with increasing temperature. The

Yi Tang; Jefferey B. Fedison; T. Paul Chow



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



A high gain GRIN-SCH MQW optical semiconductor laser amplifier  

Microsoft Academic Search

A description is presented of the fabrication of a multiple-quantum-well GRIN-SCH traveling-wave-type amplifier combined with a tapered waveguide and a window region to reduce optical reflection at both end facets. Optical fiber-to-fiber gain of 10.4 dB (signal gain of 24.4 dB) under gain variation of 100 nm and gain variation was <1.0 dB. The saturation output power was 13.5 dBm.




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.



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

NSDL National Science Digital Library

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

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



Characterization of phototransistor internal gain in metamorphic high-electron-mobility transistors  

E-print Network

the mHEMT operates as a phototransistor, it has internal gain provided by the photovoltaic effect. To determine this internal gain, photoresponse characteristics dominated by the photoconductive effect as well as the photovoltaic effect are investigated. When the device is turned off, it acts as a photoconductor

Choi, Woo-Young


Optical Amplifier with Flat-Gain and Wideband Operation Utilizing Highly Concentrated Erbium-Doped Fibers  

NASA Astrophysics Data System (ADS)

In this paper, we proposed a flat-gain and wide-band erbium doped fiber amplifier (EDFA) using two chirped fiber Bragg grating (CFBG) in serial configuration for double-pass operation. The amplifier consists of two sections of Erbium-doped fiber (EDF) operating in C-band and L-band respectively. A CFBG is used in each section to reflect the amplified signal back to the active area so that the overall gain spectrum can be enhanced and flattened. It is also observed that the gain of the amplifier produces a relatively higher gain with the Bismuth-based EDF (Bi-EDF) in the first stage compared to that of silica-based EDF (Si-EDF), especially in a longer wavelength region. The small signal gain of more than 19 dB is obtained within a wavelength region from 1545 to 1605 nm by the use of Bi-EDF with a small noise figure penalty. With a Si-EDF, the flat gain spectrum is observed within a wavelength region ranging from 1535 nm to 1605 nm with a gain variation of less than 2 dB at input signal of 0 dBm. This shows that the proposed serial double-pass amplifier may find its broad applications in wavelength division multiplexing long-haul systems as well as local optical networks.

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


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



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

NASA Technical Reports Server (NTRS)

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

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



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

NASA Astrophysics Data System (ADS)

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

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



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

NASA Astrophysics Data System (ADS)

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

Henestroza, Enrique; Grant Logan, B.



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

NASA Astrophysics Data System (ADS)

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

Newburgh, G. A.; Dubinskii, Mark



Lower-power, high-linearity class-AB current-mode programmable gain amplifier  

NASA Astrophysics Data System (ADS)

A novel class-AB implementation of a current-mode programmable gain amplifier (CPGA) including a current-mode DC offset cancellation loop is presented. The proposed CPGA is based on a current amplifier and provides a current gain in a range of 40 dB with a 1 dB step. The CPGA is characterized by a wide range of current gain variation, a lower power dissipation, and a small chip size. The proposed circuit is fabricated using a 0.18 ?m CMOS technology. The CPGA draws a current of less than 2.52 mA from a 1.8 V supply while occupying an active area of 0.099 ?m2. The measured results show an overall gain variation from 10 to 50 dB with a gain error of less than 0.40 dB. The OP1dB varies from 11.80 to 13.71 dBm, and the 3 dB bandwidth varies from 22.2 to 34.7 MHz over the whole gain range.

Yiqiang, Wu; Zhigong, Wang; Junliang, Wang; Li, Ma; Jian, Xu; Lu, Tang



Observation of spectral gain narrowing in a high-order harmonic seeded soft-x-ray amplifier  

SciTech Connect

We report an observation of spectral gain narrowing of a high-order harmonic amplified by a soft-x-ray optical-field-ionized plasma. The temporal coherence and spectral linewidth of both the seeded and unseeded soft-x-ray lasers were experimentally measured using a varying-path-difference interferometer. The results showed that the high-order harmonic is subject to a strong spectral narrowing during its propagation in the plasma amplifier without rebroadening at saturation. This is in good agreement with a radiative transfer calculation including gain narrowing and saturation rebroadening.

Tissandier, F.; Sebban, S.; Ribiere, M.; Gautier, J.; Zeitoun, Ph.; Lambert, G.; Barszczak Sardinha, A.; Goddet, J.-Ph.; Burgy, F.; Lefrou, T.; Valentin, C.; Rousse, A.; Guilbaud, O.; Klisnick, A.; Nejdl, J.; Mocek, T.; Maynard, G. [Laboratoire d'Optique Appliquee, ENSTA Paristech/Ecole Polytechnique/CNRS UMR 7639, F-91761 Palaiseau Cedex (France); Laboratoire d'Interaction du Rayonnement X Avec la Matiere, Universite Paris Sud/CNRS UMR 8624, F-91495 Orsay Cedex (France); Department of X-ray Lasers, Institute of Physics, Na Slovance 2, CZ-182 21 Prague 8 (Czech Republic); Laboratoire de Physique des Gaz et des Plasmas, Universite Paris Sud/CNRS UMR 8578, F-91405 Orsay Cedex (France)



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.



Interval Mapping of High Growth (Hg), a Major Locus That Increases Weight Gain in Mice  

PubMed Central

The high growth locus (hg) causes a major increase in weight gain and body size in mice. As a first step to map-based cloning of hg, we developed a genetic map of the hg-containing region using interval mapping of 403 F(2) from a C57BL/6J-hghg X CAST/EiJ cross. The maximum likelihood position of hg was at the chromosome 10 marker D10Mit41 (LOD = 24.8) in the F(2) females and 1.5 cM distal to D10Mit41 (LOD = 9.56) in the F(2) males with corresponding LOD 2 support intervals of 3.7 and 5.4 cM, respectively. The peak LOD scores were significantly higher than the estimated empirical threshold LOD values. The localization of hg by interval mapping was supported by a test cross of F(2) mice recombinant between the LOD 2 support interval and the flanking marker. The interval mapping and test-cross results indicate that hg is not allelic with candidate genes Igf1 or decorin (Dcn), a gene that was mapped close to hg in this study. The hg inheritance was recessive in females, although we could not reject recessive or additive inheritance in males. Possible causes for sex differences in peak LOD scores and for the distortion of transmission ratios observed in F(2) males are discussed. The genetic map of the hg region will facilitate further fine mapping and cloning of hg, and allow searches for a homologous quantitative trait locus affecting growth in humans and domestic animals. PMID:7789774

Horvat, S.; Medrano, J. F.



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

NASA Technical Reports Server (NTRS)

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

Bourkland, Kristin L.; Liu, Kuo-Chia



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

PubMed Central

Here we present synthesis and electronic properties of a new alternating copolymer composed of dithieno[2,3-d;2?,3?-d?]benzo[1,2-b;4,5-b?]dithiophene (DTBDT) and diketopyrrolopyrrole units, poly dithienobenzodithiophene-co-diketopyrrolopyrrolebithiophene (PDPDBD). The resulting polymer showed hysteresis free, fast switching and highly reliable organic thin-film transistor properties comparable to a-Si. Hole mobility of the polymer is about 2.7?cm2V?1s?1, which is remarkably improved compared with its benzodithiophene (BDT)-analougue that contains a smaller aromatic ring of BDT in the place of DTBDT. This is mainly due to much increased intramolecular charge transport originated from PDPDBD's rigid molecular backbone. Furthermore, photoconductor devices fabricated by using PDPDBD as an active layer showed a high performance with the highest photoconductive gain of ~105. Taken together, the successful PDPDBD's transistor and photoconductor performances with high device stability demonstrated practical applicability of PDPDBD in low-cost and flexible optoelectronic devices. PMID:24970637

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



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

NASA Astrophysics Data System (ADS)

Here we present synthesis and electronic properties of a new alternating copolymer composed of dithieno[2,3-d2',3'-d']benzo[1,2-b4,5-b']dithiophene (DTBDT) and diketopyrrolopyrrole units, poly dithienobenzodithiophene-co-diketopyrrolopyrrolebithiophene (PDPDBD). The resulting polymer showed hysteresis free, fast switching and highly reliable organic thin-film transistor properties comparable to a-Si. Hole mobility of the polymer is about 2.7 cm2V-1s-1, which is remarkably improved compared with its benzodithiophene (BDT)-analougue that contains a smaller aromatic ring of BDT in the place of DTBDT. This is mainly due to much increased intramolecular charge transport originated from PDPDBD's rigid molecular backbone. Furthermore, photoconductor devices fabricated by using PDPDBD as an active layer showed a high performance with the highest photoconductive gain of ~105. Taken together, the successful PDPDBD's transistor and photoconductor performances with high device stability demonstrated practical applicability of PDPDBD in low-cost and flexible optoelectronic devices.

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



Investigation Into the Effects of the Patch-Type FSS Superstrate on the High-Gain Cavity Resonance Antenna Design  

Microsoft Academic Search

Results of modeling, design, simulation and fabrication are presented for a high-gain cavity resonance antenna (CRA), employing highly-reflective patch-type superstrates. In order to determine the resonant conditions, the antenna is first analyzed using the transverse equivalent network (TEN) model, as well as the well known simple ray-tracing method. Prior to that, a highly-reflective patch-type frequency selective surface (FSS) is designed

Alireza Foroozesh; Lotfollah Shafai



Clinical results and radiographical evaluation of opening wedge high tibial osteotomy for spontaneous osteonecrosis of the knee  

Microsoft Academic Search

We evaluated the clinical outcomes, in terms of early weight bearing, of using opening wedge high tibial osteotomy (OWHTO)\\u000a to treat spontaneous osteonecrosis of the medial femoral condyle of the knee (SONK) using TomoFix™ and artificial bone substitute.\\u000a Damaged cartilage tissue was removed and drilling of the necrotic area followed by OWHTO was performed in 30 knees from 30\\u000a patients

Ryohei Takeuchi; Masato Aratake; Haruhiko Bito; Izumi Saito; Ken Kumagai; Riku Hayashi; Yohei Sasaki; Yasuhsi Akamatsu; Hiroyuki Ishikawa; Eishyun Amakado; Yoichi Aota; Tomoyuki Saito



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

Microsoft Academic Search

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

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



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.



Realising high-current gain p-n-p transistors using a novel surface accumulation layer transistor  

E-print Network

Realising high-current gain p-n-p transistors using a novel surface accumulation layer transistor accumulation layer transistor (SALTran) on SOI, which uses the concept of surface accumulation of holes near of the previously published conventional p-n-p lateral bipolar transistor (LBT) structure. From the simulation

Kumar, M. Jagadesh


High gain\\/broadband oxide glasses for next generation Raman amplifiers  

Microsoft Academic Search

Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are

Clara A. Rivero



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

Microsoft Academic Search

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

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



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

Microsoft Academic Search

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

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



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



Inflight calibration technique for onboard high-gain antenna pointing. [of Mariner 10 spacecraft in Venus and Mercury flyby mission  

NASA Technical Reports Server (NTRS)

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 the performance of HGA pointing during the critical period of Mercury encounter.

Ohtakay, H.; Hardman, J. M.



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

NASA Technical Reports Server (NTRS)

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

Bourkland, Kristin L.; Liu, Kuo-Chia



Integrated calculation of a high gain target for NIF with burn through foils  

NASA Astrophysics Data System (ADS)

Burn-through foils have been proposed as a technique to reduce the asymmetry of the radiation incident on the implosion capsule. This technique is currently being explored for ICF targets driven by heavy ion beams or Z-pinches. This work applies this technique to laser-driven designs. We begin with an earlier design of Suter that produced gain near 40 for 2.3 MJ of laser light. A more optimum 1-D implosion design( a scale of the base design for heavy ion fusion) leads to approximately a doubled gain from the coupled energy. However, in integrated designs this design fails due to a large P4. A burn-through foil is designed to remedy this problem. Generalization of this scheme to more complicated radiation asymmetries will also be discussed.

Tabak, Max



Single-mode optical fiber coupling of high-power tapered gain region devices  

Microsoft Academic Search

A simple method for collimating the optical output of a tapered gain region amplifier or laser and coupling to a single-mode optical fiber is described, along with a technique for quantitatively assessing the expected coupling efficiency. By using a tapered laser, 840 mW at 980 nm was coupled into single-mode fiber with 44% efficiency measured from fiber input to available

J. C. Livas; S. R. Chinn; E. S. Kintzer; J. N. Walpole; C. A. Wang; L. J. Missaggia



Single-mode optical fiber coupling of high-power tapered gain region devices  

Microsoft Academic Search

A simple method for collimating the optical output of a tapered gain region amplifier or laser and coupling to a single-mode optical fiber is described, along with a technique for quantitatively assessing the expected coupling efficiency. By using a tapered laser, 840 mW at 980 mm was coupled into single-mode fiber with 44% efficiency measured from fiber input to available

J. C. Livas; S. R. Chinn; E. S. Kintzer; J. N. Walpole; C. A. Wang; L. J. Missaggia



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



93-133 GHz Band InP High-Electron-Mobility Transistor Amplifier with Gain-Enhanced Topology  

NASA Astrophysics Data System (ADS)

In this study, we developed a new type of high-frequency amplifier topology using 75-nm-gate-length InP-based high-electron-mobility transistors (InP HEMTs). To enhance the gain for a wide frequency range, a common-source common-gate hybrid amplifier topology was proposed. A transformer-based balun placed at the input of the amplifier generates differential signals, which are fed to the gate and source terminals of the transistor. The amplified signal is outputted at the drain node. The simulation results show that the hybrid topology exhibits a higher gain from 90 to 140 GHz than that of the conventional common-source or common-gate amplifier. The two-stage amplifier fabricated using the topology exhibits a small signal gain of 12 dB and a 3-dB bandwidth of 40 GHz (93-133 GHz), which is the largest bandwidth and the second highest gain reported among those of published 120-GHz-band amplifiers. In addition, the measured noise figure was 5 dB from 90 to 100 GHz.

Sato, Masaru; Shiba, Shoichi; Matsumura, Hiroshi; Takahashi, Tsuyoshi; Nakasha, Yasuhiro; Suzuki, Toshihide; Hara, Naoki



No effect of high fat diet-induced obesity on spontaneous reporter gene mutations in gpt delta mice.  


A large number of epidemiological studies have demonstrated that obesity is a risk factor for several human cancers. Several animal studies using rodents with diet-induced or genetic obesity have also demonstrated that obesity can promote tumor development. However, the effects of obesity on the early stages of carcinogenesis, and especially on the spontaneous occurrence of somatic gene mutations, remain unclear. To investigate the effects of obesity on the rate of spontaneous gene mutations, we performed reporter gene mutation assays in liver, kidney, and colon, organs in which obesity appears to be associated with cancer development on the basis of epidemiological or animal studies, in mice with high fat diet (HFD)-induced obesity. Six-week-old male and female C57BL/6 gpt delta mice were fed HFD or standard diet (STD) for 13 or 26 weeks. At the end of the experiments, reporter gene mutation assays of liver, kidney, and colon were performed. Final body weights and serum leptin levels of male and female mice fed HFD for 13 or 26 weeks were significantly increased compared with corresponding STD-fed groups. Reporter gene mutation assays of liver, kidney, and colon revealed that there were no significant differences in gpt or Spi- mutant frequencies between STD- and HFD-fed mice in either the 13-week or 26-week groups. These results indicate that HFD treatment and consequent obesity does not appear to influence the spontaneous occurrence of somatic gene mutations. PMID:25227805

Takasu, Shinji; Ishii, Yuji; Matsushita, Kohei; Kuroda, Ken; Kijima, Aki; Kodama, Yukio; Ogawa, Kumiko; Umemura, Takashi



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

NASA Astrophysics Data System (ADS)

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

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



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

NASA Astrophysics Data System (ADS)

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

Li, Fangxin; Helmy, Amr S.



Single-mode optical fiber coupling of high-power tapered gain region devices  

NASA Astrophysics Data System (ADS)

A simple method for collimating the optical output of a tapered gain region amplifier or laser and coupling to a single-mode optical fiber is described, along with a technique for quantitatively assessing the expected coupling efficiency. By using a tapered laser, 840 mW at 980 nm was coupled into single-mode fiber with 44% efficiency measured from fiber input to available internal fiber power, in excellent agreement with the 48% predicted. When transmission losses of the collimating optics are included, the power coupling efficiency referred to the laser facet power is 32%.

Livas, J. C.; Chinn, S. R.; Kintzer, E. S.; Walpole, J. N.; Wang, C. A.; Missaggia, L. J.



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.



Operation of proportional counters under high gas gain, high working gas pressure in mixed field of radiation  

NASA Astrophysics Data System (ADS)

It was noted that gas gain depends on type of detected radiation and for beta particle is higher by 6-8 % than for X-ray . Over some value of current flowing through the counter (IC-critical current) the reduction in gas gain due to space charge defined by the time of evacuation of positive ions is observed. The value of IC for different counter geometries and different mixture pressures was measured. It limits the rate capability of the detector for fixed gas gain. Over some value of gas gain (AC-critical value of gas gain) non-proportionality due to self inducted space charge effect is observed. The value of AC was measured as a function of working gas pressure for different counter geometries. Measurements were made for gas compositions Ar+20% CO2 and Ar+6.4% CO2+2.5% N2, for mixture pressures from 0.05 to 0.65 MPa and for different counter geometries.

Koperny, Stefan; Kowalski, Tadeusz Z.



High-Current-Gain Direct-Growth GaN\\/InGaN Double Heterojunction Bipolar Transistors  

Microsoft Academic Search

We report high-current-gain n-p-n GaN\\/InGaN double-heterojunction bipolar transistors (DHBTs) using a direct-growth fabrication processing approach. The impact of the indium composition in the base layer was studied, and a burn-in effect using a constant-base-current stressing method was observed. We found that DHBTs with higher indium composition in the InGaN base layer may help reduce the base resistance and lower the

Yi-Che Lee; Yun Zhang; Hee-Jin Kim; Suk Choi; Zachary Lochner; Russell D. Dupuis; Jae-Hyun Ryou; Shyh-Chiang Shen



Transient analysis of short, high-concentration, gain-clamped Er3+Yb3+ codoped fiber amplifiers  

Microsoft Academic Search

A theoretical study of the dynamics of short high-concentration gain-clamped Er3+-Yb3+ codoped fiber amplifiers is presented. The effect of various parameters on the transient power excursions and relaxation oscillation frequency of a given signal input channel when other signal channels are added or dropped from an initial steady-state configuration is analyzed. In particular, the effects of Er3+ clustering, Yb3+ concentration,

Eldad Yahel; Ortwin Hess; Amos A. Hardy



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



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.



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

NASA Astrophysics Data System (ADS)

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

Atzeni, Stefano; Marocchino, Alberto; Schiavi, Angelo



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


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

Délen, Xavier; Balembois, François; Georges, Patrick



Quantum spatial correlations in high-gain parametric down-conversion measured by means of a CCD camera  

E-print Network

We consider travelling-wave parametric down-conversion in the high-gain regime and present the experimental demonstration of the quantum character of the spatial fluctuations in the system. In addition to showing the presence of sub-shot noise fluctuations in the intensity difference, we demonstrate that the peak value of the normalized spatial correlations between signal and idler lies well above the line marking the boundary between the classical and the quantum domain. This effect is equivalent to the apparent violation of the Cauchy-Schwartz inequality, predicted by some of us years ago, which represents a spatial analogue of photon antibunching in time. Finally, we analyse numerically the transition from the quantum to the classical regime when the gain is increased and we emphasize the role of the inaccuracy in the determination of the symmetry center of the signal/idler pattern in the far-field plane.

O. Jedrkiewicz; E. Brambilla; M. Bache; A. Gatti; L. A. Lugiato; P. Di Trapani



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


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



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)



Sustained mild hypergravity reduces spontaneous cardiac baroreflex sensitivity.  


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

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



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

SciTech Connect

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

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



Surface plasmon resonance-induced color-selective Au-peapodded silica nanowire photodetectors with high photoconductive gain  

NASA Astrophysics Data System (ADS)

We report the optoelectronic device properties of individual Au-silica hybrid nanowires prepared by microwave plasma enhanced chemical vapor deposition. Due to the surface plasmon resonance (SPR) effect the photo-responsivity peak strongly depends on the shape of the embedded gold nanostructures in the silica nanowire in which the shape can be modified by controlling the growth time of Au-silica nanowires. Finite difference time domain (FDTD) simulation shows that the electric field distribution profiles of Au-silica hybrid nanowires support the photo-responsivity spectrum results. The photodetector performance of the Au-NPs@silica nanowire is investigated. The single Au-NPs@silica nanowire exhibits unique photo-responsivity in the visible range (500 nm), high selectivity, high photoconductive gain, and very fast rise (141 ?s) and decay (298 ?s) time constants. Furthermore, the mechanism for the high photoconductive gain is also discussed. This result implies that the Au-NPs@silica nanowire can be applied for future nanoscale optoelectronic devices.We report the optoelectronic device properties of individual Au-silica hybrid nanowires prepared by microwave plasma enhanced chemical vapor deposition. Due to the surface plasmon resonance (SPR) effect the photo-responsivity peak strongly depends on the shape of the embedded gold nanostructures in the silica nanowire in which the shape can be modified by controlling the growth time of Au-silica nanowires. Finite difference time domain (FDTD) simulation shows that the electric field distribution profiles of Au-silica hybrid nanowires support the photo-responsivity spectrum results. The photodetector performance of the Au-NPs@silica nanowire is investigated. The single Au-NPs@silica nanowire exhibits unique photo-responsivity in the visible range (500 nm), high selectivity, high photoconductive gain, and very fast rise (141 ?s) and decay (298 ?s) time constants. Furthermore, the mechanism for the high photoconductive gain is also discussed. This result implies that the Au-NPs@silica nanowire can be applied for future nanoscale optoelectronic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04533a

Wang, Sheng-Bo; Chen, Ruei-San; Chang, Shoou Jinn; Han, Hsieh-Cheng; Hu, Ming-Shien; Chen, Kuei-Hsien; Chen, Li-Chyong



High-gain solid-state and fiber amplifier-chain for high-power coherent communication  

Microsoft Academic Search

We report on the experimental results of a dual-stage amplifier combining a Nd-doped double-clad fiber and a Nd-doped YAG crystal. We obtained up to 3.5-W single-mode single-frequency output power with 28-dB gain. This is, to the best of our knowledge, the first demonstration of a dual-stage amplifier combining doped fibers and solid-state amplifiers

E. Rochat; K. Haroud; U. Roth; J. E. Balmer; R. Dandliker; H. P. Weber



Achieving and Maintaining Deep Space 1 Spacecraft High-Gain Antenna Pointing Control by Data Monitoring and Immediate Corrective Commanding  

NASA Astrophysics Data System (ADS)

The Deep Space 1 (DS1) onboard stellar reference unit failed in November 1999, leaving the spacecraft able to achieve only Sun point, with 8.4 GHz (X-band) communications reduced to the low rates supportable via a low-gain antenna. By January 2000, the DS1 project fight team implemented an interim three-axis pointing concept called the "HGA activity" because it made the high-gain antenna (HGA) usable again. The HGA activity involves the telecommunications analyst as an integral part of a closed-loop ground--spacecraft pointing control system. The HGA activity initiates pointing of the high-gain antenna toward the Earth and subsequently maintains pointing for the duration of one or two passes. The concept requires the tracking station to lock its receiver on the X-band carrier and provide carrier signal-to-noise ratio in monitor data in real time. The project telecommunications analyst uses the data to prepare accurate event timing predictions and to assess performance through rapid and precise comparisons of monitor and prediction data. Use of this labor-intensive and real-time process enabled the project to receive high-rate telemetry data from 14 passes through May 2000. Finally, another 14 HGA activities in June 2000 enabled the project to reload several megabytes of flight software at a high rate. The new software brought to an end the routine use of the HGA activity because it operates the science camera to generate star data for onboard pointing control. With full three-axis pointing capability restored for ion-propulsion subsystem thrusting, DS1 has resumed its science mission with a flyby of the comet Borrelly planned for September 2001.

Taylor, J.; Ko, P.



A solid state driven, parasitic oscillation suppressed, 17 GHz high gain tw klystron for stable operation with high gradient linac structures  

Microsoft Academic Search

The gain of a high power TW relativistic klystron can be increased substantially with the use of a varying phase velocity, large beam aperture, lengthened output structure, designed for asynchronous interaction to control space charge fields and provide near-adiabatic bunch compression during the power extraction process. While this technique enables the replacement of a pulsed vacuum tube driver system with

J. Haimson; B. Mecklenburg; G. Stowell; B. Ishii



1.5-?m tapered-gain-region lasers with high-CW output powers  

Microsoft Academic Search

High-power diode lasers consisting of a a tapered region have waveguide section coupled to fabricated in 1.5-?m InGaAsP-InP multiple-quantum-well material. Self-focusing at high current densities and high intensity input into the taper section has been identified as a fundamental problem in these devices that has to be dealt with. To date, continuous-wave output powers of >1 W with ≈80% of

J. P. Donnelly; J. N. Walpole; S. H. Groves; R. J. Bailey; L. J. Missaggia; A. Napoleone; R. E. Reeder; C. C. Cook



Shuttle orbiter Ku-band radar/communications system design evaluation: High gain antenna/widebeam horn  

NASA Technical Reports Server (NTRS)

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 antenna is examined and the high sidelobe levels measured are related to the physical characteristics of the antenna. An examination of the attributes of the feed which might be influenced by temperature extremes shows that the antenna should be insensitive to temperature variations. Because the feed support bipod structure is considered a significant contributor to the high sidelobe levels measured in the azimuth plane, pod relocation, material changes, and shaping are suggested as improvements. Alternate feed designs are presented to further improve system performance. The widebeam horn and potential temperature effects due to the polarizer are discussed as well as in the effects of linear polarization on TDRS acquisition, and the effects of circular polarization on radar sidelobe avoidance. The radar detection probability is analyzed as a function of scan overlap and target range.

Iwasaki, R.; Dodds, J. G.; Broad, P.



Statistical properties of radiation power levels from a high-gain free-electron laser at and beyond saturation  

SciTech Connect

We investigate the statistical properties (e.g., shot-to-shot power fluctuations) of the radiation from a high-gain free-electron laser (FEL) operating in the nonlinear regime. We consider the case of an FEL amplifier reaching saturation whose shot-to-shot fluctuations in input radiation power follow a gamma distribution. We analyze the corresponding output power fluctuations at and beyond first saturation, including beam energy spread effects, and find that there are well-characterized values of undulator length for which the fluctuation level reaches a minimum.

Schroeder, Carl B.; Fawley, William M.; Esarey, Eric



High gain, low noise, fully complementary logic inverter based on bi-layer WSe2 field effect transistors  

NASA Astrophysics Data System (ADS)

In this article, first, we show that by contact work function engineering, electrostatic doping and proper scaling of both the oxide thickness and the flake thickness, high performance p- and n-type WSe2 field effect transistors (FETs) can be realized. We report record high drive current of 98 ?A/?m for the electron conduction and 110 ?A/?m for the hole conduction in Schottky barrier WSe2 FETs. Then, we combine high performance WSe2 PFET with WSe2 NFET in double gated transistor geometry to demonstrate a fully complementary logic inverter. We also show that by adjusting the threshold voltages for the NFET and the PFET, the gain and the noise margin of the inverter can be significantly enhanced. The maximum gain of our chemical doping free WSe2 inverter was found to be ˜25 and the noise margin was close to its ideal value of ˜2.5 V for a supply voltage of VDD = 5.0 V.

Das, Saptarshi; Dubey, Madan; Roelofs, Andreas



Spontaneous abortion.  


Sporadic spontaneous abortion has been accorded relatively little scientific attention but has widespread prevalence and great personal impact. The physician must be continually vigilant to consider possibilities for Rh0(D) sensitization and offer prophylaxis when appropriate. The most immediate problems include differential diagnosis, haemorrhage, and infection, while later issues focus on counselling and subsequent pregnancies. Serious physical and psychological morbidity can be averted by the conscientious care of couples experiencing spontaneous pregnancy loss. PMID:3086012

Laferla, J J



Computational evidence for self-initiation in spontaneous high-temperature polymerization of methyl methacrylate.  


This paper presents computational evidence for the occurrence of diradical mechanism of self-initiation in thermal polymerization of methyl methacrylate. Two self-initiation mechanisms of interest were explored with first-principles density functional theory calculations. Singlet and triplet potential energy surfaces were constructed. The formation of two Diels-Alder adducts, cis- and trans-dimethyl 1,2-dimethylcyclobutane-1,2-dicarboxylate and dimethyl 2-methyl-5-methylidene-hexanedioate, on the singlet surface was identified. Transition states were calculated using B3LYP/6-31G* and assessed using MP2/6-31G*. The calculated energy barriers and rate constants with different levels of theory were found to show good agreement to corresponding data obtained from laboratory experiments. The presence of a diradical intermediate on the triplet surface was identified. When MCSCF/6-31G* was used, the spin-orbit coupling constant for the singlet to triplet crossover was calculated to be 2.5 cm(-1). The mechanism of monoradical generation via a hydrogen abstraction by both triplet and singlet diradicals from a third monomer was identified to be the most likely mechanism of initiation in spontaneous polymerization of methyl methacrylate. PMID:21265525

Srinivasan, Sriraj; Lee, Myung Won; Grady, Michael C; Soroush, Masoud; Rappe, Andrew M



High Rates of Occurrence of Spontaneous Chromosome Aberrations in DROSOPHILA MELANOGASTER.  


Spontaneous mutations were accumulated for 40 generations in 140 unrelated second chromosomes with the standard gene arrangement. These were extracted from the same population by using the marked inversion technique, and the following findings were obtained: (1) In 42 out of the 140 chromosome lines, chromosome aberrations were detected by examining the salivary gland chromosomes: 40 paracentric and 15 pericentric inversions, 2 reciprocal translocations between the second and the third chromosomes, and 6 transpositions. (2) In 63 out of the 90 originally lethal-free lines, recessive lethal mutations occurred. (3) There were only 3 lines that acquired chromosome aberrations (inversions) with no lethal effects in the homozygous condition. (4) In a comparison of these results with those of the (CH), (PQ), and (RT) chromosomes in which no chromosome aberrations occurred after accumulating mutations for 22058 chromosome.generations (Yamaguchi and Mukai 1974), it was concluded that some of these 140 chromosomes carried a kind of mutator. (5) The frequency of mutator-carrying chromosome lines was estimated to be 0.66 on the basis of the distribution of the break-points on the chromosome lines and the frequency of lines that acquired neither recessive lethal mutations nor chromosome aberrations. Thus, the average number of breaks per mutator-carrying chromosome was estimated to be about 0.19/generation.On the basis of these estimates, the nature of the mutator factor was discussed. PMID:17248724

Yamaguchi, O; Cardellino, R A; Mukai, T



High Rates of Occurrence of Spontaneous Chromosome Aberrations in DROSOPHILA MELANOGASTER  

PubMed Central

Spontaneous mutations were accumulated for 40 generations in 140 unrelated second chromosomes with the standard gene arrangement. These were extracted from the same population by using the marked inversion technique, and the following findings were obtained: (1) In 42 out of the 140 chromosome lines, chromosome aberrations were detected by examining the salivary gland chromosomes: 40 paracentric and 15 pericentric inversions, 2 reciprocal translocations between the second and the third chromosomes, and 6 transpositions. (2) In 63 out of the 90 originally lethal-free lines, recessive lethal mutations occurred. (3) There were only 3 lines that acquired chromosome aberrations (inversions) with no lethal effects in the homozygous condition. (4) In a comparison of these results with those of the (CH), (PQ), and (RT) chromosomes in which no chromosome aberrations occurred after accumulating mutations for 22058 chromosome·generations (Yamaguchi and Mukai 1974), it was concluded that some of these 140 chromosomes carried a kind of mutator. (5) The frequency of mutator-carrying chromosome lines was estimated to be 0.66 on the basis of the distribution of the break-points on the chromosome lines and the frequency of lines that acquired neither recessive lethal mutations nor chromosome aberrations. Thus, the average number of breaks per mutator-carrying chromosome was estimated to be about 0.19/generation. On the basis of these estimates, the nature of the mutator factor was discussed. PMID:17248724

Yamaguchi, Osamu; Cardellino, Ricardo A.; Mukai, Terumi



High-Resolution Mapping of Two Types of Spontaneous Mitotic Gene Conversion Events in Saccharomyces cerevisiae  

PubMed Central

Gene conversions and crossovers are related products of the repair of double-stranded DNA breaks by homologous recombination. Most previous studies of mitotic gene conversion events have been restricted to measuring conversion tracts that are <5 kb. Using a genetic assay in which the lengths of very long gene conversion tracts can be measured, we detected two types of conversions: those with a median size of ?6 kb and those with a median size of >50 kb. The unusually long tracts are initiated at a naturally occurring recombination hotspot formed by two inverted Ty elements. We suggest that these long gene conversion events may be generated by a mechanism (break-induced replication or repair of a double-stranded DNA gap) different from the short conversion tracts that likely reflect heteroduplex formation followed by DNA mismatch repair. Both the short and long mitotic conversion tracts are considerably longer than those observed in meiosis. Since mitotic crossovers in a diploid can result in a heterozygous recessive deleterious mutation becoming homozygous, it has been suggested that the repair of DNA breaks by mitotic recombination involves gene conversion events that are unassociated with crossing over. In contrast to this prediction, we found that ?40% of the conversion tracts are associated with crossovers. Spontaneous mitotic crossover events in yeast are frequent enough to be an important factor in genome evolution. PMID:24990991

Yim, Eunice; O'Connell, Karen E.; St. Charles, Jordan; Petes, Thomas D.



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. PMID:21975121

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



Performance optimization of diffused Li on Ga/In eutectic, In/Sn solder and eutectic Ga/In Ohmic contacts to n-high purity-crystalline (100) Ge  

NASA Astrophysics Data System (ADS)

Performance optimization study of novel contacts such as diffused lithium on Ga/In eutectic (75.5/24.5 wt%), In/Sn solder (95.0/5.0 wt%) and Ga/In eutectic (75.5/24.5 wt%) to n-high purity-crystalline <100> Ge (HP-SC-Ge) has been presented. Ultrasonically clean samples taken from same substrate were used to process the contacts followed by their characterization utilizing current--voltage (I--V), Hall-effect and AFM measurements. Extreme care was introduced to minimize the effect of parasitic oxide layers. Contacts such as diffused Li on eutectic Ga/In and In/Sn solder were processed in an inert glove box and characterized at 305 K (RT) and 77 K (LN) respectively. Comparative study revealed that Ga/In eutectics contacts behave throughout linear and stable, showing strong hall-effect to that of its counter parts. This was attributed due to the high adsorption behavior of anions at liquid (Ga--In) contacts and improved wettability. Whereas, for In/Sn solder case, the contacts processing considerations were substantially different, mainly because of its poor solder flow, excessive void formation, and heterogeneous phase distribution responsible for process yield loss. For diffused Li on Ga/In eutectic contacts, the linearity of the obtained Ohmic profiles was not consistent due to the high reactivity of the Li with HP-SC-Ge substrate. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

Khan, Khizar; Gang, Yang; Wang, Guojian; Xiang, Wenchang; Guan, Yutong; Mei, Dongming



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

National Technical Information Service (NTIS)

The effects of translocation to high altitude on growth rate, nitrogen retention and body composition were studied in meal-eating albino rats. Ad libitum-fed, meal-eating rats were rapidly (2.25 hours) translocated from Denver (1,600 meters) to Pikes Peak...

D. D. Schnakenberg, L. F. Krabill, P. C. Weiser



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

Microsoft Academic Search

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

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



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

ERIC Educational Resources Information Center

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

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



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



High gain CMOS image sensor design and fabrication on SOI and bulk technology  

Microsoft Academic Search

The CMOS imager is now competing with the CCD imager, which still dominates the electronic imaging market. By taking advantage of the mature CMOS technology, the CMOS imager can integrate AID converters, digital signal processing (DSP) and timing control circuits on the same chip. This low cost and high-density integration solution to the image capture is the strong driving force

Weiquan Zhang



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

SciTech Connect

The electrical properties of semi-insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle detectors and photoconductive semiconductor switches (PCSS). PCSS made from these materials operating in both the linear and non-linear modes have applications such as firing sets, as drivers for lasers, and in high impedance, low current Q-switches or Pockels cells. In the non-linear mode, it has also been used in a system to generate Ultra-Wideband (UWB) High Power Microwaves (HPM). The choice of GaAs over silicon offers the advantage that its material properties allow for fast, repetitive switching action. Furthermore photoconductive switches have advantages over conventional switches such as improved jitter, better impedance matching, compact size, and in some cases, lower laser energy requirement for switching action. The rise time of the PCSS is an important parameter that affects the maximum energy transferred to the load and it depends, in addition to other parameters, on the bias or the average field across the switch. High field operation has been an important goal in PCSS research. Due to surface flashover or premature material breakdown at higher voltages, most PCSS, especially those used in high power operation, need to operate well below the inherent breakdown voltage of the material. The lifetime or the total number of switching operations before breakdown, is another important switch parameter that needs to be considered for operation at high bias conditions. A lifetime of {approximately} 10{sup 4} shots has been reported for PCSS's used in UWB-HPM generation [5], while it has exceeded 10{sup 8} shots for electro-optic drivers. Much effort is currently being channeled in the study related to improvements of these two parameters high bias operation and lifetime improvement for switches used in pulsed power applications. The contact material and profiles are another important area of study. Although these problems are being pursued through the incorporation of different contact materials and introducing doping near contacts, it is important that the switch properties and the conduction mechanism in these switches be well understood such that the basic nature of the problems can be properly addressed. In this paper the authors report on these two basic issues related to the device operation, i.e., mechanisms for increasing the hold-off characteristics through neutron irradiation, and the analysis of transport processes at varying field conditions in trap dominated SI GaAs in order to identify the breakdown mechanism during device operation. It is expected that this study would result in a better understanding of photoconductive switches, specifically those used in high power operation.




Origin of high photoconductive gain in fully transparent heterojunction nanocrystalline oxide image sensors and interconnects.  


A technique for invisible image capture using a photosensor array based on transparent conducting oxide semiconductor thin-film transistors and transparent interconnection technologies is presented. A transparent conducting layer is employed for the sensor electrodes as well as interconnection in the array, providing about 80% transmittance at visible-light wavelengths. The phototransistor is a Hf-In-Zn-O/In-Zn-O heterostructure yielding a high quantum-efficiency in the visible range. PMID:25219518

Jeon, Sanghun; Song, Ihun; Lee, Sungsik; Ryu, Byungki; Ahn, Seung-Eon; Lee, Eunha; Kim, Young; Nathan, Arokia; Robertson, John; Chung, U-In



New High Voltage Gain Dual-boost DC-DC Converter for Photovoltaic Power Systems  

Microsoft Academic Search

This article presents a new circuit topology of a high-voltage step-up boost DC-DC converter for photovoltaic power systems. The converter boosts the low-output voltage of the solar cell to the required voltage for the load. The proposed circuit has various advantages compared to the conventional boost converters, namely a higher boost rate with low duty cycle, lower voltage stress on

Khairy Sayed; Mazen Abdel-Salam; Adel Ahmed; Mahmoud Ahmed



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

Microsoft Academic Search

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

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



A high current gain 4H-SiC NPN power bipolar junction transistor  

Microsoft Academic Search

This work reports the development of high power 4H-SiC bipolar junction transistors (BJTs) by using reduced implantation dose for p+ base contact region and annealing in nitric oxide of base-to-emitter junction passivation oxide for 2 hours at 1150°C. The transistor blocks larger than 480 V and conducts 2.1 A (Jc=239 A\\/cm2) at Vce=3.4 V, corresponding to a specific on-resistance (Rsp

Jianhui Zhang; Yanbin Luo; Petre Alexandrov; Leonid Fursin; Jian H. Zhao



Different effects of aspirin on blood pressure of spontaneously hypertensive rats (SHR) with high and spontaneously low levels of blood pressure.  

PubMed Central

Spontaneously hypertensive rats (SHR) of the Okamoto strain with blood pressure above 161 mmHg and SHR with blood pressure levels of less than 160 mmHg were treated with oral doses of aspirin (100 mg kg-1) for three days. Whereas the blood pressure of SHR with blood pressure above 161 mmHg was decreased by aspirin, the blood pressure of SHR below 160 mmHg was increased by aspirin. The extent and direction of blood pressure change by aspirin was strongly correlated with the blood pressure of SHR before treatment (r = -0.88). The effect of aspirin supports an important role for endogenous prostanoids in the regulation of blood pressure of SHR. PMID:8401941

Schirner, M.; Taube, C.



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



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


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

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



Investigation of high energy ?-rays accompanying spontaneous fission of 252Cf in double and triple neutron-? coincidences  

NASA Astrophysics Data System (ADS)

The high energy bremsstrahlung ?-rays accompanying the spontaneous fission of 252 Cf were measured in the 10-70 MeV energy range. The photons were detected by two BGO scintillator detectors (ø7.6cm × 7.6cm) in coincidence with neutrons detected by plastic scintillator detector, in the 90° and 180° geometry of the two BGO detectors with respect to the axis of the plastic scintillator. The distance from the 252Cf source to the BGO detectors was 10 cm, and the one to the plastic detector was 50 cm. The fast digital shape analysis technique and the time-of-flight method were used to reject pile-up effects and cosmic ray background. The ?-ray emission probability of 3 × 10-8photon/(MeV × fission) at E? = 70 MeV was obtained.

Eremin, N. V.; Markochev, S. S.; Paskhalov, A. A.; Mandaglio, G.; Manganaro, M.; Fazio, G.; Giardina, G.; Romaniuk, M. V.



On the long-memory filtering gain in optical high-order QAM transmission systems.  


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



A CMOS linear-in-dB high-linearity variable-gain amplifier for UWB receivers  

Microsoft Academic Search

This paper presents a CMOS linear-in-dB variable gain amplifier (VGA) that provides a variable gain range over 90 dB with 3 dB bandwidth greater than 400 MHz at 54 dB gain. The maximum output 1 dB compression point is 9 dBm. Maximum gain error is +\\/-2 dB. It consumes total 22 mW with 1.8 V supply, including control circuit. This

Chan Tat Fu; Howard Luong



College Expectations in High School Mitigate Weight Gain over Early Adulthood: Findings from a National Study of American Youth  

PubMed Central

Objective Research conducted on school-based interventions suggests that school connectedness protects against a variety of risk behaviors, including substance abuse, delinquency and sedentary behavior. We extend this line of research by examining the link between college expectations and early adult weight gain using nationally representative panel data from thirty cohorts of American high school seniors followed prospectively to age 30 in the Monitoring the Future Study (1986–2009). Design and Methods Growth mixture models identified two latent classes of trajectories of body mass index (BMI) from age 19 to 30: a persistently overweight class (BMI?25) and a second class exhibiting more moderate growth in BMI to age 30. Results Compared to those who did not expect to graduate from college, students fully expecting to graduate from college had 34% lower odds of being in the persistently overweight class (adjusted odds ratio = 0.66, 95% confidence interval = 0.54, 0.81), controlling for academic performance and socioeconomic status. Conclusions Successful prevention of obesity early in the life course is based on a multifactorial approach incorporating strategies that address the contexts in which adolescents are embedded. The school setting may be one avenue where successful educational attachment could have positive consequences for subsequent weight gain in early adulthood. PMID:23666817

Clarke, Philippa J.; O'Malley, Patrick M.; Schulenberg, John E.; Lee, Hedwig; Colabianchi, Natalie; Johnston, Lloyd D.



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

NASA Astrophysics Data System (ADS)

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

Taylor, Travis S.


Spontaneous high-frequency (10-80 Hz) oscillations during up states in the cerebral cortex in vitro.  


High-frequency oscillations in cortical networks have been linked to a variety of cognitive and perceptual processes. They have also been recorded in small cortical slices in vitro, indicating that neuronal synchronization at these frequencies is generated in the local cortical circuit. However, in vitro experiments have hitherto necessitated exogenous pharmacological or electrical stimulation to generate robust synchronized activity in the beta/gamma range. Here, we demonstrate that the isolated cortical microcircuitry generates beta and gamma oscillations spontaneously in the absence of externally applied neuromodulators or synaptic agonists. We show this in a spontaneously active slice preparation that engages in slow oscillatory activity similar to activity during slow-wave sleep. beta and gamma synchronization appeared during the up states of the slow oscillation. Simultaneous intracellular and extracellular recordings revealed synchronization between the timing of incoming synaptic events and population activity. This rhythm was mechanistically similar to pharmacologically induced gamma rhythms, as it also included sparse, irregular firing of neurons within the population oscillation, predominant involvement of inhibitory neurons, and a decrease of oscillation frequency after barbiturate application. Finally, we show in a computer model how a synaptic loop between excitatory and inhibitory neurons can explain the emergence of both the slow (<1 Hz) and the beta-range oscillations in the neocortical network. We therefore conclude that oscillations in the beta/gamma range that share mechanisms with activity reported in vivo or in pharmacologically activated in vitro preparations can be generated during slow oscillatory activity in the local cortical circuit, even without exogenous pharmacological or electrical stimulation. PMID:19091973

Compte, Albert; Reig, Ramon; Descalzo, Vanessa F; Harvey, Michael A; Puccini, Gabriel D; Sanchez-Vives, Maria V



Adaptive fuzzy backstepping output feedback control for a class of MIMO time-delay nonlinear systems based on high-gain observer  

Microsoft Academic Search

In this paper, an adaptive fuzzy backstepping output feedback control approach is developed for a class of multiinput and\\u000a multioutput (MIMO) nonlinear systems with time delays and immeasurable states. Fuzzy logic systems are employed to approximate\\u000a the unknown nonlinear functions, and an adaptive fuzzy high-gain observer is developed to estimate the unmeasured states.\\u000a Using the designed high-gain observer, and combining

Yongming Li; Chang’e Ren; Shaocheng Tong


Gimbals Drive and Control Electronics Design, Development and Testing of the LRO High Gain Antenna and Solar Array Systems  

NASA Technical Reports Server (NTRS)

Launched June 18, 2009 on an Atlas V rocket, NASA's Lunar Reconnaissance Orbiter (LRO) is the first step in NASA's Vision for Space Exploration program and for a human return to the Moon. The spacecraft (SC) carries a wide variety of scientific instruments and provides an extraordinary opportunity to study the lunar landscape at resolutions and over time scales never achieved before. The spacecraft systems are designed to enable achievement of LRO's mission requirements. To that end, LRO's mechanical system employed two two-axis gimbal assemblies used to drive the deployment and articulation of the Solar Array System (SAS) and the High Gain Antenna System (HGAS). This paper describes the design, development, integration, and testing of Gimbal Control Electronics (GCE) and Actuators for both the HGAS and SAS systems, as well as flight testing during the on-orbit commissioning phase and lessons learned.

Chernyakov, Boris; Thakore, Kamal



Synthesis of fiber Bragg grating for gain-narrowing compensation in high-power Nd: Glass chirped pulse amplification system  

NASA Astrophysics Data System (ADS)

We propose and analyze theoretically a method to compensate gain-narrowing effect by using the spectral shaping technology based on superstructure fiber Bragg grating (SSFBG) in high-power Nd:glass chirped pulse amplification system. The target spectrum is firstly calculated from hundreds joules amplified chirped Gaussian or super-Gaussian pulse by an inverse engineering operation. A genetic algorithm is used to design the SSFBG and obtain the index modulation distribution of grating which can transform the initial seed pulse to the target spectrum. The numerically simulations show that the spectral narrowing effect of chirped pulse amplification will be reduced largely and the ideal pulse spectrum (Gaussian or super-Gaussian) is also obtained. It is believed that this proposed method will provide a theoretical direction for the following experiment. Moreover, it will also be useful and flexible for the spectral transform in other chirped pulse application areas.

Liu, Qiong; Ye, Qing; Pan, Zhengqing; Luo, Aiping; Cai, Haiwen; Qu, Ronghui; Fang, Zujie



Flexible high gain complementary inverter using n-ZnO and p-pentacene channels on polyethersulfone substrate  

NASA Astrophysics Data System (ADS)

We report on the fabrication of complementary inverters that have ZnO and pentacene as n-type and p-type channels on a polyethersulfone substrate operating under 7V. Patterned Al and AlOx thin film were deposited at room temperature on the plastic as a common gate electrode and dielectric, respectively. After initial gate instability between ZnO channel and AlOx dielectric was controlled, our n-type thin-film transistors (TFTs) displayed quite a similar drain current level to that of p-type TFTs. Our flexible complementary device showed much high voltage gain of ˜100 even under a bent condition (56mm radius of curvature). Our complementary inverter also demonstrates a promising dynamic behavior of ˜20ms.

Oh, Min Suk; Choi, Wonjun; Lee, Kimoon; Hwang, D. K.; Im, Seongil



High-power and high-gain organic dye-doped polymer optical fiber amplifiers: novel techniques for preparation and spectral investigation  

Microsoft Academic Search

Rhodamine B (RB), Rhodamine 6G (R6G), Oxazine 4 perchlorate (O4PC), and 4-Dicyanomethylene-2-methyl-6-( p -dimethylaminostyryl -4H-pyran)-doped graded-index (GI) polymer optical fiber amplifiers (POFA s) were successfully prepared by novel techniques to prevent degradation of organic dyes and to enhance solubility of the dyes in methyl methacrylate and in poly(methyl methacrylate) (PMMA). High-power (620 W) and high-gain (33-dB, 2070 times) amplification was

Akihiro Tagaya; Shigehiro Teramoto; Eisuke Nihei; Keisuke Sasaki; Yasuhiro Koike



Instructional practices among science departments with high, moderate, and low gains on the Connecticut Academic Performance Test  

NASA Astrophysics Data System (ADS)

The purpose of this study was to ascertain whether the instructional practices of performance-based, inquiry-based, and authentic-based learning strategies, and rubric use are related to improvement on the science portion of the Connecticut Academic Performance Test [CAPT], as indicated by CAPT gains from 1995--2001. Data were collected for this study by a survey/interview of 63 Connecticut high schools and their 118 certified biology teachers, who had participated in the science CAPT administration within that same school district during 1995--2001. Results from the analysis of the data indicate a significant relationship between strategy and rubric use and CAPT science score outputs. Those schools having the highest levels of strategy and rubric use also demonstrated high CAPT gains and increasing CAPT scores, over time. It was also determined that a strong relationship exists between the percentage of the ERG's goal for CAPT index and those ERGs, using strategies and/or rubrics proficiently. The major findings of the study reveal that teachers demonstrate a confusion of strategy/rubric meaning, as indicated by the low proficiency levels of their submitted strategy and rubric samples, despite high indicators of use for the three learning strategies and rubrics. In addition, rubrics are rated highly by the sample, but are not employed at the high levels of reported favorability. Further analysis determines that objective forms of assessment are used more frequently than strategy and rubric use, and may be implicated for the decreased use of rubrics. Although survey data indicate that 90% of the sample reported "Satisfactory" to "Excellent" levels of annual score updates within their respective districts, teachers requested a need for increased pre- and in-service professional development in the use of all three strategies and rubrics: particularly non-tenured teachers expressed a need for basic CAPT information and samples of strategy and rubric use, while teachers with greater than four years of experience requested both inter- and intra-district science collaboration and communication: teachers from all ERGs requested to develop curriculum and strategic planning initiatives to implement CAPT-based strategies and rubrics for CAPT science score improvement.

Kachergis, Theodora R.


High-Power High-Gain Diffraction-Limited Emission from Single-Mode Tapered Semiconductor Optical Amplifiers  

Microsoft Academic Search

The realization of high-power (over 1 Watt), coherent diode lasers will open up new possibilities in printing, biomedicine, efficient pumping of solid state lasers and rare-earth doped fiber amplifiers, free-space optical communication, and nonlinear frequency conversion to the blue spectral region. The most successful approach toward high-power coherent light sources to date is the master oscillator power amplifier (MOPA) configuration

Ping-Hui Sophia Yeh



Wheel Access Does Not Attenuate Weight Gain in Mice Fed High-Fat or High-CHO Diets  

PubMed Central

Purpose To determine the effect of a high-fat or high-carbohydrate diet and running wheel activity on body composition, body mass, and caloric intake in C57Bl/6 mice. Methods At four weeks of age, five groups of C57Bl/6 mice were housed individually. Two groups had running wheels, while the other three groups did not. Within the running wheel groups, FAT-W consumed a high-fat diet (60.3% fat) and CHO-W consumed a high-carbohydrate diet (70.4% carbohydrate). Within the non-running groups, FAT consumed the high-fat diet, CHO consumed the high-carbohydrate diet, and CON consumed standard chow. All groups consumed food ad libitum, and were exposed to their respective conditions for 12 weeks. Wheel activity, food consumption, body mass (BM), and body fat (%BF) were recorded. Results There was no significant difference in %BF or BM at the end of 12 weeks between FAT-W and FAT or between CHO-W and CHO (p>0.05). %BF was significantly higher in both FAT-W (42.9±0.6%) and FAT (45.9±0.8%) compared to CHO-W (30.8±1.4%) or CHO (33.4±1.0%; p<0.001). BM was significantly higher in both FAT-W (42.8±0.7g) and FAT (44.7±1.2g) compared to either CHO-W (32.8±1.6g) or CHO (37.1±0.8; p<0.01). There was no difference in wheel activity between FAT-W and CHO-W (p>0.05). Daily caloric intake was higher in both FAT-W (17.0±0.8kcal) and FAT (15.9±0.9kcal) compared to CHO-W (13.9±0.7kcal) and CHO (13.6±0.5kcal; p<0.01). Conclusion Access to a running wheel had no protective effect on BM or %BF in C57Bl/6 mice that consumed either a high-fat or high-carbohydrate diet over a 12-week period. Access to a running wheel did not affect caloric intake; however, average daily caloric intake was higher in mice on high-fat diets compared to mice on a high-carbohydrate diet. PMID:19927024

Jung, Alan P.; Luthin, David R.



[Non-random distribution of spontaneous and high temperature-induced recessive lethal mutations in the X-chromosome of Drosophila].  


Frequency and localization of spontaneous and induced by high temperature (37 degrees C) recessive lethal mutations in X-chromosome of females belonging to the 1(1) ts 403 strain defective in synthesis of heat-shock proteins (HSP) were studied. No differences in frequencies of both spontaneous and induced lethals between 1(1) ts 403 and control strain were found, thus implying that the disturbances in HSP synthesis have no effect on this process in oocytes of Drosophila melanogaster females. Surprisingly, distribution of spontaneous and induced lethals along the X-chromosome of 1(1) ts 403 strain appeared to be non-random: they primarily are located in its distal portion (1-44 cM of genetic map or in I-II sections of the Bridges cytogenetic map). This correlates with non-random distribution of mobile elements in the X-chromosome of D. melanogaster (Leibovich, 1990). PMID:1778461

Mamon, L A; Barabanova, L V



Multiple-wavelength conversion with gain by a high-repetition-rate pulsed-pump fiber OPA  

Microsoft Academic Search

The authors propose and demonstrate a novel multiple-wavelength converter with gain, based on a pulsed-pump fiber optical parametric amplifier (OPA). It generates multiple replicas of the signal, as well as spectrally inverted versions. The device is modeled by using quasi-steady-state OPA gain equations, as well as by the split-step Fourier method. Predicted conversion gains of up to 20 dB have

Georgios Kalogerakis; M. E. Marhic; Leonid G. Kazovsky



High current gain graded GaN\\/InGaN heterojunction bipolar transistors grown on sapphire and SiC substrates by metalorganic chemical vapor deposition  

Microsoft Academic Search

High-current-gain GaN\\/InGaN double heterojunction bipolar transistors having a graded-base and emitter design grown on sapphire and SiC substrates by metalorganic chemical vapor deposition are presented. Improved device performances result from the improvement of the InGaN graded layer material quality and the p-type doping enhancement as well as the improvement of device fabrication techniques. The devices show common-emitter incremental current gain

T. Chung; D. M. Keogh; J.-H. Ryou; D. Yoo; J. Limb; W. Lee; S.-C. Shen; P. M. Asbeck; R. D. Dupuis



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

Microsoft Academic Search

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

Venu Gopinathan; Maurice Tarsia; Davy Choi



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

PubMed Central

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

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



A low-carbohydrate/high-fat diet reduces blood pressure in spontaneously hypertensive rats without deleterious changes in insulin resistance  

PubMed Central

Previous studies reported that diets high in simple carbohydrates could increase blood pressure in rodents. We hypothesized that the converse, a low-carbohydrate/high-fat diet, might reduce blood pressure. Six-week-old spontaneously hypertensive rats (SHR; n = 54) and Wistar-Kyoto rats (WKY; n = 53, normotensive control) were fed either a control diet (C; 10% fat, 70% carbohydrate, 20% protein) or a low-carbohydrate/high-fat diet (HF; 20% carbohydrate, 60% fat, 20% protein). After 10 wk, SHR-HF had lower (P < 0.05) mean arterial pressure than SHR-C (148 ± 3 vs. 159 ± 3 mmHg) but a similar degree of cardiac hypertrophy (33.4 ± 0.4 vs. 33.1 ± 0.4 heart weight/tibia length, mg/mm). Mesenteric arteries and the entire aorta were used to assess vascular function and endothelial nitric oxide synthase (eNOS) signaling, respectively. Endothelium-dependent (acetylcholine) relaxation of mesenteric arteries was improved (P < 0.05) in SHR-HF vs. SHR-C, whereas contraction (potassium chloride, phenylephrine) was reduced (P < 0.05). Phosphorylation of eNOSSer1177 increased (P < 0.05) in arteries from SHR-HF vs. SHR-C. Plasma glucose, insulin, and homoeostatic model of insulin assessment were lower (P < 0.05) in SHR-HF vs. SHR-C, whereas peripheral insulin sensitivity (insulin tolerance test) was similar. After a 10-h fast, insulin stimulation (2 U/kg ip) increased (P < 0.05) phosphorylation of AktSer473 and S6 in heart and gastrocnemius similarly in SHR-C vs. SHR-HF. In conclusion, a low-carbohydrate/high-fat diet reduced blood pressure and improved arterial function in SHR without producing signs of insulin resistance or altering insulin-mediated signaling in the heart, skeletal muscle, or vasculature. PMID:23604708

Bosse, John D.; Lin, Han Yi; Sloan, Crystal; Zhang, Quan-Jiang; Abel, E. Dale; Pereira, Troy J.; Dolinsky, Vernon W.; Symons, J. David




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.



High-Gain, Polarization-Preserving, Yb-Doped Fiber Amplifier for Low-Duty-Cycle Pulse Amplification  

SciTech Connect

Amplified spontaneous emission (ASE) suppression techniques were utilized to fabricate a double-pass, Yb-doped amplifier with the noise properties of a single-pass amplifier. Simulations based on a rate equation model were used to analyze the ASE and the effectiveness of the suppression techniques.

Marciante, J.R.; Zuegel, J.D.



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

E-print Network

in the experiments. Index Terms-- coupled lasers, coherence, synchrony, two way coupling, optical fibers, laser array fiber laser arrays Jeffrey L. Rogers, Slaven Peles, and Kurt Wiesenfeld (Invited Paper) Abstract-- Recent experiments [1] have shown that a small number of fiber lasers can spontaneously form coherent

PeleÂ?, Slaven


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

NASA Technical Reports Server (NTRS)

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

Kojima, Jun; Nguyen, Quang-Viet



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


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



Green tea decoction improves glucose tolerance and reduces weight gain of rats fed normal and high-fat diet.  


Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis. PMID:24656388

Snoussi, Chahira; Ducroc, Robert; Hamdaoui, Mohamed Hédi; Dhaouadi, Karima; Abaidi, Houda; Cluzeaud, Francoise; Nazaret, Corinne; Le Gall, Maude; Bado, André



Severe obesity, gestational weight gain, and adverse birth outcomes123  

PubMed Central

Background: The 2009 Institute of Medicine (IOM) Committee to Reevaluate Gestational Weight Gain Guidelines concluded that there were too few data to inform weight-gain guidelines by obesity severity. Therefore, the committee recommended a single range, 5–9 kg at term, for all obese women. Objective: We explored associations between gestational weight gain and small-for-gestational-age (SGA) births, large-for-gestational-age (LGA) births, spontaneous preterm births (sPTBs), and medically indicated preterm births (iPTBs) among obese women who were stratified by severity of obesity. Design: We studied a cohort of singleton, live-born infants without congenital anomalies born to obesity class 1 (prepregnancy body mass index [BMI (in kg/m2)]: 30–34.9; n = 3254), class 2 (BMI: 35–39.9; n = 1451), and class 3 (BMI: ?40; n = 845) mothers. We defined the adequacy of gestational weight gain as the ratio of observed weight gain to IOM-recommended gestational weight gain. Results: The prevalence of excessive gestational weight gain declined, and weight loss increased, as obesity became more severe. Generally, weight loss was associated with an elevated risk of SGA, iPTB, and sPTB, and a high weight gain tended to increase the risk of LGA and iPTB. Weight gains associated with probabilities of SGA and LGA of ?10% and a minimal risk of iPTB and sPTB were as follows: 9.1–13.5 kg (obesity class 1), 5.0–9 kg (obesity class 2), 2.2 to <5.0 kg (obesity class 3 white women), and <2.2 kg (obesity class 3 black women). Conclusion: These data suggest that the range of gestational weight gain to balance risks of SGA, LGA, sPTB, and iPTB may vary by severity of obesity. PMID:20357043

Bodnar, Lisa M; Siega-Riz, Anna Maria; Simhan, Hyagriv N; Himes, Katherine P; Abrams, Barbara



Overexpression of VEGF-C attenuates chronic high salt intake-induced left ventricular maladaptive remodeling in spontaneously hypertensive rats.  


Recent studies have shown that the tonicity-responsive enhancer binding protein (TonEBP)/vascular endothelial growth factor-C (VEGF-C) signaling pathway-induced lymphangiogenesis provides a buffering mechanism for high salt (HS) intake-induced elevation of blood pressure (BP). Moreover, blocking of TonEBP/VEGF-C signaling by mononuclear phagocyte depletion can induce salt-sensitive hypertension in rats. We hypothesized that HS intake could have an impact on cardiac lymphangiogenesis, and regulation of VEGF-C bioactivity, which is largely through the main receptor for VEGFR-3, may modulate HS intake-induced left ventricular remodeling. We demonstrated upregulation of TonEBP, increased macrophage infiltration, and enhanced lymphangiogenesis in the left ventricles of spontaneously hypertensive rats (SHR) that were fed a HS diet (8.0% NaCl). Then, retrovirus vectors capable of overexpression (?N?C/VEGF-C/Cys152Ser, used for overexpressing VEGF-C) and blocking (VEGFR-3-Rg, used for trapping of bioactive VEGF-C) of VEGF-C and control vector (pLPCX) were intravenously administered to SHR from week 9 of a 12-wk HS loading period. At the end of the HS challenge, overexpression of VEGF-C led to enhanced cardiac lymphangiogenesis, decreased myocardial fibrosis, and macrophage infiltration, preserved left ventricular functions, as well as decreased blood pressure level compared with the HS group and the control vector-treated HS group. In contrast, systemic blocking of VEGF-C was associated with elevation of blood pressure level and an exacerbation of hypertensive left ventricular remodeling, as indicated by increased fibrosis and macrophage infiltration, and diminished lymphangiogenesis. Hence, our findings highlight that VEGF-C/VEGFR-3 is a promising therapeutic target to attenuate hypertensive left ventricular remodeling induced by HS intake, presumably via blood pressure-dependent and -independent mechanisms. PMID:24337460

Yang, Guo-Hong; Zhou, Xin; Ji, Wen-Jie; Zeng, Shan; Dong, Yan; Tian, Lu; Bi, Ying; Guo, Zhao-Zeng; Gao, Fei; Chen, Hong; Jiang, Tie-Min; Li, Yu-Ming



The X-Target: A novel high gain target with single-sided heavy-ion beam illumination  

NASA Astrophysics Data System (ADS)

A new inertial-fusion target configuration, the X-target, using one-sided heavy ion axial illumination has been explored [1]. It takes advantage of the unique energy deposition properties of heavy ion beams that have a classical, long penetration range. This class of target uses heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an ``X''. X-targets that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT are capable of assembling fuel areal densities ˜2 g/cm^2 using two MJ-scale annular beams to implode quasi-spherically the target to peak DT densities ˜100 g/cm^3. A 3MJ fast-ignition solid ion beam heats the fuel to thermonuclear temperatures in ˜200 ps to start the burn propagation, obtaining gains of ˜300. The main concern for the X-target is the amount of high-Z atomic mixing at the ignition zone produced by hydro-instabilities, which, if large enough, could cool the fuel during the ignition process and prevent the propagation of the fusion burn. Analytic estimates and implosion calculations using the radiation hydrodynamics code HYDRA in 2D (RZ), at typical Eulerian mesh resolutions of a few microns, have shown that for the relatively low implosion velocities, low stagnation fuel densities, and low quasi-spherical fuel convergence ratios of the X-target, these hydro-instabilities do not have a large effect on the burning process. These preliminary studies need to be extended by further hydrodynamic calculations using finer resolution, complemented with turbulent mix modeling and validated by experiments, to ascertain the stability of the X-target design. We will present the current status of the X-target. [4pt] [1] E. Henestroza and B. G. Logan, Phys. Plasmas 19, 072706 (2012)

Henestroza, Enrique



Correlation of high and decreased NY-ESO-1 immunity to spontaneous regression and subsequent recurrence in a lung cancer patient  

PubMed Central

We show correlation between strong and decreased NY-ESO-1-specific immunity with spontaneous regression and subsequent recurrence, respectively, in a long-surviving patient with an NY-ESO-1-expressing lung adenocarcinoma. An integrated immune response consisting of IgG antibody, as well as CD4 and CD8 T cells, against NY-ESO-1 was observed at the time of spontaneous regression of multiple pleural metastases. After tumor dormancy for 3 years, the tumor started to progress. IgG antibody levels and the number of CD4 and CD8 T cells against NY-ESO-1 decreased, but were still detectable. On the other hand, the number of Foxp3+ CD25 high T regulatory cells gradually increased. The findings suggest the relevance of the NY-ESO-1 immune response and its regulation by Foxp3+ CD25 high T regulatory cells in the clinical course of this lung cancer patient. PMID:19791734

Isobe, Midori; Eikawa, Shingo; Uenaka, Akiko; Nakamura, Yoichi; Kanda, Tetsuo; Kohno, Shigeru; Kuzushima, Kiyotaka




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



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. PMID:23469329

Nguyen, Charles T.; Bota, Robert G.



Gaining Ground  

ERIC Educational Resources Information Center

In the 2006-07 school year, North Brunswick High School--a rural, racially and economically diverse high school in Leland, North Carolina--was identified as a priority school by the North Carolina Department of Public Instruction. Overall student proficiency was at 48.6%, indicating that less than one-half of all students earned a score of…

Newman, Leslie A.; Rollison, Margaret L.



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.



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



INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Behavior of gain-guided lasers generating high-power nanosecond pulses  

NASA Astrophysics Data System (ADS)

Computer-controlled apparatus was used in an investigation of gain-guided narrow-stripe AlGaAs double heterostructure lasers. These lasers were excited with current pulses of 10 ns duration and amplitudes up to 3 A. The watt-ampere characteristics together with near- and far-field radiation patterns were considered using an analytic model of the lasers. The results showed that the values of the gain under a stripe contact or of the absorption outside this region varied with the output power.

Erbert, G.



High-gain inner-shell photoionization laser in Cd vapor pumped by soft-x-ray radiation from a laser-produced plasma source.  


A soft-x-ray-pumped inner-shell photoionization laser has been produced in Cd vapor at 4416 and 3250 A. A gain of 5.6 cm(-1) has been measured at 4416 A, and a reasonably high-energy storage of 0.2 mJ/cm(3) in the upper laser states has been obtained. PMID:19718180

Silfvast, W T; Macklin, J J; Ii, O R



High-gain x-ray lasing at 11.1nm in sodiumlike copper driven by a 20-J, 2-ps Nd:glass laser  

SciTech Connect

Evidence of high gain pumped by recombination has been observed in the 5{ital g}{endash}4{ital f} transition at 11.1nm in sodiumlike copper ions with use of a 20-J 2-ps Nd:glass laser system. The time- and space-integrated gain coefficient was 8.8{plus_minus}1.4 cm{sup {minus}1}, indicating a single-transit amplification of {approximately}60 times. This experiment has shown that 2ps is the optimum pulse duration to drive the sodiumlike copper recombination x-ray lasing at 11.1nm. {copyright} {ital 1996 Optical Society of America.}

Zhang, J. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Fill, E.E.; Li, Y.; Schloegl, D.; Steingruber, J. [Max-Planck Institut fuer Quantenoptik, D-85740 Garching (Germany); Holden, M.; Tallents, G.J.; Demir, A.; Zeitoun, P. [Department of Physics, University of Essex, Colchester CO4 3SQ (United Kingdom); Danson, C.; Norreys, P.A.; Walsh, F. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX1 0QX (United Kingdom); Key, M.H. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom)]|[Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX1 0QX (United Kingdom); Lewis, C.L.; McPhee, A.G. [Department of Pure and Applied Physics, Queen`s University, Belfast BT7 1NN (United Kingdom)



Heavy ion beam ICF fusion: The thermodynamics of ignition and the achievement of high gain in ICF fusion targets  

Microsoft Academic Search

A model suitable for the calculation of gain in a fuel tamped inertial confinement fusion (ICF) target is developed. The model can be applied to targets driven by any suitable driver, lasers, ion beams, etc. As an example it is applied to a particular single shell, multilayer heavy ion beam target.

K. A. Long; N. A. Tahir



The dynamics of amplified spontaneous emission in CdSe/ZnSe quantum dots  

E-print Network

We have used the variable stripe technique and pump-probe spectroscopy to investigate both gain and the dynamics of amplified spontaneous emission from CdSe quantum dot structures. We have found modal gain coefficients of 75 and 32 1/cm for asymmetric and symmetric waveguide structures, respectively. Amplified spontaneous emission decay times of 150 and 300 ps and carrier capture times of 15 and 40 ps were measured for the structures with high and low material gains respectively. The difference in the capture times are related to the fact that for the symmetric waveguide, carriers diffuse into the active region from the uppermost ZnMgSSe cladding layer, yielding a longer rise time for the pump-probe signals for this sample.

Kundys, D O; Wells, J P R; Tartakovskii, A I; Skolnick, M S; Dang, Le Si; Lutsenko, E V; Tarasuk, N P; Lyublinskaya, O G; Toropov, A A; Ivanov, S V



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



Record efficiency and gain at 2.1 GHz of high power RF transistors for cellular and 3G base stations  

Microsoft Academic Search

Improved RF performance of Motorola's next generation HV6 high power RF-LDMOS transistor is demonstrated. In the 2.1 GHz band, with a two-carrier WCDMA signal, a 29% drain efficiency is achieved at -37 dBc IM3 and 20 W of output power, along with a high power gain of over 16.5 dB. To our knowledge, this is the highest combination of efficiency

H. Brech; W. Brakensiek; D. Burdeaux; W. Burger; C. Dragon; G. Formicone; B. Pryor; D. Rice



High CO2 concentration increases relative leaf carbon gain under dynamic light in Dipterocarpus sublamellatus seedlings in a tropical rain forest, Malaysia.  


Understory plants in tropical forests often experience a low-light environment combined with high CO2 concentration. We hypothesized that the high CO2 concentration may compensate for leaf carbon loss caused by the low light, through increasing light-use efficiency of both steady-state and dynamic photosynthetic properties. To test the hypothesis, we examined CO2 gas exchange in response to an artificial lightfleck in Dipterocarpus sublamellatus Foxw. seedlings under contrasting CO2 conditions: 350 and 700??mol?CO2?mol(-1) air in a tropical rain forest, Pasoh, Malaysia. Total photosynthetic carbon gain from the lightfleck was about double when subjected to the high CO2 when compared with the low CO2 concentration. The increase of light-use efficiency in dynamic photosynthesis contributed 7% of the increased carbon gain, most of which was due to reduction of photosynthetic induction to light increase under the high CO2. The light compensation point of photosynthesis decreased by 58% and the apparent quantum yield increased by 26% at the high CO2 compared with those at the low CO2. The study suggests that high CO2 increases photosynthetic light-use efficiency under both steady-state and fluctuating light conditions, which should be considered in assessing the leaf carbon gain of understory plants in low-light environments. PMID:25187569

Tomimatsu, Hajime; Iio, Atsuhiro; Adachi, Minaco; Saw, Leng-Guan; Fletcher, Christine; Tang, Yanhong



Effects of high temperature on growth and efficiency of male and female broilers from lines selected for high weight gain, favorable feed conversion, and high or low fat content.  


Male and female broiler chicks from five different broiler crosses (WI, LF, and HF = Israeli chicks selected for high body weight gain, and low and high abdominal fat, respectively; FC and WN = Dutch chicks selected for favorable feed conversion and high body weight gain, respectively) were raised at a high ambient temperature (32 to 33 C). Weight gain, protein and fat content in the carcass and feed, and protein efficiency were determined at 4, 6, and 8 wk of age. The effect of the high temperature was evaluated by comparing these data with those of similar chicks raised at a normal temperature (20 to 33 C) up to 6 wk of age. The reductions in body weight, protein gain, and feed and protein efficiency due to the high temperature increased with age and were much larger in males than in females. This trend was more pronounced in WI and WN chicks than in LF, HF, and FC chicks. Females of WI and WN crosses were as heavy as males at 6 wk and heavier at 8 wk. In LF, HF, and FC crosses, both sexes had similar weights at 8 wk. Growth reduction due to the high temperature was largest in the groups with the highest growth rate at the normal temperature (WI and WN males). Chicks with a lower growth rate and a higher capacity for energy storage in fat depots (all females, HF chicks), or a higher capacity for heat loss (FC chicks), were less affected by the high temperature. The results suggest that females should be preferred over males for broiler production in hot facilities or locations. Broiler genotypes selected for feed efficiency at the expense of fast growth may allow for a more profitable broiler production in high-temperature regions. PMID:1523174

Cahaner, A; Leenstra, F



Measurement of the gain profile of high-pressure Kr\\/O2 mixtures near 5577 A?  

Microsoft Academic Search

An intense relativistic electron beam (1.8 MeV, 100 ns, 4 kJ) was used to transversely excite a 50-cm-long laser cell containing 5200 Torr krypton and 10 Torr O2. Optical gain in the medium in the afterglow of the e-beam pulse was determined by measuring the decay of a 5-ns-long pulse from a carefully wavelength-tuned (±0.1 A?) narrow-band (0.04 A? FWHM)

Joseph R. Woodworth; James K. Rice



High-power 1.25 µm InAs QD VECSEL based on resonant periodic gain structure  

Microsoft Academic Search

We compare an InAs quantum dot (QD) vertical external-cavity surface-emitting laser (VECSEL) design consisting of 4 groups of 3 closely spaced QD layers with a resonant periodic gain (RPG) structure, where each of the 12 QD layers is placed at a separate field antinode. This increased the spacing between the QDs, reducing strain and greatly improving device performance. For thermal

Alexander R. Albrecht; Thomas J. Rotter; Christopher P. Hains; Andreas Stintz; Guofeng Xin; Tsuei-Lian Wang; Yushi Kaneda; Jerome V. Moloney; Kevin J. Malloy; Ganesh Balakrishnan



Lipoic acid prevents body weight gain induced by a high fat diet in rats: Effects on intestinal sugar transport  

Microsoft Academic Search

Several studies have suggested that oxidative stress might cause and aggravate the inflammatory state associated with obesity\\u000a and could be the link between excessive weight gain and its related disorders such as insulin resistance and cardiovascular\\u000a diseases. Thus, antioxidant treatment has been proposed as a therapy to prevent and manage obesity and associated complications.\\u000a Therefore, the aim of the present

P. L. Prieto-Hontoria; P. Pérez-Matute; M. Fernández-Galilea; A. Barber; J. A. Martínez; M. J. Moreno-Aliaga



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



Effect of Myostatin Depletion on Weight Gain, Hyperglycemia, and Hepatic Steatosis during Five Months of High-Fat Feeding in Mice  

PubMed Central

The marked hypermuscularity in mice with constitutive myostatin deficiency reduces fat accumulation and hyperglycemia induced by high-fat feeding, but it is unclear whether the smaller increase in muscle mass caused by postdevelopmental loss of myostatin activity has beneficial metabolic effects during high-fat feeding. We therefore examined how postdevelopmental myostatin knockout influenced effects of high-fat feeding. Male mice with ubiquitous expression of tamoxifen-inducible Cre recombinase were fed tamoxifen for 2 weeks at 4 months of age. This depleted myostatin in mice with floxed myostatin genes, but not in control mice with normal myostatin genes. Some mice were fed a high-fat diet (60% of energy) for 22 weeks, starting 2 weeks after cessation of tamoxifen feeding. Myostatin depletion increased skeletal muscle mass ?30%. Hypermuscular mice had ?50% less weight gain than control mice over the first 8 weeks of high-fat feeding. During the subsequent 3 months of high-fat feeding, additional weight gain was similar in control and myostatin-deficient mice. After 5 months of high-fat feeding, the mass of epididymal and retroperitoneal fat pads was similar in control and myostatin-deficient mice even though myostatin depletion reduced the weight gain attributable to the high-fat diet (mean weight with high-fat diet minus mean weight with low-fat diet: 19.9 g in control mice, 14.1 g in myostatin-deficient mice). Myostatin depletion did not alter fasting blood glucose levels after 3 or 5 months of high-fat feeding, but reduced glucose levels measured 90 min after intraperitoneal glucose injection. Myostatin depletion also attenuated hepatic steatosis and accumulation of fat in muscle tissue. We conclude that blocking myostatin signaling after maturity can attenuate some of the adverse effects of a high-fat diet. PMID:21390326

Burgess, Kerri; Xu, Tianshun; Brown, Roger; Han, Bajin; Welle, Stephen



Improving proliferation resistance of high breeding gain generation 4 reactors using blankets composed of light water reactor waste  

SciTech Connect

Fertile blankets can be used in fast reactors to enhance the breeding gain as well as the passive safety characteristics. However, such blankets typically result in the production of weapons grade plutonium. For this reason they are often excluded from Generation IV reactor designs. In this paper we demonstrate that using blankets manufactured directly from spent light water (LWR) reactor fuel it is possible to produce a plutonium product with non-proliferation characteristics on a par with spent LWR fuel of 30-50 MWd/kg burnup. The beneficial breeding and safety characteristics are retained. (authors)

Hellesen, C.; Grape, S.; Haakanson, A.; Jacobson Svaerd, S.; Jansson, P. [Division of Applied Nuclear Physics, Uppsala University, Aangstroemlaboratoriet Laegerhyddsvaegen 1, 751 20 Uppsala (Sweden)



Design of a high-gain laser diode-array pumped Nd:YAG alternating precessive slab amplifier (APS amplifier)  

NASA Astrophysics Data System (ADS)

In the design of space-qualifiable laser systems for ranging and altimetry, such as NASA's Geodynamic Laser Ranging System (GLRS), the transmitter must be kept small, powerful yet efficient, and must consist of as few components as possible. A novel preamplifier design is examined which requires no external beam steering optics, yielding a compact component with simple alignment procedures. The gains achieved are comparable to multipass zigzag amplifiers using two or more sets of external optics for extra passes through the amplifying medium.

Coyle, D. B.



Measurements of the Low Frequency Gain Fluctuations of a 30 GHz High-Electron-Mobility-Transistor Cryogenic Amplifier  

NASA Technical Reports Server (NTRS)

Low frequency gain fluctuations of a 30 GHz cryogenic HEMT amplifier have been measured with the input of the amplifier connected to a 15 K load. Effects of fluctuations of other components of the test set-up were eliminated by use of a power-power correlation technique. Strong correlation between output power fluctuations of the amplifier and drain current fluctuations of the transistors comprising the amplifier are observed. The existence of these correlations introduces the possibility of regressing some of the excess noise from the HEMT amplifier's output using the measured drain currents.

Jarosik, Norman



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


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



Coupling of ICRF waves and axial transport of high-energy ions owing to spontaneously excited waves in the GAMMA 10 tandem mirror  

NASA Astrophysics Data System (ADS)

Plasmas with high ion temperature of several kiloelectronvolts and a strong temperature anisotropy of greater than 10 were produced by ion cyclotron range of frequency (ICRF) heating in the GAMMA 10 tandem mirror. In such high-performance plasmas with strong anisotropy, high-frequency fluctuations, so-called Alfvén-ion-cyclotron (AIC) waves, are excited spontaneously. These AIC waves have several discrete peaks in the frequency spectrum. Coupling of the ICRF heating waves and the excited AIC waves was clearly observed in the density fluctuations measured with a newly developed reflectometer. Parametric decay from the heating ICRF waves to the AIC waves and low-frequency waves was also indicated. Alfvén waves with difference frequencies between the discrete peaks of the AIC waves were detected in a signal that measured the number of axially transported high-energy ions (over 6 keV) at the machine end, indicating pitch-angle scattering caused by the low-frequency waves. Energy transport along the magnetic field line is an important consideration when ICRF power is injected in the perpendicular direction to a magnetic field line. The importance of the spontaneously excited AIC waves for axial confinement of a tandem mirror through wave-wave couplings was demonstrated.

Ikezoe, R.; Ichimura, M.; Hirata, M.; Iwai, T.; Yokoyama, T.; Ugajin, Y.; Sato, T.; Iimura, T.; Saito, Y.; Yoshikawa, M.; Kohagura, J.; Shima, Y.; Imai, T.



Decentralized adaptive output-feedback stabilization of large-scale time-delay nonlinear systems with unknown high-frequency-gain signs  

Microsoft Academic Search

In this paper, we propose a decentralized adaptive output-feedback controller for a class of large-scale time-delay nonlinear systems with unknown high-frequency-gain signs. We establish global asymptotic stabilization results, without using Razumikhin Theorem or constructing Lyapunov-Krasovskii functionals. The paper enlarges the class of large-scale nonlinear systems for which global decentralized adaptive output- feedback controller can be designed.

Xudong Ye



Small-signal gain and kinetic processes on highly excited vibrational levels in active medium of pulsed first-overtone CO laser  

Microsoft Academic Search

Temporal behavior of small signal gain (SSG) for a frequency tunable first-overtone CO laser has been studied both experimentally and theoretically. The laser operates on highly excited vibrational transitions from 20->18 up to 38->36 that correspond to laser wavelength range between ~3 and 4 microns coinciding to atmospheric 'transparency window'. Maximum SSG comes up to 0.4 m-1. It is shown

Andrei A. Ionin; Andrei A. Kotkov; Yurii M. Klimachev; Leonid V. Seleznev; Dmitrii V. Sinitsyn; Alexander K. Kurnosov; Anatoly P. Napartovich; Sergei Shnyrev; Gordon D. Hager; John E. McCord



Excitation dependent two-component spontaneous emission and ultrafast amplified spontaneous emission in dislocation-free InGaN nanowires  

SciTech Connect

Amplified spontaneous emission (ASE) at 456 nm from In{sub 0.2}Ga{sub 0.8}N nanowires grown on (001) silicon by catalyst-free molecular beam epitaxy was observed at room temperature under femtosecond excitation. The photoluminescence spectra below ASE threshold consist of two spontaneous emission bands centered at {approx}555 nm and {approx}480 nm, respectively, revealing the co-existence of deeply and shallowly localized exciton states in the nanowires. The ASE peak emerges from the 480 nm spontaneous emission band when the excitation density exceeds {approx}120 {mu}J/cm{sup 2}, indicating that optical gain arises from the radiative recombination of shallowly localized excitons in the nanowires. Time-resolved photoluminescence measurements revealed that the ASE process completes within 1.5 ps, suggesting a remarkably high stimulated emission recombination rate in one-dimensional InGaN nanowires.

You, Guanjun; Zhang, Chunfeng; Xu, Jian [Department of Engineering Science and Mechanics, The Penn State University, University Park, Pennsylvania 16802 (United States)] [Department of Engineering Science and Mechanics, The Penn State University, University Park, Pennsylvania 16802 (United States); Guo, Wei; Bhattacharya, Pallab [Center for Nanoscale Photonics and Spintronics, University of Michigan, Ann Arbor, Michigan 48109 (United States)] [Center for Nanoscale Photonics and Spintronics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Henderson, Ron [Department of Physics and Astronomy, Middle Tennessee State University, Murfreesboro, Tennessee 37132 (United States)] [Department of Physics and Astronomy, Middle Tennessee State University, Murfreesboro, Tennessee 37132 (United States)



Investigation of the gain regimes and gain parameters of the free electron laser dispersion equation  

Microsoft Academic Search

The small signal gain curve and various gain parameters have been computed by solving numerically the generalized gain-dispersion equation of free electron lasers (FEL), which characterizes the conventional magnetic bremsstrahlung FEL, as well as a large number of other FEL devices. The method includes high gain, collective, and axial velocity spread effects, and some waveguide effects. The FEL gain regimes

E. Jerby; A. Gover



Spontaneous Resolution of Pneumocystis jirovecii Pneumonia on High-Resolution Computed Tomography in a Patient with Renal Cell Carcinoma.  


Background Spontaneous resolution of Pneumocystis jirovecii pneumonia has rarely been reported. Case Report A 59-year-old man presented to our hospital because of pyrexia (38°C) and shaking chills for 2 days. He had a history of right nephrectomy due to renal cell carcinoma and left upper lobectomy for lung metastasis in the last 1.5 years. Two months previously, he was treated with oral prednisolone (20 mg/day) plus the intravenous mTOR inhibitor, temsirolimus (25 mg/week), for brain metastasis. On radiological examination, thoracic computed tomography showed diffuse ground glass opacities spreading in bilateral middle to lower lung fields. Although transbronchial biopsy specimens and bronchoalveolar lavage fluid demonstrated the presence of accumulation of black-colored Pneumocystis jirovecii cysts in the lung, his chief complaints and radiological abnormalities disappeared completely with no treatment. This case demonstrates a unique clinical presentation of Pneumocystis jirovecii pneumonia, in that spontaneous resolution was noted on clinical and sequential radiological evaluations. Conclusions Increasing numbers of cytotoxic drugs and biological therapies have emerged, and changes in the immune status due to underlying diseases or administration of immunosuppressive drugs might affect the inflammatory process of Pneumocystis jirovecii pneumonia, as in the present case. PMID:25396336

Tanaka, Yasutaka; Saraya, Takeshi; Kurai, Daisuke; Ishii, Haruyuki; Takizawa, Hajime; Goto, Hajime



Spontaneous Resolution of Pneumocystis jirovecii Pneumonia on High-Resolution Computed Tomography in a Patient with Renal Cell Carcinoma  

PubMed Central

Patient: Male, 59 Final Diagnosis: Pneumocystis jirovecii pneumonia Symptoms: Low grade fever Medication: — Clinical Procedure: Transbronchial lung biopsy Specialty: Pulmonology Objective: Rare disease Background: Spontaneous resolution of Pneumocystis jirovecii pneumonia has rarely been reported. Case Report: A 59-year-old man presented to our hospital because of pyrexia (38°C) and shaking chills for 2 days. He had a history of right nephrectomy due to renal cell carcinoma and left upper lobectomy for lung metastasis in the last 1.5 years. Two months previously, he was treated with oral prednisolone (20 mg/day) plus the intravenous mTOR inhibitor, temsirolimus (25 mg/week), for brain metastasis. On radiological examination, thoracic computed tomography showed diffuse ground glass opacities spreading in bilateral middle to lower lung fields. Although transbronchial biopsy specimens and bronchoalveolar lavage fluid demonstrated the presence of accumulation of black-colored Pneumocystis jirovecii cysts in the lung, his chief complaints and radiological abnormalities disappeared completely with no treatment. This case demonstrates a unique clinical presentation of Pneumocystis jirovecii pneumonia, in that spontaneous resolution was noted on clinical and sequential radiological evaluations. Conclusions: Increasing numbers of cytotoxic drugs and biological therapies have emerged, and changes in the immune status due to underlying diseases or administration of immunosuppressive drugs might affect the inflammatory process of Pneumocystis jirovecii pneumonia, as in the present case. PMID:25396336

Tanaka, Yasutaka; Saraya, Takeshi; Kurai, Daisuke; Ishii, Haruyuki; Takizawa, Hajime; Goto, Hajime



Greater than 30-dB gain at 1500nm in S-band erbium-doped silica fiber with distributed ASE suppression  

NASA Astrophysics Data System (ADS)

S-band amplification with >30 dB peak gain at 1500 nm, >20 dB gain for wavelengths between 1475 nm and 1520 nm, and 5 dB noise figure is demonstrated in Erbium-doped Alumino-germanosilicate fiber. Using standard MCVD processing and solution doping, we combined a depressed-cladding fiber design with erbium doping to create a new type of gain fiber. A fundamental mode cutoff near 1530 nm provides distributed suppression of C-band amplified spontaneous emission, thereby enabling the high population inversion required for S-band gain. This type of S-band amplifier is compatible with standard fusion splicing techniques and is pumped by standard 980 nm pump lasers. In this talk, we will describe gain and noise characteristics for several amplifier architectures, gain saturation characteristics, and gain flattening.

Arbore, Mark A.; Zhou, Yidong; Keaton, Gregory; Kane, Thomas J.



Effects of low, normal, and high temperatures on slaughter yield of broilers from lines selected for high weight gain, favorable feed conversion, and high or low fat content.  


Male and female broiler chicks from five different broiler crosses (WI = Israeli chicks selected for increased body weight; LF and HF = Israeli chicks selected for low and high abdominal fat, respectively; FC and WN = Dutch chicks selected for improved feed conversion and increased body weight, respectively) were raised at low, normal, or high temperature. Slaughter yield, amount of breast meat, and abdominal fat were determined at 6 wk of age in all groups and at a body weight of 2,360 g for males and 1,965 g for females in the low- and normal-temperature groups, and at 8 wk in the high-temperature groups. Temperature, genotype, and sex influenced both absolute and relative weights of carcass, breast meat, and abdominal fat. Temperature had a negative effect on breast meat yield. Males were affected more by high temperature than females. A significant interaction between temperature and sex for breast meat yield was caused by a low yield for males at the high temperature. A similar interaction for proportion of abdominal fat was caused by a high fat content in males reared at the high temperature. Slaughter yield and especially yield of breast meat were highest in FC chickens in all comparisons. PMID:1470585

Leenstra, F; Cahaner, A



HiPER target studies: towards the design of high gain, robust, scalable direct-drive targets with advanced ignition schemes  

NASA Astrophysics Data System (ADS)

An essential element of the HiPER project is the design of high gain targets, compatible with high repetition-rate operation and that can be mass produced at low cost. HiPER WP9 (Work Package 9 Requirements analysis for the fusion programme) studied schemes based on direct laser irradiation and advanced ignition (fast ignition and shock ignition), which have potentials for gain in excess of 100 at laser energy of about 1 MJ. To begin with, a very simple target was designed, which could allow for ignition demonstration with a few hundred kJ laser, and can be scaled at higher energy and gain. The ignition requirements have been determined, and crucial issues have been identified. This led to select shock ignition as the main option, since it turns out that all the relevant issues could be tested experimentally at existing facilities in the present decade. WP9 investigated irradiation schemes, target symmetry and stability issues, sensitivity to parameter changes, requirements for beam delivery and focusing and target positioning. Current work is directed towards increasing target robustness, scaling to greater energy, and designing targets for full scale demonstration.

Atzeni, S.; Schurtz, G.



High Rates of Hepatitis C Virus Reinfection and Spontaneous Clearance of Reinfection in People Who Inject Drugs: A Prospective Cohort Study  

PubMed Central

Hepatitis C virus reinfection and spontaneous clearance of reinfection were examined in a highly characterised cohort of 188 people who inject drugs over a five-year period. Nine confirmed reinfections and 17 possible reinfections were identified (confirmed reinfections were those genetically distinct from the previous infection and possible reinfections were used to define instances where genetic differences between infections could not be assessed due to lack of availability of hepatitis C virus sequence data). The incidence of confirmed reinfection was 28.8 per 100 person-years (PY), 95%CI: 15.0-55.4; the combined incidence of confirmed and possible reinfection was 24.6 per 100 PY (95%CI: 16.8-36.1). The hazard of hepatitis C reinfection was approximately double that of primary hepatitis C infection; it did not reach statistical significance in confirmed reinfections alone (hazard ratio [HR]: 2.45, 95%CI: 0.87-6.86, p=0.089), but did in confirmed and possible hepatitis C reinfections combined (HR: 1.93, 95%CI: 1.01-3.69, p=0.047) and after adjustment for the number of recent injecting partners and duration of injecting. In multivariable analysis, shorter duration of injection (HR: 0.91; 95%CI: 0.83-0.98; p=0.019) and multiple recent injecting partners (HR: 3.12; 95%CI: 1.08-9.00, p=0.035) were independent predictors of possible and confirmed reinfection. Time to spontaneous clearance was shorter in confirmed reinfection (HR: 5.34, 95%CI: 1.67-17.03, p=0.005) and confirmed and possible reinfection (HR: 3.10, 95%CI: 1.10-8.76, p-value=0.033) than primary infection. Nonetheless, 50% of confirmed reinfections and 41% of confirmed or possible reinfections did not spontaneously clear. Conclusions: Hepatitis C reinfection and spontaneous clearance of hepatitis C reinfection were observed at high rates, suggesting partial acquired natural immunity to hepatitis C virus. Public health campaigns about the risks of hepatitis C reinfection are required. PMID:24244654

Sacks-Davis, Rachel; Aitken, Campbell K.; Higgs, Peter; Spelman, Tim; Pedrana, Alisa E.; Bowden, Scott; Bharadwaj, Mandvi; Nivarthi, Usha K.; Suppiah, Vijayaprakash; George, Jacob; Grebely, Jason; Drummer, Heidi E.; Hellard, Margaret



Spontaneous fourfold-symmetry breaking driven by electron-lattice coupling and strong correlations in high-$T_c$ cuprates  

SciTech Connect

Using dynamical-mean-field theory for clusters, we study the two-dimensional Hubbard model in which electrons are coupled with the orthorhombic lattice distortions through the modulation in the hopping matrix. Instability towards spontaneous symmetry breaking from a tetragonal symmetric phase to an orthorhombic distorted phase is examined as a function of doping and interaction strength. A very strong instability is found in the underdoped pseudogap regime when the interaction strength is large enough to yield the Mott insulating phase at half filling. The symmetry breaking accompanies the recovery of quasiparticle weights along one of the two antinodal directions, leading to the characteristic Fermi arc reconnection.We discuss the implications of our results to the fourfold symmetry breaking reported in systems where the underlying crystal does not have any structural anisotropy.

Okamoto, Satoshi [ORNL; Furukawa, N. [Aoyama Gakuin University, Kanagawa, Japan



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. PMID:23593029

St. Charles, Jordan; Petes, Thomas D.



Spontaneous facial motility in infancy: A 3D kinematic analysis  

Microsoft Academic Search

Early spontaneous orofacial movements have rarely been studied experimentally, though the motor experiences gained from these behaviors may influence the development of motor skills emerging for speech. This investigation quantitatively describes developmental changes in silent, spontaneous lip and jaw movements from 1 to 12 months of age using optically based 3D motion capture technology. Twenty-nine typically developing infants at five

Jordan R. Green; Erin M. Wilson



Spontaneous thoracic duct cyst.  


Spontaneous and asymptomatic supraclavicular thoracic duct cysts (lymphoceles ) are rare. Only five cases have been reported so far. They are more common after surgery or trauma and have been reported in the abdomen, mediastinum, pelvis and neck. They must be differentiated from other neck cysts as failure to recognise their attachment may result in the disastrous consequence of chylothorax. A high index of suspicion is necessary, and diagnosis usually can be established by fine-needle aspiration and suitable imaging. This case is reported along with a review of the literature and management options, including that of inadvertent damage to the thoracic duct. PMID:12750920

Ray, J; Braithwaite, D; Patel, P J



Investigation of the gain regimes and gain parameters of the free electron laser dispersion equation  

NASA Astrophysics Data System (ADS)

The small signal gain curve and various gain parameters have been computed by solving numerically the generalized gain-dispersion equation of free electron lasers (FEL), which characterizes the conventional magnetic bremsstrahlung FEL, as well as a large number of other FEL devices. The method includes high gain, collective, and axial velocity spread effects, and some waveguide effects. The FEL gain regimes are investigated and presented in terms of only three universal FEL characteristic parameters. The approximative analytic gain expressions are compared to the numerical computation results, and the approximation error is computed and displayed. In the intermediate regimes (high-low gain, tenuous-collective beam, cold-warm beam), the gain parameters are given in terms of useful curves, and a heuristic approximative formula is suggested for estimating the axial velocity spread gain reduction factor in all gain regimes. Gain bandwidth and beam quality acceptance parameters are defined and computed in all gain regimes.

Jerby, E.; Gover, A.



Significant progression of load on the musculoskeletal system with extremely high loads, with rapid weekly weight gains, using the Anatoly Gravitational System, in a 10-week training period  

PubMed Central

In an age of increasing numbers of lifestyle diseases and plasticity of longevity, exercise and weight training have been increasingly recognized as both preventing and mitigating the severity of many illnesses. This study was designed to determine whether significant weight-lifting gains could be realized through the Anatoly Gravitational System. Specifically, this study sought to determine whether this once-weekly weight-training system could result in significant weekly strength gains during a 10-week training period. A total of 50 participants, ranging in age from 17 to 67 years, completed at least 10 weekly 30-minute training sessions. The results suggest participants could, on average, double their weight-lifting capacity within 10 sessions. This preliminary study, which would require further scrutiny, suggests the Anatoly Gravitational System provides a rather unique opportunity to load the musculoskeletal system with extremely high loads, with rapid weekly weight gains, using only short weekly training sessions. More studies are warranted to scrutinize these findings. PMID:24379727

Burke, David T; Tran, David; Cui, Di; Burke, Daniel P; Al-Adawi, Samir; Dorvlo, Atsu SS



Significant progression of load on the musculoskeletal system with extremely high loads, with rapid weekly weight gains, using the Anatoly Gravitational System, in a 10-week training period.  


In an age of increasing numbers of lifestyle diseases and plasticity of longevity, exercise and weight training have been increasingly recognized as both preventing and mitigating the severity of many illnesses. This study was designed to determine whether significant weight-lifting gains could be realized through the Anatoly Gravitational System. Specifically, this study sought to determine whether this once-weekly weight-training system could result in significant weekly strength gains during a 10-week training period. A total of 50 participants, ranging in age from 17 to 67 years, completed at least 10 weekly 30-minute training sessions. The results suggest participants could, on average, double their weight-lifting capacity within 10 sessions. This preliminary study, which would require further scrutiny, suggests the Anatoly Gravitational System provides a rather unique opportunity to load the musculoskeletal system with extremely high loads, with rapid weekly weight gains, using only short weekly training sessions. More studies are warranted to scrutinize these findings. PMID:24379727

Burke, David T; Tran, David; Cui, Di; Burke, Daniel P; Al-Adawi, Samir; Dorvlo, Atsu Ss



High-Fat-Diet-Induced Weight Gain Ameliorates Bone Loss without Exacerbating A?PP Processing and Cognition in Female APP/PS1 Mice  

PubMed Central

Osteoporosis is negatively correlated with body mass, whereas both osteoporosis and weight loss occur at higher incidence during the progression of Alzheimer’s disease (AD) than the age-matched non-dementia individuals. Given that there is no evidence that being overweight is associated with AD-type cognitive dysfunction, we hypothesized that moderate weight gain might have a protective effect on the bone loss in AD without exacerbating cognitive dysfunction. In this study, feeding a high-fat diet (HFD, 45% calorie from fat) to female APP/PS1 transgenic mice, an AD animal model, induced weight gain. The bone mineral density, microarchitecture, and biomechanical properties of the femurs were then evaluated. The results showed that the middle-aged female APP/PS1 transgenic mice were susceptible to osteoporosis of the femoral bones and that weight gain significantly enhanced bone mass and mechanical properties. Notably, HFD was not detrimental to brain insulin signaling and A?PP processing, as well as to exploration ability and working, learning, and memory performance of the transgenic mice measured by T maze and Morris water maze, compared with the mice fed a normal-fat diet (10% calorie from fat). In addition, the circulating levels of leptin but not estradiol were remarkably elevated in HFD-treated mice. These results suggest that a body weight gain induced by the HFD feeding regimen significantly improved bone mass in female APP/PS1 mice with no detriments to exploration ability and spatial memory, most likely via the action of elevated circulating leptin. PMID:25152713

Peng, Yunhua; Liu, Jing; Tang, Ying; Liu, Jianshu; Han, Tingting; Han, Shujun; Li, Hua; Hou, Chen; Liu, Jiankang; Long, Jiangang



Weak FEL Gain Detection with a Modulated Laser-Based Beam Heater  

Microsoft Academic Search

For an x-ray free-electron laser (FEL) such as the LCLS, the FEL gain signal is accompanied by spontaneous radiation with a significant power level. Detecting the weak FEL gain among the large spontaneous background in the early stage of the exponential growth or for a low quality electron beam is important in commissioning the FEL. In this paper, we describe

P. Emma; Z. Huang; J. Wu



Demonstration of high-power and stable C-band and L-band erbium-doped fiber amplified spontaneous emission sources using multipumping configuration  

NASA Astrophysics Data System (ADS)

We have investigated and experimentally demonstrated high-power and stable C-band and L-band erbium-doped fiber amplified spontaneous emission (ASE) sources using a multipumping configuration, which can provide an output power of 27.16 dBm (519.99 mW) and 27.34 dBm (542.01 mW) with a power ripple of 5.9 and 1.1 dB for C-band and L-band without adding any external spectra-flattening components. Moreover, the averaged power stability of C-band and L-band erbium-doped fiber ASE source with +/-0.005 and +/-0.003 dB during an 8-h interval measurements at the room temperature 25 °C can be achieved, allowing high pumping efficiency of 38.5 and 36.9%.

Chang, Chia-Hsiung; Liang, Tsair-Chun



Spontaneous Intratesticular Haemorrhage  

Microsoft Academic Search

Spontaneous intratesticular haemorrhage is a rare disease. Four cases have been described, all diagnosed after orchidectomy. We present an additional patient with a spontaneously arisen intratesticular haematoma in whom orchidectomy could be avoided.

Per Ovesen; Søren Mommsen



Less Pain and More to Gain: Why High-Status Group Members Blame Their Failure on Discrimination  

Microsoft Academic Search

Members of high-status groups are more likely than members of low-status groups to blame their failure on discrimination and are less likely to blame it on themselves. This tendency was demonstrated in 3 experiments comparing men and women, White and Black students, and members of experimentally created high- and low-status groups. Results also showed that when making an attribution to

Karen M. Ruggiero; David M. Marx



High-gain inertial confinement fusion by volume ignition, avoiding the complexities of fusion detonation fronts of spark ignition  

Microsoft Academic Search

Summary form only given, as follows. The main approach to inertial confinement fusion (ICF) uses a high-temperature, low-density core and a high-density, low-temperature outer region of the laser(or ion beam-) compressed deuterium-tritium (D-T) fuel, in order to ignite a fusion detonation wave at the interface. This is an extremely delicate, unstable configuration which is very difficult to achieve, even with

H. Hora; S. Eliezer; J. J. Honrubia; R. Hopfl; J. M. Martinez-Val; G. H. Miley; G. Velarde



Porcine Adiponectin Receptor 1 Transgene Resists High-fat/Sucrose Diet-Induced Weight Gain, Hepatosteatosis and Insulin Resistance in Mice  

PubMed Central

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



High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm  

Microsoft Academic Search

We demonstrate a pulsed ytterbium-doped fiber master-oscillator power amplifier source at 1060 nm producing over 300 W of average power in 20-ps pulses at 1-GHz repetition rate. The pulses generated by a gain-switched diode were compressed by a chirped fiber Bragg grating and amplified without any distortion with excellent spectral quality. This fiber master oscillator power amplifier system offers versatility

P. Dupriez; A. Piper; A. Malinowski; J. K. Sahu; M. Ibsen; B. C. Thomsen; Y. Jeong; L. M. B. Hickey; M. N. Zervas; J. Nilsson; D. J. Richardson



Analytic modeling of Brillouin gain in rare-earth doped fiber amplifiers with high-power single-frequency signals  

Microsoft Academic Search

The effect of temperature variation along a high power fiber amplifier on the SBS threshold is considered theoretically. We show that for an end-pumped rare-earth doped double-clad fiber the inhomogeneous distribution of temperature, which is caused by absorption of pump radiation, may result in total suppression of SBS even for output powers well above 200 W.

V. I. Kovalev; R. G. Harrison; J. Nilsson; Y. Jeong; V. Hernandes-Solis; J. K. Sahu



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.



Transform-Limited X-Ray Pulse Generation from a High Brightness Self-Amplified Spontaneous Emission Free-Electron Laser  

E-print Network

A method to achieve High-Brightness Self-Amplified Spontaneous Emission (HB-SASE) in the Free Electron Laser (FEL) is described. The method uses repeated non-equal electron beam delays to de-localise the collective FEL interaction and break the radiation coherence length dependence on the FEL cooperation length. The method requires no external seeding or photon optics and so is applicable at any wavelength or repetition rate. It is demonstrated using linear theory and numerical simulations that the radiation coherence length can be increased by approximately two orders of magnitude over SASE with a corresponding increase in spectral brightness. Examples are shown of HB-SASE generating transform-limited FEL pulses in the soft X-ray and near transform-limited pulses in the hard X-ray. Such pulses may greatly benefit existing applications and may also open up new areas of scientific research.

McNeil, B W J; Dunning, D J



Femtosecond high-power spontaneous mode-locked operation in vertical-external cavity surface-emitting laser with gigahertz oscillation.  


We realize a femtosecond high-power spontaneous mode-locked operation with gigahertz oscillation in a vertical-external cavity surface-emitting laser under the condition of eliminating the internal and external unwanted reflection. We find that the reflectivity of the output coupler has a significant influence not only on the output power but also on the output pulse duration. With an incident pump power of 20 W, we have achieved 2.35 W of average output power with 778 fs pulse duration at a repetition rate of 2.17 GHz. The shortest pulse duration was 654 fs at an average output power of 0.45 W. PMID:22139249

Chen, Y F; Lee, Y C; Liang, H C; Lin, K Y; Su, K W; Huang, K F



Identification of spontaneous and deliberate behavior  

Microsoft Academic Search

The present research investigates the accuracy of decoding spontaneous (natural or unintentional) and deliberate (posed or intentional) nonverbal behavior. Previous research has suggested that spontaneous and deliberate nonverbal cues are highly similar if not identical, implying that observers cannot discriminate accurately between the two types of behavior. But this conclusion is based on the decoding of information about content, without

Vernon L. Allen; Michael L. Atkinson



Spectroscopic and microscopic studies of self-assembled nc-Si/a-SiC thin films grown by low pressure high density spontaneous plasma processing.  


In view of suitable applications in the window layer of nc-Si p-i-n solar cells in superstrate configuration, the growth of nc-Si/a-SiC composite films was studied, considering the trade-off relation between individual characteristics of its a-SiC component to provide a wide optical-gap and electrically conducting nc-Si component to simultaneously retain enough crystalline linkages to facilitate proper crystallization to the i-nc-Si absorber-layer during its subsequent growth. Self-assembled nc-Si/a-SiC thin films were spontaneously grown by low-pressure planar inductively coupled plasma CVD, operating in electromagnetic mode, providing high atomic-H density. Spectroscopic simulations of ellipsometry and Raman data, and systematic chemical and structural analysis by XPS, TEM, SEM and AFM were performed. Corresponding to optimized inclusion of C essentially incorporated as Si-C bonds in the network, the optical-gap of the a-SiC component widened, void fraction including the incubation layer thickness reduced. While the bulk crystallinity decreased only marginally, Si-ncs diminished in size with narrower distribution and increased number density. With enhanced C-incorporation, formation of C-C bonds in abundance deteriorates the Si continuous bonding network and persuades growth of an amorphous dominated silicon-carbon heterostructure containing high-density tiny Si-ncs. Stimulated nanocrystallization identified in the Si-network, induced by a limited amount of carbon incorporation, makes the material most suitable for applications in nc-Si solar cells. The novelty of the present work is to enable spontaneous growth of self-assembled superior quality nc-Si/a-SiC thin films and simultaneous spectroscopic simulation-based optimization of properties for utilization in devices. PMID:25342429

Das, Debajyoti; Kar, Debjit



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)



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



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 cm 2 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



A mitochondrial-targeted coenzyme q analog prevents weight gain and ameliorates hepatic dysfunction in high-fat-fed mice.  


We hypothesized that the mitochondrial-targeted antioxidant, mitoquinone (mitoQ), known to have mitochondrial uncoupling properties, might prevent the development of obesity and mitigate liver dysfunction by increasing energy expenditure, as opposed to reducing energy intake. We administered mitoQ or vehicle (ethanol) to obesity-prone C57BL/6 mice fed high-fat (HF) or normal-fat (NF) diets. MitoQ (500 µM) or vehicle (ethanol) was added to the drinking water for 28 weeks. MitoQ significantly reduced total body mass and fat mass in the HF-fed mice but had no effect on these parameters in NF mice. Food intake was reduced by mitoQ in the HF-fed but not in the NF-fed mice. Average daily water intake was reduced by mitoQ in both the NF- and HF-fed mice. Hypothalamic expression of neuropeptide Y, agouti-related peptide, and the long form of the leptin receptor were reduced in the HF but not in the NF mice. Hepatic total fat and triglyceride content did not differ between the mitoQ-treated and control HF-fed mice. However, mitoQ markedly reduced hepatic lipid hydroperoxides and reduced circulating alanine aminotransferase, a marker of liver function. MitoQ did not alter whole-body oxygen consumption or liver mitochondrial oxygen utilization, membrane potential, ATP production, or production of reactive oxygen species. In summary, mitoQ added to drinking water mitigated the development of obesity. Contrary to our hypothesis, the mechanism involved decreased energy intake likely mediated at the hypothalamic level. MitoQ also ameliorated HF-induced liver dysfunction by virtue of its antioxidant properties without altering liver fat or mitochondrial bioenergetics. PMID:25301169

Fink, Brian D; Herlein, Judith A; Guo, Deng Fu; Kulkarni, Chaitanya; Weidemann, Benjamin J; Yu, Liping; Grobe, Justin L; Rahmouni, Kamal; Kerns, Robert J; Sivitz, William I



Vaccination against weight gain  

PubMed Central

Obesity endangers the lives of millions of people worldwide, through comorbidities such as heart disease, cancers, type 2 diabetes, stroke, arthritis, and major depression. New approaches to control body weight remain a high priority. Vaccines traditionally have been used to protect against infectious diseases and, more recently, for unconventional targets such as drug addiction. Methodologies that could specifically modulate the bioavailability of an endogenous molecule that regulates energy balance might provide a new foundation for treating obesity. Here we show that active vaccination of mature rats with ghrelin immunoconjugates decreases feed efficiency, relative adiposity, and body weight gain in relation to the immune response elicited against ghrelin in its active, acylated form. Three active vaccines based on the 28-aa residue sequence of ghrelin, a gastric endocrine hormone, were used to immunize adult male Wistar rats (n = 17). Synthetic ghrelin analogs were prepared that spanned residues 1–10 [ghrelin (1–10) Ser-3(butanoyl) hapten, Ghr1], 13–28 [ghrelin (13–28) hapten, Ghr2], and 1–28 [ghrelin(1–28) Ser-3(butanoyl) hapten, Ghr3], and included n-butanoyl esters at Ser-3. Groups immunized with Ghr1 or Ghr3 showed greater and more selective plasma binding capacity for the active, Ser-3-(n-octanoyl) form of ghrelin as compared with Ghr2 or keyhole limpet hemocyanin vaccinated controls. Accordingly, they gained less body weight, with sparing of lean mass and preferential reduction of body fat, consistent with reduced circulating leptin levels. The ratio of brain/serum ghrelin levels was lower in rats with strong anti-ghrelin immune responses. Effects were not attributable to nonspecific inflammatory responses. Vaccination against the endogenous hormone ghrelin can slow weight gain in rats by decreasing feed efficiency. PMID:16891413

Zorrilla, Eric P.; Iwasaki, Shinichi; Moss, Jason A.; Chang, Jason; Otsuji, Jonathan; Inoue, Koki; Meijler, Michael M.; Janda, Kim D.



Spaceliner Class Operability Gains Via Combined Airbreathing/ Rocket Propulsion: Summarizing an Operational Assessment of Highly Reusable Space Transports  

NASA Technical Reports Server (NTRS)

In discussing a new NASA initiative in advanced space transportation systems and technologies, the Director of the NASA Marshall Space Flight Center, Arthur G. Stephenson, noted that, "It would use new propulsion technology, air-breathing engine so you don't have to carry liquid oxygen, at least while your flying through the atmosphere. We are calling it Spaceliner 100 because it would be 100 times cheaper, costing $ 100 dollars a pound to orbit." While airbreathing propulsion is directly named, rocket propulsion is also implied by, "... while you are flying through the atmosphere." In-space final acceleration to orbital speed mandates rocket capabilities. Thus, in this informed view, Spaceliner 100 will be predicated on combined airbreathing/rocket propulsion, the technical subject of this paper. Interestingly, NASA's recently concluded Highly Reusable Space Transportation (HRST) study focused on the same affordability goal as that of the Spaceliner 100 initiative and reflected the decisive contribution of combined propulsion as a way of expanding operability and increasing the design robustness of future space transports, toward "aircraft like" capabilities. The HRST study built on the Access to Space Study and the Reusable Launch Vehicle (RLV) development activities to identify and characterize space transportation concepts, infrastructure and technologies that have the greatest potential for reducing delivery cost by another order of magnitude, from $1,000 to $100-$200 per pound for 20,000 lb. - 40.000 lb. payloads to low earth orbit (LEO). The HRST study investigated a number of near-term, far-term, and very far-term launch vehicle concepts including all-rocket single-stage-to-orbit (SSTO) concepts, two-stage-to-orbit (TSTO) concepts, concepts with launch assist, rocket-based combined cycle (RBCC) concepts, advanced expendable vehicles, and more far term ground-based laser powered launchers. The HRST study consisted of preliminary concept studies, assessments and analysis tool development for advanced space transportation systems, followed by end-to-end system concept definitions and trade analyses, specific system concept definition and analysis, specific key technology and topic analysis, system, operational and economics model development, analysis, and integrated assessments. The HRST Integration Task Force (HITF) was formed to synthesize study results in several specific topic areas and support the development of conclusions from the study: Systems Concepts Definitions, Technology Assessment, Operations Assessment, and Cost Assessment. This paper summarizes the work of the Operations Assessment Team: the six approaches used, the analytical tools and methodologies developed and employed, the issues and concerns, and the results of the assessment. The approaches were deliberately varied in measures of merit and procedure to compensate for the uncertainty inherent in operations data in this early phase of concept exploration. In general, rocket based combined cycle (RBCC) concepts appear to have significantly greater potential than all-rocket concepts for reducing operations costs.

Nix, Michael B.; Escher, William J. d.



Telecommunicating and Spontaneous Interaction  

Microsoft Academic Search

\\u000a This chapter investigates how spontaneous interaction is affected by telecommuting. By using work diaries to collect data\\u000a on time spent on spontaneous interaction, two groups are studied, one working form a remote location for part of the time,\\u000a and one working at one location. The assumption is that spontaneous interaction is either constant during time of co-presence,\\u000a or it is

Jon Rognes


The design criteria of hybrid waveguides using semiconductor gain to compensate the metal loss towards nano-scale lasers with high plasmonicity  

NASA Astrophysics Data System (ADS)

In this Letter, we report on the design criteria of plasmonic nano-lasers based on hybrid waveguides using semiconductor gain to compensate for the metal loss. A quantitative measure of the plasmonic-like character in nano-lasers was discussed with the distance of operation wavelength to plasmon resonance, herein defined as "plasmonicity" ( ? = ? / ? sp). We found that the effective index (confinement) increased with plasmonicity rapidly when approaching resonance and the associated giant modal loss prohibited lasing. We further studied the design criteria of a practicable green nano-laser, based on a vertical p-n junction combined with a lateral semiconductor/dielectric/metal core-shell structure. The influence of thickness and permittivity of dielectric spacer and also the critical thickness of the active region were investigated numerically. The approach proposed here will shed light on the future fabrication of electrical injection nano-lasers with high plasmonicity.

Yang, Wei; Zong, Hua; Ji, Qingbin; Yan, Tongxing; Hu, Xiaodong



High power tunable picosecond green laser pulse generation by frequency doubling of an Yb-doped fiber power amplifier seeded by a gain switch laser diode  

NASA Astrophysics Data System (ADS)

A compact tunable high power picosecond green laser pulse source based on frequency doubling of an Yb-doped fiber amplifier seeded by a gain switch laser diode has been developed. The fiber amplifier generates the picosecond infrared pulses with average power of 10.3 W, repetition rate of 1 MHz, pulse duration of 150 ps, and tunable range of 20 nm around 1064 nm. For underwater use, the tunable output infrared pulses are frequency doubled into picosecond green laser pulses, which can be tuned from 527 to 537 nm with average power of more than 1.1 W, corresponding to an overall conversion efficiency of 10.7% by a BBO nonlinear crystal. This kind of laser source will have potential application for underwater optical communication.

Liu, H. J.; Li, X. F.



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


We investigated the effect of dietary supplementation with selenium on spontaneous metastasis of Lewis lung carcinoma in mice fed a high-fat diet. Mice were fed a low-fat diet or that diet modified with 45% of calories from corn oil and supplemented with 0 or 2.5mg selenium/4029 kcal as methylseleninic acid. After 6 weeks, mice were each injected 2.5 × 10(5) Lewis lung carcinoma cells subcutaneously. The resulting primary tumor was removed surgically 10 days later; the experiment was terminated after an additional 10 days. High-fat feeding increased pulmonary metastases by 17% compared to the low-fat diet (P < 0.01). Selenium supplementation reduced the metastases by 11% compared to nonsupplemented controls (P < 0.05); the reduction was less for animals fed the high-fat diet (5%) than for those fed the low-fat diet (18%). Supplemental Se lowered plasma concentrations of proteases (urokinase plasminogen activator, P < 0.01; matrix metalloproteinase-9, P < 0.05) and angiogenic factors (vascular endothelial growth factor, P < 0.01; tissue inhibitor of metalloproteinase-1, P < 0.01) compared to nonsupplemented controls. High-fat feeding increased plasma concentrations of adipokines plasminogen activator inhibitor-1, monocyte chemotactic protein-1, tumor necrosis factor-?, and leptin regardless of the level of dietary selenium; supplemental selenium lowered plasma concentrations of plasminogen activator inhibitor-1 (P ? 0.05) and monocyte chemotactic protein-1 (P ? 0.05) in low-fat fed mice but not in high-fat fed mice. These results indicate that consumption of a high-fat diet abrogated the antimetastatic effects of selenium by increasing the expression of adipose-derived inflammatory cytokines. PMID:25053624

Yan, Lin; Combs, Gerald F



Dynamic-performance characterization of C-band EDFA using ASE-power peak-selective feedback gain-clamping  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a C-band Erbium-doped fiber amplifier (EDFA) using amplified spontaneous emission (ASE) power peaking-selective and feedback to achieve highly stabilized and wide dynamic range gain clamping performances. The gain of 16.20 ± 0.13 dB is obtained with the input signal power dynamic range of 30 dB and the maximum noise figure (NF) was 6.6 dB with the input signal power from -35 to -10 dBm. To investigate the gain variation for the probe signals, we applied a saturation tone signal to simulate 16-channel DWDM signals as it is added (dropped) into (from) EDFA. The gain variation of the proposed scheme at a appropriate ring-cavity loss (VOA = 5 dB) is less than 0.13 dB for the input signal power from -35 to -5 dBm and wavelength from 1530 to 1564 nm.

Lin, J. M.; Ho, W. J.



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

ERIC Educational Resources Information Center

The author of EC 606 782 reflects on aspects of the elaborative interrogation strategy evaluated with high achieving fifth- and sixth-grade students, noting the importance of an extensive knowledge base for using this strategy and the likelihood that the strategy is inappropriate for low achievers. (Author/DB)

Wood, Eileen; And Others



High photon number path entanglement in the interference of spontaneously downconverted photon pairs with coherent laser light  

E-print Network

We show that the quantum interference between downconverted photon pairs and photons from coherent laser light can produce a maximally path entangled N-photon output component with a fidelity greater than 90% for arbitrarily high photon numbers. A simple beam splitter operation can thus transform the 2-photon coherence of down-converted light into an almost optimal N-photon coherence.

Holger F. Hofmann; Takafumi Ono



Effects of a High-Fat Diet on Spontaneous Metastasis of Lewis Lung Carcinoma in Plasminogen Activator Inhibitor-1 Deficient and Wild-Type Mice  

PubMed Central

This study investigated the effects of a high-fat diet on spontaneous metastasis of Lewis lung carcinoma (LLC) in plasminogen activator inhibitor-1 deficient (PAI-1?/?) and wild-type mice. The high-fat diet increased the number of pulmonary metastases by 60% (p<0.01), tumor cross-sectional area by 82% (p<0.05) and tumor volume by 130% (p<0.05) compared to the AIN93G diet. Deficiency in PAI-1 reduced the number of metastases by 35% (p<0.01) compared to wild-type mice. In mice fed the high-fat diet, PAI-1 deficiency reduced tumor cross-sectional area by 52% (p<0.05) and tumor volume by 61% (p<0.05) compared to their wild-type counterparts; however, PAI-1 deficiency affected neither area nor volume in mice fed the AIN93G diet. Adipose and plasma concentrations of PAI-1 were significantly higher in high-fat fed wild-type mice than in their AIN93G-fed counterparts. Adipose and plasma PAI-1 were not detectable in PAI-1?/? mice regardless of the diet. Mice deficient in PAI-1 showed significantly greater plasma concentrations of monocyte chemotactic protein-1, tumor necrosis factor-?, leptin, vascular endothelial growth factor, tissue inhibitor of metalloproteinase-1 and insulin compared to wild-type mice, indicating a compensatory overproduction of inflammatory cytokines, angiogenic factors and insulin in the absence of PAI-1. We conclude that PAI-1 produced by the host, including that by adipose tissue, promotes high-fat enhanced metastasis of LLC. PMID:25356654

Yan, Lin; DeMars, Lana C.



High peak- and average-power pulse shaped fiber laser in the ns-regime applying step-index XLMA gain fibers  

NASA Astrophysics Data System (ADS)

Pulsed fiber lasers and continuous-wave (cw) fiber lasers have become the tool of choice in more and more laser based industrial applications like metal cutting and welding mainly because of their robustness, compactness, high brightness, high efficiency and reasonable costs. However, to further increase the productivity with those laser types there is a great demand for even higher laser power specifications. In this context we demonstrate a pulsed high peak- and averagepower fiber laser in a Master Oscillator Power Amplifier (MOPA) configuration with selectable pulse durations between 1 ns and several hundred nanoseconds. To overcome fiber nonlinearities such as stimulated Raman scattering (SRS) and self-phase-modulation (SPM) flexible Ytterbium doped extra-large mode area (XLMA) step index fibers, prepared by novel powder-sinter technology, have been used as gain fibers. As an example, for 12 ns pulses with a repetition rate of 10 kHz, a pump power limited average laser output power of more than 400 W in combination with peak powers of more than 3.5 MW (close to self-focusing-threshold) has been achieved in stable operation. The potentials of this laser system have been further explored towards longer pulse durations in order to achieve even higher pulse energies by means of pulse shaping techniques. In addition, investigations have been conducted with reduced pulse energies and repetition rates up to 500 kHz and average powers of more than 500 W at nearly diffraction limited beam quality.

Dinger, R.; Grundmann, F.-P.; Hapke, C.; Ruppik, S.



High-gain mode-adapted semiconductor optical amplifier with 12.4dBm saturation output power at 1550 nm  

Microsoft Academic Search

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias

K. Dreyer; C. H. Joyner; J. L. Pleumeekers; C. A. Burrus; A. Dentai; B. I. Miller; S. Shunk; P. Sciortino; S. Chandrasekhar; L. Buhl; F. Storz; M. Farwell



Adaptive allocation of attentional gain  

PubMed Central

Humans are adept at distinguishing between stimuli that are very similar, an ability that is particularly crucial when the outcome is of serious consequence (e.g. for a surgeon or air traffic controller). Traditionally, selective attention was thought to facilitate perception by increasing the gain of sensory neurons tuned to the defining features of a behaviorally relevant object (e.g. color, orientation, etc.). In contrast, recent mathematical models counter-intuitively suggest that in many cases attentional gain should be applied to neurons that are tuned away from relevant features, especially when discriminating highly similar stimuli. Here we used psychophysical methods to critically evaluate these ‘ideal observer’ models. The data demonstrate that attention enhances the gain of the most informative sensory neurons, even when these neurons are tuned away from the behaviorally relevant target feature. Moreover, the degree to which an individual adopted optimal attentional gain settings by the end of testing predicted success rates on a difficult visual discrimination task, as well as the amount of task improvement that occurred across repeated testing sessions (learning). Contrary to most traditional accounts, these observations suggest that the primary function of attentional gain is not simply to enhance the representation of target features, but to optimize performance on the current perceptual task. Additionally, individual differences in gain suggest that the operating characteristics of low-level attentional phenomena are not stable trait-like attributes and that variability in how attention is deployed may play an important role in determining perceptual abilities. PMID:19776279

Scolari, Miranda; Serences, John T.



Spontaneous emission of a two-level static atom coupling with the electromagnetic vacuum fluctuations outside a high-dimensional Einstein Gauss-Bonnet black hole  

E-print Network

In present paper, by using the generalized DDC formalism, we investigate the spontaneous excitation of an static atom interacting with electromagnetic vacuum fluctuations outside a EGB black hole in $d$-dimensions. We find that spontaneous excitation does not occur in Boulware vacuum. The Gauss-Bonnet term has no effect on the stability of the atom. Finally, we discuss the contribution of the coupling constant and dimensional factor to the results in three different kinds of spacetime.

Ming Zhang; Zhan-Ying Yang; Rui-Hong Yue



Gain weighted eigenspace assignment  

NASA Technical Reports Server (NTRS)

This report presents the development of the gain weighted eigenspace assignment methodology. This provides a designer with a systematic methodology for trading off eigenvector placement versus gain magnitudes, while still maintaining desired closed-loop eigenvalue locations. This is accomplished by forming a cost function composed of a scalar measure of error between desired and achievable eigenvectors and a scalar measure of gain magnitude, determining analytical expressions for the gradients, and solving for the optimal solution by numerical iteration. For this development the scalar measure of gain magnitude is chosen to be a weighted sum of the squares of all the individual elements of the feedback gain matrix. An example is presented to demonstrate the method. In this example, solutions yielding achievable eigenvectors close to the desired eigenvectors are obtained with significant reductions in gain magnitude compared to a solution obtained using a previously developed eigenspace (eigenstructure) assignment method.

Davidson, John B.; Andrisani, Dominick, II



The effect of a county's public high school summer remediation program on student gains on end-of-course standard of learning tests in Algebra I, Biology, Chemistry, Geometry and World History and Geography II  

NASA Astrophysics Data System (ADS)

The Commonwealth of Virginia requires high school students to receive a passing grade in core courses and a passing score on End-of-Course Standards of Learning (EOC SOL) tests to receive verified credits that lead to a Virginia high school diploma. These tests are believed to accurately reflect what students should know and be able to do in order to experience success in their endeavors beyond high school. For some students remediation is required to experience success on EOC SOL tests. This study sought to determine the effect of a County's public high school summer remediation program on student gains on EOC SOL tests in Algebra I, Biology, Chemistry, Geometry, and World History and Geography II. Specifically, the purpose of the study sought to determine the following: (a) If significant gains were made by students who attended the summer remediation program; (b) If significant gains were made by students who did not attend the summer remediation program; (c) If there were differences in gain scores of students who attended and those who did not attend the summer remediation program; and (d) If there were differences in gain scores among students who attended the summer remediation program related to school site, gender, ethnicity, learning ability group, socioeconomic status, and level of English proficiency. The results of the study indicate that students who attended and those who did not attend the summer remediation program made significant gains. However, the gains for students who attended the summer remediation program were significantly greater than the gains made by students who did not attend. The study also found that there were no significant differences in gain scores among students who attended the summer remediation program related to gender, ethnicity, learning ability group, socioeconomic status, and level of English proficiency. There were significant differences in Algebra I gain scores related to school site. Recommendations for practitioners and further research are presented. The study contributes to research on standards-based summer remediation programs and their effect on student gains on high-stakes tests.

Aiken, Brenda L.


Designing high performance Er +3-doped fiber amplifier in triangular-lattice photonic crystal fiber host towards higher gain, low splice loss  

NASA Astrophysics Data System (ADS)

In order to improve the over-all performance of all-fiber amplifier using Er +3-doped triangular-lattice photonic crystal fiber (PCF), we performed a detailed study on the amplifying characteristics of the PCF host by varying all associated geometrical parameters towards utilizing controllable effective numerical aperture and tight modal confinement. A finite difference (FD) mode convergence analysis is used to determine the modal propagation characteristics of the structure, which is then used to solve a standard propagation and population rate equation. Our results show that a spectral gain of the amplifier as high as 51 dB and that too over a short length ˜2.5 m of the fiber is achievable by optimizing the transverse geometry of the fiber. Aimed at field-deployment of the amplifier as inline component, we calculate the important all-fiber characteristics, namely, beam divergence, bending loss and nonlinearity and then optimize the splicing/coupling loss (resulting from the fundamental mode mismatch only) of this active fiber device. Notably, the splice loss with standard telecom-grade SMF-28 fiber is considerably minimized through an improved mode-matching of the design. These results record a marked improvement in fiber amplifier research in realizing high-performance EDFA-PCF amplifiers.

Mondal, Kajal; Chaudhuri, Partha Roy



High-Fat Diet with Acyl-Ghrelin Treatment Leads to Weight Gain with Low Inflammation, High Oxidative Capacity and Normal Triglycerides in Rat Muscle  

Microsoft Academic Search

Obesity is associated with muscle lipid accumulation. Experimental models suggest that inflammatory cytokines, low mitochondrial oxidative capacity and paradoxically high insulin signaling activation favor this alteration. The gastric orexigenic hormone acylated ghrelin (A-Ghr) has antiinflammatory effects in vitro and it lowers muscle triglycerides while modulating mitochondrial oxidative capacity in lean rodents. We tested the hypothesis that A-Ghr treatment in high-fat

Rocco Barazzoni; Michela Zanetti; Annamaria Semolic; Maria Rosa Cattin; Alessia Pirulli; Luigi Cattin; Gianfranco Guarnieri; Ian Lanza



Underrepresented Minority High School and College Students Report STEM-Pipeline Sustaining Gains After Participating in the Loma Linda University Summer Health Disparities Research Program  

PubMed Central

An urgent need exists for graduate and professional schools to establish evidence-based STEM (science, technology, engineering, and math) pipeline programs to increase the diversity of the biomedical workforce. An untapped yet promising pool of willing participants are capable high school students that have a strong STEM interest but may lack the skills and the guided mentoring needed to succeed in competitive STEM fields. This study evaluates and compares the impact of the Loma Linda University (LLU) Summer Health Disparities Research Program on high school (HS) and undergraduate (UG) student participants. The primary focus of our summer research experience (SRE) is to enhance the research self-efficacy of the participants by actively involving them in a research project and by providing the students with personalized mentoring and targeted career development activities, including education on health disparities. The results of our study show that our SRE influenced terminal degree intent and increased participant willingness to incorporate research into future careers for both the HS and the UG groups. The quantitative data shows that both the HS and the UG participants reported large, statistically significant gains in self-assessed research skills and research self-efficacy. Both participant groups identified the hands-on research and the mentor experience as the most valuable aspects of our SRE and reported increased science skills, increased confidence in science ability and increased motivation and affirmation to pursue a science career. The follow-up data indicates that 67% of the HS participants and 90% of the UG participants graduated from college with a STEM degree; for those who enrolled in graduate education, 61% and 43% enrolled in LLU, respectively. We conclude that structured SREs can be highly effective STEM strengthening interventions for both UG and HS students and may be a way to measurably increase institutional and biomedical workforce diversity. PMID:25250695

Salto, Lorena M.; Riggs, Matt L.; Delgado De Leon, Daisy; Casiano, Carlos A.; De Leon, Marino



Underrepresented Minority High School and College Students Report STEM-Pipeline Sustaining Gains After Participating in the Loma Linda University Summer Health Disparities Research Program.  


An urgent need exists for graduate and professional schools to establish evidence-based STEM (science, technology, engineering, and math) pipeline programs to increase the diversity of the biomedical workforce. An untapped yet promising pool of willing participants are capable high school students that have a strong STEM interest but may lack the skills and the guided mentoring needed to succeed in competitive STEM fields. This study evaluates and compares the impact of the Loma Linda University (LLU) Summer Health Disparities Research Program on high school (HS) and undergraduate (UG) student participants. The primary focus of our summer research experience (SRE) is to enhance the research self-efficacy of the participants by actively involving them in a research project and by providing the students with personalized mentoring and targeted career development activities, including education on health disparities. The results of our study show that our SRE influenced terminal degree intent and increased participant willingness to incorporate research into future careers for both the HS and the UG groups. The quantitative data shows that both the HS and the UG participants reported large, statistically significant gains in self-assessed research skills and research self-efficacy. Both participant groups identified the hands-on research and the mentor experience as the most valuable aspects of our SRE and reported increased science skills, increased confidence in science ability and increased motivation and affirmation to pursue a science career. The follow-up data indicates that 67% of the HS participants and 90% of the UG participants graduated from college with a STEM degree; for those who enrolled in graduate education, 61% and 43% enrolled in LLU, respectively. We conclude that structured SREs can be highly effective STEM strengthening interventions for both UG and HS students and may be a way to measurably increase institutional and biomedical workforce diversity. PMID:25250695

Salto, Lorena M; Riggs, Matt L; Delgado De Leon, Daisy; Casiano, Carlos A; De Leon, Marino



Wavelength swept amplified spontaneous emission source.  


We present a new, alternative approach to realize a wavelength swept light source with no fundamental limit to sweep speed. Amplified spontaneous emission (ASE) light alternately passes a cascade of optical gain elements and tunable optical bandpass filters. We show that for high sweep speeds, the control signal for the different filters has to be applied with a defined, precise phase delay on the order of nanoseconds, to compensate for the light propagation time between the filters and ensure optimum operation. At a center wavelength of 1300 nm sweep rates of 10 kHz, 100 kHz and 340 kHz over a sweep range of 100 nm full width and an average power of 50 mW are demonstrated. For application in optical coherence tomography (OCT), an axial resolution of 12 microm (air), a sensitivity of 120 dB (50 mW) and a dynamic range of 50 dB are achieved and OCT imaging is demonstrated. Performance parameters like coherence properties and relative intensity noise (RIN) are quantified, discussed and compared to the performance of Fourier Domain Mode Locked (FDML) lasers. Physical models for the observed difference in performance are provided. PMID:20372613

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



Invention and Gain Analysis.  

ERIC Educational Resources Information Center

Gain analysis is applied to the invention of the sewing needle as well as different sewing implements and modes of sewing. The analysis includes a two-subject experiment. To validate the generality of gain heuristics and underlying switching processes, the invention of the assembly line is also analyzed. (TJH)

Weber, Robert J.; Dixon, Stacey



Effects of Acidic Polysaccharides from Gastrodia Rhizome on Systolic Blood Pressure and Serum Lipid Concentrations in Spontaneously Hypertensive Rats Fed a High-Fat Diet  

PubMed Central

The effects of acidic polysaccharides purified from Gastrodia rhizome on blood pressure and serum lipid levels in spontaneously hypertensive rats (SHR) fed a high-fat diet were investigated. Acidic polysaccharides were purified from crude polysaccharides by DEAE-Sepharose CL-6B. Thirty-six male SHR were randomly divided into three groups: Gastrodia rhizome crude polysaccharide (A), acidic polysaccharide (B) groups, and a control group (C). A 5-week oral administration of all treatment groups was performed daily in 3- to 8-week-old SHRs with a dose of 6 mg/kg of body weight/day. After 5 weeks of treatment, total cholesterol in the acidic polysaccharide group, at 69.7 ± 10.6 mg/dL, was lower than in the crude polysaccharide group (75.0 ± 6.0 mg/dL) and the control group (89.2 ± 7.4 mg/dL). In addition, triglyceride and low-density lipoprotein cholesterol levels in the acidic polysaccharide group were lower than in the crude polysaccharide and control groups. The atherogenic index of the acidic polysaccharide group was 46.3% lower than in the control group. Initial blood pressure after the initial three weeks on the high-fat diet averaged 195.9 ± 3.3 mmHg among all rats. Compared with the initial blood pressure, the final blood pressure in the control group was increased by 22.8 mmHg, whereas it decreased in the acidic polysaccharide group by 14.9 mmHg. These results indicate that acidic polysaccharides from Gastrodia rhizome reduce hypertension and improve serum lipid levels. PMID:22312280

Lee, Ok-Hwan; Kim, Kyung-Im; Han, Chan-Kyu; Kim, Young-Chan; Hong, Hee-Do



Comparison of enalapril and valsartan in cyclosporine A-induced hypertension and nephrotoxicity in spontaneously hypertensive rats on high-sodium diet  

PubMed Central

We compared the effects of the angiotensin converting enzyme (ACE) inhibitor enalapril and the angiotensin AT1 receptor antagonist valsartan in cyclosporine A (CsA)-induced hypertension and nephrotoxicity in spontaneously hypertensive rats (SHR).SHR (8–9 weeks old) on high-sodium diet were given CsA (5?mg?kg?1d??1 s.c.) for 6 weeks. The rats were treated concomitantly either with enalapril (30?mg?kg?1d??1 p.o.) or valsartan (3 or 30?mg?kg?1 d??1 p.o.). To evaluate the role of bradykinin in the action of enalapril, some rats received a bradykinin B2 receptor antagonist icatibant (HOE 140, 500??g?kg?1 d??1 s.c.) during the last 2 weeks of enalapril treatment.Blood pressure was recorded every second week by tail cuff method. Renal function was measured by serum creatinine, creatinine clearance and urinary excretion of proteins at the end of the experiment. The activity of the renal kallikrein-kinin system was estimated by urinary kallikrein excretion.CsA caused hypertension, impaired renal function and induced morphological nephrotoxicity with glomerular damage and interstitial fibrosis.Enalapril and the lower dose of valsartan attenuated the CsA-induced hypertension to the same extent, while the higher dose of valsartan totally abolished it. Icatibant did not reduce the antihypertensive effect of enalapril. Urinary kallikrein excretion was similar in all groups. Enalapril and valsartan equally prevented the CsA-induced deterioration of kidney function and morphology.The renin-angiotensin but not the kallikrein-kinin system plays a crucial role in CsA-toxicity during high intake of sodium in SHR. PMID:10903974

Lassila, Markus; Finckenberg, Piet; Pere, Anna-Kaisa; Krogerus, Leena; Ahonen, Juhani; Vapaatalo, Heikki; Nurminen, Marja-Leena



High-resolution molecular validation of self-renewal and spontaneous differentiation in clinical-grade adipose-tissue derived human mesenchymal stem cells.  


Improving the effectiveness of adipose-tissue derived human mesenchymal stromal/stem cells (AMSCs) for skeletal therapies requires a detailed characterization of mechanisms supporting cell proliferation and multi-potency. We investigated the molecular phenotype of AMSCs that were either actively proliferating in platelet lysate or in a basal non-proliferative state. Flow cytometry combined with high-throughput RNA sequencing (RNASeq) and RT-qPCR analyses validate that AMSCs express classic mesenchymal cell surface markers (e.g., CD44, CD73/NT5E, CD90/THY1, and CD105/ENG). Expression of CD90 is selectively elevated at confluence. Self-renewing AMSCs express a standard cell cycle program that successively mediates DNA replication, chromatin packaging, cyto-architectural enlargement, and mitotic division. Confluent AMSCs preferentially express genes involved in extracellular matrix (ECM) formation and cellular communication. For example, cell cycle-related biomarkers (e.g., cyclins E2 and B2, transcription factor E2F1) and histone-related genes (e.g., H4, HINFP, NPAT) are elevated in proliferating AMSCs, while ECM genes are strongly upregulated (>10-fold) in quiescent AMSCs. AMSCs also express pluripotency genes (e.g., POU5F1, NANOG, KLF4) and early mesenchymal markers (e.g., NES, ACTA2) consistent with their multipotent phenotype. Strikingly, AMSCs modulate expression of WNT signaling components and switch production of WNT ligands (from WNT5A/WNT5B/WNT7B to WNT2/WNT2B), while upregulating WNT-related genes (WISP2, SFRP2, and SFRP4). Furthermore, post-proliferative AMSCs spontaneously express fibroblastic, osteogenic, chondrogenic, and adipogenic biomarkers when maintained in confluent cultures. Our findings validate the biological properties of self-renewing and multi-potent AMSCs by providing high-resolution quality control data that support their clinical versatility. PMID:24905804

Dudakovic, Amel; Camilleri, Emily; Riester, Scott M; Lewallen, Eric A; Kvasha, Sergiy; Chen, Xiaoyue; Radel, Darcie J; Anderson, Jarett M; Nair, Asha A; Evans, Jared M; Krych, Aaron J; Smith, Jay; Deyle, David R; Stein, Janet L; Stein, Gary S; Im, Hee-Jeong; Cool, Simon M; Westendorf, Jennifer J; Kakar, Sanjeev; Dietz, Allan B; van Wijnen, Andre J



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  

E-print Network

protein-based diet did not reduce, Thomas et al. Nutrition &diet and 12 wk timeframe were previously shown to elicit obesity, Thomas et al. Nutrition &Nutrition & Metabolism 2012, 9:3 RESEARCH Open Access A high calcium diet

Thomas, Anthony P; Dunn, Tamara N; Drayton, Josephine B; Oort, Pieter J; Adams, Sean H



Rice koji reduced body weight gain, fat accumulation, and blood glucose level in high-fat diet-induced obese mice.  


Rice koji is considered a readily accessible functional food that may have health-promoting effects. We investigated whether white, yellow, and red koji have the anti-obesity effect in C57BL/6J mice fed a high-fat diet (HFD), which is a model for obesity. Mice were fed HFD containing 10% (w/w) of rice koji powder or steamed rice for 4 weeks. Weight gain, epididymal white adipose tissue, and total adipose tissue weight were significantly lower in all rice koji groups than in the HFD-rice group after 4 weeks. Feed efficiency was significantly reduced in the yellow koji group. Blood glucose levels were significantly lower in the white and red koji groups with HOMA-R and leptin levels being reduced in the white koji group. White and red koji increased glucose uptake and GLUT4 protein expression in L6 myotube cells. These results showed that all rice koji have the anti-obesity or anti-diabetes effects although the mechanisms may differ depending on the type of rice koji consumed. PMID:25237599

Yoshizaki, Yumiko; Kawasaki, Chihiro; Cheng, Kai-Chun; Ushikai, Miharu; Amitani, Haruka; Asakawa, Akihiro; Okutsu, Kayu; Sameshima, Yoshihiro; Takamine, Kazunori; Inui, Akio



Spontaneous Facial Motility in Infancy: A 3D Kinematic Analysis  

PubMed Central

Early spontaneous orofacial movements have rarely been studied experimentally, though the motor experiences gained from these behaviors may influence the development of motor skills emerging for speech. This investigation quantitatively describes developmental changes in silent, spontaneous lip and jaw movements from 1 to 12 months of age using optically based 3D motion capture technology. Twenty-nine typically developing infants at five ages (1, 5, 7, 9, and 12 months) were studied cross-sectionally. Infants exhibited spontaneous facial movements at all ages studied. Several age-related changes were detected in lip and jaw kinematics: the occurrence of spontaneous movements increased, movement speed increased, the duration of movement epochs decreased and movement coupling among different facial regions increased. Additionally, evidence for stereotypic movements was not strong. The present findings suggest that, during the first year of life, early spontaneous facial movements undergo significant developmental change in the direction of skill development for speech. PMID:16381029

Green, Jordan R.; Wilson, Erin M.



Effective spontaneous PT-symmetry breaking in hybridized metamaterials  

NASA Astrophysics Data System (ADS)

We show that metamaterials can be used as a testing ground to investigate spontaneous symmetry breaking associated with non-Hermitian quantum systems. By exploring the interplay between near-field dipolar coupling and material absorption or gain, we demonstrate various spontaneous breaking processes of the PT symmetry for a series of effective Hamiltonians associated with the scattering matrix. By tuning the coupling parameter, coherent perfect absorption, laser action, and gain-induced complete reflection (? reflector) by using an ultrathin metamaterial can be obtained. Moreover, an ideal PT symmetry can be established effectively in a passive system by exploring the balance between scattering and absorption loss using metamaterials.

Kang, Ming; Liu, Fu; Li, Jensen



[Spontaneous pontine hemorrhage].  


Data from 11 observed patients with spontaneous pontine haemorrhages were compared to the findings in 235 cases reported in 9 studies. Causes of pontine haemorrhages which have an incidence of 2 to 4/100 000/year include hypertension, vascular malformations (a.v.-haemangioma, cavernous haemangioma, capillary teleangiectasies), anticoagulative treatment and inflammatory vascular disease. Diffusely spreading hypertensive haemorrhages are of apo-plectiform onset with fast developing coma, and show disturbance of vegetative function (disturbance of respiration, cardiac dysrhythmias, hyperthermia, hypertension), miosis and other neuroophthalmologic symptoms, flaccid tetraparalysis and blood-stained cerebrospinal fluid; mortality is high, reaching 50% after 24 hours and 90% after 3 weeks. Vascular malformations are the origin of circumscribed pontine haematomas with slowly progressing disturbance of consciousness and brain stem symptoms with variable course exhibiting multiple remissions and recurrences. In respect of symptomatology and clinical course, slight lateral hypertensive pontine haemorrhages must be placed between these two typical syndromes. Diagnosis of pontine haemorrhages is supported by x-ray computed tomography, but vascular malformations can be detected only by cerebral angiography. Treatment of patients with pontine haemorrhages must be based on intensive care with regular control via CT. Increased intracranial pressure and internal hydrocephalus caused by blockage of CSF passage necessitate ventricular drainage. While hypertensive pontine haemorrhages cannot be surgically treated, pontine haematomas and the causative vascular malformations can be removed. PMID:6479827

Bewermeyer, H; Neveling, M; Ebhardt, G; Heiss, W D



High-Throughput Analysis of NF-?B Dynamics in Single Cells Reveals Basal Nuclear Localization of NF-?B and Spontaneous Activation of Oscillations  

PubMed Central

NF-?B is a transcription factor that upon activation undergoes cycles of cytoplasmic-to-nuclear and nuclear-to-cytoplasmic transport, giving rise to so called “oscillations”. In turn, oscillations tune the transcriptional output. Since a detailed understanding of oscillations requires a systems biology approach, we developed a method to acquire and analyze large volumes of data on NF-?B dynamics in single cells. We measured the time evolution of the nuclear to total ratio of GFP-p65 in knock-in mouse embryonic fibroblasts using time-lapse imaging. We automatically produced a precise segmentation of nucleus and cytoplasm based on an accurate estimation of the signal and image background. Finally, we defined a set of quantifiers that describe the oscillatory dynamics, which are internally normalized and can be used to compare data recorded by different labs. Using our method, we analyzed NF-?B dynamics in over 2000 cells exposed to different concentrations of TNF- ? ?. We reproduced known features of the NF-?B system, such as the heterogeneity of the response in the cell population upon stimulation and we confirmed that a fraction of the responding cells does not oscillate. We also unveiled important features: the second and third oscillatory peaks were often comparable to the first one, a basal amount of nuclear NF-?B could be detected in unstimulated cells, and at any time a small fraction of unstimulated cells showed spontaneous random activation of the NF-?B system. Our work lays the ground for systematic, high-throughput, and unbiased analysis of the dynamics of transcription factors that can shuttle between the nucleus and other cell compartments. PMID:24595030

Zambrano, Samuel; Bianchi, Marco E.; Agresti, Alessandra



Pulsed laser operating on the first vibrational overtone of the CO molecule in the 2.5 - 4.2-{mu}m range: 3. The gain and kinetic processes on high vibrational levels  

SciTech Connect

The gain dynamics in the active medium of an overtone CO laser operating on the transitions between high vibrational levels is studied experimentally and theoretically. The gain dynamics is measured on the vibration - rotation transitions of the CO molecule [the P(12) spectral line in the vibrational bands from 20 {yields} 18 to 36 {yields} 34] in CO - He and CO - N{sub 2} laser mixtures. The maximum small-signal gain was 0.43 m{sup -1}. The theoretical model of the CO laser was significantly improved. It was shown that multiquantum and asymmetric VV-exchange processes should be included in the analysis of the population dynamics of high vibrational levels of the CO molecule. (lasers)

Basov, N G; Ionin, Andrei A; Klimachev, Yu M; Kotkov, A A; Seleznev, L V; Sinitsyn, D V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Kurnosov, A K; Napartovich, A P; Shnyrev, S L [State Research Center of Russian Federation 'Troitsk Institute for Innovation and Fusion Research', Troitsk, Moscow Region (Russian Federation); McCord, J E; Hager, G D [US Air Force Research Laboratories, Kirtland, New Mexico (United States)



Optical gain characteristics of staggered InGaN quantum wells lasers  

NASA Astrophysics Data System (ADS)

Staggered InGaN quantum wells (QWs) are analyzed as improved gain media for laser diodes (LDs) lasing at 440 and 500 nm. The calculation of band structure is based on a 6-band k ?p method taking into account the valence band mixing, strain effect, and spontaneous and piezoelectric polarizations as well as the carrier screening effect. Staggered InGaN QWs with two-layer and three-layer step-function like In-content InGaN QWs structures are investigated to enhance the optical gain as well as to reduce the threshold current density for LDs emitting at 440 and 500 nm. Our analysis shows that the optical gain is enhanced by 1.5-2.1 times by utilizing the staggered InGaN QW active region emitting at 440 nm, which leads to a reduction of the threshold current density up to 24% as compared to that of the conventional InGaN QW laser. Staggered InGaN QWs with enhanced optical gain shows significantly reduced blue-shift as carrier density increases, which enables nitride QWs with high optical gain in the green spectral regime. The use of green-emitting three-layer staggered InGaN QW is also expected to lead to reduction in the threshold carrier density by 30%.

Zhao, Hongping; Tansu, Nelson



Making the most of fMRI at 7 T by suppressing spontaneous signal fluctuations.  


The presence of spontaneous BOLD fMRI signal fluctuations in human grey matter compromises the detection and interpretation of evoked responses and limits the sensitivity gains that are potentially available through coil arrays and high field systems. In order to overcome these limitations, we adapted and improved a recently described correlated noise suppression method (de Zwart et al., 2008), demonstrating improved precision in estimating the response to ultra-short visual stimuli at 7 T. In this procedure, the temporal dynamics of spontaneous signal fluctuations are estimated from a reference brain region outside the area targeted with the stimulus. Rather than using the average signal in this region as regressor, as proposed in the original method, we used principal component analysis to derive multiple regressors in order to optimally describe nuisance signals (e.g. spontaneous fluctuations) and separate these from evoked activity in the target region. Experimental results obtained from application of the original method showed a 66% improvement in estimation precision. The novel, enhanced version of the method, using 18 PCA-derived noise regressors, led to a 160% increase in precision. These increases were relative to a control condition without noise suppression, which was simulated by randomizing the time-course of the nuisance-signal regressor(s) without altering their power spectrum. The increase of estimation precision was associated with decreased autocorrelation levels of the residual errors. These results suggest that modeling of spontaneous fMRI signal fluctuations as multiple independent sources can dramatically improve detection of evoked activity, and fully exploit the potential sensitivity gains available with high field technology. PMID:18835582

Bianciardi, Marta; van Gelderen, Peter; Duyn, Jeff H; Fukunaga, Masaki; de Zwart, Jacco A



A low-power high-performance configurable auto-gain control loop for a digital hearing aid SoC  

NASA Astrophysics Data System (ADS)

A low-power, configurable auto-gain control loop for a digital hearing aid system on a chip (SoC) is presented. By adopting a mixed-signal feedback control structure and peak detection and judgment, it can work in automatic gain or variable gain control modes through a digital signal processing unit. A noise-reduction and dynamic range (DR) improvement technique is also used to ensure the DR of the circuit in a low-voltage supply. The circuit is implemented in an SMIC 0.13 ?m 1P8M CMOS process. The measurement results show that in a 1 V power supply, 1.6 kHz input frequency and 200 mVp—p, the SFDR is 74.3 dB, the THD is 66.1 dB, and the total power is 89 ?W, meeting the application requirements of hearing aid SoCs.

Chengying, Chen; Hainan, Liu; Yong, Hei; Jun, Fan; Xiaoyu, Hu



[High risk of recurrent spontaneous abortion during second trimester in women carriers of polymorphism A2 in platelet glycoprotein IIb/IIIa].  


The aim of this study was to evaluate the role of polymorphism A2 (PLA2) in platelet glycoprotein IIb/IIIa (GP IIb/IIIa) in the development of recurrent spontaneous abortion (RSA)--miscarriages before 20th week of gestation (wg) of pregnancy. The carriage status of PLA2 in GP IIb/IIIa, single and in combination with FVL and FII G20210A was investigated in 56 women with recurrent miscarriages before 10 g, in 38 women with RSA from 10 to 20 wg and in 98 healthy women with at least one uncomplicated full-term pregnancy. The significant prevalence of carriage of PLA2 in GP IIb/IIIa in women with RSA in first 20 wg was found with high risk or miscarriage (OR = 4.32; 95% CI: 2.10-8.97, p < 0.0001). However, after adjustment for combined carriage of other thrombophilic factors (PLA2 and FVL or PLA2 with FII G20210A) the risk was still high (OR = 2.07; 95% CI: 0.98-4.40 p = 0.058), but not significant. The similar results (OR = 2.632; 95% CI: 1.140-6.104, p = 0.021) were found for women with recurrent miscarriages in the first 10 wg. The prevalence of PLA2 adjusted for combined carriage of other thrombophilic factors was also not significant. The carriage status of PLA2 in GP IIb/IIIa in women with RSA in the period from 10 to 20 wg was significantly higher as compared to controls (OR = 8.79; 95% CI: 3.477-22.605, p < 0.0001). The prevalence, adjusted for combined carriage of other thrombophilic factors (PLA2 with FVL or PLA2 with FII G20210A) was also significantly higher (OR: 2.990; 95% CI: 1.178-7.613, p = 0.018). These results confirm the impact of PLA2 polymorphism on RSA in the period of 10 to 20 wg, and its contribution to RSA in the first 10 wg in combination with other thrombophilic mutations. The results support the suggestion of testing women with miscarriages in first 20 wg for PLA2 carriage and application of appropriate prophylactic antiplatelet drug therapy for next planned pregnancy. PMID:19230252

Ivanov, P; Komsa-Penkova, R; Ivanov, I; Konova, E; Kovacheva, K; Sto?kov, S; Popov, I



Brazilian Multicentre Study on Preterm Birth (EMIP): Prevalence and Factors Associated with Spontaneous Preterm Birth  

PubMed Central

Background Preterm birth rate is increasing and is currently a worldwide concern. The purpose of this study was to estimate the prevalence of preterm birth in a sample of health facilities in Brazil and to identify the main risk factors associated with spontaneous preterm births. Methods and Findings This was a multicentre cross sectional study on preterm births in 20 referral obstetric hospitals with a case-control component to identify factors associated with spontaneous preterm birth. Surveillance was implemented at all centres to identify preterm births. For eligible consenting women, data were collected through a post-delivery questionnaire completed with information from all mother-newborn medical records until death or discharge or at a maximum of 60 days post-delivery, whichever came first. The risk of spontaneous preterm birth was estimated with OR and 95%CI for several predictors. A non-conditional logistic regression analysis was then performed to identify independently associated factors. The overall prevalence of preterm birth was 12.3%. Among them, 64.6% were spontaneous and 35.4% therapeutic. In the case-control component, 2,682 spontaneous preterm births were compared to a sample of 1,146 term births. Multivariate analyses identified the following as risk factors for spontaneous preterm birth among women with at least one previous birth: a previous preterm birth (ORadj?=?3.19, 2.30–4.43), multiple pregnancy (ORadj?=?29.06, 8.43–100.2), cervical insufficiency (ORadj?=?2.93, 1.07–8.05), foetal malformation (ORadj?=?2.63, 1.43–4.85), polyhydramnios (ORadj?=?2.30, 1.17–4.54), vaginal bleeding (ORadj?=?2.16, 1.50–3.11), and previous abortion (ORadj?=?1.39, 1.08–1.78). High BMI (ORadj?=?0.94, 0.91–0.97) and weight gain during gestation (ORadj?=?0.92, 0.89–0.95) were found to be protective factors. Conclusions The preterm birth rate in these health facilities in Brazil is high and spontaneous preterm births account for two thirds of them. A better understanding of the factors associated with spontaneous preterm birth is of utmost importance for planning effective measures to reduce the burden of its increasing rates. PMID:25299699

Passini, Renato; Cecatti, Jose G.; Lajos, Giuliane J.; Tedesco, Ricardo P.; Nomura, Marcelo L.; Dias, Tabata Z.; Haddad, Samira M.; Rehder, Patricia M.; Pacagnella, Rodolfo C.; Costa, Maria L.; Sousa, Maria H.



High-gain excitonic lasing from a single InAs monolayer in bulk GaAs A. R. Gon~i, M. Stroh, C. Thomsen, F. Heinrichsdorff, V. Turck, A. Krost,  

E-print Network

of the emission as determined from cathodoluminescence and the absence of band-gap renormalization with increasing of the pump power, at about 100 meV below the GaAs band gap involving radiative recombination processes fromHigh-gain excitonic lasing from a single InAs monolayer in bulk GaAs A. R. Gon~i, M. Stroh, C

Nabben, Reinhard


Simplified ASE correction algorithm for variable gain-flattened erbium-doped fiber amplifier.  


We demonstrate a simplified algorithm to manifest the contribution of amplified spontaneous emission in variable gain-flattened Erbium-doped fiber amplifier (EDFA). The detected signal power at the input and output ports of EDFA comprises of both signal and noise. The generated amplified spontaneous emission from EDFA cannot be differentiated by photodetector which leads to underestimation of the targeted gain value. This gain penalty must be taken into consideration in order to obtain the accurate gain level. By taking the average gain penalty within the dynamic gain range, the targeted output power is set higher than the desired level. Thus, the errors are significantly reduced to less than 0.15 dB from 15 dB to 30 dB desired gain values. PMID:19506658

Mahdi, Mohd Adzir; Sheih, Shou-Jong; Adikan, Faisal Rafiq Mahamd



Theoretical investigation of the more suitable rare earth to achieve high gain in waveguide based on silica containing silicon nanograins doped with either Nd³+ or Er³+ ions.  


We present a comparative study of the gain achievement in a waveguide whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd3+) or erbium ions (Er3+). By means of an auxiliary differential equation and finite difference time domain (ADE-FDTD) approach that we developed, we investigate the steady states regime of both rare earths ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 104 mW/mm2. Moreover, the achievable gain has been estimated in this pumping range. The Nd3+ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB/cm) than the one with Er3+ doped active layer at 1532 nm (up to 2 dB/cm). Taking into account the experimental background losses we demonstrate that a significant positive net gain can only be achieved with the Nd3+ doped waveguide. PMID:24921348

Fafin, Alexandre; Cardin, Julien; Dufour, Christian; Gourbilleau, Fabrice



An alloy semiconductor system with a tailorable band-tail and its application to high-performance laser operation: II. Experimental study on InGaN MQW laser for optimization of differential gain characteristics tuned by In compositional fluctuation  

NASA Astrophysics Data System (ADS)

Differential gain and carrier lifetime have been deduced experimentally for InGaN MQWs having different magnitudes of In compositional fluctuation and defect density in the active layer. It has been found that the compositional fluctuation and differential gain show a strong correlation in full accordance with the theoretical model for a band-tail modified by In compositional fluctuation as described in the companion paper (part I). Several laser characteristics, threshold current density, differential gain and response time, were found to be affected by the compositional fluctuation and defect density. The optimization of these growth parameters for producing high-performance blue-violet InGaN MQW LDs is also discussed.

Kuramoto, M.; Hisanaga, Y.; Kimura, A.; Futagawa, N.; Yamaguchi, A. A.; Nido, M.; Mizuta, M.



Amplified spontaneous emission in solar-pumped iodine laser  

NASA Technical Reports Server (NTRS)

The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.



Spontaneous Emission of a Two-Level Static Atom Coupling with Electromagnetic Vacuum Fluctuations Outside a High-Dimensional Einstein Gauss–Bonnet Black Hole  

NASA Astrophysics Data System (ADS)

Using the generalized formalism of Dalibard, Dupont–Roc and Cohen–Tannoudji we investigate the spontaneous excitation of a static atom interacting with electromagnetic vacuum fluctuations outside an Einstein Gauss–Bonnet black hole in d-dimensions. It shows that spontaneous excitation does not occur in a Boulware vacuum, while exists in an Unruh vacuum and Hartle–Hawking vacuum. As to the total rate of change of the atomic energy, it does not receive the contribution from the coupling constant of the Gauss–Bonnet term at spatial infinity only the dimensional parameter has the contribution to it. Near the event horizon, both the coupling constant and the dimension p contribute to the total rate of change of the atomic energy in all three kinds of vacuum. We discuss the contribution of the coupling constant and dimensional factor to the results in three different kinds of spacetime lastly.

Zhang, Ming; Yang, Zhan-Ying; Yue, Rui-Hong



Spontaneous Kidney Allograft Rupture  

Microsoft Academic Search

Spontaneous renal allograft rupture is one of the most dangerous complications of kidney transplantation, which can result in graft loss.This condition needs immediate surgical intervention. Conservative management has dismal results. Its prevalence varies from 0.3% to 3%. Rupture occurs in first few weeks after transplantation. Predisposing factors for graft rupture are acute rejection, acute tubular necrosis, and renal vein thrombosis.

H. Shahrokh; H. Rasouli; M. A. Zargar; K. Karimi; K. Zargar



Spontaneous transverse colon volvulus  

PubMed Central

We report a case of spontaneous transverse colon volvulus in a young healthy woman. It constitutes an unusual case since it occurred in a young healthy woman with a subacute onset and no aetiological factor has been found. Its diagnosis is still challenging. Prompt recognition with emergency intervention constitutes the key to successful outcome. PMID:23785565

Sana, Landolsi; Ali, Gassara; Kallel, Helmi; Amine, Baklouti; Ahmed, Saadaoui; Mohamed Ali, Elouer; Wajdi, Chaeib; Saber, Mannai



[Spontaneous recanalization after vasectomy].  


Two cases of spontaneous recanalisation could be reoperated. The recanalisation was proved histologically. The reasons were analysed. The own technique is presented: resection of at least two centimeters of the vas, ligature, electrocoagulation, proximally turning-up fixation of the end, distally immersing the end in a tobacco-pouch. PMID:8119817

Pestalozzi, D M; Bannwart, F; Knönagel, H



Advanced-stage cervical carcinomas are defined by a recurrent pattern of chromosomal aberrations revealing high genetic instability and a consistent gain of chromosome arm 3q  

Microsoft Academic Search

We have analyzed 30 cases of advanced-stage cervical squamous cell carcinoma (stages IIb-IV) by comparative genomic hybridization (CGH). The most consistent chromosomal gain in the aneuploid tumors was mapped to chromosome arm 3q in 77% of the cases. Acquisition of genetic material also occurred frequently on 1q (47%), 5p (30%), 6p (27%), and 20 (23%). Recurrent losses were mapped on

K. Heselmeyer-Haddad; Merryn Macville; Evelin Schröck; Harald Blegen; Keerti Shah; Gert Auer; Thomas Ried



Design of a high-gain laser diode-array pumped Nd:YAG Alternating Precessive Slab Amplifier (APS-Amplifier)  

NASA Astrophysics Data System (ADS)

In the design of space qualifiable laser systems for ranging and altimetry, such as NASA's Geodynamic Laser Ranging System (GLRS), the transmitter must be kept small, powerful yet efficient, and must consist of as few components as possible. A novel preamplifier design is examined which requires no external beam steering optics, yielding a compact component with simple alignment procedures. The gains achieved are comparable to multipass zigzag amplifiers using two or more sets of external optics for extra passes through the amplifying medium.

Coyle, D. Barry


Low body weight gain, low white blood cell count and high serum ferritin as markers of poor nutrition and increased risk for preterm delivery.  


This study determined factors of preterm delivery in Taiwan. Healthy women (n=520, age 29.1±4.2 y) at 8-12 weeks of pregnancy were recruited from prenatal clinics. Background information, anthropometrics, biochemical parameters, and dietary intake, collected by 24 h-recall were obtained from the first, second, and third trimesters to delivery. Clinical outcomes of neonates were also collected. The results show that 53.7% of women were primiparous and that the incidence of preterm delivery was 6.2%. Body weight gains in the first trimester and throughout pregnancy were significantly lower in mothers with preterm delivery (preterm group) than in mothers with term delivery (term group, p<0.05). Maternal cholesterol intake, circulating white blood cell counts (WBC) and serum albumin were significantly lower and that serum magnesium and ferritin were significantly higher in the preterm group than in the term group. Maternal weight gain was positively correlated with caloric and nutrient intake (p<0.05). Neonatal birth weight was positively correlated with maternal weight gain and intakes of protein and phosphate during pregnancy; with intakes of calories, vitamin B-1 and B-2 in the first trimester; and with intakes of calcium, magnesium, iron and zinc, as well as circulating WBC in the third trimester. However, neonatal birth weight was negatively correlated with serum iron in the third trimester and with serum iron and ferritin at the time of delivery. In conclusion, maternal weight gain in early pregnancy and WBC, mineral intake and iron status in late pregnancy seem to be major factors affecting delivery and neonatal outcomes. PMID:23353616

Hsu, Wen-Yin; Wu, Cheng-Hsuan; Hsieh, Charles Tsung-Che; Lo, Hui-Chen; Lin, Jen-Shiou; Kao, Mei-Ding



High Reliability 49 dB Gain, 13W PM Fiber Amplifier at 1550 nm with 30 dB PER and Record Efficiency  

Microsoft Academic Search

We present a single-mode, polarization-maintaining, Er\\/Yb-codoped cladding-pumped amplifier with up to 49 dB of gain, 13W output power, a 30 dB polarization-extinction ratio, 12.9% electrical to optical conversion efficiency, and 42% optical-optical power-stage fiber slope efficiency. This is the most efficient highest PER HPOA ever reported near 1550 nm. The HPOA was built using all fiber-based components qualifiable for long

P. Wysocki; T. Wood; A. Grant; D. Holcomb; K. Chang; M. Santo; L. Braun; G. Johnson



Spontaneous neonatal gastric perforation  

Microsoft Academic Search

Over a 7-year period (1990-1997) spontaneous gastric perforation was diagnosed in five neonates. The mean gestational age and birth weight were 33\\/40 weeks and 1.83 kg, respectively. All patients presented with severe abdominal distention and frank pneumoperitoneum on roentgenograms. All perforations were on the anterior wall of the greater curvature and were managed by prompt laparotomy and primary closure of

Akram J. Jawad; A. Al-Rabie; Anjum Hadi; A. Al-Sowailem; A. Al-Rawaf; Bashar Abu-Touk; T. Al-Karfi; A. Al-Sammarai



Spontaneous Physics/Astronomy,  

E-print Network

to the spontaneous expulsion of interior objects from a vesicle without otherwise damaging either the ``parent'' or the ``daughter'' object [6] (Fig. 1). In the light of our earlier remarks it is remarkable that this dramatic of radius R = 4:5 ¯m in pure water (see text) ini­ tially contains a smaller daughter of radius r = 3:3 ¯m

Nelson, Philip


High peak power and sub-picosecond Fourier-limited pulse generation from passively mode-locked monolithic two-section gain-guided tapered InGaAs quantum-dot lasers  

NASA Astrophysics Data System (ADS)

We report on the development of a new generation of high-power ultrashort pulse quantum-dot lasers with tapered gain section. Two device designs are proposed and fabricated, with different total lengths and absorber-to-gain-section length-ratios. These designs have been informed by numerical simulations of the dynamic mode-locking regimes and their dependence on the structural parameters. One device design demonstrated a record-high peak power of 17.7 W with 1.26 ps pulse width and a second design enabled the generation of a Fourier-limited 672 fs pulse width with a peak power of 3.8 W. A maximum output average power of 288 mW with 28.7 pJ pulse energy was also attained. In addition, the integrated timing jitter of 2.6 ps and far-field patterns are demonstrated.

Nikitichev, D. I.; Ding, Y.; Cataluna, M. A.; Rafailov, E. U.; Drzewietzki, L.; Breuer, S.; Elsaesser, W.; Rossetti, M.; Bardella, P.; Xu, T.; Montrosset, I.; Krestnikov, I.; Livshits, D.; Ruiz, M.; Tran, M.; Robert, Y.; Krakowski, M.



Gain control mechanisms in spinal motoneurons  

PubMed Central

Motoneurons provide the only conduit for motor commands to reach muscles. For many years, motoneurons were in fact considered to be little more than passive “wires”. Systematic studies in the past 25 years however have clearly demonstrated that the intrinsic electrical properties of motoneurons are under strong neuromodulatory control via multiple sources. The discovery of potent neuromodulation from the brainstem and its ability to change the gain of motoneurons shows that the “passive” view of the motor output stage is no longer tenable. A mechanism for gain control at the motor output stage makes good functional sense considering our capability of generating an enormous range of forces, from very delicate (e.g., putting in a contact lens) to highly forceful (emergency reactions). Just as sensory systems need gain control to deal with a wide dynamic range of inputs, so to might motor output need gain control to deal with the wide dynamic range of the normal movement repertoire. Two problems emerge from the potential use of the brainstem monoaminergic projection to motoneurons for gain control. First, the projection is highly diffuse anatomically, so that independent control of the gains of different motor pools is not feasible. In fact, the system is so diffuse that gain for all the motor pools in a limb likely increases in concert. Second, if there is a system that increases gain, probably a system to reduce gain is also needed. In this review, we summarize recent studies that show local inhibitory circuits within the spinal cord, especially reciprocal and recurrent inhibition, have the potential to solve both of these problems as well as constitute another source of gain modulation. PMID:25120435

Johnson, Michael D.; Heckman, Charles J.



Highly efficient and robust operation of Kerr-lens mode-locked Cr:LiSAF lasers using gain-matched output couplers.  


We present efficient and robust Kerr-lens mode locking (KLM) of a diode-pumped Cr:LiSAF laser using a gain-matched output coupler (GMOC). An inexpensive, battery-powered 660 nm single-spatial-mode diode was used as the pump source. GMOC enhances the effective self-amplitude modulation depth by reducing the gain-filtering effect in broadband KLM operation to provide significant improvement in efficiency and robustness. Pulsing can be initiated without careful cavity alignment and is sustained for hours. 13 fs pulses with an average power of 25 mW have been generated using only 120 mW of pump power. The corresponding pulse energy and peak power is 200 pJ and 15 kW for the 126 MHz repetition rate cavity. Optical-to-optical conversion efficiency of the system is 21%, which represents an order of magnitude improvement in reported efficiencies for such diode-pumped ultrashort-pulse KLM Cr:LiSAF lasers. The obtainable pulse width is currently limited by the dispersion bandwidth of the available optics and can be potentially reduced to below 7 fs. PMID:24562138

Canbaz, Ferda; Beyatli, Ersen; Chen, Li-Jin; Sennaroglu, Alphan; Kärtner, Franz X; Demirbas, Umit



Spontaneous patella fracture presenting as osteomyelitis in focal dermal hypoplasia  

Microsoft Academic Search

We report the first case of the assessment and treatment of a spontaneous patellar fracture in a patient with Goltz syndrome—a rare dermal hypoplasia. This case illustrates the non-straightforward presentation of a spontaneous patellar fracture in seemingly osteoporotic bone stock further complicated by the inability to rule out osteomyelitis. In this confusing presentation, a high index of suspicion for patella

Eric L. Altschuler; Richard S. Yoon; Richard Dentico; Frank A. Liporace


Spontaneous Bilateral Meningoencephalocoeles of the Temporal Bones  

PubMed Central

Spontaneous tegmen tympani defects are rare with even rarer bilateral cases. The symptoms are nonspecific; hence, a high index of suspicion is required to prevent serious intracranial complications. We present a case of spontaneous bilateral tegmen tympani defects with associated meningoencephalocoeles in a 54-year-old male who presented with the signs and symptoms of severe meningitis. After careful workup which included a lumbar puncture, CT and MRI scans, both defects were repaired using a middle fossa approach. The patient made an uneventful recovery with complete cessation of otorrhoea and improvement in his hearing. PMID:24288640



Assess the key physics that underpins high-hydro coupling-efficiency in NDCX-II experiments and high-gain heavy ion direct drive target designs using proven hydro codes like HYDRA  

SciTech Connect

The simulations provided in this milestone have solidified the theoretical underpinning of direct drive targets and also the ability to design experiments on NDCX II that will enhance our understanding of ion-beam hydrodynamic coupling, and thus be relevant to IFE. For the case of the IFE targets, we have studied hydro and implosion efficiency using HYDRA in ID, a starting point towards the goal of polar direct drive in geometry compatible with liquid wall chambers. Recent analysis of direct drive fusion energy targets using heavy ion beams has found high coupling efficiency of ion beam energy into implosion energy. However, to obtain optimal coupling, the ion energy must increase during the pulse in order to penetrate the outflowing ablated material, and deposit the energy close enough to the fuel so that the fuel achieves sufficient implosion velocity. We have computationally explored ID (radial) time dependent models of ion driven direct drive capsule implosions using the Arbitrary Lagrangian-Eulerian (ALE) code HYDRA, to help validate the theoretical analysis done so far, particularly exploring the effects of varying the ion energy and ion current over the course of the pulse. On NDCX II, experiments have been proposed to explore issues of ion penetration of the outflowing plasma over the course of the ion pulse. One possibility is to create a first pulse of ions that heats a planar target, and produces an outflow of material. A second pulse, {approx}10 ns after the first, of higher ion energy (and hence larger projected range) will interact with this outflow before reaching and further heating the target. We have investigated whether the change in range can be tailored to match the evolution of the ablation front. We have carried out simulations using the one-dimensional hydrodynamic code DISH and HYDRA to set parameters for this class of experiments. DISH was upgraded with an ion deposition algorithm, and we have carried out ID (planar) simulations. HYDRA was also used for ID (planar) and 2D (r,z) simulations of potential experiments. We have also explored whether similar physics could be studied using an energy ramp (i.e., a velocity tilt) rather than two separate pulses. We have shown that an optimum occurs in the macropulse duration (with fixed velocity tilt) that maximizes the shock strength. In the area of IFE target design we have continued to explore direct drive targets composed of deuterium-tritium fuel and ablator layers. We have extended our previous target designs at 0.44 MJ drive energy, gain 50, (50 MeV foot, 500 MeV main pulse, Rb ion, which requires a large number of beams due to a high beam space charge constraint) to a power plant scale 3.7 MJ drive energy, gain {approx}150 (220 MeV foot, 2.2 GeV main pulse, Hg ion) that eases requirements on the accelerator. We have studied the effects of two important design choices on ICF target performance. We have shown that increasing the number of foot pulses may reduce the target's in-flight adiabat and consequently improve its compressibility and fusion yield. As in the case of laser drive, the first three shocks are the most important to the target's performance, with additional shocks contributing only marginally to compression and burn. We have also demonstrated that ion range lengthening during the main pulse can further reduce the target adiabat and improve the efficiency with which beam energy is coupled into the target. (Ion range lengthening using two different kinetic energies for the foot and main pulse has previously proven effective in the design of high gain targets).

Barnard, J. J.; Hay, M. J.; Logan, B. G.; Ng, S. F.; Perkins, L. J.; Veitzer, S.; Yu, S. S.



Spontaneous recovery in dynamical networks  

NASA Astrophysics Data System (ADS)

Much research has been carried out to explore the structural properties and vulnerability of complex networks. Of particular interest are abrupt dynamic events that cause networks to irreversibly fail. However, in many real-world phenomena, such as brain seizures in neuroscience or sudden market crashes in finance, after an inactive period of time a significant part of the damaged network is capable of spontaneously becoming active again. The process often occurs repeatedly. To model this marked network recovery, we examine the effect of local node recoveries and stochastic contiguous spreading, and find that they can lead to the spontaneous emergence of macroscopic `phase-flipping' phenomena. As the network is of finite size and is stochastic, the fraction of active nodes z switches back and forth between the two network collective modes characterized by high network activity and low network activity. Furthermore, the system exhibits a strong hysteresis behaviour analogous to phase transitions near a critical point. We present real-world network data exhibiting phase switching behaviour in accord with the predictions of the model.

Majdandzic, Antonio; Podobnik, Boris; Buldyrev, Sergey V.; Kenett, Dror Y.; Havlin, Shlomo; Eugene Stanley, H.



Factors influencing spontaneous combustion of solid waste.  


Landfill fires create a critical problem for landfill operators and require investigation of its occurrence and the conditions that favor its initiation. Subsurface fires are considered the most significant due to the difficulty in determining their location and extent. These fires are mainly caused by spontaneous combustion, combustion due to high temperature in absence of flame. This study investigates the effect of moisture content, oxygen concentration and leachate components on spontaneous ignition, combustion initiation, and self-heating of solid waste. A new procedure for testing spontaneous ignition is described; however, variations in solid waste components and landfill conditions can create some limitations to its use. The presence of water and dissolved solids in leachate was found to accelerate chemical self-heating of the solid waste. Oxygen concentration at 10% by volume can sustain chemical oxidation but did not promote accelerated burning. PMID:20110161

Moqbel, Shadi; Reinhart, Debra; Chen, Ruey-Hung



Initial state angular asymmetries in high energy p+A collisions: spontaneous breaking of rotational symmetry by a color electric field and C-odd fluctuations  

E-print Network

We present a simple model for generating initial-state azimuthal asymmetries in pA collisions from dipole scattering on an anisotropic dense target. Parity even angular harmonics arise from the C-even real part of the dipole S-matrix which spontaneously breaks rotational symmetry in two dimensions due to a condensate for the color electric field. This leads to an angular correlation with the direction of $\\vec E$. Parity odd harmonics are generated by the C-odd imaginary part (odderon) due to coupling to coherent target fluctuations which again break rotational invariance. We perform a first qualitative extraction of the amplitude and cutoff of C-odd fluctuations in the dense target.

Dumitru, Adrian



Spontaneous spinal extradural hematomas.  


We review three patients who presented with acute spontaneous spinal extradural hematomas (SSEH). We discuss the presentation, imaging and management strategies. All three patients were adult women with thoracic SSEH. All had motor weakness prior to surgery. One patient recovered completely, one partially recovered and one did not recover. SSEH, although rare, should be considered in cases of acute onset paraparesis. The diagnostic modality of choice is magnetic resonance imaging. Favourable outcome is related to aetiology, interval between the ictus and presentation, and the severity of the neurological deficits. Emergent surgical drainage is the treatment of choice. PMID:16503490

Ravi, D; Dwarakanath, S; Satish, R; Gopal, S; Venkataramana, N K



Controlling gain one photon at a time  

PubMed Central

Adaptation is a salient property of sensory processing. All adaptational or gain control mechanisms face the challenge of obtaining a reliable estimate of the property of the input to be adapted to and obtaining this estimate sufficiently rapidly to be useful. Here, we explore how the primate retina balances the need to change gain rapidly and reliably when photons arrive rarely at individual rod photoreceptors. We find that the weakest backgrounds that decrease the gain of the retinal output signals are similar to those that increase human behavioral threshold, and identify a novel site of gain control in the retinal circuitry. Thus, surprisingly, the gain of retinal signals begins to decrease essentially as soon as background lights are detectable; under these conditions, gain control does not rely on a highly averaged estimate of the photon count, but instead signals from individual photon absorptions trigger changes in gain. DOI: PMID:23682314

Schwartz, Gregory W; Rieke, Fred



Gravity from spontaneous Lorentz violation  

SciTech Connect

We investigate a class of theories involving a symmetric two-tensor field in Minkowski spacetime with a potential triggering spontaneous violation of Lorentz symmetry. The resulting massless Nambu-Goldstone modes are shown to obey the linearized Einstein equations in a fixed gauge. Imposing self-consistent coupling to the energy-momentum tensor constrains the potential for the Lorentz violation. The nonlinear theory generated from the self-consistent bootstrap is an alternative theory of gravity, containing kinetic and potential terms along with a matter coupling. At energies small compared to the Planck scale, the theory contains general relativity, with the Riemann-spacetime metric constructed as a combination of the two-tensor field and the Minkowski metric. At high energies, the structure of the theory is qualitatively different from general relativity. Observable effects can arise in suitable gravitational experiments.

Kostelecky, V. Alan [Physics Department, Indiana University, Bloomington, Indiana 47405 (United States); Potting, Robertus [CENTRA, Physics Department, FCT, Universidade do Algarve, 8000-139 Faro (Portugal)



Order in spontaneous behavior.  


Brains are usually described as input/output systems: they transform sensory input into motor output. However, the motor output of brains (behavior) is notoriously variable, even under identical sensory conditions. The question of whether this behavioral variability merely reflects residual deviations due to extrinsic random noise in such otherwise deterministic systems or an intrinsic, adaptive indeterminacy trait is central for the basic understanding of brain function. Instead of random noise, we find a fractal order (resembling Lévy flights) in the temporal structure of spontaneous flight maneuvers in tethered Drosophila fruit flies. Lévy-like probabilistic behavior patterns are evolutionarily conserved, suggesting a general neural mechanism underlying spontaneous behavior. Drosophila can produce these patterns endogenously, without any external cues. The fly's behavior is controlled by brain circuits which operate as a nonlinear system with unstable dynamics far from equilibrium. These findings suggest that both general models of brain function and autonomous agents ought to include biologically relevant nonlinear, endogenous behavior-initiating mechanisms if they strive to realistically simulate biological brains or out-compete other agents. PMID:17505542

Maye, Alexander; Hsieh, Chih-Hao; Sugihara, George; Brembs, Björn



Recurrence of primary spontaneous pneumothorax  

PubMed Central

BACKGROUND: Primary spontaneous pneumothorax (PSP) is a common clinical problem and its incidence is thought to be increasing. The risk of recurrence is high and various studies quote rates of 20-60%. Factors which may or may not predispose to recurrence have not yet been established. METHODS: In a study period of four years 291 cases with a diagnosis of pneumothorax were reviewed; 153 patients with PSP were included in the study. Their risk of recurrence was analysed with particular reference to the following variables: age, sex, height and body mass index (BMI) of the patient, the initial size of pneumothorax, the smoking status of the patient, and the primary form of treatment employed. Univariate analysis was carried out by chi 2 testing and multivariate analysis was calculated by a logistic regression model. RESULTS: A retrospective study of 275 episodes of PSP in 153 patients over a four year period confirmed a high incidence of recurrence (54.2%). PSP was twice as common in men as in women, though women were significantly more likely to develop a recurrence (chi 2 = 7.58, df = 1, p < 0.01). Male height was the second most important factor, and smoking cessation the only other variable which significantly influenced the risk of recurrence. CONCLUSIONS: Analysis of several potential risk factors revealed that recurrence was not related to the BMI of the patient, the initial treatment of the pneumothorax, nor to its size. Recurrence was more common in taller men and in women. Smoking cessation appeared to reduce the risk of recurrence. These findings are discussed in the context of the possible aetiology of spontaneous pneumothorax, recurrences, and the management thereof. ??? PMID:9371212

Sadikot, R. T.; Greene, T.; Meadows, K.; Arnold, A. G.



Edge cladding gain media according to IL-11317  

SciTech Connect

In this patent application we wish to claim the following approach to ameliorating spontaneous amplified emission (ASE) that occurs in a laser amplifier slab. There are two important elements of our approach. We wish to claim the application of both together but not either one alone. (1) The first element of the invention is to roughen the edge surfaces of the amplifier slab. A rough surface with random planar features larger than the wavelength of light will reflect and refract incident light rays at angles different than the median plane of the surface. The rough surface can then be characterized by two parameters. First there is a distribution of heights about the zero mean plane of the surface. If normal this distribution is characterized by a standard deviation. The second parameter is the correlation distance that describes how close together on average are the peaks and valleys. The ratio of these two numbers determines the spread of light reflected off the surface of the edge of the slab. (2) The second element in our invention is to bond the roughened edges of the gain medium to an ASE absorbing media using a suitable bonding agent. In order for the ASE to leave the gain medium crystal there must be minimal reflection and maximum transmission at the interface. This requires having a near match of the index of refraction of the bonding medium and the amplifier slab material at the wavelength of the ASE. Further if the index of refraction of the bonding agent is less than that of the amplifier there will be some total internal reflection even if the surface is roughened. The index of refraction of GGG is {approx} 1.92 and that of YAG is {approx} 1.84. There are no suitable bonding agents with indices of refraction this high.

Soules, T



Weight Gain Prevention among Women  

Microsoft Academic Search

Objective: Women 25 to 45 years old are at risk for weight gain and future obesity. This trial was designed to evaluate the efficacy of two interventions relative to a control group in preventing weight gain among normal or overweight women and to identify demographic, behavioral, and psychosocial factors related to weight gain prevention.Research Methods and Procedures: Healthy women (N

Michele D. Levine; Mary Lou Klem; Melissa A. Kalarchian; Rena R. Wing; Lisa Weissfeld; Li Qin; Marsha D. Marcus



Single-transverse-mode large-mode-area erbium-doped fiber amplifier for high-energy pulse amplification  

Microsoft Academic Search

Efficiency of energy extraction is an important issue for high-energy pulse amplification in fiber systems. High gain in the single-mode fiber amplifier is always accompanied by a considerable amount of amplified spontaneous emission (ASE). ASE efficiently saturates the gain, thus reducing the population inversion and limiting the stored energy. An improvement in scaling these sources with single-transverse-mode output to higher

O. G. Okhotnikov; J. M. Sousa



Amplified spontaneous emission (ASE) models and approximations for thin-disk laser modeling  

NASA Astrophysics Data System (ADS)

It is well-known that amplified spontaneous emission (ASE) can be a major source of upper laser level loss in high gain pulsed or steady-state solid state lasers. This paper briefly reviews the theory of ASE and, using a simple rate equation model of the upper laser level, a geometric, radiative transport equation to describe the ASE intensity, and the perturbation method of multiple time scales, demonstrates that the loss rate of the upper laser level due to ASE adiabatically follows the spontaneous emission source term. This result which includes gain saturation is applicable to both quasi-three level and four level lasers and rigorously justifies formally using the steady-state expression derived heuristically by Lowenthal and Eggleston1 to model ASE loss in pulsed laser media. Then, it is shown that the frequency integral occurring in the ASE loss term can be evaluated analytically for both a broad "flat-top" and a Lorentzian stimulated emission lineshape but must be evaluated numerically or using an approximation due to Tommasini and Balmer2 for a Gaussian stimulated emission lineshape. It is shown that at high gain loss due to ASE is mitigated by ASE line narrowing. For a thin disk laser an approximate expression for the rate of ASE loss (or ASE lifetime) can be obtained by evaluating the remaining volume integral using either the method of Speiser3 or of Vretenar et al4. A new approximate expression for the ASE loss rate is obtained which, unlike Speiser's3 expression, accounts for ASE line narrowing and, unlike Vretenar et al's4 expression, correctly scales with the cylindrical volume of the disk. Application to both 1D and 3D laser modeling is briefly discussed.

Copeland, Drew A.



Chimeric lactase capable of spontaneous and strong immobilization on cellulose and development of a continuous-flow system for lactose hydrolysis at high temperatures.  


Recombinant plasmids containing fusion proteins composed of two different modules were constructed and expressed in Escherichia coli. The modules encoded the lactase LacA (LacZ) from the thermophilic bacterium Thermoanaerobacter ethanolicus and the cellulase CelD, a cellulose-binding module (CBM) from Anaerocellum thermophilum. The CelD CBM provides a spontaneous and strong sorption of the fusion proteins onto a cellulose carrier. The enzymatic activities of both the free LacA protein and LacA-CelD CBM fusion proteins immobilized onto the cellulose carrier were assessed. The LacA activity of the fusion protein was dependent upon its position with respect to the CBM. The highest level of lactase activity and stability was observed when the lactase domain was localized at its N terminus. A continuous-flow column reactor of lactase immobilized on a cellulose carrier was constructed, and its activity was assessed. The lactose hydrolysis rate for a 150 mM (5%) solution at a flow rate of 1 reactor volume per min was 75%, which is a value optimal for further whey transformation into glucose/galactose syrup. PMID:20935120

Velikodvorskaya, G A; Tikhonova, T V; Gurvits, I D; Karyagina, A S; Lavrova, N V; Sergienko, O V; Tashlitskii, V N; Lunina, N A; Lunin, V G



Chimeric Lactase Capable of Spontaneous and Strong Immobilization on Cellulose and Development of a Continuous-Flow System for Lactose Hydrolysis at High Temperatures?  

PubMed Central

Recombinant plasmids containing fusion proteins composed of two different modules were constructed and expressed in Escherichia coli. The modules encoded the lactase LacA (LacZ) from the thermophilic bacterium Thermoanaerobacter ethanolicus and the cellulase CelD, a cellulose-binding module (CBM) from Anaerocellum thermophilum. The CelD CBM provides a spontaneous and strong sorption of the fusion proteins onto a cellulose carrier. The enzymatic activities of both the free LacA protein and LacA-CelD CBM fusion proteins immobilized onto the cellulose carrier were assessed. The LacA activity of the fusion protein was dependent upon its position with respect to the CBM. The highest level of lactase activity and stability was observed when the lactase domain was localized at its N terminus. A continuous-flow column reactor of lactase immobilized on a cellulose carrier was constructed, and its activity was assessed. The lactose hydrolysis rate for a 150 mM (5%) solution at a flow rate of 1 reactor volume per min was 75%, which is a value optimal for further whey transformation into glucose/galactose syrup. PMID:20935120

Velikodvorskaya, G. A.; Tikhonova, T. V.; Gurvits, I. D.; Karyagina, A. S.; Lavrova, N. V.; Sergienko, O. V.; Tashlitskii, V. N.; Lunina, N. A.; Lunin, V. G.



Isolation and molecular characterization of high-performance cellobiose-fermenting spontaneous mutants of ethanologenic Escherichia coli KO11 containing the Klebsiella oxytoca casAB operon.  

PubMed Central

Escherichia coli KO11 was previously constructed to produce ethanol from acid hydrolysates of hemicellulose (pentoses and hexoses) by the chromosomal integration of Zymomonas mobilis genes encoding pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adhB). Klebsiella oxytoca P2 was constructed in an analogous fashion for the simultaneous saccharification and fermentation of cellulose and contains PTS enzymes for cellobiose. In this study, KO11 was further engineered for the fermentation of cellulose by adding the K. oxytoca casAB genes encoding Enzyme IIcellobiose and phospho-beta-glucosidase. Although the two K. oxytoca genes were well expressed in cloning hosts such as DH5 alpha, both were expressed poorly in E. coli KO11, a derivative of E. coli B. Spontaneous mutants which exhibited more than 15-fold-higher specific activities for cellobiose metabolism were isolated. The mutations of these mutants resided in the plasmid rather than the host. Three mutants were characterized by sequence analysis. All contained similar internal deletions which eliminated the casAB promoter and operator regions and placed the lacZ Shine-Dalgarno region immediately upstream from the casA Shine-Dalgarno region. KO11 harboring mutant plasmids (pLOI1908, pLOI1909, or pLOI1910) rapidly fermented cellobiose to ethanol, and the yield was more than 90% of the theoretical yield. Two of these strains were used with commercial cellulase to ferment mixed-waste office paper to ethanol. PMID:9406380

Moniruzzaman, M; Lai, X; York, S W; Ingram, L O



Gain and energy storage in holmium YLF  

NASA Technical Reports Server (NTRS)

It is demonstrated that Q-switched holmium lasers are capable of high-gain and high-energy operation at 300 K. Small-signal gain coefficients of 0.50 and 0.12/cm have been measured in YLF and YAG, respectively. Small-signal gains of 0.50/cm are comparable to those achievable in Nd:YAG and are not typical of low-gain materials. This large gain in the Ho:YLF material is made possible by operating the amplifier in the ground state depletion mode. The amplifier performance data and associated analysis presented demonstrate that efficient energy storage is possible with very high excited state ion densities of the Ho 5I7 upper laser level. This is an important result since upconversion can limit the 5I7 population. Although upconversion was still present in this experiment, it was possible to achieve efficient energy storage, demonstrating that the problem is manageable even at high excitation densities in YLF.

Storm, Mark E.; Deyst, John P.



Body Weight, Not Insulin Sensitivity or Secretion, May Predict Spontaneous Weight Changes in Nondiabetic and Prediabetic Subjects  

PubMed Central

OBJECTIVE Previous studies have found that high insulin sensitivity predicts weight gain; this association has not been confirmed. Our aim was to systematically analyze metabolic predictors of spontaneous weight changes. RESEARCH DESIGN AND METHODS In 561 women and 467 men from the Relationship Between Insulin Sensitivity and Cardiovascular Disease (RISC) cohort (mean age 44 years, BMI range 19–44 kg/m2, 9% impaired glucose tolerance) followed up for 3 years, we measured insulin sensitivity (by a euglycemic clamp) and ?-cell function (by modeling of the C-peptide response to oral glucose and by acute insulin response to intravenous glucose). RESULTS Insulin sensitivity was similar in weight gainers (top 20% of the distribution of BMI changes), weight losers (bottom 20%), and weight stable subjects across quartiles of baseline BMI. By multiple logistic or linear regression analyses controlling for center, age, sex, and baseline BMI, neither insulin sensitivity nor any ?-cell function parameter showed an independent association with weight gain; this was true in normal glucose tolerance, impaired glucose tolerance, and whether subjects progressed to dysglycemia or not. Baseline BMI was significantly higher in gainers (26.1 ± 4.1 kg/m2) and losers (26.6 ± 3.7 kg/m2) than in weight stable subjects (24.8 ± 3.8 kg/m2, P < 0.0001 for both gainers and losers). Baseline waist circumference (or equivalently, BMI or weight) was a positive, independent predictor of both weight gain and weight loss (odds ratio 1.48 [95% CI 1.12–1.97]) in men and (1.67 [1.28–2.12]) in women. In men only, better insulin sensitivity was an additional independent predictor of weight loss. CONCLUSIONS Neither insulin sensitivity nor insulin secretion predicts spontaneous weight gain. Individuals who have attained a higher weight are prone to either gaining or losing weight regardless of their glucose tolerance. PMID:21617179

Rebelos, Eleni; Muscelli, Elza; Natali, Andrea; Balkau, Beverley; Mingrone, Geltrude; Piatti, Piermarco; Konrad, Thomas; Mari, Andrea; Ferrannini, Ele



Managing price, gaining profit.  


The fastest and most effective way for a company to realize maximum profit is to get its pricing right. The right price can boost profit faster than increasing volume will; the wrong price can shrink it just as quickly. Yet many otherwise tough-minded managers miss out on significant profits because they shy away from pricing decisions for fear that they will alienate their customers. Worse, if management isn't controlling its pricing policies, there's a good chance that the company's clients are manipulating them to their own advantage. McKinsey & Company's Michael Marn and Robert Rosiello show managers how to gain control of the pricing puzzle and capture untapped profit potential by using two basic concepts: the pocket price waterfall and the pocket price band. The pocket price waterfall reveals how price erodes between a company's invoice figure and the actual amount paid by the customer--the transaction price. It tracks the volume purchase discounts, early payment bonuses, and frequent customer incentives that squeeze a company's profits. The pocket price band plots the range of pocket prices over which any given unit volume of a single product sells. Wide price bands are commonplace: some manufacturers' transaction prices for a given product range 60%; one fastener supplier's price band ranged up to 500%. Managers who study their pocket price waterfalls and bands can identify unnecessary discounting at the transaction level, low-performance accounts, and misplaced marketing efforts. The problems, once identified, are typically easy and inexpensive to remedy. PMID:10121318

Marn, M V; Rosiello, R L



Acting to gain information  

NASA Technical Reports Server (NTRS)

This report is concerned with agents that act to gain information. In previous work, we developed agent models combining qualitative modeling with real-time control. That work, however, focused primarily on actions that affect physical states of the environment. The current study extends that work by explicitly considering problems of active information-gathering and by exploring specialized aspects of information-gathering in computational perception, learning, and language. In our theoretical investigations, we analyzed agents into their perceptual and action components and identified these with elements of a state-machine model of control. The mathematical properties of each was developed in isolation and interactions were then studied. We considered the complexity dimension and the uncertainty dimension and related these to intelligent-agent design issues. We also explored active information gathering in visual processing. Working within the active vision paradigm, we developed a concept of 'minimal meaningful measurements' suitable for demand-driven vision. We then developed and tested an architecture for ongoing recognition and interpretation of visual information. In the area of information gathering through learning, we explored techniques for coping with combinatorial complexity. We also explored information gathering through explicit linguistic action by considering the nature of conversational rules, coordination, and situated communication behavior.

Rosenchein, Stanley J.; Burns, J. Brian; Chapman, David; Kaelbling, Leslie P.; Kahn, Philip; Nishihara, H. Keith; Turk, Matthew



Spontaneous vaginal evisceration  

PubMed Central

Management of vaginal prolapse in the elderly lacks a uniform consensus and continues to remain challenging. The authors report a case of an elderly lady who presented with a spontaneous vaginal evisceration. She had a long-standing vaginal prolapse being controlled by a shelf pessary, which, in her case became displaced 2 weeks prior to admission. The patient underwent a laparotomy with an intent to replace the bowel back within the peritoneal cavity and repair the vault. During the pelvic floor repair, she sustained an inadvertent button-hole injury to the rectum, which was oversewn. She went on to develop a rectovaginal fistula requiring a de-functioning colostomy. The patient made good recovery subsequently. PMID:22707628

I, Siddiqui; A, Samee; C, Hall; J, Cooper; F, O'Mahony



A transformation method for equivalent infinite-gain op amp to unity-gain CCII networks  

Microsoft Academic Search

A method to obtain equivalent networks is proposed. This permits one to synthesize filters with unity-gain CCII± from well-known single infinite-gain op amp configurations. Current transmittance filters with high output impedance and voltage transmittance filters with high input impedance are obtained. These circuits have the same passive sensitivities as their op amp counterparts. So, many particular cases proposed in the

S. Celma; P. A. Martinez; J. Sabadell



Spontaneous rupture of the oesophagus  

Microsoft Academic Search

Background: The aim of this study was to evaluate the diagnosis, management and outcome of patients with spontaneous rupture of the oesophagus in a single centre. Methods: Between October 1993 and May 2007, 51 consecutive patients with spontaneous oesophageal rupture were evaluated with contrast radiology and flexible endoscopy. Patients with limited contamination who fulfilled specific criteria were managed by a

S. M. Griffin; P. J. Lamb; J. Shenfine; D. L. Richardson; D. Karat; N. Hayes



Short Wavelength Laser Gain Studies in Plasmas Produced by a Small NEODYMIUM:GLASS Slab Laser  

NASA Astrophysics Data System (ADS)

A high-power, high-repetition-rate Nd:glass laser system was developed and used to study a collisionally pumped x-ray laser scheme near 200 A. The laser system used a commercial oscillator injecting 60-psec modelocked pulses at 1053 nm into a Nd:glass zig-zag slab amplifier which was developed for this project. The amplifier was capable of producing 2-J, near-diffraction-limited pulses at repetition rates of up to 0.3 Hz. Single-pass gains of up to 7.5 were measured with storage efficiencies of 3-4%, and the gain profile was flat to within 10%. Use of air cooling and subhertz repetition rates alleviated thermal distortion, stringent coolant channel sealing requirements, and optical surface degradation. An optical system was designed which incorporated flattop rectangular beams and relay imaging to generate 15-?m -wide, uniform line foci on the target. The focused laser radiation was used to generate linear plasma columns suitable for amplified-spontaneous -emission laser output near 200 A. An electron collisionally pumped scheme in Ni-like Nb, analogous to previously demonstrated Ni-like schemes at higher Z, was investigated experimentally. A solid Nb target was irradiated with modelocked trains of pump pulses; a gain at 204 A of about 5 cm^ {-1} in a length of 3 mm at pump energies of 1.1 J/pulse was inferred from experiments in which the line focus length was varied. Comparable amounts of gain were seen following the second and third pump pulses, suggesting that an x-ray cavity might be feasible using this pumping scheme. Supporting evidence for gain was observed in the angular and temporal dependence of the emission. The measured gain was low compared to predictions, and the pump laser power appeared therefore to have been insufficient to achieve a high gain-length product. Theoretical work supporting the experimental efforts included calculation of ionization and recombination rate coefficients, development of a hydrodynamics model for the plasma cooling phase between pulses, and study of the extension of nonlinear four-wave-mixing and tripling processes to the soft x-ray regime. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Muendel, Martin Heinrich


[Spontaneous respiration versus IPPV in pigeons].  


Veterinary textbook on anaesthesia in birds that volatile anaesthetics can accumulate in the air sac system during spontaneous respiration of birds anaesthetized with inhalational anaesthetics. In order to quantify the extent of accumulation, air samples were collected from the endotracheal tube and from the left abdominal air sac of ten pigeons anaesthetized with O2, NO2, and isoflurane. In this way, O2, CO2, and isoflurane concentrations were measured continuously at two places, during both spontaneous respiration and positive pressure ventilation. During spontaneous respiration, CO2-concentrations were higher in the air sac than in the endotracheal tube in 60% of the animals. The average difference for the whole group was 0.8 volume per cent; individual differences were as high as 2.9 volume per cent. The concentration of isoflurane was on average 1.1 volume per cent lower in the abdominal air sac than in the endotracheal tube. During mechanical ventilation, the percentage of CO2 was lower in the abdominal air sac than in the endotracheal tube in all pigeons. At the same time, the differences between isoflurane concentrations in the endotracheal tube and air sac decreased. Thus the results of our study with isoflurane-anaesthetized pigeons do not support the suggestion that volatile anaesthetics accumulate in the air sacs of spontaneously breathing birds anaesthetized with inhalation anaesthetics. The results also show that, under these conditions, CO2 concentrations in the endotracheal tube can only be measured reliably during positive pressure ventilation. PMID:8322364

Sap, R; van Wandelen, R M; Hellebrekers, L J



Emergency surgery for spontaneous hemopneumothorax.  


Emergency management of spontaneous hemopneumothorax patients was retrospectively analysed in this study. From November 2009 to August 2012, 221 patients with spontaneous pneumothorax were treated in the thoracic surgery clinic. Among them, 9 (4.07%) were diagnosed with spontaneous hemopneumothorax. Chest X-ray and computed tomography were the diagnostic tools. Emergency thoracotomy was performed for 7 of 9 patients because of massive hemothorax and continuous bleeding from the chest tube. Massive hematoma was documented in 2 of 7 patients at tomography. Bridging veins and torn pleural adhesion between parietal and visceral pleura were the source of bleeding determined at thoracotomy. Hematoma evacuation, resection of bullae, ligation of pleural adhesions and apical pleurectomy were performed. Spontaneous hemopneumothorax is an emergency due to massive hemorrhage and hematoma formation. Early surgical treatment is recommended for patients with spontaneous hemopneumothorax. PMID:24953921

Tulay, Cumhur Murat; Aygün, Mert



Airflow models gaining clout  

SciTech Connect

Move over, mock-ups. So long, smoke bombs. Take a walk, wind tunnels. Computational fluid dynamics, a spaceage simulation technique, is gaining velocity in the building community. And the design of inner spaces may never be the same. CFD is an equation-intensive computer modeling method that can simulate transient and steady-state airflow patterns and temperature gradients, indoors or out. CFD is used to downsize heating, ventilating and air conditioning systems, locate air outlets, and in general, create spaces that offer creature comfort, provide quality air and use less energy. The method is good for new construction, retrofits and forensic work, for example to investigate a building fire or a contaminant. In a room, CFD helps engineers consider, over a period of time, the combined impacts of ventilation, size, shape, contents, weather, even fenestration. For its first decade or two, CFD stayed the near-exclusive domain of aerospace, defense and electronics. With few exceptions, the building community could not afford the supercomputers that were needed to run the tens of thousands of equations involved. However, in the past few years, thanks to the increasing power and decreasing cost of computers, CFD simulation became practical. Curtain wall designers are even using it, though not without some controversy. Indoor air quality specialists, smoke and fire-spread researchers, laboratory designers, energy engineers, code writers, architects, and plant and building engineers are uncharacteristically upbeat about the tool. {open_quotes}CFD modeling is so many light years ahead of design tools that exist,{close_quotes} says Mariano Rodriguez, director of research and development for architect The Hillier Group, Princeton, N.J. {open_quotes}It`s the next step up from a wind tunnel test, and you don`t need a $300,000 wind tunnel.{close_quotes}

Post, N.M.



Can LENR Energy Gains Exceed 1000?  

NASA Astrophysics Data System (ADS)

Energy gain is defined as the energy realized from reactions divided by the energy required to produce those reactions. Low Energy Nuclear Reactions (LENR) have already been measured to significantly exceed the energy gain of 10 projected from ITER,possibly 15 years from now. Electrochemical experiments using the Pd-D system have shown energy gains exceeding 10. Gas phase experiments with the Ni-H system were reported to yield energy gains of over 100. Neither of these reports has been adequately verified or reproduced. However, the question in the title still deserves consideration. If, as thought by many, it is possible to trigger nuclear reactions that yield MeV energies with chemical energies of the order of eV, then the most optimistic expectation is that LENR gains could approach one million. Hence, the very tentative answer to the question above is yes. However, if LENR could be initiated with some energy cost, and then continue to "burn," very high energy gains might be realized. Consider a match and a pile of dry logs. The phenomenon termed "heat after death" will be examined to see if it might be the initial evidence for nuclear "burning."

Nagel, David J.



Improvement of amplified spontaneous emission by encapsulating green fluorescent dye in inverted-opal titania photonic crystals.  


Amplified spontaneous emission (ASE) characteristics of a green fluorescent dye (10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1] benzo- pyrano [6,7,8-ij]quinolizin-11-one) (C545T) encapsulated in a highly ordered three-dimensional (3D) inverted-opal titania (TiO(2)) photonic crystal (PC) microcavity were studied. Due to the utilization of a TiO(2) PC, the emission spectrum was greatly narrowed and the ASE threshold, gain, and loss were significantly improved. The threshold, gain, and loss reached 1.25 mJ pulse(-1) cm(-2), 34.69 cm(-1), and 16.9 cm(-1), respectively. The possible reason for the improvement in the ASE performance by the PC is attributed to the 3D photon localization by the microcavity effect of the PC. PMID:18709061

Zhang, Dingke; Wang, Yanping; Cao, Yanling; Ma, Dongge



Over the past decade, the use of numerical reservoir simulation with high-speed electronic computers has gained wide acceptance throughout the  

E-print Network

PREFACE Over the past decade, the use of numerical reservoir simulation with high- speed electronic. For example, he may have a choice among several simulators that use different numerical methods. He may have of a wide variety of oil and gas reservoirs throughout the world. These reservoir simulators have been

Santos, Juan


Multiphase Tertiary erosion history and elevation gain of the High Plains of New Mexico and Texas: A signal of widespread mid-Tertiary lithospheric modification?  

NASA Astrophysics Data System (ADS)

The undeformed High Plains of North America are located over 1,000 km east of the nearest plate boundary but reach elevations of >2 km at their boundary with the southern Rocky Mountains. East of the mountain front elevations decrease gradually, but remain as high as 1 km in northern Texas. Despite the accumulation of extensive geological and geophysical datasets, there is no consensus on the mechanisms that caused high elevations in the region or on how these mechanisms may be linked to the history of deformation and volcanism in the neighboring Rocky Mountains. The timing of unroofing and uplift is key to differentiating between these mechanisms, but this too remains debated. A 350 km-long integrated apatite fission-track (AFT) and (U-Th)/He (AHe) east-west transect from the southern Rocky Mountains of New Mexico across the High Plains into northern Texas provides insight into the spatial and temporal variability of unroofing across this region during Cenozoic time. The southern Sangre de Cristo Range separates the High Plains of northern New Mexico from the Rio Grande Rift. At the western edge of the southern Sangre de Cristo Range, AFT and AHe data from Precambrian basement samples show an age-elevation relationship and indicate cooling and rapid unroofing through the shallow crust during the early Tertiary Laramide orogeny. At the eastern edge of the range, both AFT and AHe data record a late Tertiary cooling episode as young as mid-Miocene. Samples from Triassic sandstones on the High Plains 50 km east of the mountain front yield mid-Tertiary AFT and late Tertiary AHe dates. These data require post-depositional heating of samples to above ~110 °C, followed by at least 1.5 km of relatively rapid unroofing on the western High Plains between 17 Ma and the initiation of Ogallala Group deposition at ~12 Ma. This interval of unroofing predates the <10 Ma volcanism along the nearby Jemez lineament. The easternmost samples in the Texas Panhandle suggest that a smaller degree of post-depositional heating caused minimal annealing of fission tracks and partial resetting of the AHe system prior to cooling and unroofing during the mid-Tertiary. Together these results indicate that multiphase Tertiary cooling and unroofing on the High Plains took place over a wide region that stretches as far as 300 km east of the rugged Cordilleran front. This implies Tertiary lithospheric modification over the same spatial extent as the cause, due either to volcanism associated with the mid-Tertiary ignimbrite flareup or to the initiation of the Rio Grande Rift system. The results may therefore constrain the development of the low-velocity mantle that contributes to high elevations throughout the Rocky Mountain-High Plains region.

Landman, R.; Flowers, R. M.; Kelley, S.



Genetics Home Reference: Primary spontaneous pneumothorax  


... PubMed Recent literature OMIM Genetic disorder catalog Conditions > Primary spontaneous pneumothorax On this page: Description Genetic changes ... names Glossary definitions Reviewed November 2012 What is primary spontaneous pneumothorax? Primary spontaneous pneumothorax is an abnormal ...


Wave optics modelling of amplified spontaneous emission  

SciTech Connect

A laser works by amplified spontaneous emission (ASE) of inverted atomic ions confined in an amplifier of rod-like geometry, such that ASE radiation is directed out of both ends of the rod. The forward and backward ASE waves are coupled through the population-rate equations and cause the saturation of the lasing transition (gain saturation). Diffraction of the waves in the transverse direction is responsible for the radiation pattern (angular distribution) observed on a distant screen and for the degree of spatial coherence of the radiation. Refraction of the light also occurs due to spatial gradients in the electron density. In order to describe this situation a code has been developed which numerically solves paraxial Maxwell's equations in the time and two spatial dimensions. The code uses the Peaceman-Rachford Alternating-Direction-Implicit algorithm and is benchmarked against laboratory DYE-LASER experiments. 4 refs., 1 fig.

Ritchie, B.; Garrison, J.



Simulation of an X-ray laser in the transient gain-saturation regime  

SciTech Connect

By using the TRANS code, we performed three-dimensional calculations of amplified spontaneous emission (ASE) in X-ray lasers on the 3p-3s transition in Ne-like Ge ({lambda} = 19.6 nm) and Ti ({lambda} = 2.6 nm) operating in the transient regime upon irradiation of a flat target by a high-power picosecond laser pulse focused into a line with one or two nanosecond prepulses. The hydrodynamics and population kinetics of the active medium of X-ray lasers were calculated by using the SS-9M code. The pulse duration, the gain, the spatial structure of the laser beam and the type of influence of a 'travelling' pump wave on the ASE brightness obtained in calculations are in agreement with the experimental data. The use of the 'travelling pump wave' leads not only to the increase in the ASE brightness but also considerably reduces its angular divergence. (active media)

Starikov, F A; Volkov, V A; Gasparyan, P D; Roslov, V I [Russian Federal Nuclear Center - The All-Russian Research Institute of Experimental Physics, Sarov, Nizhnii Novgorod Region (Russian Federation)



Physics gains attraction?  

NASA Astrophysics Data System (ADS)

A recent report from the American Institute of Physics has indicated that high school enrolments in physics in the USA have reached their highest level since World War II. Figures for the last decade show an increase in the proportion of high school students taking physics from 20 to 28% (800Â 000 students now), according to Physics Today (October 1999, p 68). The report, Maintaining Momentum: High School Physics for a New Millennium , was based on a 1997 survey of high school physics teachers, the fourth such since the mid-1980s. One conclusion drawn by the report's authors was that a broader range of physics courses is now offered, with increased popularity of `conceptual' physics courses using little algebra or trigonometry over the last ten years. The proportion of students with the strongest maths abilities now taking advanced placement or second-year physics has doubled since 1987. In addition the physics appeal has been noted among high school girls, where the percentage taking physics has risen from 39 to 47% in the ten years to 1997. These female students do not, however, seem to extend their studies into advanced placements or even into teaching physics (women constitute just a quarter of high school teachers of the subject). Sadly the good news is outweighed by the fact that physics still registers the lowest enrolments of all the high school sciences - about half those in chemistry for example. Indeed only around 1% of high school students have taken two years of physics before they graduate, which represents a much lower proportion than in many European and Asian countries. The full report can be viewed at the AIP's statistics division's homepage: whilst summaries of the document are available free from the AIP, Education and Employment Statistics Division, One Physics Ellipse, College Park, MD 20740, USA.



Optical gain characteristics of staggered InGaN quantum wells lasers Hongping Zhao and Nelson Tansu  

E-print Network

a hybrid quantum well/quantum dot laser structure Appl. Phys. Lett. 100, 041118 (2012) Time-dynamicsO/SnO nanocomposites AIP Advances 2, 012133 (2012) Ultra-broad spontaneous emission and modal gain spectrum fromOptical gain characteristics of staggered InGaN quantum wells lasers Hongping Zhao and Nelson Tansu

Gilchrist, James F.


Predicting Gains in Dementia Caregiving  

Microsoft Academic Search

Background: Caregiver gain is an important yet less-explored phenomenon. Being conceptually distinct from burden, factors associated with burden and gain can differ. This study aims to explore factors associated with the experience of gains in dementia caregiving. Method: Cross-sectional study involving caregivers recruited from a tertiary hospital dementia clinic and the local Alzheimer’s Association. Caregivers completed a questionnaire containing the

Tau Ming Liew; Nan Luo; Wai Yee Ng; Hui Ling Chionh; Jenny Goh; Philip Yap



A stimulated spontaneous down conversion effect  

NASA Astrophysics Data System (ADS)

A ghost imaging setup having a spontaneous down conversion (SPDC) entangled photon source is considered. The experimental results prove that a change of the object reflection coefficient modifies the idler single count rate. An infrared laser acting as "signal reflected photons" source intensifies the idler single count rate. A crude explanation of this effect could be the stimulated SPDC photon pair generation. Fascinating applications arise: stimulated high intensity SPDC entangled photon sources.

Rusu, Al.; Rusu, L.



Rates of spontaneous mutation.  

PubMed Central

Rates of spontaneous mutation per genome as measured in the laboratory are remarkably similar within broad groups of organisms but differ strikingly among groups. Mutation rates in RNA viruses, whose genomes contain ca. 10(4) bases, are roughly 1 per genome per replication for lytic viruses and roughly 0.1 per genome per replication for retroviruses and a retrotransposon. Mutation rates in microbes with DNA-based chromosomes are close to 1/300 per genome per replication; in this group, therefore, rates per base pair vary inversely and hugely as genome sizes vary from 6 x 10(3) to 4 x 10(7) bases or base pairs. Mutation rates in higher eukaryotes are roughly 0.1-100 per genome per sexual generation but are currently indistinguishable from 1/300 per cell division per effective genome (which excludes the fraction of the genome in which most mutations are neutral). It is now possible to specify some of the evolutionary forces that shape these diverse mutation rates. PMID:9560386

Drake, J W; Charlesworth, B; Charlesworth, D; Crow, J F



Spontaneous fission of the heaviest elements  

SciTech Connect

Although spontaneous fission was discovered in /sup 238/U in 1940, detailed studies of the process were first made possible in the 1960's with the availability of milligram quantities of /sup 252/Cf. The advent of solid-state detectors made it possible to perform measurements of coincident fission fragments from even very short-lived spontaneous fission activities or those available in only very small quantities. Until 1971 it was believed that the main features of the mass and kinetic-energy distributions were essentially the same as those for thermal neutron-induced fission and that all low-energy fission proceeded via asymmetric mass division with total kinetic energies which could be derived by linear extrapolation from those of lighter elements. In 1971, measurements of /sup 257/Fm showed an increase in symmetric mass division with anomalously high TKE's. Subsequent experiments showed that in /sup 258/Fm and /sup 259/Fm, the most probable mass split was symmetric with very high total kinetic energy. Measurements for the heavier elements have shown symmetric mass distributions with both high and low total kinetic energies. Recent results for spontaneous fission properties of the heaviest elements are reviewed and compared with theory. 31 refs., 8 figs., 1 tab.

Hoffman, D.C.



Precision Measurement of the Undulator K Parameter using Spontaneous Radiation  

SciTech Connect

Obtaining precise values of the undulator parameter, K, is critical for producing high-gain FEL radiation. At the LCLS [1], where the FEL wavelength reaches down to 1.5 {angstrom}, the relative precision of K must satisfy ({Delta}K/K){sub rms} {approx}< 0.015% over the full length of the undulator. Transverse misalignments, construction errors, radiation damage, and temperature variations all contribute to errors in the mean K values among the undulator segments. It is therefore important to develop some means to measure relative K values, after installation and alignment. We propose a method using the angle-integrated spontaneous radiation spectrum of two nearby undulator segments, and the natural shot-to-shot energy jitter of the electron beam. Simulation of this scheme is presented using both ideal and measured undulator fields. By ''leap-frogging'' to different pairs of segments with extended separations we hope to confirm or correct the values of K, including proper tapering, over the entire 130-m long LCLS undulator.

Welch, J.J.; Arthur, J.; Emma, P.; Hastings, J.B.; Huang, Z.; Nuhn, H.D.; Stefan, P.; /SLAC; Bionta, R.M.; /LLNL, Livermore; Dejus, R.J.; Yang, B.X.; /Argonne



Should I Gain Weight?  


... middle school, but now that I'm in high school, the other guys have bulked up and I haven't. What can I do?" "All of my friends have broad shoulders and look like they lift weights. No matter what I do, I just ...


Pulsed-Periodic Generation of Laser on SR I and SR II Transitions With High Gain Under Conditions of Ionization and Recombination Plasma Inhomogeneity  

NASA Astrophysics Data System (ADS)

Parametrical investigations of pulsed-periodic strontium vapor laser are carried out. Conditions of simultaneous generation on strontium atom and ion transitions (? = 1.03 and 1.09 ?m; 2.69, 2.6, 2.92, 3.01 and 3.06 ?m; and 6.45 ?m) formed during the period of ionization plasma inhomogeneity on the leading front of the excitation pulse and on strontium ion transitions (? = 416.2 and 430.5 nm) formed during the period of recombination plasma inhomogeneity in the near afterglow of the discharge are determined. Simultaneous generation is understood as the presence of all generation lines per excitation period of high-voltage pulsed-periodic discharge in one resonator whose nontransmitting mirror has the reflection coefficient ?90% and a CaF2 plane-parallel plate without deposited coating is used as an output mirror.

Soldatov, A. N.; Mirza, S. Yu.; Polunin, Yu. P.; Shumeiko, A. S.



A brain gain with a brain drain  

Microsoft Academic Search

We study human capital depletion and formation in an economy open to out-migration, as opposed to an economy which is closed. Under the assumption of asymmetric information, the enlarged opportunities and the associated different structure of incentives can give rise to a brain gain in conjunction with a brain drain. Migration by high-skill members of its workforce notwithstanding, the home

Oded Stark; Christian Helmenstein; Alexia Prskawetz



The Efficiency Gains from Deregulation  

Microsoft Academic Search

We analyze the efficiency gains from deregulating monopolies using an equilibrium rent seeking model. McCormick, Shughart and Tollison (1984) argue that the initial effort to establish regulation dissipates the monopoly profit, limiting the gain from deregulation to the efficiency cost of monopoly. We establish conditions under which this proposition holds; in particular, the initial rent seekers must fail to anticipate

Marc Poitras; Daniel Sutter



Graphene as Gain Medium for Broadband Lasers  

E-print Network

In contrast to conventional structures, efficient non-radiative carrier recombination counteracts the appearance of optical gain in graphene. Based on a microscopic and fully quantum-mechanical study of the coupled carrier, phonon, and photon dynamics in graphene, we present a strategy to obtain a long-lived gain: Integrating graphene into a photonic crystal nanocavity and applying a high-dielectric substrate gives rise to pronounced coherent light emission suggesting the design of graphene-based laser devices covering a broad spectral range.

Jago, Roland; Knorr, Andreas; Malic, Ermin



Gain and linewidth enhancement factor in InAs quantum-dot laser diodes  

Microsoft Academic Search

Amplified spontaneous emission measurements are investigated below threshold in InAs quantum-dot lasers emitting at 1.22 ?m. The dot layer of the laser was grown in a strained quantum well (QW) on a GaAs substrate. Ground state gain is determined from cavity mode Fabry-Perot modulation. As the injection current increases, the gain rises super-linearly while changes in the index of refraction

T. C. Newell; D. J. Bossert; A. Stintz; B. Fuchs; K. J. Malloy; L. F. Lester



Spontaneous olfactory receptor neuron activity determines follower cell response properties  

PubMed Central

Noisy or spontaneous activity is common in neural systems and poses a challenge to detecting and discriminating signals. Here we use the locust to answer fundamental questions about noise in the olfactory system: Where does spontaneous activity originate? How is this activity propagated or reduced throughout multiple stages of neural processing? What mechanisms favor the detection of signals despite the presence of spontaneous activity? We found that spontaneous activity long observed in the secondary projection neurons (PNs) originates almost entirely from the primary olfactory receptor neurons (ORNs) rather than from spontaneous circuit interactions in the antennal lobe, and that spontaneous activity in ORNs tonically depolarizes the resting membrane potentials of their target PNs and local neurons (LNs), and indirectly tonically depolarizes tertiary Kenyon cells (KCs). However, because these neurons have different response thresholds, in the absence of odor stimulation, ORNs and PNs display a high spontaneous firing rate but KCs are nearly silent. Finally, we used a simulation of the olfactory network to show that discrimination of signal and noise in the KCs is best when threshold levels are set so that baseline activity in PNs persists. Our results show how the olfactory system benefits from making a signal detection decision after a point of maximal information convergence, e.g., after KCs pool inputs from many PNs. PMID:22357872

Joseph, Joby; Dunn, Felice A.; Stopfer, Mark



Brillouin optical correlation domain analysis with 4 millimeter resolution based on amplified spontaneous emission.  


A new technique for Brillouin scattering-based, distributed fiber-optic measurements of temperature and strain is proposed, analyzed, simulated, and demonstrated. Broadband Brillouin pump and signal waves are drawn from the filtered amplified spontaneous emission of an erbium-doped fiber amplifier, providing high spatial resolution. The reconstruction of the position-dependent Brillouin gain spectra along 5 cm of a silica single-mode fiber under test, with a spatial resolution of 4 mm, is experimentally demonstrated using a 25 GHz-wide amplified spontaneous emission source. A 4 mm-long localized hot spot is identified by the measurements. The uncertainty in the reconstruction of the local Brillouin frequency shift is ± 1.5 MHz. The single correlation peak between the pump and signal is scanned along a fiber under test using a mechanical variable delay line. The analysis of the expected spatial resolution and the measurement signal-to-noise ratio is provided. The measurement principle is supported by numerical simulations of the stimulated acoustic field as a function of position and time. Unlike most other Brillouin optical correlation domain analysis configurations, the proposed scheme is not restricted by the bandwidth of available electro-optic modulators, microwave synthesizers, or pattern generators. Resolution is scalable to less than one millimeter in highly nonlinear media. PMID:24921326

Cohen, Raphael; London, Yosef; Antman, Yair; Zadok, Avi



["Spontaneous perforation" of Douglas' pouch].  


"Spontaneous" perforations of Douglas's pouch are a rare complication following gynecological surgery. Three patients are reported, in which Wertheim-Meigs-operation, abdominal and vaginal hysterectomy had been performed. Laceration of the vaginal vault with opening of Douglas's pouch occurred "spontaneously" at sexual intercourse. In another patient rupture of the pelvic floor with prolapse of the intestinum was observed 7 months after colpocleisis. Small perforations may be closed through the vagina; prolapse of the intestinum requires laparotomy. PMID:11127771

Borgmann, U; Heidenreich, W



The spontaneity of media interviews  

Microsoft Academic Search

The aimof this study is to show that, for effective communication in interviews, media professionals sometimes speak spontaneously instead of reading their questions. The research question arises from the incompatibility of ideal delivery, on the one hand, and the concept of spontaneity as hesitant and therefore defective, on the other. In a 2×2(speakersxtasks) within-subject design, readings and interviews of prominent

Sabine Kowal; Mary R. Bassett; Daniel C. O'Connell



Spontaneous calf haematoma: case report.  


Spontaneous calf haematoma is a rare condition and few case reports have been published in the English literature. Common conditions like deep vein thrombosis and traumatic gastrocnemius muscle tear need to be considered when a patient presents with unilateral calf swelling and tenderness. Ultrasound and Magnetic Resonance Imaging are essential for confirmation of diagnosis. The purpose of this paper is to report on a rare case of spontaneous calf hematoma and its diagnosis and management. PMID:24814632

Zubaidah, N H; Liew, N C



Spontaneous emission spectra of optically pumped vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

We study the spontaneous emission spectra of optically pumped vertical-cavity surface-emitting lasers (VCSELs) operating below threshold. By spatial and angular filtering of the spontaneous emission spectra we can relate the observed asymmetrical shape of these spectra to the subthreshold guiding properties of the VCSELs. We find a substantial difference between VCSELs with a thin gain medium, consisting of quantum wells, and VCSELs with a thick gain medium, consisting of bulk GaAs; this difference is explained by analyzing the relative weights of thermal index guiding and carrier-induced index anti-guiding.

Hendriks, R. F. M.; Willemsen, M. B.; van Exter, M. P.; Woerdman, J. P.; Weegels, L.; Gulden, K. H.; Moser, M.



Gain measurement in a CW medium-power diode pumped Nd:YAG laser amplifier by ASE analysis  

NASA Astrophysics Data System (ADS)

Using the relation between amplified spontaneous emission intensity and gain, a set of formulas is derived for gain evaluation by comparing fluorescence yield in two different lengths of the active medium. Experimental measurements are carried out and gain is calculated by solving the derived formula. For comparison, measurements are also carried out using the probe beam method, which shows good agreement between the two methods in a typical CW medium-power diode pumped Nd:YAG amplifier.

Razzaghi, D.; Hajiesmaeilbaigi, F.; Ruzbehani, M.



Spontaneous stress fractures of the femoral neck  

SciTech Connect

The diagnosis of spontaneous stress fractures of the femoral neck, a form of insufficiency stress fracture, can be missed easily. Patients present with unremitting hip pain without a history of significant trauma or unusual increase in daily activity. The initial radiographic features include osteoporosis, minor alterations of trabecular alignment, minimal extracortical or endosteal reaction, and lucent fracture lines. Initial scintigraphic examinations performed in three of four patients showed focal increased radionuclide uptake in two and no focal abnormality in one. Emphasis is placed on the paucity of early findings. Evaluation of patients with persistent hip pain requires a high degree of clinical suspicion and close follow-up; the sequelae of undetected spontaneous fractures are subcapital fracture with displacement, angular deformity, and a vascular necrosis of the femoral head.

Dorne, H.L.; Lander, P.H.



Effect of undulations on spontaneous braid formation.  


This paper is an extension of a recent study where it was shown that forces dependent on molecular helical structure may cause two DNA molecules to spontaneously braid [R. Cortini et al., Biophys. J. 101, 875 (2011)]. Here, bending fluctuations of molecular center lines about the braid axis are incorporated into the braiding theory, which may be generalized to other helix-dependent interactions and other helical molecules. The free energy of the pair of molecules is recalculated and compared to its value without incorporating undulations. We find that the loss of configurational entropy due to confinement of the molecules in the braid is quite high. This contribution to the free energy increases the amount of attraction needed for spontaneous braiding due to helix-dependent forces. The theory will be further developed for plectonemes and braids under mechanical forces in later work. PMID:24032876

Lee, Dominic



Spontaneous Altruism by Chimpanzees and Young Children  

PubMed Central

People often act on behalf of others. They do so without immediate personal gain, at cost to themselves, and even toward unfamiliar individuals. Many researchers have claimed that such altruism emanates from a species-unique psychology not found in humans' closest living evolutionary relatives, such as the chimpanzee. In favor of this view, the few experimental studies on altruism in chimpanzees have produced mostly negative results. In contrast, we report experimental evidence that chimpanzees perform basic forms of helping in the absence of rewards spontaneously and repeatedly toward humans and conspecifics. In two comparative studies, semi–free ranging chimpanzees helped an unfamiliar human to the same degree as did human infants, irrespective of being rewarded (experiment 1) or whether the helping was costly (experiment 2). In a third study, chimpanzees helped an unrelated conspecific gain access to food in a novel situation that required subjects to use a newly acquired skill on behalf of another individual. These results indicate that chimpanzees share crucial aspects of altruism with humans, suggesting that the roots of human altruism may go deeper than previous experimental evidence suggested. PMID:17594177

Warneken, Felix; Hare, Brian; Melis, Alicia P; Hanus, Daniel; Tomasello, Michael



Geotech Smart24 data acquisition system input terminated noise seismic response adjusted test : StreckeisenSTS2-low and high gain, Guralp CMG3T and Geotech GS13 seismometers.  

SciTech Connect

Sandia National Laboratories has tested, evaluated and reported on the Geotech Smart24 data acquisition system with active Fortezza crypto card data signing and authentication in SAND2008-. One test, Input Terminated Noise, allows us to characterize the self-noise of the Smart24 system. By computing the power spectral density (PSD) of the input terminated noise time series data set and correcting for the instrument response of different seismometers, the resulting spectrum can be compared to the USGS new low noise model (NLNM) of Peterson (1996), and determine the ability of the matched system of seismometer and Smart24 to be quiet enough for any general deployment location. Four seismometer models were evaluated: the Streckeisen STS2-Low and High Gain, Guralp CMG3T and Geotech GS13 models. Each has a unique pass-band as defined by the frequency band of the instrument corrected noise spectrum that falls below the new low-noise model.

Rembold, Randy Kai; Hart, Darren M.; Harris, James Mark



Achieving yield gains in wheat.  


Wheat provides 20% of calories and protein consumed by humans. Recent genetic gains are <1% per annum (p.a.), insufficient to meet future demand. The Wheat Yield Consortium brings expertise in photosynthesis, crop adaptation and genetics to a common breeding platform. Theory suggest radiation use efficiency (RUE) of wheat could be increased ~50%; strategies include modifying specificity, catalytic rate and regulation of Rubisco, up-regulating Calvin cycle enzymes, introducing chloroplast CO(2) concentrating mechanisms, optimizing light and N distribution of canopies while minimizing photoinhibition, and increasing spike photosynthesis. Maximum yield expression will also require dynamic optimization of source: sink so that dry matter partitioning to reproductive structures is not at the cost of the roots, stems and leaves needed to maintain physiological and structural integrity. Crop development should favour spike fertility to maximize harvest index so phenology must be tailored to different photoperiods, and sensitivity to unpredictable weather must be modulated to reduce conservative responses that reduce harvest index. Strategic crossing of complementary physiological traits will be augmented with wide crossing, while genome-wide selection and high throughput phenotyping and genotyping will increase efficiency of progeny screening. To ensure investment in breeding achieves agronomic impact, sustainable crop management must also be promoted through crop improvement networks. PMID:22860982

Reynolds, Matthew; Foulkes, John; Furbank, Robert; Griffiths, Simon; King, Julie; Murchie, Erik; Parry, Martin; Slafer, Gustavo



Complex vacuum fluctuation as a chaotic “limit” set of any Kleinian group transformation and the mass spectrum of high energy particle physics via spontaneous self-organization  

Microsoft Academic Search

First we give an introduction to the E(?) quantum space-time theory from the point of view of nonlinear dynamics, complexity, string and KAM theory. Subsequently we give without proof several theorems that we consider to be fundamental to the foundation of any general theory for high energy particles interaction. The final picture seems to be a synthesis between compactified Kleinian

M. S. El Naschie



Soft x-ray laser gain measurements in a recombining plasma column  

SciTech Connect

An enhancement of approx. 100 of stimulated emission over spontaneous emission of the CVI 182 A line (one-pass gain approx. = 6.5) was measured in a recombining, magnetically confined plasma column by two independent techniques using intensity calibrated XUV monochromators. Additional confirmation that the enhancement was due to stimulated emission has been obtained with a soft x-ray mirror.

Suckewer, S.; Skinner, C.H.; Milchberg, H.; Keane, C.; Voorhees, D.



Synaptic vesicles position complexin to block spontaneous fusion  

PubMed Central

Synapses continually replenish their synaptic vesicle (SV) pools while suppressing spontaneous fusion events, thus maintaining a high dynamic range in response to physiological stimuli. The presynaptic protein complexin can both promote and inhibit fusion through interactions between its alpha-helical domain and the SNARE complex. In addition, complexin’s C-terminal half is required for the inhibition of spontaneous fusion in worm, fly, and mouse, although the molecular mechanism remains unexplained. We show here that complexin’s C-terminal domain binds lipids through a novel protein motif, permitting complexin to inhibit spontaneous exocytosis in vivo by targeting complexin to SVs. We propose that the SV pool serves as a platform to sequester and position complexin where it can intercept the rapidly assembling SNAREs and control the rate of spontaneous fusion. PMID:23352168

Wragg, Rachel T.; Snead, David; Dong, Yongming; Ramlall, Trudy F.; Menon, Indu; Bai, Jihong; Eliezer, David; Dittman, Jeremy S



Progress Toward High-Gain Laser Fusion.  

National Technical Information Service (NTIS)

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...

E. Storm



Spontaneous emission from a quantum-well GaN\\/InGaN\\/AlGaN heterostructure at high pump currents  

Microsoft Academic Search

An investigation was made of the electroluminescence spectra of a structure with an InxGa1-xN (3 nm thick) quantum well pumped by current pulses of up to 4 kA cm-2 density at T=77 and 300 K. Considerable spectral broadening (?E=150–200 meV) of nonthermal nature was observed. A preliminary study was made of the stability of this light-emitting structure pumped by high-current

I V Akimova; P G Eliseev; M A Osinski; P Perlin



A Family-Based Approach to Preventing Excessive Weight Gain  

Microsoft Academic Search

Objective: Preventing weight gain in adults and excessive weight gain in children is a high priority. We evaluated the ability of a family-based program aimed at increasing steps and cereal consumption (for breakfast and snacks) to reduce weight gain in children and adults.Research Methods and Procedures: Families (n = 105) with at least one 8- to 12-year-old child who was

Susan J. Rodearmel; Holly R. Wyatt; Mary J. Barry; Fang Dong; Dongmei Pan; Richard G. Israel; Susan S. Cho; Michael I. McBurney; James O. Hill



The Lloyd L. Gaines Collection  

NSDL National Science Digital Library

Born in 1911, Lloyd Lionel Gaines was one of eleven children. Gaines excelled in his studies and applied to the University of Missouri School of Law in 1936. He was denied admission solely on the grounds that Missouri's state constitution called for "separate education of the races." Gaines did not back down from this injustice, and he sought legal assistance from the NAACP. In 1938, Gaines won his case before the United States Supreme Court, but tragically Gaines disappeared at age 28 in Chicago and was never seen or heard from again. This engaging collection from the University of Missouri Law Library brings together documents related to Gaines's life, including photographs, family correspondence, materials related to his Supreme Court case, and related secondary materials. Visitors to the site can perform a simple search across all the materials, or dig in deeper by perform a citation search. Legal scholars will find the Case Materials area particularly engaging, as it includes links to the trial briefs, respondents' statements, and so on.


Developmental gains in visuospatial memory predict gains in mathematics achievement.  


Visuospatial competencies are related to performance in mathematical domains in adulthood, but are not consistently related to mathematics achievement in children. We confirmed the latter for first graders and demonstrated that children who show above average first-to-fifth grade gains in visuospatial memory have an advantage over other children in mathematics. The study involved the assessment of the mathematics and reading achievement of 177 children in kindergarten to fifth grade, inclusive, and their working memory capacity and processing speed in first and fifth grade. Intelligence was assessed in first grade and their second to fourth grade teachers reported on their in-class attentive behavior. Developmental gains in visuospatial memory span (d?=?2.4) were larger than gains in the capacity of the central executive (d?=?1.6) that in turn were larger than gains in phonological memory span (d?=?1.1). First to fifth grade gains in visuospatial memory and in speed of numeral processing predicted end of fifth grade mathematics achievement, as did first grade central executive scores, intelligence, and in-class attentive behavior. The results suggest there are important individual differences in the rate of growth of visuospatial memory during childhood and that these differences become increasingly important for mathematics learning. PMID:23936154

Li, Yaoran; Geary, David C



Study of gain mechanisms in AlGaN in the temperature range of 30-300 K  

NASA Astrophysics Data System (ADS)

We report the results of an experimental study of the stimulated emission (SE) properties of AlGaN epilayers grown by metalorganic chemical vapor deposition under high optical excitation conditions in the temperature range of 30-300 K. The band gap and energy position of spontaneous and SE peaks were measured over the entire temperature range studied. Through an analysis of the temperature dependence of the relative energy positions and the SE threshold, combined with absorption and time-resolved photolumine