WorldWideScience

Sample records for hot electron populations

  1. Utilizing hot electrons

    Energy Technology Data Exchange (ETDEWEB)

    Nozik, Arthur J.

    2018-03-01

    In current solar cells, any photon energy exceeding the semiconductor bandgap is lost before being collected, limiting the cell performance. Hot carrier solar cells could avoid these losses. Now, a detailed experimental study and analysis shows that this strategy could lead to an improvement of the photoconversion efficiency in practice.

  2. Time-resolved measurements of the hot-electron population in ignition-scale experiments on the National Ignition Facility (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Hohenberger, M., E-mail: mhoh@lle.rochester.edu; Stoeckl, C. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Albert, F.; Palmer, N. E.; Döppner, T.; Divol, L.; Dewald, E. L.; Bachmann, B.; MacPhee, A. G.; LaCaille, G.; Bradley, D. K. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Lee, J. J. [National Security Technologies LLC, Livermore, California 94551 (United States)

    2014-11-15

    In laser-driven inertial confinement fusion, hot electrons can preheat the fuel and prevent fusion-pellet compression to ignition conditions. Measuring the hot-electron population is key to designing an optimized ignition platform. The hot electrons in these high-intensity, laser-driven experiments, created via laser-plasma interactions, can be inferred from the bremsstrahlung generated by hot electrons interacting with the target. At the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)], the filter-fluorescer x-ray (FFLEX) diagnostic–a multichannel, hard x-ray spectrometer operating in the 20–500 keV range–has been upgraded to provide fully time-resolved, absolute measurements of the bremsstrahlung spectrum with ∼300 ps resolution. Initial time-resolved data exhibited significant background and low signal-to-noise ratio, leading to a redesign of the FFLEX housing and enhanced shielding around the detector. The FFLEX x-ray sensitivity was characterized with an absolutely calibrated, energy-dispersive high-purity germanium detector using the high-energy x-ray source at NSTec Livermore Operations over a range of K-shell fluorescence energies up to 111 keV (U K{sub β}). The detectors impulse response function was measured in situ on NIF short-pulse (∼90 ps) experiments, and in off-line tests.

  3. Interplay of hot electrons from localized and propagating plasmons.

    Science.gov (United States)

    Hoang, Chung V; Hayashi, Koki; Ito, Yasuo; Gorai, Naoki; Allison, Giles; Shi, Xu; Sun, Quan; Cheng, Zhenzhou; Ueno, Kosei; Goda, Keisuke; Misawa, Hiroaki

    2017-10-03

    Plasmon-induced hot-electron generation has recently received considerable interest and has been studied to develop novel applications in optoelectronics, photovoltaics and green chemistry. Such hot electrons are typically generated from either localized plasmons in metal nanoparticles or propagating plasmons in patterned metal nanostructures. Here we simultaneously generate these heterogeneous plasmon-induced hot electrons and exploit their cooperative interplay in a single metal-semiconductor device to demonstrate, as an example, wavelength-controlled polarity-switchable photoconductivity. Specifically, the dual-plasmon device produces a net photocurrent whose polarity is determined by the balance in population and directionality between the hot electrons from localized and propagating plasmons. The current responsivity and polarity-switching wavelength of the device can be varied over the entire visible spectrum by tailoring the hot-electron interplay in various ways. This phenomenon may provide flexibility to manipulate the electrical output from light-matter interaction and offer opportunities for biosensors, long-distance communications, and photoconversion applications.Plasmon-induced hot electrons have potential applications spanning photodetection and photocatalysis. Here, Hoang et al. study the interplay between hot electrons generated by localized and propagating plasmons, and demonstrate wavelength-controlled polarity-switchable photoconductivity.

  4. Surface-Plasmon-Driven Hot Electron Photochemistry.

    Science.gov (United States)

    Zhang, Yuchao; He, Shuai; Guo, Wenxiao; Hu, Yue; Huang, Jiawei; Mulcahy, Justin R; Wei, Wei David

    2017-11-30

    Visible-light-driven photochemistry has continued to attract heightened interest due to its capacity to efficiently harvest solar energy and its potential to solve the global energy crisis. Plasmonic nanostructures boast broadly tunable optical properties coupled with catalytically active surfaces that offer a unique opportunity for solar photochemistry. Resonant optical excitation of surface plasmons produces energetic hot electrons that can be collected to facilitate chemical reactions. This review sums up recent theoretical and experimental approaches for understanding the underlying photophysical processes in hot electron generation and discusses various electron-transfer models on both plasmonic metal nanostructures and plasmonic metal/semiconductor heterostructures. Following that are highlights of recent examples of plasmon-driven hot electron photochemical reactions within the context of both cases. The review concludes with a discussion about the remaining challenges in the field and future opportunities for addressing the low reaction efficiencies in hot-electron-induced photochemistry.

  5. MIS hot electron devices for enhancement of surface reactivity by hot electrons

    DEFF Research Database (Denmark)

    Thomsen, Lasse Bjørchmar

    A Metal-Insulator-Semiconductor (MIS) based device is developed for investigation of hot electron enhanced chemistry. A model of the device is presented explaining the key concepts of the functionality and the character- istics. The MIS hot electron emitter is fabricated using cleanroom technology...... and the process sequence is described. An Ultra High Vacuum (UHV) setup is modified to facilitate experiments with electron emission from the MIS hot electron emitters and hot electron chemistry. Simulations show the importance of keeping tunnel barrier roughness to an absolute minimum. The tunnel oxide...... to be an important energy loss center for the electrons tunneling through the oxide lowering the emission e±ciency of a factor of 10 for a 1 nm Ti layer thickness. Electron emission is observed under ambient pressure conditions and in up to 2 bars of Ar. 2 bar Ar decrease the emission current by an order...

  6. Plasmonically enhanced hot electron based photovoltaic device.

    Science.gov (United States)

    Atar, Fatih B; Battal, Enes; Aygun, Levent E; Daglar, Bihter; Bayindir, Mehmet; Okyay, Ali K

    2013-03-25

    Hot electron photovoltaics is emerging as a candidate for low cost and ultra thin solar cells. Plasmonic means can be utilized to significantly boost device efficiency. We separately form the tunneling metal-insulator-metal (MIM) junction for electron collection and the plasmon exciting MIM structure on top of each other, which provides high flexibility in plasmonic design and tunneling MIM design separately. We demonstrate close to one order of magnitude enhancement in the short circuit current at the resonance wavelengths.

  7. Production of hot electrons in mirror systems associated with ECR heating with longitudinal input of microwaves

    International Nuclear Information System (INIS)

    Zhil'tsov, V.A.; Skovoroda, A.A.; Timofeev, A.V.; Kharitonov, K.Yu.; Shcherbakov, A.G.

    1991-01-01

    Almost all experiments on ECR plasma heating are accompanied by the formation of hot electrons (i.e., electrons with energy substantially greater than the average of the bulk population). In mirror systems these electrons may determine the basic energy content (β) of the plasma. In this paper, results are presented from experimental measurements of the hot electron population resulting from ECR heating of the plasma in OGRA-4. A theoretical model is developed which describes the hot electron dynamics and the propagation of electromagnetic oscillations in the plasma self-consistently. The results obtained with this model are in agreement with experimental data

  8. Superconducting cuprate heterostructures for hot electron bolometers

    Science.gov (United States)

    Wen, B.; Yakobov, R.; Vitkalov, S. A.; Sergeev, A.

    2013-11-01

    Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La2-xSrxCuO4 layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV ˜γI3, with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ /dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area ge -ph≈1 W/K cm2 at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity.

  9. Superconducting cuprate heterostructures for hot electron bolometers

    International Nuclear Information System (INIS)

    Wen, B.; Yakobov, R.; Vitkalov, S. A.; Sergeev, A.

    2013-01-01

    Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La 2−x Sr x CuO 4 layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV∼γI 3 , with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ/dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area g e−ph ≈1 W/K cm 2 at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity

  10. Hot Electron Nanoscopy and Spectroscopy (HENs)

    KAUST Repository

    Giugni, Andrea; Torre, Bruno; Allione, Marco; Perozziello, Gerardo; Candeloro, Patrizio; Di Fabrizio, Enzo M.

    2017-01-01

    This chapter includes a brief description of different laser coupling methods with guided surface plasmon polariton (SPP) modes at the surface of a cone. It shows some devices, their electromagnetic simulations, and their optical characterization. A theoretical section illustrates the optical and quantum description of the hot charge generation rate as obtained for the SPP propagation along the nanocone in adiabatic compression. The chapter also shows some experimental results concerning the application of the hot electron nanoscopy and spectroscopy (HENs) in the so-called Schottky configuration, highlighting the sensitivity and the nanoscale resolution of the technique. The comparison with Kelvin probe and other electric atomic force microscopy (AFM) techniques points out the intrinsic advantages of the HENs. In the end, some further insights are given about the possibility of exploiting HENs with a pulsed laser at the femtosecond time scale without significant pulse broadening and dispersion.

  11. Hot Electron Nanoscopy and Spectroscopy (HENs)

    KAUST Repository

    Giugni, Andrea

    2017-08-17

    This chapter includes a brief description of different laser coupling methods with guided surface plasmon polariton (SPP) modes at the surface of a cone. It shows some devices, their electromagnetic simulations, and their optical characterization. A theoretical section illustrates the optical and quantum description of the hot charge generation rate as obtained for the SPP propagation along the nanocone in adiabatic compression. The chapter also shows some experimental results concerning the application of the hot electron nanoscopy and spectroscopy (HENs) in the so-called Schottky configuration, highlighting the sensitivity and the nanoscale resolution of the technique. The comparison with Kelvin probe and other electric atomic force microscopy (AFM) techniques points out the intrinsic advantages of the HENs. In the end, some further insights are given about the possibility of exploiting HENs with a pulsed laser at the femtosecond time scale without significant pulse broadening and dispersion.

  12. Going ballistic: Graphene hot electron transistors

    Science.gov (United States)

    Vaziri, S.; Smith, A. D.; Östling, M.; Lupina, G.; Dabrowski, J.; Lippert, G.; Mehr, W.; Driussi, F.; Venica, S.; Di Lecce, V.; Gnudi, A.; König, M.; Ruhl, G.; Belete, M.; Lemme, M. C.

    2015-12-01

    This paper reviews the experimental and theoretical state of the art in ballistic hot electron transistors that utilize two-dimensional base contacts made from graphene, i.e. graphene base transistors (GBTs). Early performance predictions that indicated potential for THz operation still hold true today, even with improved models that take non-idealities into account. Experimental results clearly demonstrate the basic functionality, with on/off current switching over several orders of magnitude, but further developments are required to exploit the full potential of the GBT device family. In particular, interfaces between graphene and semiconductors or dielectrics are far from perfect and thus limit experimental device integrity, reliability and performance.

  13. Ab initio study of hot electrons in GaAs

    OpenAIRE

    Bernardi, Marco; Vigil-Fowler, Derek; Ong, Chin Shen; Neaton, Jeffrey B.; Louie, Steven G.

    2015-01-01

    Hot carrier dynamics critically impacts the performance of electronic, optoelectronic, photovoltaic, and plasmonic devices. Hot carriers lose energy over nanometer lengths and picosecond timescales and thus are challenging to study experimentally, whereas calculations of hot carrier dynamics are cumbersome and dominated by empirical approaches. In this work, we present ab initio calculations of hot electrons in gallium arsenide (GaAs) using density functional theory and many-body perturbation...

  14. Flute-interchange stability in a hot electron plasma

    International Nuclear Information System (INIS)

    Dominguez, R.R.

    1980-01-01

    Several topics in the kinetic stability theory of flute-interchange modes in a hot electron plasma are discussed. The stability analysis of the hot-electron, curvature-driven flute-interchange mode, previously performed in a slab geometry, is extended to a cylindrical plasma. The cold electron concentration necessary for stability differs substantially from previous criteria. The inclusion of a finite temperature background plasma in the stability analysis results in an ion curvature-driven flute-interchange mode which may be stabilized by either hot-electron diamagnetic effects, hot-electron plasma density, or finite (ion) Larmor radius effects

  15. Suppression of sawtooth oscillations due to hot electrons and hot ions

    International Nuclear Information System (INIS)

    Zhang, Y.Z.; Berk, H.L.

    1989-01-01

    The theory of m = 1 kink mode stabilization is discussed in the presence of either magnetically trapped hot electrons or hot ions. For instability hot ion requires particles peaked inside the q = 1 surface, while hot electrons require that its pressure profile be increasing at the q = 1 surface. Experimentally observed sawtooth stabilization usually occurs with off-axis heating with ECRH and near axis heating with ICRH. Such heating may produce the magnetically trapped hot particle pressure profiles that are consistent with theory. 17 refs., 2 figs

  16. Simulation studies on stability of hot electron plasma

    International Nuclear Information System (INIS)

    Ohsawa, Yukiharu

    1985-01-01

    Stability of a hot electron plasma in an NBT(EBT)-like geometry is studied by using a 2-1/2 dimensional relativistic, electromagnetic particle code. For the low-frequency hot electron interchange mode, comparison of the simulation results with the analytical predictions of linear stability theory show fairly good agreement with the magnitude of the growth rates calculated without hot electron finite Larmor radius effects. Strong stabilizing effects by finite Larmor radius of the hot electrons are observed for short wavelength modes. As for the high-frequency hot electron interchange mode, there is a discrepancy between the simulation results and the theory. The high-frequency instability is not observed though a parameter regime is chosen in which the high-frequency hot electron interchange mode is theoretically predicted to grow. Strong cross-field diffusion in a poloidal direction of the hot electrons might explain the stability. Each particle has a magnetic drift velocity, and the speed of the magnetic drift is proportional to the kinetic energy of each particle. Hence, if the particles have high temperature, the spread of the magnetic drift velocity is large. This causes a strong cross-field diffusion of the hot electrons. In the simulation for this interchange mode, an enhanced temperature relaxation is observed between the hot and cold electrons although the theoretically predicted high frequency modes are stable. (Nogami, K.)

  17. Experiments on hot-electron ECRH in the Tandem Mirror Experiment-Upgrade

    International Nuclear Information System (INIS)

    Stallard, B.W.

    1983-01-01

    Experiments have begun on the Tandem Mirror Experiment Upgrade (TMX-U) using electron-cyclotron resonant heating (ECRH) to generate the hot electron populations required for thermal barrier operation (Energy E/sub eh/ approx. 50 keV, density n/sub eh/ 12 , and hot-to-cold fraction n/sub eh/n approx. 0.9). For this operation, rf power produced by 28-GHz gyrotrons is injected with extraordinary mode polarization at both fundamental and second harmonic locations. Our initial experiments, which concentrated on startup of the hot electrons, were carried out at low density ( 12 cm - 3 ) where Fokker-Planck calculations predict high heating efficiency when the electron temperature (T/sub e/) is low. Under these conditions, we produced substantial hot electron populations (diamagnetic energy > 400 J, E/sub eh/ in the range of 15 to 50 keV, and n/sub eh//n > 0.5)

  18. Hot electron effect in the dc SQUID

    International Nuclear Information System (INIS)

    Wellstood, F.C.; Clarke, J.; Urbina, C.

    1989-01-01

    The authors have investigated the temperature dependence of the noise in thin-film dc Superconducting Quantum Interference Devices (SQUIDs) down to 20 mK. The white noise measured in the early versions of our SQUIDs did not decrease as the bath temperature was lowered below 150 mK. They have attributed this saturation to a hot electron effect in the thin-film AuCu resistors shunting the Josephson junctions. A theoretical investigation showed that the temperature of the electrons in the shunts should be given by T/sub e/ = (P/ΣΩ)/sup 1/5/, where P is the power dissipated in the shunts, Ω is the shunt volume, and Σ is a proportionality constant. Experimentally, the authors found Σ=(2.4+-0.6)X10/sup 9/WK/sup -5/m/sup -3/. They have redesigned the shunts, adding large thin-film cooling fins, to increase their volume substantially. This technique has reduced T/sub e/ to about 50 mK, with a corresponding improvement in the sensitivity of the SQUIDs

  19. Nonlinear electron-acoustic rogue waves in electron-beam plasma system with non-thermal hot electrons

    Science.gov (United States)

    Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.

    2014-11-01

    The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, non-thermal hot electrons obeying a non-thermal distribution, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles on the electron beam and energetic population parameter are discussed. The results of the present investigation may be applicable in auroral zone plasma.

  20. Surface and volume photoemission of hot electrons from plasmonic nanoantennas

    DEFF Research Database (Denmark)

    Uskov, Alexander V.; Protsenko, Igor E.; Ikhsanov, Renat S.

    2014-01-01

    We theoretically compare surface- and volume-based photoelectron emission from spherical nanoparticles, obtaining analytical expressions for the emission rate in both mechanisms. We show that the surface mechanism prevails, being unaffected by detrimental hot electron collisions.......We theoretically compare surface- and volume-based photoelectron emission from spherical nanoparticles, obtaining analytical expressions for the emission rate in both mechanisms. We show that the surface mechanism prevails, being unaffected by detrimental hot electron collisions....

  1. Hot-electron nanoscopy using adiabatic compression of surface plasmons

    KAUST Repository

    Giugni, Andrea

    2013-10-20

    Surface plasmon polaritons are a central concept in nanoplasmonics and have been exploited to develop ultrasensitive chemical detection platforms, as well as imaging and spectroscopic techniques at the nanoscale. Surface plasmons can decay to form highly energetic (or hot) electrons in a process that is usually thought to be parasitic for applications, because it limits the lifetime and propagation length of surface plasmons and therefore has an adverse influence on the functionality of nanoplasmonic devices. Recently, however, it has been shown that hot electrons produced by surface plasmon decay can be harnessed to produce useful work in photodetection, catalysis and solar energy conversion. Nevertheless, the surface-plasmon-to-hot-electron conversion efficiency has been below 1% in all cases. Here we show that adiabatic focusing of surface plasmons on a Schottky diode-terminated tapered tip of nanoscale dimensions allows for a plasmon-to-hot-electron conversion efficiency of ∼30%. We further demonstrate that, with such high efficiency, hot electrons can be used for a new nanoscopy technique based on an atomic force microscopy set-up. We show that this hot-electron nanoscopy preserves the chemical sensitivity of the scanned surface and has a spatial resolution below 50 nm, with margins for improvement.

  2. Hot-electron nanoscopy using adiabatic compression of surface plasmons

    KAUST Repository

    Giugni, Andrea; Torre, Bruno; Toma, Andrea; Francardi, Marco; Malerba, Mario; Alabastri, Alessandro; Proietti Zaccaria, Remo; Stockman, Mark Mark; Di Fabrizio, Enzo M.

    2013-01-01

    Surface plasmon polaritons are a central concept in nanoplasmonics and have been exploited to develop ultrasensitive chemical detection platforms, as well as imaging and spectroscopic techniques at the nanoscale. Surface plasmons can decay to form highly energetic (or hot) electrons in a process that is usually thought to be parasitic for applications, because it limits the lifetime and propagation length of surface plasmons and therefore has an adverse influence on the functionality of nanoplasmonic devices. Recently, however, it has been shown that hot electrons produced by surface plasmon decay can be harnessed to produce useful work in photodetection, catalysis and solar energy conversion. Nevertheless, the surface-plasmon-to-hot-electron conversion efficiency has been below 1% in all cases. Here we show that adiabatic focusing of surface plasmons on a Schottky diode-terminated tapered tip of nanoscale dimensions allows for a plasmon-to-hot-electron conversion efficiency of ∼30%. We further demonstrate that, with such high efficiency, hot electrons can be used for a new nanoscopy technique based on an atomic force microscopy set-up. We show that this hot-electron nanoscopy preserves the chemical sensitivity of the scanned surface and has a spatial resolution below 50 nm, with margins for improvement.

  3. Hot electron formation in thermal barrier region of tandem mirror GAMMA 10

    International Nuclear Information System (INIS)

    Katanuma, I.; Kiwamoto, Y.; Sawada, K.; Miyoshi, S.

    1987-01-01

    We have studied the hot electron build-up by the second harmonic electron cyclotron resonance heating in the thermal barrier region of tandem mirror GAMMA 10 by using a Fokker-Planck code with self-consistent potential profile taken into account. We have found two phases in the evolution of hot electron population and the potential profile. In the first phase where the RF diffusion is dominant quick increase of the hot electron density and that of the mean energy are observed. No further increase in the mean energy is observed thereafter. The potential is the deepest during the first phase. The second phase starts in the mean-free-time of the pitch angle scattering of hot electrons on cold electrons and ions. In this phase the hot electron population increases in the rate of the pitch angle scattering. The potential dip shallows due to the accumulation of pitch angle scattered passing ions. This observation indicates the necessity of the ion pumping for maintaining the negative potential at the thermal barrier. (author)

  4. Role of hot electron transport in scintillators: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Huihui [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, Key Lab. of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen Univ. (China); Li, Qi [Physical Sciences Division, IBM TJ Watson Research Center, Yorktown Heights, NY (United States); Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Lu, Xinfu; Williams, R.T. [Department of Physics, Wake Forest University, Winston Salem, NC (United States); Qian, Yiyang [College of Engineering and Applied Science, Nanjing University (China); Wu, Yuntao [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States)

    2016-10-15

    Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab-initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte-Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Dynamics of Pierce instability of hot electron beams

    International Nuclear Information System (INIS)

    Ignatov, A.M.; Novikov, V.N.

    1986-01-01

    On the base of a new method of numerical solution of the Vlasov equation evolution of complete function of electron distribution at the injection of hot electron beams into plasma bounded with electrodes is investigated. It is shown that despite the development of electrostatic instabilities in the system the currents can run substantially exceeding the Pierce critical current

  6. Hot electron effects on the satellite spectrum of laser-produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Abdallah, J. [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM (United States); Faenov, A.Y.; Pikuz, T.A. [MISDC, NPO ' VNIIFTRI' , Mendeleevo, Moscow Region, 141570 (Russian Federation); Wilke, M.D.; Kyrala, G.A.; Clark, R.E.H. [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM (United States)

    1999-05-01

    In laser-produced plasmas, the interaction of the intense laser light with plasma electrons can produce high-energy superthermal electrons with energies in the keV range. These hot electrons can influence the level populations which determine spectral line structure. In the present paper, the effect of hot electrons on the X-ray satellite spectrum of laser-produced plasmas is studied. Calculated spectra are compared with experimental observations. Magnesium targets irradiated by three different types of laser pulses are considered. These include, a high-intensity 600 fs Nd-glass laser, a 1 ns Nd-glass laser, and a 2ns CO{sub 2} laser. The Nd-glass laser experiments were conducted recently at the Los Alamos Trident Facility and the CO{sub 2} data were recorded by MISDC. High-resolution spectra were measured near the He-like resonance line of magnesium. The calculations employ an electron energy distribution which includes a thermal and a hot electron component, as part of a detailed collisional-radiative model. Plasma parameters including electron temperature, density, and hot electron fraction are estimated by choosing best fits to the experimental measurements. The calculations show that hot electrons can cause several anomalous effects. The Li-like jkl, abcd, and qr satellites can show intensities which are generally attributed to electron densities in excess of 10{sup 23} cm{sup -3}. In addition, the relative amplitude of the intercombination line can be unusually large even at high electron densities due to enhanced collisional excitation of the 1s2p{sup 3}P state by hot electrons. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  7. Hot-electron plasma formation and confinement in the Tandem Mirror Experiment-Upgrade

    International Nuclear Information System (INIS)

    Ress, D.B.

    1988-01-01

    Electron-cyclotron range-of-frequency heating (ECRH) at 28 GHz is used to create a population of mirror-confined hot electrons in the Tandem Mirror Experiment-Upgrade (TMX-U). Generation of a large fraction of such electrons within each end-cell of TMX-U is essential to the formation of the desired electrostatic potential profile of the thermal-barrier tandem mirror. The formation and confinement of the ECRH-generated hot-electron plasma was investigated with a variety of diagnostic instruments, including a novel instrumented limiter probe. The author characterized the spatial structure of the hot-electron plasma. Details of the heating process cause the plasma to separate into two regions: a halo, consisting entirely of energetic electrons, and a core, which is dominated by cooler electrons. The plasma structure forms rapidly under the action of second-harmonic ECRH. Fundamental ECRH, which is typically applied simultaneously, is only weakly absorbed and generally does not create energetic electrons. The ECRH-generated plasma displays several loss mechanisms. Hot electrons in the halo region, with T e ∼ 30 keV, are formed by localized ECRH near the plasma boundary, and are lost through a radial process involving open magnetic-curvature-drift surfaces

  8. Study of hot electrons in a ECR ion source

    International Nuclear Information System (INIS)

    Barue, C.

    1992-12-01

    The perfecting of diagnosis connected with hot electrons of plasma, and then the behaviour of measured parameters of plasma according to parameters of source working are the purpose of this thesis. The experimental results obtained give new information on hot electrons of an ECR ion source. This thesis is divided in 4 parts: the first part presents an ECR source and the experimental configuration (ECRIS physics, minimafios GHz, diagnosis used); the second part, the diagnosis (computer code of cyclotron emission and calibration); the third part gives experimental results in continuous regime (emission cyclotron diagnosis, bremsstrahlung); the fourth part, experimental results in pulsed regime (emission cyclotron diagnosis, diamagnetism) calibration)

  9. Sheath formation of a plasma containing multiply charged ions, cold and hot electrons, and emitted electrons

    International Nuclear Information System (INIS)

    You, H.J.

    2012-01-01

    It is quite well known that ion confinement is an important factor in an electron cyclotron resonance ion source (ECRIS) as it is closely related to the plasma potential. A model of sheath formation was extended to a plasma containing multiply charged ions (MCIs), cold and hot electrons, and secondary electrons emitted either by MCIs or hot electrons. In the model, a modification of the 'Bohm criterion' was given, the sheath potential drop and the critical emission condition were also analyzed. It appears that the presence of hot electrons and emitted electrons strongly affects the sheath formation so that smaller hot electrons and larger emission current result in reduced sheath potential (or floating potential). However the sheath potential was found to become independent of the emission current J when J > J c , (where J c is the critical emission current. The paper is followed by the associated poster

  10. High frequency conductivity of hot electrons in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Amekpewu, M., E-mail: mamek219@gmail.com [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, S.Y. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Musah, R. [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, N.G. [Department of Mathematics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Abukari, S.S.; Dompreh, K.A. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana)

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac–dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons’ source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  11. Heat transfer between adsorbate and laser-heated hot electrons

    International Nuclear Information System (INIS)

    Ueba, H; Persson, B N J

    2008-01-01

    Strong short laser pulses can give rise to a strong increase in the electronic temperature at metal surfaces. Energy transfer from the hot electrons to adsorbed molecules may result in adsorbate reactions, e.g. desorption or diffusion. We point out the limitations of an often used equation to describe the heat transfer process in terms of a friction coupling. We propose a simple theory for the energy transfer between the adsorbate and hot electrons using a newly introduced heat transfer coefficient, which depends on the adsorbate temperature. We calculate the transient adsorbate temperature and the reaction yield for a Morse potential as a function of the laser fluency. The results are compared to those obtained using a conventional heat transfer equation with temperature-independent friction. It is found that our equation of energy (heat) transfer gives a significantly lower adsorbate peak temperature, which results in a large modification of the reaction yield. We also consider the heat transfer between different vibrational modes excited by hot electrons. This mode coupling provides indirect heating of the vibrational temperature in addition to the direct heating by hot electrons. The formula of heat transfer through linear mode-mode coupling of two harmonic oscillators is applied to the recent time-resolved study of carbon monoxide and atomic oxygen hopping on an ultrafast laser-heated Pt(111) surface. It is found that the maximum temperature of the frustrated translation mode can reach high temperatures for hopping, even when direct friction coupling to the hot electrons is not strong enough

  12. Nonequilibrium statistical operator in hot-electron transport theory

    International Nuclear Information System (INIS)

    Xing, D.Y.; Liu, M.

    1991-09-01

    The Nonequilibrium Statistical Operator method developed by Zubarev is generalized and applied to the study of hot-electron transport in semiconductors. The steady-state balance equations for momentum and energy are derived to the lowest order in the electron-lattice coupling. We show that the derived balance equations are exactly the same as those obtained by Lei and Ting. This equivalence stems from the fact that to the linear order in the electron-lattice coupling, two statistical density matrices have identical effect when they are used to calculate the average value of a dynamical operator. The application to the steady-state and transient hot-electron transport in multivalley semiconductors is also discussed. (author). 28 refs, 1 fig

  13. Investigation of hot cracking in deep penetration electron beam welds

    Energy Technology Data Exchange (ETDEWEB)

    Thorvaldson, W.G.

    1978-06-10

    A defect in a deep penetration electron beam weld of 304L stainless steel to 21-6-9 stainless steel has been identified as a centerline hot crack. The study discussed in this report was made to define and to eliminate the cause of cracking.

  14. Plasma relaxation of cold electrons and hot ions

    International Nuclear Information System (INIS)

    Potapenko, I.F.; Sakanaka, P.H.

    1996-01-01

    The relaxation process of a space uniform plasma composed of cold electrons and one species of hot ions studied numerically. Special attention has been paid to the deviation of relaxation from the classical picture which is characterized by a weakly non-isothermic situation. (author). 6 refs., 2 figs

  15. Quantum noise in a terahertz hot electron bolometer mixer

    NARCIS (Netherlands)

    Zhang, W.; Khosropanah, P.; Gao, J. R.; Kollberg, E. L.; Yngvesson, K. S.; Bansal, T.; Barends, R.; Klapwijk, T. M.

    2010-01-01

    We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model

  16. Ultrafast Hot Electron Induced Phase Transitions in Vanadium Dioxide

    Directory of Open Access Journals (Sweden)

    Haglund R. F.

    2013-03-01

    Full Text Available The Au/Cr/VO2/Si system was investigated in pump–probe experiments. Hot-electrons generated in the Au were found to penetrate into the underlying VO2 and couple with its lattice inducing a semiconductor-to-metal phase transition in ~2 picoseconds.

  17. Hot electron plasma equilibrium and stability in the Constance B mirror experiment

    International Nuclear Information System (INIS)

    Chen, Xing.

    1988-04-01

    An experimental study of the equilibrium and macroscopic stability property of an electron cyclotron resonance heating (ECRH) generated plasma in a minimum-B mirror is presented. The Constance B mirror is a single cell quadrupole magnetic mirror in which high beta (β ≤ 0.3) hot electron plasmas (T/sub e/≅400 keV) are created with up to 4 kW of ECRH power. The plasma equilibrium profile is hollow and resembles the baseball seam geometry of the magnet which provides the confining magnetic field. This configuration coincides with the drift orbit of deeply trapped particles. The on-axis hollowness of the hot electron density profile is 50 /+-/ 10%, and the pressure profile is at least as hollow as, if not more than, the hot electron density profile. The hollow plasma equilibrium is macroscopically stable and generated in all the experimental conditions in which the machine has been operated. Small macroscopic plasma fluctuations in the range of the hot electron curvature drift frequency sometimes occur but their growth rate is small (ω/sub i//ω/sub r/ ≤ 10 -2 ) and saturate at very low level (δB//bar B/ ≤ 10 -3 ). Particle drift reversal is predicted to occur for the model pressure profile which best fits the experimental data under the typical operating conditions. No strong instability is observed when the plasma is near the drift reversal parameter regime, despite a theoretical prediction of instability under such conditions. The experiment shows that the cold electron population has no stabilizing effect to the hot electrons, which disagrees with current hot electron stability theories and results of previous maximum-B experiments. A theoretical analysis using MHD theory shows that the compressibility can stabilize a plasma with a hollowness of 20--30% in the Constance B mirror well. 57 refs

  18. Enhanced energy deposition symmetry by hot electron transport

    International Nuclear Information System (INIS)

    Wilson, D.; Mack, J.; Stover, E.; VanHulsteyn, D.; McCall, G.; Hauer, A.

    1981-01-01

    High energy electrons produced by resonance absorption carry the CO 2 laser energy absorbed in a laser fusion pellet. The symmetrization that can be achieved by lateral transport of the hot electrons as they deposit their energy is discussed. A K/sub α/ experiment shows a surprising symmetrization of energy deposition achieved by adding a thin layer of plastic to a copper sphere. Efforts to numerically model this effect are described

  19. Microwave interaction with hot electron plasmas

    International Nuclear Information System (INIS)

    Tanaka, M.; Fujiwara, M.; Ikegami, H.

    1980-01-01

    A numerical calculation is presented of ray trajectories and cyclotron damping for toroidal plasmas using geometrical optics. In the absorption region, group velocity does not always coincide with the velocity of energy flow, therefore it should be careful to apply the geometrical optics to finite temperature plasmas. In these calculations, attention is paid mainly to the finite temperature effect on ray tracing. Some numerical results for ordinary waves are presented. Second, new cutoff and resonance appear in the plasmas with anisotropic electron temperature. This resonance frequency is shifted from the usual cyclotron resonance by an amount proportional to T 11 /mc 2 , so that one can determine T 11 when this resonance frequency is measured. A simple discussion is given. The results are presented of recent density measurement on Nagoya Bumpy Torus obtained by interferometer system with different frequencies, 35 GHz and 55 GHz. The results are different than each other in T-mode. The possible reasons for these differences are enumerated in this section

  20. Stimulated Raman scattering and hot-electron production

    International Nuclear Information System (INIS)

    Drake, R.P.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.; Campbell, E.M.; Wang, C.L.; Phillion, D.W.; Williams, E.A.; Kruer, W.L.

    1985-01-01

    High-intensity laser light can excite parametric instabilities that scatter or absorb it. One instability that can arise when laser light penetrates a plasma is sub-quarter-critical stimulated Raman (SQSR) scattering. It occurs below the quarter-critical density of the incident light and involves the decay of the incident light wave into a scattered light wave and electron plasma wave. The scattered-light wavelength ranges from 1 to 2 times that of the incident light, depending on the plasma density and temperature. This article reports studies of SQSR scattering and hot-electron production in plasmas produced by irradiating thick gold targets with up to 4 kJ of 0.53-μm light in 1-ns (FWHM) pulses. These studies have important implications for laser fusion. Hot electrons attributed to the SQSR instability can increase the difficulty of achieving high-gain implosions by penetrating and preheating the fusion fuel

  1. Ponderomotive Acceleration of Hot Electrons in Tenuous Plasmas

    International Nuclear Information System (INIS)

    Geyko, V.I.; Fraiman, G.M.; Dodin, I.Y.; Fisch, N.J.

    2009-01-01

    The oscillation-center Hamiltonian is derived for a relativistic electron injected with an arbitrary momentum in a linearly polarized laser pulse propagating in tenuous plasma, assuming that the pulse length is smaller than the plasma wavelength. For hot electrons generated at collisions with ions under intense laser drive, multiple regimes of ponderomotive acceleration are identified and the laser dispersion is shown to affect the process at plasma densities down to 10 17 cm -3 . Assuming a/γ g 0 ∼ g , where a is the normalized laser field, and γ g is the group velocity Lorentz factor. Yet γ ∼ Γ is attained within a wide range of initial conditions; hence a cutoff in the hot electron distribution is predicted

  2. Measurements of hot electrons in the Extrap T1 reversed-field pinch

    International Nuclear Information System (INIS)

    Welander, A.; Bergsaaker, H.

    1998-01-01

    The presence of an anisotropic energetic electron population in the edge region is a characteristic feature of reversed-field pinch (RFP) plasmas. In the Extrap T1 RFP, the anisotropic, parallel heat flux in the edge region measured by calorimetry was typically several hundred MWm -2 . To gain more insight into the origin of the hot electron component and to achieve time resolution of the hot electron flow during the discharge, a target probe with a soft x-ray monitor was designed, calibrated and implemented. The x-ray emission from the target was measured with a surface barrier detector covered with a set of different x-ray filters to achieve energy resolution. A calibration in the range 0.5-2 keV electron energy was performed on the same target and detector assembly using a LaB 6 cathode electron gun. The calibration data are interpolated and extrapolated numerically. A directional asymmetry of more than a factor of 100 for the higher energy electrons is observed. The hot electrons are estimated to constitute 10% of the total electron density at the edge and their energy distribution is approximated by a half-Maxwellian with a temperature slightly higher than the central electron temperature. Scalings with plasma current, as well as correlations with local Hα measurements and radial dependences, are presented. (author)

  3. Measurements of hot electrons in the Extrap T1 reversed-field pinch

    Science.gov (United States)

    Welander, A.; Bergsåker, H.

    1998-02-01

    The presence of an anisotropic energetic electron population in the edge region is a characteristic feature of reversed-field pinch (RFP) plasmas. In the Extrap T1 RFP, the anisotropic, parallel heat flux in the edge region measured by calorimetry was typically several hundred 0741-3335/40/2/011/img1. To gain more insight into the origin of the hot electron component and to achieve time resolution of the hot electron flow during the discharge, a target probe with a soft x-ray monitor was designed, calibrated and implemented. The x-ray emission from the target was measured with a surface barrier detector covered with a set of different x-ray filters to achieve energy resolution. A calibration in the range 0.5-2 keV electron energy was performed on the same target and detector assembly using a 0741-3335/40/2/011/img2 cathode electron gun. The calibration data are interpolated and extrapolated numerically. A directional asymmetry of more than a factor of 100 for the higher energy electrons is observed. The hot electrons are estimated to constitute 10% of the total electron density at the edge and their energy distribution is approximated by a half-Maxwellian with a temperature slightly higher than the central electron temperature. Scalings with plasma current, as well as correlations with local 0741-3335/40/2/011/img3 measurements and radial dependences, are presented.

  4. How well do time-integrated Kα images represent hot electron spatial distributions?

    Science.gov (United States)

    Ovchinnikov, V. M.; Kemp, G. E.; Schumacher, D. W.; Freeman, R. R.; Van Woerkom, L. D.

    2011-07-01

    A computational study is described, which addresses how well spatially resolved time-integrated Kα images recorded in intense laser-plasma experiments correlate with the distribution of "hot" (>1 MeV) electrons as they propagate through the target. The hot electron angular distribution leaving the laser-plasma region is critically important for many applications such as Fast Ignition or laser based x-ray sources; and Kα images are commonly used as a diagnostic. It is found that Kα images can easily mislead due to refluxing and other effects. Using the particle-in-cell code LSP, it is shown that a Kα image is not solely determined by the initial population of forward directed hot electrons, but rather also depends upon "delayed" hot electrons, and in fact continues to evolve long after the end of the laser interaction. Of particular note, there is a population of hot electrons created during the laser-plasma interaction that acquire a velocity direction opposite that of the laser and subsequently reflux off the front surface of the target, deflect when they encounter magnetic fields in the laser-plasma region, and then traverse the target in a wide spatial distribution. These delayed fast electrons create significant features in the Kα time-integrated images. Electrons refluxing from the sides and the back of the target are also found to play a significant role in forming the final Kα image. The relative contribution of these processes is found to vary depending on depth within target. These effects make efforts to find simple correlations between Kα images and, for example, Fast Ignition relevant parameters prone to error. Suggestions for future target design are provided.

  5. Jumping-droplet electronics hot-spot cooling

    International Nuclear Information System (INIS)

    Oh, Junho; Birbarah, Patrick; Foulkes, Thomas; Yin, Sabrina L.; Rentauskas, Michelle

    2017-01-01

    Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25°C air temperature, 20-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm), and heat flux (demonstrated to 13 W/cm"2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈ 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm"2. Finally, this work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.

  6. Jumping-droplet electronics hot-spot cooling

    Science.gov (United States)

    Oh, Junho; Birbarah, Patrick; Foulkes, Thomas; Yin, Sabrina L.; Rentauskas, Michelle; Neely, Jason; Pilawa-Podgurski, Robert C. N.; Miljkovic, Nenad

    2017-03-01

    Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm × 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25 °C air temperature, 20%-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm) and applied heat flux (demonstrated to 13 W/cm2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm2. This work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.

  7. Hot-Electron Intraband Luminescence from Single Hot Spots in Noble-Metal Nanoparticle Films

    Science.gov (United States)

    Haug, Tobias; Klemm, Philippe; Bange, Sebastian; Lupton, John M.

    2015-08-01

    Disordered noble-metal nanoparticle films exhibit highly localized and stable nonlinear light emission from subdiffraction regions upon illumination by near-infrared femtosecond pulses. Such hot spot emission spans a continuum in the visible and near-infrared spectral range. Strong plasmonic enhancement of light-matter interaction and the resulting complexity of experimental observations have prevented the development of a universal understanding of the origin of light emission. Here, we study the dependence of emission spectra on excitation irradiance and provide the most direct evidence yet that the continuum emission observed from both silver and gold nanoparticle aggregate surfaces is caused by recombination of hot electrons within the conduction band. The electron gas in the emitting particles, which is effectively decoupled from the lattice temperature for the duration of emission, reaches temperatures of several thousand Kelvin and acts as a subdiffraction incandescent light source on subpicosecond time scales.

  8. Simulations of Electron Transport in Laser Hot Spots

    International Nuclear Information System (INIS)

    Brunner, S.; Valeo, E.

    2001-01-01

    Simulations of electron transport are carried out by solving the Fokker-Planck equation in the diffusive approximation. The system of a single laser hot spot, with open boundary conditions, is systematically studied by performing a scan over a wide range of the two relevant parameters: (1) Ratio of the stopping length over the width of the hot spot. (2) Relative importance of the heating through inverse Bremsstrahlung compared to the thermalization through self-collisions. As for uniform illumination [J.P. Matte et al., Plasma Phys. Controlled Fusion 30 (1988) 1665], the bulk of the velocity distribution functions (VDFs) present a super-Gaussian dependence. However, as a result of spatial transport, the tails are observed to be well represented by a Maxwellian. A similar dependence of the distributions is also found for multiple hot spot systems. For its relevance with respect to stimulated Raman scattering, the linear Landau damping of the electron plasma wave is estimated for such VD Fs. Finally, the nonlinear Fokker-Planck simulations of the single laser hot spot system are also compared to the results obtained with the linear non-local hydrodynamic approach [A.V. Brantov et al., Phys. Plasmas 5 (1998) 2742], thus providing a quantitative limit to the latter method: The hydrodynamic approach presents more than 10% inaccuracy in the presence of temperature variations of the order delta T/T greater than or equal to 1%, and similar levels of deformation of the Gaussian shape of the Maxwellian background

  9. Terahertz hot electron bolometer waveguide mixers for GREAT

    OpenAIRE

    Pütz, P.; Honingh, C. E.; Jacobs, K.; Justen, M.; Schultz, M.; Stutzki, J.

    2012-01-01

    Supplementing the publications based on the first-light observations with the German Receiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on the...

  10. Hot deformation behavior and hot working characteristic of Nickel-base electron beam weldments

    Energy Technology Data Exchange (ETDEWEB)

    Ning, Yongquan, E-mail: ningke521@163.com [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Yao, Zekun; Guo, Hongzhen [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Fu, M.W. [Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)

    2014-01-25

    Highlights: • The Hot deformation behavior of electron beam (EB) Nickel-base weldments was investigated. • The constitutive equation represented by temperature, strain rate and true strain was developed. • Processing map approach was adopted to optimize the hot forging process of EB weldments. • True strain has a great effect on the efficiency of power dissipation (η). -- Abstract: The electron beam welding (EBW) of Nickel-base superalloys was conducted, and the cylindrical compression specimens were machined from the central part of the electron beam (EB) weldments. The hot deformation behavior of EB weldments was investigated at the temperature of 960–1140 °C and the strain rate of 0.001–1.0 s{sup −1}. The apparent activation energy of deformation was calculated to be 400 kJ/mol, and the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature was proposed for modeling of the hot deformation process of EB weldments. The processing map approach was adopted to investigate the deformation mechanisms during the hot plastic deformation and to optimize the processing parameters of EB weldments. It is found that the true strain has a significant effect on the efficiency of power dissipation (η). The η value in the safe processing domain (1140 °C, 1.0 s{sup −1}) increases from 0.32 to 0.55. In the unsafe processing domain (1080 °C, 0.001 s{sup −1}), however, the η value greatly decreases with the increase of strain. When the strain is 0.40, the efficiency of power dissipation becomes negative. The flow instability is predicted to occur since the instability parameter ξ(ε) becomes negative. The hot deformation of EB weldments can be carried out safely in the domain with the strain rate range of 0.1–1.0 s{sup −1} and the temperature range of 960–1140 °C. When the height reduction is about 50%, the optimum processing condition is (T{sub opi}: 1140 °C, ε{sub opi}: 1.0 s{sup −1}) with

  11. Hot deformation behavior and hot working characteristic of Nickel-base electron beam weldments

    International Nuclear Information System (INIS)

    Ning, Yongquan; Yao, Zekun; Guo, Hongzhen; Fu, M.W.

    2014-01-01

    Highlights: • The Hot deformation behavior of electron beam (EB) Nickel-base weldments was investigated. • The constitutive equation represented by temperature, strain rate and true strain was developed. • Processing map approach was adopted to optimize the hot forging process of EB weldments. • True strain has a great effect on the efficiency of power dissipation (η). -- Abstract: The electron beam welding (EBW) of Nickel-base superalloys was conducted, and the cylindrical compression specimens were machined from the central part of the electron beam (EB) weldments. The hot deformation behavior of EB weldments was investigated at the temperature of 960–1140 °C and the strain rate of 0.001–1.0 s −1 . The apparent activation energy of deformation was calculated to be 400 kJ/mol, and the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature was proposed for modeling of the hot deformation process of EB weldments. The processing map approach was adopted to investigate the deformation mechanisms during the hot plastic deformation and to optimize the processing parameters of EB weldments. It is found that the true strain has a significant effect on the efficiency of power dissipation (η). The η value in the safe processing domain (1140 °C, 1.0 s −1 ) increases from 0.32 to 0.55. In the unsafe processing domain (1080 °C, 0.001 s −1 ), however, the η value greatly decreases with the increase of strain. When the strain is 0.40, the efficiency of power dissipation becomes negative. The flow instability is predicted to occur since the instability parameter ξ(ε) becomes negative. The hot deformation of EB weldments can be carried out safely in the domain with the strain rate range of 0.1–1.0 s −1 and the temperature range of 960–1140 °C. When the height reduction is about 50%, the optimum processing condition is (T opi : 1140 °C, ε opi : 1.0 s −1 ) with the peak efficiency of 0

  12. High-frequency microinstabilities in hot-electron plasmas

    International Nuclear Information System (INIS)

    Chen, Y.J.; Nevins, W.M.; Smith, G.R.

    1981-01-01

    Instabilities with frequencies in the neighborhood of the electron cyclotron frequency are of interest in determining stable operating regimes of hot-electron plasmas in EBT devices and in tandem mirrors. Previous work used model distributions significantly different than those suggested by recent Fokker-Planck studies. We use much more realistic model distributions in a computer code that solves the full electromagnetic dispersion relation governing longitudinal and transverse waves in a uniform plasma. We allow for an arbitrary direction of wave propagation. Results for the whistler and upper-hybrid loss-cone instabilities are presented

  13. Perpendicular electron cyclotron emission from hot electrons in TMX-U

    International Nuclear Information System (INIS)

    James, R.A.; Ellis, R.F.; Lasnier, C.J.; Casper, T.A.; Celata, C.M.

    1984-01-01

    Perpendicular electron cyclotron emission (PECE) from the electron cyclotron resonant heating of hot electrons in TMX-U is measured at 30 to 40 and 50 to 75 GHz. This emission is optically thin and is measured at the midplane, f/sub ce/ approx. = 14 GHz, in either end cell. In the west end cell, the emission can be measured at different axial positions thus yielding the temporal history of the hot electron axial profile. These profiles are in excellent agreement with the axial diamagnetic signals. In addition, the PECE signal level correlates well with the diamagnetic signal over a wide range of hot electron densities. Preliminary results from theoretical modeling and comparisons with other diagnostics are also presented

  14. Modelling hot electron generation in short pulse target heating experiments

    Directory of Open Access Journals (Sweden)

    Sircombe N.J.

    2013-11-01

    Full Text Available Target heating experiments planned for the Orion laser facility, and electron beam driven fast ignition schemes, rely on the interaction of a short pulse high intensity laser with dense material to generate a flux of energetic electrons. It is essential that the characteristics of this electron source are well known in order to inform transport models in radiation hydrodynamics codes and allow effective evaluation of experimental results and forward modelling of future campaigns. We present results obtained with the particle in cell (PIC code EPOCH for realistic target and laser parameters, including first and second harmonic light. The hot electron distributions are characterised and their implications for onward transport and target heating are considered with the aid of the Monte-Carlo transport code THOR.

  15. Electron acoustic solitary waves in unmagnetized two electron population dense plasmas

    International Nuclear Information System (INIS)

    Mahmood, S.; Masood, W.

    2008-01-01

    The electron acoustic solitary waves are studied in unmagnetized two population electron quantum plasmas. The quantum hydrodynamic model is employed with the Sagdeev potential approach to describe the arbitrary amplitude electron acoustic waves in a two electron population dense Fermi plasma. It is found that hot electron density hump structures are formed in the subsonic region in such type of quantum plasmas. The wave amplitude as well as the width of the soliton are increased with the increase of percentage presence of cold (thinly populated) electrons in a multicomponent quantum plasma. It is found that an increase in quantum diffraction parameter broadens the nonlinear structure. Furthermore, the amplitude of the nonlinear electron acoustic wave is found to increase with the decrease in Mach number. The numerical results are also presented to understand the formation of solitons in two electron population Fermi plasmas.

  16. Fast Advection of Magnetic Fields by Hot Electrons

    International Nuclear Information System (INIS)

    Willingale, L.; Thomas, A. G. R.; Krushelnick, K.; Nilson, P. M.; Kaluza, M. C.; Dangor, A. E.; Evans, R. G.; Fernandes, P.; Haines, M. G.; Kamperidis, C.; Kingham, R. J.; Ridgers, C. P.; Sherlock, M.; Wei, M. S.; Najmudin, Z.; Bandyopadhyay, S.; Notley, M.; Minardi, S.; Tatarakis, M.; Rozmus, W.

    2010-01-01

    Experiments where a laser-generated proton beam is used to probe the megagauss strength self-generated magnetic fields from a nanosecond laser interaction with an aluminum target are presented. At intensities of 10 15 W cm -2 and under conditions of significant fast electron production and strong heat fluxes, the electron mean-free-path is long compared with the temperature gradient scale length and hence nonlocal transport is important for the dynamics of the magnetic field in the plasma. The hot electron flux transports self-generated magnetic fields away from the focal region through the Nernst effect [A. Nishiguchi et al., Phys. Rev. Lett. 53, 262 (1984)] at significantly higher velocities than the fluid velocity. Two-dimensional implicit Vlasov-Fokker-Planck modeling shows that the Nernst effect allows advection and self-generation transports magnetic fields at significantly faster than the ion fluid velocity, v N /c s ≅10.

  17. A model for hot electron phenomena: Theory and general results

    International Nuclear Information System (INIS)

    Carrillo, J.L.; Rodriquez, M.A.

    1988-10-01

    We propose a model for the description of the hot electron phenomena in semiconductors. Based on this model we are able to reproduce accurately the main characteristics observed in experiments of electric field transport, optical absorption, steady state photoluminescence and relaxation process. Our theory does not contain free nor adjustable parameters, it is very fast computerwise, and incorporates the main collision mechanisms including screening and phonon heating effects. Our description on a set of nonlinear rate equations in which the interactions are represented by coupling coefficients or effective frequencies. We calculate three coefficients from the characteristic constants and the band structure of the material. (author). 22 refs, 5 figs, 1 tab

  18. Antenna-coupled 30 THz hot electron bolometer mixers

    OpenAIRE

    Shcherbatenko, M.; Lobanov, Y.; Benderov, O.; Shurakov, A.; Ignatov, A.; Titova, N.; Finkel, M.; Maslennikov, S.; Kaurova, N.; Voronov, B.M.; Rodin, A.; Klapwijk, T.M.; Gol'tsman, G.N.

    2015-01-01

    We report on design and characterization of a superconducting Hot Electron Bolometer Mixer integrated with a logarithmic spiral antenna for mid-IR range observations. The antenna parameters have been adjusted to achieve the ultimate performance at 10 ?m (30 THz) range where O3, NH3, CO2, CH4, N2O, …. lines in the Earth’s atmosphere, in planetary atmospheres and in the interstellar space can be observed. The HEB mixer is made of a thin NbN film deposited onto a GaAs substrate. To couple the ra...

  19. Diffusion-Cooled Tantalum Hot-Electron Bolometer Mixers

    Science.gov (United States)

    Skalare, Anders; McGrath, William; Bumble, Bruce; LeDuc, Henry

    2004-01-01

    A batch of experimental diffusion-cooled hot-electron bolometers (HEBs), suitable for use as mixers having input frequencies in the terahertz range and output frequencies up to about a gigahertz, exploit the superconducting/normal-conducting transition in a thin strip of tantalum. The design and operation of these HEB mixers are based on mostly the same principles as those of a prior HEB mixer that exploited the superconducting/normal- conducting transition in a thin strip of niobium and that was described elsewhere.

  20. Quantum noise in a terahertz hot electron bolometer mixer

    OpenAIRE

    Zhang, W.; Khosropanah, P.; Gao, J. R.; Kollberg, E. L.; Yngvesson, K. S.; Bansal, T.; Barends, R.; Klapwijk, T. M.

    2010-01-01

    We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The ?-factor (the quantum efficiency ...

  1. Significance of fundamental processes of radiation chemistry in hot atom chemical processes: electron thermalization

    International Nuclear Information System (INIS)

    Nishikawa, M.

    1984-01-01

    The author briefly reviews the current understanding of the course of electron thermalization. An outline is given of the physical picture without going into mathematical details. The analogy of electron thermalization with hot atom processes is taken as guiding principle in this paper. Content: secondary electrons (generation, track structure, yields); thermalization (mechanism, time, spatial distribution); behaviour of hot electrons. (Auth.)

  2. Conceptual design and simulation investigation of an electronic cooling device powered by hot electrons

    International Nuclear Information System (INIS)

    Su, Guozhen; Zhang, Yanchao; Cai, Ling; Su, Shanhe; Chen, Jincan

    2015-01-01

    Most electronic cooling devices are powered by an external bias applied between the cold and the hot reservoirs. Here we propose a new concept of electronic cooling, in which cooling is achieved by using a reservoir of hot electrons as the power source. The cooling device incorporates two energy filters with the Lorentzian transmission function to respectively select low- and high-energy electrons for transport. Based on the proposed model, we analyze the performances of the device varying with the resonant levels and half widths of two energy filters and establish the optimal configuration of the cooling device. It is believed that such a novel device may be practically used in some nano-energy fields. - Highlights: • A new electronic cooling device powered by hot electrons is proposed. • Two energy filters are employed to select the electrons for transport. • The effects of the resonant levels and half widths of two filters are discussed. • The maximum cooling power and coefficient of performance are calculated. • The optimal configuration of the cooling device is determined.

  3. Nonplasmonic Hot-Electron Photocurrents from Mn-Doped Quantum Dots in Photoelectrochemical Cells.

    Science.gov (United States)

    Dong, Yitong; Rossi, Daniel; Parobek, David; Son, Dong Hee

    2016-03-03

    We report the measurement of the hot-electron current in a photoelectrochemical cell constructed from a glass/ITO/Al2 O3 (ITO=indium tin oxide) electrode coated with Mn-doped quantum dots, where hot electrons with a large excess kinetic energy were produced through upconversion of the excitons into hot electron hole pairs under photoexcitation at 3 eV. In our recent study (J. Am. Chem. Soc. 2015, 137, 5549), we demonstrated the generation of hot electrons in Mn-doped II-VI semiconductor quantum dots and their usefulness in photocatalytic H2 production reaction, taking advantage of the more efficient charge transfer of hot electrons compared with band-edge electrons. Here, we show that hot electrons produced in Mn-doped CdS/ZnS quantum dots possess sufficient kinetic energy to overcome the energy barrier from a 5.4-7.5 nm thick Al2 O3 layer producing a hot-electron current in photoelectrochemical cell. This work demonstrates the possibility of harvesting hot electrons not only at the interface of the doped quantum dot surface, but also far away from it, thus taking advantage of the capability of hot electrons for long-range electron transfer across a thick energy barrier. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Superconducting hot-electron bolometer: from the discovery of hot-electron phenomena to practical applications

    International Nuclear Information System (INIS)

    Shurakov, A; Lobanov, Y; Goltsman, G

    2016-01-01

    The discovery of hot-electron phenomena in a thin superconducting film in the last century was followed by numerous experimental studies of its appearance in different materials aiming for a better understanding of the phenomena and consequent implementation of terahertz detection systems for practical applications. In contrast to the competitors such as superconductor-insulator-superconductor tunnel junctions and Schottky diodes, the hot electron bolometer (HEB) did not demonstrate any frequency limitation of the detection mechanism. The latter, in conjunction with a decent performance, rapidly made the HEB mixer the most attractive candidate for heterodyne observations at frequencies above 1 THz. The successful operation of practical instruments (the Heinrich Hertz Telescope, the Receiver Lab Telescope, APEX, SOFIA, Hershel) ensures the importance of the HEB technology despite the lack of rigorous theoretical routine for predicting the performance. In this review, we provide a summary of experimental and theoretical studies devoted to understanding the HEB physics, and an overview of various fabrication routes and materials. (topical review)

  5. Stabilizing effects of hot electrons on low frequency plasma drift waves

    International Nuclear Information System (INIS)

    Huang Chaosong; Qiu Lijian; Ren Zhaoxing

    1988-01-01

    The MHD equation is used to study the stabilization of low frequency drift waves driven by density gradient of plasma in a hot electron plasma. The dispersion relation is derived, and the stabilizing effects of hot electrons are discussed. The physical mechanism for hot electron stabilization of the low frequency plasma perturbations is charge uncovering due to the hot electron component, which depends only on α, the ratio of N h /N i , but not on the value of β h . The hot electrons can reduce the growth rate of the interchange mode and drift wave driven by the plasma, and suppress the enomalous plasma transport caused by the drift wave. Without including the effectof β h , the stabilization of the interchange mode requires α≅2%, and the stabilization of the drift wave requires α≅40%. The theoretical analyses predict that the drift wave is the most dangerous low frequency instability in the hot electron plasma

  6. Hot electron attenuation of direct and scattered carriers across an epitaxial Schottky interface

    NARCIS (Netherlands)

    Parui, S.; Klandermans, P. S.; Venkatesan, S.; Scheu, C.; Banerjee, T.

    2013-01-01

    Hot electron transport of direct and scattered carriers across an epitaxial NiSi2/n-Si(111) interface, for different NiSi2 thickness, is studied using ballistic electron emission microscopy (BEEM). We find the BEEM transmission for the scattered hot electrons in NiSi2 to be significantly lower than

  7. Hot-electron effect in spin relaxation of electrically injected electrons in intrinsic Germanium.

    Science.gov (United States)

    Yu, T; Wu, M W

    2015-07-01

    The hot-electron effect in the spin relaxation of electrically injected electrons in intrinsic germanium is investigated by the kinetic spin Bloch equations both analytically and numerically. It is shown that in the weak-electric-field regime with E ≲ 0.5 kV cm(-1), our calculations have reasonable agreement with the recent transport experiment in the hot-electron spin-injection configuration (2013 Phys. Rev. Lett. 111 257204). We reveal that the spin relaxation is significantly enhanced at low temperature in the presence of weak electric field E ≲ 50 V cm(-1), which originates from the obvious center-of-mass drift effect due to the weak electron-phonon interaction, whereas the hot-electron effect is demonstrated to be less important. This can explain the discrepancy between the experimental observation and the previous theoretical calculation (2012 Phys. Rev. B 86 085202), which deviates from the experimental results by about two orders of magnitude at low temperature. It is further shown that in the strong-electric-field regime with 0.5 ≲ E ≲ 2 kV cm(-1), the spin relaxation is enhanced due to the hot-electron effect, whereas the drift effect is demonstrated to be marginal. Finally, we find that when 1.4 ≲ E ≲ 2 kV cm(-1) which lies in the strong-electric-field regime, a small fraction of electrons (≲5%) can be driven from the L to Γ valley, and the spin relaxation rates are the same for the Γ and L valleys in the intrinsic sample without impurity. With the negligible influence of the spin dynamics in the Γ valley to the whole system, the spin dynamics in the L valley can be measured from the Γ valley by the standard direct optical transition method.

  8. On the relaxation of cold electrons and hot ions

    International Nuclear Information System (INIS)

    Potapenko, I.F.; Bobylev, A.V.; Azevedo, C.A. de; Sakanaka, P.H.; Assis, A.S. de

    1998-01-01

    The relaxation process of a space uniform plasma composed of cold electrons and one species of hot ions is studied numerically using one- and two-dimensional Landau - Fokker - Planck codes. Relaxation of a monoenergetic ion beam is considered in possibly extreme temperature regimes. Special attention is paid to the deviation of the relaxation process from the classical picture, which is characterized by the close initial temperatures T e >(m e /m i ) 1/3 T i . The present results give quite a clear idea of the relaxation picture for any initial temperatures also in extreme temperature regimes. A difference scheme, preserving the number of particles and the energy, gives the possibility of solving the problem numerically without error accumulation, except for machine errors. copyright 1998 American Institute of Physics

  9. The development of terahertz superconducting hot-electron bolometric mixers

    International Nuclear Information System (INIS)

    Semenov, Alexei; Richter, Heiko; Smirnov, Konstantin; Voronov, Boris; Gol'tsman, Gregory; Huebers, Heinz-Wilhelm

    2004-01-01

    We present recent advances in the development of NbN hot-electron bolometric (HEB) mixers for flying terahertz heterodyne receivers. Three important issues have been addressed: the quality of the source NbN films, the effect of the bolometer size on the spectral properties of different planar feed antennas, and the local oscillator (LO) power required for optimal operation of the mixer. Studies of the NbN films with an atomic force microscope indicated a surface structure that may affect the performance of the smallest mixers. Measured spectral gain and noise temperature suggest that at frequencies above 2.5 THz the spiral feed provides better overall performance than the double-slot feed. Direct measurements of the optimal LO power support earlier estimates made in the framework of the uniform mixer model

  10. Hot Electron Generation and Transport Using Kα Emission

    International Nuclear Information System (INIS)

    Akli, K.U.; Stephens, R.B.; Key, M.H.; Bartal, T.; Beg, F.N.; Chawla, S.; Chen, C.D.; Fedosejevs, R.; Freeman, R.R.; Friesen, H.; Giraldez, E.; Green, J.S.; Hey, D.S.; Higginson, D.P.; Hund, J.; Jarrott, L.C.; Kemp, G.E.; King, J.A.; Kryger, A.; Lancaster, K.; LePape, S.; Link, A.; Ma, T.; Mackinnon, A.J.; MacPhee, A.G.; McLean, H.S.; Murphy, C.; Norreys, P.A.; Ovchinnikov, V.; Patel, P.K.; Ping, Y.; Sawada, H.; Schumacher, D.; Theobald, W.; Tsui, Y.Y.; Van Woerkom, L.D.; Wei, M.S.; Westover, B.; Yabuuchi, T.

    2010-01-01

    We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40(micro)m diameter wire emulating a 40(micro)m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of prepulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.

  11. Hot accretion disks with electron-positron pairs

    International Nuclear Information System (INIS)

    White, T.R.; Lightman, A.P.

    1989-01-01

    The hot thermal accretion disks of the 1970s are studied and consideration is given to the effects of electron-positron pairs, which were originally neglected. It is found that disks cooled by internally produced photons have a critical accretion rate above which equilibrium is not possible in a radial annulus centered around r = 10 GM/c-squared, where M is the mass of the central object. This confirms and extends previous work by Kusunose and Takahara. Above the critical rate, pairs are created more rapidly than they can be destroyed. Below the critical rate, there are two solutions to the disk structure, one with a high pair density and one with a low pair density. Depending on the strength of the viscosity, the critical accretion rate corresponds to a critical luminosity of about 3-10 percent of the Eddington limit. 32 refs

  12. POPULATION SYNTHESIS OF HOT SUBDWARFS: A PARAMETER STUDY

    International Nuclear Information System (INIS)

    Clausen, Drew; Wade, Richard A.; Kopparapu, Ravi Kumar; O'Shaughnessy, Richard

    2012-01-01

    Binaries that contain a hot subdwarf (sdB) star and a main-sequence companion may have interacted in the past. This binary population has historically helped determine our understanding of binary stellar evolution. We have computed a grid of binary population synthesis models using different assumptions about the minimum core mass for helium ignition, the envelope binding energy, the common-envelope ejection efficiency, the amount of mass and angular momentum lost during stable mass transfer, and the criteria for stable mass transfer on the red giant branch and in the Hertzsprung gap. These parameters separately and together can significantly change the entire predicted population of sdBs. Nonetheless, several different parameter sets can reproduce the observed subpopulation of sdB + white dwarf and sdB + M dwarf binaries, which has been used to constrain these parameters in previous studies. The period distribution of sdB + early F dwarf binaries offers a better test of different mass transfer scenarios for stars that fill their Roche lobes on the red giant branch.

  13. Electron cyclotron waves, transport and instabilities in hot plasmas

    International Nuclear Information System (INIS)

    Westerhof, E.

    1987-01-01

    A number of topics relevant to the magnetic confinement approach to the thermonuclear fusion is addressed. The absorption and emission of electron cyclotron waves in a thermal plasma with a small population of supra-thermal, streaming electrons is examined and the properties of electron cyclotron waves in a plasma with a pure loss-cone distribution are studied. A report is given on the 1-D transport code simulations that were performed to assist the interpretation of the electron cyclotron heating experiments on the TFR tokamak. Transport code simulations of sawteeth discharges in the T-10 tokamak are discussed in order to compare the predictions of different models for the sawtooth oscillations with the experimental findings. 149 refs.; 69 figs.; 7 tabs

  14. A Hot-electron Direct Detector for Radioastronomy

    Science.gov (United States)

    Karasik, B. S.; McGrath, W. R.; LeDuc, H. G.

    2000-01-01

    A new approach is proposed to improve the sensitivity of direct-detection bolometers. The idea is to adjust a speed of the thermal relaxation of hot-electrons in a nanometer size normal metal or superconductive transition edge bolometer by controlling the elastic electron mean free path. If the bolometer contacts are made of a superconductor with high critical temperature then the thermal diffusion into the contacts is absent because of the Andreev's reflection and the electron-phonon relaxation is the only mechanism for heat removal. The relaxation rate should behave as 7(exp 4)l at subkelvin temperatures (l is the electron elastic mean free path) and can be reduced by factor of 10 - 100 by decreasing l. Then an antenna- or waveguide-coupled bolometer with a time constant approx. 10(exp -3) to 10(exp -5) S at T approx. = 0.1 - 0.3 K will exhibit photon-noise limited performance in millimeter and subn-millimeter range. The bolometer will have a figure-of-merit NEk square root of tau approx. = 10(exp -22) 10(exp -21) W/Hz at 100 mK which is 10(exp 3) times smaller than that of a state-of-the-art bolometer. This will allow for a tremendous increase in speed which will have a significant impact for observational mapping applications. Alternatively, the bolometer could operate at higher temperature with still superior sensitivity This research was performed by the Center for Space Microelectronics Technology, JPL, California Institute of Technology, under the contract for NASA.

  15. Studies of instabilities and waves in a mirror confined hot electron plasma

    International Nuclear Information System (INIS)

    Huang Chaosong; Qiu Lijian; Ren Zhaoxing

    1989-01-01

    The stability of hot electron plasmas is studied. The hot electron component can stabilize the low frequency drift wave and the interchange mode driven by the plasma, which depends only on α=N h /N i , the density ratio of the hot electrons to the plasma ions, but not on the beta value and the annular structure of the hot electrons. Stabilization of the drift wave occurs for α > 40%, and that of the interchange mode for α > 5%, which allows the prediction that the interchange mode can be suppressed in hot electron plasma experiments. The experiments have been conducted in a simple mirror machine. It is observed that the plasma drives a drift wave at 40 kHz and an interchange mode at about 100 kHz. The fluctuation amplitude of the drift wave is much higher than that of the interchange mode. The hot electrons reduce the density gradient, the fluctuation amplitude and the radial loss of the plasma. On the other hand, the hot electrons drive the interchange mode and drift wave in the ion cyclotron frequency region. The effects of a cold plasma on hot electron perturbations are discussed. (author). 10 refs, 6 figs

  16. Profile modification and hot electron temperature from resonant absorption at modest intensity

    International Nuclear Information System (INIS)

    Albritton, J.R.; Langdon, A.B.

    1980-01-01

    Resonant absorption is investigated in expanding plasmas. The momentum deposition associated with the ejection of hot electrons toward low density via wavebreaking readily exceeds that of the incident laser radiation and results in significant modification of the density profile at critical. New scaling of hot electron temperature with laser and plasma parameters is presented

  17. The effect of hot electrons and surface plasmons on heterogeneous catalysis

    International Nuclear Information System (INIS)

    Kim, Sun Mi; Lee, Si Woo; Moon, Song Yi; Park, Jeong Young

    2016-01-01

    Hot electrons and surface-plasmon-driven chemistry are amongst the most actively studied research subjects because they are deeply associated with energy dissipation and the conversion processes at the surface and interfaces, which are still open questions and key issues in the surface science community. In this topical review, we give an overview of the concept of hot electrons or surface-plasmon-mediated hot electrons generated under various structural schemes (i.e. metals, metal–semiconductor, and metal–insulator–metal) and their role affecting catalytic activity in chemical reactions. We highlight recent studies on the relation between hot electrons and catalytic activity on metallic surfaces. We discuss possible mechanisms for how hot electrons participate in chemical reactions. We also introduce controlled chemistry to describe specific pathways for selectivity control in catalysis on metal nanoparticles. (topical review)

  18. Dual-mode operation of 2D material-base hot electron transistors

    KAUST Repository

    Lan, Yann-Wen; Jr., Carlos M. Torres,; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (V-CB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (V-CB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  19. Dual-mode operation of 2D material-base hot electron transistors

    KAUST Repository

    Lan, Yann-Wen

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (V-CB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (V-CB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  20. Hot-electron surface retention in intense short-pulse laser-matter interactions.

    Science.gov (United States)

    Mason, R J; Dodd, E S; Albright, B J

    2005-07-01

    Implicit hybrid plasma simulations predict that a significant fraction of the energy deposited into hot electrons can be retained near the surface of targets with steep density gradients illuminated by intense short-pulse lasers. This retention derives from the lateral transport of heated electrons randomly emitted in the presence of spontaneous magnetic fields arising near the laser spot, from geometric effects associated with a small hot-electron source, and from E fields arising in reaction to the ponderomotive force. Below the laser spot hot electrons are axially focused into a target by the B fields, and can filament in moderate Z targets by resistive Weibel-like instability, if the effective background electron temperature remains sufficiently low. Carefully engineered use of such retention in conjunction with ponderomotive density profile steepening could result in a reduced hot-electron range that aids fast ignition. Alternatively, such retention may disturb a deeper deposition needed for efficient radiography and backside fast ion generation.

  1. Superconducting Hot-Electron Submillimeter-Wave Detector

    Science.gov (United States)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    A superconducting hot-electron bolometer has been built and tested as a prototype of high-sensitivity, rapid-response detectors of submillimeter-wavelength radiation. There are diverse potential applications for such detectors, a few examples being submillimeter spectroscopy for scientific research; detection of leaking gases; detection of explosive, chemical, and biological weapons; and medical imaging. This detector is a superconducting-transition- edge device. Like other such devices, it includes a superconducting bridge that has a low heat capacity and is maintained at a critical temperature (T(sub c)) at the lower end of its superconducting-transition temperature range. Incident photons cause transient increases in electron temperature through the superconducting-transition range, thereby yielding measurable increases in electrical resistance. In this case, T(sub c) = 6 K, which is approximately the upper limit of the operating-temperature range of silicon-based bolometers heretofore used routinely in many laboratories. However, whereas the response speed of a typical silicon- based laboratory bolometer is characterized by a frequency of the order of a kilohertz, the response speed of the present device is much higher characterized by a frequency of the order of 100 MHz. For this or any bolometer, a useful figure of merit that one seeks to minimize is (NEP)(tau exp 1/2), where NEP denotes the noise-equivalent power (NEP) and the response time. This figure of merit depends primarily on the heat capacity and, for a given heat capacity, is approximately invariant. As a consequence of this approximate invariance, in designing a device having a given heat capacity to be more sensitive (to have lower NEP), one must accept longer response time (slower response) or, conversely, in designing it to respond faster, one must accept lower sensitivity. Hence, further, in order to increase both the speed of response and the sensitivity, one must make the device very small in

  2. Anisotropy effects on curvature-driven flute instabilities in a hot-electron plasma

    International Nuclear Information System (INIS)

    Spong, D.A.; Berk, H.L.; Van Dam, J.W.; Rosenbluth, M.N.

    1982-08-01

    The effects of finite parallel temperature are investigated for a hot electron plasma with sufficiently large beta that the magnetic field scale length (Δ/sub B/) is small compared with the vacuum field radius of curvature (R). Numerical and analytical estimates of stability boundaries are obtained for the four possible modes that can be treated in this limit: the conventional hot electron interchange, the high frequency hot electron interchange (ω > ω/sub ci/), the compressional Alfven mode, and the interacting pressure-driven interchange

  3. Curvature-driven instabilities in a hot-electron plasma: radial analysis

    International Nuclear Information System (INIS)

    Berk, H.L.; Van Dam, J.W.; Rosenbluth, M.N.; Spong, D.A.

    1981-12-01

    The theory of unfavorable curvature-driven instabilities is developed for a plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic theory. A z-pinch model is used to emphasize the radial structure of the problem. Stability criteria are obtained for the five possible modes of instability: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies larger than the ion cyclotron frequency), a compressional instability, a background pressure-driven interchange, and an interacting pressure-driven interchange

  4. Buildup of electrons with hot electron beam injection into a homogeneous magnetic field

    International Nuclear Information System (INIS)

    Bashko, V.A.; Krivoruchko, A.M.; Tarasov, I.K.

    1989-01-01

    The injection of the monoenergetic beam of electrons into the vacuum drift channel under the conditions when the beam current exceeds a certain threshold value involves a virtual cathode creation. The process of virtual cathode creation leads to an exchange of one-fluid movement of beam particles to three-fluid one corresponding to incident, reflected and passed through anticathode beam particles. For the monoenergetic beam case when the velocity spread Δv dr (v dr is the beam drift velocity), the beam instability was predicted in theory and was observed in experiment. Meanwhile, the injection in the drift space of the 'hot' beam having finite spread in velocities may be accompanied not only by the reflection of particles if their velocity v 1/2 (where φ is the electrostatic potential dip value, e and m are the electron charge and mass, respectively), but also the mutual Coulomb scattering of incident and reflected electrons. The scattering process leads in its turn to appearance of viscosity forces and to trapping of a part of beam electrons into the effective potential well formed by electrostatic potential dip and the viscous force potential. The interaction of travelling and trapped particles may occur even at the stage preceding the virtual electrode formation and it may influence the process of its appearance and also the current flow through the drift space. In this report there are described the experimental results on accumulation of electrons when electron beam propagates in vacuum and has a large spread in particle velocities Δv dr in the homogeneous longitudinal magnetic field when ω pe He where ω pe is the electron Langmuir frequency of beam electrons, ω He is the electron cyclotron frequency. (author) 6 refs., 2 figs

  5. Au nanoparticle-decorated silicon pyramids for plasmon-enhanced hot electron near-infrared photodetection

    Science.gov (United States)

    Qi, Zhiyang; Zhai, Yusheng; Wen, Long; Wang, Qilong; Chen, Qin; Iqbal, Sami; Chen, Guangdian; Xu, Ji; Tu, Yan

    2017-07-01

    The heterojunction between metal and silicon (Si) is an attractive route to extend the response of Si-based photodiodes into the near-infrared (NIR) region, so-called Schottky barrier diodes. Photons absorbed into a metallic nanostructure excite the surface plasmon resonances (SPRs), which can be damped non-radiatively through the creation of hot electrons. Unfortunately, the quantum efficiency of hot electron detectors remains low due to low optical absorption and poor electron injection efficiency. In this study, we propose an efficient and low-cost plasmonic hot electron NIR photodetector based on a Au nanoparticle (Au NP)-decorated Si pyramid Schottky junction. The large-area and lithography-free photodetector is realized by using an anisotropic chemical wet etching and rapid thermal annealing (RTA) of a thin Au film. We experimentally demonstrate that these hot electron detectors have broad photoresponsivity spectra in the NIR region of 1200-1475 nm, with a low dark current on the order of 10-5 A cm-2. The observed responsivities enable these devices to be competitive with other reported Si-based NIR hot electron photodetectors using perfectly periodic nanostructures. The improved performance is attributed to the pyramid surface which can enhance light trapping and the localized electric field, and the nano-sized Au NPs which are beneficial for the tunneling of hot electrons. The simple and large-area preparation processes make them suitable for large-scale thermophotovoltaic cell and low-cost NIR detection applications.

  6. Dual-mode operation of 2D material-base hot electron transistors.

    Science.gov (United States)

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  7. Importance of field-reversing ion ring formation in hot electron plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ikuta, K.

    1975-11-01

    Formation of the field reversing ion ring in the mirror confined hot electron plasma may offer a device to confine the fusion plasma even under the restriction of the present technology. (Author) (GRA)

  8. Fabrication of High-T(sub c) Hot-Electron Bolometric Mixers for Terahertz Applications

    Science.gov (United States)

    Burns, M. J.; Kleinsasser, A. W.; Delin, K. A.; Vasquez, R. P.; Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.

    1996-01-01

    Superocnducting hot-electron bolometers (HEB) represent a promising candidate for heterodyne mixing at frequencies exceeding 1 THz. Nb HEB mixers offer performance competitive with tunnel junctions without the frequency limit imposed by the superconducting energy gap.

  9. Efficient, Broadband and Wide-Angle Hot-Electron Transduction using Metal-Semiconductor Hyperbolic Metamaterials

    KAUST Repository

    Sakhdari, Maryam; Hajizadegan, Mehdi; Farhat, Mohamed; Chen, Pai-Yen

    2016-01-01

    Hot-electron devices are emerging as promising candidates for the transduction of optical radiation into electrical current, as they enable photodetection and solar/infrared energy harvesting at sub-bandgap wavelengths. Nevertheless, poor

  10. Formation of hot spots in a superconductor observed by low-temperature scanning electron microscopy

    International Nuclear Information System (INIS)

    Eichele, R.; Seifert, H.; Huebener, R.P.

    1981-01-01

    Low-temperature scanning electron microscopy can be used for the direct observation of hot spots in a superconductor. Experiments performed at 2.10 K with tim films demonstrating the method are reported

  11. Amplification of hot electron flow by the surface plasmon effect on metal–insulator–metal nanodiodes

    International Nuclear Information System (INIS)

    Lee, Changhwan; Nedrygailov, Ievgen I; Keun Lee, Young; Lee, Hyosun; Young Park, Jeong; Ahn, Changui; Jeon, Seokwoo

    2015-01-01

    Au–TiO_2–Ti nanodiodes with a metal–insulator–metal structure were used to probe hot electron flows generated upon photon absorption. Hot electrons, generated when light is absorbed in the Au electrode of the nanodiode, can travel across the TiO_2, leading to a photocurrent. Here, we demonstrate amplification of the hot electron flow by (1) localized surface plasmon resonance on plasmonic nanostructures fabricated by annealing the Au–TiO_2–Ti nanodiodes, and (2) reducing the thickness of the TiO_2. We show a correlation between changes in the morphology of the Au electrodes caused by annealing and amplification of the photocurrent. Based on the exponential dependence of the photocurrent on TiO_2 thickness, the transport mechanism for the hot electrons across the nanodiodes is proposed. (paper)

  12. Modification of the Absorption Edge of GaAs Arising from Hot-Electron Effects

    DEFF Research Database (Denmark)

    McGroddy, J. C.; Christensen, Ove

    1973-01-01

    We have observed a large enhancement of the electric-field-induced optical absorption arising from hot-electron effects in n-type GaAs at 77 K. The magnitude and field dependence of the enhancement can be approximately accounted for by a theory attributing the effect to broadening of the final...... states of the optical transitions by interaction with the nonequilibrium optical phonons produced by the hot electrons....

  13. Equivalent circuit-level model of quantum cascade lasers with integrated hot-electron and hot-phonon effects

    Science.gov (United States)

    Yousefvand, H. R.

    2017-12-01

    We report a study of the effects of hot-electron and hot-phonon dynamics on the output characteristics of quantum cascade lasers (QCLs) using an equivalent circuit-level model. The model is developed from the energy balance equation to adopt the electron temperature in the active region levels, the heat transfer equation to include the lattice temperature, the nonequilibrium phonon rate to account for the hot phonon dynamics and simplified two-level rate equations to incorporate the carrier and photon dynamics in the active region. This technique simplifies the description of the electron-phonon interaction in QCLs far from the equilibrium condition. Using the presented model, the steady and transient responses of the QCLs for a wide range of sink temperatures (80 to 320 K) are investigated and analysed. The model enables us to explain the operating characteristics found in QCLs. This predictive model is expected to be applicable to all QCL material systems operating in pulsed and cw regimes.

  14. Transport effects with hot electrons in laser fusion. Final report, October 1, 1981-February 28, 1983

    International Nuclear Information System (INIS)

    Shkarofsky, I.P.

    1983-02-01

    Two explanations are offered which can account for heat inhibition found in laser-fusion experiments. The first explanation requires an anisotorpic electron velocity distribution with a higher temperature parallel to the surface than into the surface. This provides axial heat inhibition. Lateral heat inhibition is associated with azimuthal magnetic fields. The second explanation requires the presence of both hot suprathermal and thermal electrons. The hot electrons can cause the flux limiter to decrease substantially below the free-streaming limit in an intermediate range of collisionality. Conditions for this situation occur in the coronal region. We compare a Maxwellian distribution to an exp(-v 5 /v 5 /sub c/) variation for the cold electrons and find that the flux limiter decreases more for the latter case. The effects of collisions between cold and hot electrons is also looked into. The Cartesian tensor approach is used in the above investigations with various forms for the zeroth order electron velocity distribution function

  15. Radial structure of curvature-driven instabilities in a hot-electron plasma

    International Nuclear Information System (INIS)

    Spong, D.A.; Berk, H.L.; Van Dam, J.W.

    1984-01-01

    A nonlocal analysis of curvature-driven instabilities for a hot-electron ring interacting with a warm background plasma has been made. Four different instability modes characteristic of hot-electron plasmas have been examined: the high-frequency hot-electron interchange (at frequencies larger than the ion-cyclotron frequency), the compressional Alfven instability, the interacting background pressure-driven interchange, and the conventional hot-electron interchange (at frequencies below the ion-cyclotron frequency). The decoupling condition between core and hot-electron plasmas has also been examined, and its influence on the background and hot-electron interchange stability boundaries has been studied. The assumed equilibrium plasma profiles and resulting radial mode structure differ somewhat from those used in previous local analytic estimates; however, when the analysis is calibrated to the appropriate effective radial wavelength of the nonlocal calculation, reasonable agreement is obtained. Comparison with recent experimental measurements indicates that certain of these modes may play a role in establishing operating boundaries for the ELMO Bumpy Torus-Scale (EBT-S) experiment. The calculations given here indicate the necessity of having core plasma outside the ring to prevent the destabilizing wave resonance of the precessional mode with a cold plasma

  16. Hot-electron-based solar energy conversion with metal-semiconductor nanodiodes

    Science.gov (United States)

    Lee, Young Keun; Lee, Hyosun; Lee, Changhwan; Hwang, Euyheon; Park, Jeong Young

    2016-06-01

    Energy dissipation at metal surfaces or interfaces between a metal and a dielectric generally results from elementary excitations, including phonons and electronic excitation, once external energy is deposited to the surface/interface during exothermic chemical processes or an electromagnetic wave incident. In this paper, we outline recent research activities to develop energy conversion devices based on hot electrons. We found that photon energy can be directly converted to hot electrons and that hot electrons flow through the interface of metal-semiconductor nanodiodes where a Schottky barrier is formed and the energy barrier is much lower than the work function of the metal. The detection of hot electron flow can be successfully measured using the photocurrent; we measured the photoyield of photoemission with incident photons-to-current conversion efficiency (IPCE). We also show that surface plasmons (i.e. the collective oscillation of conduction band electrons induced by interaction with an electromagnetic field) are excited on a rough metal surface and subsequently decay into secondary electrons, which gives rise to enhancement of the IPCE. Furthermore, the unique optical behavior of surface plasmons can be coupled with dye molecules, suggesting the possibility for producing additional channels for hot electron generation.

  17. Proton beam shaped by “particle lens” formed by laser-driven hot electrons

    International Nuclear Information System (INIS)

    Zhai, S. H.; Shen, B. F.; Wang, W. P.; Zhang, H.; Zhang, L. G.; Huang, S.; Xu, Z. Z.; He, S. K.; Lu, F.; Zhang, F. Q.; Deng, Z. G.; Dong, K. G.; Wang, S. Y.; Zhou, K. N.; Xie, N.; Wang, X. D.; Liu, H. J.; Zhao, Z. Q.; Gu, Y. Q.; Zhang, B. H.

    2016-01-01

    Two-dimensional tailoring of a proton beam is realized by a “particle lens” in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a “fountain-like” pattern when these hot electrons diffuse after propagating a distance.

  18. The optimization of production and control of hot-electron plasmas

    International Nuclear Information System (INIS)

    1989-01-01

    The present project was initially undertaken to develop a number of innovative concepts for using electron cyclotron heating (ECH) to enhance tokamak performance. A common feature of the various applications under consideration is efficient, spatially-localized generation of hot-electron plasmas; and the first phase of the work addressed the basic aspects of an approach to achieving this Upper Off-Resonant Heating (UORH) and open-resonator couplers to confine the weakly damped microwave power to the particular region where the hot electrons are to be generated. The results of the first year's work provided strong evidence that hot-electron plasmas with electron energies of hundreds of keV could be generated using multiple-frequency ECH and fully-toroidal open-resonator couplers. The evidence was sufficiently compelling to suggest that the project be focused on a suitable near-term application to the TEXT device

  19. Spin dependent transport of hot electrons through ultrathin epitaxial metallic films

    Energy Technology Data Exchange (ETDEWEB)

    Heindl, Emanuel

    2010-06-23

    In this work relaxation and transport of hot electrons in thin single crystalline metallic films is investigated by Ballistic Electron Emission Microscopy. The electron mean free paths are determined in an energy interval of 1 to 2 eV above the Fermi level. While fcc Au-films appear to be quite transmissive for hot electrons, the scattering lengths are much shorter for the ferromagnetic alloy FeCo revealing, furthermore, a strong spin asymmetry in hot electron transport. Additional information is gained from temperature dependent studies in combination with golden rule approaches in order to disentangle the impact of several relaxation and transport properties. It is found that bcc Fe-films are much less effective in spin filtering than films made of the FeCo-alloy. (orig.)

  20. Effects of magnetic configuration on hot electrons in highly charged ECR plasma

    International Nuclear Information System (INIS)

    Zhao, H Y; Zhao, H W; Sun, L T; Wang, H; Ma, B H; Zhang, X Zh; Li, X X; Ma, X W; Zhu, Y H; Lu, W; Shang, Y; Xie, D Z

    2009-01-01

    To investigate the hot electrons in highly charged electron cyclotron resonance (ECR) plasma, Bremsstrahlung radiations were measured on two ECR ion sources at the Institute of Modern Physics. Used as a comparative index of the mean energy of the hot electrons, a spectral temperature, T spe , is derived through a linear fitting of the spectra in a semi-logarithmic representation. The influences of the external source parameters, especially the magnetic configuration, on the hot electrons are studied systematically. This study has experimentally demonstrated the importance of high microwave frequency and high magnetic field in the electron resonance heating to produce a high density of hot electrons, which is consistent with the empirical ECR scaling laws. The experimental results have again shown that a good compromise is needed between the ion extraction and the plasma confinement for an efficient production of highly charged ion beams. In addition, this investigation has shown that the correlation between the mean energy of the hot electrons and the magnetic field gradient at the ECR is well in agreement with the theoretical models.

  1. Measurements of hot spots and electron beams in Z-pinch devices

    International Nuclear Information System (INIS)

    Deeney, C.

    1988-04-01

    Hot spots and Electron Beams have been observed in different types of Z-pinches. There is, however, no conclusive evidence on how either are formed although there has been much theoretical interest in both these phenomena. In this thesis, nanosecond time resolved and time correlated, X-ray and optical diagnostics, are performed on two different types of Z-pinch: a 4 kJ, 30 kV Gas Puff Z-pinch and a 28 kJ, 60 kV Plasma Focus. The aim being to study hot spots and electron beams, as well as characterise the plasma, two different Z-pinch devices. Computer codes are developed to analyse the energy and time resolved data obtained in this work. These codes model both, X-ray emission from a plasma and X-ray emission due to electron beam bombardment of a metal surface. The hot spot and electron beam parameters are measured, from the time correlated X-ray data using these computer codes. The electron beams and the hot spots are also correlated to the plasma behaviour and to each other. The results from both devices are compared with each other and with the theoretical work on hot spot and electron beam formation. A previously unreported 3-5 keV electron temperature plasma is identified, in the gas puff Z-pinch plasma, prior to the formation of the hot spots. it is shown, therefore, that the hot spots are more dense but not hotter than the surrounding plasma. Two distinct periods of electron beam generation are identified in both devices. (author)

  2. Monte Carlo study of electron-plasmon scattering effects on hot electron transport in GaAs

    International Nuclear Information System (INIS)

    Popov, V.V.; Bagaeva, T.Yu.; Solodkaya, T.I.

    1994-07-01

    It is shown using Monte Carlo simulation that electron-plasmon scattering affects substantially the hot-electron energy distribution function and transport properties in bulk GaAs. However, this effect is found to be much less than that predicted in earlier paper of other authors. (author). 5 refs, 7 figs

  3. Size dependence investigations of hot electron cooling dynamics in metal/adsorbates nanoparticles

    International Nuclear Information System (INIS)

    Bauer, Christophe; Abid, Jean-Pierre; Girault, Hubert H.

    2005-01-01

    The size dependence of electron-phonon coupling rate has been investigated by femtosecond transient absorption spectroscopy for gold nanoparticles (NPs) wrapped in a shell of sulfate with diameter varying from 1.7 to 9.2 nm. Broad-band spectroscopy gives an overview of the complex dynamics of nonequilibrium electrons and permits the choice of an appropriate probe wavelength for studying the electron-phonon coupling dynamics. Ultrafast experiments were performed in the weak perturbation regime (less than one photon in average per nanoparticle), which allows the direct extraction of the hot electron cooling rates in order to compare different NPs sizes under the same conditions. Spectroscopic data reveals a decrease of hot electron energy loss rates with metal/adsorbates nanosystem sizes. Electron-phonon coupling time constants obtained for 9.2 nm NPs are similar to gold bulk materials (∼1 ps) whereas an increase of hot electron cooling time up to 1.9 ps is observed for sizes of 1.7 nm. This is rationalized by the domination of surface effects over size (bulk) effects. The slow hot electron cooling is attributed to the adsorbates-induced long-lived nonthermal regime, which significantly reduces the electron-phonon coupling strength (average rate of phonon emission)

  4. Electronic oscillations in a hot plasma due the non-Maxwellian velocity distributions

    International Nuclear Information System (INIS)

    Dias, L.A.V.; Nakamura, Y.

    1977-01-01

    In a completely ionized hot plasma, with a non-Maxwellian electron velocity distribution, it is shown that, depending on the electron temperature, oscillations may occur at the elctron plasma and gyro frequencies. For three different electron velocity distributions, it is shown the oscillations dependency on the temperature. This situation occurs in the ionospheric plasma when artificially heated by HF radio waves. If the distribution is Maxwellian, the oscillation only occur near the electron plasma frequency [pt

  5. Efficient, Broadband and Wide-Angle Hot-Electron Transduction using Metal-Semiconductor Hyperbolic Metamaterials

    KAUST Repository

    Sakhdari, Maryam

    2016-05-20

    Hot-electron devices are emerging as promising candidates for the transduction of optical radiation into electrical current, as they enable photodetection and solar/infrared energy harvesting at sub-bandgap wavelengths. Nevertheless, poor photoconversion quantum yields and low bandwidth pose fundamental challenge to fascinating applications of hot-electron optoelectronics. Based on a novel hyperbolic metamaterial (HMM) structure, we theoretically propose a vertically-integrated hot-electron device that can efficiently couple plasmonic excitations into electron flows, with an external quantum efficiency approaching the physical limit. Further, this metamaterial-based device can have a broadband and omnidirectional response at infrared and visible wavelengths. We believe that these findings may shed some light on designing practical devices for energy-efficient photodetection and energy harvesting beyond the bandgap spectral limit.

  6. Interlayer electron-hole pair multiplication by hot carriers in atomic layer semiconductor heterostructures

    Science.gov (United States)

    Barati, Fatemeh; Grossnickle, Max; Su, Shanshan; Lake, Roger; Aji, Vivek; Gabor, Nathaniel

    Two-dimensional heterostructures composed of atomically thin transition metal dichalcogenides provide the opportunity to design novel devices for the study of electron-hole pair multiplication. We report on highly efficient multiplication of interlayer electron-hole pairs at the interface of a tungsten diselenide / molybdenum diselenide heterostructure. Electronic transport measurements of the interlayer current-voltage characteristics indicate that layer-indirect electron-hole pairs are generated by hot electron impact excitation. Our findings, which demonstrate an efficient energy relaxation pathway that competes with electron thermalization losses, make 2D semiconductor heterostructures viable for a new class of hot-carrier energy harvesting devices that exploit layer-indirect electron-hole excitations. SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Air Force Office of Scientific Research.

  7. Characteristics of hot electron ring in a simple magnetic mirror field

    International Nuclear Information System (INIS)

    Hosokawa, M.; Ikegami, H.

    1980-12-01

    Characteristics of hot electron ring are studied in a simple magnetic mirror machine (mirror ratio 2 : 1) with a diameter of 30 cm at the midplane and with the distance of 80 cm between the mirrors. Maximum microwave input power is 5 kW at 6.4 GHz with the corresponding power density of approximately 0.3 W/cm 3 . With a background cold plasma of 4 x 10 11 cm -3 , hot electron rings are most effectively generated in two cases when the magnetic field on the axis of the midplane is set near the fundamental or the second harmonic electron cyclotron resonance to the applied microwave frequency. Density profile of the hot electrons is observed to take a so-called ring shape with a radius controllable by the magnetic field intensity and with an axial length of approximately 10 cm. The radial cut view of the ring, however, indicates an M shape density profile, and the density of the hot electrons on the axis is about one half of the density at the ring. Approximately 30 msec is needed before generating the hot electron ring at the density of 10 10 cm -3 with an average kinetic energy of 100 keV. The ultimate energy distribution function is observed to have a stepwise cut in the high energy tail and no energetic components above 1 MeV are detected. The hot electron ring is susceptible to a few instabilities which can be artificially triggered. One of the instabilities is observed to associate with a loss of lower energetic electrons and microwave bursts. At the instability, the ring shape is observed to transform into a filled cylinder in a few microseconds and disappear. (author)

  8. Three-dimensional hot electron photovoltaic device with vertically aligned TiO2 nanotubes.

    Science.gov (United States)

    Goddeti, Kalyan C; Lee, Changhwan; Lee, Young Keun; Park, Jeong Young

    2018-05-09

    Titanium dioxide (TiO 2 ) nanotubes with vertically aligned array structures show substantial advantages in solar cells as an electron transport material that offers a large surface area where charges travel linearly along the nanotubes. Integrating this one-dimensional semiconductor material with plasmonic metals to create a three-dimensional plasmonic nanodiode can influence solar energy conversion by utilizing the generated hot electrons. Here, we devised plasmonic Au/TiO 2 and Ag/TiO 2 nanodiode architectures composed of TiO 2 nanotube arrays for enhanced photon absorption, and for the subsequent generation and capture of hot carriers. The photocurrents and incident photon to current conversion efficiencies (IPCE) were obtained as a function of photon energy for hot electron detection. We observed enhanced photocurrents and IPCE using the Ag/TiO 2 nanodiode. The strong plasmonic peaks of the Au and Ag from the IPCE clearly indicate an enhancement of the hot electron flux resulting from the presence of surface plasmons. The calculated electric fields and the corresponding absorbances of the nanodiode using finite-difference time-domain simulation methods are also in good agreement with the experimental results. These results show a unique strategy of combining a hot electron photovoltaic device with a three-dimensional architecture, which has the clear advantages of maximizing light absorption and a metal-semiconductor interface area.

  9. Hot-electron plasma formation and confinement in the tandem mirror experiment-upgrade

    International Nuclear Information System (INIS)

    Ress, D.B.

    1988-06-01

    The tandem mirror experiment-upgrade (TMX-U) at the Lawrence Livermore National Laboratory (LLNL) is the first experiment to investigate the thermal-barrier tandem-mirror concept. One attractive feature of the tandem magnetic mirror as a commercial power reactor is that the fusion reactions occur in an easily accessible center-cell. On the other hand, complicated end-cells are necessary to provide magnetohydrodynamic (MHD) stability and improved particle confinement of the center-cell plasma. In these end-cells, enhanced confinement is achieved with a particular axial potential profile that is formed with electron-cyclotron range-of-frequency heating (ECRF heating, ECRH). By modifying the loss rates of electrons at spatially distinct locations within the end-cells, the ECRH can tailor the plasma potential profile in the desired fashion. Specifically, the thermal-barrier concept requires generation of a population of energetic electrons near the midplane of each end-cell. To be effective, the transverse (to the magnetic field) spatial structure of the hot-electron plasma must be fairly uniform. In this dissertation we characterize the spatial structure of the ECRH-generated plasma, and determine how the structure builds up in time. Furthermore, the plasma should efficiently absorb the ECRF power, and a large fraction of the electrons must be well confined near the end-cell midplane. Therefore, we also examine in detail the ECRH power balance, determining how the ECRF power is absorbed by the plasma, and the processes through which that power is confined and lost. 43 refs., 69 figs., 6 tabs

  10. Buneman instability in hot electron plasma (Te>>Ti)

    International Nuclear Information System (INIS)

    Khalil, S.M.; Sayed, Y.A.; Sayed, R.A.

    1986-07-01

    We shall investigate the linear excitation of electrostatic current Buneman instability in both unmagnetized and magnetized homogeneous plasma. The frequency, growth rate and conditions of excitation of such instability are obtained analytically. We consider that the current velocity u (due to relative streaming of ions and electrons) slightly exceeds the instability threshold velocity u cr and that the electron temperature is much higher than the ion temperature (T e >>T i ). (author)

  11. Limitation and suppression of hot electron fluctuations in submicron semiconductor structures

    International Nuclear Information System (INIS)

    Kochelap, V.A.; Zahleniuk, N.A.; Sokolov, V.N.

    1992-09-01

    We present theoretical investigations of fluctuations of hot electrons in submicron active regions, where the dimensions 2 d of the region is comparable to the electron energy relaxation length L ε . The new physical phenomenon is reported; the fluctuations depend on the sample thickness, with 2d ε a suppression of fluctuations arises in the range of fluctuation frequencies ω much less than T -1 ε , T ε is the electron energy relaxation time. (author). 12 refs, 7 figs

  12. Imaging Plasmon Hybridization of Fano Resonances via Hot-Electron-Mediated Absorption Mapping.

    Science.gov (United States)

    Simoncelli, Sabrina; Li, Yi; Cortés, Emiliano; Maier, Stefan A

    2018-05-04

    The inhibition of radiative losses in dark plasmon modes allows storing electromagnetic energy more efficiently than in far-field excitable bright-plasmon modes. As such, processes benefiting from the enhanced absorption of light in plasmonic materials could also take profit of dark plasmon modes to boost and control nanoscale energy collection, storage, and transfer. We experimentally probe this process by imaging with nanoscale precision the hot-electron driven desorption of thiolated molecules from the surface of gold Fano nanostructures, investigating the effect of wavelength and polarization of the incident light. Spatially resolved absorption maps allow us to show the contribution of each element of the nanoantenna in the hot-electron driven process and their interplay in exciting a dark plasmon mode. Plasmon-mode engineering allows control of nanoscale reactivity and offers a route to further enhance and manipulate hot-electron driven chemical reactions and energy-conversion and transfer at the nanoscale.

  13. Coaxial Ag/ZnO/Ag nanowire for highly sensitive hot-electron photodetection

    Energy Technology Data Exchange (ETDEWEB)

    Zhan, Yaohui; Li, Xiaofeng, E-mail: xfli@suda.edu.cn; Wu, Kai; Wu, Shaolong; Deng, Jiajia [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China)

    2015-02-23

    Single-nanowire photodetectors (SNPDs) are mostly propelled by p-n junctions, where the detection wavelength is constrained by the band-gap width. Here, we present a simple doping-free metal/semiconductor/metal SNPD, which shows strong detection tunability without such a material constraint. The proposed hot-electron SNPD exhibits superior optical and electrical advantages, i.e., optically the coaxial design leads to a strong asymmetrical photoabsorption and results in a high unidirectional photocurrent, as desired by the hot-electron collection; electrically the hot-electrons are generated in the region very close to the barrier, facilitating the electrical transport. Rigorous calculations predict an unbiased photoresponsivity of ∼200 nA/mW.

  14. Numerical simulation of neutral injection in a hot-electron mirror target plasma

    International Nuclear Information System (INIS)

    Werkoff, F.; Bardet, R.; Briand, P.; Dupas, L.; Gormezano, C.; Melin, G.; Association Euratom-CEA, Centre d'Etudes Nucleaires de Grenoble, 38

    1976-01-01

    In the case of neutral injection into a hot-electron target plasma, the use of the existing Fokker-Planck codes is greatly complicated by the fact that the scale of the energies and times of the confined ions and electrons is very large. To avoid this difficulty, a simplified multi-species model is set up, in which each species is described by time-dependent density and energy equations with analytical approximations for the interactions between the species. During the neutral injection, instantaneous high values of the ambipolar potential (higher than the half value of hot-ion energy) may appear, but do not prevent hot-ion density build-up. However, the hot-electron target plasma must not be maintained for a too long time. Numerical runs are performed with typical target parameters: density 2x10 13 cm -3 , electron energy 30 keV, ion energy 400 eV, time duration during which the target density is maintained 1 ms. Hot-ion density, a few 10 14 cm -3 , can be achieved with a neutral beam of 100 A, 20 keV. (author)

  15. High-Current Gain Two-Dimensional MoS 2 -Base Hot-Electron Transistors

    KAUST Repository

    Torres, Carlos M.

    2015-12-09

    The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications. © 2015 American Chemical Society.

  16. Non-equilibrium between ions and electrons inside hot spots from National Ignition Facility experiments

    Directory of Open Access Journals (Sweden)

    Zhengfeng Fan

    2017-01-01

    Full Text Available The non-equilibrium between ions and electrons in the hot spot can relax the ignition conditions in inertial confinement fusion [Fan et al., Phys. Plasmas 23, 010703 (2016], and obvious ion-electron non-equilibrium could be observed by our simulations of high-foot implosions when the ion-electron relaxation is enlarged by a factor of 2. On the other hand, in many shots of high-foot implosions on the National Ignition Facility, the observed X-ray enhancement factors due to ablator mixing into the hot spot are less than unity assuming electrons and ions have the same temperature [Meezan et al., Phys. Plasmas 22, 062703 (2015], which is not self-consistent because it can lead to negative ablator mixing into the hot spot. Actually, this non-consistency implies ion-electron non-equilibrium within the hot spot. From our study, we can infer that ion-electron non-equilibrium exists in high-foot implosions and the ion temperature could be ∼9% larger than the equilibrium temperature in some NIF shots.

  17. High-Current Gain Two-Dimensional MoS 2 -Base Hot-Electron Transistors

    KAUST Repository

    Torres, Carlos M.; Lan, Yann Wen; Zeng, Caifu; Chen, Jyun Hong; Kou, Xufeng; Navabi, Aryan; Tang, Jianshi; Montazeri, Mohammad; Adleman, James R.; Lerner, Mitchell B.; Zhong, Yuan Liang; Li, Lain-Jong; Chen, Chii Dong; Wang, Kang L.

    2015-01-01

    The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications. © 2015 American Chemical Society.

  18. Electrostatic solitons in unmagnetized hot electron-positron-ion plasmas

    International Nuclear Information System (INIS)

    Mahmood, S.; Ur-Rehman, H.

    2009-01-01

    Linear and nonlinear electrostatic waves in unmagnetized electron-positron-ion (e-p-i) plasmas are studied. The electrons and positrons are assumed to be isothermal and dynamic while ions are considered to be stationary to neutralize the plasma background only. It is found that both upper (fast) and lower (slow) Langmuir waves can propagates in such a type of pair (e-p) plasma in the presence of ions. The small amplitude electrostatic Korteweg-de Vries (KdV) solitons are also obtained using reductive perturbation method. The electrostatic potential hump structures are found to exist when the temperature of the electrons is larger than the positrons, while the electrostatic potential dips are obtained in the reverse temperature conditions for electrons and positrons in e-p-i plasmas. The numerical results are also shown for illustration. The effects of different ion concentration and temperature ratios of electrons and positrons, on the formation of nonlinear electrostatic potential structures in e-p-i plasmas are also discussed.

  19. Hard x-ray measurements of the hot-electron rings in EBT-S

    International Nuclear Information System (INIS)

    Hillis, D.L.

    1982-06-01

    A thorough understanding of the hot electron rings in ELMO Bumpy Torus-Scale (EBT-S) is essential to the bumpy torus concept of plasma production, since the rings provide bulk plasma stability. The hot electrons are produced via electron cyclotron resonant heating using a 28-GHz cw gyrotron, which has operated up to power levels of 200 kW. The parameters of the energetic electron rings are studied via hard x-ray measurement techniques and with diamagnetic pickup coils. The hard x-ray measurements have used collimated NaI(Tl) detectors to determine the electron temperature T/sub e/ and electron density n/sub e/ for the hot electron annulus. Typical values of T/sub e/ are 400 to 500 keV and of n/sub e/ 2 to 5 x 10 11 cm -3 . The total stored energy of a single energetic electron ring as measured by diamagnetic pickup loops approaches approx. 40 J and is in good agreement with that deduced from hard x-ray measurements. By combining the experimental measurements from hard x-rays and the diamagnetic loops, an estimate can be obtained for the volume of a single hot electron ring. The ring volume is determined to be approx. 2.2 litres, and this volume remains approximately constant over the T-mode operating regime. Finally, the power in the electrons scattered out of the ring is measured indirectly by measuring the x-ray radiation produced when those electrons strike the chamber walls. The variation of this radiation with increasing microwave power levels is found to be consistent with classical scattering estimates

  20. Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Gregory Elijah [The Ohio State Univ., Columbus, OH (United States)

    2013-01-01

    Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic

  1. Effect of re-heating on the hot electron temperature

    International Nuclear Information System (INIS)

    Estabrook, K.; Rosen, M.

    1980-01-01

    Resonant absorption is the direct conversion of the transverse laser light to longitudinal electron plasma waves (epw) at the critical density [10 21 (1.06 μm/lambda 0 ) 2 cm -3 ]. The oscillating longitudinal electric field of the epw heats the electrons by accelerating them down the density gradient to a temperature of approximately 21T/sub e/ 0 25 ([I(W/cm 2 )/10 16 ](lambda 0 /1.06 μm) 2 ) 0 4 . This section extends the previous work by studying the effects of magnetic fields and collisions (albedo) which return the heated electrons for further heating. A magnetic field increases their temperature and collisions do not

  2. Naked Gold Nanoparticles and hot Electrons in Water.

    Science.gov (United States)

    Ghandi, Khashayar; Wang, Furong; Landry, Cody; Mostafavi, Mehran

    2018-05-08

    The ionizing radiation in aqueous solutions of gold nanoparticles, stabilized by electrostatic non-covalent intermolecular forces and steric interactions, with antimicrobial compounds, are investigated with picosecond pulse radiolysis techniques. Upon pulse radiolysis of an aqueous solution containing very low concentrations of gold nanoparticles with naked surfaces available in water (not obstructed by chemical bonds), a change to Cerenkov spectrum over a large range of wavelengths are observed and pre-solvated electrons are captured by gold nanoparticles exclusively (not by ionic liquid surfactants used to stabilize the nanoparticles). The solvated electrons are also found to decay rapidly compared with the decay kinetics in water. These very fast reactions with electrons in water could provide an enhanced oxidizing zone around gold nanoparticles and this could be the reason for radio sensitizing behavior of gold nanoparticles in radiation therapy.

  3. Towards hot electron mediated charge exchange in hyperthermal energy ion-surface interactions

    DEFF Research Database (Denmark)

    Ray, M. P.; Lake, R. E.; Thomsen, Lasse Bjørchmar

    2010-01-01

    shows that the primary energy loss mechanism is the atomic displacement of Au atoms in the thin film of the metal–oxide–semiconductor device. We propose that neutral particle detection of the scattered flux from a biased device could be a route to hot electron mediated charge exchange.......We have made Na + and He + ions incident on the surface of solid state tunnel junctions and measured the energy loss due to atomic displacement and electronic excitations. Each tunnel junction consists of an ultrathin film metal–oxide–semiconductor device which can be biased to create a band of hot...

  4. Origin of Power Laws for Reactions at Metal Surfaces Mediated by Hot Electrons

    DEFF Research Database (Denmark)

    Olsen, Thomas; Schiøtz, Jakob

    2009-01-01

    A wide range of experiments have established that certain chemical reactions at metal surfaces can be driven by multiple hot-electron-mediated excitations of adsorbates. A high transient density of hot electrons is obtained by means of femtosecond laser pulses and a characteristic feature of such...... density functional theory and the delta self-consistent field method. With a simplifying assumption, the power law becomes exact and we obtain a simple physical interpretation of the exponent n, which represents the number of adsorbate vibrational states participating in the reaction....

  5. Quasi-static electron density fluctuations of atoms in hot compressed matter

    International Nuclear Information System (INIS)

    Grimaldi, F.; Grimaldi-Lecourt, A.

    1982-01-01

    The standard theoretical methods for the calculation of properties of hot compressed matter lead to a description based on the Average Atom model. In this model the degenerate orbitals are populated with the Fermi-Dirac (FD) density, partitioned according to the binomial distribution. Since the one particle picture is inadequate to evaluate reliable optical properties, a method involving correlated population fluctuations, but limited to unrelaxed orbitals and lacking time dependence, has been examined. The probability distribution of fluctuations in a particular level is evaluated through a decoupling procedure. The method is carried out self consistently. For each level this leads to the definition of an effective 1st order ionization energy as a statistical sum of all possible transition energies. As a result the effective number of electrons exchanged with the outside weights the chemical potential. This defines an effective chemical potential μsup(k) for each level. In many cases of interest the statistics leads to FD type average occupation numbers. This allows a treatment of the continuum in a Thomas-Fermi like model using the effective ionization energy and μsup(k). We obtain a simultaneous description of charge rearrangements and net fluctuations in the Wigner-Seitz cell. The discussion is supported by numerical results for iron. (author)

  6. Hot electrons in superlattices: quantum transport versus Boltzmann equation

    DEFF Research Database (Denmark)

    Wacker, Andreas; Jauho, Antti-Pekka; Rott, S.

    1999-01-01

    A self-consistent solution of the transport equation is presented for semiconductor superlattices within different approaches: (i) a full quantum transport model based on nonequilibrium Green functions, (ii) the semiclassical Boltzmann equation for electrons in a miniband, and (iii) Boltzmann...

  7. New electron beam facility for irradiated plasma facing materials testing in hot cell

    International Nuclear Information System (INIS)

    Sakamoto, N.; Kawamura, H.; Akiba, M.

    1995-01-01

    Since plasma facing components such as the first wall and the divertor for the next step fusion reactors are exposed to high heat loads and high energy neutron flux generated by the plasma, it is urgent to develop of plasma facing components which can resist these. Then, we have established electron beam heat facility (open-quotes OHBISclose quotes, Oarai Hot-cell electron Beam Irradiating System) at a hot cell in JMTR (Japan Materials Testing Reactor) hot laboratory in order to estimate thermal shock resistivity of plasma facing materials and heat removal capabilities of divertor elements under steady state heating. In this facility, irradiated plasma facing materials (beryllium, carbon based materials and so on) and divertor elements can be treated. This facility consists of an electron beam unit with the maximum beam power of 50kW and the vacuum vessel. The acceleration voltage and the maximum beam current are 30kV (constant) and 1.7A, respectively. The loading time of electron beam is more than 0.1ms. The shape of vacuum vessel is cylindrical, and the mainly dimensions are 500mm in inner diameter, 1000mm in height. The ultimate vacuum of this vessel is 1 x 10 -4 Pa. At present, the facility for thermal shock test has been established in a hot cell. And performance estimation on the electron beam is being conducted. Presently, the devices for heat loading tests under steady state will be added to this facility

  8. Generation and Beaming of Early Hot Electrons onto the Capsule in Laser-Driven Ignition Hohlraums

    Science.gov (United States)

    Dewald, E. L.; Hartemann, F.; Michel, P.; Milovich, J.; Hohenberger, M.; Pak, A.; Landen, O. L.; Divol, L.; Robey, H. F.; Hurricane, O. A.; Döppner, T.; Albert, F.; Bachmann, B.; Meezan, N. B.; MacKinnon, A. J.; Callahan, D.; Edwards, M. J.

    2016-02-01

    In hohlraums for inertial confinement fusion (ICF) implosions on the National Ignition Facility, suprathermal hot electrons, generated by laser plasma instabilities early in the laser pulse ("picket") while blowing down the laser entrance hole (LEH) windows, can preheat the capsule fuel. Hard x-ray imaging of a Bi capsule surrogate and of the hohlraum emissions, in conjunction with the measurement of time-resolved bremsstrahlung spectra, allows us to uncover for the first time the directionality of these hot electrons and infer the capsule preheat. Data and Monte Carlo calculations indicate that for most experiments the hot electrons are emitted nearly isotropically from the LEH. However, we have found cases where a significant fraction of the generated electrons are emitted in a collimated beam directly towards the capsule poles, where their local energy deposition is up to 10 × higher than the average preheat value and acceptable levels for ICF implosions. The observed "beaming" is consistent with a recently unveiled multibeam stimulated Raman scattering model [P. Michel et al., Phys. Rev. Lett. 115, 055003 (2015)], where laser beams in a cone drive a common plasma wave on axis. Finally, we demonstrate that we can control the amount of generated hot electrons by changing the laser pulse shape and hohlraum plasma.

  9. New electron beam facility for irradiated plasma facing materials testing in hot cell

    International Nuclear Information System (INIS)

    Shimakawa, S.; Akiba, M.; Kawamura, H.

    1996-01-01

    Since plasma facing components such as the first wall and the divertor for the next step fusion reactors are exposed to high heat loads and high energy neutron flux generated by the plasma, it is urgent to develop plasma facing components which can resist these. We have established electron beam heat facility ('OHBIS', Oarai hot-cell electron beam irradiating system) at a hot cell in JMTR (Japan materials testing reactor) hot laboratory in order to estimate thermal shock resistivity of plasma facing materials and heat removal capabilities of divertor elements under steady state heating. In this facility, irradiated plasma facing materials (beryllium, carbon based materials and so on) and divertor elements can be treated. This facility consists of an electron beam unit with the maximum beam power of 50 kW and the vacuum vessel. The acceleration voltage and the maximum beam current are 30 kV (constant) and 1.7 A, respectively. The loading time of the electron beam is more than 0.1 ms. The shape of vacuum vessel is cylindrical, and the main dimensions are 500 mm in inside diameter, 1000 mm in height. The ultimate vacuum of this vessel is 1 x 10 -4 Pa. At present, the facility for the thermal shock test has been established in a hot cell. The performance of the electron beam is being evaluated at this time. In the future, the equipment for conducting static heat loadings will be incorporated into the facility. (orig.)

  10. Hot-electron-plasma accumulation in the CIRCE mirror experiment

    International Nuclear Information System (INIS)

    Bardet, R.; Briand, P.; Dupas, L.; Gormezano, C.; Melin, G.

    1975-01-01

    In the CIRCE experiment, the plasma is obtained by the trapping of a plasma injected into a magnetic bottle by electron heating at cyclotron resonance. The plasma density lies between 5x10 11 cm -3 and 10 12 cm -3 , the electron temperature is about 100 keV and the ion temperature is in the range of few hundred electronvolts. Gross instabilities are not observed. The ratio of the plasma density to the neutral-gas density inside the plasma is higher than 100. A few kilowatts of r.f. power at 8 GHz are sufficient to obtain these results, a fact which looks encouraging as far as the creation of a more effective fast-neutral-target plasma using the CIRCE-experiment concept is concerned. (author)

  11. Hot Electron Photoemission from Plasmonic Nanostructures: The Role of Surface Photoemission and Transition Absorption

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Zhukovsky, Sergei; Ikhsanov, Renat Sh

    2015-01-01

    We study mechanisms of photoemission of hot electrons from plasmonic nanoparticles. We analyze the contribution of "transition absorption", i.e., loss of energy of electrons passing through the boundary between different materials, to the surface mechanism of photoemission. We calculate photoemis......We study mechanisms of photoemission of hot electrons from plasmonic nanoparticles. We analyze the contribution of "transition absorption", i.e., loss of energy of electrons passing through the boundary between different materials, to the surface mechanism of photoemission. We calculate...... photoemission rate and transition absorption for nanoparticles surrounded by various media with a broad range of permittivities and show that photoemission rate and transition absorption follow the same dependence on the permittivity. Thus, we conclude that transition absorption is responsible...

  12. Analysis of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applications

    Science.gov (United States)

    Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.

    1996-01-01

    The prospects of a YBa2Cu3O7(delta)(YBCO) hot-electron bolometer (HEB) mixer for a THz heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate.

  13. Operation of a novel hot-electron vertical-cavity surface-emitting laser

    Science.gov (United States)

    Balkan, Naci; O'Brien-Davies, Angela; Thoms, A. B.; Potter, Richard J.; Poolton, Nigel; Adams, Michael J.; Masum, J.; Bek, Alpan; Serpenguzel, Ali; Aydinli, Atilla; Roberts, John S.

    1998-07-01

    The hot Electron Light Emission and Lasing in Semiconductor Heterostructures devices (HELLISH-1) is novel surface emitter consisting of a GaAs quantum well, within the depletion region, on the n side of Ga1-xAlxAs p- n junction. It utilizes hot electron transport parallel to the layers and injection of hot electron hole pairs into the quantum well through a combination of mechanisms including tunnelling, thermionic emission and diffusion of `lucky' carriers. Super Radiant HELLISH-1 is an advanced structure incorporating a lower distributed Bragg reflector (DBR). Combined with the finite reflectivity of the upper semiconductor-air interface reflectivity it defines a quasi- resonant cavity enabling emission output from the top surface with a higher spectral purity. The output power has increased by two orders of magnitude and reduced the full width at half maximum (FWHM) to 20 nm. An upper DBR added to the structure defines HELLISH-VCSEL which is currently the first operational hot electron surface emitting laser and lases at room temperature with a 1.5 nm FWHM. In this work we demonstrate and compare the operation of UB-HELLISH-1 and HELLISH-VCSEL using experimental and theoretical reflectivity spectra over an extensive temperature range.

  14. Study of Hot-Electron Effects, Breakdown and Reliability in FETS, HEMTS, and HBT’S

    Science.gov (United States)

    1998-08-01

    device (VDS = 7.5 V, VQS = -0.1 V, 137 hrs). (b) Drain Current FT-DLTS measurements in an as received device (open simbols ) and in a device after hot...electron stress test: VDS = 7.5 V, VQS = - 0.1 V, 137 hrs (closed simbols ). output characteristics of degraded devices and completely eliminates

  15. Localized structures of electromagnetic waves in hot electron-positron plasma

    International Nuclear Information System (INIS)

    Kartal, S.; Tsintsadze, L.N.; Berezhiani, V.I.

    1995-08-01

    The dynamics of relatively strong electromagnetic (EM) wave propagation in hot electron-positron plasma is investigated. The possibility of finding localized stationary structures of EM waves is explored. It it shown that under certain conditions the EM wave forms a stable localized soliton-like structures where plasma is completely expelled from the region of EM field location. (author). 9 refs, 2 figs

  16. Hot-electrons-induced ultrafast demagnitization in Co/Pt multilayers

    NARCIS (Netherlands)

    Bergeard, N.; Hehn, M.; Mangin, S.; Lengaigne, G.; Montaigne, F.; Lalieu, M. L. M.; Koopmans, B.; Malinowski, G.

    2016-01-01

    Using specially engineered structures to tailor the optical absorption in a metallic multilayer, we analyze the magnetization dynamics of a Co/Pt multilayer buried below a thick Cu layer. We demonstrate that hot electrons alone can very efficiently induce ultrafast demagnetization. Simulations based

  17. Broadband Cooling Spectra of Hot Electrons and Holes in PbSe Quantum Dots

    NARCIS (Netherlands)

    Spoor, F.C.M.; Tomić, Stanko; Houtepen, A.J.; Siebbeles, L.D.A.

    2017-01-01

    Understanding cooling of hot charge carriers in semiconductor quantum dots (QDs) is of fundamental interest and useful to enhance the performance of QDs in photovoltaics. We study electron and hole cooling dynamics in PbSe QDs up to high energies where carrier multiplication occurs. We

  18. Penetration length-dependent hot electrons in the field emission from ZnO nanowires

    Science.gov (United States)

    Chen, Yicong; Song, Xiaomeng; Li, Zhibing; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

    2018-01-01

    In the framework of field emission, whether or not hot electrons can form in the semiconductor emitters under a surface penetration field is of great concern, which will provide not only a comprehensive physical picture of field emission from semiconductor but also guidance on how to improve device performance. However, apart from some theoretical work, its experimental evidence has not been reported yet. In this article, the field penetration length-dependent hot electrons were observed in the field emission of ZnO nanowires through the in-situ study of its electrical and field emission characteristic before and after NH3 plasma treatment in an ultrahigh vacuum system. After the treatment, most of the nanowires have an increased carrier density but reduced field emission current. The raised carrier density was caused by the increased content of oxygen vacancies, while the degraded field emission current was attributed to the lower kinetic energy of hot electrons caused by the shorter penetration length. All of these results suggest that the field emission properties of ZnO nanowires can be optimized by modifying their carrier density to balance both the kinetic energy of field induced hot electrons and the limitation of saturated current under a given field.

  19. Model for ion confinement in a hot-electron tandem mirror anchor

    International Nuclear Information System (INIS)

    Baldwin, D.E.

    1980-01-01

    Anisotropic, hot electrons trapped in local minimum-B wells have been proposed as MHD-stabilizing anchors to an otherwise axisymmetric tandem configuration. This work describes a model for plasma confinement between the anchors and the remainder of the system and calcuates the power loss implied by maintenance of this plasma

  20. Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect

    Energy Technology Data Exchange (ETDEWEB)

    Nuga, H., E-mail: nuga@p-grp.nucleng.kyoto-u.ac.jp; Fukuyama, A. [Department of Engineering, Kyoto University, Kyoto 615-8540 (Japan); Yagi, M. [National Institutes for Quantum and Radiological Science and Technology, Aomori 039-3212 (Japan)

    2016-06-15

    To study runaway electron generation in disruptions, we have extended the three-dimensional (two-dimensional in momentum space; one-dimensional in the radial direction) Fokker-Planck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a self-consistent manner. A particular focus is placed on the hot-tail effect in two-dimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electron-electron slowing down time for a few times of the pre-quench thermal velocity. It contributes to not only the enhancement of the primary runaway electron generation but also the broadening of the runaway electron distribution in the pitch angle direction. If the thermal energy loss during the major disruption is assumed to be isotropic, there are hot-tail electrons that have sufficiently large perpendicular momentum, and the runaway electron distribution becomes broader in the pitch angle direction. In addition, the pitch angle scattering also yields the broadening. Since the electric field is reduced due to the burst of runaway electron generation, the time required for accelerating electrons to the runaway region becomes longer. The longer acceleration period makes the pitch-angle scattering more effective.

  1. Target Surface Area Effects on Hot Electron Dynamics from High Intensity Laser-Plasma Interactions

    Science.gov (United States)

    2016-08-19

    Science, University ofMichigan, AnnArbor,MI 48109-2099, USA E-mail: czulick@umich.edu Keywords: laser- plasma ,mass-limited, fast electrons , sheath...New J. Phys. 18 (2016) 063020 doi:10.1088/1367-2630/18/6/063020 PAPER Target surface area effects on hot electron dynamics from high intensity laser... plasma interactions CZulick, ARaymond,AMcKelvey, VChvykov, AMaksimchuk, AGRThomas, LWillingale, VYanovsky andKKrushelnick Center forUltrafast Optical

  2. Terahertz detectors using hot-electrons in superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Semenov, A. [DLR, Inst. of Planetary Research, Berlin (Germany)

    2007-07-01

    Recently the terahertz gap has been recognized as a prospective spectral range for radioastronomy as well as for material and security studies. Implementation of terahertz technology in these fields requires further improvement of instruments and their major subcomponents. Physical phenomena associated with the local and homogeneous non-equilibrium electron sates in thin superconducting films offer numerous possibilities for the development of terahertz and infrared detectors. Depending on the nature of the resistive state and the operation regime, a variety of detector can be realized. They are e.g. direct bolometric or kinetic inductance detectors, heterodyne mixers or photon counters. Operation principles and physical limitations of these devices will be discussed. Two examples of the detector development made in cooperation between the German Aerospace Center, the University of Karlsruhe and PTB, Berlin will be presented. The energy resolving single-photon detector with an almost fundamentally limited energy resolution of 0.6 eV at 6.5 K for photons with wavelengths from 400 nm to 2500 nm and the heterodyne mixer quasioptically coupled to radiation in the frequency range from 0.8 THz to 5 THz and providing a noise temperature of less then ten times the quantum limit. The mixers will be implemented in the terahertz radar for security screening (TERASEC) and in the heterodyne receiver of the stratospheric observatory SOFIA. (orig.)

  3. Plasmonic photocatalytic reactions enhanced by hot electrons in a one-dimensional quantum well

    Directory of Open Access Journals (Sweden)

    H. J. Huang

    2015-11-01

    Full Text Available The plasmonic endothermic oxidation of ammonium ions in a spinning disk reactor resulted in light energy transformation through quantum hot charge carriers (QHC, or quantum hot electrons, during a chemical reaction. It is demonstrated with a simple model that light of various intensities enhance the chemical oxidization of ammonium ions in water. It was further observed that light illumination, which induces the formation of plasmons on a platinum (Pt thin film, provided higher processing efficiency compared with the reaction on a bare glass disk. These induced plasmons generate quantum hot electrons with increasing momentum and energy in the one-dimensional quantum well of a Pt thin film. The energy carried by the quantum hot electrons provided the energy needed to catalyze the chemical reaction. The results indicate that one-dimensional confinement in spherical coordinates (i.e., nanoparticles is not necessary to provide an extra excited state for QHC generation; an 8 nm Pt thin film for one-dimensional confinement in Cartesian coordinates can also provide the extra excited state for the generation of QHC.

  4. Experimental study on energy distribution of the hot electrons generated by femtosecond laser interacting with solid targets

    International Nuclear Information System (INIS)

    Gu Yuqiu; Zheng Zhijian; Zhou Weimin; Wen Tianshu; Chunyu Shutai; Cai Dafeng; Sichuan Univ., Chengdu; Neijiang Teachers College, Neijiang; Jiao Chunye; Chen Hao; Sichuan Univ., Chengdu; Yang Xiangdong

    2005-01-01

    This paper reports the results of the experiment of hot electron energy distribution during the femtosecond laser-solid target interaction. The hot electrons formed an anisotropic energy distribution. In the direction of the target normal, the energy spectrum of the hot electron was a Maxwellian-like distribution with an effective temperature of 206 keV, which was due to the resonance absorption. In the direction of the specular reflection of laser, there appeared a local plateau of hot electron energy spectrum at the beginning and then it was decreased gradually, which maybe produced by several acceleration mechanisms. The effective temperature and the yield of hot electrons in the direction of the target normal is larger than those in the direction of the specular reflection of laser, which proves that the resonance absorption mechanism is more effective than others. (authors)

  5. Hot electron dynamics at semiconductor surfaces: Implications for quantum dot photovoltaics

    Science.gov (United States)

    Tisdale, William A., III

    Finding a viable supply of clean, renewable energy is one of the most daunting challenges facing the world today. Solar cells have had limited impact in meeting this challenge because of their high cost and low power conversion efficiencies. Semiconductor nanocrystals, or quantum dots, are promising materials for use in novel solar cells because they can be processed with potentially inexpensive solution-based techniques and because they are predicted to have novel optoelectronic properties that could enable the realization of ultra-efficient solar power converters. However, there is a lack of fundamental understanding regarding the behavior of highly-excited, or "hot," charge carriers near quantum-dot and semiconductor interfaces, which is of paramount importance to the rational design of high-efficiency devices. The elucidation of these ultrafast hot electron dynamics is the central aim of this Dissertation. I present a theoretical framework for treating the electronic interactions between quantum dots and bulk semiconductor surfaces and propose a novel experimental technique, time-resolved surface second harmonic generation (TR-SHG), for probing these interactions. I then describe a series of experimental investigations into hot electron dynamics in specific quantum-dot/semiconductor systems. A two-photon photoelectron spectroscopy (2PPE) study of the technologically-relevant ZnO(1010) surface reveals ultrafast (sub-30fs) cooling of hot electrons in the bulk conduction band, which is due to strong electron-phonon coupling in this highly polar material. The presence of a continuum of defect states near the conduction band edge results in Fermi-level pinning and upward (n-type) band-bending at the (1010) surface and provides an alternate route for electronic relaxation. In monolayer films of colloidal PbSe quantum dots, chemical treatment with either hydrazine or 1,2-ethanedithiol results in strong and tunable electronic coupling between neighboring quantum dots

  6. Electric field dependence of the temperature and drift velocity of hot electrons in n-Si

    International Nuclear Information System (INIS)

    Vass, E.

    2001-01-01

    Full text: The average energy- and momentum loss rates of hot electrons interacting simultaneously with acoustic phonons, ionized and neutral impurities in n-Si are calculated quantum theoretically by means of a drifted hot Fermi-Dirac distribution. The drift velocity vd and electron temperature Te occurring in this distribution are determined self-consistently from the force- and power balance equation with respect to the charge neutrality condition. The functions Te(E) and vd(E) calculated in this way are compared with the corresponding relations obtained with help of the simple electron temperature model in order to determine the range of application of this model often used in previous treatises. (author)

  7. Numerical study of the generation of runaway electrons in a gas diode with a hot channel

    Energy Technology Data Exchange (ETDEWEB)

    Lisenkov, V. V., E-mail: lisenkov@iep.uran.ru [Institute of Electrophysics UrB RAS, 106 Amundsena St., Ekaterinburg 620012 (Russian Federation); Ural Federal University, 19 Mira St., Ekaterinburg 620002 (Russian Federation); Shklyaev, V. A., E-mail: shklyaev@to.hcei.tsc.ru [Institute of High Current Electronics SD RAS, 2/3 Akademichesky Avenue, 634055 Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk (Russian Federation)

    2015-11-15

    A new method for increasing the efficiency of runaway electron beam generation in atmospheric pressure gas media has been suggested and theoretically proved. The method consists of creating a hot region (e.g., a spark channel or a laser plume) with a decreased numerical density of gas molecules (N) near the cathode. In this method, the ratio E/N (E—electric field strength) is increased by decreasing N instead of increasing E, as has been done in the past. The numerical model that is used allows the simultaneous calculation of the formation of a subnanosecond gas discharge and the generation of runaway electrons in gas media. The calculations have demonstrated the possibility of obtaining current pulses of runaway electrons with amplitudes of hundred of amperes and durations of more than 100 ps. The influence of the hot channel geometry on the parameters of the generated beam has been investigated.

  8. Study by electronic microscopy of corrosion features of graphite after hot oxidation (air, 620 C)

    International Nuclear Information System (INIS)

    Jodon de Villeroche, Suzanne

    1968-01-01

    The author reports the study of corrosion features of graphite after hot oxidation in the air at 620 C. It is based on observations made by electronic microscopy. This study comes after another one dedicated to oxidation features obtained by hot corrosion of natural graphite, and aims at comparing pyrolytic graphite before and after irradiation in an atomic pile, and at performing tests on a graphite processed with ozone. After a recall of generalities about natural graphite and of some issues related to hot corrosion of natural graphite, the author presents some characteristics and features of irradiated and non-irradiated pyrolytic graphite. He reports the study of the oxidation of samples of pyrolytic graphite: production of thin lamellae, production of glaze-carbon replicates, oxidation of irradiated and of non-irradiated graphite, healing of irradiation defects, and oxidation of ozone-processed natural graphite [fr

  9. Non-equilibrium between ions and electrons inside hot spots from National Ignition Facility experiments

    OpenAIRE

    Zhengfeng Fan; Yuanyuan Liu; Bin Liu; Chengxin Yu; Ke Lan; Jie Liu

    2017-01-01

    The non-equilibrium between ions and electrons in the hot spot can relax the ignition conditions in inertial confinement fusion [Fan et al., Phys. Plasmas 23, 010703 (2016)], and obvious ion-electron non-equilibrium could be observed by our simulations of high-foot implosions when the ion-electron relaxation is enlarged by a factor of 2. On the other hand, in many shots of high-foot implosions on the National Ignition Facility, the observed X-ray enhancement factors due to ablator mixing into...

  10. Gap-plasmon based broadband absorbers for enhanced hot-electron and photocurrent generation

    DEFF Research Database (Denmark)

    Lu, Yuhua; Dong, Wen; Chen, Zhuo

    2016-01-01

    Plasmonic hot-electron generation has recently come into focus as a new scheme for solar energy conversion. So far, however, due to the relatively narrow bandwidth of the surface plasmon resonances and the insufficient resonant light absorption, most of plasmonic photocatalysts show narrow......-band spectral responsivities and small solar energy conversion efficiencies. Here we experimentally demonstrate that a three-layered nanostructure, consisting of a monolayer gold-nanoparticles and a gold film separated by a TiO2 gap layer (Au-NPs/TiO2/Au-film), is capable of near-completely absorbing light...... within the whole visible region. We show that the Au-NPs/TiO2/Au-film device can take advantage of such strong and broadband light absorption to enhance the generation of hot electrons and thus the photocurrent under visible irradiation. As compared to conventional plasmonic photocatalysts such as Au...

  11. Interpretation of the electron cyclotron emission of hot ASDEX upgrade plasmas at optically thin frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Denk, Severin Sebastian; Stroth, Ulrich [Max-Planck-Institut fuer Plasmaphysik, D-85748 Garching (Germany); Physik-Department E28, Technische Universitaet Muenchen, 85748 Garching (Germany); Fischer, Rainer; Poli, Emanuele; Willensdorfer, Matthias; Maj, Omar; Stober, Joerg; Suttrop, Wolfgang [Max-Planck-Institut fuer Plasmaphysik, D-85748 Garching (Germany); Collaboration: The ASDEX Upgrade Team

    2016-07-01

    The electron cyclotron emission diagnostic (ECE) provides routinely electron temperature (T{sub e}) measurements. ''Kinetic effects'' (relativistic mass shift and Doppler shift) can cause the measured radiation temperatures (T{sub rad}) to differ from T{sub e} at cold resonance position complicating the determination of T{sub e} from the measured radiation temperature profile (T{sub rad}). For the interpretation of such ECE measurements an electron cyclotron forward model solving the radiation transport equation for given T{sub e} and electron density profiles is in use in the framework of Integrated Data Analysis at ASDEX Upgrade. While the original model lead to improved T{sub e} profiles near the plasma edge in moderately hot H-mode discharges, vacuum approximations in the model lead to inaccuracies given large T{sub e}. In hot plasmas ''wave-plasma interaction'', i.e. the dielectric effect of the background plasma onto the electron cyclotron emission, becomes important at optical thin measured frequencies. Additionally, given moderate electron densities and large T{sub e}, the refraction of the line of sight has to be considered for the interpretation of ECE measurements with low optical depth.

  12. Numerical method for the dispersion relation of a hot and inhomogeneous plasma with an electron beam

    International Nuclear Information System (INIS)

    Devia, A.; Orrego, C.E.; Buitrago, G.

    1990-01-01

    A numerical method that is based in kinetic theory (Vlasov-Poison equations) was developed in order to calculate the dispersion relation for the interaction between a hot cylindrical and electron beam in any temperature and density. The plasma-beam system is located in a strong magnetic field. Many examples showing the effect of the temperatures and densities on the dispersion relation are given. (Author)

  13. Study of nonlinear electron-acoustic solitary and shock waves in a dissipative, nonplanar space plasma with superthermal hot electrons

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jiu-Ning, E-mail: hanjiuning@126.com; He, Yong-Lin; Luo, Jun-Hua; Nan, Ya-Gong; Han, Zhen-Hai; Dong, Guang-Xing [College of Physics and Electromechanical Engineering, Hexi University, Zhangye 734000 (China); Duan, Wen-Shan [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Li, Jun-Xiu [College of Civil Engineering, Hexi University, Zhangye 734000 (China)

    2014-01-15

    With the consideration of the superthermal electron distribution, we present a theoretical investigation about the nonlinear propagation of electron-acoustic solitary and shock waves in a dissipative, nonplanar non-Maxwellian plasma comprised of cold electrons, superthermal hot electrons, and stationary ions. The reductive perturbation technique is used to obtain a modified Korteweg-de Vries Burgers equation for nonlinear waves in this plasma. We discuss the effects of various plasma parameters on the time evolution of nonplanar solitary waves, the profile of shock waves, and the nonlinear structure induced by the collision between planar solitary waves. It is found that these parameters have significant effects on the properties of nonlinear waves and collision-induced nonlinear structure.

  14. Electron - polar acoustical phonon interactions in nitride based diluted magnetic semiconductor quantum well via hot electron magnetotransport

    International Nuclear Information System (INIS)

    Pandya, Ankur; Shinde, Satyam; Jha, Prafulla K.

    2015-01-01

    In this paper the hot electron transport properties like carrier energy and momentum scattering rates and electron energy loss rates are calculated via interactions of electrons with polar acoustical phonons for Mn doped BN quantum well in BN nanosheets via piezoelectric scattering and deformation potential mechanisms at low temperatures with high electric field. Electron energy loss rate increases with the electric field. It is observed that at low temperatures and for low electric field the phonon absorption is taking place whereas, for sufficient large electric field, phonon emission takes place. Under the piezoelectric (polar acoustical phonon) scattering mechanism, the carrier scattering rate decreases with the reduction of electric field at low temperatures wherein, the scattering rate variation with electric field is limited by a specific temperature beyond which there is no any impact of electric field on such scattering

  15. Electrogenerated chemiluminescence induced by sequential hot electron and hole injection into aqueous electrolyte solution

    Energy Technology Data Exchange (ETDEWEB)

    Salminen, Kalle; Kuosmanen, Päivi; Pusa, Matti [Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Kulmala, Oskari [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 (Finland); Håkansson, Markus [Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Kulmala, Sakari, E-mail: sakari.kulmala@aalto.fi [Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland)

    2016-03-17

    Hole injection into aqueous electrolyte solution is proposed to occur when oxide-coated aluminum electrode is anodically pulse-polarized by a voltage pulse train containing sufficiently high-voltage anodic pulses. The effects of anodic pulses are studied by using an aromatic Tb(III) chelate as a probe known to produce intensive hot electron-induced electrochemiluminescence (HECL) with plain cathodic pulses and preoxidized electrodes. The presently studied system allows injection of hot electrons and holes successively into aqueous electrolyte solutions and can be utilized in detecting electrochemiluminescent labels in fully aqueous solutions, and actually, the system is suggested to be quite close to a pulse radiolysis system providing hydrated electrons and hydroxyl radicals as the primary radicals in aqueous solution without the problems and hazards of ionizing radiation. The analytical power of the present excitation waveforms are that they allow detection of electrochemiluminescent labels at very low detection limits in bioaffinity assays such as in immunoassays or DNA probe assays. The two important properties of the present waveforms are: (i) they provide in situ oxidation of the electrode surface resulting in the desired oxide film thickness and (ii) they can provide one-electron oxidants for the system by hole injection either via F- and F{sup +}-center band of the oxide or by direct hole injection to valence band of water at highly anodic pulse amplitudes. - Highlights: • Hot electrons injected into aqueous electrolyte solution. • Generation of hydrated electrons. • Hole injection into aqueous electrolyte solution. • Generation of hydroxyl radicals.

  16. Experimental studies on the production and suppression mechanism of the hot electrons produced by short wavelength laser

    International Nuclear Information System (INIS)

    Qi Lanying; Jiang Xiaohua; Zhao Xuewei; Li Sanwei; Zhang Wenhai; Li Chaoguang; Zheng Zhijian; Ding Yongkun

    1999-12-01

    The experiments on gold-disk and hohlraum and plastic hydrocarbon (CH) film targets irradiated by laser beams with wavelength 0.35 μm (Xingguang-II) and 0.53 μm (Shenguang-I) are performed. The characteristics of hot electrons are commonly deduced from spectrum of hard X-ray. Associated with the measurement of backward SRS and 3/2ω 0 , the production mechanism of hot electrons for different target type is analyzed in laser plasma with shorter wavelength. A effective way to suppress hot electrons has been found

  17. Hot electron transport modelling in fast ignition relevant targets with non-Spitzer resistivity

    Energy Technology Data Exchange (ETDEWEB)

    Chapman, D A; Hoarty, D J; Swatton, D J R [Plasma Physics Department, AWE, Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom); Hughes, S J, E-mail: david.chapman@awe.co.u [Computational Physics Group, AWE, Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom)

    2010-08-01

    The simple Lee-More model for electrical resistivity is implemented in the hybrid fast electron transport code THOR. The model is shown to reproduce experimental data across a wide range of temperatures using a small number of parameters. The effect of this model on the heating of simple Al targets by a short-pulse laser is studied and compared to the predictions of the classical Spitzer-Haerm resistivity. The model is then used in simulations of hot electron transport experiments using buried layer targets.

  18. Capture dynamics of hot electrons on quantum dots in RTDs studied by noise measurement

    International Nuclear Information System (INIS)

    Hees, S S; Kardynal, B E; Shields, A J; Farrer, I; Ritchie, D A

    2008-01-01

    We investigate the noise in quantum dot resonant tunnelling diodes (QDRTDs), where the quantum dots (QDs) placed in the collector experience electric fields that vary in a wide range. The trapping/detrapping of electrons on the QDs dominated the measured electrical noise. The model that we derived for the noise explains the experimental data well. The QD capture cross-section is one to two orders of magnitude smaller than the physical size of the QDs due to the reduced probability of capturing a hot electron on the QD. The model is a powerful tool to design the noise characteristics of QDRTD single photon-detectors

  19. Hot LO-phonon limited electron transport in ZnO/MgZnO channels

    Science.gov (United States)

    Šermukšnis, E.; Liberis, J.; Matulionis, A.; Avrutin, V.; Toporkov, M.; Özgür, Ü.; Morkoç, H.

    2018-05-01

    High-field electron transport in two-dimensional channels at ZnO/MgZnO heterointerfaces has been investigated experimentally. Pulsed current-voltage (I-V) and microwave noise measurements used voltage pulse widths down to 30 ns and electric fields up to 100 kV/cm. The samples investigated featured electron densities in the range of 4.2-6.5 × 1012 cm-2, and room temperature mobilities of 142-185 cm2/V s. The pulsed nature of the applied field ensured negligible, if any, change in the electron density, thereby allowing velocity extraction from current with confidence. The highest extracted electron drift velocity of ˜0.5 × 107 cm/s is somewhat smaller than that estimated for bulk ZnO; this difference is explained in the framework of longitudinal optical phonon accumulation (hot-phonon effect). The microwave noise data allowed us to rule out the effect of excess acoustic phonon temperature caused by Joule heating. Real-space transfer of hot electrons into the wider bandgap MgZnO layer was observed to be a limiting factor in samples with a high Mg content (48%), due to phase segregation and the associated local lowering of the potential barrier.

  20. Ion acoustic solitons and supersolitons in a magnetized plasma with nonthermal hot electrons and Boltzmann cool electrons

    Energy Technology Data Exchange (ETDEWEB)

    Rufai, O. R., E-mail: rajirufai@gmail.com; Bharuthram, R., E-mail: rbharuthram@uwc.ac.za [University of the Western Cape, Belville (South Africa); Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India)

    2014-08-15

    Arbitrary amplitude, ion acoustic solitons, and supersolitons are studied in a magnetized plasma with two distinct groups of electrons at different temperatures. The plasma consists of a cold ion fluid, cool Boltzmann electrons, and nonthermal energetic hot electrons. Using the Sagdeev pseudo-potential technique, the effect of nonthermal hot electrons on soliton structures with other plasma parameters is studied. Our numerical computation shows that negative potential ion-acoustic solitons and double layers can exist both in the subsonic and supersonic Mach number regimes, unlike the case of an unmagnetized plasma where they can only exist in the supersonic Mach number regime. For the first time, it is reported here that in addition to solitions and double layers, the ion-acoustic supersoliton solutions are also obtained for certain range of parameters in a magnetized three-component plasma model. The results show good agreement with Viking satellite observations of the solitary structures with density depletions in the auroral region of the Earth's magnetosphere.

  1. Investigation of the aluminium-aluminium oxide reversible transformation as observed by hot stage electron microscopy.

    Science.gov (United States)

    Grove, C. A.; Judd, G.; Ansell, G. S.

    1972-01-01

    Thin foils of high purity aluminium and an Al-Al2O3 SAP type of alloy were oxidised in a specially designed hot stage specimen chamber in an electron microscope. Below 450 C, amorphous aluminium oxide formed on the foil surface and was first detectable at foil edges, holes, and pits. Islands of aluminium then nucleated in this amorphous oxide. The aluminium islands displayed either a lateral growth with eventual coalescence with other islands, or a reoxidation process which caused the islands to disappear. The aluminium island formation was determined to be related to the presence of the electron beam. A mechanism based upon electron charging due to the electron beam was proposed to explain the nucleation, growth, coalescence, disappearance, and geometry of the aluminium islands.

  2. Hot electron and real space transfer in double-quantum-well structures

    International Nuclear Information System (INIS)

    Okuno, Eiichi; Sawaki, Nobuhiko; Akasaki, Isamu; Kano, Hiroyuki; Hashimoto, Masafumi.

    1991-01-01

    The hot electron phenomena and real space transfer (RST) effect are studied in GaAs/AlGaAs double-quantum-well (DQW) structures, in which we have two kind of quantum wells with different widths. The drift velocity and the electron temperature at liquid helium temperature are investigated as a function of the external electric field applied parallel to the heterointerface. By increasing the field, the electron temperature rises and reaches a plateau in the intermediate region, followed by further rise in the high-field region. The appearance of the plateau is attributed to the RST effect between the two quantum wells. The threshold field for the appearance of the plateau is determined by the difference energy between the quantized levels in two wells. The energy loss rate as a function of the electron temperature indicates that the RST is assisted by LO phonon scattering. (author)

  3. Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Khurgin, Jacob B., E-mail: jakek@jhu.edu [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Bajaj, Sanyam; Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-12-28

    Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

  4. Electron population uncertainty and atomic covalency

    International Nuclear Information System (INIS)

    Chesnut, D.B.

    2006-01-01

    The atoms-in-molecules (AIM) index of atomic covalency is directly related to the AIM atomic population uncertainty. The covalent bond order, delocalization index, and, therefore, the atomic covalency are maximal when electron pairs are equally shared by the atoms involved. When polarization effects are present, these measures of covalent bond character decrease. We present atomic covalences for the single- and double-heavy atom hydrides of elements of the first and second low rows of the periodic table to illustrate these effects. Some usual behavior is seen in hydrogen-bridged species due in some cases to stronger than expected multicenter bonds and in other cases to many atoms contributing to the covalency index

  5. X-rays diagnostics of the hot electron energy distribution in the intense laser interaction with metal targets

    Science.gov (United States)

    Kostenko, O. F.; Andreev, N. E.; Rosmej, O. N.

    2018-03-01

    A two-temperature hot electron energy distribution has been revealed by modeling of bremsstrahlung emission, measured by the radiation attenuation and half-shade methods, and Kα emission from a massive silver cylinder irradiated by a subpicosecond s-polarized laser pulse with a peak intensity of about 2 × 1019 W/cm2. To deduce parameters of the hot electron spectrum, we have developed semi-analytical models of generation and measurements of the x-rays. The models are based on analytical expressions and tabulated data on electron stopping power as well as cross-sections of generation and absorption of the x-rays. The Kα emission from thin silver foils deposited on low-Z substrates, both conducting and nonconducting, has been used to verify the developed models and obtained hot electron spectrum. The obtained temperatures of the colder and hotter electron components are in agreement with the values predicted by kinetic simulations of the cone-guided approach to fast ignition [Chrisman et al., Phys. Plasmas 15, 056309 (2008)]. The temperature of the low-energy component of the accelerated electron spectrum is well below the ponderomotive scaling and Beg's law. We have obtained relatively low conversion efficiency of laser energy into the energy of hot electrons propagating through the solid target of about 2%. It is demonstrated that the assumption about a single-temperature hot electron energy distribution with the slope temperature described by the ponderomotive scaling relationship, without detailed analysis of the hot electron spectrum, can lead to strong overestimation of the laser-to-electron energy-conversion efficiency, in particular, the conversion efficiency of laser energy into the high-temperature component of the hot electron distribution.

  6. Hot electron spatial distribution under presence of laser light self-focusing in over-dense plasmas

    International Nuclear Information System (INIS)

    Tanimoto, T; Yabuuchi, T; Habara, H; Kondo, K; Kodama, R; Mima, K; Tanaka, K A; Lei, A L

    2008-01-01

    In fast ignition for laser thermonuclear fusion, an ultra intense laser (UIL) pulse irradiates an imploded plasma in order to fast-heat a high-density core with hot electrons generated in laser-plasma interactions. An UIL pulse needs to make plasma channel via laser self-focusing and to propagate through the corona plasma to reach close enough to the core. Hot electrons are used for heating the core. Therefore the propagation of laser light in the high-density plasma region and spatial distribution of hot electron are important in issues in order to study the feasibility of this scheme. We measure the spatial distribution of hot electron when the laser light propagates into the high-density plasma region by self-focusing

  7. Scanning electron microscopy and transmission electron microscopy study of hot-deformed gamma-TiAl-based alloy microstructure.

    Science.gov (United States)

    Chrapoński, J; Rodak, K

    2006-09-01

    The aim of this work was to assess the changes in the microstructure of hot-deformed specimens made of alloys containing 46-50 at.% Al, 2 at.% Cr and 2 at.% Nb (and alloying additions such as carbon and boron) with the aid of scanning electron microscopy and transmission electron microscopy techniques. After homogenization and heat treatment performed in order to make diverse lamellae thickness, the specimens were compressed at 1000 degrees C. Transmission electron microscopy examinations of specimens after the compression test revealed the presence of heavily deformed areas with a high density of dislocation. Deformation twins were also observed. Dynamically recrystallized grains were revealed. For alloys no. 2 and no. 3, the recovery and recrystallization processes were more extensive than for alloy no. 1.

  8. Fast ions and hot electrons in the laser--plasma interaction

    International Nuclear Information System (INIS)

    Gitomer, S.J.; Jones, R.D.; Begay, F.; Ehler, A.W.; Kephart, J.F.; Kristal, R.

    1986-01-01

    Data on the emission of energetic ions produced in laser--matter interactions have been analyzed for a wide variety of laser wavelengths, energies, and pulse lengths. Strong correlation has been found between the bulk energy per AMU for fast ions measured by charge cups and the x-ray-determined hot electron temperature. Five theoretical models have been used to explain this correlation. The models include (1) a steady-state spherically symmetric fluid model with classical electron heat conduction, (2) a steady-state spherically symmetric fluid model with flux limited electron heat conduction, (3) a simple analytic model of an isothermal rarefaction followed by a free expansion, (4) the lasneX hydrodynamics code [Comments Plasma Phys. Controlled Fusion 2, 85 (1975)], calculations employing a spherical expansion and simple initial conditions, and (5) the lasneX code with its full array of absorption, transport, and emission physics. The results obtained with these models are in good agreement with the experiments and indicate that the detailed shape of the correlation curve between mean fast ion energy and hot electron temperature is due to target surface impurities at the higher temperatures (higher laser intensities) and to the expansion of bulk target material at the lower temperatures (lower laser intensities)

  9. Experimental study for angular distribution of the hot electrons generated by femtosecond laser interaction with solid targets

    International Nuclear Information System (INIS)

    Cai, D.F.; Gu, Y.Q.; Zheng, Z.J.; Wen, T.S.; Chunyu, S.T.; Wang, Z.B.; Yang, X.D.

    2003-01-01

    The experimental results of angular distribution of hot electrons in the interaction of a 60 fs, 125 mJ, 800 nm, ∼10 17 W cm -2 laser pulse with Al targets are reported. Three obvious peaks of hot electrons emission have been observed, as there is a weak normal component of the laser electric field. These emission peaks are located in the directions of the specular reflection of the laser, the target normal, and the backreflection of the laser, respectively. In the case of the P-polarized laser pulse, which has a strong normal component of the laser electric field, the peak in the backreflection of the laser disappeared, and only two obvious peaks of hot electron emissions existed. It shows that the different directions of hot electrons emission are dominated by different absorption or acceleration mechanisms. The experimental result of the hot electrons energy spectrum at the target normal shows that the effective temperature of hot electrons is about 190 keV, which is consistent with a scaling law of the resonance absorption

  10. Fundamental harmonic electron cyclotron emission for hot, loss-cone type distributions

    International Nuclear Information System (INIS)

    Bornatici, M.; Ruffina, U.; Westerhof, E.

    1988-01-01

    Electron cyclotron emission (ECE) is an important diagnostic tool for the study of hot plasmas. ECE can be used not only to measure the electron temperature but also to obtain information about non-thermal characteristics of the electron distribution function. One such a nonthermal characteristic is a loss-cone anisotropy. Loss-cone anisotropy can give rise to unstable growth of electro-magnetic waves around the harmonics of the electron cyclotron resonance and to increased emissivity of electron cyclotron waves. In case of high electron temperatures, also the dispersion properties of the extraordinary (X-) mode arond the fundamental electron cyclotron resonance are changed due to loss-cone anisotropy. The consequences of these dispersion properties for the emissivity of the fundamental harmonic X-mode are analyzed for perpendicular propagation. The emissivity, is calculated for two types of distribution functions having a loss-cone anisotropy. These distribution functions are a relativistic Dory-Guest-Harris type distribution function and modified relativistic Maxwellian distribution having a loss-cone with rounded edges (author). 9 refs.; 2 figs

  11. Prediction of hot electron production by ultraintense KrF laser-plasma interactions on solid-density targets

    International Nuclear Information System (INIS)

    Kato, Susumu; Takahashi, Eiichi; Miura, Eisuke; Owadano, Yoshiro; Nakamura, Tatsufumi; Kato, Tomokazu

    2002-01-01

    The scaling of hot electron temperature and the spectrum of electron energy by intense laser plasma interactions are reexamined from a viewpoint of the difference in laser wavelength. Laser plasma interaction such as parametric instabilities is usually determined by the Iλ2 scaling, where I and λ is the laser intensity and wavelength, respectively. However, the hot electron temperature is proportional to (ncr/ne0)1/2 [(1 + a 0 2 ) 1/2 - 1] rather than [(1 + a 0 2 ) 1/2 - 1] at the interaction with overdense plasmas, where ne0 is a electron density of overdense plasmas and a0 is a normalized laser intensity

  12. Proton probe measurement of fast advection of magnetic fields by hot electrons

    International Nuclear Information System (INIS)

    Willingale, L; Thomas, A G R; Nilson, P M; Kaluza, M C; Dangor, A E; Evans, R G; Fernandes, P; Haines, M G; Kamperidis, C; Kingham, R J; Ridgers, C P; Sherlock, M; Wei, M S; Najmudin, Z; Krushelnick, K; Bandyopadhyay, S; Notley, M; Minardi, S; Rozmus, W; Tatarakis, M

    2011-01-01

    A laser generated proton beam was used to measure the megagauss strength self-generated magnetic fields from a nanosecond laser interaction with an aluminum target. At intensities of 10 15 W cm −2 , the significant hot electron production and strong heat fluxes result in non-local transport becoming important to describe the magnetic field dynamics. Two-dimensional implicit Vlasov–Fokker–Planck modeling shows that fast advection of the magnetic field from the focal region occurs via the Nernst effect at significantly higher velocities than the sound speed, v N /c s ≈ 10.

  13. Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges

    International Nuclear Information System (INIS)

    Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A.; Vacelet, T.

    2014-01-01

    We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film

  14. Signatures of hot electrons and fluorescence in Mo Kα emission on Z

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, S. B.; Ampleford, D. J.; Cuneo, M. E.; Jones, B.; Jennings, C. A.; Coverdale, C. A.; Rochau, G. A.; Dunham, G. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Ouart, N.; Dasgupta, A.; Giuliani, J. L. [Naval Research Laboratory, Washington, DC 20375 (United States); Apruzese, J. P. [Consultant to NRL through Engility Corp., Chantilly, Virginia 20151 (United States)

    2014-03-15

    Recent experiments on the Z accelerator have produced high-energy (17 keV) inner-shell K-alpha emission from molybdenum wire array z-pinches. Extensive absolute power and spectroscopic diagnostics along with collisional-radiative modeling enable detailed investigation into the roles of thermal, hot electron, and fluorescence processes in the production of high-energy x-rays. We show that changing the dimensions of the arrays can impact the proportion of thermal and non-thermal K-shell x-rays.

  15. Modification of a scanning electron microscope for remote operation in a hot cell

    International Nuclear Information System (INIS)

    Reed, J.R.; Watson, H.E.; Smidt, F.A. Jr.

    1982-01-01

    Scanning electron microscopy (SEM) examination of broken fracture specimens is an essential part of the characterization of the failure mode of fracture toughness of specimens. The large specimen mass required for such examinations dictates the use of a shielded facility for performing such examinations on irradiated specimens. This report describes the modification of a commercial SEM for remote operation in a hot cell. The facility is used to examine specimens from several Navy and DOE-sponsored programs conducted at NRL which require the examination of radioactive materials

  16. Evidence of hot spot formation on carbon limiters due to thermal electron emission

    International Nuclear Information System (INIS)

    Philipps, V.; Samm, U.; Tokar, M.Z.; Unterberg, B.; Pospieszczyk, A.; Schweer, B.

    1993-01-01

    Carbon test limiters have been exposed in TEXTOR to high heat loads up to about 30 MW/m 2 . The evolutions of the surface temperature distribution and of the carbon release have been observed by means of local diagnostics. A sudden acceleration of the rise of the surface temperature has been found at a critical temperature of approx. 2400 deg. C. The increase of the rate of the temperature rise is consistent with an enhancement of the power loading by a factor of 2.5-3. Following the temperature jump (hot spot), a quasi-equilibrium temperature establishes at approx. 2700 deg. C. The development of the hot spot is explained by an increase of the local power loading to the breakdown of the sheath potential by thermal emission of electrons from the carbon surface. Simultaneously with the appearance of the hot spot, the carbon release from the surface increases sharply. This increase can be explained by normal thermal sublimation. Sublimation cooling contributes to the establishment of the quasi-equilibrium temperature at about 2700 deg. C. (author). 16 refs, 10 figs

  17. Modeling and Optimization of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applicaitons

    Science.gov (United States)

    Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.; Burns, M. J.; Kleinsasser, A. W.; Delin, K. A.; Vasquez, R. P.

    1996-01-01

    The development of a YBa(sub 2)Cu(sub 3)O(sub 7-(kronecker delta))(YBCO) hot-electron bolometer (HEB) quasioptical mixer for a 2.5 heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate. The mixer performance expected for this device is analyzed in the framework of a two-temperature model which includes heating both of the electrons and the lattice. Also, the contribution of heat diffusion from the film through the substrate and from the film to the normal metal contacts is evaluated....a single sideband temperature of less than 2000k is predicted.

  18. Establishment of design space for high current gain in III-N hot electron transistors

    Science.gov (United States)

    Gupta, Geetak; Ahmadi, Elaheh; Suntrup, Donald J., III; Mishra, Umesh K.

    2018-01-01

    This paper establishes the design space of III-N hot electron transistors (HETs) for high current gain by designing and fabricating HETs with scaled base thickness. The device structure consists of GaN-based emitter, base and collector regions where emitter and collector barriers are implemented using AlN and InGaN layers, respectively, as polarization-dipoles. Electrons tunnel through the AlN layer to be injected into the base at a high energy where they travel in a quasi-ballistic manner before being collected. Current gain increases from 1 to 3.5 when base thickness is reduced from 7 to 4 nm. The extracted mean free path (λ mfp) is 5.8 nm at estimated injection energy of 1.5 eV.

  19. Experimental Route to Scanning Probe Hot Electron Nanoscopy (HENs) Applied to 2D Material

    KAUST Repository

    Giugni, Andrea

    2017-06-09

    This paper presents details on a new experimental apparatus implementing the hot electron nanoscopy (HENs) technique introduced for advanced spectroscopies on structure and chemistry in few molecules and interface problems. A detailed description of the architecture used for the laser excitation of surface plasmons at an atomic force microscope (AFM) tip is provided. The photogenerated current from the tip to the sample is detected during the AFM scan. The technique is applied to innovative semiconductors for applications in electronics: 2D MoS2 single crystal and a p-type SnO layer. Results are supported by complementary scanning Kelvin probe microscopy, traditional conductive AFM, and Raman measurements. New features highlighted by HEN technique reveal details of local complexity in MoS2 and polycrystalline structure of SnO at nanometric scale otherwise undetected. The technique set in this paper is promising for future studies in nanojunctions and innovative multilayered materials, with new insight on interfaces.

  20. Effect of energetic electrons on dust charging in hot cathode filament discharge

    Science.gov (United States)

    Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.

    2011-03-01

    The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.

  1. Effect of energetic electrons on dust charging in hot cathode filament discharge

    International Nuclear Information System (INIS)

    Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.

    2011-01-01

    The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.

  2. Probing hot-electron effects in wide area plasmonic surfaces using X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ayas, Sencer; Cupallari, Andi; Dana, Aykutlu, E-mail: aykutlu@unam.bilkent.edu.tr [UNAM Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey)

    2014-12-01

    Plasmon enhanced hot carrier formation in metallic nanostructures increasingly attracts attention due to potential applications in photodetection, photocatalysis, and solar energy conversion. Here, hot-electron effects in nanoscale metal-insulator-metal (MIM) structures are investigated using a non-contact X-ray photoelectron spectroscopy based technique using continuous wave X-ray and laser excitations. The effects are observed through shifts of the binding energy of the top metal layer upon excitation with lasers of 445, 532, and 650 nm wavelength. The shifts are polarization dependent for plasmonic MIM grating structures fabricated by electron beam lithography. Wide area plasmonic MIM surfaces fabricated using a lithography free route by the dewetting of evaporated Ag on HfO{sub 2} exhibit polarization independent optical absorption and surface photovoltage. Using a simple model and making several assumptions about the magnitude of the photoemission current, the responsivity and external quantum efficiency of wide area plasmonic MIM surfaces are estimated as 500 nA/W and 11 × 10{sup −6} for 445 nm illumination.

  3. Submolecular Gates Self-Assemble for Hot-Electron Transfer in Proteins.

    Science.gov (United States)

    Filip-Granit, Neta; Goldberg, Eran; Samish, Ilan; Ashur, Idan; van der Boom, Milko E; Cohen, Hagai; Scherz, Avigdor

    2017-07-27

    Redox reactions play key roles in fundamental biological processes. The related spatial organization of donors and acceptors is assumed to undergo evolutionary optimization facilitating charge mobilization within the relevant biological context. Experimental information from submolecular functional sites is needed to understand the organization strategies and driving forces involved in the self-development of structure-function relationships. Here we exploit chemically resolved electrical measurements (CREM) to probe the atom-specific electrostatic potentials (ESPs) in artificial arrays of bacteriochlorophyll (BChl) derivatives that provide model systems for photoexcited (hot) electron donation and withdrawal. On the basis of computations we show that native BChl's in the photosynthetic reaction center (RC) self-assemble at their ground-state as aligned gates for functional charge transfer. The combined computational and experimental results further reveal how site-specific polarizability perpendicular to the molecular plane enhances the hot-electron transport. Maximal transport efficiency is predicted for a specific, ∼5 Å, distance above the center of the metalized BChl, which is in remarkably close agreement with the distance and mutual orientation of corresponding native cofactors. These findings provide new metrics and guidelines for analysis of biological redox centers and for designing charge mobilizing machines such as artificial photosynthesis.

  4. An experimental determination of the hot electron ring geometry in a Bumpy Torus and its implications for Bumpy Torus stability

    International Nuclear Information System (INIS)

    Hillis, D.L.; Wilgen, J.B.; Bigelow, T.S.; Jaeger, E.F.; Swain, D.W.; Hankins, O.E.; Juhala, R.E.

    1986-10-01

    The hot electron rings of the ELMO Bumpy Torus (EBT) [Plasma Physics and Controlled Nuclear Fusion (IAEA, Vienna, 1975), Vol. II, p. 141] are formed by electron cyclotron resonance heating (ECRH) and have an electron temperature of 350 to 500 keV. The original intention of these hot electron rings was to provide a local minimum in the magnetic field and, thereby, stabilize the simple interchange and flute modes, which are inherent in a closed field line bumpy torus. To evaluate the electron energy density of the EBT rings and determine if enough stored energy is present to provide a local minimum in the magnetic field, a detailed understanding of the spatial distribution of the rings is imperative. The purpose of this report is to measure the ring thickness and investigate its implications for bumpy torus stability. The spatial location and radial profile of the hot electron ring are measured with a unique metal ball pellet injector, which injects small metallic balls into the EBT ring plasma. From these measurements the radial extent (or ring thickness) is about 5 to 7 cm full width at half maximum for typical EBT operation, which is much larger than previously expected. These measurements and recent modeling of the EBT plasma indicate that the hot electron ring's stored energy may not be sufficient to produce a local minimum in the magnetic field

  5. An Ultrasensitive Hot-Electron Bolometer for Low-Background SMM Applications

    Science.gov (United States)

    Olayaa, David; Wei, Jian; Pereverzev, Sergei; Karasik, Boris S.; Kawamura, Jonathan H.; McGrath, William R.; Sergeev, Andrei V.; Gershenson, Michael E.

    2006-01-01

    We are developing a hot-electron superconducting transition-edge sensor (TES) that is capable of counting THz photons and operates at T = 0.3K. The main driver for this work is moderate resolution spectroscopy (R approx. 1000) on the future space telescopes with cryogenically cooled (approx. 4 K) mirrors. The detectors for these telescopes must be background-limited with a noise equivalent power (NEP) approx. 10(exp -19)-10(exp -20) W/Hz(sup 1/2) over the range v = 0.3-10 THz. Above about 1 THz, the background photon arrival rate is expected to be approx. 10-100/s), and photon counting detectors may be preferable to an integrating type. We fabricated superconducting Ti nanosensors with a volume of approx. 3x10(exp -3) cubic microns on planar substrate and have measured the thermal conductance G to the thermal bath. A very low G = 4x10(exp -14) W/K, measured at 0.3 K, is due to the weak electron-phonon coupling in the material and the thermal isolation provided by superconducting Nb contacts. This low G corresponds to NEP(0.3K) = 3x10(exp -19) W/Hz(sup 1/2). This Hot-Electron Direct Detector (HEDD) is expected to have a sufficient energy resolution for detecting individual photons with v > 0.3 THz at 0.3 K. With the sensor time constant of a few microseconds, the dynamic range is approx. 50 dB.

  6. Generation and Transport of Hot Electrons in Cone-Wire Targets

    Science.gov (United States)

    Beg, Farhat

    2009-11-01

    We present results from a series of experiments where cone-wire targets in various configurations were employed both to assess hot electron coupling efficiency, and to reveal the source temperature of the hot electrons. Initial experiments were performed on the Vulcan petawatt laser at the Rutherford Appleton Laboratory and Titan laser at the Lawrence Livermore National Laboratory. Results with aluminum cones joined to Cu wires of diameters from 10 to 40 μm show that the laser coupling efficiency to electron energy within the wire is proportional to the cross sectional area of the wire. In addition, coupling into the wire was observed to decrease with the laser prepulse and cone-wall thickness. More recently, this study was extended, using the OMEGA EP laser. The resulting changes in coupling energy give indications of the scaling as we approach FI-relevant conditions. Requirements for FI scale fast ignition cone parameters: tip thickness, wall thickness, laser prepulse and laser pulse length, will be discussed. In collaboration with T. Yabuuchi, T. Ma, D. Higginson, H. Sawada, J. King, M.H. Key, K.U. Akli, Al Elsholz, D. Batani, H. Chen, R.R. Freeman, L. Gizzi, J. Green, S. Hatchett, D. Hey, P. Jaanimagi, J. Koch, K. L. Lancaster, D.Larson, A.J. MacKinnon, H. McLean, A. MacPhee, P.A. Norreys, P.K Patel, R. B. Stephens, W. Theobald, R. Town, M. Wei, S. Wilks, Roger Van Maren, B. Westover and L. VanWoerkom.

  7. Low-Noise Wide Bandwith, Hot Electron Bolometer Mixers for Submillimeter Wavelengths

    Science.gov (United States)

    McGrath, W. R.

    1995-01-01

    Recently a novel superconductive hot-electron micro-bolometer has been proposed which is both fast and sensitive (D. E. Prober, Appl. Phys. Lett. 62, 2119, 1993). This device has several important properties which make it useful as a heterodyne sensor for radioastronomy applications at frequencies above 1 THz. The thermal response time of the device is fast enough, several 10's of picoseconds, to allow for IF's of several GHz. This bolometer mixer should operate well up to at least 10 THz. There is no energy gap limitation as in an SIS mixer, since the mixing process relies on heating of the electron gas. In fact, rf power is absorbed more uniformly above the gap frequency. The mixer noise should be near quantum-limited, and the local oscillator (LO) power requirement is very low: / 10 nW for a Nb device. One of the unique features of this device is that it employs rapid electron diffusion into a normal metal, rather than phonon emission, as the thermal conductance that cools the heated electrons. In order for diffusion to dominate over phonon emission, the device must be short, less than 0.5.

  8. Resonant plasmonic terahertz detection in vertical graphene-base hot-electron transistors

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhii, V. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University and Institute of Ultra High Frequency Semiconductor Electronics of RAS, Moscow 111005 (Russian Federation); Otsuji, T. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Ryzhii, M. [Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580 (Japan); Mitin, V. [Department of Electrical Engineering, University at Buffalo, SUNY, Buffalo, New York 1460-1920 (United States); Shur, M. S. [Department of Electrical, Computer, and System Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2015-11-28

    We analyze dynamic properties of vertical graphene-base hot-electron transistors (GB-HETs) and consider their operation as detectors of terahertz (THz) radiation using the developed device model. The GB-HET model accounts for the tunneling electron injection from the emitter, electron propagation across the barrier layers with the partial capture into the GB, and the self-consistent oscillations of the electric potential and the hole density in the GB (plasma oscillations), as well as the quantum capacitance and the electron transit-time effects. Using the proposed device model, we calculate the responsivity of GB-HETs operating as THz detectors as a function of the signal frequency, applied bias voltages, and the structural parameters. The inclusion of the plasmonic effect leads to the possibility of the GB-HET operation at the frequencies significantly exceeding those limited by the characteristic RC-time. It is found that the responsivity of GB-HETs with a sufficiently perfect GB exhibits sharp resonant maxima in the THz range of frequencies associated with the excitation of plasma oscillations. The positions of these maxima are controlled by the applied bias voltages. The GB-HETs can compete with and even surpass other plasmonic THz detectors.

  9. Femtosecond-laser induced dynamics of CO on Ru(0001): Deep insights from a hot-electron friction model including surface motion

    Science.gov (United States)

    Scholz, Robert; Floß, Gereon; Saalfrank, Peter; Füchsel, Gernot; Lončarić, Ivor; Juaristi, J. I.

    2016-10-01

    A Langevin model accounting for all six molecular degrees of freedom is applied to femtosecond-laser induced, hot-electron driven dynamics of Ru(0001)(2 ×2 ):CO. In our molecular dynamics with electronic friction approach, a recently developed potential energy surface based on gradient-corrected density functional theory accounting for van der Waals interactions is adopted. Electronic friction due to the coupling of molecular degrees of freedom to electron-hole pairs in the metal are included via a local density friction approximation, and surface phonons by a generalized Langevin oscillator model. The action of ultrashort laser pulses enters through a substrate-mediated, hot-electron mechanism via a time-dependent electronic temperature (derived from a two-temperature model), causing random forces acting on the molecule. The model is applied to laser induced lateral diffusion of CO on the surface, "hot adsorbate" formation, and laser induced desorption. Reaction probabilities are strongly enhanced compared to purely thermal processes, both for diffusion and desorption. Reaction yields depend in a characteristic (nonlinear) fashion on the applied laser fluence, as well as branching ratios for various reaction channels. Computed two-pulse correlation traces for desorption and other indicators suggest that aside from electron-hole pairs, phonons play a non-negligible role for laser induced dynamics in this system, acting on a surprisingly short time scale. Our simulations on precomputed potentials allow for good statistics and the treatment of long-time dynamics (300 ps), giving insight into this system which hitherto has not been reached. We find generally good agreement with experimental data where available and make predictions in addition. A recently proposed laser induced population of physisorbed precursor states could not be observed with the present low-coverage model.

  10. X-ray spectroscopy of warm and hot electron components in the CAPRICE source plasma at EIS testbench at GSI

    Energy Technology Data Exchange (ETDEWEB)

    Mascali, D., E-mail: davidmascali@lns.infn.it; Celona, L.; Castro, G.; Torrisi, G.; Neri, L.; Gammino, S.; Ciavola, G. [Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, – Via S. Sofia 62, 95123 Catania (Italy); Maimone, F.; Maeder, J.; Tinschert, K.; Spaedtke, K. P.; Rossbach, J.; Lang, R. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt (Germany); Romano, F. P. [Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, – Via S. Sofia 62, 95123 Catania (Italy); IBAM, CNR, Via Biblioteca 4, 95124 Catania (Italy); Musumarra, A.; Altana, C.; Caliri, C. [Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, – Via S. Sofia 62, 95123 Catania (Italy); Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-15

    An experimental campaign aiming to detect X radiation emitted by the plasma of the CAPRICE source – operating at GSI, Darmstadt – has been carried out. Two different detectors (a SDD – Silicon Drift Detector and a HpGe – hyper-pure Germanium detector) have been used to characterize the warm (2–30 keV) and hot (30–500 keV) electrons in the plasma, collecting the emission intensity and the energy spectra for different pumping wave frequencies and then correlating them with the CSD of the extracted beam measured by means of a bending magnet. A plasma emissivity model has been used to extract the plasma density along the cone of sight of the SDD and HpGe detectors, which have been placed beyond specific collimators developed on purpose. Results show that the tuning of the pumping frequency considerably modifies the plasma density especially in the warm electron population domain, which is the component responsible for ionization processes: a strong variation of the plasma density near axis region has been detected. Potential correlations with the charge state distribution in the plasma are explored.

  11. X-ray spectroscopy of warm and hot electron components in the CAPRICE source plasma at EIS testbench at GSI.

    Science.gov (United States)

    Mascali, D; Celona, L; Maimone, F; Maeder, J; Castro, G; Romano, F P; Musumarra, A; Altana, C; Caliri, C; Torrisi, G; Neri, L; Gammino, S; Tinschert, K; Spaedtke, K P; Rossbach, J; Lang, R; Ciavola, G

    2014-02-01

    An experimental campaign aiming to detect X radiation emitted by the plasma of the CAPRICE source - operating at GSI, Darmstadt - has been carried out. Two different detectors (a SDD - Silicon Drift Detector and a HpGe - hyper-pure Germanium detector) have been used to characterize the warm (2-30 keV) and hot (30-500 keV) electrons in the plasma, collecting the emission intensity and the energy spectra for different pumping wave frequencies and then correlating them with the CSD of the extracted beam measured by means of a bending magnet. A plasma emissivity model has been used to extract the plasma density along the cone of sight of the SDD and HpGe detectors, which have been placed beyond specific collimators developed on purpose. Results show that the tuning of the pumping frequency considerably modifies the plasma density especially in the warm electron population domain, which is the component responsible for ionization processes: a strong variation of the plasma density near axis region has been detected. Potential correlations with the charge state distribution in the plasma are explored.

  12. Hot-Electron Bolometer Mixers on Silicon-on-Insulator Substrates for Terahertz Frequencies

    Science.gov (United States)

    Skalare, Anders; Stern, Jeffrey; Bumble, Bruce; Maiwald, Frank

    2005-01-01

    A terahertz Hot-Electron Bolometer (HEB) mixer design using device substrates based on Silicon-On-Insulator (SOI) technology is described. This substrate technology allows very thin chips (6 pm) with almost arbitrary shape to be manufactured, so that they can be tightly fitted into a waveguide structure and operated at very high frequencies with only low risk for power leakages and resonance modes. The NbTiN-based bolometers are contacted by gold beam-leads, while other beamleads are used to hold the chip in place in the waveguide test fixture. The initial tests yielded an equivalent receiver noise temperature of 3460 K double-sideband at a local oscillator frequency of 1.462 THz and an intermediate frequency of 1.4 GHz.

  13. Electron-positron pair production in a hot accretion plasma around a massive black hole

    International Nuclear Information System (INIS)

    Takahara, Fumio; Kusunose, Masaaki.

    1985-01-01

    We investigate the electron-positron pair production in a hot accretion plasma around a supermassive black hole in connection with active galactic nuclei. Assuming that an optically thin two-temperature plasma is produced in the vicinity of the central black hole, we examine the condition for the significant pair production by comparing relevant time scales. Since the pair production is dominated by collisions between hard photons, the conditions for significant pair production depend on the production rate of hard photons. We examine the case where the unsaturated Comptonization of soft photons produces hard photons as well as that of bremsstrahlung. We show that significant pair production occurs for a moderately high accretion rate with relatively slow accretion flow as compared to the free fall velocity in both cases. Possible consequences of pair production are briefly discussed. (author)

  14. Identification of conduction and hot electron property in ZnS, ZnO and SiO2

    International Nuclear Information System (INIS)

    Huang Jinzhao; Xu Zheng; Zhao Suling; Li Yuan; Yuan Guangcai; Wang Yongsheng; Xu Xurong

    2007-01-01

    The impact excitation and ionization is the most important process in layered optimization scheme and solid state cathodoluminescence. The conduction property (semiconductor property) of SiO 2 , ZnS and ZnO is studied based on organic/inorganic electroluminescence. The hot electron property (acceleration and multiplication property) of SiO 2 and ZnS is investigated based on the solid state cathodoluminescence. The results show that the SiO 2 has the fine hot electron property and the conduction property is not as good as ZnO and ZnS

  15. Hot electron light emission in gallium arsenide/aluminium(x) gallium(1-x) arsenic heterostructures

    Science.gov (United States)

    Teke, Ali

    In this thesis we have demonstrated the operation of a novel tunable wavelength surface light emitting device. The device is based on a p-GaAs, and n-Ga1- xAlxAs heterojunction containing an inversion layer on the p- side, and GaAs quantum wells on the n- side, and, is referred to as HELLISH-2 (Hot Electron Light Emitting and Lasing in Semiconductor Heterostructure-Type 2). The devices utilise hot electron longitudinal transport and, therefore, light emission is independent of the polarity of the applied voltage. The wavelength of the emitted light can be tuned with the applied bias from GaAs band-to-band transition in the inversion layer to e1-hh1 transition in the quantum wells. In this work tunable means that the device can be operated at either single or multiple wavelength emission. The operation of the device requires only two diffused in point contacts. In this project four HELLISH-2 samples coded as ES1, ES2, ES6 and QT919 have been studied. First three samples were grown by MBE and the last one was grown by MOVPE techniques. ES1 was designed for single and double wavelength operation. ES2 was a control sample used to compare our results with previous work on HELLISH-2 and ES6 was designed for single, double and triple wavelength operation. Theoretical modelling of the device operation was carried out and compared with the experimental results. HELLISH-2 structure was optimised for low threshold and high efficiency operation as based on our model calculations. The last sample QT919 has been designed as an optimised device for single and double wavelength operation like ES1. HELLISH-2 has a number of advantages over the conventional light emitters, resulting in some possible applications, such as light logic gates and wavelength division multiplexing in optoelectronic.

  16. Influence of laser induced hot electrons on the threshold for shock ignition of fusion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Colaïtis, A.; Ribeyre, X.; Le Bel, E.; Duchateau, G.; Nicolaï, Ph.; Tikhonchuk, V. [Centre Lasers Intenses et Applications, Université de Bordeaux - CNRS - CEA, UMR 5107,351 Cours de la Libération, 33400 Talence (France)

    2016-07-15

    The effects of Hot Electrons (HEs) generated by the nonlinear Laser-Plasma Interaction (LPI) on the dynamics of Shock Ignition Inertial Confinement Fusion targets are investigated. The coupling between the laser beam, plasma dynamics and hot electron generation and propagation is described with a radiative hydrodynamics code using an inline model based on Paraxial Complex Geometrical Optics [Colaïtis et al., Phys. Rev. E 92, 041101 (2015)]. Two targets are considered: the pure-DT HiPER target and a CH-DT design with baseline spike powers of the order of 200–300 TW. In both cases, accounting for the LPI-generated HEs leads to non-igniting targets when using the baseline spike powers. While HEs are found to increase the ignitor shock pressure, they also preheat the bulk of the imploding shell, notably causing its expansion and contamination of the hotspot with the dense shell material before the time of shock convergence. The associated increase in hotspot mass (i) increases the ignitor shock pressure required to ignite the fusion reactions and (ii) significantly increases the power losses through Bremsstrahlung X-ray radiation, thus rapidly cooling the hotspot. These effects are less prominent for the CH-DT target where the plastic ablator shields the lower energy LPI-HE spectrum. Simulations using higher laser spike powers of 500 TW suggest that the CH-DT capsule marginally ignites, with an ignition window width significantly smaller than without LPI-HEs, and with three quarters of the baseline target yield. The latter effect arises from the relation between the shock launching time and the shell areal density, which becomes relevant in presence of a LPI-HE preheating.

  17. Ignition conditions relaxation for central hot-spot ignition with an ion-electron non-equilibrium model

    Science.gov (United States)

    Fan, Zhengfeng; Liu, Jie

    2016-10-01

    We present an ion-electron non-equilibrium model, in which the hot-spot ion temperature is higher than its electron temperature so that the hot-spot nuclear reactions are enhanced while energy leaks are considerably reduced. Theoretical analysis shows that the ignition region would be significantly enlarged in the hot-spot rhoR-T space as compared with the commonly used equilibrium model. Simulations show that shocks could be utilized to create and maintain non-equilibrium conditions within the hot spot, and the hot-spot rhoR requirement is remarkably reduced for achieving self-heating. In NIF high-foot implosions, it is observed that the x-ray enhancement factors are less than unity, which is not self-consistent and is caused by assuming Te =Ti. And from this non-consistency, we could infer that ion-electron non-equilibrium exists in the high-foot implosions and the ion temperature could be 9% larger than the equilibrium temperature.

  18. YBCO hot-electron bolometers dedicated to THz detection and imaging: Embedding issues

    International Nuclear Information System (INIS)

    Aurino, M; Tuerer, I; Martinez, A; Gensbittel, A; Degardin, A F; Kreisler, A J

    2010-01-01

    High-T c hot-electron bolometers (HEB) are an interesting alternative to other superconducting heterodyne mixers in the terahertz frequency range because of low-cost cooling investment, ultra-wide instantaneous bandwidth and low intrinsic noise level, even at 80 K. A technological process to fabricate stacked yttrium-based (YBCO) / praseodymium-based (PBCO) ultra-thin films (in the 15 to 40 nm thickness range) etched to form 0.5 μm x 0.5 μm constrictions, elaborated on (100) MgO substrates, has been previously described. Ageing effects were also considered, with the consequence of increased electrical resistance, significant degradation of the regular THz response and no HEB mixing action. Electron and UV lithography steps are revisited here to realize HEB mixers based on nano-bridges covered by a log-periodic planar gold antenna, dedicated to the 1 to 7 THz range. Several measures have been attempted to reduce the conversion losses, mainly by considering the embedding issues related to the YBCO nano-bridge impedance matching to the antenna and the design of optimized intermediate frequency circuitry. Antenna simulations were performed and validated through experiments on scaled models at GHz frequencies. Electromagnetic coupling to the incoming radiation was also studied, including crosstalk between neighbour antennas forming a linear imaging array.

  19. Analysis of a high-Tc hot-electron superconducting mixer for terahertz applications

    International Nuclear Information System (INIS)

    Karasik, B.S.; McGrath, W.R.; Gaidis, M.C.

    1997-01-01

    The prospects of a YBa 2 Cu 3 O 7-δ hot-electron bolometer mixer for a THz heterodyne receiver are discussed. The modeled device is a submicron bridge made from a 10-nm-thick film on a high thermal conductance substrate. The mixer performance expected for this device is analyzed in the framework of a two-temperature model which includes heating both of the electrons and the lattice. Also, the contribution of phonon diffusion from the film through the substrate and from the film to the normal metal contacts is evaluated. The intrinsic conversion efficiency and the noise temperature have been calculated as functions of the device size, local oscillator (LO) power, and ambient temperature. Assuming thermal fluctuations and Johnson noise to be the main sources of noise, a minimum single sideband mixer noise temperature of congruent 2000 K is predicted. For our modeled device the intrinsic conversion loss at an intermediate frequency of 2.5 GHz is less than 10 dB and the required LO power is ∼1 endash 10 μW. copyright 1997 American Institute of Physics

  20. Physical basis of power conversion of energy fluctuations of hot electrons

    Energy Technology Data Exchange (ETDEWEB)

    Yater, J C

    1983-12-01

    The design of an experimental reversible-energy-fluctuation (REF) solar converter using hot nonequilibrated (HNE) electrons is presented. The physical principles are introduced, and an idealized model is described and analyzed in terms of radiation and electron-thermalization losses and first-to-third-layer transfer times. It is shown that the 93-percent limiting conversion efficiency can be approached in both a two-level and an N-level model, even in larger-scale circuits. On the other hand, as circuit size is decreased below 100 nm, the maximum power output can exceed 10 MW/sq m. The materials and thicknesses to be used in an experimental thin-film version of the REF device are outlined, including a 10-60-nm-thick Cd3As2 or alpha-Sn absorbing layer, a 4-10-nm-thick doped-semiconductor or semimetal quantum-well layer, and a Schottky-barrier diode layer comprising a 4-10-nm-thick Pb sheet on a 5-20-nm-thick p-GaAs film. Experiments at lattice temperatures of from 300 to 1 K with input radiation at wavelengths from 1 micron to the solar spectrum and intensities from zero to 1 mW are planned to determine whether the predicted practical efficiency of 80 percent can be obtained. 19 references.

  1. Laser generated hot electron transport in an externally applied magnetic field

    International Nuclear Information System (INIS)

    Burnett, N.H.; Enright, G.D.

    1986-01-01

    The authors have investigated the effect of an externally applied DC magnetic field on the generation and transport of hot electrons in CO/sub 2/ laser irradiation of cylindrical targets. The targets used in these studies were 6.3 mm diameter metal rods through which a pulsed current was driven from an external capacitor. Magnetic fields up to 150 kgauss were produced at the target surface. The CO/sub 2/ laser was focused with an f/5 lens resulting in a laser intensity of ≅3 x 10/sup 14/ W/cm/sup 2/ in a 100 μm diameter focal spot. The effect of the external magnetic field on the generation and inward transport of superhot (≥ 100 keV) electrons was studied. Principal diagnostics included a six channel hard x-ray spectrometer, a high energy x-ray pinhole camera, a LiF Laue x-ray spectrograph and a Ross-filtered (W-Ta) pair of x-ray detectors. The latter two diagnostics were designed to detect Au Kα /sub emission at 68.2 keV

  2. Effect of excess superthermal hot electrons on finite amplitude ion-acoustic solitons and supersolitons in a magnetized auroral plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rufai, O. R., E-mail: rrufai@csir.co.za [Council for Scientific and Industrial Research, Pretoria (South Africa); Bharuthram, R., E-mail: rbharuthram@uwc.ac.za [University of the Western Cape, Bellville (South Africa); Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi, Mumbai-410218 (India)

    2015-10-15

    The effect of excess superthermal electrons is investigated on finite amplitude nonlinear ion-acoustic waves in a magnetized auroral plasma. The plasma model consists of a cold ion fluid, Boltzmann distribution of cool electrons, and kappa distributed hot electron species. The model predicts the evolution of negative potential solitons and supersolitons at subsonic Mach numbers region, whereas, in the case of Cairn's nonthermal distribution model for the hot electron species studied earlier, they can exist both in the subsonic and supersonic Mach number regimes. For the dayside auroral parameters, the model generates the super-acoustic electric field amplitude, speed, width, and pulse duration of about 18 mV/m, 25.4 km/s, 663 m, and 26 ms, respectively, which is in the range of the Viking spacecraft measurements.

  3. Microstructural characterization by electron backscatter diffraction of a hot worked Al-Cu-Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Cepeda-Jimenez, C.M., E-mail: cm.cepeda@cenim.csic.es [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain); Hidalgo, P.; Carsi, M.; Ruano, O.A.; Carreno, F. [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain)

    2011-03-25

    Research highlights: {yields} The most favourable conditions for hot workability have been determined. {yields} EBSD was employed to characterize the obtained microtexture and microstructure. {yields} The Al 2024 alloy torsion tested at 408 deg. C and 2.1 s{sup -1} showed maximum ductility. {yields} Solid solution and fine precipitates favour a fine microstructure at 408 deg. C. {yields} The increase in test temperature to 467 deg. C produces a sharp decrease in ductility. - Abstract: Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted in the range 278-467 deg. C, and at two strain rates, 2.1 and 4.5 s{sup -1}. Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure before and after testing. The microstructural evolution during torsion deformation at different temperatures and strain rate conditions determines the mechanical properties at room temperature of the Al 2024 alloy since grain refining, dynamic precipitation and precipitate coalescence occur during the torsion test. These mechanical properties were measured by Vickers microhardness tests. At 408 deg. C and 2.1 s{sup -1} the optimum combination of solid solution and incipient precipitation gives rise to maximum ductility and large fraction of fine and misoriented grains (f{sub HAB} = 54%). In contrast, the increase in test temperature to 467 deg. C produces a sharp decrease in ductility, attributed to the high proportion of alloying elements in solid solution. Both the stress-strain flow curves obtained by torsion tests and the final microstructures are a consequence of recovery phenomena and the dynamic nature of the precipitation process taking place during deformation.

  4. Microstructural characterization by electron backscatter diffraction of a hot worked Al-Cu-Mg alloy

    International Nuclear Information System (INIS)

    Cepeda-Jimenez, C.M.; Hidalgo, P.; Carsi, M.; Ruano, O.A.; Carreno, F.

    2011-01-01

    Research highlights: → The most favourable conditions for hot workability have been determined. → EBSD was employed to characterize the obtained microtexture and microstructure. → The Al 2024 alloy torsion tested at 408 deg. C and 2.1 s -1 showed maximum ductility. → Solid solution and fine precipitates favour a fine microstructure at 408 deg. C. → The increase in test temperature to 467 deg. C produces a sharp decrease in ductility. - Abstract: Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted in the range 278-467 deg. C, and at two strain rates, 2.1 and 4.5 s -1 . Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure before and after testing. The microstructural evolution during torsion deformation at different temperatures and strain rate conditions determines the mechanical properties at room temperature of the Al 2024 alloy since grain refining, dynamic precipitation and precipitate coalescence occur during the torsion test. These mechanical properties were measured by Vickers microhardness tests. At 408 deg. C and 2.1 s -1 the optimum combination of solid solution and incipient precipitation gives rise to maximum ductility and large fraction of fine and misoriented grains (f HAB = 54%). In contrast, the increase in test temperature to 467 deg. C produces a sharp decrease in ductility, attributed to the high proportion of alloying elements in solid solution. Both the stress-strain flow curves obtained by torsion tests and the final microstructures are a consequence of recovery phenomena and the dynamic nature of the precipitation process taking place during deformation.

  5. All-inorganic perovskite nanocrystal assisted extraction of hot electrons and biexcitons from photoexcited CdTe quantum dots.

    Science.gov (United States)

    Mondal, Navendu; De, Apurba; Samanta, Anunay

    2018-01-03

    Excitation of semiconductor quantum dots (QDs) by photons possessing energy higher than the band-gap creates a hot electron-hole pair, which releases its excess energy as waste heat or under certain conditions (when hν > 2E g ) produces multiple excitons. Extraction of these hot carriers and multiple excitons is one of the key strategies for enhancing the efficiency of QD-based photovoltaic devices. However, this is a difficult task as competing carrier cooling and relaxation of multiple excitons (through Auger recombination) are ultrafast processes. Herein, we study the potential of all-inorganic perovskite nanocrystals (NCs) of CsPbX 3 (X = Cl, Br) as harvesters of these short-lived species from photo-excited CdTe QDs. The femtosecond transient absorption measurements show CsPbX 3 mediated extraction of both hot and thermalized electrons of the QDs (under a low pump power) and (under a high pump fluence) extraction of multiple excitons prior to their Auger assisted recombination. A faster timescale of thermalized electron transfer (∼2 ps) and a higher extraction efficiency of hot electrons (∼60%) are observed in the presence of CsPbBr 3 . These observations demonstrate the potential of all-inorganic perovskite NCs in the extraction of these short-lived energy rich species implying that complexes of the QDs and perovskite NCs are better suited for improving the efficiency of QD-sensitized solar cells.

  6. Development of a microbial population within a hot-drinks vending machine and the microbial load of vended hot chocolate drink.

    Science.gov (United States)

    Hall, A; Short, K; Saltmarsh, M; Fielding, L; Peters, A

    2007-09-01

    In order to understand the development of the microbial population within a hot-drinks vending machine a new machine was placed in a staff area of a university campus vending only hot chocolate. The machine was cleaned weekly using a detergent based protocol. Samples from the mixing bowl, dispense area, and drink were taken over a 19-wk period and enumerated using plate count agar. Bacillus cereus was identified using biochemical methods. Vended drinks were sampled at 0, 3, 6, and 9 min after vending; the hot chocolate powder was also sampled. Over the 1st 8 wk, a significant increase in the microbial load of the machine components was observed. By the end of the study, levels within the vended drink had also increased significantly. Inactivation of the automatic flush over a subsequent 5-wk period led to a statistically but not operationally significant increase in the microbial load of the dispense area and vended drink. The simple weekly clean had a significant impact on the microbial load of the machine components and the vended drink. This study demonstrated that a weekly, detergent-based cleaning protocol was sufficient to maintain the microbial population of the mixing bowl and dispense point in a quasi-steady state below 3.5 log CFU/cm2 ensuring that the microbial load of the vended drinks was maintained below 3.4 log CFU/mL. The microbial load of the drinks showed no significant changes over 9 min after vending, suggesting only spores are present in the final product.

  7. Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments.

    Science.gov (United States)

    Rosenberg, M J; Solodov, A A; Myatt, J F; Seka, W; Michel, P; Hohenberger, M; Short, R W; Epstein, R; Regan, S P; Campbell, E M; Chapman, T; Goyon, C; Ralph, J E; Barrios, M A; Moody, J D; Bates, J W

    2018-02-02

    Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the first time to regimes of electron density scale length (∼500 to 700  μm), electron temperature (∼3 to 5 keV), and laser intensity (6 to 16×10^{14}  W/cm^{2}) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRS sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ∼0.7% to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ∼4×10^{14} to ∼6×10^{14}  W/cm^{2}. These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.

  8. Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments

    Science.gov (United States)

    Rosenberg, M. J.; Solodov, A. A.; Myatt, J. F.; Seka, W.; Michel, P.; Hohenberger, M.; Short, R. W.; Epstein, R.; Regan, S. P.; Campbell, E. M.; Chapman, T.; Goyon, C.; Ralph, J. E.; Barrios, M. A.; Moody, J. D.; Bates, J. W.

    2018-01-01

    Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the first time to regimes of electron density scale length (˜500 to 700 μ m ), electron temperature (˜3 to 5 keV), and laser intensity (6 to 16 ×1014 W /cm2 ) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRS sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ˜0.7 % to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ˜4×10 14 to ˜6 ×1014 W /cm2 . These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.

  9. Hot-electron bolometer terahertz mixers for the Herschel Space Observatory.

    Science.gov (United States)

    Cherednichenko, Sergey; Drakinskiy, Vladimir; Berg, Therese; Khosropanah, Pourya; Kollberg, Erik

    2008-03-01

    We report on low noise terahertz mixers (1.4-1.9 THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performance was characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5 to 2.5 THz, with 30 GHz resolution) and also by measuring the mixer noise temperature at a limited number of discrete frequencies. The lowest mixer noise temperature recorded was 750 K [double sideband (DSB)] at 1.6 THz and 950 K DSB at 1.9 THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4-4.8 GHz, the mixer noise temperature was 1100 K DSB at 1.6 THz and 1450 K DSB at 1.9 THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEB stability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200-500 nW range.

  10. Inhibition of the electron cyclotron maser instability in the dense magnetosphere of a hot Jupiter

    Science.gov (United States)

    Daley-Yates, S.; Stevens, I. R.

    2018-06-01

    Hot Jupiter (HJ) type exoplanets are expected to produce strong radio emission in the MHz range via the Electron Cyclotron Maser Instability (ECMI). To date, no repeatable detections have been made. To explain the absence of observational results, we conduct 3D adaptive mess refinement (AMR) magnetohydrodynamic (MHD) simulations of the magnetic interactions between a solar type star and HJ using the publicly available code PLUTO. The results are used to calculate the efficiency of the ECMI at producing detectable radio emission from the planets magnetosphere. We also calculate the frequency of the ECMI emission, providing an upper and lower bounds, placing it at the limits of detectability due to Earth's ionospheric cutoff of ˜10 MHz. The incident kinetic and magnetic power available to the ECMI is also determined and a flux of 0.075 mJy for an observer at 10 pc is calculated. The magnetosphere is also characterized and an analysis of the bow shock which forms upstream of the planet is conducted. This shock corresponds to the thin shell model for a colliding wind system. A result consistent with a colliding wind system. The simulation results show that the ECMI process is completely inhibited by the planets expanding atmosphere, due to absorption of UV radiation form the host star. The density, velocity, temperature and magnetic field of the planetary wind are found to result in a magnetosphere where the plasma frequency is raised above that due to the ECMI process making the planet undetectable at radio MHz frequencies.

  11. Terahertz imaging and spectroscopy based on hot electron bolometer (HEB) heterodyne detection

    Science.gov (United States)

    Gerecht, Eyal; You, Lixing

    2008-02-01

    Imaging and spectroscopy at terahertz frequencies have great potential for healthcare, plasma diagnostics, and homeland security applications. Terahertz frequencies correspond to energy level transitions of important molecules in biology and astrophysics. Terahertz radiation (T-rays) can penetrate clothing and, to some extent, can also penetrate biological materials. Because of their shorter wavelengths, they offer higher spatial resolution than do microwaves or millimeter waves. We are developing hot electron bolometer (HEB) mixer receivers for heterodyne detection at terahertz frequencies. HEB detectors provide unprecedented sensitivity and spectral resolution at terahertz frequencies. We describe the development of a two-pixel focal plane array (FPA) based on HEB technology. Furthermore, we have demonstrated a fully automated, two-dimensional scanning, passive imaging system based on our HEB technology operating at 0.85 THz. Our high spectral resolution terahertz imager has a total system noise equivalent temperature difference (NEΔT) value of better than 0.5 K and a spatial resolution of a few millimeters. HEB technology is becoming the basis for advanced terahertz imaging and spectroscopic technologies for the study of biological and chemical agents over the entire terahertz spectrum.

  12. Hot gas cleaning in power stations by using electron beam technology. Influence on PAH emissions

    International Nuclear Information System (INIS)

    Callen, M.S.; de la Cruz, M.T.; Mastral, A.M.; Murillo, R.; Marinov, S.; Stefanova, M.

    2007-01-01

    The Electron Beam Technology (EBT), proven treatment for SO 2 and NO x removal, is applied to different power stations as a hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO 2 and NO x , studying EBT effects from an organic environmental point of view. The PAH quantification was performed by using a very sensitive analytical technique, gas chromatography with mass spectrometry mass spectrometry detection (GC-MS-MS). Results showed that PAH are influenced by the EBT showing a reduction of the most volatile PAH in the gas phase. With regard to the solid by-products obtained after the irradiation, fertilizers, similar PAH concentration to the fly ashes produced when no irradiation is applied were found. These fertilizers were considered like unpolluted soils being adequate for agriculture applications with PAH concentrations below the target value set up by the Dutch government. (author)

  13. Infrared hot-electron NbN superconducting photodetectors for imaging applications

    International Nuclear Information System (INIS)

    Il'in, K.S.; Gol'tsman, G.N.; Verevkin, A.A.; Sobolewski, Roman

    1999-01-01

    We report an effective quantum efficiency of 340, responsivity >200 A W -1 (>10 4 V W -1 ) and response time of 27±5 ps at temperatures close to the superconducting transition for NbN superconducting hot-electron photodetectors (HEPs) in the near-infrared and optical ranges. Our studies were performed on a few nm thick NbN films deposited on sapphire substrates and patterned into μm-size multibridge detector structures, incorporated into a coplanar transmission line. The time-resolved photoresponse was studied by means of subpicosecond electro-optic sampling with 100 fs wide laser pulses. The quantum efficiency and responsivity studies of our photodetectors were conducted using an amplitude-modulated infrared beam, fibre-optically coupled to the device. The observed picosecond response time and the very high efficiency and sensitivity of the NbN HEPs make them an excellent choice for infrared imaging photodetectors and input optical-to-electrical transducers for superconducting digital circuits. (author)

  14. Fabrication of an Aluminum Based Hot Electron Mixer for Terahertz Applications

    Science.gov (United States)

    Echternach, P. M.; LeDuc, H. G.; Skalare, A.; McGrath, W. R.

    2000-01-01

    Aluminum based diffusion cooled hot electron bolometers (HEB) mixers, predicted to have better noise, bandwidth and to require less LO power than Nb based diffusion cooled HEBs, have been fabricated. Preliminary DC tests were performed. The bolometer elements consisted of short (0.1 to 0.3 micron), narrow (0.08 to 0. 15 micron) and thin (11 nm) aluminum wires connected to large contact pads consisting of a novel trilayer Al/Ti/Au. The patterns were defined by electron beam lithography and the metal deposition involved a double angle process, the Aluminum wires being deposited straight on and the pads being deposited at a 45 degree angle without breaking vacuum. The Al/Ti/Au trilayer was developed to provide a way of making contact between the aluminum wire and the gold antenna. The Titanium layer acts as a diffusion barrier to avoid damage of the Aluminum contact and bolometer wire and to lower the transition temperature of the pads to below that of the bolometer wire. The Au layer avoids the formation of an oxide on the Ti layer and provides good electrical contact to the IF/antenna structure. The resistance of the bolometers as a function of temperature was measured. It is clear that below the transition temperature of the wire (1.8K) but above the transition temperature of the contact pads (0.6K), the proximity effect drives most of the bolometer wire normal, causing a very broad transition. This effect should not affect the performance of the bolometers since they will be operated at a temperature below the TC of the pads. This is evident from the IV characteristics measured at 0.3K. RF characterization tests will begin shortly.

  15. Fermi-degeneracy and discrete-ion effects in the spherical-cell model and electron-electron correlation effects in hot dense plasmas

    International Nuclear Information System (INIS)

    Furukawa, H.; Nishihara, K.

    1992-01-01

    The spherical-cell model [F. Perrot, Phys. Rev. A 25, 489 (1982); M. W. C. Dharma-wardana and F. Perrot, ibid. 26, 2096 (1982)] is improved to investigate laser-produced hot, dense plasmas. The free-electron distribution function around a test free electron is calculated by using the Fermi integral in order that the free-electron--free-electron correlation function includes Fermi-degeneracy effects, and also that the calculation includes the discrete-ion effect. The free-electron--free-electron, free-electron--ion, and ion-ion correlation effects are coupled, within the framework of the hypernetted-chain approximation, through the Ornstein-Zernike relation. The effective ion-ion potential includes the effect of a spatial distribution of bound electrons. The interparticle correlation functions and the effective potential acting on either an electron or an ion in hot, dense plasmas are calculated numerically. The Fermi-degeneracy effect on the correlation functions between free electrons becomes clear for the degeneracy parameter θ approx-lt 1. The discrete-ion effect in the calculation of the correlation functions between free electrons affects the electron-ion pair distribution functions for r s approx-gt 3. As an application of the proposed model, the strong-coupling effect on the stopping power of charged particles [Xin-Zhong Yan, S. Tanaka, S. Mitake, and S. Ichimaru, Phys. Rev. A 32, 1785 (1985)] is estimated. While the free-electron--ion strong-coupling effect and the Fermi-degeneracy effect incorporated in the calculation of the free-electron distribution function around a test free electron enhance the stopping number, the quantum-diffraction effect incorporated in the quantal hypernetted-chain equations [J. Chihara, Prog. Theor. Phys. 72, 940 (1984); Phys. Rev. A 44, 1247 (1991); J. Phys. Condens. Matter 3, 8715 (1991)] reduces the stopping number substantially

  16. Mass-loss evolution of close-in exoplanets: Evaporation of hot Jupiters and the effect on population

    International Nuclear Information System (INIS)

    Kurokawa, H.; Nakamoto, T.

    2014-01-01

    During their evolution, short-period exoplanets may lose envelope mass through atmospheric escape owing to intense X-ray and extreme ultraviolet (XUV) radiation from their host stars. Roche-lobe overflow induced by orbital evolution or intense atmospheric escape can also contribute to mass loss. To study the effects of mass loss on inner planet populations, we calculate the evolution of hot Jupiters considering mass loss of their envelopes and thermal contraction. Mass loss is assumed to occur through XUV-driven atmospheric escape and the following Roche-lobe overflow. The runaway effect of mass loss results in a dichotomy of populations: hot Jupiters that retain their envelopes and super Earths whose envelopes are completely lost. Evolution primarily depends on the core masses of planets and only slightly on migration history. In hot Jupiters with small cores (≅ 10 Earth masses), runaway atmospheric escape followed by Roche-lobe overflow may create sub-Jupiter deserts, as observed in both mass and radius distributions of planetary populations. Comparing our results with formation scenarios and observed exoplanets populations, we propose that populations of closely orbiting exoplanets are formed by capturing planets at/inside the inner edges of protoplanetary disks and subsequent evaporation of sub-Jupiters.

  17. Mass-loss evolution of close-in exoplanets: Evaporation of hot Jupiters and the effect on population

    Energy Technology Data Exchange (ETDEWEB)

    Kurokawa, H. [Department of Physics, Nagoya Univsersity, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan); Nakamoto, T., E-mail: kurokawa@nagoya-u.jp [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2014-03-01

    During their evolution, short-period exoplanets may lose envelope mass through atmospheric escape owing to intense X-ray and extreme ultraviolet (XUV) radiation from their host stars. Roche-lobe overflow induced by orbital evolution or intense atmospheric escape can also contribute to mass loss. To study the effects of mass loss on inner planet populations, we calculate the evolution of hot Jupiters considering mass loss of their envelopes and thermal contraction. Mass loss is assumed to occur through XUV-driven atmospheric escape and the following Roche-lobe overflow. The runaway effect of mass loss results in a dichotomy of populations: hot Jupiters that retain their envelopes and super Earths whose envelopes are completely lost. Evolution primarily depends on the core masses of planets and only slightly on migration history. In hot Jupiters with small cores (≅ 10 Earth masses), runaway atmospheric escape followed by Roche-lobe overflow may create sub-Jupiter deserts, as observed in both mass and radius distributions of planetary populations. Comparing our results with formation scenarios and observed exoplanets populations, we propose that populations of closely orbiting exoplanets are formed by capturing planets at/inside the inner edges of protoplanetary disks and subsequent evaporation of sub-Jupiters.

  18. Spin-dependent hot electron transport and nano-scale magnetic imaging of metal/Si structures

    International Nuclear Information System (INIS)

    Kaidatzis, A.

    2008-10-01

    In this work, we experimentally study spin-dependent hot electron transport through metallic multilayers (ML), containing single magnetic layers or 'spin-valve' (SV) tri layers. For this purpose, we have set up a ballistic electron emission microscope (BEEM), a three terminal extension of scanning tunnelling microscopy on metal/semiconductor structures. The implementation of the BEEM requirements into the sample fabrication is described in detail. Using BEEM, the hot electron transmission through the ML's was systematically measured in the energy range 1-2 eV above the Fermi level. By varying the magnetic layer thickness, the spin-dependent hot electron attenuation lengths were deduced. For the materials studied (Co and NiFe), they were compared to calculations and other determinations in the literature. For sub-monolayer thickness, a non uniform morphology was observed, with large transmission variations over sub-nano-metric distances. This effect is not yet fully understood. In the imaging mode, the magnetic configurations of SV's were studied under field, focusing on 360 degrees domain walls in Co layers. The effects of the applied field intensity and direction on the DW structure were studied. The results were compared quantitatively to micro-magnetic calculations, with an excellent agreement. From this, it can be shown that the BEEM magnetic resolution is better than 50 nm. (author)

  19. Transition-Edge Hot-Electron Microbolometers for Millimeter and Submillimeter Astrophysics

    Science.gov (United States)

    Hsieh, Wen-Ting; Stevenson, Thomas; U-yen, Kongpop; Wollack, Edward; Barrentine, Emily

    2014-01-01

    The millimeter and the submillimeter wavelengths of the electromagnetic spectrum hold a wealth of information about the evolution of the universe. In particular, cosmic microwave background (CMB) radiation and its polarization carry the oldest information in the universe, and provide the best test of the inflationary paradigm available to astronomy today. Detecting gravity waves through their imprint on the CMB polarization would have extraordinary repercussions for cosmology and physics. A transition-edge hot-electron micro - bolometer (THM) consists of a superconducting bilayer transition-edge sensor (TES) with a thin-film absorber. Unlike traditional monolithic bolometers that make use of micromachined structures, the THM em ploys the decoupling between electrons and phonons at millikelvin temperatures to provide thermal isolation. The devices are fabricated photolithographically and are easily integrated with antennas via microstrip transmission lines, and with SQUID (superconducting quantum interference device) readouts. The small volume of the absorber and TES produces a short thermal time constant that facilitates rapid sky scanning. The THM consists of a thin-film metal absorber overlapping a superconducting TES. The absorber forms the termination of a superconducting microstripline that carries RF power from an antenna. The purpose of forming a separate absorber and TES is to allow flexibility in the optimization of the two components. In particular, the absorbing film's impedance can be chosen to match the antenna, while the TES impedance can be chosen to match to the readout SQUID amplifier. This scheme combines the advantages of the TES with the advantages of planar millimeter-wave transmission line circuits. Antenna-coupling to the detectors via planar transmission lines allows the detector dimensions to be much smaller than a wavelength, so the technique can be extended across the entire microwave, millimeter, and submillimeter wavelength ranges. The

  20. Influence of lateral target size on hot electron production and electromagnetic pulse emission from laser-irradiated metallic targets

    International Nuclear Information System (INIS)

    Chen Ziyu; Li Jianfeng; Yu Yong; Li Xiaoya; Peng Qixian; Zhu Wenjun; Wang Jiaxiang

    2012-01-01

    The influences of lateral target size on hot electron production and electromagnetic pulse emission from laser interaction with metallic targets have been investigated. Particle-in-cell simulations at high laser intensities show that the yield of hot electrons tends to increase with lateral target size, because the larger surface area reduces the electrostatic field on the target, owing to its expansion along the target surface. At lower laser intensities and longer time scales, experimental data characterizing electromagnetic pulse emission as a function of lateral target size also show target-size effects. Charge separation and a larger target tending to have a lower target potential have both been observed. The increase in radiation strength and downshift in radiation frequency with increasing lateral target size can be interpreted using a simple model of the electrical capacity of the target.

  1. Influence of lateral target size on hot electron production and electromagnetic pulse emission from laser-irradiated metallic targets

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ziyu; Li Jianfeng; Yu Yong; Li Xiaoya; Peng Qixian; Zhu Wenjun [National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Wang Jiaxiang [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China)

    2012-11-15

    The influences of lateral target size on hot electron production and electromagnetic pulse emission from laser interaction with metallic targets have been investigated. Particle-in-cell simulations at high laser intensities show that the yield of hot electrons tends to increase with lateral target size, because the larger surface area reduces the electrostatic field on the target, owing to its expansion along the target surface. At lower laser intensities and longer time scales, experimental data characterizing electromagnetic pulse emission as a function of lateral target size also show target-size effects. Charge separation and a larger target tending to have a lower target potential have both been observed. The increase in radiation strength and downshift in radiation frequency with increasing lateral target size can be interpreted using a simple model of the electrical capacity of the target.

  2. Auto-correlation of velocity-fluctuations and frequency-dependent diffusion constant for hot electrons

    International Nuclear Information System (INIS)

    Roy, M.D.; Nag, B.R.

    1981-01-01

    A method has been developed for determining the auto-correlation functions of the fluctuations in the transverse and the parallel components of hot carrier-velocity in a semiconductor by Monte Carlo simulation. The functions for electrons in InSb are determined by this method for applied electric fields of 50 V/cm, 75 V/cm, and 100 V/cm. With increasing value of the time interval the transverse auto-correlation function fall nearly exponentially to zero, but the parallel function falls sharply to a negative peak, then rises to positive values and finally becomes zero. The interval beyond which the auto-correlation function is zero and the correlation time are also evaluated. The correlation time is found to be approximately 1.6 times the relaxation time calculated from the chord mobility. The effect of the flight sampling time on the value of variance of the displacement, is investigated in terms of the low frequency diffusion constants, determined from the variation of the correlation functions. It is found that the diffusion constants become independent of the sampling time if it is of the order of one hundred times the relaxation time. The frequency-dependent diffusion constants are calculated from the correlation functions. The transverse diffusion constant falls monotonically with frequency for all the field strengths studied. The parallel diffusion constant has similar variation for the lower fields (50 V/cm and 75 V/cm) but it has a peak at about 44 GHz for the field of 100 V/cm. (orig.)

  3. Reliable determination of the Cu/n-Si Schottky barrier height by using in-device hot-electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu; Atxabal, Ainhoa; Ribeiro, Mário; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Llopis, Roger [CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country (Spain); Casanova, Fèlix; Hueso, Luis E., E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu [CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country (Spain)

    2015-11-02

    We show the operation of a Cu/Al{sub 2}O{sub 3}/Cu/n-Si hot-electron transistor for the straightforward determination of a metal/semiconductor energy barrier height even at temperatures below carrier-freeze out in the semiconductor. The hot-electron spectroscopy measurements return a fairly temperature independent value for the Cu/n-Si barrier of 0.66 ± 0.04 eV at temperatures below 180 K, in substantial accordance with mainstream methods based on complex fittings of either current-voltage (I-V) and capacitance-voltage (C-V) measurements. The Cu/n-Si hot-electron transistors exhibit an OFF current of ∼2 × 10{sup −13} A, an ON/OFF ratio of ∼10{sup 5}, and an equivalent subthreshold swing of ∼96 mV/dec at low temperatures, which are suitable values for potential high frequency devices.

  4. Reliable determination of the Cu/n-Si Schottky barrier height by using in-device hot-electron spectroscopy

    International Nuclear Information System (INIS)

    Parui, Subir; Atxabal, Ainhoa; Ribeiro, Mário; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Llopis, Roger; Casanova, Fèlix; Hueso, Luis E.

    2015-01-01

    We show the operation of a Cu/Al 2 O 3 /Cu/n-Si hot-electron transistor for the straightforward determination of a metal/semiconductor energy barrier height even at temperatures below carrier-freeze out in the semiconductor. The hot-electron spectroscopy measurements return a fairly temperature independent value for the Cu/n-Si barrier of 0.66 ± 0.04 eV at temperatures below 180 K, in substantial accordance with mainstream methods based on complex fittings of either current-voltage (I-V) and capacitance-voltage (C-V) measurements. The Cu/n-Si hot-electron transistors exhibit an OFF current of ∼2 × 10 −13  A, an ON/OFF ratio of ∼10 5 , and an equivalent subthreshold swing of ∼96 mV/dec at low temperatures, which are suitable values for potential high frequency devices

  5. Current gain above 10 in sub-10 nm base III-Nitride tunneling hot electron transistors with GaN/AlN emitter

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhichao, E-mail: zcyang.phys@gmail.com; Zhang, Yuewei; Krishnamoorthy, Sriram; Nath, Digbijoy N. [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Khurgin, Jacob B. [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2016-05-09

    We report on a tunneling hot electron transistor amplifier with common-emitter current gain greater than 10 at a collector current density in excess of 40 kA/cm{sup 2}. The use of a wide-bandgap GaN/AlN (111 nm/2.5 nm) emitter was found to greatly improve injection efficiency of the emitter and reduce cold electron leakage. With an ultra-thin (8 nm) base, 93% of the injected hot electrons were collected, enabling a common-emitter current gain up to 14.5. This work improves understanding of the quasi-ballistic hot electron transport and may impact the development of high speed devices based on unipolar hot electron transport.

  6. ON THE ROLE AND ORIGIN OF NONTHERMAL ELECTRONS IN HOT ACCRETION FLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Niedźwiecki, Andrzej; Stȩpnik, Agnieszka [Department of Astrophysics, University of Łódź, Pomorska 149/153, 90-236 Łódź (Poland); Xie, Fu-Guo, E-mail: niedzwiecki@uni.lodz.pl, E-mail: agajer@o2.pl, E-mail: fgxie@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

    2015-02-01

    We study the X-ray spectra of tenuous, two-temperature accretion flows using a model involving an exact, Monte Carlo computation of the global Comptonization effect as well as a general relativistic description of both the flow structure and radiative processes. In our previous work, we found that in flows surrounding supermassive black holes, thermal synchrotron radiation is not capable of providing a sufficient seed photon flux to explain the X-ray spectral indices as well as the cut-off energies measured in several best-studied active galactic nuclei (AGNs). In this work, we complete the model by including seed photons provided by nonthermal synchrotron radiation and we find that it allows us to reconcile the hot flow model with the AGN data. We take into account two possible sources of nonthermal electrons. First, we consider e {sup ±} produced by charged-pion decay, which should always be present in the innermost part of a two-temperature flow due to proton-proton interactions. We find that for a weak heating of thermal electrons (small δ) the synchrotron emission of pion-decay e {sup ±} is much stronger than the thermal synchrotron emission in the considered range of bolometric luminosities, L ∼ (10{sup –4}-10{sup –2}) L {sub Edd}. The small-δ model including hadronic effects, in general, agrees with the AGN data, except for the case of a slowly rotating black hole and a thermal distribution of protons. For large δ, the pion-decay e {sup ±} have a negligible effect and, in this model, we consider nonthermal electrons produced by direct acceleration. We find an approximate agreement with the AGN data for the fraction of the heating power of electrons, which is used for the nonthermal acceleration η ∼ 0.1. However, for constant η and δ, the model predicts a positive correlation of the X-ray spectral index with the Eddington ratio, and hence a fine tuning of η and/or δ with the accretion rate is required to explain the negative correlation

  7. Lower-hybrid wave penetration and effects on electron population

    International Nuclear Information System (INIS)

    Dupas, L.; Grelot, P.; Parlange, F.; Weisse, J.

    1981-01-01

    In a high-power-density lower-hybrid experiment (approximately 10kW.cm -2 ), a parallel index spectrum was measured and the radial position where sidebands are excited was deduced from pump and sideband wavenumber measurements. On this basis, some considerations on wave propagation are given which are compatible with some effects observed on electron population. (author)

  8. Effects of lower hybrid fast electron populations on electron temperature measurements at JET

    International Nuclear Information System (INIS)

    Tanzi, C.P.; Bartlett, D.V.; Schunke, B.

    1993-01-01

    The Lower Hybrid Current Drive (LHCD) system on JET has to date achieved up to 1.5 MA of driven current. This current is carried by a fast electron population with energies more than ten times the electron temperature and density about 10 -4 of the bulk plasma. This paper discusses the effects of this fast electron population on our ability to make reliable temperature measurements using ECE and reviews the effects on other plasma diagnostics which rely on ECE temperature measurements for their interpretation. (orig.)

  9. Signatures of Hot Molecular Hydrogen Absorption from Protoplanetary Disks. I. Non-thermal Populations

    Energy Technology Data Exchange (ETDEWEB)

    Hoadley, Keri; France, Kevin; Arulanantham, Nicole; Loyd, R. O. Parke; Kruczek, Nicholas, E-mail: keri.hoadley@colorado.edu [Laboratory for Atmospheric and Space Physics (LASP), University of Colorado Space Science Building (SPSC), 3665 Discovery Drive, Boulder, CO 80303 (United States)

    2017-09-01

    The environment around protoplanetary disks (PPDs) regulates processes that drive the chemical and structural evolution of circumstellar material. We perform a detailed empirical survey of warm molecular hydrogen (H{sub 2}) absorption observed against H i-Ly α (Ly α : λ 1215.67) emission profiles for 22 PPDs, using archival Hubble Space Telescope ultraviolet (UV) spectra to identify H{sub 2} absorption signatures and quantify the column densities of H{sub 2} ground states in each sightline. We compare thermal equilibrium models of H{sub 2} to the observed H{sub 2} rovibrational level distributions. We find that, for the majority of targets, there is a clear deviation in high-energy states ( T {sub exc} ≳ 20,000 K) away from thermal equilibrium populations ( T (H{sub 2}) ≳ 3500 K). We create a metric to estimate the total column density of non-thermal H{sub 2} ( N (H{sub 2}){sub nLTE}) and find that the total column densities of thermal ( N (H{sub 2})) and N (H{sub 2}){sub nLTE} correlate for transition disks and targets with detectable C iv-pumped H{sub 2} fluorescence. We compare N (H{sub 2}) and N (H{sub 2}){sub nLTE} to circumstellar observables and find that N (H{sub 2}){sub nLTE} correlates with X-ray and far-UV luminosities, but no correlations are observed with the luminosities of discrete emission features (e.g., Ly α , C iv). Additionally, N (H{sub 2}) and N (H{sub 2}){sub nLTE} are too low to account for the H{sub 2} fluorescence observed in PPDs, so we speculate that this H{sub 2} may instead be associated with a diffuse, hot, atomic halo surrounding the planet-forming disk. We create a simple photon-pumping model for each target to test this hypothesis and find that Ly α efficiently pumps H{sub 2} levels with T {sub exc} ≥ 10,000 K out of thermal equilibrium.

  10. Design of nanophotonic, hot-electron solar-blind ultraviolet detectors with a metal-oxide-semiconductor structure

    International Nuclear Information System (INIS)

    Wang, Zhiyuan; Wang, Xiaoxin; Liu, Jifeng

    2014-01-01

    Solar-blind ultraviolet (UV) detection refers to photon detection specifically in the wavelength range of 200 nm–320 nm. Without background noises from solar radiation, it has broad applications from homeland security to environmental monitoring. The most commonly used solid state devices for this application are wide band gap (WBG) semiconductor photodetectors (Eg > 3.5 eV). However, WBG semiconductors are difficult to grow and integrate with Si readout integrated circuits (ROICs). In this paper, we design a nanophotonic metal-oxide-semiconductor structure on Si for solar-blind UV detectors. Instead of using semiconductors as the active absorber, we use Sn nano-grating structures to absorb UV photons and generate hot electrons for internal photoemission across the Sn/SiO 2 interfacial barrier, thereby generating photocurrent between the metal and the n-type Si region upon UV excitation. Moreover, the transported hot electron has an excess kinetic energy >3 eV, large enough to induce impact ionization and generate another free electron in the conduction band of n-Si. This process doubles the quantum efficiency. On the other hand, the large metal/oxide interfacial energy barrier (>3.5 eV) also enables solar-blind UV detection by blocking the less energetic electrons excited by visible photons. With optimized design, ∼75% UV absorption and hot electron excitation can be achieved within the mean free path of ∼20 nm from the metal/oxide interface. This feature greatly enhances hot electron transport across the interfacial barrier to generate photocurrent. The simple geometry of the Sn nano-gratings and the MOS structure make it easy to fabricate and integrate with Si ROICs compared to existing solar-blind UV detection schemes. The presented device structure also breaks through the conventional notion that photon absorption by metal is always a loss in solid-state photodetectors, and it can potentially be extended to other active metal photonic devices. (paper)

  11. Self-consistent average-atom scheme for electronic structure of hot and dense plasmas of mixture

    International Nuclear Information System (INIS)

    Yuan Jianmin

    2002-01-01

    An average-atom model is proposed to treat the electronic structures of hot and dense plasmas of mixture. It is assumed that the electron density consists of two parts. The first one is a uniform distribution with a constant value, which is equal to the electron density at the boundaries between the atoms. The second one is the total electron density minus the first constant distribution. The volume of each kind of atom is proportional to the sum of the charges of the second electron part and of the nucleus within each atomic sphere. By this way, one can make sure that electrical neutrality is satisfied within each atomic sphere. Because the integration of the electron charge within each atom needs the size of that atom in advance, the calculation is carried out in a usual self-consistent way. The occupation numbers of electron on the orbitals of each kind of atom are determined by the Fermi-Dirac distribution with the same chemical potential for all kinds of atoms. The wave functions and the orbital energies are calculated with the Dirac-Slater equations. As examples, the electronic structures of the mixture of Au and Cd, water (H 2 O), and CO 2 at a few temperatures and densities are presented

  12. Self-consistent average-atom scheme for electronic structure of hot and dense plasmas of mixture.

    Science.gov (United States)

    Yuan, Jianmin

    2002-10-01

    An average-atom model is proposed to treat the electronic structures of hot and dense plasmas of mixture. It is assumed that the electron density consists of two parts. The first one is a uniform distribution with a constant value, which is equal to the electron density at the boundaries between the atoms. The second one is the total electron density minus the first constant distribution. The volume of each kind of atom is proportional to the sum of the charges of the second electron part and of the nucleus within each atomic sphere. By this way, one can make sure that electrical neutrality is satisfied within each atomic sphere. Because the integration of the electron charge within each atom needs the size of that atom in advance, the calculation is carried out in a usual self-consistent way. The occupation numbers of electron on the orbitals of each kind of atom are determined by the Fermi-Dirac distribution with the same chemical potential for all kinds of atoms. The wave functions and the orbital energies are calculated with the Dirac-Slater equations. As examples, the electronic structures of the mixture of Au and Cd, water (H2O), and CO2 at a few temperatures and densities are presented.

  13. MICROBIAL POPULATION OF HOT SPRING WATERS IN ESKİŞEHİR/TURKEY

    Directory of Open Access Journals (Sweden)

    Nalan YILMAZ SARIÖZLÜ

    2012-02-01

    Full Text Available In order to investigate and find out the bacterial community of hot spring waters in Eskişehir, Turkey, 7 hot spring water samples were collected from 7 different hot springs. All samples were inoculated using four different media (nutrient agar, water yeast extract agar, trypticase soy agar, starch casein agar. After incubation at 50 ºC for 14 days, all bacterial colonies were counted and purified. Gram reaction, catalase and oxidase properties of all isolates were determined and investigated by BIOLOG, VITEK and automated ribotyping system (RiboPrinter. The resistance of these bacteriawas examined against ampiciline, gentamisine, trimethoprime-sulphamethoxazole and tetracycline. As a result, heat resistant pathogenic microorganisms in addition to human normal flora were determined in hot spring waters (43-50 ºC in investigated area. Ten different species belong to 6 genera were identified as Alysiella filiformis, Bordetella bronchiseptica, B. pertussis, Molexalla caprae, M. caviae, M. cuniculi, M. phenylpyruvica, Roseomonas fauriae, Delftia acidovorans and Pseudomonas taetrolens.

  14. Direct observation of the growth of voids in multifilamentary superconducting materials via hot stage scanning electron microscopy

    International Nuclear Information System (INIS)

    Wang, J.L.F.; Holthuis, J.T.; Pickus, M.R.; Lindberg, R.W.

    1978-11-01

    The need for large high field magnetic devices has focused attention on multifilamentary superconductors based on A15 compounds such as Nb 3 Sn. The commercial bronze process for fabricating multifilamentary superconducting Nb 3 Sn wires was developed. A major problem is strain sensitivity when long reaction times are employed. An improved hot stage for the scanning electron microscope was constructed to study the formation of the A15 phase by solid state diffusion. The nucleation and growth of voids near the interface of the A15 phase (Nb 3 Sn) and matrix were observed, monitored, and recorded on video tape. Successive layers of material heated in the hot stage were subsequently removed and the new surfaces were re-examined, using SEM-EDX and optical microscopy, to confirm the fact that the observed porosity was indeed a bulk rather than a surface phenomenon. These voids are considered to be a primary cause for degrading the mechanical, thermal and superconducting properties

  15. Analysis of recrystallization behavior of hot-deformed austenite reconstructed from electron backscattering diffraction orientation maps of lath martensite

    International Nuclear Information System (INIS)

    Kubota, Manabu; Ushioda, Kohsaku; Miyamoto, Goro; Furuhara, Tadashi

    2016-01-01

    The recrystallization behavior of hot-deformed austenite of a 0.55% C steel at 800 °C was investigated by a method of reconstructing the parent austenite orientation map from an electron backscattering diffraction orientation map of lath martensite. Recrystallized austenite grains were clearly distinguished from un-recrystallized austenite grains. Very good correlation was confirmed between the static recrystallization behavior investigated mechanically by double-hit compression tests and the change in austenite microstructure evaluated by the reconstruction method. The recrystallization behavior of hot-deformed 0.55% C steel at 800 °C is directly revealed and it was observed that by addition of 0.1% V the recrystallization was significantly retarded.

  16. Electron-electron scattering-induced channel hot electron injection in nanoscale n-channel metal-oxide-semiconductor field-effect-transistors with high-k/metal gate stacks

    International Nuclear Information System (INIS)

    Tsai, Jyun-Yu; Liu, Kuan-Ju; Lu, Ying-Hsin; Liu, Xi-Wen; Chang, Ting-Chang; Chen, Ching-En; Ho, Szu-Han; Tseng, Tseung-Yuen; Cheng, Osbert; Huang, Cheng-Tung; Lu, Ching-Sen

    2014-01-01

    This work investigates electron-electron scattering (EES)-induced channel hot electron (CHE) injection in nanoscale n-channel metal-oxide-semiconductor field-effect-transistors (n-MOSFETs) with high-k/metal gate stacks. Many groups have proposed new models (i.e., single-particle and multiple-particle process) to well explain the hot carrier degradation in nanoscale devices and all mechanisms focused on Si-H bond dissociation at the Si/SiO 2 interface. However, for high-k dielectric devices, experiment results show that the channel hot carrier trapping in the pre-existing high-k bulk defects is the main degradation mechanism. Therefore, we propose a model of EES-induced CHE injection to illustrate the trapping-dominant mechanism in nanoscale n-MOSFETs with high-k/metal gate stacks.

  17. Microbial ecology of two hot springs of Sikkim: Predominate population and geochemistry.

    Science.gov (United States)

    Najar, Ishfaq Nabi; Sherpa, Mingma Thundu; Das, Sayak; Das, Saurav; Thakur, Nagendra

    2018-10-01

    Northeastern regions of India are known for their floral and faunal biodiversity. Especially the state of Sikkim lies in the eastern Himalayan ecological hotspot region. The state harbors many sulfur rich hot springs which have therapeutic and spiritual values. However, these hot springs are yet to be explored for their microbial ecology. The development of neo generation techniques such as metagenomics has provided an opportunity for inclusive study of microbial community of different environment. The present study describes the microbial diversity in two hot springs of Sikkim that is Polok and Borong with the assist of culture dependent and culture independent approaches. The culture independent techniques used in this study were next generation sequencing (NGS) and Phospholipid Fatty Acid Analysis (PLFA). Having relatively distinct geochemistry both the hot springs are thermophilic environments with the temperature range of 50-77 °C and pH range of 5-8. Metagenomic data revealed the dominance of bacteria over archaea. The most abundant phyla were Proteobacteria and Bacteroidetes although other phyla were also present such as Acidobacteria, Nitrospirae, Firmicutes, Proteobacteria, Parcubacteria and Spirochaetes. The PLFA studies have shown the abundance of Gram Positive bacteria followed by Gram negative bacteria. The culture dependent technique was correlative with PLFA studies. Most abundant bacteria as isolated and identified were Gram-positive genus Geobacillus and Anoxybacillus. The genus Geobacillus has been reported for the first time in North-Eastern states of India. The Geobacillus species obtained from the concerned hot springs were Geobacillus toebii, Geobacillus lituanicus, Geobacillus Kaustophillus and the Anoxybacillus species includes Anoxybacillus gonensis and Anoxybacillus Caldiproteolyticus. The distribution of major genera and their statistical correlation analyses with the geochemistry of the springs predicted that the temperature, p

  18. A POPULATION OF VERY HOT SUPER-EARTHS IN MULTIPLE-PLANET SYSTEMS SHOULD BE UNCOVERED BY KEPLER

    International Nuclear Information System (INIS)

    Schlaufman, Kevin C.; Lin, D. N. C.; Ida, S.

    2010-01-01

    We simulate a Kepler-like observation of a theoretical exoplanet population and show that the observed orbital period distribution of the Kepler giant planet candidates is best matched by an average stellar specific dissipation function Q' * in the interval 10 6 ∼ * ∼ 7 . In that situation, the few super-Earths that are driven to orbital periods of P < 1 day by dynamical interactions in multiple-planet systems will survive tidal disruption for a significant fraction of the main-sequence lifetimes of their stellar hosts. Consequently, though these very hot super-Earths are not characteristic of the overall super-Earth population, their substantial transit probability implies that they should be significant contributors to the full super-Earth population uncovered by Kepler. As a result, the CoRoT-7 system may be the first representative of a population of very hot super-Earths that we suggest should be found in multiple-planet systems preferentially orbiting the least-dissipative stellar hosts in the Kepler sample.

  19. Micron-scale mapping of megagauss magnetic fields using optical polarimetry to probe hot electron transport in petawatt-class laser-solid interactions.

    Science.gov (United States)

    Chatterjee, Gourab; Singh, Prashant Kumar; Robinson, A P L; Blackman, D; Booth, N; Culfa, O; Dance, R J; Gizzi, L A; Gray, R J; Green, J S; Koester, P; Kumar, G Ravindra; Labate, L; Lad, Amit D; Lancaster, K L; Pasley, J; Woolsey, N C; Rajeev, P P

    2017-08-21

    The transport of hot, relativistic electrons produced by the interaction of an intense petawatt laser pulse with a solid has garnered interest due to its potential application in the development of innovative x-ray sources and ion-acceleration schemes. We report on spatially and temporally resolved measurements of megagauss magnetic fields at the rear of a 50-μm thick plastic target, irradiated by a multi-picosecond petawatt laser pulse at an incident intensity of ~10 20 W/cm 2 . The pump-probe polarimetric measurements with micron-scale spatial resolution reveal the dynamics of the magnetic fields generated by the hot electron distribution at the target rear. An annular magnetic field profile was observed ~5 ps after the interaction, indicating a relatively smooth hot electron distribution at the rear-side of the plastic target. This is contrary to previous time-integrated measurements, which infer that such targets will produce highly structured hot electron transport. We measured large-scale filamentation of the hot electron distribution at the target rear only at later time-scales of ~10 ps, resulting in a commensurate large-scale filamentation of the magnetic field profile. Three-dimensional hybrid simulations corroborate our experimental observations and demonstrate a beam-like hot electron transport at initial time-scales that may be attributed to the local resistivity profile at the target rear.

  20. The effect of different stabilizers on the thermostability of electron beam crosslinked polyethylene in hot water

    International Nuclear Information System (INIS)

    Hassanpour, S.; Khoylou, F.

    2003-01-01

    Plastic pipes owing to their flexibility, great lengths, easier handling and absence of corrosion have been used for hot-water installations. Crosslinked high-density polyethylene is one of the best materials, being used for this purpose. The useful lifetime of unstabilized polyethylene is predicted to vary from a few months in hot water (30-40 deg. C) to almost two years in cool water (0-10 deg. C). Polyethylene was mixed with different types of stabilizers, in order to increase its durability. The samples were irradiated at 100-150 kGy. The amount of gel fraction and the changes in mechanical properties were measured. Irradiated samples were immersed in hot water for 1000 h. The thermostability of the specimens and the existence of antioxidants were measured by the induction time technique using differential scanning calorimetry at different time intervals. Furthermore, the changes in chemical structure and mechanical properties of the samples during their immersion in hot water were determined

  1. Two-photon-induced hot-electron transfer to a single molecule in a scanning tunneling microscope

    International Nuclear Information System (INIS)

    Wu, S. W.; Ho, W.

    2010-01-01

    The junction of a scanning tunneling microscope (STM) operating in the tunneling regime was irradiated with femtosecond laser pulses. A photoexcited hot electron in the STM tip resonantly tunnels into an excited state of a single molecule on the surface, converting it from the neutral to the anion. The electron-transfer rate depends quadratically on the incident laser power, suggesting a two-photon excitation process. This nonlinear optical process is further confirmed by the polarization measurement. Spatial dependence of the electron-transfer rate exhibits atomic-scale variations. A two-pulse correlation experiment reveals the ultrafast dynamic nature of photoinduced charging process in the STM junction. Results from these experiments are important for understanding photoinduced interfacial charge transfer in many nanoscale inorganic-organic structures.

  2. Electron backscatter diffraction study of dislocation content of a macrozone in hot-rolled Ti-6Al-4V alloy

    International Nuclear Information System (INIS)

    Britton, T. Ben; Birosca, Soran; Preuss, Michael; Wilkinson, Angus J.

    2010-01-01

    We compare the dislocation substructure within macrozone and non-macrozone regions of hot-rolled Ti-6Al-4 V. Hough-based and cross-correlation-based analysis of electron backscatter diffraction (EBSD) patterns are used to establish the grain orientations and intra-granular misorientations, respectively. The set of geometrically necessary dislocations (GNDs) that support measured lattice curvatures and minimize the total GND line energy are calculated. The GND content in the macrozone is approximately twice that in the non-macrozone region, and GNDs are present at densities ∼10 times higher than GNDs.

  3. Proximity effect and hot-electron diffusion in Ag/Al2O3/Al tunnel junctions

    International Nuclear Information System (INIS)

    Netel, H.; Jochum, J.; Labov, S.E.; Mears, C.A.; Frank, M.; Chow, D.; Lindeman, M.A.; Hiller, L.J.

    1997-01-01

    We have fabricated Ag/Al 2 O 3 /Al tunnel junctions on Si substrates using a new process. This process was developed to fabricate superconducting tunnel junctions (STJs) on the surface of a superconductor. These junctions allow us to study the proximity effect of a superconducting Al film on a normal metal trapping layer. In addition, these devices allow us to measure the hot-electron diffusion constant using a single junction. Lastly these devices will help us optimize the design and fabrication of tunnel junctions on the surface of high-Z, ultra-pure superconducting crystals. 5 refs., 8 figs

  4. Phase-locking of a terahertz solid-state source using a superconducting hot-electron bolometer mixer

    International Nuclear Information System (INIS)

    Miao, W; Zhang, W; Zhou, K M; Li, S L; Zhang, K; Duan, W Y; Yao, Q J; Shi, S C

    2013-01-01

    We report on a scheme whereby the local-oscillator (LO) of a THz heterodyne receiver can be phase-locked by the mixer of the heterodyne receiver. This scheme is demonstrated for the phase-locking of an 847.6 GHz Gunn oscillator and multiplier chain combined source with a superconducting hot-electron bolometer (HEB) mixer. We show that with this technique the phase-locked beat signal can reach a signal-to-noise ratio higher than 70 dB in a resolution bandwidth (RBW) of 1 Hz. This phase-locking scheme should find good use in THz heterodyne spectrometers. (paper)

  5. Theory of hot electrons on the liquid 4He surface, 2

    International Nuclear Information System (INIS)

    Aoki, Takayuki; Saitoh, Motohiko

    1979-01-01

    Theoretical study is given of the high field transport of surface state electrons on the liquid 4 He. The explicit form of the electron distribution function is solved by the use of the Boltzmann transport equation where the electron-ripplon and electron-He gas interactions are considered as dominant scattering mechanisms, and the electron-electron interactions are completely neglected. Inter-subband and intra-subband transitions are treated equally. The S-shaped non-linear behaviors predicted to occur at low temperature region in the electron temperature approximation have been removed. Experimentally observed hysteresis, if any, in the widths of the plasmon resonance and cyclotron resonance may thus be attributed to the electron-electron interaction. (author)

  6. Effects of electron beam irradiation combined with hot water immersion treatment for shelf life extension of bananas

    International Nuclear Information System (INIS)

    Russly Abdul Rahman

    1996-01-01

    A study of the effects of minimal processing treatments, both individually or in combinations, was carried out in order to extend the shelf life and to improve the quality of bananas. Pre climacteric bananas at light full three-quarter grade, were either treated with hot water immersion for 1-30 min at 45-55 degree C, or irradiated with electron beams (2.0 MeV, Van de Graaff accelerator), to a dose of 0.1-1.5 kGy. All fruit was stored at 21 ± 1 degree C and relative humidity of 85-95 %. There was no significant delay in ripening of fruit treated with hot water immersion at the above temperatures. Some damage to fruit particularly peel scalding at ends occurred at the higher temperatures (>50 degree C). The 50 degree C, 5 minutes immersion was selected for further study. Irradiation to 0.1-0.3 kGy delayed the ripening (up to 3 days) without affecting fruit quality. Doses greater than 0.4 kGy resulted in extensive discoloration and fruit splitting. No significant differences could be detected organoleptically between bananas irradiated at 0.15 kGy and the control. Results of the physico-chemical attributes of the bananas were reported for fruits at colour stage 5 and after 10 and 15 days of storage. The combination treatment of hot water immersion and irradiation at the above settings further extended the shelf life of the banana fruits

  7. Lateral terahertz hot-electron bolometer based on an array of Sn nanothreads in GaAs

    Science.gov (United States)

    Ponomarev, D. S.; Lavrukhin, D. V.; Yachmenev, A. E.; Khabibullin, R. A.; Semenikhin, I. E.; Vyurkov, V. V.; Ryzhii, M.; Otsuji, T.; Ryzhii, V.

    2018-04-01

    We report on the proposal and the theoretical and experimental studies of the terahertz hot-electron bolometer (THz HEB) based on a gated GaAs structure like the field-effect transistor with the array of parallel Sn nanothreads (Sn-NTs). The operation of the HEB is associated with an increase in the density of the delocalized electrons due to their heating by the incoming THz radiation. The quantum and the classical device models were developed, the quantum one was based on the self-consistent solution of the Poisson and Schrödinger equations, the classical model involved the Poisson equation and density of states omitting quantization. We calculated the electron energy distributions in the channels formed around the Sn-NTs for different gate voltages and found the fraction of the delocalized electrons propagating across the energy barriers between the NTs. Since the fraction of the delocalized electrons strongly depends on the average electron energy (effective temperature), the proposed THz HEB can exhibit an elevated responsivity compared with the HEBs based on more standard heterostructures. Due to a substantial anisotropy of the device structure, the THz HEB may demonstrate a noticeable polarization selectivity of the response to the in-plane polarized THz radiation. The features of the THz HEB might be useful in their practical applications in biology, medicine and material science.

  8. Study of field induced hot-electron emission using the composite microemitters with varying dielectric layer thickness

    International Nuclear Information System (INIS)

    Mousa, M.S.

    1987-07-01

    The analysis of the measurements obtained from the of field emission of electrons from composite metal-insulator (M-I) micropoint cathodes, using the combination of a high resolution electron spectrometer and a field emission microscope, has been presented. Results obtained describe the reversible current-voltage characteristic, emission images and electron energy distribution measurements of both thin and the optimum thick coatings. The observed effects, e.g. the threshold switch-on phenomena and the field-dependence of the F.W.H.M. and energy shift of the electron spectra have been identified in terms of a field-induced hot-electron emission (FIHEE) mechanism resulting from field penetration in the insulating film where conducting channels are formed. The theoretical implications accounts for the channels field intensification mechanism and the conduction properties with applied field, and the F.W.H.M. dependence on electron temperature. The control of the emission process at low fields by the M-I contact junction and at high fields by the bulk properties of the insulator have also been accounted for. These experimental and theoretical findings have been shown to be consistent with recently published data on M-I microstructures on broad-area (BA) high-voltage electrodes. (author). 18 refs, 6 figs

  9. Electron cyclotron waves transmission: new approach for the characterization of electron distribution functions in Tokamak hot plasmas

    International Nuclear Information System (INIS)

    Michelot, Y.

    1995-10-01

    Fast electrons are one of the basic ingredients of plasma operations in many existing thermonuclear fusion research devices. However, the understanding of fast electrons dynamics during creation and sustainment of the superthermal electrons tail is far for being satisfactory. For this reason, the Electron Cyclotron Transmission (ECT) diagnostic was implemented on Tore Supra tokamak. It consists on a microwave transmission system installed on a vertical chord crossing the plasma center and working in the frequency range 77-109 GHz. Variations of the wave amplitude during the propagation across the plasma may be due to refraction and resonant absorption. For the ECT, the most common manifestation of refraction is a reduction of the received power density with respect to the signal detected in vacuum, due to the spreading and deflection of the wave beam. Wave absorption is observed in the vicinity of the electron cyclotron harmonics and may be due both to thermal plasma and to superthermal electron tails. It has a characteristic frequency dependence due to the relativistic mass variation in the wave-electron resonance condition. This thesis presents the first measurements of: the extraordinary mode optical depth at the third harmonics, the electron temperature from the width of a cyclotron absorption line and the relaxation times of the electron distribution during lower hybrid current drive from the ordinary mode spectral superthermal absorption line at the first harmonic. (J.S.). 175 refs., 110 figs., 9 tabs., 3 annexes

  10. Theoretical predictions for the polarization of the J = 0 - 1 neonlike germanium X-ray laser line in the presence of a directed beam of hot electrons

    International Nuclear Information System (INIS)

    Inal, M.K.; Dubau, J.; Cornille, M.

    1998-01-01

    The polarization of the neonlike germanium J = 0 - 1 laser line, which would arise from the existence of a directed beam of hot electrons in the amplifying plasma, is theoretically investigated. The relative populations of the magnetic sublevels in the lower J = 1 laser level have been determined by allowing for the processes of direct excitation from the 2p 6 ground level and collisional de-excitation from the upper J = 0 laser level. Elastic collisions leading to transitions between the M J = 0 and M J =1 sublevels within the lower level of the lasing line have also been taken into account. The required elastic and inelastic collision strengths for transitions between magnetic sublevels have been computed in a semi-relativistic distorted-wave approximation, for incident electron energies up to 15 keV. Our calculations predict a rather low degree of polarization for the J = 0 - 1 line, although the elastic collisions are found to play a negligibly small role in the redistribution of magnetic sublevel populations. (author)

  11. Hot phonon generation by split-off hole band electrons in AlxGa1-xAs alloys investigated by picosecond Raman scattering

    International Nuclear Information System (INIS)

    Jacob, J.M.; Kim, D.S.; Zhou, J.F.; Song, J.J.

    1992-01-01

    The initial generation of hot LO phonons by the relaxation of hot carriers in GaAs and Al x Ga 1-x As alloy semiconductors is studied. Within the initial 2ps of photoexcitation, only those electrons originating from the split-off hole bands are found to generate a significant number of I-valley hot phonons when photon energies of 2.33eV are used. A picosecond Raman scattering technique is used to determine the hot phonon occupation number in a series of MBE grown Al x Ga 1-x As samples with 0≤x≤0.39. The Stokes and anti-Stokes lines were measured for both GaAs-like and AlAs-like LO phonon modes to determine their occupation numbers. The authors observe a rapid decrease in the phonon occupation numbers as the aluminum concentration increases beyond x = 0.2. This rapid decrease is explained by considering only those electrons photoexcited from the split-off hole band. Almost all of the electrons originating from the heavy and light-hole bands are shown to quickly transfer and remain in the X and L valleys without generating significant numbers of hot LO phonons during the initial 2ps and at a carrier density of 10 17 cm -3 . A model based upon the instantaneous thermalization of hot electrons photoexcited from the split-off hole bands is used to fit the data. They have obtained very good agreement between experiment and theory. This work provides a clear understanding to the relaxation of Γ valley hot electrons by the generation of hot phonons on subpicosecond and picosecond time scales, which has long standing implications to previous time resolved Raman experiments

  12. Non-Fourier Heat Transfer with Phonons and Electrons in a Circular Thin Layer Surrounding a Hot Nanodevice

    Directory of Open Access Journals (Sweden)

    Vito Antonio Cimmelli

    2015-07-01

    Full Text Available A nonlocal model for heat transfer with phonons and electrons is applied to infer the steady-state radial temperature profile in a circular layer surrounding an inner hot component. Such a profile, following by the numerical solution of the heat equation, predicts that the temperature behaves in an anomalous way, since for radial distances from the heat source smaller than the mean-free path of phonons and electrons, it increases for increasing distances. The compatibility of this temperature behavior with the second law of thermodynamics is investigated by calculating numerically the local entropy production as a function of the radial distance. It turns out that such a production is positive and strictly decreasing with the radial distance.

  13. The role of the Milky Way hot coronal gas on its dwarf galaxies stellar population

    Science.gov (United States)

    Pasetto, Stefano; Cropper, Mark; fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

    2015-08-01

    A large amount (˜5 ×1010 Msun) of hot gas is thought to exist in an extended (˜200 kpc) hot diffuse halo around the Milky Way (MW). We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation history of gravitationally bound system in this external environment. Ram pressure, Kelvin-Helmholtz instability, Rayleigh-Taylor, and tidal forces are accounted separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment useful in observational applications as well as theoretical interpretations of numerical results.We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance.The theoretical framework developed has direct applications to the cases of our MW system as well as dwarf galaxies in galaxy clusters or any primordial gas-rich cluster of stars orbiting within its host galaxy.

  14. Energy relaxation and separation of a hot electron-hole pair in organic aggregates from a time-dependent wavepacket diffusion method

    International Nuclear Information System (INIS)

    Han, Lu; Liang, WanZhen; Zhao, Yi; Zhong, Xinxin

    2014-01-01

    The time-dependent wavepacket diffusive method [X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013)] is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling. The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with a central momentum. The results reveal that the hot electron energy relaxation is very well described by two rate processes with the fast rate much larger than the slow one, consistent with experimental observations, and an efficient electron-hole separation is accomplished accompanying the fast energy relaxation. Furthermore, although the extra energy indeed helps the separation by overcoming the Coulomb interaction, the width of initial wavepacket is much sensitive to the separation efficiency and the narrower wavepacket generates the more separated charges. This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation

  15. Distinguishing of Ile/Leu amino acid residues in the PP3 protein by (hot) electron capture dissociation in Fourier transform ion cyclotron resonance mass spectrometry

    DEFF Research Database (Denmark)

    Kjeldsen, Frank; Haselmann, Kim F; Sørensen, Esben Skipper

    2003-01-01

    In hot electron capture dissociation (HECD), multiply protonated polypeptides fragment upon capturing approximately 11-eV electrons. The excess of energy upon the primary c, z* cleavage induces secondary fragmentation in z* fragments. The resultant w ions allow one to distinguish between the isom...

  16. Technique for measuring hot plsma electron temperture by soft X-ray spectra with increased resolution

    International Nuclear Information System (INIS)

    Gulyaev, V.A.; Kabanovskij, S.V.; Lyadina, E.S.

    1985-01-01

    Ways of improving time resolution of amplitude spectrometers used for diagnostics of hot plasma in tokamaks are discussed. The circuit of an analog-to-digital processor for processing signals coming from detectors is suggested. The converter comprises 8 similar channels each of them including an input shaper, differential discriminator with a wide energy band; fast shaper with shaping time of 0.1-0.2 μs, analog delay circuit, linear transmission circuit, control device, slow shaping circuit, differential discriminator with a narrow energy band, digital intensimeter. Model test of the described channel is conducted; it confirmed correctness of the applied method

  17. A spatial analysis of population dynamics and climate change in Africa: potential vulnerability hot spots emerge where precipitation declines and demographic pressures coincide

    Science.gov (United States)

    López-Carr, David; Pricope, Narcisa G.; Aukema, Juliann E.; Jankowska, Marta M.; Funk, Christopher C.; Husak, Gregory J.; Michaelsen, Joel C.

    2014-01-01

    We present an integrative measure of exposure and sensitivity components of vulnerability to climatic and demographic change for the African continent in order to identify “hot spots” of high potential population vulnerability. Getis-Ord Gi* spatial clustering analyses reveal statistically significant locations of spatio-temporal precipitation decline coinciding with high population density and increase. Statistically significant areas are evident, particularly across central, southern, and eastern Africa. The highly populated Lake Victoria basin emerges as a particularly salient hot spot. People located in the regions highlighted in this analysis suffer exceptionally high exposure to negative climate change impacts (as populations increase on lands with decreasing rainfall). Results may help inform further hot spot mapping and related research on demographic vulnerabilities to climate change. Results may also inform more suitable geographical targeting of policy interventions across the continent.

  18. THERMAL RESPONSE OF A SOLAR-LIKE ATMOSPHERE TO AN ELECTRON BEAM FROM A HOT JUPITER: A NUMERICAL EXPERIMENT

    International Nuclear Information System (INIS)

    Gu, P.-G.; Suzuki, Takeru K.

    2009-01-01

    We investigate the thermal response of the atmosphere of a solar-type star to an electron beam injected from a hot Jupiter by performing a one-dimensional MHD numerical experiment with nonlinear wave dissipation, radiative cooling, and thermal conduction. In our experiment, the stellar atmosphere is non-rotating and is modeled as a one-dimensional open flux tube expanding super-radially from the stellar photosphere to the planet. An electron beam is assumed to be generated from the reconnection site of the planet's magnetosphere. The effects of the electron beam are then implemented in our simulation as dissipation of the beam momentum and energy at the base of the corona where the Coulomb collisions become effective. When the sufficient energy is supplied by the electron beam, a warm region forms in the chromosphere. This warm region greatly enhances the radiative fluxes corresponding to the temperature of the chromosphere and transition region. The warm region can also intermittently contribute to the radiative flux associated with the coronal temperature due to the thermal instability. However, owing to the small area of the heating spot, the total luminosity of the beam-induced chromospheric radiation is several orders of magnitude smaller than the observed Ca II emissions from HD 179949.

  19. Ultrafast Phase Transition in Vanadium Dioxide Driven by Hot-Electron Injection

    Directory of Open Access Journals (Sweden)

    Prasankumar R. P.

    2013-03-01

    Full Text Available We present a novel all-optical method of triggering the phase transition in vanadium dioxide by means of ballistic electrons injected across the interface between a mesh of Au nanoparticles coveringd VO2 nanoislands. By performing non-degenerate pump-probe transmission spectroscopy on this hybrid plasmonic/phase-changing nanostructure, structural and electronic dynamics can be retrieved and compared.

  20. Room Temperature Deposition Processes Mediated By Ultrafast Photo-Excited Hot Electrons

    Science.gov (United States)

    2014-01-30

    mechanical through resonant energy transfer. The average electron temperature (Tel) during τ2 evolves as energy is lost through optical and acoustic ...through ballistic collisions and acoustic phonons. The large difference in heat capacities between electrons and the substrate leads to negligible...temperature pyrometer indicated only a ~30oC temperature gradient between the thermocouple location and the topside of the sample which faced the

  1. Hard x-ray (>100 keV) imager to measure hot electron preheat for indirectly driven capsule implosions on the NIF.

    Science.gov (United States)

    Döppner, T; Dewald, E L; Divol, L; Thomas, C A; Burns, S; Celliers, P M; Izumi, N; Kline, J L; LaCaille, G; McNaney, J M; Prasad, R R; Robey, H F; Glenzer, S H; Landen, O L

    2012-10-01

    We have fielded a hard x-ray (>100 keV) imager with high aspect ratio pinholes to measure the spatially resolved bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. These electrons are generated in laser plasma interactions and are a source of preheat to the deuterium-tritium fuel. First measurements show that hot electron preheat does not limit obtaining the fuel areal densities required for ignition and burn.

  2. A Practitioner's Guide to Electronic Cigarettes in the Adolescent Population.

    Science.gov (United States)

    Hildick-Smith, Gordon J; Pesko, Michael F; Shearer, Lee; Hughes, Jenna M; Chang, Jane; Loughlin, Gerald M; Ipp, Lisa S

    2015-12-01

    We present guidance on electronic nicotine delivery systems (ENDS) for health care professionals who care for adolescents. ENDS provide users with inhaled nicotine in an aerosolized mist. Popular forms of ENDS include e-cigarettes and vape-pens. ENDS range in disposability, customization, and price. Growth of ENDS usage has been particularly rapid in the adolescent population, surpassing that of conventional cigarettes in 2014. Despite surging use throughout the United States, little is known about the health risks posed by ENDS, especially in the vulnerable adolescent population. These products may potentiate nicotine addiction in adolescents and have been found to contain potentially harmful chemicals. The growth in these products may be driven by relaxed purchasing restrictions for minors, lack of advertising regulations, and youth friendly flavors. Taken together, ENDS represent a new and growing health risk to the adolescent population, one that health care professionals should address with their patients. We suggest a patient centered strategy to incorporate ENDS use into routine substance counseling. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  3. Trapping in GaN-based metal-insulator-semiconductor transistors: Role of high drain bias and hot electrons

    Energy Technology Data Exchange (ETDEWEB)

    Meneghini, M., E-mail: matteo.meneghini@dei.unipd.it; Bisi, D.; Meneghesso, G.; Zanoni, E. [Department of Information Engineering, University of Padova, via Gradenigo 6/B, 35131 Padova (Italy); Marcon, D.; Stoffels, S.; Van Hove, M.; Wu, T.-L.; Decoutere, S. [IMEC, Kapeldreef 75, 3001 Heverlee (Belgium)

    2014-04-07

    This paper describes an extensive analysis of the role of off-state and semi-on state bias in inducing the trapping in GaN-based power High Electron Mobility Transistors. The study is based on combined pulsed characterization and on-resistance transient measurements. We demonstrate that—by changing the quiescent bias point from the off-state to the semi-on state—it is possible to separately analyze two relevant trapping mechanisms: (i) the trapping of electrons in the gate-drain access region, activated by the exposure to high drain bias in the off-state; (ii) the trapping of hot-electrons within the AlGaN barrier or the gate insulator, which occurs when the devices are operated in the semi-on state. The dependence of these two mechanisms on the bias conditions and on temperature, and the properties (activation energy and cross section) of the related traps are described in the text.

  4. Design of all-optical, hot-electron current-direction-switching device based on geometrical asymmetry.

    Science.gov (United States)

    Kumarasinghe, Chathurangi S; Premaratne, Malin; Gunapala, Sarath D; Agrawal, Govind P

    2016-02-18

    We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors.

  5. The Skyrme-TQRPA calculations of electron capture on hot nuclei in pre-supernova environment

    Energy Technology Data Exchange (ETDEWEB)

    Dzhioev, Alan A., E-mail: dzhioev@theor.jinr.ru; Vdovin, A. I., E-mail: vdovin@theor.jinr.ru [JINR, Bogoliubov Laboratory of Theoretical Physics (Russian Federation); Stoyanov, Ch., E-mail: stoyanov@inrne.bas.bg [Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy (Bulgaria)

    2016-11-15

    We combine the thermal QRPA approach with the Skyrme energy density functional theory (Skyrme–TQRPA) for modelling the process of electron capture on nuclei in supernova environment. For a sample nucleus, {sup 56}Fe, the Skyrme–TQRPA approach is applied to analyze thermal effects on the strength function of GT{sub +} transitions which dominate electron capture at E{sub e} ≤ 30 MeV. Several Skyrme interactions are used in order to verify the sensitivity of the obtained results to the Skyrme force parameters. Finite-temperature cross sections are calculated and the results are comparedwith those of the other model calculations.

  6. College's hot topics? Wildfire and Hazards' risk perception among university's population

    Science.gov (United States)

    Wuerzer, T.

    2014-12-01

    This research presents a novel perspective on college students and their risk perception in a fire prone US State; Idaho. Idaho was "top #1" in burned lands by acreage in 2012 with approximate 15% of all US burned lands; in 2013 "top #2". Past studies have conducted surveys on residents in high wildfire risk communities to learn what factors make homeowners more likely to engage in mitigation activities and therefore increase communities' resiliency. This research emphasis is on a population that deals with the threat of fire but is likely less invested through property ownership and other investment of risk; yet, equally threatened in quality of life. Are college students the left-out population in the 'planning for wildfires' and its communication process? Main hypothesis is that a college population will have a different perception and awareness (and therefore mitigation actions) than i.e. residents invested in the wild land urban interface (WUI). Dominant research methodologies in past studies are identified as surveys, focus groups, or interviews focusing on homeowners in fire prone areas that have witnessed wildfire or are exposed to increasing fire risk. Yet again, research on population that has no property ownership, investments at stake, and therefore no direct monetary values associated (but potentially non-monetary), is found little to none in these studies. The university population based study and its findings offers a contrast to current literature related to these traditional residents surveys/interviews. The study's survey and interactive spatial assessment of risk perception with allocation of perceived hazards zones promotes understanding of where risk is apparent for participants. Results are used to inform agencies such as campus emergency management, regional wild fire mitigation efforts, and to enhance public communication. Lessons learned include the challenges of a comprehensive inclusion process when mitigating for hazards and building

  7. Experimental Route to Scanning Probe Hot Electron Nanoscopy (HENs) Applied to 2D Material

    KAUST Repository

    Giugni, Andrea; Torre, Bruno; Allione, Marco; Das, Gobind; Wang, Zhenwei; He, Xin; Alshareef, Husam N.; Di Fabrizio, Enzo M.

    2017-01-01

    for applications in electronics: 2D MoS2 single crystal and a p-type SnO layer. Results are supported by complementary scanning Kelvin probe microscopy, traditional conductive AFM, and Raman measurements. New features highlighted by HEN technique reveal details

  8. Hot electrons and the approach to metallic behavior in Kx(KCl)1-x

    NARCIS (Netherlands)

    Silvestrelli, P.L.; Alavi, A.; Parrinello, M.; Frenkel, D.

    1996-01-01

    The approach to the metallic phase of molten Kx(KCl)1-x mixtures is studied using ab initio molecular dynamics based on finite-temperature density functional theory. The finite electronic temperature is found to result in new and unexpected effects. In particular, we observe a thermally induced

  9. Hot-electron-mediated desorption rates calculated from excited-state potential energy surfaces

    DEFF Research Database (Denmark)

    Olsen, Thomas; Gavnholt, Jeppe; Schiøtz, Jakob

    2009-01-01

    We present a model for desorption induced by (multiple) electronic transitions [DIET (DIMET)] based on potential energy surfaces calculated with the delta self-consistent field extension of density-functional theory. We calculate potential energy surfaces of CO and NO molecules adsorbed on variou...

  10. Confinement of hot, hard x-ray producing electrons in solar flares

    International Nuclear Information System (INIS)

    Smith, D.F.; Lilliequist, C.G.

    1979-01-01

    Possible thermal models for solar, hard X-ray emission, consisting of small volumes in which the electrons are rapidly heated to 4 x 10 8 K, are examined to determine under what conditions such models can be more efficient than nonthermal models. The primary energy-loss mechanism in these models is source expansion due to heat conduction which deviates from its classical value by mechanisms which are reviewed and systematized. One such mechanism is saturation of the heat flux at its maximum possible value, corresponding to direct convection by electrons. Another mechanism is anomalous limitation of the heat flux due to instability of the return current which must compensate the electron current carrying the heat. A simple, one-dimensional model in which a section of the flux tube of constant density is heated to 4 x 10 8 K is analyzed. A conduction front, determined by the above collisionless process, moves along the flux tube at the head of the expanding source. A more realistic, one-dimensional, one-fluid, two-temperature model with a spatially and temporally varying energy source which delivers energy to the electrons at a finite rate is formulated and solved numerically. This results in some ion heating and mass motions which, by themselves, represent only a small energy loss. However, because of changes in the anomalous limitation of the heat flux with higher ion temperature, the expansion losses increase considerably

  11. Generation and confinement of hot ions and electrons in a reversed-field pinch plasma

    International Nuclear Information System (INIS)

    Chapman, B E; Almagri, A F; Anderson, J K; Caspary, K J; Clayton, D J; Den Hartog, D J; Ennis, D A; Fiksel, G; Gangadhara, S; Kumar, S; Magee, R M; O'Connell, R; Parke, E; Prager, S C; Reusch, J A; Sarff, J S; Stephens, H D; Brower, D L; Ding, W X; Craig, D

    2010-01-01

    By manipulating magnetic reconnection in Madison Symmetric Torus (MST) discharges, we have generated and confined for the first time a reversed-field pinch (RFP) plasma with an ion temperature >1 keV and an electron temperature of 2 keV. This is achieved at a toroidal plasma current of about 0.5 MA, approaching MST's present maximum. The manipulation begins with intensification of discrete magnetic reconnection events, causing the ion temperature to increase to several kiloelectronvolts. The reconnection is then quickly suppressed with inductive current profile control, leading to capture of a portion of the added ion heat with improved ion energy confinement. Electron energy confinement is simultaneously improved, leading to a rapid ohmically driven increase in the electron temperature. A steep electron temperature gradient emerges in the outer region of the plasma, with a local thermal diffusivity of about 2 m 2 s -1 . The global energy confinement time reaches 12 ms, the largest value yet achieved in the RFP and which is roughly comparable to the H-mode scaling prediction for a tokamak with the same plasma current, density, heating power, size and shape.

  12. Optimum launching of electron-cyclotron power for localized current drive in a hot tokamak

    International Nuclear Information System (INIS)

    Smith, G.R.

    1989-05-01

    Optimum launch parameters are determined for localized electron-cyclotron current drive near the magnetic axis and the q=2 surface by solving several minimization problems. For central current drive, equatorial and bottom launch are compared. Localized current drive near q=2 is studied for equatorial launch and for an alternative outside launch geometry that may be better for suppressing tearing modes and controlling disruptions. 6 refs., 2 figs

  13. Hot-electron-assisted femtochemistry at surfaces: A time-dependent density functional theory approach

    DEFF Research Database (Denmark)

    Gavnholt, Jeppe; Rubio, Angel; Olsen, Thomas

    2009-01-01

    Using time-evolution time-dependent density functional theory (TDDFT) within the adiabatic local-density approximation, we study the interactions between single electrons and molecular resonances at surfaces. Our system is a nitrogen molecule adsorbed on a ruthenium surface. The surface is modele...... resonance and the lowering of the resonance energy due to an image charge effect. Finally we apply the TDDFT procedure to only consider the decay of molecular excitations and find that it agrees quite well with the width of the projected density of Kohn-Sham states....

  14. Hot electron-induced electrochemiluminescence at polyetherimide-carbon black-based electrodes

    International Nuclear Information System (INIS)

    Salminen, Kalle; Grönroos, Päivi; Johansson, Leena-Sisko; Campbell, Joseph; Kulmala, Sakari

    2017-01-01

    Highlights: • Generation of hydrated electrons at carbon paste electrodes. • Hydrated electrons are able to produce intense chemiluminescence. • Relationship between carbon black content in electrode and HECL studied. • Performance of composite electrodes is similar to aluminum electrodes. • The present electrodes are good alternative for disposable assay cartridges. - Abstract: Various luminophores produce strong electrogenerated chemiluminescence during cathodic pulse polarization of the present insulating film-covered carbon paste electrodes in fully aqueous solutions. First electrodes made of a commercial conductive carbon paste were successfully utilized as working electrodes and their surface was characterized by ESCA. Then custom in-laboratory made improved composite electrodes were manufactured from the same insulating polymer and conducting carbon black particles. The relationship between the amount of carbon present on the composite electrode, in the bulk and on the surface, and the intensity of electrogenerated chemiluminescence was studied further. The overall performance of these composite electrodes makes them viable low-cost replacements for metal/insulator type electrodes such as oxide-coated silicon electrodes.

  15. Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

    Directory of Open Access Journals (Sweden)

    Kai Braun

    2015-05-01

    Full Text Available Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode into the highest occupied orbital of the closest substrate-bound molecule (lower level and radiative recombination with an electron from above the Fermi level (upper level, hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode.

  16. Density and field effect on electron-ion collision cross-sections in hot dense plasma

    International Nuclear Information System (INIS)

    Gaufridy de Dortan, F. de

    2003-03-01

    Collisional excitation cross-sections are essential for the modeling of the properties of non equilibrium plasmas. There has been a lot of work on electron impact excitation of isolated ions, but in dense plasmas, neighboring particles are expected to widely disturb these electron transitions in atoms. Plasma modeling through a radially perturbed potential has already been done but is not satisfactory as it does not account for levels degeneracy breaking and its consequences. Introduction of a quasistatic electric micro-field of neighboring ions allows us to break spherical symmetry. Our original theoretical study has given birth to a numerical code that accurately computes collisional strengths and rates (in the Distorted Waves approach) in atoms submitted to a realistic micro-field. Hydrogen- and helium-like aluminium is studied. Stark mixing widely increases rates of transitions from high l levels and forbidden transitions are field-enhanced by many orders of magnitude until they reach allowed ones. Eventually, we conduct an elementary stationary collisional radiative study to investigate field-enhancement effects on corresponding line shapes. In cases we study (aluminium, hydrogen- and helium-like) we find a relatively weak increase of K-shell line broadening

  17. Numerical fluid solutions for nonlocal electron transport in hot plasmas: Equivalent diffusion versus nonlocal source

    International Nuclear Information System (INIS)

    Colombant, Denis; Manheimer, Wallace

    2010-01-01

    Flux limitation and preheat are important processes in electron transport occurring in laser produced plasmas. The proper calculation of both of these has been a subject receiving much attention over the entire lifetime of the laser fusion project. Where nonlocal transport (instead of simple single flux limit) has been modeled, it has always been with what we denote the equivalent diffusion solution, namely treating the transport as only a diffusion process. We introduce here a new approach called the nonlocal source solution and show it is numerically viable for laser produced plasmas. It turns out that the equivalent diffusion solution generally underestimates preheat. Furthermore, the advance of the temperature front, and especially the preheat, can be held up by artificial 'thermal barriers'. The nonlocal source method of solution, on the other hand more accurately describes preheat and can stably calculate the solution for the temperature even if the heat flux is up the gradient.

  18. Quantum corrected Langevin dynamics for adsorbates on metal surfaces interacting with hot electrons

    DEFF Research Database (Denmark)

    Olsen, Thomas; Schiøtz, Jakob

    2010-01-01

    We investigate the importance of including quantized initial conditions in Langevin dynamics for adsorbates interacting with a thermal reservoir of electrons. For quadratic potentials the time evolution is exactly described by a classical Langevin equation and it is shown how to rigorously obtain...... quantum mechanical probabilities from the classical phase space distributions resulting from the dynamics. At short time scales, classical and quasiclassical initial conditions lead to wrong results and only correctly quantized initial conditions give a close agreement with an inherently quantum...... mechanical master equation approach. With CO on Cu(100) as an example, we demonstrate the effect for a system with ab initio frictional tensor and potential energy surfaces and show that quantizing the initial conditions can have a large impact on both the desorption probability and the distribution...

  19. Study of hot carrier relaxation in quantum wells by subpicosecond Raman scattering

    International Nuclear Information System (INIS)

    Kim, Dai-sik; Yu, P.Y.

    1990-03-01

    Relaxation of hot carriers excited by subpicosecond laser pulses has been studied by Raman scattering in GaAs/AlAs multiple quantum wells with well widths varying between 100 and 1000 Angstrom. The hot phonon population observed by Raman scattering is found to decrease with the well width despite the fact that the hot electron temperature remains constant. The results are explained in terms of confinement of both electrons and optical phonons in quantum wells

  20. Electrically excited hot-electron dominated fluorescent emitters using individual Ga-doped ZnO microwires via metal quasiparticle film decoration.

    Science.gov (United States)

    Liu, Yang; Jiang, Mingming; Zhang, Zhenzhong; Li, Binghui; Zhao, Haifeng; Shan, Chongxin; Shen, Dezhen

    2018-03-28

    The generation of hot electrons from metal nanostructures through plasmon decay provided a direct interfacial charge transfer mechanism, which no longer suffers from the barrier height restrictions observed for metal/semiconductor interfaces. Metal plasmon-mediated energy conversion with higher efficiency has been proposed as a promising alternative to construct novel optoelectronic devices, such as photodetectors, photovoltaic and photocatalytic devices, etc. However, the realization of the electrically-driven generation of hot electrons, and the application in light-emitting devices remain big challenges. Here, hybrid architectures comprising individual Ga-doped ZnO (ZnO:Ga) microwires via metal quasiparticle film decoration were fabricated. The hottest spots could be formed towards the center of the wires, and the quasiparticle films were converted into physically isolated nanoparticles by applying a bias onto the wires. Thus, the hot electrons became spatially localized towards the hottest regions, leading to a release of energy in the form of emitting photons. By adjusting the sputtering times and appropriate alloys, such as Au and Ag, wavelength-tunable emissions could be achieved. To exploit the EL emission characteristics, metal plasmons could be used as active elements to mediate the generation of hot electrons from metal nanostructures, which are located in the light-emitting regions, followed by injection into ZnO:Ga microwire-channels; thus, the production of plasmon decay-induced hot-electrons could function as an efficient approach to dominate emission wavelengths. Therefore, by introducing metal nanostructure decoration, individual ZnO:Ga microwires can be used to construct wavelength-tunable fluorescent emitters. The hybrid architectures of metal-ZnO micro/nanostructures offer a fantastic candidate to broaden the potential applications of semiconducting optoelectronic devices, such as photovoltaic devices, photodetectors, optoelectronic sensors, etc.

  1. Nicotine and Cotinine Exposure from Electronic Cigarettes: A Population Approach

    Science.gov (United States)

    de Mendizábal, Nieves Vélez; Jones, David R.; Jahn, Andy; Bies, Robert R.; Brown, Joshua W.

    2015-01-01

    Background and Objectives Electronic cigarettes (e-cigarettes) are a recent technology that has gained rapid acceptance. Still, little is known about them in terms of safety and effectiveness. A basic question is how effectively they deliver nicotine, however the literature is surprisingly unclear on this point. Here, a population pharmacokinetic (PK) model was developed for nicotine and its major metabolite cotinine with the aim to provide a reliable framework for the simulation of nicotine and cotinine concentrations over time, based solely on inhalation airflow recordings and individual covariates (i.e. weight and breath carbon monoxide CO levels). Methods This study included 10 adults self-identified as heavy smokers (at least one pack per day). Plasma nicotine and cotinine concentrations were measured at regular 10-minute intervals for 90 minutes while human subjects inhaled nicotine vapor from a modified e-cigarette. Airflow measurements were recorded every 200 milliseconds throughout the session. A population PK model for nicotine and cotinine was developed based on previously published PK parameters and the airflow recordings. All the analyses were performed with the nonlinear mixed-effect modelling software NONMEM 7.2. Results The results show that e-cigarettes deliver nicotine effectively, although the pharmacokinetic profiles are lower than those achieved with regular cigarettes. Our PK model effectively predicts plasma nicotine and cotinine concentrations from the inhalation volume, and initial breath CO. Conclusion E-cigarettes are effective at delivering nicotine. This new PK model of e-cigarette usage might be used for pharmacodynamic analysis where the PK profiles are not available. PMID:25503588

  2. Reduction of adhesive stain defect in flexible printed circuit board on hot pressing process: A case study of electronic component factory

    Directory of Open Access Journals (Sweden)

    Sakulkaew Srisang

    2015-03-01

    Full Text Available The objective of this research is a reduction of an adhesive stain defect in flexible printed circuit board in hot pressing process, the electronic factory. The manufacturing have been processing by sheet type of products with ninety-six pieces of flexible printed circuit boards. Causes of the problem include the before and internal hot pressing process. In process beginning times, the most right row of products between the cooling plate and the hot pressing machine has temperature 71.2◦C that is higher than glass transition temperature (Tg 60◦C. Those products’ temperature lead to evaporate a polyimide adhesive before hot pressing process beginning. The internal hot pressing process include the preheat times and the pressure time. In the preheat time the problem is a gap between lower and upper plate, was under specification (Under 1 mm and leaded to adhesive polyimide stain. In the actuality this time requires temperature and low pressure that mean a gap within 1 – 2 mm (between lower and upper plate. In pressure times the hot pressing plate surface is not flat and products are pressed by insufficient force that it lead to generate an adhesive stain on flexible printed circuit boards. That force is measured by the pre-scale paper and a result, RGB color, is provided. And then color density (From standard color sample and RGB color (From pre-scale paper is found out the relation by Photoshop program and multiple regression theory using. The formula is applied to compare with defect so as to find out the suitable color density (Defects reducing. The solving solutions is provided including the gap reduced adjustment between cooling plate and hot pressing machine before hot pressing process, the plate adjustment within specification in the preheat time and the pressing plate polishing in the pressure time. Results of study and solving are provide defect reduction from 24.4 percentage to 7.2 percentage of total study product.

  3. Possibilities and prospects of investigation of irradiated structural and fuel materials using scanning electron microscope PHILLIPS XL 30 ESEM-TMP installed in the hot cell

    International Nuclear Information System (INIS)

    Golovanov, V. N.; Novoselov, A.E.; Kuzmin, S.V.; Yakovlev, V. V.

    2005-01-01

    Scanning electron microscope Philips XL 30 ESEM - TMP with X-ray microanalysis system INCA has been installed at SSC RF RIAR. The microscope is placed in the hot cell. Monitoring and control system is installed in the operator's room. Irradiated specimens are supplied to the hot cell through the transport terminal and installed into the microscope by manipulators. Direct contact of the personnel with radioactive materials is impossible. In addition it is developed the system of remote placement of the irradiated specimens into the specimen chamber of microscope. The system includes a stage with three seats, holders for different types of specimens and equipment for their remote loading in the holders. (Author)

  4. Change On The S-Z Effect Induced By The Cooling Flow CF On The Hot Electronic Gas At The Center OF The Clusters Of Galaxies

    Directory of Open Access Journals (Sweden)

    Enkelejd Caca

    2015-06-01

    Full Text Available ABSTRACT Building more accurate profiles for temperature and density of hot electronic gas concentrated in the center of clusters of galaxies is a constant problem in survey of Sunyeav Zeldovich effect SZ. An effect that consists in the inverse Compton effect of the hot electronic gas interacting with Cosmic Microwave Back- ground CMB photons passing through Intra Cluster Medium ICM. So far the Isothermal model is used for temperature profiling in the calculation of the inverse Compton effect but based on the recent improved observations from satellites which showed that the hot electronic gas presents a feature called Cooling Flow CF. Temperatures in this model differs towards the edges of the Clusters of Galaxies leading to a change on the Compton parameter in comparison with Isothermal model. In this paper are processed data provided by X-ray satellite Chandra. The X-ray analysis is based on two models for the electron density and temperature profile. A sample of 12 clusters of galaxies are analyzed and by building the temperature profiles using CF model the differences on the Compton parameter are 10-100 in comparison with Isothermal model. Therefore to increase the accuracy of evaluation of the Compton parameter we should take into account the change of the electronic gas tempera- ture change that affect changes in both CMB spectrum and temperature from SZ effect.

  5. Photoprompted Hot Electrons from Bulk Cross-Linked Graphene Materials and Their Efficient Catalysis for Atmospheric Ammonia Synthesis.

    Science.gov (United States)

    Lu, Yanhong; Yang, Yang; Zhang, Tengfei; Ge, Zhen; Chang, Huicong; Xiao, Peishuang; Xie, Yuanyuan; Hua, Lei; Li, Qingyun; Li, Haiyang; Ma, Bo; Guan, Naijia; Ma, Yanfeng; Chen, Yongsheng

    2016-11-22

    Ammonia synthesis is the single most important chemical process in industry and has used the successful heterogeneous Haber-Bosch catalyst for over 100 years and requires processing under both high temperature (300-500 °C) and pressure (200-300 atm); thus, it has huge energy costs accounting for about 1-3% of human's energy consumption. Therefore, there has been a long and vigorous exploration to find a milder alternative process. Here, we demonstrate that by using an iron- and graphene-based catalyst, Fe@3DGraphene, hot (ejected) electrons from this composite catalyst induced by visible light in a wide range of wavelength up to red could efficiently facilitate the activation of N 2 and generate ammonia with H 2 directly at ambient pressure using light (including simulated sun light) illumination directly. No external voltage or electrochemical or any other agent is needed. The production rate increases with increasing light frequency under the same power and with increasing power under the same frequency. The mechanism is confirmed by the detection of the intermediate N 2 H 4 and also with a measured apparent activation energy only ∼1/4 of the iron based Haber-Bosch catalyst. Combined with the morphology control using alumina as the structural promoter, the catalyst retains its activity in a 50 h test.

  6. Contribution to the modelling and multi-scale numerical simulation of kinetic electron transport in hot plasma

    International Nuclear Information System (INIS)

    Mallet, J.

    2012-01-01

    This research thesis stands at the crossroad of plasma physics, numerical analysis and applied mathematics. After an introduction presenting the problematic and previous works, the author recalls some basis of classical kinetic models for plasma physics (collisionless kinetic theory and Vlasov equation, collisional kinetic theory with the non-relativistic Maxwell-Fokker-Plansk system) and describes the fundamental properties of the collision operators such as conservation laws, entropy dissipation, and so on. He reports the improvement of a deterministic numerical method to solve the non-relativistic Vlasov-Maxwell system coupled with Fokker-Planck-Landau type operators. The efficiency of each high order scheme is compared. The evolution of the hot spot is studied in the case of thermonuclear reactions in the centre of the pellet in a weakly collisional regime. The author focuses on the simulation of the kinetic electron collisional transport in inertial confinement fusion (ICF) between the laser absorption zone and the ablation front. A new approach is then introduced to reduce the huge computation time obtained with kinetic models. In a last chapter, the kinetic continuous equation in spherical domain is described and a new model is chosen for collisions in order to preserve collision properties

  7. Immunoassay of C-reactive protein by hot electron induced electrochemiluminescence using integrated electrodes with hydrophobic sample confinement

    Energy Technology Data Exchange (ETDEWEB)

    Ylinen-Hinkka, T., E-mail: tiina.ylinen-hinkka@aalto.fi [Laboratory of Analytical Chemistry, Aalto University School of Chemical Technology, P.O. Box 16100, FI-00076 Aalto (Finland); Niskanen, A.J.; Franssila, S. [Department of Materials Science and Engineering, Aalto University School of Chemical Technology, P.O. Box 16200, FI-00076 Aalto (Finland); Kulmala, S. [Laboratory of Analytical Chemistry, Aalto University School of Chemical Technology, P.O. Box 16100, FI-00076 Aalto (Finland)

    2011-09-19

    Highlights: {center_dot} C-reactive protein has been determined in the concentration range 0.01-10 mg L{sup -1} using an electrochemiluminescence microchip which employs integrated electrodes with hydrophobic sample confinement. {center_dot} This arrangement enables very simple and fast CRP analysis amenable to point-of-care applications. - Abstract: C-reactive protein (CRP) was determined in the concentration range 0.01-10 mg L{sup -1} using hot electron induced electrochemiluminescence (HECL) with devices combining both working and counter electrodes and sample confinement on a single chip. The sample area on the electrodes was defined by a hydrophobic ring, which enabled dispensing the reagents and the analyte directly on the electrode. Immunoassay of CRP by HECL using integrated electrodes is a good candidate for a high-sensitivity point-of-care CRP-test, because the concentration range is suitable, miniaturisation of the measurement system has been demonstrated and the assay method with integrated electrodes is easy to use. High-sensitivity CRP tests can be used to monitor the current state of cardiovascular disease and also to predict future cardiovascular problems in apparently healthy people.

  8. Experimental study of hot electrons propagation and energy deposition in solid or laser-shock compressed targets: applications to fast igniter

    International Nuclear Information System (INIS)

    Pisani, F.

    2000-02-01

    In the fast igniter scheme, a recent approach proposed for the inertial confinement fusion, the idea is to dissociate the fuel ignition phase from its compression. The ignition phase would be then achieved by means of an external energy source: a fast electron beam generated by the interaction with an ultra-intense laser. The main goal of this work is to study the mechanisms of the hot electron energy transfer to the compressed fuel. We intent in particular to study the role of the electric and collisional effects involved in the hot electron propagation in a medium with properties similar to the compressed fuel. We carried out two experiments, one at the Vulcan laser facility (England) and the second one at the new LULI 100 TW laser (France). During the first experiment, we obtained the first results on the hot electron propagation in a dense and hot plasma. The innovating aspect of this work was in particular the use of the laser-shock technique to generate high pressures, allowing the strongly correlated and degenerated plasma to be created. The role of the electric and magnetic effects due to the space charge associated with the fast electron beam has been investigated in the second experiment. Here we studied the propagation in materials with different electrical characteristics: an insulator and a conductor. The analysis of the results showed that only by taking into account simultaneously the two propagation mechanisms (collisions and electric effects) a correct treatment of the energy deposition is possible. We also showed the importance of taking into account the induced modifications due to the electrons beam crossing the target, especially the induced heating. (author)

  9. Quasilinear dynamics of a cloud of hot electrons propagating through a plasma with decreasing density and temperature

    International Nuclear Information System (INIS)

    Foroutan, G.; Khalilpour, H.; Moslehi-Fard, M.; Li, B.; Robinson, P. A.

    2008-01-01

    The effects of plasma inhomogeneities on the propagation of a cloud of hot electrons through a cold background plasma and generation of Langmuir waves are investigated using numerical simulations of the quasilinear equations. It is found that in a plasma with decreasing density the quasilinear relaxation of the electron distribution in velocity space is accelerated and the levels of the generated Langmuir waves are enhanced. The magnitude of the induced emission rate is increased and its maximum value moves to lower velocities. Due to density gradient the height of plateau shows an increase at small distances and a corresponding decrease at large distances. It is also found that in a plasma with decreasing temperature, the relaxation of the beam is retarded, the spectral density of Langmuir waves is broadened, and the height of the plateau decreases below its value in a uniform plasma. In the presence of both density and temperature gradients, at given position, the height and upper boundary of the plateau and the level of Langmuir waves are all increased at small velocities. The spatial expansion of the beam is increased by the plasma inhomogeneities, but its average velocity of propagation decreases. Initially, at a given position, the velocity at the upper boundary of the plateau is smaller in the presence of the density gradient than in the uniform plasma but the reverse is true at longer times. Due to temperature gradient, at large times and small distances, the upper boundary of the plateau is increased above its value in the uniform plasma. Because of fast relaxation, the value of the lower boundary of the plateau in the plasma with decreasing density is always less than its value in the uniform plasma. It is found that the local velocity of the beam decreases when the density gradient is present. The local velocity spread of the beam remains unchanged during the propagation of the beam in the uniform plasma, but increases in the presence of inhomogeneities.

  10. Radiation belt seed population and its association with the relativistic electron dynamics: A statistical study: Radiation Belt Seed Population

    International Nuclear Information System (INIS)

    Tang, C. L.; Wang, Y. X.; Ni, B.; Zhang, J.-C.

    2017-01-01

    Using the Van Allen Probes data, we study the radiation belt seed population and it associated with the relativistic electron dynamics during 74 geomagnetic storm events. Based on the flux changes of 1 MeV electrons before and after the storm peak, these storm events are divided into two groups of “non-preconditioned” and “preconditioned”. The statistical study shows that the storm intensity is of significant importance for the distribution of the seed population (336 keV electrons) in the outer radiation belt. However, substorm intensity can also be important to the evolution of the seed population for some geomagnetic storm events. For non-preconditioned storm events, the correlation between the peak fluxes and their L-shell locations of the seed population and relativistic electrons (592 keV, 1.0 MeV, 1.8 MeV, and 2.1 MeV) is consistent with the energy-dependent dynamic processes in the outer radiation belt. For preconditioned storm events, the correlation between the features of the seed population and relativistic electrons is not fully consistent with the energy-dependent processes. It is suggested that the good correlation between the radiation belt seed population and ≤1.0 MeV electrons contributes to the prediction of the evolution of ≤1.0 MeV electrons in the Earth’s outer radiation belt during periods of geomagnetic storms.

  11. Natural variations in the geomagnetically trapped electron population

    Science.gov (United States)

    Vampola, A. L.

    1972-01-01

    Temporal variations in the trapped natural electron flux intensities and energy spectra are discussed and demonstrated using recent satellite data. These data are intended to acquaint the space systems engineer with the types of natural variations that may be encountered during a mission and to augment the models of the electron environment currently being used in space system design and orbit selection. An understanding of the temporal variations which may be encountered should prove helpful. Some of the variations demonstrated here which are not widely known include: (1) addition of very energetic electrons to the outer zone during moderate magnetic storms: (2) addition of energetic electrons to the inner zone during major magnetic storms; (3) inversions in the outer zone electron energy spectrum during the decay phase of a storm injection event and (4) occasional formation of multiple maxima in the flux vs altitude profile of moderately energetic electrons.

  12. Theoretical study of atomic structure of Zpopulations in a hot plasma and population inversions

    International Nuclear Information System (INIS)

    Guennou, Helene.

    1983-05-01

    This thesis presents a theoretical method for atomic-structure calculations (energy levels, wave functions, oscillator strengths): it is a modified Hartree-Fock method including the spin-orbit interaction in the variationnal process. Two applications are first described: one concerning the resonance lines of the Krypton isoelectronic sequence, the other having for purpose the interpretation of Lsub(α) and Lsub(β) satellites in Copper. A description is made of an original collisional-radiative model, which makes use of the preceding method, and allows to calculate the populations of a great number of ionic excited levels in a plasma. This model is used in a detailed study of the Al 10+ Lithium -like ion spectrum. It is able to explain the apparition of inversion populations for some special electronic densities and temperatures, for example between the levels corresponding to the transitions observed at 103.8, 105.7 and 154.7 A [fr

  13. Hot Flashes

    Science.gov (United States)

    Hot flashes Overview Hot flashes are sudden feelings of warmth, which are usually most intense over the face, neck and chest. Your skin might redden, as if you're blushing. Hot flashes can also cause sweating, and if you ...

  14. The impact of electronic cigarettes on the paediatric population

    OpenAIRE

    Durmowicz, Elizabeth L

    2014-01-01

    Objective To review the impact of electronic cigarettes (e-cigarettes) on children. Methods Five electronic databases were searched through 31 December 2013. Studies in English that included data for children younger than 18 years of age were included. In addition, relevant data from articles identified during searches of the e-cigarette literature, relevant state survey data and paediatric voluntary adverse event reports submitted to the US Food and Drug Administration (FDA) were reviewed an...

  15. Predicting hot spots in protein interfaces based on protrusion index, pseudo hydrophobicity and electron-ion interaction pseudopotential features

    Science.gov (United States)

    Xia, Junfeng; Yue, Zhenyu; Di, Yunqiang; Zhu, Xiaolei; Zheng, Chun-Hou

    2016-01-01

    The identification of hot spots, a small subset of protein interfaces that accounts for the majority of binding free energy, is becoming more important for the research of drug design and cancer development. Based on our previous methods (APIS and KFC2), here we proposed a novel hot spot prediction method. For each hot spot residue, we firstly constructed a wide variety of 108 sequence, structural, and neighborhood features to characterize potential hot spot residues, including conventional ones and new one (pseudo hydrophobicity) exploited in this study. We then selected 3 top-ranking features that contribute the most in the classification by a two-step feature selection process consisting of minimal-redundancy-maximal-relevance algorithm and an exhaustive search method. We used support vector machines to build our final prediction model. When testing our model on an independent test set, our method showed the highest F1-score of 0.70 and MCC of 0.46 comparing with the existing state-of-the-art hot spot prediction methods. Our results indicate that these features are more effective than the conventional features considered previously, and that the combination of our and traditional features may support the creation of a discriminative feature set for efficient prediction of hot spots in protein interfaces. PMID:26934646

  16. HOT 2015

    DEFF Research Database (Denmark)

    Hannibal, Sara Stefansen

    2016-01-01

    HOT samler og formidler 21 literacykyndiges bud på, hvad der er hot, og hvad der bør være hot inden for literacy – og deres begrundelser for disse bud.......HOT samler og formidler 21 literacykyndiges bud på, hvad der er hot, og hvad der bør være hot inden for literacy – og deres begrundelser for disse bud....

  17. Reduction of adhesive stain defect in flexible printed circuit board on hot pressing process: a case study of electronic component factory

    Directory of Open Access Journals (Sweden)

    Sakulkaew Srisang

    2014-09-01

    Full Text Available The objective of this research is a reduction of an adhesive stain defect in flexible printed circuit board in hot pressing process, the electronic factory. The manufacturing have been processing by sheet type of products with ninety-six pieces of flexible printed circuit boards. Causes of the problem include the before and internal hot pressing process. In process beginning times, the most right row of products between the cooling plate and the hot pressing machine has temperature 71.2◦C that is higher than glass transition temperature (Tg 60◦C. Those products’ temperature lead to evaporate a polyimide adhesive before hot pressing process beginning. The internal hot pressing process include the preheat times and the pressure time. In the preheat time the problem is a gap between lower and upper plate, was under specification(Under 1 mm and leaded to adhesive polyimide stain. In the actuality this time requires temperature and low pressure that mean a gap within 1 – 2 mm (between lower and upper plate. In pressure times the hot pressing plate surface is not flat and products are pressed by insufficient force that it lead to generate an adhesive stain on flexible printed circuit boards. That force is measured by the pre-scale paper and a result, RGB color, is provided. And then color density (From standard color sample and RGB color (From pre-scale paper is found out the relation by Photoshop program and multiple regression theory using. The formula is applied to compare with defect so as to find out the suitable color density (Defects reducing. The solving solutions is provided including the gap reduced adjustment between cooling plate and hot pressing machine before hot pressing process, the plate adjustment within specification in the preheat time and the pressing plate polishing in the pressure time. Results of study and solving are provide defect reduction from 24.4 percentage to 7.2 percentage of total study product.

  18. Effect of hot air drying on volatile compounds of Flammulina velutipes detected by HS-SPME-GC-MS and electronic nose.

    Science.gov (United States)

    Yang, Wenjian; Yu, Jie; Pei, Fei; Mariga, Alfred Mugambi; Ma, Ning; Fang, Yong; Hu, Qiuhui

    2016-04-01

    Volatile compounds are important factors that affect the flavor quality of Flammulina velutipes, but the changes occurring during hot air drying is still unclear. To clarify the dynamic changes of flavor components during hot air drying, comprehensive flavor characterization and volatile compounds of F. velutipes were evaluated using electronic nose technology and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. Results showed that volatile components in F. velutipes significantly changed during hot air drying according to the principal component analysis and radar fingerprint chart of electronic nose. Volatile compounds of fresh F. velutipes consisted mainly of ketones, aldehydes and alcohols, and 3-octanone was the dominant compound. Drying process could significantly decrease the relative content of ketones and promoted the generation of alcohols, acids, and esters, which became the main volatile compounds of dried F. velutipes. These may provide a theoretical basis for the formation mechanism of flavor substances in dried F. velutipes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. The Challenges of Electronic Health Records and Diabetes Electronic Prescribing: Implications for Safety Net Care for Diverse Populations

    Directory of Open Access Journals (Sweden)

    Neda Ratanawongsa

    2017-01-01

    Full Text Available Widespread electronic health record (EHR implementation creates new challenges in the diabetes care of complex and diverse populations, including safe medication prescribing for patients with limited health literacy and limited English proficiency. This review highlights how the EHR electronic prescribing transformation has affected diabetes care for vulnerable patients and offers recommendations for improving patient safety through EHR electronic prescribing design, implementation, policy, and research. Specifically, we present evidence for (1 the adoption of RxNorm; (2 standardized naming and picklist options for high alert medications such as insulin; (3 the widespread implementation of universal medication schedule and language-concordant labels, with the expansion of electronic prescription 140-character limit; (4 enhanced bidirectional communication with pharmacy partners; and (5 informatics and implementation research in safety net healthcare systems to examine how EHR tools and practices affect diverse vulnerable populations.

  20. Hot rolling and annealing effects on the microstructure and mechanical properties of ODS austenitic steel fabricated by electron beam selective melting

    Science.gov (United States)

    Gao, Rui; Ge, Wen-jun; Miao, Shu; Zhang, Tao; Wang, Xian-ping; Fang, Qian-feng

    2016-03-01

    The grain morphology, nano-oxide particles and mechanical properties of oxide dispersion strengthened (ODS)-316L austenitic steel synthesized by electron beam selective melting (EBSM) technique with different post-working processes, were explored in this study. The ODS-316L austenitic steel with superfine nano-sized oxide particles of 30-40 nm exhibits good tensile strength (412 MPa) and large total elongation (about 51%) due to the pinning effect of uniform distributed oxide particles on dislocations. After hot rolling, the specimen exhibits a higher tensile strength of 482 MPa, but the elongation decreases to 31.8% owing to the introduction of high-density dislocations. The subsequent heat treatment eliminates the grain defects induced by hot rolling and increases the randomly orientated grains, which further improves the strength and ductility of EBSM ODS-316L steel.

  1. The magic of nanoplasmonics: from superhydrophobic and 3D suspended devices for SERS/TERS-like applications to hot-electrons based nanoscopy

    KAUST Repository

    Alabastri, A.

    2014-05-02

    The ability to confine light in small volumes, associated to low background signals, is an important technological achievement for a number of disciplines such as biology or electronics. In fact, decoupling the source position from the sample area allows an unprecedented sensitivity which can be exploited in different systems. The most direct implications are however related to either Surface Enhanced Raman Scattering (SERS) or Tip Enhanced Raman Scattering (TERS). Furthermore, while the combination with super-hydrophobic patterns can overcome the typical diffusion limit of sensors, focused surface plasmons decaying into hot electrons can be exploited to study the electronic properties of the sample by means of a Schottky junction. Within this paper these techniques will be briefly described and the key role played by both surface and localized plasmons will be highlighted. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  2. The magic of nanoplasmonics: from superhydrophobic and 3D suspended devices for SERS/TERS-like applications to hot-electrons based nanoscopy

    KAUST Repository

    Alabastri, A.; Toma, A.; Giugni, A.; Torre, B.; Malerba, M.; Miele, E.; De Angelis, F.; Liberale, Carlo; Das, Gobind; Di Fabrizio, Enzo M.; Proietti Zaccaria, R.

    2014-01-01

    The ability to confine light in small volumes, associated to low background signals, is an important technological achievement for a number of disciplines such as biology or electronics. In fact, decoupling the source position from the sample area allows an unprecedented sensitivity which can be exploited in different systems. The most direct implications are however related to either Surface Enhanced Raman Scattering (SERS) or Tip Enhanced Raman Scattering (TERS). Furthermore, while the combination with super-hydrophobic patterns can overcome the typical diffusion limit of sensors, focused surface plasmons decaying into hot electrons can be exploited to study the electronic properties of the sample by means of a Schottky junction. Within this paper these techniques will be briefly described and the key role played by both surface and localized plasmons will be highlighted. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  3. Illicit Drug Users in the Tanzanian Hinterland: Population Size Estimation Through Key Informant-Driven Hot Spot Mapping.

    Science.gov (United States)

    Ndayongeje, Joel; Msami, Amani; Laurent, Yovin Ivo; Mwankemwa, Syangu; Makumbuli, Moza; Ngonyani, Alois M; Tiberio, Jenny; Welty, Susie; Said, Christen; Morris, Meghan D; McFarland, Willi

    2018-02-12

    We mapped hot spots and estimated the numbers of people who use drugs (PWUD) and who inject drugs (PWID) in 12 regions of Tanzania. Primary (ie, current and past PWUD) and secondary (eg, police, service providers) key informants identified potential hot spots, which we visited to verify and count the number of PWUD and PWID present. Adjustments to counts and extrapolation to regional estimates were done by local experts through iterative rounds of discussion. Drug use, specifically cocaine and heroin, occurred in all regions. Tanga had the largest numbers of PWUD and PWID (5190 and 540, respectively), followed by Mwanza (3300 and 300, respectively). Findings highlight the need to strengthen awareness of drug use and develop prevention and harm reduction programs with broader reach in Tanzania. This exercise provides a foundation for understanding the extent and locations of drug use, a baseline for future size estimations, and a sampling frame for future research.

  4. The impact of electronic cigarettes on the paediatric population.

    Science.gov (United States)

    Durmowicz, Elizabeth L

    2014-05-01

    To review the impact of electronic cigarettes (e-cigarettes) on children. Five electronic databases were searched through 31 December 2013. Studies in English that included data for children younger than 18 years of age were included. In addition, relevant data from articles identified during searches of the e-cigarette literature, relevant state survey data and paediatric voluntary adverse event reports submitted to the US Food and Drug Administration (FDA) were reviewed and included. Use of e-cigarettes by youth is increasing and is not limited to traditional cigarette smokers. Data regarding the reasons for youth e-cigarette initiation and ongoing use are limited. The effects of e-cigarette marketing and the availability of flavoured e-liquids on youth use are unknown. The abuse liability of e-cigarettes in youth is also not known. Unintentional exposures to e-cigarettes and e-liquids have been reported in children. The number of e-cigarette-related reports received by poison centres is increasing. No data are available on secondhand and thirdhand e-cigarette aerosol exposures in children. Data on the impact of e-cigarettes on children are extremely limited. The available data indicate that youth awareness is high and use is increasing rapidly. The extent to which e-cigarette use in youth will result in nicotine dependence and subsequent use of other tobacco products is unknown. e-cigarettes present risks of unintentional nicotine exposure and are potential choking hazards. A greater understanding of the impact of e-cigarettes on children is needed and will be important in the evaluation of the effects of these products on the public health.

  5. Hot electron emission can lead to damping of optomechanical modes in core-shell Ag@TiO2 nanocubes

    DEFF Research Database (Denmark)

    Tamulevičius, Sigitas; Peckus, Domantas; Rong, Hongpan

    2017-01-01

    Interactions between light and metal nanostructures are mediated by collective excitations of free electrons called surface plasmons, which depend primarily on geometry and dielectric environment. Excitation with ultrafast pulses can excite optomechanical modes that modulate the volume and shape...... resonance is being lost to the TiO2 as hot carriers instead of coupling to the optomechanical mode. Analysis of both ultrafast decay and characterization of optomechanical modes provides a dual accounting method to track energy dissipation in hybrid metal-semiconductor nanosystems for plasmon-enhanced solar...

  6. Two-dimensional simulations of laser–plasma interaction and hot electron generation in the context of shock-ignition research

    Czech Academy of Sciences Publication Activity Database

    Klimo, O.; Psikal, J.; Tikhonchuk, V.T.; Weber, Stefan A.

    2014-01-01

    Roč. 56, č. 5 (2014), 055010 ISSN 0741-3335 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk EE2.3.20.0279 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; LaserZdroj (OP VK 3)(XE) CZ.1.07/2.3.00/20.0279 Institutional support: RVO:68378271 Keywords : laser plasma interaction * stimulated Raman scattering * hot electrons * particle-in-cell simulation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.186, year: 2014

  7. Shaping the solar wind electron temperature anisotropy by the interplay of core and suprathermal populations

    Science.gov (United States)

    Shaaban Hamd, S. M.; Lazar, M.; Poedts, S.; Pierrard, V.; Štverák

    2017-12-01

    We present the results of an advanced parametrization of the temperature anisotropy of electrons in the slow solar wind and the electromagnetic instabilities resulting from the interplay of their thermal core and suprathermal halo populations. A large set of observational data (from the Ulysses, Helios and Cluster missions) is used to parametrize these components and establish their correlations. Comparative analysis demonstrates for the first time a particular implication of the suprathermal electrons which are less dense but hotter than thermal electrons. The instabilities are significantly stimulated by the interplay of the core and halo populations, leading to lower thresholds which shape the observed limits of the temperature anisotropy for both the core and halo populations. This double agreement strongly suggests that the selfgenerated instabilities play the major role in constraining the electron anisotropy.

  8. Comparison of hot and cold spell effects on cardiovascular mortality in individual population groups in the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Kyselý, Jan; Plavcová, Eva; Davídkovová, Hana; Kynčl, J.

    2011-01-01

    Roč. 49, č. 2 (2011), s. 113-129 ISSN 0936-577X R&D Projects: GA ČR(CZ) GAP209/11/1985 Institutional research plan: CEZ:AV0Z30420517; CEZ:AV0Z30120515 Keywords : Human mortality * Cardiovascular diseases * Temperature extremes * Hot spells * Cold spells * Central Europe Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.994, year: 2011 http://www.int-res.com/articles/cr_oa/c049p113.pdf

  9. Ensemble Monte Carlo particle investigation of hot electron induced source-drain burnout characteristics of GaAs field-effect transistors

    Science.gov (United States)

    Moglestue, C.; Buot, F. A.; Anderson, W. T.

    1995-08-01

    The lattice heating rate has been calculated for GaAs field-effect transistors of different source-drain channel design by means of the ensemble Monte Carlo particle model. Transport of carriers in the substrate and the presence of free surface charges are also included in our simulation. The actual heat generation was obtained by accounting for the energy exchanged with the lattice of the semiconductor during phonon scattering. It was found that the maximum heating rate takes place below the surface near the drain end of the gate. The results correlate well with a previous hydrodynamic energy transport estimate of the electronic energy density, but shifted slightly more towards the drain. These results further emphasize the adverse effects of hot electrons on the Ohmic contacts.

  10. Freezing hot electrons. Electron transfer and solvation dynamics at D{sub 2}O and NH{sub 3}-metal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Staehler, A.J.

    2007-05-15

    The present work investigates the electron transfer and solvation dynamics at the D{sub 2}O/Cu(111), D{sub 2}O/Ru(001), and NH{sub 3}/Cu(111) interfaces using femtosecond time-resolved two-photon photoelectron spectroscopy. Within this framework, the influence of the substrate, adsorbate structure and morphology, solvation site, coverage, temperature, and solvent on the electron dynamics are studied, yielding microscopic insight into the underlying fundamental processes. Transitions between different regimes of ET, substrate-dominated, barrier-determined, strong, and weak coupling are observed by systematic variation of the interfacial properties and development of empirical model descriptions. It is shown that the fundamental steps of the interfacial electron dynamics are similar for all investigated systems: Metal electrons are photoexcited to unoccupied metal states and transferred into the adlayer via the adsorbate's conduction band. The electrons localize at favorable sites and are stabilized by reorientations of the surrounding polar solvent molecules. Concurrently, they decay back two the metal substrate, as it offers a continuum of unoccupied states. However, the detailed characteristics vary for the different investigated interfaces: For amorphous ice-metal interfaces, the electron transfer is initially, right after photoinjection, dominated by the substrate's electronic surface band structure. With increasing solvation, a transient barrier evolves at the interface that increasingly screens the electrons from the substrate. Tunneling through this barrier becomes the rate-limiting step for ET. The competition of electron decay and solvation leads to lifetimes of the solvated electrons in the order of 100 fs. Furthermore, it is shown that the electrons bind in the bulk of the ice layers, but on the edges of adsorbed D{sub 2}O clusters and that the ice morphology strongly influences the electron dynamics. For the amorphous NH{sub 3}/Cu(111

  11. HOT 2012

    DEFF Research Database (Denmark)

    Lund, Henriette Romme

    Undersøgelse af, hvad der er hot - og hvad der burde være hot på læseområdet med 21 læsekyndige. Undersøgelsen er gennemført siden 2010. HOT-undersøgelsen er foretaget af Nationalt Videncenter for Læsning - Professionshøjskolerne i samarb. med Dansklærerforeningen......Undersøgelse af, hvad der er hot - og hvad der burde være hot på læseområdet med 21 læsekyndige. Undersøgelsen er gennemført siden 2010. HOT-undersøgelsen er foretaget af Nationalt Videncenter for Læsning - Professionshøjskolerne i samarb. med Dansklærerforeningen...

  12. HOT 2014

    DEFF Research Database (Denmark)

    Lund, Henriette

    Undersøgelse af, hvad der er hot - og hvad der burde være hot på læseområdet med 21 læsekyndige. Undersøgelsen er gennemført siden 2010. HOT-undersøgelsen er foretaget af Nationalt Videncenter for Læsning - Professionshøjskolerne i samarb. med Dansklærerforeningen...

  13. HOT 2011

    DEFF Research Database (Denmark)

    Lund, Henriette Romme

    En undersøgelse af, hvad der er hot - og burde være hot på læseområdet. I undersøgelsen deltager 21 læsekyndige fra praksisfeltet, professionshøjskolerne og forskningsområdet.......En undersøgelse af, hvad der er hot - og burde være hot på læseområdet. I undersøgelsen deltager 21 læsekyndige fra praksisfeltet, professionshøjskolerne og forskningsområdet....

  14. Noise temperature of an NbN hot-electron bolometric mixer at frequencies from 0.7 THz to 5.2 THz

    International Nuclear Information System (INIS)

    Schubert, J.; Semenov, A.; Gol'tsman, G.; Huebers, H-W.; Voronov, B.; Gershenzon, E.; Schwaab, G.

    1999-01-01

    We report on noise temperature measurements of an NbN phonon-cooled hot-electron bolometric mixer in the terahertz frequency range. The devices were 3 nm thick films with in-plane dimensions 1.7x0.2μm 2 and 0.9x0.2μm 2 integrated in a complementary logarithmic-spiral antenna. Measurements were performed at seven frequencies ranging from 0.7 THz to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz) and 8800 K (5.2 THz). (author)

  15. Warm and hot electron distribution in the inner magnetosphere and the plasmasheet region related to the magnetospheric indices and the solar wind parameters: a statistical study form the NOAA POES TED and MEPED data

    Science.gov (United States)

    Boscher, Daniel; Rochel Grimald, Sandrine

    2013-04-01

    Using DMSP satellites, low altitude measurements has demonstrated to give a good picture of the plasmasheet population. The NOAA POES satellites are a constellation of five spacecraft orbiting in a polar orbit between 800 and 850 km and covering a wide L-shell range. They provide fourteen years of data without interruption which allow to make statistical study of the inner magnetosphere and the plasmasheet population. Moreover, since 2002, three of the NOAA POES satellites are located at different local times allowing to deduce the plasmasheet properties, even for huge magnetic activity. This paper present a statistical study of the warm and hot electron density over an energy range [0.16 ; 300] keV and between 1 and 12 Re. We present here maps in Mac Ilwain L paramater / MLT and we use the magnetic indices and solar wind parameter to classify our observations. The results show a clear motion of the plasmapause when Kp increase, which is in agreement with previous results, but it also show changes of the plasmapause shape and strong density variations in the night side sector. Moreover, a clear link between the solar wind parameters, in particular Bz, and the density distribution has been established. Unexpected distributions have been observed in the dayside and will be discussed here.

  16. Assessment of PCBs and exposure risk to infants in breast milk of primiparae and multiparae mothers in an electronic waste hot spot and non-hot spot areas in Ghana.

    Science.gov (United States)

    Asamoah, Anita; Essumang, David Kofi; Muff, Jens; Kucheryavskiy, Sergey V; Søgaard, Erik Gydesen

    2018-01-15

    The aim of the study was to assess the levels of PCBs in the breast milk of some Ghanaian women at suspected hotspot and relatively non-hotspot areas and to find out if the levels of these PCBs pose any risk to the breastfed infants. A total of 128 individual human breast milk were sampled from both primiparae and multiparae mothers. The levels of PCBs in the milk samples were compared. Some of these mothers (105 individuals) work or reside in and around Agbogbloshie (hot-spot), the largest electric and electronic waste dump and recycling site in Accra, Ghana. Others (23 donor mothers) also reside in and around Kwabenya (non-hotspot) which is a mainly residential area without any industrial activities. Samples were analyzed using GC-MS/MS. The total mean levels and range of Σ 7 PCBs were 3.64ng/glipidwt and ˂LOD-29.20ng/glipidwt, respectively. Mean concentrations from Agbogbloshie (hot-spot area) and Kwabenya (non-hotspot areas) were 4.43ng/glipidwt and 0.03ng/glipidwt, respectively. PCB-28 contributed the highest of 29.5% of the total PCBs in the milk samples, and PCB-101 contributed the lowest of 1.74%. The estimated daily intake of PCBs and total PCBs concentrations in this work were found to be lower as compared to similar studies across the world. The estimated hazard quotient using Health Canada's guidelines threshold limit of 1μg/kgbw/day showed no potential health risk to babies. However, considering minimum tolerable value of 0.03μg/kgbw/day defined by the Agency for Toxic Substances and Disease Registry (ATSDR), the values of some mothers were found to be at the threshold limit. This may indicate a potential health risk to their babies. Mothers with values at the threshold levels of the minimum tolerable limits are those who work or reside in and around the Agbogbloshie e-waste site. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Large Reduction of Hot Spot Temperature in Graphene Electronic Devices with Heat-Spreading Hexagonal Boron Nitride.

    Science.gov (United States)

    Choi, David; Poudel, Nirakar; Park, Saungeun; Akinwande, Deji; Cronin, Stephen B; Watanabe, Kenji; Taniguchi, Takashi; Yao, Zhen; Shi, Li

    2018-04-04

    Scanning thermal microscopy measurements reveal a significant thermal benefit of including a high thermal conductivity hexagonal boron nitride (h-BN) heat-spreading layer between graphene and either a SiO 2 /Si substrate or a 100 μm thick Corning flexible Willow glass (WG) substrate. At the same power density, an 80 nm thick h-BN layer on the silicon substrate can yield a factor of 2.2 reduction of the hot spot temperature, whereas a 35 nm thick h-BN layer on the WG substrate is sufficient to obtain a factor of 4.1 reduction. The larger effect of the h-BN heat spreader on WG than on SiO 2 /Si is attributed to a smaller effective heat transfer coefficient per unit area for three-dimensional heat conduction into the thick, low-thermal conductivity WG substrate than for one-dimensional heat conduction through the thin oxide layer on silicon. Consequently, the h-BN lateral heat-spreading length is much larger on WG than on SiO 2 /Si, resulting in a larger degree of temperature reduction.

  18. Amplification of radiation near cyclotron frequency due to electron population inversion

    International Nuclear Information System (INIS)

    Lee, L.C.; Wu, C.S.

    1980-01-01

    Amplification of electromagnetic waves via the cyclotron maser mechanism by a population of weakly relativistic electrons is studied. The effect of a tenuous population of low energy background plasma is included. It is found that both the ordinary and extraordinary modes can be excited by the weakly relativistic electrons with a loss-cone distribution. The growth rate for the extraordinary mode is much higher than that for the ordinary mode. Velocity spread in the energetic electron distribution function may reduce the growth rate by a factor of approximately 10 from that in the monoenergetic case. The maximum growth rate for the fast extraordinary mode (X mode) occurs near the upper hybrid cutoff frequency. Numerical results are obtained and discussed

  19. Predicting Electron Population Characteristics in 2-D Using Multispectral Ground-Based Imaging

    Science.gov (United States)

    Grubbs, Guy; Michell, Robert; Samara, Marilia; Hampton, Donald; Jahn, Jorg-Micha

    2018-01-01

    Ground-based imaging and in situ sounding rocket data are compared to electron transport modeling for an active inverted-V type auroral event. The Ground-to-Rocket Electrodynamics-Electrons Correlative Experiment (GREECE) mission successfully launched from Poker Flat, Alaska, on 3 March 2014 at 11:09:50 UT and reached an apogee of approximately 335 km over the aurora. Multiple ground-based electron-multiplying charge-coupled device (EMCCD) imagers were positioned at Venetie, Alaska, and aimed toward magnetic zenith. The imagers observed the intensity of different auroral emission lines (427.8, 557.7, and 844.6 nm) at the magnetic foot point of the rocket payload. Emission line intensity data are correlated with electron characteristics measured by the GREECE onboard electron spectrometer. A modified version of the GLobal airglOW (GLOW) model is used to estimate precipitating electron characteristics based on optical emissions. GLOW predicted the electron population characteristics with 20% error given the observed spectral intensities within 10° of magnetic zenith. Predictions are within 30% of the actual values within 20° of magnetic zenith for inverted-V-type aurora. Therefore, it is argued that this technique can be used, at least in certain types of aurora, such as the inverted-V type presented here, to derive 2-D maps of electron characteristics. These can then be used to further derive 2-D maps of ionospheric parameters as a function of time, based solely on multispectral optical imaging data.

  20. A Population of Very-Hot Super-Earths in Multiple-Planet Systems Should be Uncovered by Kepler

    OpenAIRE

    Schlaufman, Kevin C.; Lin, D. N. C.; Ida, S.

    2010-01-01

    We simulate a Kepler-like observation of a theoretical exoplanet population and we show that the observed orbital period distribution of the Kepler giant planet candidates is best matched by an average stellar specific dissipation function Q_* in the interval 10^6 ~< Q_* ~< 10^7. In that situation, the few super-Earths that are driven to orbital periods P < 1 day by dynamical interactions in multiple-planet systems will survive tidal disruption for a significant fraction of the main-sequence ...

  1. HOT 2010

    DEFF Research Database (Denmark)

    Lund, Henriette Romme

    En undersøgelse af, hvad der er hot - og burde være hot på læseområdet. I undersøgelsen deltager en række læsekyndige fra praksisfeltet, professionshøjskolerne og forskningsområdet. Undersøgelsen er gentaget hvert år siden 2010.......En undersøgelse af, hvad der er hot - og burde være hot på læseområdet. I undersøgelsen deltager en række læsekyndige fra praksisfeltet, professionshøjskolerne og forskningsområdet. Undersøgelsen er gentaget hvert år siden 2010....

  2. HOT 2013

    DEFF Research Database (Denmark)

    Lund, Henriette Romme

    En undersøgelse af, hvad der er hot - og burde være hot på læseområdet. I undersøgelsen deltager en række læsekyndige fra praksisfeltet, professionshøjskolerne og forskningsområdet. Undersøgelsen er gentaget hvert år siden 2010.......En undersøgelse af, hvad der er hot - og burde være hot på læseområdet. I undersøgelsen deltager en række læsekyndige fra praksisfeltet, professionshøjskolerne og forskningsområdet. Undersøgelsen er gentaget hvert år siden 2010....

  3. Rhodium Catalysts in the Oxidation of CO by O2 and NO: Shape, Composition, and Hot Electron Generation

    Energy Technology Data Exchange (ETDEWEB)

    Renzas, James R. [Univ. of California, Berkeley, CA (United States)

    2010-03-08

    It is well known that the activity, selectivity, and deactivation behavior of heterogeneous catalysts are strongly affected by a wide variety of parameters, including but not limited to nanoparticle size, shape, composition, support, pretreatment conditions, oxidation state, and electronic state. Enormous effort has been expended in an attempt to understand the role of these factors on catalytic behavior, but much still remains to be discovered. In this work, we have focused on deepening the present understanding of the role of nanoparticle shape, nanoparticle composition, and hot electrons on heterogeneous catalysis in the oxidation of carbon monoxide by molecular oxygen and nitric oxide. These reactions were chosen because they are important for environmental applications, such as in the catalytic converter, and because there is a wide range of experimental and theoretical insight from previous single crystal work as well as experimental data on nanoparticles obtained using new state-of-the-art techniques that aid greatly in the interpretation of results on complex nanoparticle systems. In particular, the studies presented in this work involve three types of samples: ~ 6.5 nm Rh nanoparticles of different shapes, ~ 15 nm Rh1-xPdx core-shell bimetallic polyhedra nanoparticles, and Rh ultra-thin film (~ 5 nm) catalytic nanodiodes. The colloidal nanoparticle samples were synthesized using a co-reduction of metal salts in alcohol and supported on silicon wafers using the Langmuir-Blodgett technique. This synthetic strategy enables tremendous control of nanoparticle size, shape, and composition. Nanoparticle shape was controlled through the use of different organic polymer capping layers. Bimetallic core-shell nanoparticles were synthesized by careful choice of metal salt precursors. Rh/TiOx and Rh/GaN catalytic nanodiodes were fabricated using a variety of thin film device fabrication techniques, including reactive DC magnetron

  4. Electron microscopy characterization of mechanically alloyed and hot consolidates Cu-Cr3C2 particles

    Directory of Open Access Journals (Sweden)

    López, M.

    2005-08-01

    Full Text Available Mechanically alloyed copper-ceramic composites have been obtained with the purpose of studying their use as copper-based material for electrical equipment. For high-temperature applications, dispersion-strengthened copper alloys are attractive due to their excellent combination of thermal and electrical conductivity, mechanical strength retention and microstructural stability. In this work, powder mixtures of pure copper with 2 vol % Cr3C2, milled during 4, 6, 10, 12 and 15 h in a high-energy planetary balls mill under argon atmosphere, were consolidated by hot isostatic pressing, applying a pressure of 100 MPa at 1073 K for two hours, to obtain materials with a fine microstructure. The Cu-Cr3C2 alloys were studied by scanning electron microscopy (SEM, electron microprobe (EPMA and transmission electron microscopy (TEM. Mechanical properties and electrical conductivity were also studied. The average tensile strength and electrical conductivity were found to be 500 MPa and 50 % IACS, respectively. The Cr3C2 ceramics show good stability during hot consolidation. Contributing to a further strengthening of the alloy during the hot consolidation, uniformly-distributed Fe-carbide particles of nanometric size precipitated in the copper matrix. Fe-Cr oxycarbides formed in the interphase between Cr3C2 particles and the copper matrix cause the low ductility of Cu-Cr3C2 alloys. Said particles are attributed to impurities/contamination generated from the milling process.

    Se obtuvieron aleaciones compuestas de Cu-Cr3C2, aleadas mecánicamente, para estudiar futuras aplicaciones en componentes eléctricos. A altas temperaturas, las aleaciones de base cobre reforzadas por dispersión, son atractivas por su excelente conductividad térmica y eléctrica, propiedades mecánicas y estabilidad microstructural. En este estudio

  5. Two distinct energetic electron populations of different origin in the Earth's magnetotail: a Cluster case study

    Directory of Open Access Journals (Sweden)

    I. I. Vogiatzis

    2006-08-01

    Full Text Available Energetic electrons (E≥30 keV travelling along and perpendicular to the magnetic field lines have been observed in the magnetotail at L~17:00 and 22:00 MLT during the recovery phase of a storm-time substorm on 7 October 2002. Three-dimensional electron distributions of the full unit sphere obtained from the IES/RAPID sensor system demonstrated a rather complicated and random behavior of the energetic electrons. Occasionally these electrons were appearing to travel parallel, perpendicular, or in both directions, relative to the magnetic field direction, forming in this way bi-directional, perpendicular-peaked, and mixed distributions. The electron enhancements occurred while the Cluster spacecraft were on closed field lines in the central plasma sheet approaching the neutral sheet from the northern tail lobe. Magnetic field and energetic particle measurements have been used from geosynchronous and Cluster satellites, in order to describe the general context of the event and then give a possible interpretation regarding the occurrence of the electron anisotropies observed by the IES/RAPID spectrometer on board Cluster. According to geosynchronous measurements an electron dispersionless ejection is very well correlated with a dipolar re-configuration of the magnetic field. The latter fact supports the idea that electrons and, in general, particle ejections at geosynchronous altitude are directly related to electric fields arising from field dipolarization caused by current disruption. Also, having as a main objective the understanding of the way 3-D electron distributions are formed, we have analyzed electron energy spectra along and perpendicular to the magnetic field direction, demonstrating the fact that the electron population consists of two distinct components acting independently and in a random manner relative to each other. This leads to the conclusion that these two electron populations along and perpendicular to the field are

  6. Velocity auto-correlation and hot-electron diffusion constant in GaAs and InP

    International Nuclear Information System (INIS)

    Deb Roy, M.

    1982-01-01

    Auto-correlation functions of the fluctuations in the electron velocities transverse and parallel to the applied electric field are calculated by the Monte Carlo method for GaAs and InP at three different values of field strength which are around three times the threshold field for negative differential mobility in each case. From these the frequency-dependent diffusion coefficients transverse and parallel to the applied field and the figure of merit for noise performance when used in a microwave amplifying device are determined. The results indicate that the transverse auto-correlation function Csub(t)(s) falls nearly exponentially to zero with increasing interval s while the parallel function Csub(p)(s) falls sharply, attains a minimum and then rises towards zero. In each case a higher field gives a higher rate of fall and makes the correlation functions zero within a shorter interval. The transverses diffusion coefficient falls monotonically with the frequency but the parallel diffusion coefficient generally starts with a low value at low frequencies, rises to a maximum and then falls. InP, with a larger separation between the central and the satellite valleys, has a higher value of the low frequency transverse diffusion coefficient and a lower value of its parallel counterpart. The noise performance of microwave semiconductor amplifying devices depends mainly on the low frequency parallel diffusion constant and consequently devices made out of materials like InP with a large separation between valleys are likely to have better noise characteristics. (orig.)

  7. The unexpected beneficial effect of the L-valley population on the electron mobility of GaAs nanowires

    International Nuclear Information System (INIS)

    Marin, E. G.; Ruiz, F. G.; Godoy, A.; Tienda-Luna, I. M.; Gámiz, F.

    2015-01-01

    The impact of the L-valley population on the transport properties of GaAs cylindrical nanowires (NWs) is analyzed by numerically calculating the electron mobility under the momentum relaxation time approximation. In spite of its low contribution to the electron mobility (even for high electron populations in small NWs), it is demonstrated to have a beneficial effect, since it significantly favours the Γ-valley mobility by screening the higher Γ-valley energy subbands

  8. Population of nitrogen molecule electron states and structure of the fast ionization wave

    CERN Document Server

    Pancheshnyi, S V; Starikovskii, A Y

    1999-01-01

    The excitation of N sub 2 (C sup 3 supPI sub u , nu=0) and N sup + sub 2 (B sup 2 supSIGMA sup + sub u , nu=0) electron states has been studied by using a time-resolved emission spectroscopy technique. To excite the above states, the nanosecond, high-voltage, periodic impulsed discharge at low pressures in the form of the fast ionization wave (FIW) was used. The electron concentration and the average energy, electric field were found on the basis of experimental data. The spacial-temporal structure of the FIW front was investigated. It has been shown that the generation of the required electron concentration, as well as the electron level population take place behind the FIW front in residual fields. Sections corresponding to the 'electric' and 'luminous' FIW fronts are essentially separated in space. The proposed modelling electron energy distribution function describes qualitatively general regularities of the breakdown propagation in the whole range of parameters under study. (author)

  9. Selective Electron Beam Manufacturing of Ti-6Al-4V Strips: Effect of Build Orientation, Columnar Grain Orientation, and Hot Isostatic Pressing on Tensile Properties

    Science.gov (United States)

    Wang, J.; Tang, H. P.; Yang, K.; Liu, N.; Jia, L.; Qian, M.

    2018-03-01

    Many novel designs for additive manufacturing (AM) contain thin-walled (≤ 3 mm) sections in different orientations. Selective electron beam melting (SEBM) is particularly suited to AM of such thin-walled titanium components because of its high preheating temperature and high vacuum. However, experimental data on SEBM of Ti-6Al-4V thin sections remains scarce because of the difficulty and high cost of producing long, thin and smooth strip tensile specimens (see Fig. 1). In this study, 80 SEBM Ti-6Al-4V strips (180 mm long, 42 mm wide, 3 mm thick) were built both vertically (V-strips) and horizontally (H-strips). Their density, microstructure and tensile properties were investigated. The V-strips showed clearly higher tensile strengths but lower elongation than the H-strips. Hot isostatic pressing (HIP) produced the same lamellar α-β microstructures in terms of the average α-lath thickness in both types of strips. The retained prior-β columnar grain boundaries after HIP showed no measurable influence on the tensile properties, irrespective of their length and orientation, because of the formation of randomly distributed fine α-laths.[Figure not available: see fulltext.

  10. Multiple-wavelength analysis of energy release during a solar flare - Thermal and nonthermal electron populations

    Science.gov (United States)

    Willson, Robert F.; Lang, Kenneth R.; Klein, Karl-Ludwig; Kerdraon, Alain; Trottet, Gerard

    1990-01-01

    Collaborative solar investigations by Tufts University and the Observatoire de Paris have resulted in simultaneous radio observations with the Very Large Array (VLA) and the Nancay Radioheliograph (NR), comparisons of this radio data with X-ray observations, and theoretical interpretations of the dominant radiation mechanisms during a weak impulsive solar flare observed on May 28, 1988. The VLA has mapped the flaring structures at time intervals of 3.3 s, showing that the preflash and flash-phase components of the impulsive emission originate in spatially separated sources. The 20.7 cm preflash source is ascribed to thermal gyroresonance emission from coronal loops with typical magnetic field strengths of up to 270 G; this emission is associated with heating and exhibits no detectable hard X-ray radiation above 30 keV. The flash-phase 20.7 cm source and the hard X-ray emission are attributed to nonthermal electrons in the coronal and chromospheric portions of a magnetic loop. The combination of imaging observations at 20.7 and 91.6 cm excludes emission from a confined hot plasma during the flash phase.

  11. Collisional effects on metastable atom population in vapour generated by electron beam heating

    International Nuclear Information System (INIS)

    Dikshit, B; Majumder, A; Bhatia, M S; Mago, V K

    2008-01-01

    The metastable atom population distribution in a free expanding uranium vapour generated by electron beam (e-beam) heating is expected to depart from its original value near the source due to atom-atom collisions and interaction with electrons of the e-beam generated plasma co-expanding with the vapour. To investigate the dynamics of the electron-atom and atom-atom interactions at different e-beam powers (or source temperatures), probing of the atomic population in ground (0 cm -1 ) and 620 cm -1 metastable states of uranium was carried out by the absorption technique using a hollow cathode discharge lamp. The excitation temperature of vapour at a distance ∼30 cm from the source was calculated on the basis of the measured ratio of populations in 620 to 0 cm -1 states and it was found to be much lower than both the source temperature and estimated translational temperature of the vapour that is cooled by adiabatic free expansion. This indicated relaxation of the metastable atoms by collisions with low energy plasma electrons was so significant that it brings the excitation temperature below the translational temperature of the vapour. So, with increase in e-beam power and hence atom density, frequent atom-atom collisions are expected to establish equilibrium between the excitation and translational temperatures, resulting in an increase in the excitation temperature (i.e. heating of vapour). This has been confirmed by analysing the experimentally observed growth pattern of the curve for excitation temperature with e-beam power. From the observed excitation temperature at low e-beam power when atom-atom collisions can be neglected, the total de-excitation cross section for relaxation of the 620 cm -1 state by interaction with low energy electrons was estimated and was found to be ∼10 -14 cm 2 . Finally using this value of cross section, the extent of excitational cooling and heating by electron-atom and atom-atom collisions are described at higher e-beam powers

  12. Use of electronic sales data to tailor nutrition education resources for an ethnically diverse population.

    Science.gov (United States)

    Eyles, H; Rodgers, A; Ni Mhurchu, C

    2010-02-01

    Nutrition education may be most effective when personally tailored. Individualised electronic supermarket sales data offer opportunities to tailor nutrition education using shopper's usual food purchases. The present study aimed to use individualised electronic supermarket sales data to tailor nutrition resources for an ethnically diverse population in a large supermarket intervention trial in New Zealand. Culturally appropriate nutrition education resources (i.e. messages and shopping lists) were developed with the target population (through two sets of focus groups) and ethnic researchers. A nutrient database of supermarket products was developed using retrospective sales data and linked to participant sales to allow tailoring by usual food purchases. Modified Heart Foundation Tick criteria were used to identify 'healthier' products in the database suitable for promotion in the resources. Rules were developed to create a monthly report listing the tailored and culturally targeted messages to be sent to each participant, and to produce automated, tailored shopping lists. Culturally targeted nutrition messages (n = 864) and shopping lists (n = 3 formats) were developed. The food and nutrient database (n = 3000 top-selling products) was created using 12 months of retrospective sales data, and comprised 60%'healthier' products. Three months of baseline sales data were used to determine usual food purchases. Tailored resources were successfully mailed to 123 Māori, 52 Pacific and 346 non-Māori non-Pacific participants over the 6-month trial intervention period. Electronic supermarket sales data can be used to tailor nutrition education resources for a large number of ethnically diverse supermarket shoppers.

  13. Validating an electronic health literacy scale in an older hispanic population.

    Science.gov (United States)

    Aponte, Judith; Nokes, Kathleen M

    2017-09-01

    To examine the validity of the Spanish version of an instrument used to measure electronic health literacy (eHEALS) with an older Hispanic population from a number of Spanish-language countries living in New York City in the United States (US). Although the Internet is available globally, complex skills are needed to use this source of valuable health-related information effectively. Electronic health literacy is a multifactorial concept that includes health literacy but also requires technology skills. Cross-sectional. Recruitment occurred at a Senior Organization located in a largely Hispanic neighbourhood in New York City (N = 100). Participants completed eHEALS and selected items from the Health Information National Trends Survey (HINTS) which assesses how adults use different communication channels, including the Internet, to obtain vital health information. Data from the US HINTS sample (N = 162) were matched to the Senior Organization sample on age range and Hispanic ethnicity. The average Senior Organization participant was 68 years old, female, born in one of six different Spanish-language countries, and completed high school while the average HINTS participant was 67 years old, female and had high school or less education. Although there was no relationship with the two HINTS subscales and electronic health literacy, there were significant relationships between electronic health literacy and health status and confidence in self-care. Inadequate electronic health literacy is a barrier to positive health outcomes. The Spanish version of eHEALS could be used as a screening instrument to identify gaps and tailored interventions could be developed to increase consumer confidence in using the Internet for reliable health-related information. Knowledge in self-management is related to positive health outcomes; all persons irrespective of their electronic health literacy should be able to use all sources of health information to enhance their self-care.

  14. Particle dynamics and current-free double layers in an expanding, collisionless, two-electron-population plasma

    International Nuclear Information System (INIS)

    Hairapetian, G.; Stenzel, R.L.

    1991-01-01

    The expansion of a two-electron-population, collisionless plasma into vacuum is investigated experimentally. Detailed in situ measurements of plasma density, plasma potential, electric field, and particle distribution functions are performed. At the source, the electron population consists of a high-density, cold (kT e congruent 4 eV) Maxwellian, and a sparse, energetic ( (1)/(2) mv 2 e congruent 80 eV) tail. During the expansion of plasma, space-charge effects self-consistently produce an ambipolar electric field whose amplitude is controlled by the energy of tail electrons. The ambipolar electric field accelerates a small number (∼1%) of ions to streaming energies which exceed and scale linearly with the energy of tail electrons. As the expansion proceeds, the energetic tail electrons electrostatically trap the colder Maxwellian electrons and prevent them from reaching the expansion front. A potential double layer develops at the position of the cold electron front. Upstream of the double layer both electron populations exist; but downstream, only the tail electrons do. Hence, the expansion front is dominated by retarded tail electrons. Initially, the double layer propagates away from the source with a speed approximately equal to the ion sound speed in the cold electron population. The propagation speed is independent of the tail electron energy. At later times, the propagating double layer slows down and eventually stagnates. The final position and amplitude of the double layer are controlled by the relative densities of the two electron populations in the source. The steady-state double layer persists till the end of the discharge (Δt congruent 1 msec), much longer than the ion transit time through the device (t congruent 150 μsec)

  15. Characterization of the RTP slideaway regime and its fast electron population

    International Nuclear Information System (INIS)

    Schokker, B.C.; Vries, P.C. de; Oomens, A.A.M.; Schueller, F.C.; Lopes Cardozo, N.J.

    1994-01-01

    Slideaway discharges in RTP (R 0 = 0.72 m, a = 0.16 m) have been analyzed. Slideaway discharges are characterized by an increase of the plasma energy content and of the electron cyclotron emission over the Ohmic values, bursts of emission around the lower hybrid frequency, and the occurrence of the Parail-Pogutse instability. The motivation for this investigation is twofold. Firstly, improved confinement is observed. Secondly, the large nonthermal electron population observed can be compared to predictions of the Parail-Pogutse instability theory. Measurements have been performed with magnetics, Thomson scattering (TVTS), ECE low and high field side (lfs and hfs) X-mode and O-mode emission viewing absorbers, soft X-ray tomography, and rf radiometry. The effects of ECRH on slideaway properties have been studied. (author) 4 refs., 4 figs

  16. [Knowledge of electronic cigarettes and their perceived harmfulness among the adult population in Barcelona (Spain)].

    Science.gov (United States)

    Martínez-Sánchez, José M; Fu, Marcela; Ballbè, Montse; Martín-Sánchez, Juan Carlos; Saltó, Esteve; Fernández, Esteve

    2015-01-01

    To describe knowledge of electronic cigarettes (e-cigarettes) and their perceived harmfulness in the population of Barcelona in 2013-2014. We used participants from a longitudinal study of a representative sample of the adult population in the city of Barcelona (n=736). The field work was conducted between May 2013 and February 2014. Awareness of e-cigarette was 79.2%. The average level of knowledge was 4.4 points out of 10; there were statistically significant differences according to age, educational level, tobacco consumption, and nicotine dependence. Most participants had learned about e-cigarettes through traditional media (57.8%). Nearly half (47.2%) of the participants believed that e-cigarettes are less harmful than conventional cigarettes. Advertising of e-cigarettes in the media should be regulated because there is still scarce scientific evidence about the usefulness and harmful effects of these devices. Copyright © 2014 SESPAS. Published by Elsevier Espana. All rights reserved.

  17. HOT 2017

    DEFF Research Database (Denmark)

    Hannibal, Sara Stefansen

    HOT er en kvalitativ undersøgelse, der hvert år diskuterer og undersøger en lille udvalgt skare af danskkyndige fagpersoners bud på, hvad de er optagede af på literacyområdet her og nu – altså hvilke emner, de vil vurdere som aktuelle at forholde sig til i deres nuværende praksis.......HOT er en kvalitativ undersøgelse, der hvert år diskuterer og undersøger en lille udvalgt skare af danskkyndige fagpersoners bud på, hvad de er optagede af på literacyområdet her og nu – altså hvilke emner, de vil vurdere som aktuelle at forholde sig til i deres nuværende praksis....

  18. Hot particles

    International Nuclear Information System (INIS)

    Merwin, S.E.; Moeller, M.P.

    1989-01-01

    Nuclear Regulatory Commission (NRC) licensees are required to assess the dose to skin from a hot particle contamination event at a depth of skin of7mg/cm 2 over an area of 1 cm 2 and compare the value to the current dose limit for the skin. Although the resulting number is interesting from a comparative standpoint and can be used to predict local skin reactions, comparison of the number to existing limits based on uniform exposures is inappropriate. Most incidents that can be classified as overexposures based on this interpretation of dose actually have no effect on the health of the worker. As a result, resources are expended to reduce the likelihood that an overexposure event will occur when they could be directed toward eliminating the cause of the problem or enhancing existing programs such as contamination control. Furthermore, from a risk standpoint, this practice is not ALARA because some workers receive whole body doses in order to minimize the occurrence of hot particle skin contaminations. In this paper the authors suggest an alternative approach to controlling hot particle exposures

  19. An efficient and reproducible process for transmission electron microscopy (TEM) of rare cell populations

    Science.gov (United States)

    Kumar, Sachin; Ciraolo, Georgianne; Hinge, Ashwini; Filippi, Marie-Dominique

    2014-01-01

    Transmission electron microscopy (TEM) provides ultra-structural details of cells at the sub-organelle level. However, details of the cellular ultrastructure, and the cellular organization and content of various organelles in rare populations, particularly in the suspension, like hematopoietic stem cells (HSCs) remained elusive. This is mainly due to the requirement of millions of cells for TEM studies. Thus, there is a vital requirement of a method that will allow TEM studies with low cell numbers of such rare populations. We describe an alternative and novel approach for TEM studies for rare cell populations. Here we performed TEM study from 10,000 HSC cells with quite ease. In particular, tiny cell pellets were identified by Evans blue staining after PFA-GA fixation. The cell pellet was pre-embedded in agarose in a small microcentrifuge tube and processed for dehydration, infiltration and embedding. Semi-thin and ultra-thin sections identified clusters of numerous cells per sections with well preserved morphology and ultrastructural details of golgi complex and mitochondria. Together, this method provides an efficient, easy and reproducible process to perform qualitative and quantitative TEM analysis from limited biological samples including cells in suspension. PMID:24291346

  20. Hot Gas Halos in Galaxies

    Science.gov (United States)

    Mulchaey, John

    Most galaxy formation models predict that massive low-redshift disk galaxies are embedded in extended hot halos of externally accreted gas. Such gas appears necessary to maintain ongoing star formation in isolated spirals like the Milky Way. To explain the large population of red galaxies in rich groups and clusters, most galaxy evolution models assume that these hot gas halos are stripped completely when a galaxy enters a denser environment. This simple model has been remarkably successful at reproducing many observed properties of galaxies. Although theoretical arguments suggest hot gas halos are an important component in galaxies, we know very little about this gas from an observational standpoint. In fact, previous observations have failed to detect soft X-ray emission from such halos in disk galaxies. Furthermore, the assumption that hot gas halos are stripped completely when a galaxy enters a group or cluster has not been verified. We propose to combine proprietary and archival XMM-Newton observations of galaxies in the field, groups and clusters to study how hot gas halos are impacted by environment. Our proposed program has three components: 1) The deepest search to date for a hot gas halo in a quiescent spiral galaxy. A detection will confirm a basic tenet of disk galaxy formation models, whereas a non-detection will seriously challenge these models and impose new constraints on the growth mode and feedback history of disk galaxies. 2) A detailed study of the hot gas halos properties of field early-type galaxies. As environmental processes such as stripping are not expected to be important in the field, a study of hot gas halos in this environment will allow us to better understand how feedback and other internal processes impact hot gas halos. 3) A study of hot gas halos in the outskirts of groups and clusters. By comparing observations with our suite of simulations we can begin to understand what role the stripping of hot gas halos plays in galaxy

  1. Magnetic sublevel population in 1s-2p excitation of helium by fast electrons and protons

    Energy Technology Data Exchange (ETDEWEB)

    Godunov, A.L.; McGuire, J.H. [Department of Physics, Tulane University, New Orleans, LA (United States); Merabet, H.; Bruch, R.; Hanni, J. [Department of Physics, University of Nevada Reno, Reno, NV (United States); Schipakov, V.S. [Troitsk Institute for Innovation and Fusion Research, Troitsk, (Russian Federation)

    2001-07-14

    We report experimental and theoretical results for the magnetic sublevel population of the helium atom in collisions with fast (v{sub i}=3-9 au) electrons and protons. Cross sections for excitation of magnetic sublevels with M=0 and {+-}1 have been obtained using polarization measurements of emitted radiation in combination with differential cross sections. Calculations have been carried out using the expansion of the transition amplitude in the Born series over the projectile-target interaction through the second order. Results of calculations are in agreement with experimental data. We find that the particle-antiparticle Z{sup {+-}} difference exceeds the statistical error of measurement up to collision velocities v{sub i}{approx}6 au for excitation of sublevels with M=0. (author)

  2. Plasma membrane characterization, by scanning electron microscopy, of multipotent myoblasts-derived populations sorted using dielectrophoresis.

    Science.gov (United States)

    Muratore, Massimo; Mitchell, Steve; Waterfall, Martin

    2013-09-06

    Multipotent progenitor cells have shown promise for use in biomedical applications and regenerative medicine. The implementation of such cells for clinical application requires a synchronized, phenotypically and/or genotypically, homogenous cell population. Here we have demonstrated the implementation of a biological tag-free dielectrophoretic device used for discrimination of multipotent myoblastic C2C12 model. The multipotent capabilities in differentiation, for these cells, diminishes with higher passage number, so for cultures above 70 passages only a small percentage of cells is able to differentiate into terminal myotubes. In this work we demonstrated that we could recover, above 96% purity, specific cell types from a mixed population of cells at high passage number without any biological tag using dielectrophoresis. The purity of the samples was confirmed by cytometric analysis using the cell specific marker embryonic myosin. To further investigate the dielectric properties of the cell plasma membrane we co-culture C2C12 with similar size, when in suspension, GFP-positive fibroblast as feeder layer. The level of separation between the cell types was above 98% purity which was confirmed by flow cytometry. These levels of separation are assumed to account for cell size and for the plasma membrane morphological differences between C2C12 and fibroblast unrelated to the stages of the cell cycle which was assessed by immunofluorescence staining. Plasma membrane conformational differences were further confirmed by scanning electron microscopy. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. "Community vital signs": incorporating geocoded social determinants into electronic records to promote patient and population health.

    Science.gov (United States)

    Bazemore, Andrew W; Cottrell, Erika K; Gold, Rachel; Hughes, Lauren S; Phillips, Robert L; Angier, Heather; Burdick, Timothy E; Carrozza, Mark A; DeVoe, Jennifer E

    2016-03-01

    Social determinants of health significantly impact morbidity and mortality; however, physicians lack ready access to this information in patient care and population management. Just as traditional vital signs give providers a biometric assessment of any patient, "community vital signs" (Community VS) can provide an aggregated overview of the social and environmental factors impacting patient health. Knowing Community VS could inform clinical recommendations for individual patients, facilitate referrals to community services, and expand understanding of factors impacting treatment adherence and health outcomes. This information could also help care teams target disease prevention initiatives and other health improvement efforts for clinic panels and populations. Given the proliferation of big data, geospatial technologies, and democratization of data, the time has come to integrate Community VS into the electronic health record (EHR). Here, the authors describe (i) historical precedent for this concept, (ii) opportunities to expand upon these historical foundations, and (iii) a novel approach to EHR integration. © The Author 2015. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. A method for the direct measurement of electronic site populations in a molecular aggregate using two-dimensional electronic-vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Nicholas H. C.; Dong, Hui; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720 (United States)

    2015-09-28

    Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale.

  5. Experimental study of hot electrons propagation and energy deposition in solid or laser-shock compressed targets: applications to fast igniter; Etude experimentale de la propagation et du depot d'energie d'electrons rapides dans une cible solide ou comprimee par choc laser: application a l'allumeur rapide

    Energy Technology Data Exchange (ETDEWEB)

    Pisani, F

    2000-02-15

    In the fast igniter scheme, a recent approach proposed for the inertial confinement fusion, the idea is to dissociate the fuel ignition phase from its compression. The ignition phase would be then achieved by means of an external energy source: a fast electron beam generated by the interaction with an ultra-intense laser. The main goal of this work is to study the mechanisms of the hot electron energy transfer to the compressed fuel. We intent in particular to study the role of the electric and collisional effects involved in the hot electron propagation in a medium with properties similar to the compressed fuel. We carried out two experiments, one at the Vulcan laser facility (England) and the second one at the new LULI 100 TW laser (France). During the first experiment, we obtained the first results on the hot electron propagation in a dense and hot plasma. The innovating aspect of this work was in particular the use of the laser-shock technique to generate high pressures, allowing the strongly correlated and degenerated plasma to be created. The role of the electric and magnetic effects due to the space charge associated with the fast electron beam has been investigated in the second experiment. Here we studied the propagation in materials with different electrical characteristics: an insulator and a conductor. The analysis of the results showed that only by taking into account simultaneously the two propagation mechanisms (collisions and electric effects) a correct treatment of the energy deposition is possible. We also showed the importance of taking into account the induced modifications due to the electrons beam crossing the target, especially the induced heating. (author)

  6. Plasma membrane characterization, by scanning electron microscopy, of multipotent myoblasts-derived populations sorted using dielectrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Muratore, Massimo, E-mail: M.Muratore@ed.ac.uk [Institute of Integrated Micro and Nano System, School of Engineering, The University of Edinburgh, Edinburgh EH9 3JF (United Kingdom); Mitchell, Steve [Institute of Molecular Plant Science, School of Biological Science, The University of Edinburgh, Edinburgh EH9 3JF (United Kingdom); Waterfall, Martin [Institute of Immunology and Infection Research, School of Biological Science, The University of Edinburgh, Edinburgh EH9 3JT (United Kingdom)

    2013-09-06

    Highlights: •Dielectrophoretic separation/sorting of multipotent cells. •Plasma membrane microvilli structure of C2C12 and fibroblasts by SEM microscopy. •Cell cycle determination by Ki-67 in DEP-sorted cells. •Plasma membrane differences responsible for changes in membrane capacitance. -- Abstract: Multipotent progenitor cells have shown promise for use in biomedical applications and regenerative medicine. The implementation of such cells for clinical application requires a synchronized, phenotypically and/or genotypically, homogenous cell population. Here we have demonstrated the implementation of a biological tag-free dielectrophoretic device used for discrimination of multipotent myoblastic C2C12 model. The multipotent capabilities in differentiation, for these cells, diminishes with higher passage number, so for cultures above 70 passages only a small percentage of cells is able to differentiate into terminal myotubes. In this work we demonstrated that we could recover, above 96% purity, specific cell types from a mixed population of cells at high passage number without any biological tag using dielectrophoresis. The purity of the samples was confirmed by cytometric analysis using the cell specific marker embryonic myosin. To further investigate the dielectric properties of the cell plasma membrane we co-culture C2C12 with similar size, when in suspension, GFP-positive fibroblast as feeder layer. The level of separation between the cell types was above 98% purity which was confirmed by flow cytometry. These levels of separation are assumed to account for cell size and for the plasma membrane morphological differences between C2C12 and fibroblast unrelated to the stages of the cell cycle which was assessed by immunofluorescence staining. Plasma membrane conformational differences were further confirmed by scanning electron microscopy.

  7. Electronic Cigarettes Among Priority Populations: Role of Smoking Cessation and Tobacco Control Policies.

    Science.gov (United States)

    Huang, Jidong; Kim, Yoonsang; Vera, Lisa; Emery, Sherry L

    2016-02-01

    The electronic cigarette (e-cigarette) market has evolved rapidly in recent years, with exploding growth in brands and product types; however, e-cigarette use among priority (sexual minority and low-income) populations and its relationship with smoking-cessation and tobacco control policies have yet to be fully characterized. The authors conducted a nationally representative online survey of 17,522 U.S. adults in 2013. Participants were drawn from GfK's KnowledgePanel. Logistic regression models were used to analyze relationships between e-cigarettes (awareness, ever use, current use) and cigarette smoking and cessation behaviors, tobacco control policies, and demographics. Analyses were conducted in 2014. Approximately 15% of participants reported ever use of e-cigarettes, 5.1% reported current use, and 34.5% of ever users reported current use. E-cigarette awareness was lower among women, minorities, and those with low education. Ever and current use of e-cigarettes was higher among current cigarette smokers, young adults, and those with low SES; both ever use and current use were correlated with current cigarette smoking status, particularly when combined with quit intentions or attempts. Lesbian/gay/bisexual/transgender respondents had higher rates of ever use and current use. Ever use was lower in states with comprehensive smoking bans. No significant relationship between cigarette price and e-cigarette use was detected. Ongoing surveillance of e-cigarette use among subpopulation groups and monitoring their use for combustible cigarette cessation are needed. Important variations in the patterns and correlates of e-cigarette awareness and use exist among priority populations. These findings have implications for future e-cigarette policy decisions. Copyright © 2016 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

  8. Plasma membrane characterization, by scanning electron microscopy, of multipotent myoblasts-derived populations sorted using dielectrophoresis

    International Nuclear Information System (INIS)

    Muratore, Massimo; Mitchell, Steve; Waterfall, Martin

    2013-01-01

    Highlights: •Dielectrophoretic separation/sorting of multipotent cells. •Plasma membrane microvilli structure of C2C12 and fibroblasts by SEM microscopy. •Cell cycle determination by Ki-67 in DEP-sorted cells. •Plasma membrane differences responsible for changes in membrane capacitance. -- Abstract: Multipotent progenitor cells have shown promise for use in biomedical applications and regenerative medicine. The implementation of such cells for clinical application requires a synchronized, phenotypically and/or genotypically, homogenous cell population. Here we have demonstrated the implementation of a biological tag-free dielectrophoretic device used for discrimination of multipotent myoblastic C2C12 model. The multipotent capabilities in differentiation, for these cells, diminishes with higher passage number, so for cultures above 70 passages only a small percentage of cells is able to differentiate into terminal myotubes. In this work we demonstrated that we could recover, above 96% purity, specific cell types from a mixed population of cells at high passage number without any biological tag using dielectrophoresis. The purity of the samples was confirmed by cytometric analysis using the cell specific marker embryonic myosin. To further investigate the dielectric properties of the cell plasma membrane we co-culture C2C12 with similar size, when in suspension, GFP-positive fibroblast as feeder layer. The level of separation between the cell types was above 98% purity which was confirmed by flow cytometry. These levels of separation are assumed to account for cell size and for the plasma membrane morphological differences between C2C12 and fibroblast unrelated to the stages of the cell cycle which was assessed by immunofluorescence staining. Plasma membrane conformational differences were further confirmed by scanning electron microscopy

  9. Population densities and rate coefficients for electron impact excitation in singly ionized oxygen

    International Nuclear Information System (INIS)

    Awakowicz, P.; Behringer, K.

    1995-01-01

    In non-LTE arc plasmas, O II excited state number densities were measured relative to the O II ground and metastable states. The results were compared with collisional-radiative code calculations on the basis of the JET ADAS programs. Stationary He plasmas with small oxygen admixtures, generated in a 5 mm diameter cascade arc chamber (pressures 13-70 hPa, arc current 150 A), were investigated spectroscopically in the visible and the VUV spectral range. The continuum of a 2 mm diameter pure He arc (atmospheric pressure, current 100 A) served for calibration of the VUV system response. Plasma diagnostics on the basis of Hβ Stark broadening yielded electron densities between 2.4 x 10 14 and 2.0 x 10 15 cm -3 for the low-pressure O II mixture plasmas. The agreement of measured and calculated excited state populations is generally very satisfactory, thus confirming the rate coefficients in the code. This is of particular interest in this intermediate region between corona balance and LTE, where many atomic data are required in the simulation. Clear indications were found for the diffusion of metastables lowering their number densities significantly below their statistical values. (author)

  10. Calculation of Ground State Rotational Populations for Kinetic Gas Homonuclear Diatomic Molecules including Electron-Impact Excitation and Wall Collisions

    International Nuclear Information System (INIS)

    Farley, David R.

    2010-01-01

    A model has been developed to calculate the ground-state rotational populations of homonuclear diatomic molecules in kinetic gases, including the effects of electron-impact excitation, wall collisions, and gas feed rate. The equations are exact within the accuracy of the cross sections used and of the assumed equilibrating effect of wall collisions. It is found that the inflow of feed gas and equilibrating wall collisions can significantly affect the rotational distribution in competition with non-equilibrating electron-impact effects. The resulting steady-state rotational distributions are generally Boltzmann for N (ge) 3, with a rotational temperature between the wall and feed gas temperatures. The N = 0,1,2 rotational level populations depend sensitively on the relative rates of electron-impact excitation versus wall collision and gas feed rates.

  11. Agile Model Driven Development of Electronic Health Record-Based Specialty Population Registries

    Science.gov (United States)

    Kannan, Vaishnavi; Fish, Jason C.; Willett, DuWayne L.

    2018-01-01

    The transformation of the American healthcare payment system from fee-for-service to value-based care increasingly makes it valuable to develop patient registries for specialized populations, to better assess healthcare quality and costs. Recent widespread adoption of Electronic Health Records (EHRs) in the U.S. now makes possible construction of EHR-based specialty registry data collection tools and reports, previously unfeasible using manual chart abstraction. But the complexities of specialty registry EHR tools and measures, along with the variety of stakeholders involved, can result in misunderstood requirements and frequent product change requests, as users first experience the tools in their actual clinical workflows. Such requirements churn could easily stall progress in specialty registry rollout. Modeling a system’s requirements and solution design can be a powerful way to remove ambiguities, facilitate shared understanding, and help evolve a design to meet newly-discovered needs. “Agile Modeling” retains these values while avoiding excessive unused up-front modeling in favor of iterative incremental modeling. Using Agile Modeling principles and practices, in calendar year 2015 one institution developed 58 EHR-based specialty registries, with 111 new data collection tools, supporting 134 clinical process and outcome measures, and enrolling over 16,000 patients. The subset of UML and non-UML models found most consistently useful in designing, building, and iteratively evolving EHR-based specialty registries included User Stories, Domain Models, Use Case Diagrams, Decision Trees, Graphical User Interface Storyboards, Use Case text descriptions, and Solution Class Diagrams. PMID:29750222

  12. Effect of electron beam irradiation and microencapsulation on the flame retardancy of ethylene-vinyl acetate copolymer materials during hot water ageing test

    International Nuclear Information System (INIS)

    Sheng, Haibo; Zhang, Yan; Wang, Bibo; Yu, Bin; Shi, Yongqian; Song, Lei; Kundu, Chanchal Kumar; Tao, Youji; Jie, Ganxin; Feng, Hao; Hu, Yuan

    2017-01-01

    Microencapsulated ammonium polyphosphate (MCAPP) in combination with polyester polyurethane (TPU) was used to flame retardant ethylene-vinyl acetate copolymer (EVA). The EVA composites with different irradiation doses were immersed in hot water (80 °C) to accelerate ageing process. The microencapsulation and irradiation dose ensured positive impacts on the properties of the EVA composites in terms of better dimensional stability and flame retardant performance. The microencapsulation of APP could lower its solubility in water and the higher irradiation dose led to the more MCAPP immobilized in three dimensional crosslinked structure of the EVA matrix which could jointly enhance the flame retardant and electrical insulation properties of the EVA composites. So, the EVA composites with 180 kGy irradiation dose exhibited better dimensional stability than the EVA composites with 120 kGy due to the higher crosslinking degree. Moreover, the higher irradiation dose lead to the more MCAPP immobilizated in crosslinked three-dimensional structure of EVA, enhancing the flame retardancy and electrical insulation properties of the EVA composites. After ageing test in hot water at 80 °C for 2 weeks, the EVA/TPU/MCAPP composite with 180 kGy could still maintain the UL-94 V-0 rating and the limiting oxygen index (LOI) value was as high as 30%. This investigation indicated the flame retardant EVA cable containing MCAPP could achieve stable properties and lower electrical fire hazard risk during long-term hot water ageing test. - Highlights: • Microencapsulated ammonium polyphosphate is prepared by successive sol-gel process. • The higher irradiation dose induces the better dimensional stability for EVA system. • The higher irradiation, the more MCAPP immobilized in EVA crosslinked structure. • The higher irradiation dose enhances the flame retardancy of EVA composites. • The microencapsulated composites demonstrate stable flame retardancy in ageing test.

  13. Hot tearing studies in AA5182

    Science.gov (United States)

    van Haaften, W. M.; Kool, W. H.; Katgerman, L.

    2002-10-01

    One of the major problems during direct chill (DC) casting is hot tearing. These tears initiate during solidification of the alloy and may run through the entire ingot. To study the hot tearing mechanism, tensile tests were carried out in semisolid state and at low strain rates, and crack propagation was studied in situ by scanning electron microscopy (SEM). These experimentally induced cracks were compared with hot tears developed in an AA5182 ingot during a casting trial in an industrial research facility. Similarities in the microstructure of the tensile test specimens and the hot tears indicate that hot tearing can be simulated by performing tensile tests at semisolid temperatures. The experimental data were compared with existing hot tearing models and it was concluded that the latter are restricted to relatively high liquid fractions because they do not take into account the existence of solid bridges in the crack.

  14. Chromosomal aberrations and DNA damage in human populations exposed to the processing of electronics waste.

    Science.gov (United States)

    Liu, Qiang; Cao, Jia; Li, Ke Qiu; Miao, Xu Hong; Li, Guang; Fan, Fei Yue; Zhao, Yong Cheng

    2009-05-01

    were significantly higher than in the control group (P = 0.000). The percentage of DNA in the comet tail, tail moment, and Olive tail moment detected by comet assay showed that there was a significant difference in DNA damage in the exposure group (P = 0.000). The chromosome aberration, micronucleus rate, and DNA damage observed in women were significantly higher than those in men. Chromosome aberration and micronuclear rates of both smokers and non-smokers in the exposure group are obviously higher than that in the control group (P = 0.000). The use of outdated (and unsafe) ways to deal with E-wastes can lead to exposure to a variety of substances harmful to human health. The components of pollution may enter the human body through the air, drinking water, and food chain to damage human genetic material, resulting in genomic instability. The rates of chromosomal aberration, micronucleus formation, and the degree of DNA damage in women in the group exposed to electronic waste were significantly higher than in men. The reason for this may be concerned with the traditional lifestyle of the local residents or the difference of sensitivity to the exposure to E-wastes or any others. Further investigations are needed to provide evidence to demonstrate this. Here, we report the obviously cytogenetic toxicity to the exposure population by the E-waste pollution for the first time. E-waste pollution may be a potential agent of genetic mutation, and may induce cytogenetic damage within the general population exposed to the pollution. These findings need to be considered, and steps should be taken to protect the current population and future generations from the effects of pollution with E-wastes. The above results remind us that the impact of E-waste recycling on environmental quality of Jinghai should be evaluated soon. Moreover, it is urgent for the government to prohibit E-waste import and its processing by outdated ways. The future studies such as pollutant details of

  15. Measuring hot flash phenomenonology using ambulatory prospective digital diaries

    Science.gov (United States)

    Fisher, William I.; Thurston, Rebecca C.

    2016-01-01

    Objective This study provides the description, protocol, and results from a novel prospective ambulatory digital hot flash phenomenon diary. Methods This study included 152 midlife women with daily hot flashes who completed an ambulatory electronic hot flash diary continuously for the waking hours of 3 consecutive days. In this diary, women recorded their hot flashes and accompanying characteristics and associations as the hot flashes occurred. Results Self-reported hot flash severity on the digital diaries indicated that the majority of hot flashes were rated as mild (41.3%) or moderate (43.7%). Severe (13.1%) and very severe (1.8%) hot flashes were less common. Hot flash bother ratings were rated as mild (43%), or moderate (33.5%), with fewer hot flashes reported bothersome (17.5%) or very bothersome (6%). The majority of hot flashes were reported as occurring on the on the face (78.9%), neck (74.7%), and chest (61.3%). Prickly skin was reported concurrently with 32% of hot flashes, 7% with anxiety and 5% with nausea. A novel finding, 38% of hot flashes were accompanied by a premonitory aura. Conclusion A prospective electronic digital hot flash diary allows for a more precise quantitation of hot flashes while overcoming many of the limitations of commonly employed retrospective questionnaires and paper diaries. Unique insights into the phenomenology, loci and associated characteristics of hot flashes were obtained using this device. The digital hot flash phenomenology diary is recommended for future ambulatory studies of hot flashes as a prospective measure of the hot flash experience. PMID:27404030

  16. Solar 'hot spots' are still hot

    Science.gov (United States)

    Bai, Taeil

    1990-01-01

    Longitude distributions of solar flares are not random but show evidence for active zones (or hot spots) where flares are concentrated. According to a previous study, two hot spots in the northern hemisphere, which rotate with a synodic period of about 26.72 days, produced the majority of major flares, during solar cycles 20 and 21. The more prominent of these two hot spots is found to be still active during the rising part of cycle 22, producing the majority of northern hemisphere major flares. The synodic rotation period of this hot spot is 26.727 + or - 0.007 days. There is also evidence for hot spots in the southern hemisphere. Two hot spots separated by 180 deg are found to rotate with a period of 29.407 days, with one of them having persisted in the same locations during cycles 19-22 and the other, during cycles 20-22.

  17. Solar hot spots are still hot

    International Nuclear Information System (INIS)

    Bai, T.

    1990-01-01

    Longitude distributions of solar flares are not random but show evidence for active zones (or hot spots) where flares are concentrated. According to a previous study, two hot spots in the northern hemisphere, which rotate with a synodic period of about 26.72 days, produced the majority of major flares, during solar cycles 20 and 21. The more prominent of these two hot spots is found to be still active during the rising part of cycle 22, producing the majority of northern hemisphere major flares. The synodic rotation period of this hot spot is 26.727 + or - 0.007 days. There is also evidence for hot spots in the southern hemisphere. Two hot spots separated by 180 deg are found to rotate with a period of 29.407 days, with one of them having persisted in the same locations during cycles 19-22 and the other, during cycles 20-22. 14 refs

  18. The hot plasma environment at jupiter: ulysses results.

    Science.gov (United States)

    Lanzerotti, L J; Armstrong, T P; Gold, R E; Anderson, K A; Krimigis, S M; Lin, R P; Pick, M; Roelof, E C; Sarris, E T; Simnett, G M; Maclennan, C G; Choo, H T; Tappin, S J

    1992-09-11

    Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.

  19. Coulomb explosion of “hot spot”

    Energy Technology Data Exchange (ETDEWEB)

    Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru [Institute of High Current Electrons, SB, RAS, Tomsk (Russian Federation); Tomsk Polytechnic University, Tomsk (Russian Federation); Oreshkin, E. V. [P. N. Lebedev Physical Institute, RAS, Moscow (Russian Federation); Chaikovsky, S. A. [Institute of High Current Electrons, SB, RAS, Tomsk (Russian Federation); P. N. Lebedev Physical Institute, RAS, Moscow (Russian Federation); Institute of Electrophysics, UD, RAS, Ekaterinburg (Russian Federation); Artyomov, A. P. [Institute of High Current Electrons, SB, RAS, Tomsk (Russian Federation)

    2016-09-15

    The study presented in this paper has shown that the generation of hard x rays and high-energy ions, which are detected in pinch implosion experiments, may be associated with the Coulomb explosion of the hot spot that is formed due to the outflow of the material from the pinch cross point. During the process of material outflow, the temperature of the hot spot plasma increases, and conditions arise for the plasma electrons to become continuously accelerated. The runaway of electrons from the hot spot region results in the buildup of positive space charge in this region followed by a Coulomb explosion. The conditions for the hot spot plasma electrons to become continuously accelerated have been revealed, and the estimates have been obtained for the kinetic energy of the ions generated by the Coulomb explosion.

  20. Coulomb explosion of “hot spot”

    International Nuclear Information System (INIS)

    Oreshkin, V. I.; Oreshkin, E. V.; Chaikovsky, S. A.; Artyomov, A. P.

    2016-01-01

    The study presented in this paper has shown that the generation of hard x rays and high-energy ions, which are detected in pinch implosion experiments, may be associated with the Coulomb explosion of the hot spot that is formed due to the outflow of the material from the pinch cross point. During the process of material outflow, the temperature of the hot spot plasma increases, and conditions arise for the plasma electrons to become continuously accelerated. The runaway of electrons from the hot spot region results in the buildup of positive space charge in this region followed by a Coulomb explosion. The conditions for the hot spot plasma electrons to become continuously accelerated have been revealed, and the estimates have been obtained for the kinetic energy of the ions generated by the Coulomb explosion.

  1. Simulation of the electron acoustic instability for a finite-size electron beam system

    International Nuclear Information System (INIS)

    Lin, C.S.; Winske, D.

    1987-01-01

    Satellite observations at midlatitudes (≅20,000 km) near the earth's dayside polar cusp boundary layer indicate that the upward electron beams have a narrow latitudinal width up to 0.1 0 . In the cusp boundary layer where the electron population consists of a finite-size electron beam in a background of uniform cold and hot electrons, the electron acoustic mode is unstable inside the electron beam but damped outside the electron beam. Simulations of the electron acoustic instability for a finite-size beam system are carried out with a particle-in-cell code to investigate the heating phenomena associated with the instability and the width of the heating region. The simulations show that the finite-size electron beam radiates electrostatic electron acoustic waves. The decay length of the electron acoustic waves outside the beam in the simulation agrees with the spatial decay length derived from the linear dispersion equation

  2. Population structure and historical demography of Dipteronia dyeriana (Sapindaceae), an extremely narrow palaeoendemic plant from China: implications for conservation in a biodiversity hot spot.

    Science.gov (United States)

    Chen, C; Lu, R S; Zhu, S S; Tamaki, I; Qiu, Y X

    2017-08-01

    Inferring past demography is a central question in evolutionary and conservation biology. It is, however, sometimes challenging to disentangle their roles of contemporary versus historical processes in shaping the current patterns of genetic variation in endangered species. In this study, we used both chloroplast microsatellite (cpSSR) loci and nuclear microsatellite (nSSR) loci to assess the levels of genetic differentiation, genetic effective population size, contemporary/historical levels of gene flow and demographic history for five populations sampled across the range of Dipteronia dyeriana, an endangered palaeoendemism from Southwestern China. We found that D. dyeriana had a mixed pattern of moderate genetic diversity and high inbreeding. Bayesian clustering divided D. dyeriana populations into two nSSR genetic clusters. Coalescent-based approximate Bayesian computation analyses suggest the western and eastern groups of D. dyeriana likely persisted in a long-term refuge in Southern China since the beginning of the last glacial period, whereas increasingly colder and arid climates at the onset of the last glacial maximum might have fostered the fragmentation of D. dyeriana within refugia. Following their divergence, the western group kept relatively stable effective population size, whereas the eastern group had experienced 500-fold population expansion during the Holocene. Although clear loss of genetic diversity by human activities was not suggested, recent habitat fragmentation has led to a reduction of population connectivity and increased genetic differentiation by ongoing genetic drift in isolated populations, possibly owing to decreased population size in recent dozen years. Finally, we discussed the implications of these results on conservation policies.

  3. Transmission electron microscopy of aged Ti-10Mo-20Nb alloy after hot swaging; Microscopia eletronica de transmissao da liga Ti-10Mo-20Nb envelhecida apos forjamento a quente

    Energy Technology Data Exchange (ETDEWEB)

    Gabriel, Sinara Borborema, E-mail: sinarab@msn.com [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil); Baldan, Renato, E-mail: renatobaldan@gmail.com [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Torres, Juliana; Oliveira, Nathalia Rodrigues, E-mail: juliana_torres_5@hotmail.com, E-mail: nathalia_roliveira@yahoo.com.br [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Mei, Paulo Roberto, E-mail: cnunes@demar.eel.usp.br, E-mail: pmei@fem.unicamp.br [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil)

    2014-08-15

    Ti alloys are widely used in biomedical applications. Within this class, metastable β -Ti alloys stand, because through thermomechanical processing it is possible to obtain mechanical properties and in particular one suitable Young's modulus for biomedical applications. These alloys require high mechanical strength and a low Young's modulus to avoid stress shielding. Preliminary studies showed that the microstructure of the Ti-10Mo- 20Nb alloy after cold forging and aging 500 °C/24 h consisted in bimodal distribution of α phase in the β matrix. The aim of this study was to characterize the microstructure of Ti-10Mo-20Nb alloy after hot forging and aging at 500 °C for 24 hours. Microstructural characterization consisted of analyzes by X-ray diffraction and transmission electron microscopy. According to the results, while the cold forging resulted in a bimodal α distribution in the β matrix, hot forging resulted in a thin and homogeneous α precipitation in the β matrix. (author)

  4. Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations.

    Science.gov (United States)

    Nogueira, P; Zankl, M; Schlattl, H; Vaz, P

    2011-11-07

    The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

  5. Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations

    International Nuclear Information System (INIS)

    Nogueira, P; Vaz, P; Zankl, M; Schlattl, H

    2011-01-01

    The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

  6. Non-thermal electron populations in microwave heated plasmas investigated with X-ray detectors

    Energy Technology Data Exchange (ETDEWEB)

    Belapure, Jaydeep Sanjay

    2013-04-15

    An investigation of the generation and dynamics of superthermal electrons in fusion plasma is carried out. A SDD+CsI(Tl) based X-ray diagnostic is constructed, characterized and installed at ASDEX Upgrade. In various plasma heating power and densities, the fraction and the energy distribution of the superthermal electrons is obtained by a bi-Maxwellian model and compared with Fokker-Planck simulations.

  7. The formation of kappa-distribution accelerated electron populations in solar flares

    Energy Technology Data Exchange (ETDEWEB)

    Bian, Nicolas H.; Stackhouse, Duncan J.; Kontar, Eduard P. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Emslie, A. Gordon, E-mail: n.bian@physics.gla.ac.uk, E-mail: d.stackhouse.1@research.gla.ac.uk, E-mail: eduard@astro.gla.ac.uk, E-mail: emslieg@wku.edu [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2014-12-01

    Driven by recent RHESSI observations of confined loop-top hard X-ray sources in solar flares, we consider stochastic acceleration of electrons in the presence of Coulomb collisions. If electron escape from the acceleration region can be neglected, the electron distribution function is determined by a balance between diffusive acceleration and collisions. Such a scenario admits a stationary solution for the electron distribution function that takes the form of a kappa distribution. We show that the evolution toward this kappa distribution involves a 'wave front' propagating forward in velocity space, so that electrons of higher energy are accelerated later; the acceleration timescales with energy according to τ{sub acc} ∼ E {sup 3/2}. At sufficiently high energies escape from the finite-length acceleration region will eventually dominate. For such energies, the electron velocity distribution function is obtained by solving a time-dependent Fokker-Planck equation in the 'leaky-box' approximation. Solutions are obtained in the limit of a small escape rate from an acceleration region that can effectively be considered a thick target.

  8. Rapid Development of Specialty Population Registries and Quality Measures from Electronic Health Record Data.

    Science.gov (United States)

    Kannan, Vaishnavi; Fish, Jason S; Mutz, Jacqueline M; Carrington, Angela R; Lai, Ki; Davis, Lisa S; Youngblood, Josh E; Rauschuber, Mark R; Flores, Kathryn A; Sara, Evan J; Bhat, Deepa G; Willett, DuWayne L

    2017-01-01

    Creation of a new electronic health record (EHR)-based registry often can be a "one-off" complex endeavor: first developing new EHR data collection and clinical decision support tools, followed by developing registry-specific data extractions from the EHR for analysis. Each development phase typically has its own long development and testing time, leading to a prolonged overall cycle time for delivering one functioning registry with companion reporting into production. The next registry request then starts from scratch. Such an approach will not scale to meet the emerging demand for specialty registries to support population health and value-based care. To determine if the creation of EHR-based specialty registries could be markedly accelerated by employing (a) a finite core set of EHR data collection principles and methods, (b) concurrent engineering of data extraction and data warehouse design using a common dimensional data model for all registries, and (c) agile development methods commonly employed in new product development. We adopted as guiding principles to (a) capture data as a byproduct of care of the patient, (b) reinforce optimal EHR use by clinicians, (c) employ a finite but robust set of EHR data capture tool types, and (d) leverage our existing technology toolkit. Registries were defined by a shared condition (recorded on the Problem List) or a shared exposure to a procedure (recorded on the Surgical History) or to a medication (recorded on the Medication List). Any EHR fields needed - either to determine registry membership or to calculate a registry-associated clinical quality measure (CQM) - were included in the enterprise data warehouse (EDW) shared dimensional data model. Extract-transform-load (ETL) code was written to pull data at defined "grains" from the EHR into the EDW model. All calculated CQM values were stored in a single Fact table in the EDW crossing all registries. Registry-specific dashboards were created in the EHR to display both

  9. Steering wave packet dynamics and population transfer between electronic states of the Na2 molecule by femtosecond laser pulses

    International Nuclear Information System (INIS)

    Yuan Kaijun; Sun Zhigang; Cong Shulin; Wang Senming; Yu Jie; Lou Nanquan

    2005-01-01

    An approach used for steering the wave packet dynamics and the population transfer between electronic states of the Na 2 molecule by a pair of femtosecond laser pulses is demonstrated. Four controlling schemes, i.e., four different combinations of time delays (intuitive and counterintuitive sequences) and frequency detunings (positive and negative detunings), are discussed in detail. The light-induced potentials are used to describe the wave packet dynamics and population transfer. The numerical results show that the wave packet excited by femtosecond laser pulses oscillates drastically on 2 1 Π g state with time. The efficiency of controlling population transfer from the X 1 Σ g + to2 1 Π g states of Na 2 is nearly 100% for the schemes of the counterintuitive sequence pulses with positive and negative detunings

  10. Controlling the properties of ultraintense laser-proton sources using transverse refluxing of hot electrons in shaped mass-limited targets

    International Nuclear Information System (INIS)

    Tresca, O; Carroll, D C; Yuan, X H; Brenner, C M; Coury, M; Gray, R J; Quinn, M N; McKenna, P; Aurand, B; Bagnoud, V; Fils, J; Kuehl, T; Zielbauer, B; Li, C; Li, Y T; Lin, X X; Evans, R G; Roth, M; Neely, D

    2011-01-01

    We report on the transverse refluxing of energetic electrons in mass-limited foil targets irradiated with high intensity (1 x 10 19 W cm -2 ), picosecond laser pulses. It is shown experimentally that the maximum energies of protons accelerated by sheath fields formed at the rear and at the edges of the target increase with decreasing target size. This is due to the modification of the sheath field by the energetic electrons which spread laterally along the target surface and reflect from the edges. In addition, it is shown that this transverse refluxing of energetic electrons can be used to tailor the spatial-intensity distribution of the proton beam by engineering the shape and size of the target.

  11. Controlling the properties of ultraintense laser-proton sources using transverse refluxing of hot electrons in shaped mass-limited targets

    Energy Technology Data Exchange (ETDEWEB)

    Tresca, O; Carroll, D C; Yuan, X H; Brenner, C M; Coury, M; Gray, R J; Quinn, M N; McKenna, P [SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Aurand, B; Bagnoud, V; Fils, J; Kuehl, T; Zielbauer, B [PHELIX Department, GSI mbH, 64291 Darmstadt (Germany); Li, C; Li, Y T; Lin, X X [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Evans, R G [Plasma Physics Group, Blackett Laboratory, Imperial College, London, SW7 2AZ (United Kingdom); Roth, M [Technical University of Darmstadt, 64289 Darmstadt (Germany); Neely, D, E-mail: paul.mckenna@strath.ac.uk [STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom)

    2011-10-15

    We report on the transverse refluxing of energetic electrons in mass-limited foil targets irradiated with high intensity (1 x 10{sup 19} W cm{sup -2}), picosecond laser pulses. It is shown experimentally that the maximum energies of protons accelerated by sheath fields formed at the rear and at the edges of the target increase with decreasing target size. This is due to the modification of the sheath field by the energetic electrons which spread laterally along the target surface and reflect from the edges. In addition, it is shown that this transverse refluxing of energetic electrons can be used to tailor the spatial-intensity distribution of the proton beam by engineering the shape and size of the target.

  12. Population prevalence and control of cardiovascular risk factors: What electronic medical records tell us

    Directory of Open Access Journals (Sweden)

    Arantxa Catalán-Ramos

    2014-01-01

    Conclusions: Hypertension was the most prevalent cardiovascular risk factor in the Catalan population attended at primary care centers. About two thirds of individuals with hypertension or DM2 were adequately controlled; hypercholesterolemia control was particularly low.

  13. Hot tub folliculitis

    Science.gov (United States)

    ... survives in hot tubs, especially tubs made of wood. Symptoms The first symptom of hot tub folliculitis ... may help prevent the problem. Images Hair follicle anatomy References D'Agata E. Pseudomonas aeruginosa and other ...

  14. Effects of hot electron emission on a low-conductivity tetracyanoethylene polymer layer including studies of the corrugation of the film surface

    International Nuclear Information System (INIS)

    Lorenz, K.L.; Mousa, M.S.

    2003-01-01

    The effect of strong field electron emission (FEE) on a tetracyanoethylene (TCNE) polymer layer was studied by Field Ion Microscopy (FIM) using TCNE and Ne as the imaging gases. The TCNE polymer was formed on each tungsten tip by radical polymerisation before FEE. The FIM images show field emission spots all over the surface of the tip. The FEM images show a random distribution of several field emission areas at the onset of FEE. After sometime at a current of about 1 μA, there is a transition to higher currents at the same voltage, in which the electron emission pattern changes to have only one emitting area. After this transition, two different types of FIM images were observed, depending on the imaging gas that was used. Neon FIM images at low tip voltages show spots in the areas where the electron emission current was greatest, and at much higher voltages these images show emission from other areas with lower surface corrugation. However, the FIM images with TCNE as the imaging gas do not show any differences between the areas with and without electron emission. The FIM images remain as before FEE, which can be explained by the formation of a new polymer by the reaction of the surface layer with the imaging gas. It is assumed that chemically reactive fragments at the polymer/vacuum interface, which are needed for the polymerisation reaction, are formed by pyrolysis and sputtering processes during FEE

  15. The electron temperature and anisotropy in the solar wind. Comparison of the core and halo populations

    Czech Academy of Sciences Publication Activity Database

    Pierrard, V.; Lazar, M.; Poedts, S.; Štverák, Štěpán; Maksimovic, M.; Trávníček, Pavel M.

    2016-01-01

    Roč. 291, č. 7 (2016), s. 2165-2179 ISSN 0038-0938 Institutional support: RVO:68378289 Keywords : solar wind * electron velocity distributions * temperature anisotropy Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.682, year: 2016 http://link.springer.com/article/10.1007/s11207-016-0961-7

  16. The Electron Temperature and Anisotropy in the Solar Wind. Comparison of the Core and Halo Populations

    Czech Academy of Sciences Publication Activity Database

    Pierrard, V.; Lazar, M.; Poedts, S.; Štverák, Štěpán; Maksimovic, M.; Trávníček, Pavel M.

    2016-01-01

    Roč. 291, č. 7 (2016), s. 2165-2179 ISSN 0038-0938 R&D Projects: GA ČR GA15-17490S Institutional support: RVO:67985815 Keywords : solar wind * electron velocity distributions * temperature anisotropy Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.682, year: 2016

  17. Improving Rates of Post-Essure Hysterosalpingography in an Urban Population Using Electronic Tracking Reminders.

    Science.gov (United States)

    Virginia Hu, Yu-Han; Arora, Kavita Shah

    2017-02-01

    To demonstrate the efficacy of electronic reminders for follow-up hysterosalpingography (HSG) after Essure hysteroscopic sterilization in an urban tertiary care hospital obstetrics and gynecology practice. Retrospective cohort study (Canadian Task Force classification II-3). Obstetrics and gynecology practice at a university-affiliated urban tertiary care teaching hospital. Two hundred and fifty patients who underwent Essure hysteroscopic sterilization between June 2011 and July 2014. Implementation of electronic reminders for the office staff. Two hundred and fifty of 259 patients (96.5%) underwent Essure hysteroscopic sterilization and successful placement of coils into bilateral Fallopian tubes. Among these 250 patients, 135 (54%) returned for HSG at 3 months post-Essure as advised at the time of procedure. The use of electronic reminders prompted another 45 patients (18%) to return for HSG, improving the total post-Essure follow-up rate to 72%. Electronic reminders for the office staff of an urban tertiary care hospital's obstetrics and gynecology practice is an effective method for improving the rate of post-Essure HSG. Copyright © 2016 AAGL. Published by Elsevier Inc. All rights reserved.

  18. Modelling Hot Air Balloons.

    Science.gov (United States)

    Brimicombe, M. W.

    1991-01-01

    A macroscopic way of modeling hot air balloons using a Newtonian approach is presented. Misleading examples using a car tire and the concept of hot air rising are discussed. Pressure gradient changes in the atmosphere are used to explain how hot air balloons work. (KR)

  19. High-Intensity Laser-to-Hot-Electron Conversion Efficiency from 1 to 2100 J Using the OMEGA EP Laser System

    Science.gov (United States)

    Nilson, P. M.

    2010-11-01

    Intense laser--matter interactions generate high-current electron beams. The laser-electron conversion efficiency is an important parameter for fast ignition and for developing intense x-ray sources for flash-radiography and x-ray-scattering experiments. These applications may require kilojoules of laser energy focused to greater than 10^18 W/cm^2 with pulse durations of tens of picoseconds. Previous experiments have measured the conversion efficiency with picosecond and subpicosecond laser pulses with energies up to ˜500 J. The research extends conversion-efficiency measurements to 1- to 10-ps laser pulses with energies up to 2100 J using the OMEGA EP Laser System and shows that the conversion efficiency is constant (20±10%) over the entire range The conversion efficiency is measured for interactions with finite-mass, thin-foil targets. A collimated electron jet exits the target rear surface and initiates rapid target charging, causing the majority of laser-accelerated electrons to recirculate (reflux) within the target. The total fast-electron energy is inferred from K-photon spectroscopy. Time-resolved x-ray emission data suggest that electrons are accelerated into the target over the entire laser-pulse duration with approximately constant conversion. This work provides significant insight into high-intensity laser--target interactions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FC02-04ER54789. [4pt] In collaboration with R. Betti, A. A. Solodov (LLE/FSC), R. S. Craxton, J. A. Delettrez, C. Dorrer, L. Gao, P. A. Jaanimagi, J. H. Kelly, B. E. Kruschwitz, D. D. Meyerhofer, J. F. Myatt, T. C. Sangster, C. Stoeckl, W. Theobald, B. Yaakobi, J. D. Zuegel (LLE), A. J. MacKinnon, P. K. Patel (LLNL), K. U. Akli (General Atomics), L. Willingale, K. M. Krushelnick (U. of Michigan).

  20. Hot electron refluxing in the short intense laser pulse interactions with solid targets and its influence on K-alpha radiation

    Czech Academy of Sciences Publication Activity Database

    Horný, Vojtěch; Klimo, O.

    2015-01-01

    Roč. 60, č. 2 (2015), s. 233-237 ISSN 0029-5922. [Kudowa Summer School 2014 "Towards Fusion Energy"/12./. Kudowa Zdrój, 09.06.2014-13.06.2014] R&D Projects: GA MŠk LM2010014 Grant - others:GA MŠk(CZ) LM2010005 Institutional support: RVO:61389021 Keywords : electron recirculation * electron refl uxing * K- alpha radiation * laser–plasma interactions * particle--in-cell simulation Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 0.546, year: 2015 http://www.nukleonika.pl/www/back/full/vol60_2015/v60n2p233f.pdf

  1. Electron cyclotron waves transmission: new approach for the characterization of electron distribution functions in Tokamak hot plasmas; La transmission d`ondes cyclotroniques electroniques: une approche nouvelle pour caracteriser les fonctions de distribution electronique des plasmas chauds de Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Michelot, Y

    1995-10-01

    Fast electrons are one of the basic ingredients of plasma operations in many existing thermonuclear fusion research devices. However, the understanding of fast electrons dynamics during creation and sustainment of the superthermal electrons tail is far for being satisfactory. For this reason, the Electron Cyclotron Transmission (ECT) diagnostic was implemented on Tore Supra tokamak. It consists on a microwave transmission system installed on a vertical chord crossing the plasma center and working in the frequency range 77-109 GHz. Variations of the wave amplitude during the propagation across the plasma may be due to refraction and resonant absorption. For the ECT, the most common manifestation of refraction is a reduction of the received power density with respect to the signal detected in vacuum, due to the spreading and deflection of the wave beam. Wave absorption is observed in the vicinity of the electron cyclotron harmonics and may be due both to thermal plasma and to superthermal electron tails. It has a characteristic frequency dependence due to the relativistic mass variation in the wave-electron resonance condition. This thesis presents the first measurements of: the extraordinary mode optical depth at the third harmonics, the electron temperature from the width of a cyclotron absorption line and the relaxation times of the electron distribution during lower hybrid current drive from the ordinary mode spectral superthermal absorption line at the first harmonic. (J.S.). 175 refs., 110 figs., 9 tabs., 3 annexes.

  2. 16. Hot dense plasma atomic processes

    International Nuclear Information System (INIS)

    Werner, Dappen; Totsuji, H.; Nishii, Y.

    2002-01-01

    This document gathers 13 articles whose common feature is to deal with atomic processes in hot plasmas. Density functional molecular dynamics method is applied to the hydrogen plasma in the domain of liquid metallic hydrogen. The effects of the density gradient are taken into account in both the electronic kinetic energy and the exchange energy and it is shown that they almost cancel with each other, extending the applicability of the Thomas-Fermi-Dirac approximation to the cases where the density gradient is not negligible. Another article reports about space and time resolved M-shell X-ray measurements of a laser-produced gas jet xenon plasma. Plasma parameters have been measured by ion acoustic and electron plasma waves Thomson scattering. Photo-ionization becomes a dominant atomic process when the density and the temperature of plasmas are relatively low and when the plasma is submitted to intense external radiation. It is shown that 2 plasmas which have a very different density but have the same ionization parameters, are found in a similar ionization state. Most radiation hydrodynamics codes use radiative opacity data from available libraries of atomic data. Several articles are focused on the determination of one group Rosseland and Planck mean analytical formulas for several single elements used in inertial fusion targets. In another paper the plasma density effect on population densities, effective ionization, recombination rate coefficients and on emission lines from carbon and Al ions in hot dense plasma, is studied. The last article is devoted to a new atomic model in plasmas that considers the occupation probability of the bound state and free state density in the presence of the plasma micro-field. (A.C.)

  3. Excitation of plasma waves by unstable photoelectron and thermal electron populations on closed magnetic field lines in the Martian ionosphere

    Directory of Open Access Journals (Sweden)

    N. Borisov

    2005-06-01

    Full Text Available It is argued that anisotropic electron pitch angle distributions in the closed magnetic field regions of the Martian ionosphere gives rise to excitation of plasma instabilities. We discuss two types of instabilities that are excited by two different populations of electrons. First, the generation of Langmuir waves by photoelectrons with energies of the order of 10eV is investigated. It is predicted that the measured anisotropy of their pitch angle distribution at the heights z≈400km causes excitation of waves with frequencies f~30kHz and wavelengths λ~30m. Near the terminators the instability of the electrostatic waves with frequencies of the order of or less than the electron gyrofrequency exited by thermal electrons is predicted. The typical frequencies of these waves depend on the local magnitude of the magnetic field and can achieve values f~3-5kHz above strong crustal magnetic fields.

  4. Electronics

    Science.gov (United States)

    2001-01-01

    International Acer Incorporated, Hsin Chu, Taiwan Aerospace Industrial Development Corporation, Taichung, Taiwan American Institute of Taiwan, Taipei, Taiwan...Singapore and Malaysia .5 - 4 - The largest market for semiconductor products is the high technology consumer electronics industry that consumes up...Singapore, and Malaysia . A new semiconductor facility costs around $3 billion to build and takes about two years to become operational

  5. Impact parameter selected nuclear temperatures of hot nuclei from excited state populations for 40Ar+197Au reactions at E/A=25MeV

    International Nuclear Information System (INIS)

    Li Zuyu; He Zhiyong; Duan Limin; Jin Genming; Wu Heyu; Zhang Baoguo; Wen Wanxin; Qi Yujin; Luo Qingzheng; Dai Guangxi; Wang Hongwei

    1997-01-01

    Nuclear temperatures extracted from excited state populations were measured as a function of linear momentum transfer (LMT) for 40 Ar+ 197 Au reactions at 25MeV/nucleon. The emission temperatures increased slightly with increasing linear momentum transfer or decreasing impact parameter. Taking into account the corrections of detection efficiency and sequential feeding from higher-lying states, a temperature of T∼4MeV was deduced for central collisions. For peripheral collisions the extracted temperatures increased with the energy of the particles. (orig.)

  6. Formation of a local Abramis brama orientalis (BERG) population in the zone of hot effluent from the Konakovo hydroelectric power plant

    Energy Technology Data Exchange (ETDEWEB)

    Sappo, G B

    1976-01-01

    Bream (Abramis brama orientalis) inhabitating the part of the Ivan'kovo Reservoir directly exposed to effluent from the Konakovo Hydroelectric Power Plant are smaller and become sexually mature sooner than elsewhere in the reservoir. Moreover, they have longer tail peduncles and anal, thoracic, and dorsal fins than other bream. And, in contrast with the latter, many (20 percent) have two rows of pharyngeal teeth. Thus, the differences in ecological (growth rate, condition factor, spawning times, etc.) and meristic and plastic characters (branched rays, enlarged fins, etc.) as well as in composition of parasites point to the development of an isolated bream population.

  7. Time-resolved two-photon photoemission at the Si(001)-surface. Hot electron dynamics and two-dimensional Fano resonance; Zeitaufgeloeste Zweiphotonen-Photoemission an der Si(001)-Oberflaeche. Dynamik heisser Elektronen und zweidimensionaler Fano-Effekt

    Energy Technology Data Exchange (ETDEWEB)

    Eickhoff, Christian

    2010-10-27

    By combining ultrafast laser excitation with energy-, angle- and time-resolved twophoton photoemission (2PPE), the electronic properties of bulk silicon and the Si(001) surface are investigated in this thesis. A custom-built laser- and UHV-systemequipped with a display type 2D-CCD-detector gives new insight into the relaxation dynamics of excited carriers on a femtosecond timescale. The bandgap between occupied valence bands and unoccupied conduction bands characteristically influences the dynamics of excited electrons in the bulk, as well as in surface states and resonances. For the electron-phonon interaction this leads to the formation of a bottleneck during the relaxation of hot electrons in the conduction band, which maintains the elevated electronic temperature for several picoseconds. During relaxation, excited electrons also scatter from the conduction band into the unoccupied dangling-bond surface state D{sub down}. Depending on the excitation density this surface recombination is dominated by electron-electron- or electron-phonon scattering. The relaxation of the carriers in the D{sub down}-band is again slowed down by the formation of a bottleneck in electron-phonon coupling. Furthermore, the new laser system has allowed detection of the Rydberg-like series of image-potential resonances on the Si(001)-surface. It is shown that the lifetime of these image-potential resonances in front of the semiconducting surface exhibits the same behavior as those in front of metallic surfaces. Moreover the electron-phonon coupling in the first image-potential resonance was investigated and compared to the D{sub down}-surface state. For the first time, Fano-type lineprofiles are demonstrated and analyzed in a 2PPEprocess on a surface. Tuning the photon energy of the pump-laser across the resonance between the occupied dangling-bond state D{sub up}, and the unoccupied image-potential resonance n=1, reveals a clear intensity variation that can be successfully described

  8. Generalized Population Analysis of Three-Center Two-Electron Bonding

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Cooper, D. L.

    2004-01-01

    Roč. 97, č. 6 (2004), s. 1002-1011 ISSN 0020-7608 R&D Projects: GA AV ČR IAA4072006; GA MŠk OC D9.20 Institutional research plan: CEZ:AV0Z4072921 Keywords : multicenter bonding * generalized population analysis * post-Hartree Fock wave functions Subject RIV: CF - Physical ; The oretical Chemistry Impact factor: 1.392, year: 2004

  9. Effectiveness of mobile electronic devices in weight loss among overweight and obese populations: a systematic review and meta-analysis.

    Science.gov (United States)

    Khokhar, Bushra; Jones, Jessica; Ronksley, Paul E; Armstrong, Marni J; Caird, Jeff; Rabi, Doreen

    2014-01-01

    Mobile electronic devices, such as mobile phones and PDAs, have emerged as potentially useful tools in the facilitation and maintenance of weight loss. While RCTs have demonstrated a positive impact of mobile interventions, the extent to which mobile electronic devices are more effective than usual care methods is still being debated. Electronic databases were systematically searched for RCTs evaluating the effectiveness of mobile electronic device interventions among overweight and obese adults. Weighted mean difference for change in body weight was the primary outcome. The search strategy yielded 559 citations and of the 108 potentially relevant studies, six met the criteria. A total of 632 participants were included in the six studies reporting a mean change in body weight. Using a random-effects model, the WMD for the effect of using mobile electronic devices on reduction in body weight was -1.09 kg (95% CI -2.12, -0.05). When stratified by the type of mobile electronic device used, it suggests that interventions using mobile phones were effective at achieving weight loss, WMD = -1.78 kg (95% CI -2.92, -0.63). This systematic review and meta-analysis suggests that mobile electronic devices have the potential to facilitate weight loss in overweight and obese populations, but further work is needed to understand if these interventions have sustained benefit and how we can make these mHealth tools most effective on a large scale. As the field of healthcare increasingly utilizes novel mobile technologies, the focus must not be on any one specific device but on the best possible use of these tools to measure and understand behavior. As mobile electronic devices continue to increase in popularity and the associated technology continues to advance, the potential for the use of mobile devices in global healthcare is enormous. More RCTs with larger sample sizes need to be conducted to look at the cost-effectiveness, technical and financial feasibility of adapting such m

  10. Electronic tagging of green sturgeon reveals population structure and movement among estuaries

    Science.gov (United States)

    Lindley, S.T.; Erickson, D.L.; Moser, M.L.; Williams, G.; Langness, O.P.; McCovey, B.W.; Belchik, M.; Vogel, D.; Pinnix, W.; Kelly, J.T.; Heublein, J.C.; Klimley, A.P.

    2011-01-01

    Green sturgeon Acipenser medirostris spend much of their lives outside of their natal rivers, but the details of their migrations and habitat use are poorly known, which limits our understanding of how this species might be affected by human activities and habitat degradation.We tagged 355 green sturgeon with acoustic transmitters on their spawning grounds and in known nonspawning aggregation sites and examined their movement among these sites and other potentially important locations using automated data-logging hydrophones. We found that green sturgeon inhabit a number of estuarine and coastal sites over the summer, including the Columbia River estuary, Willapa Bay, Grays Harbor, and the estuaries of certain smaller rivers in Oregon, especially the Umpqua River estuary. Green sturgeon from different natal rivers exhibited different patterns of habitat use; most notably, San Francisco Bay was used only by Sacramento River fish, while the Umpqua River estuary was used mostly by fish from the Klamath and Rogue rivers. Earlier work, based on analysis of microsatellite markers, suggested that the Columbia River mixed stock was mainly composed of fish from the Sacramento River, but our results indicate that fish from the Rogue and Klamath River populations frequently use the Columbia River as well. We also found evidence for the existence of migratory contingentswithin spawning populations.Our findings have significant implications for the management of the threatened Sacramento River population of green sturgeon, which migrates to inland waters outside of California where anthropogenic impacts, including fisheries bycatch and water pollution, may be a concern. Our results also illustrate the utility of acoustic tracking to elucidate the migratory behavior of animals that are otherwise difficult to observe. ?? American Fisheries Society 2011.

  11. Digital divide: Use of electronic personal health record by different population groups.

    Science.gov (United States)

    Kim, Eung-Hun; Kim, Yongmin

    2010-01-01

    Personal Health Record (PHR) has been increasingly recognized and actively promoted by the federal government, experts and industry as an important tool for improving healthcare in the U.S. However, the PHR use by patients and its utility have not been studied well. We have evaluated a web-based PHR in multiple locations covering diverse population groups. The study sites included a surgical specialty clinic, a medical specialty clinic, and a mental health clinic at the University of Washington, and a low-income elderly housing facility near Seattle in the state of Washington. The PHR use by the low-income elderly was limited due to poor technical skills and low physical/cognitive abilities. On the other hand, the younger and affluent populations used the web-based PHR much easily and efficiently compared to the older and low-income group. They regarded managing personal health information easy while the older group struggled. As more computer literate individuals age, the next-generation elderly are certain to be more technically skilled than the current generation. Although the reduced physical/cognitive abilities due to aging would still be a challenge, more elderly people will be able to not only use a PHR system but also use it to the full extent to get the maximum benefit.

  12. Photoisomerization around a fulvene double bond: coherent population transfer to the electronic ground state?

    Science.gov (United States)

    Ioffe, Ilya; Dobryakov, Alexander L; Granovsky, Alexander A; Ernsting, Nikolaus P; Lustres, J Luis Pérez

    2011-07-11

    Photoisomerization around a central fulvene-type double bond is known to proceed through a conical intersection at the perpendicular geometry. The process is studied with an indenylidene-dihydropyridine model compound, allowing the use of visible excitation pulses. Transient absorption shows that 1) stimulated emission shifts to the red and loses oscillator strength on a 50 fs timescale, and 2) bleach recovery is highly nonexponential and not affected by solvent viscosity or methyl substitution at the dihydropyridine ring. Quantum-chemical calculations are used to explain point 1 as a result of initial elongation of the central C=C bond with mixing of S(2) and S(1) states. From point 2 it is concluded that internal conversion of S(1)→S(0) does not require torsional motion to the fully perpendicular state. The S(1) population appears to encounter a sink on the torsional coordinate before the conical intersection is reached. Rate equations cannot model the observed ground-state recovery adequately. Instead the dynamics are best described with a strongly damped oscillatory contribution, which could indicate coherent S(1)-S(0) population transfer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Population of Rydberg states by electron capture in fast-ion--atom collisions

    International Nuclear Information System (INIS)

    Burgdoerfer, J.; Dube, L.J.

    1985-01-01

    The l,m-substate distribution in low-lying Rydberg manifolds (nroughly-equal10) following electron capture H + +H(1s)→H(n)+H + is calculated at high velocities (v>1 a.u.) in the continuum-distorted-wave (CDW) approximation. The standard CDW approximation is modified to account for final-state Stark mixing of the Rydberg manifold in the exit channel using the post-collision-interaction model. The influence of multiple-scattering contributions is analyzed and comparison is made with sigma/sub l/m predicted by the Born approximation. We find that the double-scattering contribution, closely connected with the classical Thomas process, becomes visible in the CDW approximation at surprisingly low nonasymptotic velocities

  14. Demonstration of two-electron (shake-up) photoionization and population inversions in the visible and VUV

    International Nuclear Information System (INIS)

    Silfvast, W.T.; Wood, O.R. II; Al-Salameh, D.Y.

    1986-01-01

    The two-electron (shake-up) photoionization process has been shown to be an effective mechanism for producing large population inversions in He/sup +/ with gain at 164 nm and in Ar/sup +/ with gain at 428 and 477 nm and for observing the first autoionizing states in Cd/sup +/. Such a mechanism was recently proposed as an excitation mechanism for a VUV laser in lithium. In each species the rapid excitation and detection using broadband emission from a 30-mJ 100-ps duration laser-produced plasma and a detection system with subnanosecond time resolution were essential in observing these effects. In He, gains of up to 0.8 cm/sup -1/ for durations of 2-4 ns at 164.0 nm on the He-like (n = 3-2) transition in He/sup +/ were measured by comparing the plasma emission from a well-defined volume with and without the presence of a mirror of known reflectivity. The n = 3 upper laser level is pumped not only directly via two-electron photoionization from the neutral ground state but also indirectly (in times of the order of 1-2 ns) via electron collisions from photoionization-pumped higher-lying levels. The decay rate of the photoionization-pumped radiation-trapped lower laser level is increased by a unique process involving absorption of radiation via photoionization of ground state neutral helium atoms

  15. Using Electronic Health Records to Examine Disease Risk in Small Populations: Obesity Among American Indian Children, Wisconsin, 2007-2012.

    Science.gov (United States)

    Tomayko, Emily J; Weinert, Bethany A; Godfrey, Liz; Adams, Alexandra K; Hanrahan, Lawrence P

    2016-02-25

    Tribe-based or reservation-based data consistently show disproportionately high obesity rates among American Indian children, but little is known about the approximately 75% of American Indian children living off-reservation. We examined obesity among American Indian children seeking care off-reservation by using a database of de-identified electronic health records linked to community-level census variables. Data from electronic health records from American Indian children and a reference sample of non-Hispanic white children collected from 2007 through 2012 were abstracted to determine obesity prevalence. Related community-level and individual-level risk factors (eg, economic hardship, demographics) were examined using logistic regression. The obesity rate for American Indian children (n = 1,482) was double the rate among non-Hispanic white children (n = 81,042) (20.0% vs 10.6%, P American Indian children were less likely to have had a well-child visit (55.9% vs 67.1%, P American Indian records (18.3% vs 14.6%, P obesity risk among American Indian children (odds ratio, 1.8; 95% confidence interval, 1.6-2.1) independent of age, sex, economic hardship, insurance status, and geographic designation. An electronic health record data set demonstrated high obesity rates for nonreservation-based American Indian children, rates that had not been previously assessed. This low-cost method may be used for assessing health risk for other understudied populations and to plan and evaluate targeted interventions.

  16. Project-Based Learning and Agile Methodologies in Electronic Courses: Effect of Student Population and Open Issues

    Directory of Open Access Journals (Sweden)

    Marina Zapater

    2013-12-01

    Full Text Available Project-Based Learning (PBL and Agile methodologies have proven to be very interesting instructional strategies in Electronics and Engineering education, because they provide practical learning skills that help students understand the basis of electronics. In this paper we analyze two courses, one belonging to a Master in Electronic Engineering and one to a Bachelor in Telecommunication Engineering that apply Agile-PBL methodologies, and compare the results obtained in both courses with a traditional laboratory course. Our results support previous work stating that Agile-PBL methodologies increase student satisfaction. However, we also highlight some open issues that negatively affect the implementation of these methodologies,such as planning overhead or accidental complexity. Moreover,we show how differences in the student population, mostly related to the time spent on-campus, their commitment to the course or part-time dedication, have an impact on the benefits of Agile-PBL methods. In these cases, Agile-PBL methodologies by themselves are not enough and need to be combined with other techniques to increase student motivation.

  17. The use and perception of electronic cigarettes and snus among the U.S. population.

    Directory of Open Access Journals (Sweden)

    Shu-Hong Zhu

    Full Text Available E-cigarettes have generated controversy in the tobacco control field similar to that of Swedish snus, which came to the U.S. market six years earlier. Some argue that e-cigarettes have great potential to help smokers quit regular cigarettes while others contend they should be banned for lack of safety and efficacy data. This study examined population data from the U.S.A U.S. population survey with a national probability sample (N=10,041 was conducted (February 24 to March 8, 2012, before any major paid advertisement of e-cigarettes appeared on television. Survey respondents were asked if they had heard about e-cigarettes, where they had heard about them, whether they had used e-cigarettes or snus, how often they used them, and why they used them. Responses were weighted to represent the entire U.S. population.A high proportion, 75.4%, reported having heard about e-cigarettes. Television ranked as the number one source of information, followed by "in-person conversation" and "Internet." About 8.1% had tried e-cigarettes, and 1.4% were current users. These rates were twice those of snus (4.3% and 0.8%, respectively. Among current smokers, 32.2% had tried e-cigarettes, and 6.3% were current users. Over 80% of current e-cigarette users were non-daily users. Women were significantly more likely to have tried e-cigarettes than men. Those who had tried e-cigarettes were more likely than those who tried snus to report their products being safer than regular cigarettes (49.9% vs. 10.8%. Almost half (49.5% of current smokers were susceptible to using e-cigarettes in the future.That e-cigarettes have surpassed snus in adoption rate, even before any promotion by major tobacco companies, suggests that the former have tapped into smokers' intuitive preference for potentially harm-reducing products, probably due to the product design. E-cigarette use is likely to increase in the next few years.

  18. Hot Surface Ignition

    OpenAIRE

    Tursyn, Yerbatyr; Goyal, Vikrant; Benhidjeb-Carayon, Alicia; Simmons, Richard; Meyer, Scott; Gore, Jay P.

    2015-01-01

    Undesirable hot surface ignition of flammable liquids is one of the hazards in ground and air transportation vehicles, which primarily occurs in the engine compartment. In order to evaluate the safety and sustainability of candidate replacement fuels with respect to hot surface ignition, a baseline low lead fuel (Avgas 100 LL) and four experimental unleaded aviation fuels recommended for reciprocating aviation engines were considered. In addition, hot surface ignition properties of the gas tu...

  19. Population prevalence and control of cardiovascular risk factors: what electronic medical records tell us.

    Science.gov (United States)

    Catalán-Ramos, Arantxa; Verdú, Jose M; Grau, María; Iglesias-Rodal, Manuel; del Val García, José L; Consola, Alicia; Comin, Eva

    2014-01-01

    To analyze the prevalence, control, and management of hypertension, hypercholesterolemia, and diabetes mellitus type 2 (DM2). Cross-sectional analysis of all individuals attended in the Catalan primary care centers between 2006 and 2009. History of cardiovascular diseases, diagnosis and treatment of hypertension, hypercholesterolemia, DM2, lipid profile, glycemia and blood pressure data were extracted from electronic medical records. Age-standardized prevalence and levels of management and control were estimated. Individuals aged 35-74 years using primary care databases. A total of 2,174,515 individuals were included (mean age 52 years [SD 11], 47% men). Hypertension was the most prevalent cardiovascular risk factor (39% in women, 41% in men) followed by hypercholesterolemia (38% and 40%) and DM2 (12% and 16%), respectively. Diuretics and angiotensin-converting enzyme inhibitors were most often prescribed for hypertension control (women treated). Hypercholesterolemia was controlled (low-density lipoprotein cholesterol women with no history of cardiovascular disease, despite lipid-lowering treatment, primarily (90%) with statins. The percentage of women and men with DM2 and with glycated hemoglobin DM2 were adequately controlled; hypercholesterolemia control was particularly low. Copyright © 2013 Elsevier España, S.L. All rights reserved.

  20. Diagnostic health risk assessment of electronic waste on the general population in developing countries' scenarios

    International Nuclear Information System (INIS)

    Frazzoli, Chiara; Orisakwe, Orish Ebere; Dragone, Roberto; Mantovani, Alberto

    2010-01-01

    E-waste is the generic name for technological waste. Even though aspects related to e-waste environmental pollution and human exposure are known, scientific assessments are missing so far on the actual risks for health sustainability of the general population exposed to e-waste scenarios, such as illicit dumping, crude recycling and improper treatment and disposal. In fact, further to occupational and direct local exposure, e-waste scenarios may impact on the environment-to-food chain, thus eliciting a widespread and repeated exposure of the general population to mixtures of toxicants, mainly toxic chemical elements, polycyclic aromatic hydrocarbons and persistent organic pollutants. In the absence of any clear policy on e-waste flow management, the situation in the e-waste receiver countries may become quite scary; accordingly, here we address a diagnostic risk assessment of health issues potentially elicited by e-waste related mixtures of toxicants. Scientific evidence available so far (mainly from China) is discussed with special attention to the concept of health sustainability, i.e. the poor health burden heritage perpetuated through the mother-to-child dyad. Endocrine disruption and neurotoxicity are specifically considered as examples of main health burden issues relevant to perpetuation through life cycle and across generations; toxicological information are considered along with available data on environmental and food contamination and human internal exposure. The risk from exposure to e-waste related mixtures of toxicants of vulnerable subpopulation like breast-fed infants is given special attention. The diagnostic risk assessment demonstrates how e-waste exposure poses an actual public health emergency, as it may entrain significant health risks also for generations to come. Exposure scenarios as well as specific chemicals of major concern may vary in different contexts; for instance, only limited information is available on e-waste related exposures in

  1. Athermal electron distribution probed by femtosecond multiphoton photoemission from image potential states

    International Nuclear Information System (INIS)

    Ferrini, Gabriele; Giannetti, Claudio; Pagliara, Stefania; Banfi, Francesco; Galimberti, Gianluca; Parmigiani, Fulvio

    2005-01-01

    Image potential states are populated through indirect, scattering-mediated multiphoton absorption induced by femtosecond laser pulses and revealed by single-photon photoemission. The measured effective mass is significantly different from that obtained with direct, resonant population. These features reveal a strong coupling of the electrons residing in the image potential state, outside the solid, with the underlying hot electron population created by the laser pulse. The coupling is mediated by a many-body scattering interaction between the image potential state electrons and bulk electrons in highly excited states

  2. Validation of fragility fractures in primary care electronic medical records: A population-based study.

    Science.gov (United States)

    Martinez-Laguna, Daniel; Soria-Castro, Alberto; Carbonell-Abella, Cristina; Orozco-López, Pilar; Estrada-Laza, Pilar; Nogues, Xavier; Díez-Perez, Adolfo; Prieto-Alhambra, Daniel

    2017-11-28

    Electronic medical records databases use pre-specified lists of diagnostic codes to identify fractures. These codes, however, are not specific enough to disentangle traumatic from fragility-related fractures. We report on the proportion of fragility fractures identified in a random sample of coded fractures in SIDIAP. Patients≥50 years old with any fracture recorded in 2012 (as per pre-specified ICD-10 codes) and alive at the time of recruitment were eligible for this retrospective observational study in 6 primary care centres contributing to the SIDIAP database (www.sidiap.org). Those with previous fracture/s, non-responders, and those with dementia or a serious psychiatric disease were excluded. Data on fracture type (traumatic vs fragility), skeletal site, and basic patient characteristics were collected. Of 491/616 (79.7%) patients with a registered fracture in 2012 who were contacted, 331 (349 fractures) were included. The most common fractures were forearm (82), ribs (38), and humerus (32), and 225/349 (64.5%) were fragility fractures, with higher proportions for classic osteoporotic sites: hip, 91.7%; spine, 87.7%; and major fractures, 80.5%. This proportion was higher in women, the elderly, and patients with a previously coded diagnosis of osteoporosis. More than 4 in 5 major fractures recorded in SIDIAP are due to fragility (non-traumatic), with higher proportions for hip (92%) and vertebral (88%) fracture, and a lower proportion for fractures other than major ones. Our data support the validity of SIDIAP for the study of the epidemiology of osteoporotic fractures. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Reumatología y Colegio Mexicano de Reumatología. All rights reserved.

  3. Geographical distribution of hot flash frequencies: considering climatic influences.

    Science.gov (United States)

    Sievert, Lynnette Leidy; Flanagan, Erin K

    2005-10-01

    Laboratory studies suggest that hot flashes are triggered by small elevations in core body temperature acting within a reduced thermoneutral zone, i.e., the temperature range in which a woman neither shivers nor sweats. In the present study, it was hypothesized that women in different populations develop climate-specific thermoneutral zones, and ultimately, population-specific frequencies of hot flashes at menopause. Correlations were predicted between hot flash frequencies and latitude, elevation, and annual temperatures. Data on hot flash frequencies were drawn from 54 studies. Pearson correlation analyses and simple linear regressions were applied, first using all studies, and second using a subset of studies that included participants only to age 60 (n = 36). Regressions were repeated with all studies, controlling for method of hot flash assessment. When analyses were restricted to studies that included women up to age 60, average temperature of the coldest month was a significant predictor of hot flash frequency (P hottest and coldest temperatures was also a significant predictor (P coldest month, difference between hottest and coldest temperatures, and mean annual temperature were significant predictors of hot flash frequency. Women reported fewer hot flashes in warmer temperatures, and more hot flashes with increasing seasonality. These results suggest that acclimatization to coldest temperatures or sensitivity to seasonality may explain part of the population variation in hot flash frequency.

  4. Childhood obesity trends from primary care electronic health records in England between 1994 and 2013: population-based cohort study.

    Science.gov (United States)

    van Jaarsveld, Cornelia H M; Gulliford, Martin C

    2015-03-01

    This study aimed to use primary care electronic health records to evaluate the prevalence of overweight and obesity in 2-15-year-old children in England and compare trends over the last two decades. Cohort study of primary care electronic health records. 375 general practices in England that contribute to the UK Clinical Practice Research Datalink. Individual participants were sampled if they were aged between 2 and 15 years during the period 1994-2013 and had one or more records of body mass index (BMI). Prevalence of overweight (including obesity) was defined as a BMI equal to or greater than the 85th centile of the 1990 UK reference population. Data were analysed for 370 544 children with 507 483 BMI records. From 1994 to 2003, the odds of overweight and obesity increased by 8.1% per year (95% CI 7.2% to 8.9%) compared with 0.4% (-0.2% to 1.1%) from 2004 to 2013. Trends were similar for boys and girls, but differed by age groups, with prevalence stabilising in 2004 to 2013 in the younger (2-10 year) but not older (11-15 year) age group, where rates continued to increase. Primary care electronic health records in England may provide a valuable resource for monitoring obesity trends. More than a third of UK children are overweight or obese, but the prevalence of overweight and obesity may have stabilised between 2004 and 2013. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  5. Physics of dust grains in hot gas

    International Nuclear Information System (INIS)

    Draine, B.T.; Salpeter, E.E.

    1979-01-01

    Charging of dust grains in hot (10 4 --10 9 K) plasma is studied, including photoelectron and secondary electron emission, field emission, and transmission of electrons and ions through the grain; resulting grain potentials are (for T > or approx. = 10 5 K) considerably smaller in magnitude than found by Burke and Silk. Even so, large electrostatic stresses can cause ion field emission and rapid destruction of small grains in very hot gas. Rapid rotation can also disrupt small grains, but damping (by microwave emission) usually limits the centrifugal stress to acceptable values for plasma densities n/sub H/ -3 . Sputtering rates are estimated for grains in hot gas, based upon a semiempirical fit to experimental data. Predicted sputtering rates for possible grain constituents are similar to estimates by Barlow, but in some cases differ significantly. Useful approximation formulae are given for the drag forces acting on a grain with arbitrary Mach number

  6. Accuracy of administratively-assigned ancestry for diverse populations in an electronic medical record-linked biobank.

    Directory of Open Access Journals (Sweden)

    Jacob B Hall

    Full Text Available Recently, the development of biobanks linked to electronic medical records has presented new opportunities for genetic and epidemiological research. Studies based on these resources, however, present unique challenges, including the accurate assignment of individual-level population ancestry. In this work we examine the accuracy of administratively-assigned race in diverse populations by comparing assigned races to genetically-defined ancestry estimates. Using 220 ancestry informative markers, we generated principal components for patients in our dataset, which were used to cluster patients into groups based on genetic ancestry. Consistent with other studies, we find a strong overall agreement (Kappa  = 0.872 between genetic ancestry and assigned race, with higher rates of agreement for African-descent and European-descent assignments, and reduced agreement for Hispanic, East Asian-descent, and South Asian-descent assignments. These results suggest caution when selecting study samples of non-African and non-European backgrounds when administratively-assigned race from biobanks is used.

  7. Application of the methods of scanning electron microscopy and X-ray microanalysis for 'hot particles' detection in the human lungs formed as a result of the Chernobyl accident

    International Nuclear Information System (INIS)

    Reva, Yu.P.; Portyanko, N.M.; Ivanov, A.S.; Chuchalin, A.G.

    1993-01-01

    The up-to-date approaches to 'hot particles' studying were applied in this investigation. A complex of morphological and physical-chemical methods make it possible to detect and identify the 'hot particles' in the autopsy material of the lungs from 2 males at the age 27 and 25, who participated in the liquidation of Chernobyl katastrophe consequences in 1986. The elemental and isotope content of these particles was the same as that of the 'hot particles' detected in the zone of the katstrophe. The results obtained make it possible to suppose that the 'hot particles' have been inhaled and existed for a long time in the human bodies. On the basis of these data we suppose that the 'hot particle' are the cause of respiratory and other systems disorders

  8. Study of diffused particles by an electron cyclotron-resonance ions source plasma

    International Nuclear Information System (INIS)

    Klein, J.P.

    1995-01-01

    A double electrostatic analyser has been built mainly to study the loss cone electron population. The analysis of the ions can help to determine the plasma potential. The possibility of applying two analysing potentials along the extraction decaying magnetic filed allowed us to determine the anisotropy of the electron distribution function, of parallel temperature Tpar and perpendicular temperature Tper outside the plasma. The Tpar temperature remains constant at around 10 eV when Tper increases from 30 eV to 150 eV with improved confinement. The electron cyclotron heating provides mainly perpendicular energy to the electrons. The perpendicular electron energy is then converted to parallel energy predominantly by electron ion collisions and leave the plasma with a frequency depending on v per -3 . Taking a Maxwellian function of temperature T per cent to describe the electron function distribution f cent (v per ) in the center of the plasma is in line with the experimental electron characteristics obtained with a single electrostatic potential. Temperatures of 2 keV have been reached at 10 Ghz and 6 keV at 18 Ggz. Measurements of density and diamagnetism can complete the description of this warm population: the warm electrons dominate in number but leave the plasma quicker than the very hot electron population (analysed with the X ray diagnostic). For this reason the energy density of warm electrons is less than that of the very hot population by warm electrons consume most of the injected rf power. (author). 52 refs., 100 figs

  9. Microstructure and Mechanical Properties of Long Ti-6Al-4V Rods Additively Manufactured by Selective Electron Beam Melting Out of a Deep Powder Bed and the Effect of Subsequent Hot Isostatic Pressing

    Science.gov (United States)

    Lu, S. L.; Tang, H. P.; Ning, Y. P.; Liu, N.; StJohn, D. H.; Qian, M.

    2015-09-01

    An array of eight long Ti-6Al-4V rods (diameter: 12 mm; height: 300 mm) have been additively manufactured, vertically and perpendicular to the powder bed, by selective electron beam melting (SEBM). The purpose was to identify and understand the challenges of fabricating Ti-6Al-4V samples or parts from a deep powder bed (more than 200-mm deep) by SEBM and the necessity of applying post heat treatment. The resulting microstructure and mechanical properties of these Ti-6Al-4V rods were characterized along their building ( i.e., axial) direction by dividing each rod into three segments (top, middle, and bottom), both before ( i.e., as-built) and after hot isostatic pressing (HIP). The as-built microstructure of each rod was inhomogeneous; it was coarsest in the top segment, which showed a near equilibrium α- β lamellar structure, and finest in the bottom segment, which featured a non-equilibrium mixed structure. The tensile properties varied along the rod axis, especially the ductility, but all tensile properties met the requirements specified by ASTM F3001-14. HIP increased the relative density from 99.03 pct of the theoretical density (TD) to 99.90 pct TD and homogenized the microstructure thereby leading to highly consistent tensile properties along the rod axis. The temperature of the stainless steel substrate used in the powder bed was monitored. The as-built inhomogeneous microstructure is attributed to the temperature gradient in the deep powder bed. Post heat treatment is thus necessary for Ti-6Al-4V samples or parts manufactured from a deep powder bed by SEBM. This differs from the additive manufacturing of small samples or parts from a shallow powder bed (less than 100-mm deep) by SEBM.

  10. Hot Weather Tips

    Science.gov (United States)

    ... the person plenty of water and fruit or vegetable juice even if they say they’re not thirsty. No alcohol, coffee or tea. Seek medical help if you suspect dehydration. Light meals: Avoid hot, heavy meals and don’ ...

  11. China's 'Hot Money' Problems

    National Research Council Canada - National Science Library

    Martin, Michael F; Morrison, Wayne M

    2008-01-01

    .... The recent large inflow of financial capital into China, commonly referred to as "hot money," has led some economists to warn that such flows may have a destabilizing effect on China's economy...

  12. ESA uncovers Geminga's `hot spot'

    Science.gov (United States)

    2004-07-01

    16 July 2004 Astronomers using ESA’s X-ray observatory XMM-Newton have detected a small, bright ‘hot spot’ on the surface of the neutron star called Geminga, 500 light-years away. The hot spot is the size of a football field and is caused by the same mechanism producing Geminga’s X-ray tails. This discovery identifies the missing link between the X-ray and gamma-ray emission from Geminga. hi-res Size hi-res: 1284 kb Credits: ESA, P. Caraveo (IASF, Milan) Geminga's hot spot This figure shows the effects of charged particles accelerated in the magnetosphere of Geminga. Panel (a) shows an image taken with the EPIC instrument on board the XMM-Newton observatory. The bright tails, made of particles kicked out by Geminga’s strong magnetic field, trail the neutron star as it moves about in space. Panel (b) shows how electrically charged particles interact with Geminga’s magnetic field. For example, if electrons (blue) are kicked out by the star, positrons (in red) hit the star’s magnetic poles like in an ‘own goal’. Panel (c) illustrates the size of Geminga’s magnetic field (blue) compared to that of the star itself at the centre (purple). The magnetic field is tilted with respect to Geminga’s rotation axis (red). Panel (d) shows the magnetic poles of Geminga, where charged particles hit the surface of the star, creating a two-million degrees hot spot, a region much hotter than the surroundings. As the star spins on its rotation axis, the hot spot comes into view and then disappears, causing the periodic colour change seen by XMM-Newton. An animated version of the entire sequence can be found at: Click here for animated GIF [low resolution, animated GIF, 5536 KB] Click here for AVI [high resolution, AVI with DIVX compression, 19128 KB] hi-res Size hi-res: 371 kb Credits: ESA, P. Caraveo (IASF, Milan) Geminga's hot spot, panel (a) Panel (a) shows an image taken with the EPIC instrument on board the XMM-Newton observatory. The bright tails, made of

  13. Extracting hot carriers from photoexcited semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang

    2014-12-10

    This research program addresses a fundamental question related to the use of nanomaterials in solar energy -- namely, whether semiconductor nanocrystals (NCs) can help surpass the efficiency limits, the so-called “Shockley-Queisser” limit, in conventional solar cells. In these cells, absorption of photons with energies above the semiconductor bandgap generates “hot” charge carriers that quickly “cool” to the band edges before they can be utilized to do work; this sets the solar cell efficiency at a limit of ~31%. If instead, all of the energy of the hot carriers could be captured, solar-to-electric power conversion efficiencies could be increased, theoretically, to as high as 66%. A potential route to capture this energy is to utilize semiconductor nanocrystals. In these materials, the quasi-continuous conduction and valence bands of the bulk semiconductor become discretized due to confinement of the charge carriers. Consequently, the energy spacing between the electronic levels can be much larger than the highest phonon frequency of the lattice, creating a “phonon bottleneck” wherein hot-carrier relaxation is possible via slower multiphonon emission. For example, hot-electron lifetimes as long as ~1 ns have been observed in NCs grown by molecular beam epitaxy. In colloidal NCs, long lifetimes have been demonstrated through careful design of the nanocrystal interfaces. Due to their ability to slow electronic relaxation, semiconductor NCs can in principle enable extraction of hot carriers before they cool to the band edges, leading to more efficient solar cells.

  14. Nonlinear electron acoustic structures generated on the high-potential side of a double layer

    Directory of Open Access Journals (Sweden)

    R. Pottelette

    2009-04-01

    Full Text Available High-time resolution measurements of the electron distribution function performed in the auroral upward current region reveals a large asymmetry between the low- and high-potential sides of a double-layer. The latter side is characterized by a large enhancement of a locally trapped electron population which corresponds to a significant part (~up to 30% of the total electron density. As compared to the background hot electron population, this trapped component has a very cold temperature in the direction parallel to the static magnetic field. Accordingly, the differential drift between the trapped and background hot electron populations generates high frequency electron acoustic waves in a direction quasi-parallel to the magnetic field. The density of the trapped electron population can be deduced from the frequency where the electron acoustic spectrum maximizes. In the auroral midcavity region, the electron acoustic waves may be modulated by an additional turbulence generated in the ion acoustic range thanks to the presence of a pre-accelerated ion beam located on the high-potential side of the double layer. Electron holes characterized by bipolar pulses in the electric field are sometimes detected in correlation with these electron acoustic wave packets.

  15. Introduction of hot cell facility in research center Rez - Poster

    International Nuclear Information System (INIS)

    Petrickova, A.; Srba, O.; Miklos, M.; Svoboda, P.

    2015-01-01

    This poster presents the hot cell facility which is being constructed as part of the SUSEN project at the Rez research center (Czech Republic). Within this project a new complex of 10 hot cells and one semi-hot cell will be built. There will be 8 gamma hot cells and 2 alpha hot cells. In each hot cell a hermetic, removable box made of stainless steel will home different type of devices. The hot cells and semi hot cell will be equipped with devices for processing samples (cutting, welding, drilling, machining) as well as equipment for testing (sample preparation area, stress testing machine, fatigue machine, electromechanical creep machine, high frequency resonance pulsator...) and equipment for studying material microstructure (nano-indenter with nano-scratch tester and scanning electron microscope). An autoclave with water loop, installed in a cell will allow mechanical testing in control environment of water, pressure and temperature. A scheme shows the equipment of each cell. This hot laboratory will be able to cover all the process to study radioactive materials: receiving the material, the preparation of the samples, mechanical testing and microstructure observation. Our hot cells will be close to the research nuclear reactor LVR-15 and new irradiation facility (high irradiation by cobalt source) is planned to be built within the SUSEN project

  16. Energy flux of hot atoms

    International Nuclear Information System (INIS)

    Wotzak, G.P.; Kostin, M.D.

    1976-01-01

    The process in which hot atoms collide with thermal atoms of a gas, transfer kinetic energy to them, and produce additional hot atoms is investigated. A stochastic method is used to obtain numerical results for the spatial and time dependent energy flux of hot atoms in a gas. The results indicate that in hot atom systems a front followed by an intense energy flux of hot atoms may develop

  17. Hot Flow Anomaly formation by magnetic deflection

    International Nuclear Information System (INIS)

    Onsager, T.G.; Thomsen, M.F.; Winske, D.

    1990-01-01

    Hot Flow Anomalies (HFAs) are localized plasma structures observed in the solar wind and magnetosheath near the Earth's quasi-parallel bow shock. The authors present 1-D hybrid computer simulations illustrating a formation mechanism for HFAs in which the single, hot, ion population results from a spatial separation of two counterstreaming ion beams. The higher-density, cooler regions are dominated by the background (solar wind) ions, and the lower-density, hotter, internal regions are dominated by the beam ions. The spatial separation of the beam and background is caused by the deflection of the ions in large amplitude magnetic fields which are generated by ion/ion streaming instabilities

  18. HotRegion: a database of predicted hot spot clusters.

    Science.gov (United States)

    Cukuroglu, Engin; Gursoy, Attila; Keskin, Ozlem

    2012-01-01

    Hot spots are energetically important residues at protein interfaces and they are not randomly distributed across the interface but rather clustered. These clustered hot spots form hot regions. Hot regions are important for the stability of protein complexes, as well as providing specificity to binding sites. We propose a database called HotRegion, which provides the hot region information of the interfaces by using predicted hot spot residues, and structural properties of these interface residues such as pair potentials of interface residues, accessible surface area (ASA) and relative ASA values of interface residues of both monomer and complex forms of proteins. Also, the 3D visualization of the interface and interactions among hot spot residues are provided. HotRegion is accessible at http://prism.ccbb.ku.edu.tr/hotregion.

  19. Dose-specific adverse drug reaction identification in electronic patient records: temporal data mining in an inpatient psychiatric population.

    Science.gov (United States)

    Eriksson, Robert; Werge, Thomas; Jensen, Lars Juhl; Brunak, Søren

    2014-04-01

    Data collected for medical, filing and administrative purposes in electronic patient records (EPRs) represent a rich source of individualised clinical data, which has great potential for improved detection of patients experiencing adverse drug reactions (ADRs), across all approved drugs and across all indication areas. The aim of this study was to take advantage of techniques for temporal data mining of EPRs in order to detect ADRs in a patient- and dose-specific manner. We used a psychiatric hospital's EPR system to investigate undesired drug effects. Within one workflow the method identified patient-specific adverse events (AEs) and links these to specific drugs and dosages in a temporal manner, based on integration of text mining results and structured data. The structured data contained precise information on drug identity, dosage and strength. When applying the method to the 3,394 patients in the cohort, we identified AEs linked with a drug in 2,402 patients (70.8 %). Of the 43,528 patient-specific drug substances prescribed, 14,736 (33.9 %) were linked with AEs. From these links we identified multiple ADRs (p patient population, larger doses were prescribed to sedated patients than non-sedated patients; five antipsychotics [corrected] exhibited a significant difference (p<0.05). Finally, we present two cases (p < 0.05) identified by the workflow. The method identified the potentially fatal AE QT prolongation caused by methadone, and a non-described likely ADR between levomepromazine and nightmares found among the hundreds of identified novel links between drugs and AEs (p < 0.05). The developed method can be used to extract dose-dependent ADR information from already collected EPR data. Large-scale AE extraction from EPRs may complement or even replace current drug safety monitoring methods in the future, reducing or eliminating manual reporting and enabling much faster ADR detection.

  20. Estimation method for volumes of hot spots created by heavy ions

    International Nuclear Information System (INIS)

    Kanno, Ikuo; Kanazawa, Satoshi; Kajii, Yuji

    1999-01-01

    As a ratio of volumes of hot spots to cones, which have the same lengths and bottom radii with the ones of hot spots, a simple and convenient method for estimating the volumes of hot spots is described. This calculation method is useful for the study of damage producing mechanism in hot spots, and is also convenient for the estimation of the electron-hole densities in plasma columns created by heavy ions in semiconductor detectors. (author)

  1. Remarks on theoretical hot-atom chemistry

    International Nuclear Information System (INIS)

    Inokuti, Mitio

    1993-01-01

    The publication of the 'Handbook of Hot Atom Chemistry', following the earlier volume 'Recent Trend and Application', was a major milestone in physical chemistry. Theoretical treatments of hot atom chemistry must address two classes of problems. The first class concerns the individual collisions of hot atoms with other atoms or molecules. The second class concerns the description of the consequences of the many collisions of hot atoms and their chemical environment. Most of the remarks pertain to the problems of the first class. The central issue is the adiabaticity of nuclear motions versus electronic motions. To be precise, any atomic core motion should be mentioned rather than pure nuclear motion, because tightly bound core electrons are largely irrelevant to the chemistry. When nuclear motions are sufficiently slow, or for other reasons that can be regarded as adiabatic, the collision problem is basically straightforward, therefore, interatomic and intermolecular forces can be assumed, and their consequences for nuclear motions are calculable in principle. In the case of non-adiabaticity being important, much more difficult problems arise, and it is briefly discussed, and the work by Phelps is cited. (K.I.)

  2. The multiwavelength spectrum of NGC 3115: hot accretion flow properties

    Science.gov (United States)

    Almeida, Ivan; Nemmen, Rodrigo; Wong, Ka-Wah; Wu, Qingwen; Irwin, Jimmy A.

    2018-04-01

    NGC 3115 is the nearest galaxy hosting a billion solar mass black hole and is also a low-luminosity active galactic nucleus (LLAGN). X-ray observations of this LLAGN are able to spatially resolve the hot gas within the sphere of gravitational influence of the supermassive black hole. These observations make NGC 3115 an important test bed for black hole accretion theory in galactic nuclei since they constrain the outer boundary conditions of the hot accretion flow. We present a compilation of the multiwavelength spectral energy distribution (SED) of the nucleus of NGC 3115 from radio to X-rays. We report the results from modelling the observed SED with radiatively inefficient accretion flow (RIAF) models. The radio emission can be well-explained by synchrotron emission from the RIAF without the need for contribution from a relativistic jet. We obtain a tight constraint on the RIAF density profile, ρ (r) ∝ r^{-0.73 _{-0.02} ^{+0.01}}, implying that mass-loss through subrelativistic outflows from the RIAF is significant. The lower frequency radio observation requires the synchrotron emission from a non-thermal electron population in the RIAF, similarly to Sgr A*.

  3. Selective ultrafast probing of transient hot chemisorbed and precursor states of CO on Ru(0001)

    DEFF Research Database (Denmark)

    Beye, M.; Anniyev, T.; Coffee, R.

    2013-01-01

    to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical...... (2013)SCIEAS0036-8075] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due...

  4. Transport of energetic electrons in a magnetically expanding helicon double layer plasma

    International Nuclear Information System (INIS)

    Takahashi, Kazunori; Charles, Christine; Boswell, Rod; Cox, Wes; Hatakeyama, Rikizo

    2009-01-01

    Peripheral magnetic field lines extending from the plasma source into the diffusion chamber are found to separate two regions of Maxwellian electron energy probability functions: the central, ion-beam containing region with an electron temperature of 5 eV, and region near the chamber walls with electrons at 3 eV. Along the peripheral field lines a bi-Maxwellian population with a hot tail at 9 eV is shown to both originate from electrons in the source traveling downstream across the double layer and correspond to a local maximum in ion and electron densities.

  5. History of hot flashes and aortic calcification among postmenopausal women.

    Science.gov (United States)

    Thurston, Rebecca C; Kuller, Lewis H; Edmundowicz, Daniel; Matthews, Karen A

    2010-03-01

    Menopausal hot flashes are considered largely a quality-of-life issue. However, emerging research also links hot flashes to cardiovascular risk. In some investigations, this risk is particularly apparent among women using hormone therapy. The aim of this study was to determine whether a longer history of reported hot flashes over the study period was associated with greater aortic and coronary artery calcification. Interactions with hormone therapy use were examined in an exploratory fashion. Participants included 302 women participating in the Healthy Women Study, a longitudinal study of cardiovascular risk during perimenopause and postmenopause, which was initiated in 1983. Hot flashes (any/none) were assessed when women were 1, 2, 5, and 8 years postmenopausal. Electron beam tomography measures of coronary artery calcification and aortic calcification were completed in 1997-2004. Associations between the number of visits with report of hot flashes, divided by the number of visits attended, and aortic or coronary artery calcification (transformed) were examined in linear regression models. Interactions by hormone therapy use were evaluated. Among women using hormone therapy, a longer history of reported hot flashes was associated with increased aortic calcification, controlling for traditional cardiovascular risk factors (b = 2.87, SE = 1.21, P history of hot flashes and coronary artery calcification. Among postmenopausal women using hormone therapy, a longer history of reported hot flashes measured prospectively was associated with increased aortic calcification, controlling for traditional cardiovascular risk factors. Hot flashes may signal adverse cardiovascular changes among certain postmenopausal women.

  6. Multifragmentation of hot nuclei

    International Nuclear Information System (INIS)

    Tamain, B.

    1990-10-01

    It is difficult to deposit a large amount (∼ 1 Gev) of excitation energy into a nucleus. And if one wants to deposit large excitation energy values, the best way consists of shooting a given target nucleus with several nucleons, which can be achieved by using intermediate energy (10-100 MeV/nucleon) heavy ions. Such very excited objects were named hot nuclei. The study of hot nuclei has been undertaken only for 7 years because intermediate energy heavy ion facilities were not available before. The game is then to determine the decay properties of such nuclei, their limits of existence. Their study is connected with general properties of nuclear matter: namely its equation of state. Of special interest, is the onset of a new decay mechanism: multifragmentation, which is the non-sequential disassembly of a hot nucleus into several light nuclei (often called intermediate-mass fragments or IMF) or particles. This paper, shows how this mechanism can reflect fundamental properties of nuclear matter, but also how its experimental signature is difficult to establish. Multifragmentation has also been studied by using very energetic projectiles (protons and heavy ions) in the relativistic or ultra-relativistic region. The multifragmentation question of hot nuclei is far from being solved. One knows that IMF production increases when the excitation energy brought into a system is strongly increased, but very little is known about the mechanisms involved and a clear onset for multifragmentation is not established

  7. Mechanical shielded hot cell

    International Nuclear Information System (INIS)

    Higgy, H.R.; Abdel-Rassoul, A.A.

    1983-01-01

    A plan to erect a mechanical shielded hot cell in the process hall of the Radiochemical Laboratory at Inchas is described. The hot cell is designed for safe handling of spent fuel bundles, from the Inchas reactor, and for dismantling and cutting the fuel rods in preparation for subsequent treatment. The biological shielding allows for the safe handling of a total radioactivity level up to 10,000 MeV-Ci. The hot cell consists of an α-tight stainless-steel box, connected to a γ-shielded SAS, through an air-lock containing a movable carriage. The α-box is tightly connected with six dry-storage cavities for adequate storage of the spent fuel bundles. Both the α-box, with the dry-storage cavities, and the SAS are surrounded by 200-mm thick biological lead shielding. The α-box is equipped with two master-slave manipulators, a lead-glass window, a monorail crane and Padirac and Minirag systems. The SAS is equipped with a lead-glass window, tong manipulator, a shielded pit and a mechanism for the entry of the spent fuel bundle. The hot cell is served by adequate ventilation and monitoring systems. (author)

  8. Electron acoustic nonlinear structures in planetary magnetospheres

    Science.gov (United States)

    Shah, K. H.; Qureshi, M. N. S.; Masood, W.; Shah, H. A.

    2018-04-01

    In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized ( r , q ) distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized ( r , q ) distribution. It has been found that the flatness parameter r , tail parameter q , and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.

  9. HOT GAS HALOS IN EARLY-TYPE FIELD GALAXIES

    International Nuclear Information System (INIS)

    Mulchaey, John S.; Jeltema, Tesla E.

    2010-01-01

    We use Chandra and XMM-Newton to study the hot gas content in a sample of field early-type galaxies. We find that the L X -L K relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. The low hot gas content of field galaxies with L K ∼ * suggests that internal processes such as supernovae-driven winds or active galactic nucleus feedback expel hot gas from low-mass galaxies. Such mechanisms may be less effective in groups and clusters where the presence of an intragroup or intracluster medium can confine outflowing material. In addition, galaxies in groups and clusters may be able to accrete gas from the ambient medium. While there is a population of L K ∼ * galaxies in groups and clusters that retain hot gas halos, some galaxies in these rich environments, including brighter galaxies, are largely devoid of hot gas. In these cases, the hot gas halos have likely been removed via ram pressure stripping. This suggests a very complex interplay between the intragroup/intracluster medium and hot gas halos of galaxies in rich environments, with the ambient medium helping to confine or even enhance the halos in some cases and acting to remove gas in others. In contrast, the hot gas content of more isolated galaxies is largely a function of the mass of the galaxy, with more massive galaxies able to maintain their halos, while in lower mass systems the hot gas escapes in outflowing winds.

  10. Childhood obesity trends from primary care electronic health records in England between 1994 and 2013: population-based cohort study

    NARCIS (Netherlands)

    Jaarsveld, C.H.M. van; Gulliford, M.C.

    2015-01-01

    OBJECTIVE: This study aimed to use primary care electronic health records to evaluate the prevalence of overweight and obesity in 2-15-year-old children in England and compare trends over the last two decades. DESIGN: Cohort study of primary care electronic health records. SETTING: 375 general

  11. Hot Deformation Behavior of Hot-Extruded AA7175 Through Hot Torsion Tests.

    Science.gov (United States)

    Lee, Se-Yeon; Jung, Taek-Kyun; Son, Hyeon-Woo; Kim, Sang-Wook; Son, Kwang-Tae; Choi, Ho-Joon; Oh, Sang-Ho; Lee, Ji-Woon; Hyun, Soong-Keun

    2018-03-01

    The hot deformation behavior of hot-extruded AA7175 was investigated with flow curves and processing maps through hot torsion tests. The flow curves and the deformed microstructures revealed that dynamic recrystallization (DRX) occurred in the hot-extruded AA7175 during hot working. The failure strain was highest at medium temperature. This was mainly influenced by the dynamic precipitation of fine rod-shaped MgZn2. The processing map determined the optimal deformation condition for the alloy during hot working.

  12. Software Simulation of Hot Tearing

    DEFF Research Database (Denmark)

    Andersen, S.; Hansen, P.N.; Hattel, Jesper Henri

    1999-01-01

    The brittleness of a solidifying alloy in a temperature range near the solidus temperature has been recognised since the fifties as the mechanism responsible for hot tearing. Due to this brittlenes, the metal will crack under even small amounts of strain in that temperature range. We see these hot...... tears in castings close to hot centres, where the level of strain is often too high.Although the hot tearing mechanism is well understood, until now it has been difficult to do much to reduce the hot tearing tendency in a casting. In the seventies, good hot tearing criteria were developed by considering...... the solidification rate and the strain rate of the hot tear prone areas. But, until recently it was only possible to simulate the solidification rate, so that the criteria could not be used effectively.Today, with new software developments, it is possible to also simulate the strain rate in the hot tear prone areas...

  13. Hot Fuel Examination Facility (HFEF)

    Data.gov (United States)

    Federal Laboratory Consortium — The Hot Fuel Examination Facility (HFEF) is one of the largest hot cells dedicated to radioactive materials research at Idaho National Laboratory (INL). The nation's...

  14. Effects of electron pressure anisotropy on current sheet configuration

    International Nuclear Information System (INIS)

    Artemyev, A. V.; Angelopoulos, V.; Runov, A.; Vasko, I. Y.

    2016-01-01

    Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. We find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.

  15. Some recent results from European sounding rocket and satellite observations of the hot magnetospheric plasma

    International Nuclear Information System (INIS)

    Hultqvist, B.

    1979-03-01

    A brief summary of some recent results from European studies of the hot magnetospheric plasma is presented. The material is organized in four main sections: 1) Observations of keV auroral electrons. 2) Observation of the hot ion component of the magnetospheric plasma. 3) Sudden changes of the distribution of the hot plasma in the dayside magnetosphere. 4) Banded electron cyclotron harmonic instability in the magnetosphere - a first comparison of theory and experiment. (E.R.)

  16. Hot Charge Carrier Transmission from Plasmonic Nanostructures

    Science.gov (United States)

    Christopher, Phillip; Moskovits, Martin

    2017-05-01

    Surface plasmons have recently been harnessed to carry out processes such as photovoltaic current generation, redox photochemistry, photocatalysis, and photodetection, all of which are enabled by separating energetic (hot) electrons and holes—processes that, previously, were the domain of semiconductor junctions. Currently, the power conversion efficiencies of systems using plasmon excitation are low. However, the very large electron/hole per photon quantum efficiencies observed for plasmonic devices fan the hope of future improvements through a deeper understanding of the processes involved and through better device engineering, especially of critical interfaces such as those between metallic and semiconducting nanophases (or adsorbed molecules). In this review, we focus on the physics and dynamics governing plasmon-derived hot charge carrier transfer across, and the electronic structure at, metal-semiconductor (molecule) interfaces, where we feel the barriers contributing to low efficiencies reside. We suggest some areas of opportunity that deserve early attention in the still-evolving field of hot carrier transmission from plasmonic nanostructures to neighboring phases.

  17. Hot subluminous star: HDE 283048

    International Nuclear Information System (INIS)

    Laget, M.; Vuillemin, A.; Parsons, S.B.; Henize, K.G.; Wray, J.D.

    1978-01-01

    The star HDE 283048, located at α = 3/sup h/50/sup m/.3, delta = +25 0 36', shows a strong ultraviolet continuum. Ground-based observations indicate a hot-dominated composite spectrum. Several lines of evidence suggest that the hot component is a hot subdwarf. 2 figures

  18. (RN) pair production by photons in a hot Maxwellian plasma

    International Nuclear Information System (INIS)

    Haug, E.

    2004-01-01

    The production of electron-positron pairs by photons in the Coulomb Field of electrons and positrons (triplet production) in hot thermal plasmas is investigated. The pair production rate for this process is calculated as a function of the photon energy and compared with the rate of photon-nucleus pair production for semi-relativistic and relativistic plasma temperatures. (author)

  19. Optical pumping of hot phonons in GaAs

    International Nuclear Information System (INIS)

    Collins, C.L.; Yu, P.Y.

    1982-01-01

    Optical pumping of hot LO phonons in GaAs has been studied as a function of the excitation photon frequency. The experimental results are in good agreement with a model calculation which includes both inter- and intra-valley electron-phonon scatterings. The GAMMA-L and GAMMA-X intervalley electron-phonon interactions in GaAs have been estimated

  20. Stability of the nonequilibrium states of a superconductor with a finite difference between the populations of the electron- and hole-like spectral branches

    International Nuclear Information System (INIS)

    Gal'perin, Y.M.; Kozub, V.I.; Spivak, B.Z.

    1981-01-01

    The stability of the nonequilibrium states of a superconductor with a finite difference between the populations of the electron- and hole-like spectral branches is investigated. It is shown that an instability similar to the Cooper instability of a normal metal arises at a sufficiently large value of the imbalance. This eliminates the imbalance within quantum-mechanical (nonkinetic) time periods. The consistency of the allowance for the imbalance in the nonequilibrium Ginzburg-Landau equations is discussed

  1. Hot chocolate effect

    International Nuclear Information System (INIS)

    Crawford, F.S.

    1982-01-01

    The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments

  2. Hot water reticulation

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, S. K.

    1977-10-15

    Hot water reticulation (district heating) is an established method of energy supply within cities in many countries. It is based on the fact that heat can often be obtained cheaply in bulk, and that the resultant savings can, in suitable circumstances, justify the investment in a reticulation network of insulated pipes to distribute the heat to many consumers in the form of hot water or occasionally steam. The heat can be used by domestic, commercial, and industrial consumers for space heating and water heating, and by industries for process heat. The costs of supplying domestic consumers can be determined by considering an average residential area, but industrial and commercial consumers are so varied in their requirements that every proposal must be treated independently. Fixed costs, variable costs, total costs, and demand and resource constraints are discussed.

  3. The hot chocolate effect

    Science.gov (United States)

    Crawford, Frank S.

    1982-05-01

    The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.

  4. Hot air balloon engine

    Energy Technology Data Exchange (ETDEWEB)

    Edmonds, Ian [Solartran Pty Ltd, 12 Lentara Street, Kenmore, Brisbane 4069 (Australia)

    2009-04-15

    This paper describes a solar powered reciprocating engine based on the use of a tethered hot air balloon fuelled by hot air from a glazed collector. The basic theory of the balloon engine is derived and used to predict the performance of engines in the 10 kW to 1 MW range. The engine can operate over several thousand metres altitude with thermal efficiencies higher than 5%. The engine thermal efficiency compares favorably with the efficiency of other engines, such as solar updraft towers, that also utilize the atmospheric temperature gradient but are limited by technical constraints to operate over a much lower altitude range. The increased efficiency allows the use of smaller area glazed collectors. Preliminary cost estimates suggest a lower $/W installation cost than equivalent power output tower engines. (author)

  5. The ''hot'' patella

    International Nuclear Information System (INIS)

    Kipper, M.S.; Alazraki, N.P.; Feiglin, D.H.

    1982-01-01

    Increased patellar uptake on bone scans is seen quite commonly but the possible or probable etiologies of this finding have not been previously well described. A review of 100 consecutive bone scans showed that the incidence of bilateral ''hot'' patellae is 15%. Identified etiologies include osteoarthritic degenerative disease (35%), fracture, possible metastatic disease, bursitis, Paget's disease, and osteomyelitis. The value of careful history, physical examination, and radiographs is stressed

  6. Hot nuclei and fragmentation

    International Nuclear Information System (INIS)

    Guerreau, D.

    1993-01-01

    A review is made of the present status concerning the production of nuclei above 5 MeV temperature. Considerable progress has been made recently on the understanding of the formation and the fate of such hot nuclei. It appears that the nucleus seems more stable against temperature than predicted by static calculations. However, the occurrence of multifragment production at high excitation energies is now well established. The various experimental features of the fragmentation process are discussed. (author) 59 refs., 12 figs

  7. 'Hot particle' intercomparison dosimetry

    International Nuclear Information System (INIS)

    Kaurin, D.G.L.; Baum, J.W.; Charles, M.W.; Darley, D.P.J.; Durham, J.S.; Scannell, M.J.; Soares, C.G.

    1996-01-01

    Dosimetry measurements of four 'hot particles' were made at different density thickness values using five different methods. The hot particles had maximum dimensions of 650 μm and maximum beta energies of 0.97, 046, 0.36, and 0.32 MeV. Absorbers were used to obtain the dose at different depths for each dosimeter. Measurements were made using exoelectron dosimeters, an extrapolation chamber, NE Extremity Tape Dosimeters (tm), Eberline RO-2 and RO-2A survey meters, and two sets of GafChromic (tm) dye film with each set read out at a different institution. From these results the dose was calculated averaged over 1 cm 2 of tissue at 18, 70, 125, and 400 μm depth. Comparisons of tissue-dose averaged over 1 cm 2 for 18, 70, and 125 μm depth based on interpolated measured values, were within 30% for the GafChromic (tm) dye film, extrapolation chamber, NE Extremity Tape Dosimeters (tm), and Eberline RO-2 and 2A (tm) survey meters except for the hot particle with 0.46 MeV maximum beta energy. The results for this source showed differences of up to 60%. The extrapolation chamber and NE Extremity Tape dosimeters under-responded for measurements at 400 μm by about a factor of 2 compared with the GafChromic dye films for two hot particles with maximum beta energy of 0.32 and 0.36 MeV which each emitted two 100% 1 MeV photons per disintegration. Tissue doses determined using exoelectron dosimeters were a factor of 2 to 5 less than those determined using other dosimeters, possibly due to failures of the equipment. (author)

  8. Solar Hot Water Heater

    Science.gov (United States)

    1978-01-01

    The solar panels pictured below, mounted on a Moscow, Idaho home, are part of a domestic hot water heating system capable of providing up to 100 percent of home or small business hot water needs. Produced by Lennox Industries Inc., Marshalltown, Iowa, the panels are commercial versions of a collector co-developed by NASA. In an effort to conserve energy, NASA has installed solar collectors at a number of its own facilities and is conducting research to develop the most efficient systems. Lewis Research Center teamed with Honeywell Inc., Minneapolis, Minnesota to develop the flat plate collector shown. Key to the collector's efficiency is black chrome coating on the plate developed for use on spacecraft solar cells, the coating prevents sun heat from "reradiating," or escaping outward. The design proved the most effective heat absorber among 23 different types of collectors evaluated in a Lewis test program. The Lennox solar domestic hot water heating system has three main components: the array of collectors, a "solar module" (blue unit pictured) and a conventional water heater. A fluid-ethylene glycol and water-is circulated through the collectors to absorb solar heat. The fluid is then piped to a double-walled jacket around a water tank within the solar module.

  9. Hot Ductility Behavior of an 8 Pct Cr Roller Steel

    Science.gov (United States)

    Wang, Zhenhua; Sun, Shuhua; Shi, Zhongping; Wang, Bo; Fu, Wantang

    2015-04-01

    The hot ductility of an 8 pct Cr roller steel was determined between 1173 K and 1473 K (900 °C and 1200 °C) at strain rates of 0.01 to 10 s-1 through tensile testing. The fracture morphology was observed using scanning electron microscopy, and the microstructure was examined through optical microscopy and transmission electron microscopy. The dependence of the hot ductility behavior on the deformation conditions, grain size, and precipitation was analyzed. The relationship between the reduction in area and the natural logarithm of the Zener-Hollomon parameter (ln Z) was found to be a second-order polynomial. When ln Z was greater than 40 s-1, the hot ductility was poor and fracture was mainly caused by incompatible deformation between the grains. When ln Z was between 32 and 40 s-1, the hot ductility was excellent and the main fracture mechanism was void linking. When ln Z was below 32 s-1, the hot ductility was poor and fracture was mainly caused by grain boundary sliding. A fine grain structure is beneficial for homogenous deformation and dynamic recrystallization, which induces better hot ductility. The effect of M7C3 carbide particles dispersed in the matrix on the hot ductility was small. The grain growth kinetics in the 8 pct Cr steel were obtained between 1373 K and 1473 K (1100 °C and 1200 °C). Finally, optimized preheating and forging procedures for 8 pct Cr steel rollers are provided.

  10. An investigation into hot deformation of aluminum alloy 5083

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinipour, S.J. [Manufacturing Engineering Department, School of Mechanical Engineering, Nushirvani Institute of Technology, University of Mazandaran, P.O. Box 484, Shariati Avenue, Babol (Iran, Islamic Republic of)], E-mail: j.hosseini@nit.ac.ir

    2009-02-15

    In this paper the hot deformation behavior of Al-5083 commercial alloy is studied. For this purpose, hot tensile tests have been carried out at various temperatures and strain rates. Velocity jump tests have been performed to determine stress-strain rate curves at various temperatures and strains. The microstructures have been studied by optical and electron microscopy (SEM). It is found that continuous recrystallization occurs during hot deformation of the AA5083. Maximum elongation about 250% is obtained at 450 deg. C and strain rate of 0.005 s{sup -1}. The failure surface is narrow and failure occurs by necking.

  11. An investigation into hot deformation of aluminum alloy 5083

    International Nuclear Information System (INIS)

    Hosseinipour, S.J.

    2009-01-01

    In this paper the hot deformation behavior of Al-5083 commercial alloy is studied. For this purpose, hot tensile tests have been carried out at various temperatures and strain rates. Velocity jump tests have been performed to determine stress-strain rate curves at various temperatures and strains. The microstructures have been studied by optical and electron microscopy (SEM). It is found that continuous recrystallization occurs during hot deformation of the AA5083. Maximum elongation about 250% is obtained at 450 deg. C and strain rate of 0.005 s -1 . The failure surface is narrow and failure occurs by necking

  12. Rapid Development of Specialty Population Registries and Quality Measures from Electronic Health Record Data*. An Agile Framework.

    Science.gov (United States)

    Kannan, Vaishnavi; Fish, Jason S; Mutz, Jacqueline M; Carrington, Angela R; Lai, Ki; Davis, Lisa S; Youngblood, Josh E; Rauschuber, Mark R; Flores, Kathryn A; Sara, Evan J; Bhat, Deepa G; Willett, DuWayne L

    2017-06-14

    Creation of a new electronic health record (EHR)-based registry often can be a "one-off" complex endeavor: first developing new EHR data collection and clinical decision support tools, followed by developing registry-specific data extractions from the EHR for analysis. Each development phase typically has its own long development and testing time, leading to a prolonged overall cycle time for delivering one functioning registry with companion reporting into production. The next registry request then starts from scratch. Such an approach will not scale to meet the emerging demand for specialty registries to support population health and value-based care. To determine if the creation of EHR-based specialty registries could be markedly accelerated by employing (a) a finite core set of EHR data collection principles and methods, (b) concurrent engineering of data extraction and data warehouse design using a common dimensional data model for all registries, and (c) agile development methods commonly employed in new product development. We adopted as guiding principles to (a) capture data as a byproduct of care of the patient, (b) reinforce optimal EHR use by clinicians, (c) employ a finite but robust set of EHR data capture tool types, and (d) leverage our existing technology toolkit. Registries were defined by a shared condition (recorded on the Problem List) or a shared exposure to a procedure (recorded on the Surgical History) or to a medication (recorded on the Medication List). Any EHR fields needed - either to determine registry membership or to calculate a registry-associated clinical quality measure (CQM) - were included in the enterprise data warehouse (EDW) shared dimensional data model. Extract-transform-load (ETL) code was written to pull data at defined "grains" from the EHR into the EDW model. All calculated CQM values were stored in a single Fact table in the EDW crossing all registries. Registry-specific dashboards were created in the EHR to display

  13. Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. I. Dislocation microstructures in as-received state and at different plastic strains

    Energy Technology Data Exchange (ETDEWEB)

    Long, Fei; Daymond, Mark R., E-mail: mark.daymond@queensu.ca; Yao, Zhongwen [Department of Mechanical and Materials Engineering, Queen' s University Kingston, Ontario K7L 3N6 (Canada)

    2015-03-07

    Thin foil dog bone samples prepared from a hot rolled Zr-2.5Nb alloy have been deformed by tensile deformation to different plastic strains. The development of slip traces during loading was observed in situ through SEM, revealing that deformation starts preferentially in certain sets of grains during the elastic-plastic transition region. TEM characterization showed that sub-grain boundaries formed during hot rolling consisted of screw 〈a〉 dislocations or screw 〈c〉 and 〈a〉 dislocations. Prismatic 〈a〉 dislocations with large screw or edge components have been identified from the sample with 0.5% plastic strain. Basal 〈a〉 and pyramidal 〈c + a〉 dislocations were found in the sample that had been deformed with 1.5% plastic strain, implying that these dislocations require larger stresses to be activated.

  14. Reactivating Catalytic Surface: Insights into the Role of Hot Holes in Plasmonic Catalysis.

    Science.gov (United States)

    Peng, Tianhuan; Miao, Junjian; Gao, Zhaoshuai; Zhang, Linjuan; Gao, Yi; Fan, Chunhai; Li, Di

    2018-03-01

    Surface plasmon resonance of coinage metal nanoparticles is extensively exploited to promote catalytic reactions via harvesting solar energy. Previous efforts on elucidating the mechanisms of enhanced catalysis are devoted to hot electron-induced photothermal conversion and direct charge transfer to the adsorbed reactants. However, little attention is paid to roles of hot holes that are generated concomitantly with hot electrons. In this work, 13 nm spherical Au nanoparticles with small absorption cross-section are employed to catalyze a well-studied glucose oxidation reaction. Density functional theory calculation and X-ray absorption spectrum analysis reveal that hot holes energetically favor transferring catalytic intermediates to product molecules and then desorbing from the surface of plasmonic catalysts, resulting in the recovery of their catalytic activities. The studies shed new light on the use of the synergy of hot holes and hot electrons for plasmon-promoted catalysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Hot Carrier Generation and Extraction of Plasmonic Alloy Nanoparticles.

    Science.gov (United States)

    Valenti, Marco; Venugopal, Anirudh; Tordera, Daniel; Jonsson, Magnus P; Biskos, George; Schmidt-Ott, Andreas; Smith, Wilson A

    2017-05-17

    The conversion of light to electrical and chemical energy has the potential to provide meaningful advances to many aspects of daily life, including the production of energy, water purification, and optical sensing. Recently, plasmonic nanoparticles (PNPs) have been increasingly used in artificial photosynthesis (e.g., water splitting) devices in order to extend the visible light utilization of semiconductors to light energies below their band gap. These nanoparticles absorb light and produce hot electrons and holes that can drive artificial photosynthesis reactions. For n-type semiconductor photoanodes decorated with PNPs, hot charge carriers are separated by a process called hot electron injection (HEI), where hot electrons with sufficient energy are transferred to the conduction band of the semiconductor. An important parameter that affects the HEI efficiency is the nanoparticle composition, since the hot electron energy is sensitive to the electronic band structure of the metal. Alloy PNPs are of particular importance for semiconductor/PNPs composites, because by changing the alloy composition their absorption spectra can be tuned to accurately extend the light absorption of the semiconductor. This work experimentally compares the HEI efficiency from Ag, Au, and Ag/Au alloy nanoparticles to TiO 2 photoanodes for the photoproduction of hydrogen. Alloy PNPs not only exhibit tunable absorption but can also improve the stability and electronic and catalytic properties of the pure metal PNPs. In this work, we find that the Ag/Au alloy PNPs extend the stability of Ag in water to larger applied potentials while, at the same time, increasing the interband threshold energy of Au. This increasing of the interband energy of Au suppresses the visible-light-induced interband excitations, favoring intraband excitations that result in higher hot electron energies and HEI efficiencies.

  16. Population decay time and distribution of exciton states analyzed by rate equations based on theoretical phononic and electron-collisional rate coefficients

    Science.gov (United States)

    Oki, Kensuke; Ma, Bei; Ishitani, Yoshihiro

    2017-11-01

    Population distributions and transition fluxes of the A exciton in bulk GaN are theoretically analyzed using rate equations of states of the principal quantum number n up to 5 and the continuum. These rate equations consist of the terms of radiative, electron-collisional, and phononic processes. The dependence of the rate coefficients on temperature is revealed on the basis of the collisional-radiative model of hydrogen plasma for the electron-collisional processes and theoretical formulation using Fermi's "golden rule" for the phononic processes. The respective effects of the variations in electron, exciton, and lattice temperatures are exhibited. This analysis is a base of the discussion on nonthermal equilibrium states of carrier-exciton-phonon dynamics. It is found that the exciton dissociation is enhanced even below 150 K mainly by the increase in the lattice temperature. When the thermal-equilibrium temperature increases, the population fluxes between the states of n >1 and the continuum become more dominant. Below 20 K, the severe deviation from the Saha-Boltzmann distribution occurs owing to the interband excitation flux being higher than the excitation flux from the 1 S state. The population decay time of the 1 S state at 300 K is more than ten times longer than the recombination lifetime of excitons with kinetic energy but without the upper levels (n >1 and the continuum). This phenomenon is caused by a shift of population distribution to the upper levels. This phonon-exciton-radiation model gives insights into the limitations of conventional analyses such as the ABC model, the Arrhenius plot, the two-level model (n =1 and the continuum), and the neglect of the upper levels.

  17. Time to B. cereus about hot chocolate.

    Science.gov (United States)

    Nelms, P K; Larson, O; Barnes-Josiah, D

    1997-01-01

    To determine the cause of illnesses experienced by employees of a Minneapolis manufacturing plant after drinking hot chocolate bought from a vending machine and to explore the prevalence of similar vending machine-related illnesses. The authors inspected the vending machines at the manufacturing plant where employees reported illnesses and at other locations in the city where hot chocolate beverages were sold in machines. Tests were performed on dry mix, water, and beverage samples and on machine parts. Laboratory analyses confirmed the presence of B. cereus in dispensed beverages at a concentration capable of causing illness (170,000 count/gm). In citywide testing of vending machines dispensing hot chocolate, 7 of the 39 licensed machines were found to be contaminated, with two contaminated machines having B. cereus levels capable of causing illness. Hot chocolate sold in vending machines may contain organisms capable of producing toxins that under favorable conditions, can induce illness. Such illnesses are likely to be underreported. Even low concentrations of B. cereus may be dangerous for vulnerable populations such as the aged or immunosuppressed. Periodic testing of vending machines is thus warranted. The relationship between cleaning practices and B. cereus contamination is an issue for further study.

  18. Comparative analyses of population-scale phenomic data in electronic medical records reveal race-specific disease networks

    Science.gov (United States)

    Glicksberg, Benjamin S.; Li, Li; Badgeley, Marcus A.; Shameer, Khader; Kosoy, Roman; Beckmann, Noam D.; Pho, Nam; Hakenberg, Jörg; Ma, Meng; Ayers, Kristin L.; Hoffman, Gabriel E.; Dan Li, Shuyu; Schadt, Eric E.; Patel, Chirag J.; Chen, Rong; Dudley, Joel T.

    2016-01-01

    Motivation: Underrepresentation of racial groups represents an important challenge and major gap in phenomics research. Most of the current human phenomics research is based primarily on European populations; hence it is an important challenge to expand it to consider other population groups. One approach is to utilize data from EMR databases that contain patient data from diverse demographics and ancestries. The implications of this racial underrepresentation of data can be profound regarding effects on the healthcare delivery and actionability. To the best of our knowledge, our work is the first attempt to perform comparative, population-scale analyses of disease networks across three different populations, namely Caucasian (EA), African American (AA) and Hispanic/Latino (HL). Results: We compared susceptibility profiles and temporal connectivity patterns for 1988 diseases and 37 282 disease pairs represented in a clinical population of 1 025 573 patients. Accordingly, we revealed appreciable differences in disease susceptibility, temporal patterns, network structure and underlying disease connections between EA, AA and HL populations. We found 2158 significantly comorbid diseases for the EA cohort, 3265 for AA and 672 for HL. We further outlined key disease pair associations unique to each population as well as categorical enrichments of these pairs. Finally, we identified 51 key ‘hub’ diseases that are the focal points in the race-centric networks and of particular clinical importance. Incorporating race-specific disease comorbidity patterns will produce a more accurate and complete picture of the disease landscape overall and could support more precise understanding of disease relationships and patient management towards improved clinical outcomes. Contacts: rong.chen@mssm.edu or joel.dudley@mssm.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27307606

  19. Comparative analyses of population-scale phenomic data in electronic medical records reveal race-specific disease networks.

    Science.gov (United States)

    Glicksberg, Benjamin S; Li, Li; Badgeley, Marcus A; Shameer, Khader; Kosoy, Roman; Beckmann, Noam D; Pho, Nam; Hakenberg, Jörg; Ma, Meng; Ayers, Kristin L; Hoffman, Gabriel E; Dan Li, Shuyu; Schadt, Eric E; Patel, Chirag J; Chen, Rong; Dudley, Joel T

    2016-06-15

    Underrepresentation of racial groups represents an important challenge and major gap in phenomics research. Most of the current human phenomics research is based primarily on European populations; hence it is an important challenge to expand it to consider other population groups. One approach is to utilize data from EMR databases that contain patient data from diverse demographics and ancestries. The implications of this racial underrepresentation of data can be profound regarding effects on the healthcare delivery and actionability. To the best of our knowledge, our work is the first attempt to perform comparative, population-scale analyses of disease networks across three different populations, namely Caucasian (EA), African American (AA) and Hispanic/Latino (HL). We compared susceptibility profiles and temporal connectivity patterns for 1988 diseases and 37 282 disease pairs represented in a clinical population of 1 025 573 patients. Accordingly, we revealed appreciable differences in disease susceptibility, temporal patterns, network structure and underlying disease connections between EA, AA and HL populations. We found 2158 significantly comorbid diseases for the EA cohort, 3265 for AA and 672 for HL. We further outlined key disease pair associations unique to each population as well as categorical enrichments of these pairs. Finally, we identified 51 key 'hub' diseases that are the focal points in the race-centric networks and of particular clinical importance. Incorporating race-specific disease comorbidity patterns will produce a more accurate and complete picture of the disease landscape overall and could support more precise understanding of disease relationships and patient management towards improved clinical outcomes. rong.chen@mssm.edu or joel.dudley@mssm.edu Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

  20. Can an alert in primary care electronic medical records increase participation in a population-based screening programme for colorectal cancer? COLO-ALERT, a randomised clinical trial

    International Nuclear Information System (INIS)

    Guiriguet-Capdevila, Carolina; Fuentes-Peláez, Antonio; Reina-Rodríguez, Dolores; De León-Gallo, Rosa; Mendez-Boo, Leonardo; Torán-Monserrat, Pere; Muñoz-Ortiz, Laura; Rivero-Franco, Irene; Vela-Vallespín, Carme; Vilarrubí-Estrella, Mercedes; Torres-Salinas, Miquel; Grau-Cano, Jaume; Burón-Pust, Andrea; Hernández-Rodríguez, Cristina

    2014-01-01

    Colorectal cancer is an important public health problem in Spain. Over the last decade, several regions have carried out screening programmes, but population participation rates remain below recommended European goals. Reminders on electronic medical records have been identified as a low-cost and high-reach strategy to increase participation. Further knowledge is needed about their effect in a population-based screening programme. The main aim of this study is to evaluate the effectiveness of an electronic reminder to promote the participation in a population-based colorectal cancer screening programme. Secondary aims are to learn population’s reasons for refusing to take part in the screening programme and to find out the health professionals’ opinion about the official programme implementation and on the new computerised tool. This is a parallel randomised trial with a cross-sectional second stage. Participants: all the invited subjects to participate in the public colorectal cancer screening programme that includes men and women aged between 50–69, allocated to the eleven primary care centres of the study and all their health professionals. The randomisation unit will be the primary care physician. The intervention will consist of activating an electronic reminder, in the patient’s electronic medical record, in order to promote colorectal cancer screening, during a synchronous medical appointment, throughout the year that the intervention takes place. A comparison of the screening rates will then take place, using the faecal occult blood test of the patients from the control and the intervention groups. We will also take a questionnaire to know the opinions of the health professionals. The main outcome is the screening status at the end of the study. Data will be analysed with an intention-to-treat approach. We expect that the introduction of specific reminders in electronic medical records, as a tool to facilitate and encourage direct referral by

  1. Data-driven drug safety signal detection methods in pharmacovigilance using electronic primary care records: A population based study

    Directory of Open Access Journals (Sweden)

    Shang-Ming Zhou

    2017-04-01

    Data-driven analytic methods are a valuable aid to signal detection of ADEs from large electronic health records for drug safety monitoring. This study finds the methods can detect known ADE and so could potentially be used to detect unknown ADE.

  2. Radial evolution of nonthermal electron populations in the low-latitude solar wind: Helios, Cluster, and Ulysses Observations

    Czech Academy of Sciences Publication Activity Database

    Štverák, Štěpán; Maksimovic, M.; Trávníček, Pavel M.; Marsch, E.; Fazakerley, A. N.; Scime, E. E.

    2009-01-01

    Roč. 114, - (2009), A05104/1-A05104/15 ISSN 0148-0227 Institutional research plan: CEZ:AV0Z30420517; CEZ:AV0Z10030501 Keywords : solar wind * radial evolution * non- thermal electron properties Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.082, year: 2009

  3. Emerging hot spot analysis

    DEFF Research Database (Denmark)

    Reinau, Kristian Hegner

    Traditionally, focus in the transport field, both politically and scientifically, has been on private cars and public transport. Freight transport has been a neglected topic. Recent years has seen an increased focus upon congestion as a core issue across Europe, resulting in a great need for know...... speed data for freight. Secondly, the analytical methods used, space-time cubes and emerging hot spot analysis, are also new in the freight transport field. The analysis thus estimates precisely how fast freight moves on the roads in Northern Jutland and how this has evolved over time....

  4. Progress in hot pressing

    International Nuclear Information System (INIS)

    Brodhag, C.; Thevenot, F.

    1988-01-01

    An experimental technique is described to study hot pressing of ceramics under conditions of controlled temperature and pressure during both the heating and final sintering stages. This method gives a better control of the final microstructure of the material. Transformation mechanisms can be studied during initial heating stage (impurity degasing, reaction, phase transformation, mechanical behavior of intergranular phase...) using computer control and graphical data representations. Some examples will be given for different systems studied in our laboratory: B (α, β, amorphous), B 12 O 2 (reaction of B + B 2 O 3 ), Si 3 N 4 ( + additives), TiN, Al 2 O 3 + AlON,ZrC

  5. Multipurpose reprocessing hot cell

    International Nuclear Information System (INIS)

    Fletcher, R.D.

    1975-01-01

    A multipurpose hot cell is being designed for use at the Idaho Chemical Processing Plant for handling future scheduled fuels that cannot be adequately handled by the existing facilities and equipment. In addition to providing considerable flexibility to handle a wide variety of fuel sizes up to 2,500 lb in weight the design will provide for remote maintenance or replacement of the in-cell equipment with a minimum of exposure to personnel and also provide process piping connections for custom processing of small quantities of fuel. (auth)

  6. Electron-attachment processes

    International Nuclear Information System (INIS)

    Christophorou, L.G.; McCorkle, D.L.; Christodoulides, A.A.

    1982-01-01

    Topics covered include: (1) modes of production of negative ions, (2) techniques for the study of electron attachment processes, (3) dissociative electron attachment to ground-state molecules, (4) dissociative electron attachment to hot molecules (effects of temperature on dissociative electron attachment), (5) molecular parent negative ions, and (6) negative ions formed by ion-pair processes and by collisions of molecules with ground state and Rydberg atoms

  7. Residential solar hot water

    Energy Technology Data Exchange (ETDEWEB)

    1982-06-01

    This report examines the feasibility of using solar energy to preheat domestic water coming from the city supply at a temperature of approximately 4{degree}C. Four solar collectors totalling 7 m{sup 2} were installed on a support structure facing south at an angle of 60{degree} from the horizontal. The system worked most efficiently in the spring and early summer when the combination of long hours of sunshine, clean air and clear skies allowed for maximum availability of solar radiation. Performance dropped in late summer and fall mainly due to cloudier weather conditions. The average temperature in the storage tank over the 10 months of operation was 42{degree}C, ranging from a high of 83{degree}C in July to a low of 6{degree}C in November. The system provided a total of 7.1 GJ, which is approximately one-third the annual requirement for domestic hot water heating. At the present time domestic use of solar energy to heat water does not appear to be economically viable. High capital costs are the main problem. As a solar system with present day technology can only be expected to meet half to two-thirds of the hot water energy demand the savings are not sufficient for the system to pay for itself within a few years. 5 figs.

  8. Electron beam fluorescence spectrometry of internal state populations in nozzle beams of nitrogen and nitrogen/rare gas mixtures

    International Nuclear Information System (INIS)

    Faubel, M.; Weiner, E.R.

    1981-01-01

    Rotational level populations of N 2 were measured downstream from the skimmer in beams of pure N 2 and in mixtures of N 2 with He, Ne, and Ar expanded from room temperature nozzles. The range of p 0 D was from 5 to 50 Torr cm. The formation of dimers and higher condensates of beam species was monitored during the runs. The effect of condensation energy release on rotational populations and parallel temperatures was readily observed. Two different methods for evaluating the rotational population distributions were compared. One method is based on a dipole-excitation model and the other on an excitation matrix obtained empirically. Neither method proved clearly superior. Both methods indicated nonequilibrium rotational populations for all of our room temperature nozzle expansion conditions. Much of the nonequilibrium character appears to be due to the behavior of the K = 2 and K = 4 levels, which may be accounted for in terms of the rotational energy level spacing. In particular, the overpopulation of the K = 4 level is explained by a near-resonant transfer of rotational energy between molecules in the K = 6 and K = 0 states, to give two molecules in the K = 4 state. Rotational and vibrational temperatures were determined for pure N 2 beams from nozzles heated up to 1700 0 K. The heated nozzle experiments indicated a 40% increase in the rotational collision number between 300 and 1700 0 K

  9. Hot springs in Hokuriku District

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K. (Hot Springs Research Center, Japan)

    1971-01-01

    In the Hokuriku district including Toyama, Ishikawa, and Fukui Prefectures, hot springs of more than 25/sup 0/C were investigated. In the Toyama Prefecture, there are 14 hot springs which are located in an area from the Kurobe River to the Tateyama volcano and in the mountainous area in the southwest. In Ishikawa Prefecture there are 16 hot springs scattered in Hakusan and its vicinity, the Kaga mountains, and in the Noto peninsula. In northern Fukui Prefecture there are seven hot springs. The hot springs in Shirakawa in Gifu Prefecture are characterized as acid springs producing exhalations and H/sub 2/S. These are attributed to the Quaternary volcanoes. The hot springs of Wakura, Katayamazu, and Awara in Ishikawa Prefecture are characterized by a high Cl content which is related to Tertiary andesite. The hot springs of Daishoji, Yamanaka, Yamashiro, Kuritsu, Tatsunokuchi, Yuwaku, and Yunotani are characterized by a low HCO/sub 3/ content. The Ca and SO/sub 4/ content decreases from east to west, and the Na and Cl content increases from west to east. These fluctuations are related to the Tertiary tuff and rhyolite. The hot springs of Kuronagi, Kinshu, and Babadani, located along the Kurobe River are characterized by low levels of dissolved components and high CO/sub 2/ and HCO/sub 3/ content. These trends are related to late Paleozoic granite. Hot springs resources are considered to be connected to geothermal resources. Ten tables, graphs, and maps are provided.

  10. Multifunctional Hot Structure Heat Shield

    Data.gov (United States)

    National Aeronautics and Space Administration — This project is performing preliminary development of a Multifunctional Hot Structure (HOST) heat shield for planetary entry. Results of this development will...

  11. Anomalous properties of hot dense nonequilibrium plasmas

    International Nuclear Information System (INIS)

    Ferrante, G; Zarcone, M; Uryupin, S A

    2005-01-01

    A concise overview of a number of anomalous properties of hot dense nonequilibrium plasmas is given. The possibility of quasistationary megagauss magnetic field generation due to Weibel instability is discussed for plasmas created in atom tunnel ionization. The collisionless absorption and reflection of a test electromagnetic wave normally impinging on the plasma with two-temperature bi-maxwellian electron velocity distribution function are studied. Due to the wave magnetic field influence on the electron kinetics in the skin layer the wave absorption and reflection significantly depend on the degree of the electron temperature anisotropy. The linearly polarized impinging wave during reflection transforms into an elliptically polarized one. The problem of transmission of an ultrashort laser pulse through a layer of dense plasma, formed as a result of ionization of a thin foil, is considered. It is shown that the strong photoelectron distribution anisotropy yields an anomalous penetration of the wave field through the foil

  12. In situ ecophysiology of Aigarchaeota from an oxic, hot-spring filamentous 'streamer' community

    Science.gov (United States)

    Beam, J.; Jay, Z.; Tringe, S. G.; Glavina del Rio, T.; Rusch, D.; Schmid, M.; Wagner, M.; Inskeep, W.

    2014-12-01

    The candidate phylum Aigarchaeota contains thermophilic archaea from terrestrial, subsurface, and marine geothermal ecosystems. The phylogeny and metabolic potential of Aigarchaeota has been deduced from several recent single-cell amplified genomes; however, an accurate description of their metabolism, potential ecological interactions, and role in biogeochemical cycling is lacking. Here we report possible ecological interactions and the in situ metabolism of an uncultivated lineage of Aigarchaeota from an oxic, terrestrial hot-spring filamentous 'streamer' community (Octopus Spring, pH = 8; T = 78 - 84 °C, Yellowstone National Park, Wyoming, USA). Fluorescence in situ hybridization (FISH) was combined with detailed genomic and transcriptomic reconstruction to elucidate the ecophysiological role of Aigarchaeota in these streamer communities. This novel population of Aigarchaeota are filamentous (~500 nm diameter by ~10-30 μm length), which is consistent with the morphology predicted by the presence and transcription of a single actin-encoding gene. Aigarchaeota filaments are intricately associated with other community members, which include both thermophilic bacteria and archaea. Metabolic reconstruction suggests that this aigarchaeon is an aerobic, chemoorganotroph. A single heme copper oxidase complex was identified in de novo genome assemblies, and was highly transcribed in environmental samples. Potential electron donors include acetate, fatty acids, sugars, peptides, and aromatic compounds. Transcripts related to genes specific to each of these potential electron donors were identified, indicating that this population of Aigarchaeota likely utilizes a broad range of reduced carbon substrates. Potential electron donors for this population may include extracellular polymeric substances produced by other microorganisms in close proximity. Flagellum genes were also highly transcribed, which suggests a potential mechanism for motility and/or cell-cell attachment

  13. Harnessing Social Networks along with Consumer-Driven Electronic Communication Technologies to Identify and Engage Members of 'Hard-to-Reach' Populations: A Methodological Case Report

    Directory of Open Access Journals (Sweden)

    Rock Melanie J

    2010-01-01

    Full Text Available Abstract Background Sampling in the absence of accurate or comprehensive information routinely poses logistical, ethical, and resource allocation challenges in social science, clinical, epidemiological, health service and population health research. These challenges are compounded if few members of a target population know each other or regularly interact. This paper reports on the sampling methods adopted in ethnographic case study research with a 'hard-to-reach' population. Methods To identify and engage a small yet diverse sample of people who met an unusual set of criteria (i.e., pet owners who had been treating cats or dogs for diabetes, four sampling strategies were used. First, copies of a recruitment letter were posted in pet-friendly places. Second, information about the study was diffused throughout the study period via word of mouth. Third, the lead investigator personally sent the recruitment letter via email to a pet owner, who then circulated the information to others, and so on. Fourth, veterinarians were enlisted to refer people who had diabetic pets. The second, third and fourth strategies rely on social networks and represent forms of chain referral sampling. Results Chain referral sampling via email proved to be the most efficient and effective, yielding a small yet diverse group of respondents within one month, and at negligible cost. Conclusions The widespread popularity of electronic communication technologies offers new methodological opportunities for researchers seeking to recruit from hard-to-reach populations.

  14. Harnessing social networks along with consumer-driven electronic communication technologies to identify and engage members of 'hard-to-reach' populations: a methodological case report.

    Science.gov (United States)

    Rock, Melanie J

    2010-01-20

    Sampling in the absence of accurate or comprehensive information routinely poses logistical, ethical, and resource allocation challenges in social science, clinical, epidemiological, health service and population health research. These challenges are compounded if few members of a target population know each other or regularly interact. This paper reports on the sampling methods adopted in ethnographic case study research with a 'hard-to-reach' population. To identify and engage a small yet diverse sample of people who met an unusual set of criteria (i.e., pet owners who had been treating cats or dogs for diabetes), four sampling strategies were used. First, copies of a recruitment letter were posted in pet-friendly places. Second, information about the study was diffused throughout the study period via word of mouth. Third, the lead investigator personally sent the recruitment letter via email to a pet owner, who then circulated the information to others, and so on. Fourth, veterinarians were enlisted to refer people who had diabetic pets. The second, third and fourth strategies rely on social networks and represent forms of chain referral sampling. Chain referral sampling via email proved to be the most efficient and effective, yielding a small yet diverse group of respondents within one month, and at negligible cost. The widespread popularity of electronic communication technologies offers new methodological opportunities for researchers seeking to recruit from hard-to-reach populations.

  15. Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Jaworski, M A; Gray, T K; Kaita, R; Kallman, J; Kugel, H; LeBlanc, B; McLean, A; Sabbagh, S A; Soukanovskii, V; Stotler, D P

    2011-06-03

    The National Spherical Torus Experiment (NSTX) has recently studied the use of a liquid lithium divertor (LLD). Divertor Langmuir probes have also been installed for making measurements of the local plasma conditions. A non-local probe interpretation method is used to supplement the classical probe interpretation and obtain measurements of the electron energy distribution function (EEDF) which show the occurrence of a hot-electron component. Analysis is made of two discharges within a sequence that exhibited changes in plasma fueling efficiency. It is found that the local electron temperature increases and that this increase is most strongly correlated with the energy contained within the hot-electron population. Preliminary interpretative modeling indicates that kinetic effects are likely in the NSTX.

  16. Fabrication and properties of hot pressed bismuth tungstate

    International Nuclear Information System (INIS)

    Streicher, W.L.

    1978-01-01

    Bi 2 WO 6 is a synthetic polar material that is a possible candidate for energy conversion and detection systems. Previous research on this material has been concerned with crystal growth and sintering characteristics of polycrystalline compacts. This study involves itself with the fabrication of polycrystalline compacts by hot pressing techniques. Densities approaching theoretical crystal density were achieved by hot pressing at 850 0 C for one hour with pressures exceeding 35 MPa. Before hot pressing, the sintering range was determined by high temperature dilatometry of unfired Bi 2 WO 6 ceramics. Hot pressed discs were characterized by scanning electron microscopy, differential scanning calorimetry, and x-ray diffraction. Electrical properties were determined by dc resistivity, capacitance, and conductance measurements, ac poling, dc poling, and current-voltage measurements

  17. Long-lived hot-carrier light emission and large blue shift in formamidinium tin triiodide perovskites

    NARCIS (Netherlands)

    Fang, Hong-Hua; Adjokatse, Sampson; Shao, Shuyan; Even, Jacky; Loi, Maria Antonietta

    2018-01-01

    A long-lived hot carrier population is critical in order to develop working hot carrier photovoltaic devices with efficiencies exceeding the Shockley-Queisser limit. Here, we report photoluminescence from hot-carriers with unexpectedly long lifetime (a few ns) in formamidinium tin triiodide. An

  18. Electron-acoustic Instability Simulated By Modified Zakharov Equations

    Science.gov (United States)

    Jásenský, V.; Fiala, V.; Vána, O.; Trávnícek, P.; Hellinger, P.

    We present non-linear equations describing processes in plasma when electron - acoustic waves are excited. These waves are present for instance in the vicinity of Earth's bow shock and in the polar ionosphere. Frequently they are excited by an elec- tron beam in a plasma with two electron populations, a cold and hot one. We derive modified Zakharov equations from kinetic theory for such a case together with numer- ical method for solving of this type of equations. Bispectral analysis is used to show which non-linear wave processes are of importance in course of the instability. Finally, we compare these results with similar simulations using Vlasov approach.

  19. Magnetic holes in the dipolarized magnetotail: ion and electron anisotropies

    Science.gov (United States)

    Shustov, P.; Artemyev, A.; Zhang, X. J.; Yushkov, E.; Petrukovich, A. A.

    2017-12-01

    We conduct statistics on magnetic holes observed by THEMIS spacecraft in the near-Earth magnetotail. Groups of holes are detected after dipolarizations in the quiet, equatorial plasma sheet. Magnetic holes are characterized by significant magnetic field depressions (up to 50%) and strong electron currents ( 10-50 nA/m2), with spatial scales much smaller than the ion gyroradius. These magnetic holes are populated by hot (>10 keV), transversely anisotropic electrons supporting the pressure balance. We present statistical properties of these sub-ion scale magnetic holes and discuss possible mechanisms on the hole formation.

  20. Hot cell verification facility update

    International Nuclear Information System (INIS)

    Titzler, P.A.; Moffett, S.D.; Lerch, R.E.

    1985-01-01

    The Hot Cell Verification Facility (HCVF) provides a prototypic hot cell mockup to check equipment for functional and remote operation, and provides actual hands-on training for operators. The facility arrangement is flexible and assists in solving potential problems in a nonradioactive environment. HCVF has been in operation for six years, and the facility is a part of the Hanford Engineering Development Laboratory

  1. Formaldehyde as a carbon and electron shuttle between autotroph and heterotroph populations in acidic hydrothermal vents of Norris Geyser Basin, Yellowstone National Park

    Energy Technology Data Exchange (ETDEWEB)

    Moran, James J.; Whitmore, Laura M.; Isern, Nancy G.; Romine, Margaret F.; Riha, Krystin M.; Inskeep, William P.; Kreuzer, Helen W.

    2016-03-19

    The Norris Geyser Basin in Yellowstone National Park contains a large number of hydrothermal systems, which host microbial populations supported by primary productivity associated with a suite of chemolithotrophic metabolisms. We demonstrate that Metallosphaera yellowstonesis MK1, a facultative autotrophic archaeon isolated from a hyperthermal acidic hydrous ferric oxide (HFO) spring in Norris Geyser Basin, excretes formaldehyde during autotrophic growth. To determine the fate of formaldehyde in this low organic carbon environment, we incubated native microbial mat (containing M. yellowstonensis) from a HFO spring with 13C-formaldehyde. Isotopic analysis of incubation-derived CO2 and biomass showed that formaldehyde was both oxidized and assimilated by members of the community. Autotrophy, formaldehyde oxidation, and formaldehyde assimilation displayed different sensitivities to chemical inhibitors, suggesting that distinct sub-populations in the mat selectively perform these functions. Our results demonstrate that electrons originally resulting from iron oxidation can energetically fuel autotrophic carbon fixation and associated formaldehyde excretion, and that formaldehyde is both oxidized and assimilated by different organisms within the native microbial community. Thus, formaldehyde can effectively act as a carbon and electron shuttle connecting the autotrophic, iron oxidizing members with associated heterotrophic members in the HFO community.

  2. SEM hot stage sintering of UO2

    International Nuclear Information System (INIS)

    Miller, D.J.

    1976-06-01

    The sintering of hyperstoichiometric uranium dioxide powder compacts, in the hot stage of a scanning electron microscope, was continuously monitored using 16 mm time lapse movies. From alumina microspheres placed on the surface of the compacts, shrinkage measurements were obtained. Converting shrinkage measurements into densification profiles indicates that a maximum densification rate is reached at a critical density, independent of the constant heating rates. At temperatures above 1350 0 C, the movement of the reference microspheres made shrinkage measurements impossible. It is believed the evolution of UO 3 gas from hyperstoichiometric UO 2 is the cause of this limitation

  3. Hot plasma parameters in Neptune's magnetosphere

    International Nuclear Information System (INIS)

    Krimigis, S.M.; Mauk, B.H.; Cheng, A.F.; Keath, E.P.; Kane, M.; Armstrong, T.P.; Gloeckler, G.; Lanzerotti, L.J.

    1990-01-01

    Energy spectra of energetic protons and electrons (E p approx-gt 28 keV, E e approx-gt 22 keV, respectively) obtained with the Low Energy Charged Particle (LECP) instrument during the Voyager 2 encounter with Neptune on August 24-25, 1989 are presented. The proton spectral form was a power law (dj/dE = KE -γ ), outside the orbit of Triton (∼14.3 R N ); inside that distance, it was found to be a hot (kT ≅ 60 keV) Maxwellian distribution. Such distributions, observed in other planets as well, have yet to be explained theoretically. Similarly, the electron spectral form changed from a simple power law outside Triton to a two-slope power law with a high energy tail inside. Intensity and spectral features in both proton and electron fluxes were identified in association with the crossings of the Triton and 1989 N1 L-shells, but these features do not occur simultaneously in both species. Such signatures were manifested by relative peaks in both kT and γ spectral indices. Peak proton pressures of ∼2x10 -9 dynes cm -2 , and β ∼ 0.2 were measured at successive magnetic equatorial crossings, both inbound and outbound. These parameters show Neptune's magnetosphere to be relatively undistorted by hot plasma loading, similar to that of Uranus and unlike those of Saturn and Jupiter. Trapped electron fluxes at Neptune, as at Uranus, exceed the whistler mode stably trapped flux limit. Whistler-induced pitch angle scattering of energetic electrons in the radiation belts can yield a precipitating energy flux sufficient to drive Neptune's aurora

  4. Observation of electron plasma waves in plasma of two-temperature electrons

    International Nuclear Information System (INIS)

    Ikezawa, Shunjiro; Nakamura, Yoshiharu.

    1981-01-01

    Propagation of electron plasma waves in a large and unmagnetized plasma containing two Maxwellian distributions of electrons is studied experimentally. Two kinds of plasma sources which supply electrons of different temperature are used. The temperature ratio is about 3 and the density ratio of hot to cool electrons is varied from 0 to 0.5. A small contamination of hot electrons enhances the Landau damping of the principal mode known as the Bohm-Gross mode. When the density of hot electrons is larger than about 0.2, two modes are observed. The results agree with theoretical dispersion relations when excitation efficiencies of the modes are considered. (author)

  5. Electron-cyclotron-resonant-heated electron distribution functions

    International Nuclear Information System (INIS)

    Matsuda, Y.; Nevins, W.M.; Cohen, R.H.

    1981-01-01

    Recent studies at Lawrence Livermore National Laboratory (LLNL) with a bounce-averaged Fokker-Planck code indicate that the energetic electron tail formed by electron-cyclotron resonant heating (ECRH) at the second harmonic is not Maxwellian. We present the results of our bounce-averaged Fokker-Planck code along with some simple analytic models of hot-electron distribution functions

  6. The association between use of electronic media and prevalence of headache in adolescents: results from a population-based cross-sectional study.

    Science.gov (United States)

    Milde-Busch, Astrid; von Kries, Rüdiger; Thomas, Silke; Heinrich, Sabine; Straube, Andreas; Radon, Katja

    2010-02-09

    Use of electronic media, i.e. mobile phones, computers, television, game consoles or listening to music, is very common, especially amongst adolescents. There is currently a debate about whether frequent use of these media might have adverse effects on health, especially on headaches, which are among the most-reported health complaints in adolescents. The aim of the present study was to assess associations between frequent use of electronic media and the prevalence of different types of headache in adolescents. Data were derived from a population-based sample (n = 1,025, ages 13-17 years). Type of headache (i.e. migraine, tension-type headache, unclassifiable headache) was ascertained by standardized questionnaires for subjects reporting headache episodes at least once per month during the last six months. Duration of electronic media use was assessed during personal interviews. Associations were estimated with logistic regression models adjusted for age group, sex, family condition and socio-economic status. Most of the adolescents used computers (85%), watched television (90%) or listened to music (90%) daily, otherwise only 23% of the participants used their mobile phones and only 25% played with game consoles on a daily basis. A statistically significant association between listening to music and any headache (odds ratio 1.8; 95% confidence interval 1.1-3.1 for 30 minutes per day, 2.1; 1.2-3.7 for 1 to 2 hours per day; 2.0; 1.2-3.5 for 3 hours and longer listening to music per day) was observed. When stratifying for type of headache, no statistically significant association was seen. Apart from an association between listening to music on a daily basis and overall headache, no consistent associations between the use of electronic media and different types of headache were observed.

  7. The association between use of electronic media and prevalence of headache in adolescents: results from a population-based cross-sectional study

    Directory of Open Access Journals (Sweden)

    Straube Andreas

    2010-02-01

    Full Text Available Abstract Background Use of electronic media, i.e. mobile phones, computers, television, game consoles or listening to music, is very common, especially amongst adolescents. There is currently a debate about whether frequent use of these media might have adverse effects on health, especially on headaches, which are among the most-reported health complaints in adolescents. The aim of the present study was to assess associations between frequent use of electronic media and the prevalence of different types of headache in adolescents. Methods Data were derived from a population-based sample (n = 1,025, ages 13-17 years. Type of headache (i.e. migraine, tension-type headache, unclassifiable headache was ascertained by standardized questionnaires for subjects reporting headache episodes at least once per month during the last six months. Duration of electronic media use was assessed during personal interviews. Associations were estimated with logistic regression models adjusted for age group, sex, family condition and socio-economic status. Results Most of the adolescents used computers (85%, watched television (90% or listened to music (90% daily, otherwise only 23% of the participants used their mobile phones and only 25% played with game consoles on a daily basis. A statistically significant association between listening to music and any headache (odds ratio 1.8; 95% confidence interval 1.1-3.1 for 30 minutes per day, 2.1; 1.2-3.7 for 1 to 2 hours per day; 2.0; 1.2-3.5 for 3 hours and longer listening to music per day was observed. When stratifying for type of headache, no statistically significant association was seen. Conclusions Apart from an association between listening to music on a daily basis and overall headache, no consistent associations between the use of electronic media and different types of headache were observed.

  8. Hot testing of coke

    Energy Technology Data Exchange (ETDEWEB)

    Balon, I D

    1976-07-01

    Earlier investigations failed to take full account of the factors affecting coke behavior within the blast furnace. An apparatus was accordingly developed for testing coke, based on a cyclone furnace where the sample could be held in a flow of hot oxidizing gases, simulating conditions in the blast furnace hearth. The results are said to be suitable for comprehensive assessment of the coke, including abrasive strength and its rate of gasification in a flow of carbon dioxide. Coke of size 6-10 mm tested at 1,100/sup 0/C in an atmosphere of oxidizing gases close to those obtaining in the blast furnace hearth, indicated that destruction and total gasification of the coke occurs after 5 minutes for a weak coke and 8 minutes for strong coke, depending on the physico-chemical and physico-mechanical properties of the particular coke. When samples were treated for a fixed period (3 minutes), the amount of coke remaining, and the percentage over 6 mm varied between 22 and 40 and between 4 and 7 percent respectively.

  9. Hot Hydrogen Test Facility

    International Nuclear Information System (INIS)

    W. David Swank

    2007-01-01

    The core in a nuclear thermal rocket will operate at high temperatures and in hydrogen. One of the important parameters in evaluating the performance of a nuclear thermal rocket is specific impulse, ISp. This quantity is proportional to the square root of the propellant's absolute temperature and inversely proportional to square root of its molecular weight. Therefore, high temperature hydrogen is a favored propellant of nuclear thermal rocket designers. Previous work has shown that one of the life-limiting phenomena for thermal rocket nuclear cores is mass loss of fuel to flowing hydrogen at high temperatures. The hot hydrogen test facility located at the Idaho National Lab (INL) is designed to test suitability of different core materials in 2500 C hydrogen flowing at 1500 liters per minute. The facility is intended to test non-uranium containing materials and therefore is particularly suited for testing potential cladding and coating materials. In this first installment the facility is described. Automated Data acquisition, flow and temperature control, vessel compatibility with various core geometries and overall capabilities are discussed

  10. Nuclear viscosity of hot rotating 240Cf

    International Nuclear Information System (INIS)

    Shaw, N. P.; Dioszegi, I.; Mazumdar, I.; Buda, A.; Morton, C. R.; Velkovska, J.; Beene, J. R.; Stracener, D. W.; Varner, R. L.; Thoennessen, M.

    2000-01-01

    The absolute γ-ray/fission multiplicities from hot rotating 240 Cf, populated at seven bombarding energies using the reaction 32 S+ 208 Pb, are reported. Statistical model calculations including nuclear dissipation have been performed to extract the dependence of the nuclear viscosity on temperature and/or nuclear deformation. The extracted nuclear dissipation coefficient is found to be independent of temperature. Large dissipation during the saddle to scission path provides a good fit to the γ-ray spectra. (c) 2000 The American Physical Society

  11. HOT STARS WITH HOT JUPITERS HAVE HIGH OBLIQUITIES

    International Nuclear Information System (INIS)

    Winn, Joshua N.; Albrecht, Simon; Fabrycky, Daniel; Johnson, John Asher

    2010-01-01

    We show that stars with transiting planets for which the stellar obliquity is large are preferentially hot (T eff > 6250 K). This could explain why small obliquities were observed in the earliest measurements, which focused on relatively cool stars drawn from Doppler surveys, as opposed to hotter stars that emerged more recently from transit surveys. The observed trend could be due to differences in planet formation and migration around stars of varying mass. Alternatively, we speculate that hot-Jupiter systems begin with a wide range of obliquities, but the photospheres of cool stars realign with the orbits due to tidal dissipation in their convective zones, while hot stars cannot realign because of their thinner convective zones. This in turn would suggest that hot Jupiters originate from few-body gravitational dynamics and that disk migration plays at most a supporting role.

  12. Equity in healthcare for coronary heart disease, Wales (UK 2004-2010: A population-based electronic cohort study.

    Directory of Open Access Journals (Sweden)

    William King

    Full Text Available Despite substantial falls in coronary heart disease (CHD mortality in the United Kingdom (UK, marked socioeconomic inequalities in CHD risk factors and CHD mortality persist. We investigated whether inequity in CHD healthcare in Wales (UK could contribute to the observed social gradient in CHD mortality.Linking data from primary and secondary care we constructed an electronic cohort of individuals (n = 1199342 with six year follow-up, 2004-2010. We identified indications for recommended CHD interventions, measured time to their delivery, and estimated risk of receiving the interventions for each of five ordered deprivation groups using a time-to-event approach with Cox regression frailty models. Interventions in primary and secondary prevention included risk-factor measurement, smoking management, statins and antihypertensive therapy, and in established CHD included medication and revascularization. For primary prevention, five of the 11 models favoured the more deprived and one favoured the less deprived. For medication in secondary prevention and established CHD, one of the 15 models favoured the more deprived and one the less deprived. In relation to revascularization, six of the 12 models favoured the less deprived and none favoured the more deprived-this evidence of inequity exemplified by a hazard ratio for revascularization in stable angina of 0.79 (95% confidence interval 0.68, 0.92. The main study limitation is the possibility of under-ascertainment or misclassification of clinical indications and treatment from variability in coding.Primary care components of CHD healthcare were equitably delivered. Evidence of inequity was found for revascularization procedures, although this inequity is likely to have only a modest effect on social gradients in CHD mortality. Policymakers should focus on reducing inequalities in CHD risk factors, particularly smoking, as these, rather than inequity in healthcare, are likely to be key drivers of

  13. Electronic Health Record Effects on Work-Life Balance and Burnout Within the I3 Population Collaborative.

    Science.gov (United States)

    Robertson, Sandy L; Robinson, Mark D; Reid, Alfred

    2017-08-01

    Physician burnout is a problem that often is attributed to the use of the electronic health record (EHR). To estimate the prevalence of burnout and work-life balance satisfaction in primary care residents and teaching physicians, and to examine the relationship between these outcomes, EHR use, and other practice and individual factors. Residents and faculty in 19 primary care programs were anonymously surveyed about burnout, work-life balance satisfaction, and EHR use. Additional items included practice size, specialty, EHR characteristics, and demographics. A logistic regression model identified independent factors associated with burnout and work-life balance satisfaction. In total, 585 of 866 surveys (68%) were completed, and 216 (37%) respondents indicated 1 or more symptoms of burnout, with 162 (75%) attributing burnout to the EHR. A total of 310 of 585 (53%) reported dissatisfaction with work-life balance, and 497 (85%) indicated that use of the EHR affected their work-life balance. Respondents who spent more than 6 hours weekly after hours in EHR work were 2.9 times (95% confidence interval [CI] 1.9-4.4) more likely to report burnout and 3.9 times (95% CI 1.9-8.2) more likely to attribute burnout to the EHR. They were 0.33 times (95% CI 0.22-0.49) as likely to report work-life balance satisfaction, and 3.7 times (95% CI 2.1-6.7) more likely to attribute their work-life balance satisfaction to the EHR. More after-hours time spent on the EHR was associated with burnout and less work-life satisfaction in primary care residents and faculty.

  14. Theory of hot particle stability

    International Nuclear Information System (INIS)

    Berk, H.L.; Wong, H.V.; Tsang, K.T.

    1986-10-01

    The investigation of stabilization of hot particle drift reversed systems to low frequency modes has been extended to arbitrary hot beta, β/sub H/ for systems that have unfavorable field line curvature. We consider steep profile equilibria where the thickness of the pressure drop, Δ, is less than plasma radius, r/sub p/. The analysis describes layer modes which have mΔ/r/sub p/ 2/3. When robust stability conditions are fulfilled, the hot particles will have their axial bounce frequency less than their grad-B drift frequency. This allows for a low bounce frequency expansion to describe the axial dependence of the magnetic compressional response

  15. Hot workability of aluminium alloys

    International Nuclear Information System (INIS)

    Yoo, Yeon Chul; Oh, Kyung Jin

    1986-01-01

    Hot Workability of aluminium alloys, 2024, 6061 and 7075, has been studied by hot torsion tests at temperatures from 320 to 515 deg C and at strain rates from 1.26 x 10 -3 to 5.71 x 10 -3 sec -1 . Hot working condition of these aluminium alloys was determined quantitatively from the constitutive equations obtained from flow stress curves in torsion. Experimental data of the logarith of the Zener-Hollomonn parameter showed good linear relationships to the logarith of sinh(ασ-bar)

  16. Printed Electronics

    Science.gov (United States)

    Wade, Jessica; Hollis, Joseph Razzell; Wood, Sebastian

    2018-04-01

    The combination of printing technology with manufacturing electronic devices enables a new paradigm of printable electronics, where 'smart' functionality can be readily incorporated into almost any product at low cost. Over recent decades, rapid progress has been made in this field, which is now emerging into the industrial andcommercial realm. However, successful development and commercialisation on a large scale presents some significant technical challenges. For fully-printable electronic systems, all the component parts must be deposited from solutions (inks), requiring the development of new inorganic, organic and hybrid materials.A variety of traditional printing techniques are being explored and adapted forprinting these new materials in ways that result in the best performing electronicdevices. Whilst printed electronics research has initially focused on traditional typesof electronic device such as light-emitting diodes, transistors, and photovoltaics, it is increasingly apparent that a much wider range of applications can be realised. The soft and stretchable nature of printable materials makes them perfect candidates forbioelectronics, resulting in a wealth of research looking at biocompatible printable inks and biosensors. Regardless of application, the properties of printed electronicmaterials depend on the chemical structures, processing conditions, device architecture,and operational conditions, the complex inter-relationships of which aredriving ongoing research. We focus on three particular 'hot topics', where attention is currently focused: novel materials, characterisation techniques, and device stability. With progress advancing very rapidly, printed electronics is expected to grow over the next decade into a key technology with an enormous economic and social impact.

  17. The Impact of Ceramic Shell Strength on Hot Tearing during Investment Casting

    International Nuclear Information System (INIS)

    Norouzi, Saeid; Farhangi, Hassan

    2011-01-01

    The effect of ceramic shell strength on hot tearing susceptibility during solidification was inspected practicing investment casting of the cobalt-base superalloy samples with the same casting conditions, but different ceramic shell systems. Results showed that the lower the ceramic shell strength upon using polymer additives, the lower the hindered contraction rate, and the lower the hindered contraction rate, the smaller the hot tearing tendency. Optical microscopy and electron microscopy scanning revealed that the hot tear propagated along the last solidified interdendritic phase, and that the hot tear surface had two major modes: 1) the ductile region in the outer layer; and 2) the inner region of liquid embrittlement.

  18. Hot Hydrogen Heat Source Development

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of this project is to develop a  hot hydrogen heat source that would produce  a high temperature hydrogen flow which would be comparable to that produced...

  19. The decay of hot nuclei

    International Nuclear Information System (INIS)

    Moretto, L.G.; Wozniak, G.J.

    1988-11-01

    The formation of hot compound nuclei in intermediate-energy heavy ion reactions is discussed. The statistical decay of such compound nuclei is responsible for the abundant emission of complex fragments and high energy gamma rays. 43 refs., 23 figs

  20. Mercury content in Hot Springs

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, R

    1974-01-01

    A method of determination of mercury in hot spring waters by flameless atomic absorption spectrophotometry is described. Further, the mercury content and the chemical behavior of the elementary mercury in hot springs are described. Sulfide and iodide ions interfered with the determination of mercury by the reduction-vapor phase technique. These interferences could, however, be minimized by the addition of potassium permanganate. Waters collected from 55 hot springs were found to contain up to 26.0 ppb mercury. High concentrations of mercury have been found in waters from Shimoburo Springs, Aomori (10.0 ppb), Osorezan Springs, Aomori (1.3 approximately 18.8 ppb), Gosyogake Springs, Akita (26.0 ppb), Manza Springs, Gunma (0.30 approximately 19.5 ppb) and Kusatu Springs, Gunma (1.70 approximately 4.50 ppb). These hot springs were acid waters containing a relatively high quantity of chloride or sulfate.