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Sample records for helium compatibility studies

  1. The compatibility of candidate first wall metallic materials with impure helium

    Noda, T.; Okada, M.; Watanabe, R.

    1979-01-01

    The compatibilities of SUS 316 stainless steels, Nimonic PE 16, Nb-1% Zr, V-25% Mo, Mo, and TZM with the commercial grade helium (> 99.995%) and the helium containing oxygen of 13 vpm at temperatures from 873 to 1273 K were studied. SUS 316 and PE 16 were internally oxidized above 1100 K. The marked depletion of Cr and Mn in SUS 316 specimens was observed in the commercial grade helium above around 1100 K. Nb-1% Zr and V-25% Mo extremely absorbed oxygen and nitrogen from the helium gases and were deteriorated in the range of test temperatures. Mo and TZM appeared not to be affected by the exposure to the commercial grade helium at temperature up to 1273 K. However, Mo and TZM lost ductility at room temperature after exposure to helium above 1100 and 900 K respectively. (orig.)

  2. Compatibility of vanadium alloys with reactor-grade helium for fusion reactor applications

    Bell, G.E.C.; Bishop, P.S.

    1993-01-01

    Tests were conducted to determine the compatibility of vanadium alloys with reactor-grade helium and to define the helium gas chemistry requirements for fusion reactors, miniature tensile specimens of V-5Cr-5Ti. V-10Cr-5Ti, and V-12.5Cr-5 Ti were exposed in a once-through system to helium with 70 vppm-H 2 (measured oxygen partial pressures of 10 -12 atm) and bottle helium (measured oxygen partial pressures of -4 atm) between 500 and 700 degree C for up to 1008 h. The weight changes in the specimens were recorded. The helium-exposed specimens were tensile tested, and the effects of exposure on mechanical properties were assessed. Exposure between 500 and 700 degree C for 1008 h in He+70 vppm-H 2 resulted in complete embrittlement of all the alloys in room temperature tensile tests. The fracture mode was primarily cleavage, probably caused by a hydrogen-induced shift in the ductile to brittle transition temperature (DBTT). Weight gains increased with temperature and were largest for the V-5Cr-5Ti alloy. Specimens exposed for 531 h between 500 and 700 degree C in bottle He exhibited two distinct fracture morphologies on the fracture surfaces. Brittle cleavage around the edges of specimens gave way to ductile dimpling in the center of the specimens. The brittle region around the periphery of the specimen is most likely the highest vanadium oxide. V 2 O 5

  3. Resistivity studies of interstitial helium mobility in niobium

    Chen, C.G.; Birnbaum, H.K.; Johnson, A.B. Jr.

    1979-01-01

    The mobility of interstitial helium in Nb and Nb-O alloys was studied in the temperature range of 10-383 K using resistivity measurements. The helium was introduced by radioactive decay of solute tritium (approximately 1 at%). At T < 100 K the resistivity increased due to conversion of tritium trapped at oxygen interstititals to helium. The formation of helium caused a very significant resistance increase at room temperature and above. The results suggest that helium is mobile at temperatures above 295 K and that the precipitation of large helium bubbles occurs along grain boundaries. The mobile helium species may either be single interstitials or small helium clusters. The activation enthalpy for the diffusion of the mobile helium species was estimated to be about 55 kJ/mol (0.66 eV). (Auth.)

  4. A Study of Confined Helium Atom

    Xie Wenfang

    2007-01-01

    The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.

  5. Study of a microwave discharge in argon/helium mixtures

    Saada, Serge

    1983-01-01

    A discharge created by a surface wave in Argon-Helium mixture is studied. First, the helium influence on plasma parameters has been studied (electron density, electric field, effective collision frequency, etc...), then, on excitation processes in the discharge. Relations between plasma lines, electron density and electric field have been established. [fr

  6. Neutron scattering study of dynamical properties of liquid helium confined into porous media

    Albergamo, Francesco

    2001-01-01

    The study of liquid helium confined into porous materials should allow for a better understanding of the relation between superfluidity and Bose-Einstein condensation, lacking, at present, o f a satisfactory theoretical description. Experiments on confined liquid helium are quite difficult and samples should be prepared very carefully. One should know at best the confining material characteristics and should control the actual filling status of the porous sample. To achieve this condition, we added an experimental stage to the procedure commonly used in the studies conducted insofar. We conducted helium adsorption isotherms on each porous sample supposed to be used a s a confining sample. In this way we were able to know, with an high degree of precision, the amount of helium necessary to fill the porous sample. We also get information on macroscopic phenomena occurring during the filling procedure. Some experimental tricks have been used in order to avoid condensation of liquid helium into the injection capillary. Two inelastic neutron scattering techniques have been used in order to get information respectively on the mean kinetic energy per particle and on the elementary excitations spectrum. The kinetic energy measurements showed that confinement is responsible for a rise in this quantity. The elementary excitations measurements showed a correspondence between the capillary condensation process (detected by helium adsorption isotherms measurements) and the presence of elementary excitations typical of the liquid helium. Moreover, the long-wavelength elementary excitations are found to be perturbed in a way compatible with the system geometry. An intrinsic (at T=0.4 K) width of the roton peak is also found. (author) [fr

  7. Parametric study of radiofrequency helium discharge under ...

    The excitation temperatures in the α and γ modes were 3266 and 4500 K respectively, evaluated by Boltzmann's plot method. The estimated gas temperature increased from 335 K in the α mode to 485 K in the γ mode, suggesting that the radio frequency atmospheric pressure helium discharge can be used for surface ...

  8. Studies of helium distribution in metal tritides

    Bowman, R.C. Jr.; Attalla, A.

    1976-01-01

    The distribution of helium ( 3 He) in LiT, TiT 2 , and UT 3 , which are regarded as representative metal tritides, was investigated using pulse nuclear magnetic resonance (NMR) techniques. Analyses of the NMR lineshapes and nuclear relaxation times indicate the 3 He atoms are trapped in microscopic gas bubbles for each tritide. The effects of concentration and temperature on the 3 He distributions were investigated as well

  9. Studies of waste-canister compatibility

    McCoy, H.E.

    1983-01-01

    Compatibility studies were conducted between 7 waste forms and 15 potential canister structural materials. The waste forms were Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus silicon carbide. The canister materials included carbon steel (bare and with chromium or nickel coatings), copper, Monel, Cu-35% Ni, titanium (grades 2 and 12), several Inconels, aluminum alloy 5052, and two stainless steels. Tests of either 6888 or 8821 h were conducted at 100 and 300 0 C, which bracket the low and high limits expected during storage. Glass and FUETAP evolved sulfur, which reacted preferentially with copper, nickel, and alloys of these metals. The Pb-Sn matrix alloy stuck to all samples and the carbon-coated particles to most samples at 300 0 C, but the extent of chemical reaction was not determined. Testing for 0.5 h at 800 0 C was included because it is representative of a transportation accident and is required of casks containing nuclear materials. During these tests (1) glass and FUETAP evolved sulfur, (2) FUETAP evolved large amounts of gas, (3) Synroc stuck to titanium alloys, (4) glass was molten, and (5) both matrix alloys were molten with considerable chemical interactions with many of the canister samples. If this test condition were imposed on waste canisters, it would be design limiting in many waste storage concepts

  10. A Neutron Scattering Study of Collective Excitations in Superfluid Helium

    Graf, E. H.; Minkiewicz, V. J.; Bjerrum Møller, Hans

    1974-01-01

    Extensive inelastic-neutron-scattering experiments have been performed on superfluid helium over a wide range of energy and momentum transfers. A high-resolution study has been made of the pressure dependence of the single-excitation scattering at the first maximum of the dispersion curve over...... of the multiexcitation scattering was also studied. It is shown that the multiphonon spectrum of a simple Debye solid with the phonon dispersion and single-excitation cross section of superfluid helium qualitatively reproduces these data....

  11. A molecular dynamics study of helium bombardments on tungsten nanoparticles

    Li, Min; Hou, Qing; Cui, Jiechao; Wang, Jun

    2018-06-01

    Molecular dynamics simulations were conducted to study the bombardment process of a single helium atom on a tungsten nanoparticle. Helium atoms ranging from 50 eV to 50 keV were injected into tungsten nanoparticles with a diameter in the range of 2-12 nm. The retention and reflection of projectiles and sputtering of nanoparticles were calculated at various times. The results were found to be relative to the nanoparticle size and projectile energy. The projectile energy of 100 eV contributes to the largest retention of helium atoms in tungsten nanoparticles. The most obvious difference in reflection exists in the range of 3-10 keV. Around 66% of sputtering atoms is in forward direction for projectiles with incident energy higher than 10 keV. Moreover, the axial direction of the nanoparticles was demonstrated to influence the bombardment to some degree.

  12. Contribution to magnetic refrigeration study at liquid helium study

    Lacaze, A.

    1985-10-01

    An experimental prototype of magnetic refrigerator operates, following a Carnot cycle, with gallium gadolinium garnet, from liquid helium at 4.2 0 K. Analysis of the cyle and heat exchanges allowed to improve performance up to get more than 50% of Carnot yield at 1.8 0 K and nearly 80% at 2.1 0 K. Operation conditions of a regenerator refrigerator between 4 and 20 0 K are studied. The association of a magnetic refrigerator and a gas refrigerator is analyzed. Among different ways to realize the magnetic stage, an active regenerator cycle is chosen. An experimental device is described [fr

  13. Studies of environmental compatability. Umweltbundesamt - Texte

    1982-01-01

    The evaluation of the methodical quality of the examples by means of a verification pattern had the result that approaches using quantitative methods - as for example the value in use analysis obtained better results: The representation of the state of the environment and of possible impairments of the environment, which had bejudged, achieved a higher degree of representativeness and completeness. Furthermore the concreteness of the used criteria for the description of the repercussions of a plan and the possibility to quantify same had to be judged more favourable. It must critically be remarked that by using quantitative methods difficulties may appear if impairments of the environment overlap or if there are correlations between the media respectively if there are non-linear repercussions of measures causing environmental damages. The present level of research should be developed to a strenghtened inclusion of complex and dynamic correlations of effects. More exacting investigations concerning environmental compatability are on the long term integrated in administrative procedures only at few authorities. With the demand for an extension of environmental compatability assessment to all steps of planning and procedure for the realization of a plan an early and more intensive participation of the public should be connected.

  14. IBA studies of helium mobility in nuclear materials revisited

    Trocellier, P., E-mail: patrick.trocellier@cea.fr [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Agarwal, S.; Miro, S. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Vaubaillon, S. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); CEA, INSTN, UEPTN, F-91191 Gif-sur-Yvette (France); Leprêtre, F.; Serruys, Y. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France)

    2015-12-15

    The aim of this paper is to point out and to discuss some features extracted from the study of helium migration in nuclear materials performed during the last fifteen years using ion beam analysis (IBA) measurements. The first part of this paper is devoted to a brief description of the two main IBA methods used, i.e. deuteron induced nuclear reaction for {sup 3}He depth profiling and high-energy heavy-ion induced elastic recoil detection analysis for {sup 4}He measurement. In the second part, we provide an overview of the different studies carried out on model nuclear waste matrices and model nuclear reactor structure materials in order to illustrate and discuss specific results in terms of key influence parameters in relation with thermal or radiation activated migration of helium. Finally, we show that among the key parameters we have investigated as able to influence the height of the helium migration barrier, the following can be considered as pertinent: the experimental conditions used to introduce helium (implanted ion energy and implantation fluence), the grain size of the matrix, the lattice cell volume, the Young's modulus, the ionicity degree of the chemical bond between the transition metal atom M and the non-metal atom X, and the width of the band gap.

  15. Study of damage and helium diffusion in fluoro-apatites

    Miro, S.

    2004-12-01

    This work lies within the scope of the study of the radionuclides containment matrices. The choice of the fluoro-apatites as potential matrices of containment was suggested by the notable properties of these latter (thermal and chemical stability even under radioactive radiation). By irradiations with heavy ions and a helium implantation we simulated the effects related to the alpha radioactivity and to the spontaneous nuclear fission of the radionuclides. Thanks to the study of Durango fluoro-apatite single crystals and fluoro-apatite sintered ceramics, we evidenced that the damage fraction as well as the unit cell deformations increase with the electronic energy loss and with the substitution. These effects are followed at high fluences by a phenomenon of re-crystallization. The study of the helium diffusion points out that the thermal diffusion process improves with the substitution and strongly increases with heavy ions irradiation. (author)

  16. Studies on compatibility of energetic materials by thermal methods

    Maria Alice Carvalho Mazzeu

    2010-04-01

    Full Text Available The chemical compatibility of explosives, pyrotechnics and propellants with those materials is studied to evaluate potential hazards when in contact with other materials during production, storage and handling. Compatibility can be studied by several thermal methods as DSC (differential scanning calorimetry, TG (Thermogravimetry, VST (Vacuum stability test and others. The test methods and well defined criteria are the most important elements when a compatibility study is being accomplished. In this paper, the compatibility of two very important high explosives used in ammunition, RDX (Cyclo-1,3,5-trimethylene-2,4,6-trinitramine and HMX (Cyclotetramethylene tetranitramine was studied with the materials: fluoroelastomer (Viton and powdered aluminum (Al, using DSC and VST methods. The criteria to judge the compatibility between materials is based on a standardization agreement (STANAG 4147, 2001, and the final conclusion is that explosives and this materials are compatible, but in DSC it was observed that the peak of decomposition temperature of the admixture of RDX with Al decreased in 3º C and another peak appeared after the decomposition peak.

  17. Design study on the helium engineering demonstration loop (HENDEL)

    Aochi, Tetsuo; Yasuno, Takehiko; Muto, Yasushi; Suzuki, Kunihiko

    1977-11-01

    Four reference studies made on Helium Engineering Demonstration Loop (HENDEL) are described. HENDEL is used in confirmation of the designs of VHTR components such as reactor structure, core structure, intermediate heat exchanger and piping. It consists of mother loop, adapter section and four test sections for fuel stack, reactor support and insulation structure, core structure and high temperature heat transfer component respectively. System and component designs of the mother and adapter section and preliminary designs of the four test sections are shown. And, the plans of operation, instrumentation, control, safety, utilities (electricity, cooling water and helium gas) and construction schedule of HENDEL and research and development of the test sections are also briefed. (auth.)

  18. Damage studies on tungsten due to helium ion irradiation

    Dutta, N.J.; Buzarbaruah, N.; Mohanty, S.R.

    2014-01-01

    Highlights: • Used plasma focus helium ion source to study radiation induced damage on tungsten. • Surface analyses confirm formation of micro-crack, bubbles, blisters, pinholes, etc. • XRD patterns confirm development of compressive stress due to thermal load. • Reduction in hardness value is observed in the case of exposed sample. - Abstract: Energetic and high fluence helium ions emitted in a plasma focus device have been used successfully to study the radiation induced damage on tungsten. The reference and irradiated samples were characterized by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of cracks of micrometer width. However at higher magnification, various types of crystalline defects such as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating accumulation of compressive stress due to the heat load delivered by helium ions. A marginal reduction in hardness of the irradiated sample is also noticed

  19. The study of the influence of helium on the counter's measurement properties

    Guan Rui; Weng Kuiping; Ren Xingbi

    2009-04-01

    In measurement of tritium by the proportional counter, methane is usually used as counter gas. Gas samples have been made with helium and methane in the proportion of concentration and measured to study the influence of helium on the counter's measurement properties. Then gas sample with tritium and helium has been measured, and the result is according with anticipation. The experiment has showed that the plateau curve of counter could be changed by helium, but the influence could be ignored when helium concentration less 10%. (authors)

  20. Liquid helium

    Atkins, K R

    1959-01-01

    Originally published in 1959 as part of the Cambridge Monographs on Physics series, this book addresses liquid helium from the dual perspectives of statistical mechanics and hydrodynamics. Atkins looks at both Helium Three and Helium Four, as well as the properties of a combination of the two isotopes. This book will be of value to anyone with an interest in the history of science and the study of one of the universe's most fundamental elements.

  1. Fusion-reactor blanket-material safety-compatibility studies

    Jeppson, D.W.; Muhlestein, L.D.; Keough, R.F.; Cohen, S.

    1982-11-01

    Blanket material selection for fusion reactors is strongly influenced by the desire to minimize safety and environmental concerns. Blanket material safety compatibility studies are being conducted to identify and characterize blanket-coolant-material interactions under postulated reactor accident conditions. Recently completed scoping compatibility tests indicate that : (1) ternary oxides (LiAlO 2 , Li 2 ZrO 3 , Li 2 SiO 3 , Li 4 SiO 4 and LiTiO 3 ) at postulated blanket operating temperatures are compatible with water coolant, while liquid lithium and Li 7 Pb 2 alloy reactions with water generate heat, aerosol and hydrogen; (2) lithium oxide and Li 17 Pb 83 alloy react mildly with water requiring special precautions to control hydrogen release; (3) liquid lithium reacts substantially, while Li 17 Pb 83 alloy reacts mildly with concrete to produce hydrogen; and (4) liquid lithium-air reactions present some major safety concerns

  2. Theoretical Study of Triatomic Systems Involving Helium Atoms

    Suno, H.; Hiyama, E.; Kamimura, M.

    2013-01-01

    The triatomic 4 He system and its isotopic species 4 He 2 3 He are theoretically investigated. By adopting the best empirical helium interaction potentials, we calculate the bound state energy levels as well as the rates for the three-body recombination processes: 4 He + 4 He + 4 He → 4 He 2 + 4 He and 4 He + 4 He + 3 He → 4 He 2 + 3 He. We consider not only zero total angular momentum J = 0 states, but also J > 0 states. We also extend our study to mixed helium-alkali triatomic systems, that is 4 He 2 X with X = 7 Li, 23 Na, 39 K, 85 Rb, and 133 Cs. The energy levels of all the J ≥ 0 bound states for these species are calculated as well as the rates for three-body recombination processes such as 4 He + 4 He + 7 Li → 4 He 2 + 7 Li and 4 He + 4 He + 7 Li → 4 He 7 Li + 4 He. In our calculations, the adiabatic hyperspherical representation is employed but we also obtain preliminary results using the Gaussian expansion method. (author)

  3. Thermalization of positronium in helium: A numerical study

    Marjanovic, S.; Suvakov, M. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Engbrecht, J.J. [Saint Olaf College, Northfield, MN 55057 (United States); Petrovic, Z.Lj., E-mail: zoran@ipb.ac.rs [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)

    2012-05-15

    In this paper we present a numerical study of positronium (Ps) thermalization in pure helium (He). Recent measurements of Ps thermalization yielded data that were analyzed to produce the scattering cross-sections in helium by using energy balance equations with an assumption of a Maxwell-Boltzmann distribution (MBD) function for Ps. We have applied a Monte Carlo code to test the cross-sections. As our code was developed without any approximations for the energy distribution function we have effectively also tested the assumptions and the validity of the simple theory based on Maxwellian distributions. We present the simulation results using the simulation technique that is limited only by the accuracy of the available cross-sections. We calculate thermalization profiles for several theoretical and measured cross-sections. Also, the temporal evolution of energy distributions has been shown along with diffusion coefficients and spatial ranges of penetration. Thermalization of the initial distribution is rapid and the data follow relatively closely, those calculated in recent experiment, which supports the choice of MBD and the obtained cross-section. However the distribution function most of the time deviates from the MBD due to strong scattering. Finally, we applied the same procedure to analyze Ps thermalization in water vapor.

  4. THE COMPATIBILITY STUDENT CHOICE OF UNIVERSITY MAJORING; A PRELIMINARY STUDIES

    Daharnis Daharnis

    2016-06-01

    Full Text Available The continuous improvements in order to optimize the basic education to higher education are still running. Based on that purpose, there are many factors to supporting the students' learning activities success; one of the factors is suitability with majors in university. The purpose of this study is to reveal the condition of the compatibility of students majoring with their interest, then to describe the information when the student choose their majoring. Samples in this study were 122 peoples, taken by random sampling from the Padang State University. Data obtained by distributing questionnaires. The results showed that there are students that their major do not match with their interest (22.13%, only 3.28% of students who feel compatible with their major. This result should be a major concern, particularly for counselor in schools for design counseling services to solve these problems. The result of this study used as a grand tour or a preliminary study for further research.

  5. Study of the partonic structure of the helium nucleus

    Perrin, Y.

    2012-01-01

    The structure of the nucleons and of the nuclei was actively studied during the twentieth century through electron elastic scattering (measuring the electromagnetic form factors) and deep inelastic electron scattering (measuring the parton distributions). The formalism of generalized parton distributions (GPD) achieved the unification of the form factors and the parton distributions. This link gives a source of information about parton dynamics, such as the distribution of nuclear forces and orbital momentum inside hadrons. The easiest experimental access to the GPD is the deeply virtual Compton scattering (DVCS), which corresponds to the hard electroproduction of a real photon. While several experiments focussed on DVCS off the nucleon, only a few experiments studied DVCS off a nuclear target. This thesis deals with the study of the coherent channel of DVCS off helium 4, with the aim of extracting the real and imaginary parts of the Compton form factor thanks to the beam spin asymmetry. (author)

  6. Helium transport and exhaust studies in enhanced confinement regimes in DIII-D

    Wade, M.R.; Hillis, D.L.; Hogan, J.T.; Mahdavi, M.A.; Maingi, R.; West, W.P.; Burrell, K.H.; Finkenthal, D.F.; Gohil, P.; Groebner, R.J.

    1995-02-01

    A better understanding of helium transport in the plasma core and edge in enhanced confinement regimes is now emerging from recent experimental studies on DIII-D. Overall, the results are encouraging. Significant helium exhaust (τ* He /τ E ∼ 11) has been obtained in a diverted, ELMing H-mode plasma simultaneous with a central source of helium. Detailed analysis of the helium profile evolution indicates that the exhaust rate is limited by the exhaust efficiency of the pump (∼5%) and not by the intrinsic helium transport properties of the plasma. Perturbative helium transport studies using gas puffing have shown that D He /X eff ∼1 in all confinement regimes studied to date (including H-mode and VH-mode). Furthermore, there is no evidence of preferential accumulation of helium in any of these regimes. However, measurements in the core and pumping plenum show a significant dilution of helium as it flows from the plasma core to the pumping plenum. Such dilution could be the limiting factor in the overall removal rate of helium in a reactor system

  7. MRI Compatibility of Robot Actuation Techniques – A Comparative Study

    Fischer, Gregory S.; Krieger, Axel; Iordachita, Iulian; Csoma, Csaba; Whitcomb, Louis L.; Fichtinger, Gabor

    2008-01-01

    This paper reports an experimental evaluation of the following three different MRI-compatible actuators: a Shinsei ultrasonic motor, a Nanomotion ultrasonic motor and a pneumatic cylinder actuator. We report the results of a study comparing the effect of these actuators on the signal to noise ratio (SNR) of MRI images under a variety of experimental conditions. Evaluation was performed with the controller inside and outside the scanner room and with both 1.5T and 3T MRI scanners. Pneumatic cy...

  8. Improved Study of the Antiprotonic Helium Hyperfine Structure

    Pask, T.; Dax, A.; Hayano, R.S.; Hori, M.; Horvath, D.; Juhasz, B.; Malbrunot, C.; Marton, J.; Ono, N.; Suzuki, K.; Zmeskal, J.; Widmann, E.

    2008-01-01

    We report the initial results from a systematic study of the hyperfine (HF) structure of antiprotonic helium (n,l) = (37,~35) carried out at the Antiproton Decelerator (AD) at CERN. We performed a laser-microwave-laser resonance spectroscopy using a continuous wave (cw) pulse-amplified laser system and microwave cavity to measure the HF transition frequencies. Improvements in the spectral linewidth and stability of our laser system have increased the precision of these measurements by a factor of five and reduced the line width by a factor of three compared to our previous results. A comparison of the experimentally measured transition frequencies with three body QED calculations can be used to determine the antiproton spin magnetic moment, leading towards a test of CPT invariance.

  9. Design and study of Engineering Test Facility - Helium Circulator

    Jiang Huijing; Ye Ping; Zhao Gang; Geng Yinan; Wang Jie

    2015-01-01

    Helium circulator is one of the key equipment of High-temperature Gas-cooled Reactor Pebble-bed Module (HTR-PM). In order to simulate most normal and accident operating conditions of helium circulator in HTR-PM, a full scale, rated flow rate and power, engineering test loop, which was called Engineering Test Facility - Helium Circulator (ETF-HC), was designed and established. Two prototypes of helium circulator, which was supported by Active Magnetic Bearing (AMB) or sealed by dry gas seals, would be tested on ETF-HC. Therefore, special interchangeable design was under consideration. ETF-HC was constructed compactly, which consisted of eleven sub-systems. In order to reduce the flow resistance of the circuit, special ducts, elbows, valves and flowmeters were selected. Two stages of heat exchange loops were designed and a helium - high pressure pure water heat exchanger was applied to ensure water wouldn't be vaporized while simulating accident conditions. Commissioning tests were carried out and operation results showed that ETF-HC meets the requirement of helium circulator operation. On this test facility, different kinds of experiments were supposed to be held, including mechanical and aerodynamic performance tests, durability tests and so on. These tests would provide the features and performance of helium circulator and verify its feasibility, availability and reliability. (author)

  10. Helium 3 precipitation in AISI 316L stainless steel induced by radioactive decay of tritium: Microstructural study of helium bubble precipitation

    Brass, A.M.; Chene, J.

    1994-01-01

    The development of the thermonuclear technology has given rise to a renewed interest in the study of the behavior of helium in metals. A great amount of work is still required for the understanding of the role of helium on the mechanical properties of structural materials for fusion technology, especially austenitic stainless steels. This article deals with the study of the influence of thermomechanical heat treatments, aging conditions (temperature and time), and helium concentration of helium bubble precipitation in a 316L austenitic steel. Helium was generated by the radioactive decay of tritium (tritium trick). Helium bubbles impede the grain growth in 316L steel aged at 1,373 K and also the recrystallization reaction at this temperature if cold working is performed prior to aging. Transmission electron microscopy (TEM) observations indicated a weak helium precipitation at 1,073 and 1,223 K, presumably due to the presence of trapping sites for tritium, and no bubble growth after aging up to 100 hours. Precipitation sites are mainly dislocations in the matrix at 1,073 K and grain boundaries and individual dislocations in the matrix at 1,223 K. The large bubble size (50 nm) observed at 1,373 K, even for short aging times (0.083), can partly be attributed to bubble dragging by dislocations toward the grain boundaries. Cold deformation prior to aging leads to a larger bubble size due to growth enhancement during recrystallization. Decreasing the helium content leads to a smaller helium bubble size and density. Tritium trapping at helium bubbles may favor helium 3 accumulation on defects such as grain boundaries, as observed by tritium autoradiography

  11. Simulation study of radiation damage induced by energetic helium nuclei

    Hoang Dac Luc; Vo Tuong Hanh; Hoang Dac Dat

    2003-01-01

    High energy alpha particles produced by neutron-induced nuclear reactions can damage severely reactor materials. Simulation of this process is described using theoretical calculation and ion irradiation experiments at different displacement doses and Helium doses. (author)

  12. Simulation study of radiation damage induced by energetic helium nuclei

    Hoang Dac Luc; Hoang Dac Dat

    2003-01-01

    High energy alpha particles produced by neutron-induced nuclear reactions can damage severely reactor materials. Simulation of this process is described using theoretical calculation and ion irradiation experiments at different displacement doses and Helium doses.

  13. Henry's law and accumulation of weak source for crust-derived helium: A case study of Weihe Basin, China

    Yuhong Li

    2017-12-01

    Full Text Available Crust-derived helium is generated from the radioactive decay of uranium, thorium and other radioactive elements in geological bodies. Compared with conventional natural gas, helium is a typical weak source gas as a result of extremely slow generation rate and absence of helium-generating peak. It is associated with methane or carbon dioxide reservoirs frequently and related to groundwater closely. Helium can meet the industry standard with 0.1% in volume fraction. In order to study the accumulation mechanism of helium, the previous research on Henry's coefficient and solubility of helium, nitrogen and methane are summarized and the key roles of Henry's Law in the helium migration, accumulation and preservation are discussed by simulating calculation taking Weihe Basin as an example. According to the Law, the gas solubility in dilute solution is controlled by the gas partial pressure and the Henry's coefficient. Compared with the carrier gases, the Henry's constant of helium is high, with striking difference at low and high temperature. In addition, the helium partial pressure is greatly different in helium source rocks and gas reservoirs, resulting in the great differences of helium solubility in the two places. The accumulation progresses are as follows. Firstly, helium can dissolve into water and migrate out of helium source rocks due to the high helium solubility, which is caused by high helium partial pressure and high temperature in source rock. Secondly, when dissolved helium is transported to the shallow gas reservoir, it is prone to be out of solution and into reservoir due to the extremely low partial pressure and low temperature. Meanwhile part of carrier gases dissolves into water, as if helium is “replaced” out. Furthermore, the low concentration funnel of dissolved helium is formed near the gas reservoir, then other dissolved helium continues to migrate towards the gas reservoir, which greatly improves the helium accumulation

  14. Contribution to the experimental study of the polarized liquid helium-3; Contributions a l'etude experimentale de l'helium-3 liquide polarise

    Villard, B

    1999-07-15

    Spin-polarized liquid helium-3 is prepared by laser optical pumping in low magnetic field and at room temperature, prior to fast liquefaction of the polarized sample. The use of a new helium-3 cryostat enabled us to obtain liquid helium-3 with polarization rates up to 25 % at well-stabilized temperatures (around 0.5 K). We could thereby study the effect of nuclear polarization on liquid-vapour equilibrium, and particularly on the saturated vapour pressure. Very sensitive capacitive gauges were developed. We estimated (to first order in M{sup 2}) the expected effects when the polarization M is suddenly destroyed. These effects were experimentally observed in helium-3/helium-4 mixtures, in pure helium-3, only a transient increase in pressure has been recorded. We then describe in a third part a preliminary experiment which aimed at determining the longitudinal relaxation time T1 in mixtures. Relaxation on the walls is efficiently reduced by a cesium coating and T1s of order 20 minutes were observed. A careful determination of the helium-3 concentration in the liquid phase was made. Finally we studied the effects of dipolar field on transverse polarisation decay in our strongly polarized samples. We observed the free precession of polarization after a NMR pulse, and analysed in detail its decay time constant as a function of different parameters. This time constant drastically varied with the tipping angle, an effect which could be linked to NMR dynamical instabilities. (author)

  15. Container-content compatibility studies: a pharmaceutical team's integrated approach.

    Laschi, Alda; Sehnal, Natacha; Alarcon, Antoine; Barcelo, Beatrice; Caire-Maurisier, François; Delaire, Myriam; Feuilloley, Marc; Genot, Stéphanie; Lacaze, Catherine; Pisarik, Luc; Smati, Christophe

    2009-01-01

    Container-content compatibility studies are required as part of the submission of a new product market authorization file or for a change relating to the primary product-contact packaging. Many regulatory publications and guidances are available in the USA, Europe, and Japan. However these publications and guidances are not sufficiently precise enough to allow for consistent interpretation and implementation of the technical requirements. A working group has been formed by the French Society of Pharmaceutical Science and Technology (SFSTP) in order to propose guidance for container-content interaction studies that meet both European and US requirements, and allows consistent and standardized information to be presented by the industry to the regulators. When a pharmaceutical drug product remains in prolonged contact with a material, the two critical points to consider are the drug product's quality and safety. A pharmaceutical evaluation of the container-content relationship should be done based on the knowledge of the contact material (e.g., type, physicochemical properties), its manufacturing processes (e.g., the type of sterilization that could potentially alter the interactions), and the formulation components involved in contact with this material (e.g., physicochemical properties, pharmaceutical presentation, route of administration). Quality is evaluated using the stability study performed on the product. Safety is partially evaluated with the stability study and is analyzed in conjunction with toxicity testing, specifically with cytotoxicity testing. The toxicity aspect is the key point of the container-content compatibility study and of patient safety. Migration tests are conducted when an interaction is suspected, or found based on previous results, to identify the component responsible for this interaction and to help select a new material if needed. Therefore, such tests are perhaps not the best ones to use for the purpose of safety evaluation

  16. Study of equation-of-state of dense helium

    Cai Lingcang; Zhang Lin; Xiang Shikai; Jing Fuqian

    2001-01-01

    Hugoniot EOS, shock temperature of gas helium plasma (the initial pressure is 1.2 MPa and the initial temperature is 293 K) are measured with the help of shock compression technique and transient radiation pyrometer. The experimental Hugoniot data are good agreement with the theoretical prediction by Saha equation pus Debye-Huckel correction

  17. MRI compatibility of robot actuation techniques--a comparative study.

    Fischer, Gregory S; Krieger, Axel; Iordachita, Iulian; Csoma, Csaba; Whitcomb, Louis L; Gabor, Fichtinger

    2008-01-01

    This paper reports an experimental evaluation of the following three different MRI-compatible actuators: a Shinsei ultrasonic motor a Nanomotion ultrasonic motor and a pneumatic cylinder actuator. We report the results of a study comparing the effect of these actuators on the signal to noise ratio (SNR) of MRJ images under a variety of experimental conditions. Evaluation was performed with the controller inside and outside the scanner room and with both 1.5T and 3T MRI scanners. Pneumatic cylinders function with no loss of SNR with controller both inside and outside of the scanner room. The Nanomotion motor performs with moderate loss of SNR when moving during imaging. The Shinsei is unsuitable for motion during imaging. All may be used when motion is appropriately interleaved with imaging cycles.

  18. MRI Compatibility of Robot Actuation Techniques – A Comparative Study

    Fischer, Gregory S.; Krieger, Axel; Iordachita, Iulian; Csoma, Csaba; Whitcomb, Louis L.; Fichtinger, Gabor

    2010-01-01

    This paper reports an experimental evaluation of the following three different MRI-compatible actuators: a Shinsei ultrasonic motor, a Nanomotion ultrasonic motor and a pneumatic cylinder actuator. We report the results of a study comparing the effect of these actuators on the signal to noise ratio (SNR) of MRI images under a variety of experimental conditions. Evaluation was performed with the controller inside and outside the scanner room and with both 1.5T and 3T MRI scanners. Pneumatic cylinders function with no loss of SNR with controller both inside and outside of the scanner room. The Nanomotion motor performs with moderate loss of SNR when moving during imaging. The Shinsei is unsuitable for motion during imaging. All may be used when motion is appropriately interleaved with imaging cycles. PMID:18982643

  19. Physical acoustics at UCLA in the study of superfluid helium

    Rudnick, I.

    1976-01-01

    The theory of sound propagation in superfluid helium is reviewed. The theory of first, second, fourth and third sound is considered. A simple approximate derivation of the velocity of third sound is given and the Doppler shift of first, second, third and fourth sound is discussed. Experimental aspects of first, second, third and fourth sound are considered in turn. For first sound consideration is given to first-sound transducers, cavitation in liquid helium and velocity at the lambda transition. Second-sound transducers and the velocity of second sound at the lambda transition are discussed. Experimental aspects of third-sound transducers, the velocity and attenuation of third sound, the critical velocity of superfluid films and the thickness of a moving film are then discussed. Various aspects of fourth sound are considered. (B.R.H.)

  20. Skin compatibility and antimicrobial studies on biofunctionalized polypropylene fabric

    Anjum, Sadiya [Bioengineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi 110016 (India); Gupta, Amlan; Sharma, Deepika [Department of Pathology, Sikkim Manipal Institute of Medical Sciences, Sikkim Manipal University, Gangtok 737102 (India); Dalal, Prashansa [Bioengineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi 110016 (India); Gupta, Bhuvanesh, E-mail: bgupta@textile.iitd.ernet.in [Bioengineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi 110016 (India)

    2016-12-01

    The aim of this study was the development of antimicrobial fabric which can be used as skin contacting material. The nanosilver loaded bioactive nanogels of polyacrylamide were prepared by gamma irradiation process and the particle size was observed to be in the range of 10–50 nm. In this study, we used polyethylene glycol as carrier for the combination of functional nanogel and essential oils together. Plasma functionalized polypropylene fabric was used as the base material for the bio-immobilization. Bioactive emulsion was coated on the fabric which exhibited excellent antimicrobial activity against Staphylococcus aureus and Escherichia coli. Skin irritation studies were carried out over a period of 3 d on Swiss albino mice. Histopathology studies of the fabric did not show adverse inflammatory response in contact with the skin. The biofunctionalized fabric offers appear to be promising material for skin contacting applications. - Highlights: • Antimicrobial processing of PP fabric for skin contacting material • Polyethylene glycol is used for the carrier of bioactive nanogels. • Synergistic effect of functional nanosilver and essential oil has been investigated. • Skin compatibility and histopathological studies of material have been observed.

  1. Corrosion Compatibility Studies on Inconel-600 in NP Decontamination Solution

    Park, Sang Yoon; Jung, Jun Young; Won, Huijun; Choi, Wangkyu; Moon, Jeikwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    It is well known that corrosion and contamination process in the primary cooling circuit of nuclear reactors are essentially interrelated: the contaminant isotopes are mostly corrosion products activated in the reactor core, and the contamination takes place on the out-core of Inconel-600 surface. This radionuclide uptake takes place up to the inner oxide layer and oxide/metal interface. So, it is necessary to remove inner oxide layer as well as outer oxide layer for excellent decontamination effects. The outer oxide layers are composed of Fe{sub 3}O{sub 4} and NiFe{sub 2}O{sub 4}. On the other hand, the inner oxide layers are composed of Cr{sub 2}O{sub 3}, (Ni{sub 1-x}Ni{sub x})(Cr{sub 1-y}Fe{sub y}){sub 2}O{sub 4}, and FeCr{sub 2}O{sub 4}. Because of chromium in the trivalent oxidation state which is difficult to dissolve, the oxide layer has an excellent protectiveness and become hard to be decontaminated. Alkaline permanganate (AP) or nitric permanganate (NP) oxidative phase has been used to dissolve the chromium-rich oxide. A disadvantage of AP process is the generation of a large volume of secondary waste. On the other hand, that of NP process is the high corrosion rate for Ni-base alloys. Therefore, for the safe use of oxidative phase in PWR system decontamination, it is necessary to reformulate the NP chemicals for decrease of corrosion rate. This study describes the corrosion compatibility on Inconel-600 and type 304 stainless steel in NP decontamination solution for PWR applications. To evaluate the general corrosion properties, weight change of NP treated specimens was measured. NP treated specimen surface was observed using optical microscope (OM) and scanning electron microscopy (SEM) for the evaluation of the localized corrosion. The effect of additives on the corrosion of the specimens was also evaluated. This study describes the corrosion compatibility on Inconel-600 and type 304 stainless steel in NP decontamination solution for PWR applications

  2. Corrosion Compatibility Studies on Inconel-600 in NP Decontamination Solution

    Park, Sang Yoon; Jung, Jun Young; Won, Huijun; Choi, Wangkyu; Moon, Jeikwon

    2013-01-01

    It is well known that corrosion and contamination process in the primary cooling circuit of nuclear reactors are essentially interrelated: the contaminant isotopes are mostly corrosion products activated in the reactor core, and the contamination takes place on the out-core of Inconel-600 surface. This radionuclide uptake takes place up to the inner oxide layer and oxide/metal interface. So, it is necessary to remove inner oxide layer as well as outer oxide layer for excellent decontamination effects. The outer oxide layers are composed of Fe 3 O 4 and NiFe 2 O 4 . On the other hand, the inner oxide layers are composed of Cr 2 O 3 , (Ni 1-x Ni x )(Cr 1-y Fe y ) 2 O 4 , and FeCr 2 O 4 . Because of chromium in the trivalent oxidation state which is difficult to dissolve, the oxide layer has an excellent protectiveness and become hard to be decontaminated. Alkaline permanganate (AP) or nitric permanganate (NP) oxidative phase has been used to dissolve the chromium-rich oxide. A disadvantage of AP process is the generation of a large volume of secondary waste. On the other hand, that of NP process is the high corrosion rate for Ni-base alloys. Therefore, for the safe use of oxidative phase in PWR system decontamination, it is necessary to reformulate the NP chemicals for decrease of corrosion rate. This study describes the corrosion compatibility on Inconel-600 and type 304 stainless steel in NP decontamination solution for PWR applications. To evaluate the general corrosion properties, weight change of NP treated specimens was measured. NP treated specimen surface was observed using optical microscope (OM) and scanning electron microscopy (SEM) for the evaluation of the localized corrosion. The effect of additives on the corrosion of the specimens was also evaluated. This study describes the corrosion compatibility on Inconel-600 and type 304 stainless steel in NP decontamination solution for PWR applications. It is revealed that Inconel-600 specimen is more

  3. The helium effect at grain boundaries in Fe-Cr alloys: A first-principles study

    Zemła, M.R., E-mail: marcin.zemla@wimpw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Wróbel, J.S.; Wejrzanowski, T. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Nguyen-Manh, D. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Kurzydłowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland)

    2017-02-15

    Helium is produced in the structural materials in nuclear power plants by nuclear transmutation following neutron irradiation. Since the solubility of helium in all metals is extremely low, helium tends to be trapped at defects such as vacancies, dislocations and grain boundaries, which cause material embrittlement. Density functional theory (DFT) calculations were performed in order to investigate the helium effect at grain boundaries (GBs) in iron-chromium alloys. Both cohesive energy and magnetic properties at symmetric Σ3(1 1 1) and Σ5(2 1 0) tilt Fe GBs are studied in the presence of Cr and He atoms. It is found that the presence of Cr atoms increases cohesive energy, at different He concentrations, and strongly influences magnetic properties at the GBs. The effect of the segregation energy of helium atom as a function of the different positions of Cr atoms located inside/outside a GB has been considered. Results of the present first-principles study enable one to clarify the role of Cr in understanding the helium effect in Fe-Cr-based alloys.

  4. Plutonium-238 dioxide/T-111 compatibility studies

    Jones, G.J.; Selle, J.E.; Teaney, P.E.

    1975-01-01

    The tantalum-base alloy, T-111, is an ideal radioisotope encapsulant from the aspect of mechanical properties, but unfortunately undergoes severe oxygen embrittlement during long-term, high-temperature exposure to PuO 2 . A study was undertaken in an effort to improve T-111/PuO 2 compatibility by testing the hypothesis that reduction of fuel stoichiometry to the range PuO 1 . 75 to PuO 1 . 8 would suspend the embrittlement process by producing a state of thermodynamic equilibrium within the capsule. Test temperatures ranged from 773 to 1373 0 K, with aging times of 60 days, 240 days, and 2 y. The desired reaction did not proceed rapidly enough at the aging temperatures to stop T-111 embrittlement. Capsules heated above 1573 0 K for 1 hr showed no signs of embrittlement during aging, even after 2 y at temperatures as high as 1173 0 K. Results with test specimens employing pelletized fuel indicated the solid-state diffusion of oxygen from the fuel to the T-111 was the dominating transport process. In nonpretreated capsules oxygen diffusion in T-111 was the rate-controlling process. Pretreatment does result in the desired thermodynamic equilibrium at temperatures up to at least 1173 0 K. (auth)

  5. Materials compatibility studies for the Spallation Neutron Source

    DiStefano, J.R.; Pawel, S.J.; Manneschmidt, E.T.

    1998-01-01

    The Spallation Neutron Source (SNS) is a high power facility for producing neutrons that utilizes flowing liquid mercury inside an austenitic stainless steel container as the target for a 1.0 GeV proton beam. Type 316 SS has been selected as the container material for the mercury and consequences of exposure of 316 SS to radiation, thermal shock, thermal stress, cavitation and hot, flowing mercury are all being addressed by R and D programs. In addition, corrosion studies also include evaluation of Inconel 718 because it has been successfully used in previous spallation neutron systems as a window material. Two types of compatibility issues relative to 316 SS/mercury and Inconel 718/mercury are being examined: (1) liquid metal embrittlement (LME) and (2) temperature gradient mass transfer. Studies have shown that mercury does not easily wet type 316 SS below 275 C. In the LME experiments, attempts were made to promote wetting of the steel by mercury either by adding gallium to the mercury or coating the specimen with a tin-silver solder that the mercury easily wets. The latter proved more reliable in establishing wetting, but there was no evidence of LME in any of the constant extension rate tensile tests either at 23 or 100 C. Inconel 718 also showed no change in room temperature properties when tested in mercury or mercury-gallium. However, there was evidence that the fracture was less ductile. Preliminary evaluation of mass transfer of either type 316 SS or Inconel 718 in mercury or mercury-gallium at 350 C (maximum temperature) did not reveal significant effects. Two 5,000 h thermal convection loop tests of type 316 SS are in progress, with specimens in both hot and cold test regions, at 300 and 240 C, respectively

  6. Spectroscopic Study of Recombination in the Early Afterglow of a Helium Plasma

    Stevefelt, J

    1968-02-15

    Some properties of a decaying helium plasma have been studied using time resolved spectroscopy and probe diagnostics. The plasma was produced in a pulsed, repetitive, hot cathode discharge in helium at a pressure 11 torr , and the light emitted in the afterglow of the discharge was measured by means of a spectrometer-photomultiplier combination. Single photoelectrons were counted on a scaler during a preset gate time of each discharge cycle, and after a preset number of cycles recorded on punched tape. The spectrometer was calibrated for absolute intensity measurements of the spectral lines of atomic helium. The overall conductance of the positive column was determined by measuring the voltage difference between two probes inserted into the plasma, passing a very small current pulse between the anode and cathode in the afterglow. Heavier current pulses were used to heat the free electrons selectively, thus providing so-called 'afterglow quenching'. From the measured absolute intensities of the helium lines, the number densities of the excited states of helium were calculated. All levels with principal quantum number n {>=} 8 were found to be in near Saha equilibrium with the free electrons at a temperature 1,275 deg K in the early afterglow (15-35 {mu}s after end of the discharge). By measuring the absolute intensities of some of the molecular helium bands, an estimate of the rate of conversion of atomic helium ions into molecular helium ions was obtained. The atomic line radiation, as well as the molecular band radiation, was assumed to result from collisional-radiative recombination of atomic and molecular helium ions, respectively. The rate of recombination down to the metastable level n = 2 was obtained from the measured line intensities. By adding the rate of ambipolar diffusion, calculated from known literature data, quite good agreement with the measured decay rate for the electron density was found. The measured line intensities were also used to calculate

  7. Role of expanders in helium liquefaction cycles: Parametric studies using Collins cycle

    Thomas, Rijo Jacob; Ghosh, Parthasarathi; Chowdhury, Kanchan

    2011-01-01

    Large scale helium liquefaction/refrigeration plant is a key subsystem of fusion devices. Performance of these plants is dependent on a number of geometric and operating parameters of its constituting components such as compressors, heat exchangers, expanders, valves, etc. Expander has been chosen as the subject matter of analyses in the present study. As the sensible cold of helium vapor is lost in liquefiers, the expanders in liquefaction cycles have to provide more refrigeration than those in refrigeration cycles. The expander parameters such as rate of mass flow, operating pressure, inlet temperature, etc. are inter-dependent, and hence, it is difficult to predict the system behavior with variation of a particular parameter. This necessitates the use of process simulators. Parametric studies have been performed on Collins helium liquefaction cycle using Aspen HYSYS. Collins cycle has all the basic characteristics of a large-scale helium liquefier and the results of this study may be extrapolated to understand the behavior of large scale helium liquefiers. The study shows that the maximum liquid production is obtained when 80% of the compressor flow is diverted through the expanders and it is equally distributed between the two expanders. The relationships between the liquid production and the isentropic efficiency of expanders are almost linear and both the higher and lower temperature expanders exhibit similar trends.

  8. Role of expanders in helium liquefaction cycles: Parametric studies using Collins cycle

    Thomas, Rijo Jacob, E-mail: rijojthomas@gmail.com [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India); Ghosh, Parthasarathi; Chowdhury, Kanchan [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India)

    2011-06-15

    Large scale helium liquefaction/refrigeration plant is a key subsystem of fusion devices. Performance of these plants is dependent on a number of geometric and operating parameters of its constituting components such as compressors, heat exchangers, expanders, valves, etc. Expander has been chosen as the subject matter of analyses in the present study. As the sensible cold of helium vapor is lost in liquefiers, the expanders in liquefaction cycles have to provide more refrigeration than those in refrigeration cycles. The expander parameters such as rate of mass flow, operating pressure, inlet temperature, etc. are inter-dependent, and hence, it is difficult to predict the system behavior with variation of a particular parameter. This necessitates the use of process simulators. Parametric studies have been performed on Collins helium liquefaction cycle using Aspen HYSYS. Collins cycle has all the basic characteristics of a large-scale helium liquefier and the results of this study may be extrapolated to understand the behavior of large scale helium liquefiers. The study shows that the maximum liquid production is obtained when 80% of the compressor flow is diverted through the expanders and it is equally distributed between the two expanders. The relationships between the liquid production and the isentropic efficiency of expanders are almost linear and both the higher and lower temperature expanders exhibit similar trends.

  9. Preliminary results of the Spacelab 2 superfluid helium experiment

    Mason, P.V.; Collins, D.J.; Elleman, D.D.; Jackson, H.W.; Wang, T.

    1986-01-01

    An experiment to investigate the properties of superfluid helium in a microgravity environment flew on the Shuttle on the Spacelab 2 mission in July and August of 1985. This paper summarizes the flight experiment and describes some preliminary results. The experiment comprised an investigation of long-wavelength third-sound waves in micron-thick films, a study of the motions of superfluid helium under milli-g and micro-g accelerations, and measurements of the fluctuations in temperature associated with the small motions of the bulk helium. An additional objective was to qualify and characterize a reflyable, space-compatible cryostat

  10. Study of reverse Brayton cryocooler with Helium-Neon mixture for HTS cable

    Dhillon, A. K.; Ghosh, P.

    2017-12-01

    As observed in the earlier studies, helium is more efficient than neon as a refrigerant in a reverse Brayton cryocooler (RBC) from the thermodynamic point of view. However, the lower molecular weight of helium leads to higher refrigerant inventory as compared to neon. Thus, helium is suitable to realize the high thermodynamic efficiency of RBC whereas neon is appropriate for the compactness of the RBC. A binary mixture of helium and neon can be used to achieve high thermodynamic efficiency in the compact reverse Brayton cycle (RBC) based cryocooler. In this paper, an attempt has been made to analyze the thermodynamic performance of the RBC with a binary mixture of helium and neon as the working fluid to provide 1 kW cooling load for high temperature superconductor (HTS) power cables working with a temperature range of 50 K to 70 K. The basic RBC is simulated using Aspen HYSYS V8.6®, a commercial process simulator. Sizing of each component based on the optimized process parameters for each refrigerant is performed based on a computer code developed using Engineering Equation Solver (EES-V9.1). The recommendation is provided for the optimum mixture composition of the refrigerant based on the trade-off factors like thermodynamic efficiency such as the exergy efficiency and equipment considerations. The outcome of this study may be useful for recommending a suitable refrigerant for the RBC operating at a temperature level of 50 K to 70 K.

  11. Characterization of materials for waste-canister compatibility studies

    McCoy, H.E.; Mack, J.E.

    1981-10-01

    Sample materials of 7 waste forms and 15 potential canister materials were procured for compatibility tests. These materials were characterized before being placed in test, and the results are the main topic of this report. A test capsule was designed for the tests in which disks of a single waste form were contacted with duplicate samples of canister materials. The capsules are undergoing short-term tests at 800 0 C and long-term tests at 100 and 300 0 C

  12. Analogies in the microscopic behavior of superfluid and classical helium studied by neturon scattering [Analogieen in het microscopische gedrag van superfluid en klassiek helium

    Crevecoeur, R.M.

    1996-01-01

    In this thesis we have presented the results of a neutron scattering study of the analogies in the microscopic behavior of superfluid and classical helium. Therefore we performed both neutron-diffraction experiments to study the structure and inelastic neutron scattering experiments to study the

  13. Helium behaviour in UO{sub 2} through low fluence ion implantation studies

    Garcia, P., E-mail: philippe.garcia@cea.fr [CEA – DEN/DEC, Bât. 352, 13108 Saint-Paul-Lez-Durance Cedex (France); Gilabert, E. [Centre d’Et' udes Nucleáires de Bordeaux-Gradignan, Le Haut Vigneau, 33175 Gradignan (France); Martin, G.; Carlot, G.; Sabathier, C. [CEA – DEN/DEC, Bât. 352, 13108 Saint-Paul-Lez-Durance Cedex (France); Sauvage, T.; Desgardin, P.; Barthe, M.-F. [CNRS-CEMHTI, UPR3079, 45071 Orleáns (France)

    2014-05-01

    In this work we focus on experiments involving implantation of 500 keV {sup 3}He ions in sintered polycrystalline material. Samples are implanted at low fluences (∼2 ×10{sup 13} ions/cm{sup 2}) and subsequently isothermally annealed in a highly sensitive thermal desorption spectrometry (TDS) device PIAGARA (Plateforme Interdisciplinaire pour l’Analyse des GAz Rares en Aquitaine). The helium fluencies studied are two to three orders of magnitude lower than previous Nuclear Reaction Analysis (NRA) experiments carried out on identical samples implanted at identical energies. The fractional release of helium obtained in the TDS experiments is interpreted using a three-dimensional axisymmetric diffusion model which enables results to be quantitatively compared to previous NRA data. The analysis shows that helium behaviour is qualitatively independent of ion fluency over three orders of magnitude: helium diffusion appears to be strongly inhibited below 1273 K within the centre of the grains presumably as a result of helium bubble precipitation. The scenario involving diffusion at grain boundaries and in regions adjacent to them observed at higher fluencies is quantitatively confirmed at much lower doses. The main difference lies in the average width of the region in which uninhibited diffusion occurs.

  14. Mobility of hydrogen-helium clusters in tungsten studied by molecular dynamics

    Grigorev, Petr, E-mail: grigorievpit@gmail.com [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol, 2400 (Belgium); Ghent University, Applied Physics EA17 FUSION-DC, St.Pietersnieuwstraat, 41 B4, B-9000, Gent (Belgium); Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnologies, and Telecommunications, Peter the Great St.Petersburg Polytechnic University, St. Petersburg (Russian Federation); Terentyev, Dmitry; Bonny, Giovanni [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol, 2400 (Belgium); Zhurkin, Evgeny E. [Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnologies, and Telecommunications, Peter the Great St.Petersburg Polytechnic University, St. Petersburg (Russian Federation); Oost, Guido van [Ghent University, Applied Physics EA17 FUSION-DC, St.Pietersnieuwstraat, 41 B4, B-9000, Gent (Belgium); Noterdaeme, Jean-Marie [Ghent University, Applied Physics EA17 FUSION-DC, St.Pietersnieuwstraat, 41 B4, B-9000, Gent (Belgium); Max-Planck-Institut für Plasmaphysik, Garching (Germany)

    2016-06-15

    Tungsten is a primary candidate material for plasma facing components in fusion reactors. Interaction of plasma components with the material is unavoidable and will lead to degradation of the performance and the lifetime of the in-vessel components. In order to gain better understanding the mechanisms driving the material degradation at atomic level, atomistic simulations are employed. In this work we study migration, stability and self-trapping properties of pure helium and mixed helium-hydrogen clusters in tungsten by means of molecular dynamics simulations. We test two versions of an embedded atom model interatomic potential by comparing it with ab initio data regarding the binding properties of He clusters. By analysing the trajectories of the clusters during molecular dynamics simulations at finite temperatures we obtain the diffusion parameters. The results show that the diffusivity of mixed clusters is significantly lower, than that of pure helium clusters. The latter suggest that the formation of mixed clusters during mixed hydrogen helium plasma exposure will affect the helium diffusivity in the material.

  15. Neutronics study on hybrid reactor cooled by helium, water and molten salt

    Li Zaixin; Feng Kaiming; Zhang Guoshu; Zheng Guoyao; Zhao Fengchao

    2009-01-01

    There is no serious magnetohydrodynamics (MHD) problem when helium,water or molten salt of Flibe flows in high magnetic field. Thus helium, water and Flibe were proposed as candidate of coolant for fusion-fission hybrid reactor based on magnetic confinement. The effect on neutronics of hybrid reactor due to coolant was investigated. The analyses of neutron spectra and fuel breeding of blanket with different coolants were performed. Variations of tritium breeding ratio (TBR), blanket energy multiplication (M) and keff with operating time were also studied. MCNP code was used for neutron transport simulation. It is shown that spectra change greatly with different coolants. The blanket with helium exhibits very hard spectrum and good tritium breeding ability. And fission reactions are mainly from fast neutron. The blanket with water has soft spectrum and high energy multiplication factor. However, it needs to improve TBR. The blanket with Flibe has hard spectrum and less energy release. (authors)

  16. Study of the electromagnetic form factors of Helium-3 and Tritium nuclei by electron scattering

    Amroun, A.

    1989-01-01

    Accurate measurements of the tritium electromagnetic form factor demonstrated that, when the exchange currents are included, the theoretical and the experimental data are in agreement. Similar calculations carried out on helium-3 were not satisfactory. In this investigation, a new electromagnetic form factor of helium-3 is measured. The transfer zone of the diffraction spectra concerning the first minimum and the second maximum is considered. The aim of the study is to test on both nuclei the validity and the uncertainties of the models. The scattering of electrons on helium-3 is analyzed. The experiment was performed in the Saclay linear accelerator. The isoscalar and isovector form factors could be differentiated. By comparing the theoretical and the experimental data, it is demonstrated that the use of three body forces in the calculations has no effect on the form factor results [fr

  17. Radiation damage studies of detector-compatible Si JFETs

    Dalla Betta, Gian-Franco; Boscardin, Maurizio; Candelori, Andrea; Pancheri, Lucio; Piemonte, Claudio; Ratti, Lodovico; Zorzi, Nicola

    2007-01-01

    We have largely improved the performance of our detector-compatible Si JFETs by optimizing the fabrication technology. New devices feature thermal noise values close to the theoretical ones, and remarkably low 1/f noise figures. In view of adopting these JFETs for X-ray imaging and HEP applications, bulk and surface radiation damage tests have been carried out by irradiating single transistors and test structures with neutrons and X-rays. Selected results from static and noise characterization of irradiated devices are discussed in this paper, and the impact of radiation effects on the performance of JFET-based circuits is addressed

  18. Hydration of magnesia cubes: a helium ion microscopy study

    Ruth Schwaiger

    2016-02-01

    Full Text Available Physisorbed water originating from exposure to the ambient can have a strong impact on the structure and chemistry of oxide nanomaterials. The effect can be particularly pronounced when these oxides are in physical contact with a solid substrate such as the ones used for immobilization to perform electron or ion microscopy imaging. We used helium ion microscopy (HIM and investigated morphological changes of vapor-phase-grown MgO cubes after vacuum annealing and pressing into foils of soft and high purity indium. The indium foils were either used as obtained or, for reference, subjected to vacuum drying. After four days of storage in the vacuum chamber of the microscope and at a base pressure of p −7 mbar, we observed on these cubic particles the attack of residual physisorbed water molecules from the indium substrate. As a result, thin magnesium hydroxide layers spontaneously grew, giving rise to characteristic volume expansion effects, which depended on the size of the particles. Rounding of the originally sharp cube edges leads to a significant loss of the morphological definition specific to the MgO cubes. Comparison of different regions within one sample before and after exposure to liquid water reveals different transformation processes, such as the formation of Mg(OH2 shells that act as diffusion barriers for MgO dissolution or the evolution of brucite nanosheets organized in characteristic flower-like microstructures. The findings underline the significant metastability of nanomaterials under both ambient and high-vacuum conditions and show the dramatic effect of ubiquitous water films during storage and characterization of oxide nanomaterials.

  19. The study on compatibility of polymer matrix resins with liquid oxygen

    Wang Ge; Li Xiaodong; Yan Rui; Xing Suli

    2006-01-01

    Liquid oxygen (LOX) polymer composite tank is very important in the development of next generation of launch vehicles. To study LOX compatible polymeric matrix resins, three kinds of epoxy resins were studied. LOX impact test was used to evaluate polymers' compatibility with LOX. Thermogravimetric analysis was used to analyze polymers' oxidation. It seemed that polymers with better anti-oxidation properties, characterized by lower oxidation weight gain, lower weight loss and lower flash point, behaved better LOX compatibility. Fourier transform infrared attenuated total reflection spectroscopy confirmed the chemical reactions during the LOX impact process on the surface of polymers were similar to the oxidation reaction in gaseous oxygen (GOX) at high temperatures, which indicated the chemical mechanism of LOX compatibility of polymers was just oxidation reaction. In this way, two new epoxy resins with desirable LOX compatibility were acquired by modification

  20. On depth profiling of hydrogen and helium isotopes and its application to ion-implantation studies

    Boettiger, J.

    1979-01-01

    The thesis is divided into two parts, the first being a general review of the experimental methods for depth profiling of light isotopes, where ion beams are used. In the second part, studies of ion implantation of hydrogen and helium isotopes, applying the techniques discussed in the first part, are described. The paper summarizes recent experimental results and discusses recent developments. (Auth.)

  1. Particle and energy transport studies on TFTR and implications for helium ash in future fusion devices

    Synakowski, E.J.; Efthimion, P.C.; Rewoldt, G.; Stratton, B.C.; Tang, W.M.; Bell, R.E.; Grek, B.; Hulse, R.A.; Johnson, D.W.; Hill, K.W.; Mansfield, D.K.; McCune, D.; Mikkelsen, D.R.; Park, H.K.; Ramsey, A.T.; Scott, S.D.; Taylor, G.; Timberlake, J.; Zarnstorff, M.C.

    1992-01-01

    Particle and energy transport in tokamak plasmas have long been subjects of vigorous investigation. Present-day measurement techniques permit radially resolved studies of the transport of electron perturbations, low- and high-Z impurities, and energy. In addition, developments in transport theory provide tools that can be brought to bear on transport issues. Here, we examine local particle transport measurements of electrons, fully-stripped thermal helium, and helium-like iron in balanced-injection L-mode and enhanced confinement deuterium plasmas on TFTR of the same plasma current, toroidal field, and auxiliary heating power. He 2+ and Fe 24+ transport has been studied with charge exchange recombination spectroscopy, while electron transport has been studied by analyzing the perturbed electron flux following the same helium puff used for the He 2+ studies. By examining the electron and He 2+ responses following the same gas puff in the same plasmas, an unambiguous comparison of the transport of the two species has been made. The local energy transport has been examined with power balance analysis, allowing for comparisons to the local thermal fluxes. Some particle and energy transport results from the Supershot have been compared to a transport model based on a quasilinear picture of electrostatic toroidal drift-type microinstabilities. Finally, implications for future fusion reactors of the observed correlation between thermal transport and helium particle transport is discussed

  2. Helium diffraction study of pentacene films on Au(1 1 1)

    Albayrak, E. [Department of Materials and Metallurgical Engineering, Ahi Evran University, Kırşehir 40000 (Turkey); Danışman, M.F., E-mail: danisman@metu.edu.tr [Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)

    2014-03-01

    Highlights: • Pentacene films were grown by supersonic molecular beam deposition on Au(1 1 1). • Simultaneous helium scattering and quartz crystal resonance frequency shift measurements were performed. • Helium diffraction results were consistent with a (6 × 3) monolayer structure. • No ordered multilayers could be observed. - Abstract: Here we present a helium atom diffraction study of pentacene films on Au(1 1 1) surface prepared by supersonic molecular beam deposition. Though investigated parameter space was limited no significant difference between the films prepared by different deposition energies was observed. Completion of monolayer coverage was confirmed by simultaneous helium scattering and quartz crystal resonance frequency shift measurements during pentacene film growth on the gold electrode of a quartz resonator. Monolayer films were found to adopt a (6 × 3) unit cell which was also observed for pentacene monolayers on Ag(1 1 1). However no ordered multilayer film structure could be observed which is in contrast with the previous Ag(1 1 1) studies.

  3. Numerical Study on the Helium Flow Characteristics for Steam Generator Subsystem of HTR

    Ha, Jung Hoon; Ham, Jin Ki; Ki, Min-Hwan; Lee, Won Jae

    2014-01-01

    The High Temperature Reactor (HTR), one of the 4th generation reactors, utilizes helium as the primary coolant. A Steam Generator Subsystem (SGS) is installed to transfer heat from the primary coolant to feed water and subsequently produce steam so that it supplies electricity as well as process heat over a wide range. The SGS is composed of a helical heat exchanger, shrouds directing the flow of the shell side helium and support systems, which are located within the steam generator vessel. In this study, helium flow characteristics in the SGS were investigated at various operating conditions using Computational Fluid Dynamics (CFD). A full-scale 3-D model of the SGS was developed and the reynolds stress model with standard wall treatment was used as a turbulence model. The CFD result was compared to that of the concept design of the steam cycle modular helium reactor for the design verification of the SGS. From the CFD analysis, it was found that the primary coolant flow had non-uniform distribution while it passed the inlet in the helical heat exchanger. In order to make the uniform primary coolant flow uniform, a special type of screen was suggested in front of the helical heat exchanger. As a result, the overall design adequacy of the SGS has been evaluated. (author)

  4. Study of damage and helium diffusion in fluoro-apatites; Etude de l'endommagement et de la diffusion de l'helium dans des fluoroapatites

    Miro, S

    2004-12-15

    This work lies within the scope of the study of the radionuclides containment matrices. The choice of the fluoro-apatites as potential matrices of containment was suggested by the notable properties of these latter (thermal and chemical stability even under radioactive radiation). By irradiations with heavy ions and a helium implantation we simulated the effects related to the alpha radioactivity and to the spontaneous nuclear fission of the radionuclides. Thanks to the study of Durango fluoro-apatite single crystals and fluoro-apatite sintered ceramics, we evidenced that the damage fraction as well as the unit cell deformations increase with the electronic energy loss and with the substitution. These effects are followed at high fluences by a phenomenon of re-crystallization. The study of the helium diffusion points out that the thermal diffusion process improves with the substitution and strongly increases with heavy ions irradiation. (author)

  5. Experimental studies on helium release and stratification within the AIHMS facility

    Prabhakar, Aneesh; Agrawal, Nilesh; Raghavan, V.; Das, Sarit K.

    2015-01-01

    Hydrogen is generated during core meltdown accidents in nuclear power plants. The study of hydrogen release and mixing within the containment is an important area of safety research. An experimental setup called the AERB-IIT Madras Hydrogen Mixing Studies (AIHMS) facility is setup at IIT Madras to study the distribution of helium (an inert surrogate to hydrogen) subsequent to release as a jet. The present paper gives details of the design, fabrication and instrumentation of the AIHMS facility. It then compares the features of the facility with respect to other facilities existing for hydrogen mitigation studies. Then it gives details of the experiments on concentration build-up studies as a result of injection of gases (air and helium) performed in this experimental facility. (author)

  6. Study of helium diffusion, implanted at a cyclotron, in face-centered cubic metals: Au, Ag and Al

    Sciani, V.

    1985-01-01

    Helium in metals is produced by nuclear reactions of energetic particles. In nuclear technology the interest on helium in metals is import, due to its production by (n, α) reaction. Because helium has extremely low solubility in metals, the precipitation in the form of filled bubbles at elevated temperatures occurs, which have detrimental effects on mechanical properties and may limit the lifetime of structural components. One typical example is the high temperature embrittlement. The nucleation and growth of the bubbles strongly depends on the mobility of the helium. This work presents the study of helium diffusion in Au, Ag and Al at temperatures above room temperature. The helium created by (n, α) reactions has been simulated by homogeneous alpha particles implantation in cyclotron, at room temperature, in specimens of thicknesses between 5 and 50 μm and helium concentration between 10 -3 to 10 ppm. After implantation, the specimens were dropped in a furnace in a UHV-chamber and the diffusion was measured by observing the He-release during linear and isothermal annealings. The occurence of free diffusion was comparing the dependence of release kinetics on helium concentration, sample thickness, time and heating rate to diffusion theory and is clearly separeted from agglomeration process. The diffusion constants of helium in Au, Ag and Al follow an Arrhenius behavior, with: Au:D o =10 -1.0 cm 2 /s ΔH=1.70eV Ag:D 0 =10 -1.2 cm 2 /s ΔH=1.51eV Al:D o =10 +0.5 cm 2 /s ΔH=1.40eV. The results are compared to self-diffusion and to the diffusion of other gases in these metals. Comparison with theoretical estimates favours the vacancy mechanism for helium diffusion in Au, Ag and Al. (author) [pt

  7. The effect of helium on ventilator performance: study of five ventilators and a bedside Pitot tube spirometer.

    Oppenheim-Eden, A; Cohen, Y; Weissman, C; Pizov, R

    2001-08-01

    To assess in vitro the performance of five mechanical ventilators-Siemens 300 and 900C (Siemens-Elma; Solna, Sweden), Puritan Bennett 7200 (Nellcor Puritan Bennett; Pleasanton, CA), Evita 4 (Dragerwerk; Lubeck, Germany), and Bear 1000 (Bear Medical Systems; Riverside CA)-and a bedside sidestream spirometer (Datex CS3 Respiratory Module; Datex-Ohmeda; Helsinki, Finland) during ventilation with helium-oxygen mixtures. In vitro study. ICUs of two university-affiliated hospitals. Each ventilator was connected to 100% helium through compressed air inlets and then tested at three to six different tidal volume (VT) settings using various helium-oxygen concentrations (fraction of inspired oxygen [FIO(2)] of 0.2 to 1.0). FIO(2) and VT were measured with the Datex CS3 spirometer, and VT was validated with a water-displacement spirometer. The Puritan Bennett 7200 ventilator did not function with helium. With the other four ventilators, delivered FIO(2) was lower than the set FIO(2). For the Siemens 300 and 900C ventilators, this difference could be explained by the lack of 21% oxygen when helium was connected to the air supply port, while for the other two ventilators, a nonlinear relation was found. The VT of the Siemens 300 ventilator was independent of helium concentration, while for the other three ventilators, delivered VT was greater than the set VT and was dependent on helium concentration. During ventilation with 80% helium and 20% oxygen, VT increased to 125% of set VT for the Siemens 900C ventilator, and more than doubled for the Evita 4 and Bear 1000 ventilators. Under the same conditions, the Datex CS3 spirometer underestimated the delivered VT by about 33%. At present, no mechanical ventilator is calibrated for use with helium. This investigation offers correction factors for four ventilators for ventilation with helium.

  8. Theoretical and experimental studies on transient forced convection heat transfer of helium gas

    Liu, Qiusheng; Fukuda, Katsuya; Shibahara, Makoto

    2008-01-01

    Forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a horizontal cylinder and a plate (ribbon) one was experimentally and theoretically studied. In the experimental studies, the authors measured heat flux, surface temperature, and transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder and a plate (ribbon) one under wide experimental conditions. Empirical correlations for quasi-steady-state heat transfer and transient heat transfer were obtained based on the experimental data. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. The values of numerical solution for surface temperature and heat flux were compared and discussed with authors' experimental data. (author)

  9. Helium crystals

    Lipson, S.G.

    1987-01-01

    Hexagonal close-packed helium crystals in equilibrium with superfluid have been found to be one of the few systems in which an anisotropic solid comes into true thermodynamic equilibrium with its melt. The discovery of roughening transitions at the liquid-solid interface have shown this system to be ideal for the study of the statistical mechanics of interface structures. We describe the effect of roughening on the shape and growth of macroscopic crystals from both the theoretical and experimental points of view. (author)

  10. Modeling and Simulation Optimization and Feasibility Studies for the Neutron Detection without Helium-3 Project

    Ely, James H.; Siciliano, Edward R.; Swinhoe, Martyn T.; Lintereur, Azaree T.

    2013-01-01

    This report details the results of the modeling and simulation work accomplished for the ‘Neutron Detection without Helium-3’ project during the 2011 and 2012 fiscal years. The primary focus of the project is to investigate commercially available technologies that might be used in safeguards applications in the relatively near term. Other technologies that are being developed may be more applicable in the future, but are outside the scope of this study.

  11. Fragmentation dynamics of ionized neon trimer inside helium nanodroplets: a theoretical study.

    Bonhommeau, David; Viel, Alexandra; Halberstadt, Nadine

    2004-06-22

    We report a theoretical study of the fragmentation dynamics of Ne(3) (+) inside helium nanodroplets, following vertical ionization of the neutral neon trimer. The motion of the neon atoms is treated classically, while transitions between the electronic states of the ionic cluster are treated quantum mechanically. A diatomics-in-molecules description of the potential energy surfaces is used, in a minimal basis set consisting of three effective p orbitals on each neon atom for the missing electron. The helium environment is modeled by a friction force acting on the neon atoms when their speed exceeds the Landau velocity. A reasonable range of values for the corresponding friction coefficient is obtained by comparison with existing experimental measurements. (c) 2004 American Institute of Physics.

  12. Study of Transient Heat Transport Mechanisms in Superfluid Helium Cooled Rutherford-Cables

    AUTHOR|(CDS)2100615

    The Large Hadron Collider leverages superconducting magnets to focus the particle beam or keep it in its circular track. These superconducting magnets are composed of NbTi-cables with a special insulation that allows superfluid helium to enter and cool the superconducting cable. Loss mechanisms, e.g. continuous random loss of particles escaping the collimation system heating up the magnets. Hence, a local temperature increase can occur and lead to a quench of the magnets when the superconductor warms up above the critical temperature. A detailed knowledge about the temperature increases in the superconducting cable (Rutherford type) ensures a secure operation of the LHC. A sample of the Rutherford cable has been instrumented with temperature sensors. Experiments with this sample have been performed within this study to investigate the cooling performance of the helium in the cable due to heat deposition. The experiment uses a superconducting coil, placed in a cryostat, to couple with the magnetic field loss m...

  13. Experimental study and technique for calculation of critical heat fluxes in helium boiling in tubes

    Arkhipov, V.V.; Kvasnyuk, S.V.; Deev, V.I.; Andreev, V.K.

    1979-01-01

    Studied is the effect of regime parameters on critical heat loads in helium boiling in a vertical tube in the range of mass rates of 80 2 xc) and pressures of 100<=p<=200 kPa for the vapor content range corresponding to the heat exchange crisis of the first kind. The method for calculating critical heat fluxes describing experimental data with the error less than +-15% is proposed. The critical heat loads in helium boiling in tubes reduce with the growth of pressure and vapor content in the regime parameter ranges under investigation. Both positive and negative effects of the mass rate on the critical heat flux are observed. The calculation method proposed satisfactorily describes the experimental data

  14. An extensive study of Bose-Einstein condensation in liquid helium using Tsallis statistics

    Guha, Atanu; Das, Prasanta Kumar

    2018-05-01

    Realistic scenario can be represented by general canonical ensemble way better than the ideal one, with proper parameter sets involved. We study the Bose-Einstein condensation phenomena of liquid helium within the framework of Tsallis statistics. With a comparatively high value of the deformation parameter q(∼ 1 . 4) , the theoretically calculated value of the critical temperature (Tc) of the phase transition of liquid helium is found to agree with the experimentally determined value (Tc = 2 . 17 K), although they differs from each other for q = 1 (undeformed scenario). This throws a light on the understanding of the phenomenon and connects temperature fluctuation(non-equilibrium conditions) with the interactions between atoms qualitatively. More interactions between atoms give rise to more non-equilibrium conditions which is as expected.

  15. Study on fundamental features of helium turbomachine for high temperature gas-cooled reactor

    Wang Jie; Gu Yihua

    2004-01-01

    The High temperature gas-cooled reactor (HTGR) coupled with helium turbine cycle is considered as one of the leading candidates for future nuclear power plants. The HTGR helium turbine cycle was analyzed and optimized. Then the focal point of investigation was concentrated on the fundamental thermodynamic and aerodynamic features of helium turbomachine. As a result, a helium turbomachine is different from a general combustion gas turbine in two main design features, that is a helium turbomachine has more blade stages and shorter blade length, which are caused by the helium property and the high pressure of a closed cycle, respectively. (authors)

  16. Role of heat exchangers in helium liquefaction cycles: Simulation studies using Collins cycle

    Thomas, Rijo Jacob, E-mail: rijojthomas@gmail.com [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur 721302 (India); Ghosh, Parthasarathi; Chowdhury, Kanchan [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur 721302 (India)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Role of heat exchangers in basic helium liquefier analyzed to design large-scale ones. Black-Right-Pointing-Pointer Heat exchangers that determine inlet temperature to expanders are more significant. Black-Right-Pointing-Pointer Limiting values of nondimensional UA for each heat exchanger have been determined. Black-Right-Pointing-Pointer Extra area distributed such that effectiveness of all heat exchangers increase uniformly. Black-Right-Pointing-Pointer Heat exchanger performance variation have little influence on the optimum expander flow. - Abstract: Energy efficiency of large-scale helium liquefiers generally employed in fusion reactors and accelerators is determined by the performance of their constituting components. Simulation with Aspen HYSYS{sup Registered-Sign} V7.0, a commercial process simulator, helps to understand the effects of heat exchanger parameters on the performance of a helium liquefier. Effective UA (product of overall heat transfer coefficient U, heat transfer surface area A and deterioration factor F) has been taken as an independent parameter, which takes into account all thermal irreversibilities and configuration effects. Nondimensionalization of parameters makes the results applicable to plants of any capacity. Rate of liquefaction is found to increase linearly with the effectiveness of heat exchangers. Performance of those heat exchangers that determine the inlet temperatures to expanders have more influence on the liquid production. Variation of sizes of heat exchangers does not affect the optimum rate of flow through expanders. Increasing UA improves the rate of liquid production; however, the improvement saturates at limiting UA. Maximum benefit in liquefaction is obtained when the available heat transfer surface area is distributed in such a way that the effectiveness remains equal for all heat exchangers. Conclusions from this study may be utilized in analyzing and designing large helium

  17. Role of heat exchangers in helium liquefaction cycles: Simulation studies using Collins cycle

    Thomas, Rijo Jacob; Ghosh, Parthasarathi; Chowdhury, Kanchan

    2012-01-01

    Highlights: ► Role of heat exchangers in basic helium liquefier analyzed to design large-scale ones. ► Heat exchangers that determine inlet temperature to expanders are more significant. ► Limiting values of nondimensional UA for each heat exchanger have been determined. ► Extra area distributed such that effectiveness of all heat exchangers increase uniformly. ► Heat exchanger performance variation have little influence on the optimum expander flow. - Abstract: Energy efficiency of large-scale helium liquefiers generally employed in fusion reactors and accelerators is determined by the performance of their constituting components. Simulation with Aspen HYSYS ® V7.0, a commercial process simulator, helps to understand the effects of heat exchanger parameters on the performance of a helium liquefier. Effective UA (product of overall heat transfer coefficient U, heat transfer surface area A and deterioration factor F) has been taken as an independent parameter, which takes into account all thermal irreversibilities and configuration effects. Nondimensionalization of parameters makes the results applicable to plants of any capacity. Rate of liquefaction is found to increase linearly with the effectiveness of heat exchangers. Performance of those heat exchangers that determine the inlet temperatures to expanders have more influence on the liquid production. Variation of sizes of heat exchangers does not affect the optimum rate of flow through expanders. Increasing UA improves the rate of liquid production; however, the improvement saturates at limiting UA. Maximum benefit in liquefaction is obtained when the available heat transfer surface area is distributed in such a way that the effectiveness remains equal for all heat exchangers. Conclusions from this study may be utilized in analyzing and designing large helium plants.

  18. Helium localisation in tritides

    Flament, J.L.; Lozes, G.

    1982-06-01

    Study of titanium and LaNi 5 type alloys tritides lattice parameters evolution revealed that helium created by tritium decay remains in interstitial sites up to a limit material dependant concentration. Beyond this one exceeding helium precipites in voids [fr

  19. Study on helium-charged titanium films deposited by DC-magnetron sputtering

    Shi Liqun; Jin Qinhua; Liu Chaozhuo; Xu Shilin; Zhou Zhuying

    2005-01-01

    Helium trapping in the Ti films deposited by DC magnetron sputtering with a He/Ar mixture was studied. He atoms with a surprisingly high concentration (He/Ti atomic ratio is as high as 56%) incorporate evenly in deposited film. The trapped amount of He can be controlled by the helium partial amount. The introduction of the helium with no extra damage (or very low damage) can be realized by choosing suitable deposition conditions. It was also found that because of the formation of nanophase Ti film a relative high He flux for bubble formation is needed and the amount of the retaining He in sputtering Ti films is much higher than that in the coarse-grain Ti films. The nanophase Ti film can accommodate larger concentration of trapped sites to He, which results in a high density and small size of the He bubbles. With increasing He irradiation flux, the grain size of Ti film decreases and the lattice spacing and width of the X-ray diffraction peak increase due to the He introduction, and the film tends to amorphous phase. (authors)

  20. Study and simulation of the behaviour under irradiation of helium in uranium dioxide; Etude et modelisation du comportement sous irradiation de l'helium dans le dioxyde d'uranium

    Martin, G

    2007-06-15

    Large quantities of helium are produced from {alpha}-decay of actinides in nuclear fuels during its in-pile operating and its storage. It is important to understand the behaviour of helium in these matrix in order to well simulate the evolution and the resistance of the fuel element. During this thesis, we have used nuclear reaction analyses (NRA) to follow the evolution of the helium implanted in polycrystalline and monocrystalline uranium dioxide (UO{sub 2}). An experimental rig was developed to follow the on-line helium release in UO{sub 2} and the evolution of {sup 3}He profiles as a function of annealing temperature. An automated procedure taking into account the evolution of the depth resolution was developed. Analyses performed with a nuclear microprobe allowed to characterise the spatial distribution of helium at the grain scale and to study the influence of the sample microstructure on the helium migration. This work put into evidence the particular role of grain boundaries and irradiation defects in the helium release process. The analyse of experimental results with a diffusion model corroborates these interpretations. It allowed to determine quantitatively physical properties that characterise the helium behaviour in uranium dioxide (diffusion coefficient, activation energy..). (author)

  1. MATERIALS COMPATIBILITY STUDY FOR THREE-DIMENSIONAL PRINTER MATERIALS

    2017-09-01

    shown that the nanoparticle vapor emitted by a 3D printer can present both environmental and health concerns. A study by the Built Environment...because of the different retention times and spectral features (Figures 10–13). In addition , azacyclotrodecan-2-one (62% confidence level for...to separate the PEG from the rest of the compounds to enhance the ionization. It is possible that in addition to applying a column, other types of

  2. Further study of helium production at large impact parameters in 6.4 TeV 32S emulsion reactions

    Kamel, S.

    1999-01-01

    Further study of helium production in electromagnetic and inelastic peripheral interactions of 32 S nuclei at 200 AGeV in nuclear emulsion is presented. The multiplicities, transverse momentum distributions of relativistic He fragments, and their parameters in both interactions are measured. The effect of the multiple helium production on the present obtained evidence of two different temperatures is investigated. The main characteristics of transverse momentum distributions show a certain dependence on the peripherality degree of the interactions

  3. Improving Satellite Compatible Microdevices to Study Biology in Space

    Kalkus, Trevor; Snyder, Jessica; Paulino-Lima, Ivan; Rothschild, Lynn

    2017-01-01

    sense for biochemicals. (3) Developing a modular, semi-autonomous microfluidic device that can be easily adapted for a variety of common biological experiments. This versatility will allow for quicker and cheaper experimentation. These improvements to satellite experiment platforms have the potential to radically increase the return from NASA's biological and field studies with reduced development time, mass, and cost with increased robustness data and interpretation.

  4. Helium implanted AlHf as studied by 181 Ta TDPAC

    Measurements on helium implanted sample indicate the binding of helium associated defects by Hf solute clusters. Isochronal annealing measurements indicate the dissociation of the helium implantation induced defects from Hf solute clusters for annealing treatments beyond 650 K. On comparison of the present results ...

  5. A study of the effect of helium concentration and displacement damage on the microstructure of helium ion irradiated tungsten

    Harrison, R. W.; Greaves, G.; Hinks, J. A.; Donnelly, S. E.

    2017-11-01

    Transmission electron microscopy (TEM) with in-situ He ion irradiation has been used to examine the damage microstructure of W when varying the helium concentration to displacement damage ratio, irradiation temperature and total dose. Irradiations employed 15, 60 or 85 keV He ions, at temperatures between 500 and 1000 °C up to doses of ∼3.0 DPA. Once nucleated and grown to an observable size in the TEM, bubble diameter as a function of irradiation dose did not measurably increase at irradiation temperatures of 500 °C between 1.0 and 3.0 DPA; this is attributed to the low mobility of vacancies and He/vacancy complexes at these temperatures. Bubble diameter increased slightly for irradiation temperatures of 750 °C and rapidly increased when irradiated at 1000 °C. Dislocation loops were observed at irradiation temperatures of 500 and 750 °C and no loops were observed at 1000 °C. Burgers vectors of the dislocations were determined to be b = ±½ type only and both vacancy and interstitial loops were observed. The proportion of interstitial loops increased with He-appm/DPA ratio and this is attributed to the concomitant increase in bubble areal density, which reduces the vacancy flux for both the growth of vacancy-type loops and the annihilation of interstitial clusters.

  6. Positron and nanoindentation study of helium implanted high chromium ODS steels

    Veternikova, Jana Simeg; Fides, Martin; Degmova, Jarmila; Sojak, Stanislav; Petriska, Martin; Slugen, Vladimir

    2017-12-01

    Three oxide dispersion strengthened (ODS) steels with different chromium content (MA 956, MA 957 and ODM 751) were studied as candidate materials for new nuclear reactors in term of their radiation stability. The radiation damage was experimentally simulated by helium ion implantation with energy of ions up to 500 keV. The study was focused on surface and sub-surface structural change due to the ion implantation observed by mostly non-destructive techniques: positron annihilation lifetime spectroscopy and nanoindentation. The applied techniques demonstrated the best radiation stability of the steel ODM 751. Blistering effect occurred due to high implantation dose (mostly in MA 956) was studied in details.

  7. Note: Commercial SQUID magnetometer-compatible NMR probe and its application for studying a quantum magnet.

    Vennemann, T; Jeong, M; Yoon, D; Magrez, A; Berger, H; Yang, L; Živković, I; Babkevich, P; Rønnow, H M

    2018-04-01

    We present a compact nuclear magnetic resonance (NMR) probe which is compatible with a magnet of a commercial superconducting quantum interference device magnetometer and demonstrate its application to the study of a quantum magnet. We employ trimmer chip capacitors to construct an NMR tank circuit for low temperature measurements. Using a magnetic insulator MoOPO 4 with S = 1/2 (Mo 5+ ) as an example, we show that the T-dependence of the circuit is weak enough to allow the ligand-ion NMR study of magnetic systems. Our 31 P NMR results are compatible with previous bulk susceptibility and neutron scattering experiments and furthermore reveal unconventional spin dynamics.

  8. Note: Commercial SQUID magnetometer-compatible NMR probe and its application for studying a quantum magnet

    Vennemann, T.; Jeong, M.; Yoon, D.; Magrez, A.; Berger, H.; Yang, L.; Živković, I.; Babkevich, P.; Rønnow, H. M.

    2018-04-01

    We present a compact nuclear magnetic resonance (NMR) probe which is compatible with a magnet of a commercial superconducting quantum interference device magnetometer and demonstrate its application to the study of a quantum magnet. We employ trimmer chip capacitors to construct an NMR tank circuit for low temperature measurements. Using a magnetic insulator MoOPO4 with S = 1/2 (Mo5+) as an example, we show that the T-dependence of the circuit is weak enough to allow the ligand-ion NMR study of magnetic systems. Our 31P NMR results are compatible with previous bulk susceptibility and neutron scattering experiments and furthermore reveal unconventional spin dynamics.

  9. Helium cryogenics

    Van Sciver, Steven W

    2012-01-01

    Twenty five years have elapsed since the original publication of Helium Cryogenics. During this time, a considerable amount of research and development involving helium fluids has been carried out culminating in several large-scale projects. Furthermore, the field has matured through these efforts so that there is now a broad engineering base to assist the development of future projects. Helium Cryogenics, 2nd edition brings these advances in helium cryogenics together in an updated form. As in the original edition, the author's approach is to survey the field of cryogenics with emphasis on helium fluids. This approach is more specialized and fundamental than that contained in other cryogenics books, which treat the associated range of cryogenic fluids. As a result, the level of treatment is more advanced and assumes a certain knowledge of fundamental engineering and physics principles, including some quantum mechanics. The goal throughout the work is to bridge the gap between the physics and engineering aspe...

  10. A social work study for the effects of different factors on compatible and discordant couples

    Mehdi Esalat

    2012-04-01

    Full Text Available In this paper, we perform an empirical investigation to examine the impact different factors on compatible and discordant couples. The survey is performed in one of western regions of Iran near the city of Esfahan. In our study, we choose two groups of people from the population with no family dispute and from the people who have requested divorce. They are asked to fill in a questionnaire and the results are analyzed. We used Chi-square tests to verify any meaningful difference between compatible and discordant couples on different issues. The survey concludes that compatible and discordant couples were different in their motivation, marital satisfaction, continued incentive generation, finding better position among relatives and accomplishing their religious duties to get married.

  11. Study on the compatibility of unbleached and bleached bamboo-fiber with LLDPE matrix

    Kumar, S

    2010-10-01

    Full Text Available analysis. The results suggested that BBF are more compatible with matrix than the unbleached ones. The X-ray diffraction pattern shows no change in the intensity peak position of matrix in the presence of bamboo fibers. Morphological studies were done...

  12. A first-principles and experimental study of helium diffusion in periclase MgO

    Song, Zhewen; Wu, Henry; Shu, Shipeng; Krawczynski, Mike; Van Orman, James; Cherniak, Daniele J.; Bruce Watson, E.; Mukhopadhyay, Sujoy; Morgan, Dane

    2018-02-01

    The distribution of He isotopes is used to trace heterogeneities in the Earth's mantle, and is particularly useful for constraining the length scale of heterogeneity due to the generally rapid diffusivity of helium. However, such an analysis is challenging because He diffusivities are largely unknown in lower mantle phases, which can influence the He profiles in regions that cycle through the lower mantle. With this motivation, we have used first-principles simulations based on density functional theory to study He diffusion in MgO, an important lower mantle phase. We first studied the case of interstitial helium diffusion in perfect MgO and found a migration barrier of 0.73 eV at zero pressure. Then we used the kinetic Monte Carlo method to study the case of substitutional He diffusion in MgO, where we assumed that He diffuses on the cation sublattice through cation vacancies. We also performed experiments on He diffusion at atmospheric pressure using ion implantation and nuclear reaction analysis in both as-received and Ga-doped samples. A comparison between the experimental and simulation results are shown. This work provides a foundation for further studies at high-pressure.

  13. Experimental study of the effects of helium-neon laser radiation on repair of injured tendon

    Xu, Yong-Qing; Li, Zhu-Yi; Weng, Long-Jiang; An, Mei; Li, Kai-Yun; Chen, Shao-Rong; Wang, Jian-Xin; Lu, Yu

    1993-03-01

    Despite extensive research into the biology of tendon healing, predictably restoring normal function to a digit after a flexor tendon laceration remains one of the most difficult problems facing the hand surgeon. The challenge of simultaneously achieving tendon healing while minimizing the peritendinous scar formation, which limits tendon gliding, has captured the attention of investigators for many years. It has been said that low-power density helium-neon laser radiation had effects on anti-inflammation, detumescence, progressive wound healing, and reducing intestinal adhesions. This experimental study aims at whether helium-neon laser can reduce injured tendon adhesions and improve functional recovery of the injured tendon. Fifty white Leghorn hens were used. Ten were randomly assigned as a normal control group, the other forty were used in the operation. After anesthetizing them with Amytal, a half of the profundus tendons of the second and third foretoes on both sides of the feet were cut. Postoperatively, the hens moved freely in the cages. One side of the toes operated on were randomly chosen as a treatment group, the other side served as an untreated control group. The injured tendon toes in the treatment group were irradiated for twenty minutes daily with a fiber light needle of helium-neon laser therapeutic apparatus (wavelength, 6328 angstroms) at a constant power density of 12.74 mW/cm2, the first exposure taking place 24 hours after the operation. The longest course of treatment was 3 weeks. The control group was not irradiated. At 3 days, 1, 2, 3, and 5 weeks after surgery, 8 hens were sacrificed and their tendons were examined. The experimental results: (1) active, passive flexion and tendon gliding functional recovery were significantly better in the treatment group (p < 0.01); (2) width and thickness of the tendon at the cut site were significantly smaller in the treatment group (p < 0.01); (3) degrees of tendon adhesions were significantly lighter

  14. Incentive Compatibility

    Ledyard, John O.

    1987-01-01

    Incentive compatibility is described and discussed. A summary of the current state of understanding is provided. Key words are: incentive compatibility, game theory, implementation, mechanism, Bayes, Nash, and revelation.

  15. First Study of Helium Gas Purification System as Primary Coolant of Co-Generation Reactor

    Piping Supriatna

    2009-01-01

    The technological progress of NPP Generation-I on 1950’s, Generation-II, Generation-III recently on going, and Generation-IV which will be implemented on next year 2025, concept of nuclear power technology implementation not only for generate electrical energy, but also for other application which called cogeneration reactor. Commonly the type of this reactor is High Temperature Reactor (HTR), which have other capabilities like Hydrogen production, desalination, Enhanced Oil Recovery (EOR), etc. The cogeneration reactor (HTR) produce thermal output higher than commonly Nuclear Power Plant, and need special Heat Exchanger with helium gas as coolant. In order to preserve heat transfer with high efficiency, constant purity of the gas must be maintained as well as possible, especially contamination from its impurities. In this report has been done study for design concept of HTR primary coolant gas purification system, including methodology by sampling He gas from Primary Coolant and purification by using Physical Helium Splitting Membrane. The examination has been designed in physical simulator by using heater as reactor core. The result of study show that the of Primary Coolant Gas Purification System is enable to be implemented on cogeneration reactor. (author)

  16. Contribution to the study of helium two-phase vertical flow

    Augyrond, L.

    1998-04-01

    This work aims at a better understanding of the dynamics of helium two-phase flow in a vertical duct. The case of bubble flow is particularly investigated. The most descriptive parameter of two-phase flow is the void fraction. A sensor to measure this parameter was specially designed and calibrated, it is made of a radioactive source and a semiconductor detector. Sensors based on light attenuation were used to study the behaviour of this two-phase flow. The experimental set-up is described. The different flow types were photographed and video filmed. This visualization has allowed to measure the diameter of bubbles and to study their movements in the fluid. Bubble flow then churn and annular flows were observed but slug flow seems not to exist with helium. A modelling based on a Zuber model matches better the experimental results than a Levy type model. The detailed analysis of the signals given by the optical sensors has allowed to highlight a bubble appearance frequency directly linked to the flowrate. (A.C.)

  17. Study of heat transfer in superconducting cable electrical insulation of accelerator magnet cooled by superfluid helium; Etude des transferts de chaleur dans les isolations electriques de cables supraconducteurs d'aimant d'accelerateur refroidi par helium superfluide

    Baudouy, B

    1996-10-04

    Heat transfer studies of electrical cable insulation in superconducting winding are of major importance for stability studies in superconducting magnets. This work presents an experimental heat transfer study in superconducting cables of Large Hadron Collider dipoles cooled by superfluid helium and submitted to volume heat dissipation due to beam losses. For NbTi magnets cooled by superfluid helium the most severe heat barrier comes from the electrical insulation of the cables. Heat behaviour of a winding is approached through an experimental model in which insulation characteristics can be modified. Different tests on insulation patterns show that heat transfer is influenced by superfluid helium contained in insulation even for small volume of helium (2 % of cable volume). Electrical insulation can be considered as a composite material made of a solid matrix with a helium channels network which cannot be modelled easily. This network is characterised by another experimental apparatus which allows to study transverse and steady-state heat transfer through an elementary insulation pattern. Measurements in Landau regime ({delta}T{approx}10{sup -5} to 10{sup -3} K) and in Gorter-Mellink regime ({delta}T>10{sup -3} K) and using assumptions that helium thermal paths and conduction in the insulation are decoupled allow to determine an equivalent channel area (10{sup -6} m{sup 2}) and an equivalent channel diameter (25 {mu}). (author)

  18. Study of heat transfer in superconducting cable electrical insulation of accelerator magnet cooled by superfluid helium; Etude des transferts de chaleur dans les isolations electriques de cables supraconducteurs d'aimant d'accelerateur refroidi par helium superfluide

    Baudouy, B

    1996-10-04

    Heat transfer studies of electrical cable insulation in superconducting winding are of major importance for stability studies in superconducting magnets. This work presents an experimental heat transfer study in superconducting cables of Large Hadron Collider dipoles cooled by superfluid helium and submitted to volume heat dissipation due to beam losses. For NbTi magnets cooled by superfluid helium the most severe heat barrier comes from the electrical insulation of the cables. Heat behaviour of a winding is approached through an experimental model in which insulation characteristics can be modified. Different tests on insulation patterns show that heat transfer is influenced by superfluid helium contained in insulation even for small volume of helium (2 % of cable volume). Electrical insulation can be considered as a composite material made of a solid matrix with a helium channels network which cannot be modelled easily. This network is characterised by another experimental apparatus which allows to study transverse and steady-state heat transfer through an elementary insulation pattern. Measurements in Landau regime ({delta}T{approx}10{sup -5} to 10{sup -3} K) and in Gorter-Mellink regime ({delta}T>10{sup -3} K) and using assumptions that helium thermal paths and conduction in the insulation are decoupled allow to determine an equivalent channel area (10{sup -6} m{sup 2}) and an equivalent channel diameter (25 {mu}). (author)

  19. Initial Studies of Low Temperature Ablation in a Helium Hypersonic Wind Tunnel. Draft

    Kohlman, D. L.; Elias, L.; Orlik-Ruckemann, K.

    1969-06-15

    A study of the feasibility of investigating the effects of ablation in a helium hypersonic wind tunnel was performed. Exploratory experiments were carried out at Mach 16.4 and at 600 psi stagnation pressure using (a) metal models at room temperature, (b) models with copper inserts, cooled to -140 deg C, and (c) models with carbon dioxide inserts. All models were flat plates at zero incidence, with a sharp leading edge in front of the insert. Surface temperature, surface recession rates and pitot pressure profiles were determined at several longitudinal stations. Suitable model fabrication and experimental techniques have been developed. A simple theoretical method of predicting recession rates and surface temperatures has been proposed. It has been demonstrated that the ablation of carbon dioxide into an unheated Mach 16.4 helium flow at 600 psi stagnation pressure is significant enough to result in measurable flat plate recession rates and measurable changes in pitot pressure profiles. In addition, it has been shown that it is possible to distinguish between the effects on pitot pressure of reduction in surface temperature and of mass addition through sublimation of carbon dioxide. It was also found that the first order theoretical analysis predicts proper trends and correct approximate magnitude of sublimation rates.

  20. Energetic Study of Helium Cluster Nucleation and Growth in 14YWT through First Principles

    Yingye Gan

    2016-01-01

    Full Text Available First principles calculations have been performed to energetically investigate the helium cluster nucleation, formation and growth behavior in the nano-structured ferritic alloy 14YWT. The helium displays strong affinity to the oxygen:vacancy (O:Vac pair. By investigating various local environments of the vacancy, we find that the energy cost for He cluster growth increases with the appearance of solutes in the reference unit. He atom tends to join the He cluster in the directions away from the solute atoms. Meanwhile, the He cluster tends to expand in the directions away from the solute atoms. A growth criterion is proposed based on the elastic instability strain of the perfect iron lattice in order to determine the maximum number of He atoms at the vacancy site. We find that up to seven He atoms can be trapped at a single vacancy. However, it is reduced to five if the vacancy is pre-occupied by an oxygen atom. Furthermore, the solute atoms within nanoclusters, such as Ti and Y, will greatly limit the growth of the He cluster. A migration energy barrier study is performed to discuss the reduced mobility of the He atom/He cluster in 14YWT.

  1. Study of Temperature Wave Propagation in Superfluid Helium Focusing on Radio-Frequency Cavity Cooling

    Koettig, T; Avellino, S; Junginger, T; Bremer, J

    2015-01-01

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches of superconducting radio-frequency cavities. Local hot spots at the cavity surface initiate temperature waves in the surrounding superfluid helium that acts as cooling fluid at typical temperatures in the range of 1.6 K to 2 K. The temperature wave is characterised by the properties of superfluid helium such as the second sound velocity. For high heat load densities second sound velocities greater than the standard literature values are observed. This fast propagation has been verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound is linked to OST signals. The aim of this study is to improve the understanding of the OST signal especially the incident angle dependency. The characterised OSTs are used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resolution was proven to b...

  2. Compatibility of refractory alloys with space reactor system coolants and working fluids

    DeVan, J.H.; DiStefano, J.R.; Hoffman, E.E.

    1984-01-01

    The bulk of this report deals with compatibility studies in liquid lithium and boiling potassium. Substantial information is also presented concerning the reactivity of niobium and tantalum alloys with residual gases in high and ultrahigh vacuum atmospheres. The remaining information, which is much less extensive, covers the compatibility behavior of molybdenum and tungsten alloys in alkali metals and a qualitative assessment of the use of refractory metals for containing helium in a closed Brayton cycle. 22 references, 29 figures, 14 tables

  3. High temperature reactor and helium turbine for naval propeller (Study of feasibility and performances of the system)

    Brisbois, J.; Malherbe, J.; Rastoin, J.; Courau; Metayer.

    1976-01-01

    The nuclear reactor HTGR can get an outlet helium temperature greater than 800 deg C. That gives the means to use an helium turbine in a direct cycle. This type of reactor has been studied for a supply-ship (25,000t, 85,000Cv) and feasibility of such a system can be proved without employing any unknown materials. Because the weakness of helium activity, only the core can be shielded. All the propeller system is inside a containment which has to stand with a small over pressure after a core depressurisation. An efficiency of 35% is realized in a compact set up. This nuclear propeller get a very long core life 860FPD with constant worth- and very flexible working conditions. The HTGR direct cycle make a naval propeller very attractive [fr

  4. Use of naturally occurring helium to estimate ground-water velocities for studies of geologic storage of radioactive waste

    Marine, I.W.

    1977-01-01

    In a study of the potential for storing radioactive waste in metamorphic rock at the Savannah River Plant near Aiken, South Carolina, the rate of water movement was determined to be about 0.06 m/y by analyzing gas dissolved in the water. The gas contained up to 6 percent helium, which originated from the radioactive decay of natural uranium and thorium in the crystalline rock. The residence time of the water in the rock was calculated to be 840,000 years from the quantity of uranium and thorium in the rock, their rates of radioactive decay, and the quantity of helium dissolved in the water. The estimation of ground-water velocities by the helium method is more applicable to the assessment of a geologic site for storage of radioactive waste than are velocities estimated from packer tests, pumping tests, or artificial tracer tests, all of which require extensive time and space extrapolations

  5. Development of Membrane Contactors Using Phase Change Solvents for CO2 Capture: Material Compatibility Study

    Ansaloni, Luca; Asad, Arif; Çiftja, Arlinda; Knuutila, Hanna K; Deng, Liyuan

    2016-01-01

    Phase change solvents represent a new class of CO2 absorbents with a promising potential to reduce the energy penalty associated with CO2 capture. However, their high volatility is a major concern for their use at the industrial scale. It is believed that membrane absorption offers a solution to overcome this issue, particularly if the membrane can prevent amine evaporation. In the present work a compatibility study is carried out in order to identify suitable membranes in a membrane contacto...

  6. Phase boundary in compatible and incompatible polymer blends studied by micro indentation test and microscopic observations

    Mina, M. F.; Akhtar, F.; Haque, M.E.

    2003-10-01

    The phase boundary of incompatible polymer blends such as poly (methyl methacrylate) (PMMA)/natural rubber (NR) and polyestyrene (PS)/NR as well as compatible blends such as PMMA/NR/epoxidizer NR (compatibilizer) and PS/NR/styrene-butadiene-styrene (SBS) block copolymer (compatibilizer) was studied by means of microhardness (H) technique and microscopy. Solution grown films of neat PMMA, PS and blended films of PMMA/NR, PS/NR, PMMA/NR/ENR and PS/NR/SBS were cast using a common solvent (toluene). While the neat PMMA and PS provide constant hardness values of 178 and 173 MPa, respectively, the binary (incompatible) and the ternary (compatible) blends show a conspicuous H-decrease (PMMA/NR=140 MPa, PS/NR=167 MPa, PMMA/NR/ENR=109 MPa and PS/NR/SBS=127 MPa). Scanning electron microscopy and optical microscopy reveal clear difference of the phase boundary of compatible (smooth boundary) and incompatible (sharp boundary) blends. Besides, the compatibilizer blends are characterised by the thinnest phase boundary (30 μm), which is found about 60 μm in the incompatible blends, showing a final hardness value that demonstrates the compatibilizer to be smoothly distributed in the interface between the two blend components. Results highlight that microindentation technique, in combination with microscopic observations, is a sensitive tool for studying the breadth and quality of the interphase boundary in non- or compatibilized polymer blends and other inhomogeneous materials. (author)

  7. Coronene molecules in helium clusters: Quantum and classical studies of energies and configurations

    Rodríguez-Cantano, Rocío; Pérez de Tudela, Ricardo; Bartolomei, Massimiliano; Hernández, Marta I.; Campos-Martínez, José; González-Lezana, Tomás, E-mail: t.gonzalez.lezana@csic.es; Villarreal, Pablo [Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid (Spain); Hernández-Rojas, Javier; Bretón, José [Departamento de Física and IUdEA, Universidad de La Laguna, 38205 Tenerife (Spain)

    2015-12-14

    Coronene-doped helium clusters have been studied by means of classical and quantum mechanical (QM) methods using a recently developed He–C{sub 24}H{sub 12} global potential based on the use of optimized atom-bond improved Lennard-Jones functions. Equilibrium energies and geometries at global and local minima for systems with up to 69 He atoms were calculated by means of an evolutive algorithm and a basin-hopping approach and compared with results from path integral Monte Carlo (PIMC) calculations at 2 K. A detailed analysis performed for the smallest sizes shows that the precise localization of the He atoms forming the first solvation layer over the molecular substrate is affected by differences between relative potential minima. The comparison of the PIMC results with the predictions from the classical approaches and with diffusion Monte Carlo results allows to examine the importance of both the QM and thermal effects.

  8. Study of the high-pressure helium phase diagram using molecular dynamics

    Koci, L; Ahuja, R; Belonoshko, A B; Johansson, B

    2007-01-01

    The rich occurrence of helium and hydrogen in space makes their properties highly interesting. By means of molecular dynamics (MD), we have examined two interatomic potentials for 4 He. Both potentials are demonstrated to reproduce high-pressure solid and liquid equation of state (EOS) data. The EOS, solid-solid transitions and melting at high pressures (P) were studied using a two-phase method. The Buckingham potential shows a good agreement with theoretical and experimental EOS, but does not reproduce experimental melting data. The Aziz potential shows a perfect match with theoretical melting data. We conclude that there is a stable body-centred-cubic (bcc) phase for 4 He at temperatures (T) above 340 K and pressures above 22 GPa for the Buckingham potential, whereas no bcc phase is found for the Aziz potential in the applied PT range

  9. Use of tritium and helium-3 for oceanographic processes study. An example: the Northeastern Atlantic Ocean

    Andrie, C.; Merlivat, L.

    1987-01-01

    These results are relative to the TOPOGULF cruise during summer 1983. The sampled area is located near the Azores Islands on the both sides of the mid atlantic ridge. The tritium content of the surface waters reveals a strong front along the Azores current. At depth, the spatial distribution of tritium is studied along isopycnals. In the thermocline, it is essentially the anticyclonic gyre which is responsible for the northeast - southwest gradient in tritium concentration. Some informations about the age of the water masses are given by the use of both tritium and Helium-3. By this way are identified some areas where ventilation processes are active. At middepth, a strong contrast exists between the young waters originating from the Labrador Sea and the more stagnant waters in the South East of the sampled area

  10. A comparative study of tribological characteristics of hydrogenated DLC film sliding against ceramic mating materials for helium applications

    Wu, Daheng; Ren, Siming; Pu, Jibin; Lu, Zhibin; Zhang, Guangan; Wang, Liping

    2018-05-01

    The tribological behaviors of hydrogenated DLC film sliding against Al2O3, ZrO2, Si3N4 and WC mating balls have been comparatively investigated by a ball-on-disk tribometer at 150 °C under helium and air (RH = 6%) conditions. The results showed that the mating material influenced the friction and wear behavior remarkably in helium atmosphere, where the wear rates were in inversely proportional to the friction coefficients (COF) of those tribo-pairs. Compared to the tests in helium, the tribological performance of DLC film significantly improved in air. Scanning electron microscope (SEM) and Raman spectroscopy were performed to study the friction behavior and wear mechanism of the film under different conditions. It suggested that the severe abrasion was caused by the strong interaction between the tribo-pairs in helium atmosphere at 150 °C, whereas the sufficient passivation of the dangling bonds of carbon atoms at sliding interface by chemically active molecules, such as water and oxygen, dominated the ultralow friction under air condition. Meanwhile, Hertz analysis was used to further elucidate the frictional mechanism of DLC film under helium and air conditions. It showed that the coefficient of friction was consistent with the varied tendency of the contact radius, namely, higher friction coefficient corresponded to the larger contact radius, which was the same with the relationship between the wear rate and the contact pressure. All of the results made better understanding of the essential mechanism of hydrogenated DLC film sliding against different pairs, which were able to guide the further application of DLC film in the industrial fields of helium atmosphere.

  11. Study concerning the compatibility of the mixture of nylon-6 and poly(propylene oxide) through solid state NMR

    Tavares, Maria I.B.; Costa, D.A.; Menezes, Sonia M.C.

    1993-01-01

    NMR has been frequently used for the determination of polymers compatibility. The utilization of the simple pulse technique together with the contact time variation technique has been enabling the evaluation of the compatibility of polymeric systems. This work presents the study of the behaviour of the mixture composed by nylon-6 with poly(propylene oxide) using these techniques. Results are presented

  12. Scaled experiments using the helium technique to study the vehicular blockage effect on longitudinal ventilation control in tunnels

    Alva, Wilson Ulises Rojas; Jomaas, Grunde; Dederichs, Anne

    2015-01-01

    A model tunnel (1:30 compared to a standard tunnel section) with a helium-air smoke mixture was used to study the vehicular blockage effect on longitudinal ventilation smoke control. The experimental results showed excellent agreement with full-scale data and confirmed that the critical velocity...

  13. Study of the helium cross-section of unsymmetric disulfide self-assembled monolayers on Au(111)

    Albayrak, Erol [Department of Materials and Metallurgical Engineering, Ahi Evran University, Kırşehir 40000 (Turkey); Karabuga, Semistan [Department of Chemistry, Kahramanmaraş Sütçü İmam University, Kahramanmaraş 46030 (Turkey); Bracco, Gianangelo [CNR-IMEM and Department of Physics, University of Genoa, Via Dodecaneso 33, Genoa 16146 (Italy); Danışman, M. Fatih, E-mail: danisman@metu.edu.tr [Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey)

    2016-12-30

    Highlights: • Unsymmetrtic disulfide (HDD and HOD) self assembled monolayers were grown on Au(111) by supersonic molecular beam deposition. • Helium scattering cross sections for these two different unsymmetric disulfides were determined. • A common low temperature film phase was observed for the studied disulfides. - Abstract: We have investigated the formation of self-assembled monolayers (SAMs) of 11-hydroxyundecyl decyl disulfide (CH{sub 3}-(CH{sub 2}){sub 9}-S-S-(CH{sub 2}){sub 11}-OH, HDD) and 11-hydroxyundecyl octadecyl disulfide (CH{sub 3}-(CH{sub 2}){sub 17}-S-S-(CH{sub 2}){sub 11}-OH, HOD) produced by supersonic molecular beam deposition (SMBD). The study has been carried out by means of helium diffraction at very low film coverage. In this regime helium single molecule cross sections have been estimated in a temperature range between 100 K and 450 K. The results show a different behavior above 300 K that has been interpreted as the starting of mobility with the formation of two thiolate moieties either linked by a gold adatom or distant enough to prevent cross section overlapping. Finally, helium diffraction patterns measured at 80 K for the SAMs grown at 200 K are discussed and the results support the proposed hypothesis of molecular dissociation based on the cross section data.

  14. Chemical compatibility study of Cooley L18KU, Herculite, and Elephant Mat with Hanford tank waste

    Mercado, J.E.

    1998-01-01

    An independent chemical compatibility review of various wrapping and absorbent/padding materials was conducted to evaluate resistance to chemicals and constituents present in liquid waste from the Hanford underground tanks. These materials will be used to wrap long-length contaminated equipment when such equipment is removed from the tanks and prepared for transportation and subsequent disposal or storage. The materials studied were Cooley L18KU, Herculite, and Elephant Mat. The study concludes that these materials are appropriate for use in this application

  15. Study of helium behaviour in body-centered cubic structures for new nuclear reactor generations: experimental approach in well characterized materials

    Gorondy-Novak, Sofia Maria

    2017-01-01

    The presence of helium produced during the operation of future fast reactors and fusion reactors in core structural materials induces a deterioration of their mechanical properties (hardening, swelling, embrittlement). In order to pursue the development of the metallic structural alloys, it is necessary to comprehend the He interaction with the metal lattice thus the point in common is the study of the metallic components with body-centered cubic structure (bcc) of future alloys, such as iron and/or vanadium. Ion implantation of ions "4He was employed with the aim of simulating the damaging effects associated with the helium accumulation, the point defects' creation (vacancies, self-interstitials) and the He cluster formation in future reactors. Helium evolution in pure iron and pure vanadium has been revealed from the point of view of the trapping sites' nature and well as the helium migration mechanisms and the nucleation/growth of bubbles. These phenomena were studied by coupling different complementary techniques. Despite of the fact that some mechanisms involved seem to be similar for both bcc metals, the comparison between the helium behavior in iron and vanadium shows certain differences. Microstructural defects, including grain boundaries and implanted helium concentration (dose) in both bcc metals will play significant roles on the helium behavior at high temperature. The acquired experimental data coupled with simulation methods contribute to the future development in terms of kinetic and thermodynamic data management of helium behavior in the metal components of the alloys of nuclear interest. (author) [fr

  16. Study of observed broad dielectric relaxation and compatibility of polysulfone - Polyvinylidenefluoride blends

    Patel, Swarnim; Shrivas, Sandhya; Dubey, R. K.; Keller, J. M.

    2018-05-01

    Short circuit thermally stimulated depolarization current measurement techniques has been employed to investigate the dielectric relaxation behavior of PSF: PVDF blends. The samples taken were blends of composition PSF: PVDF:: 80:20; 85:15; 90:10 and 95:05 percent by weight. The thermograms were characterized by a high value of initial current, a low temperature peak around 75-80°C and a prominent broad peak in the temperature interval 130 to 160°C. The two polymers are found to form compatible blend in the studied composition range.

  17. Compatibility studies of potential molten-salt breeder reactor materials in molten fluoride salts

    Keiser, J.R.

    1977-05-01

    The molten fluoride salt compatibility studies carried out during the period 1974--76 in support of the Molten-Salt Reactor Program are summarized. Thermal-convection and forced-circulation loops were used to measure the corrosion rate of selected alloys. Results confirmed the relationship of time, initial chromium concentration, and mass loss developed by previous workers. The corrosion rates of Hastelloy N and Hastelloy N modified by the addition of 1--3 wt percent Nb were well within the acceptable range for use in an MSBR. 13 figures, 3 tables

  18. Study of the short distance interaction between two nucleons in helium-3 and helium-4 nuclei through (e,e'p) reaction

    Le Goff, Jean-Marc

    1991-01-01

    A recent experiment has shown that it was possible to scatter inelastically on a pair of nucleons interacting at short distance inside a 3-Helium nucleus without interacting with the third nucleon. In order to study the same process in a more compact nucleus, 4-Helium, we have measured the cross section of the 4 He(e,e'p)x reaction for recoil momenta between 225 and 500 MeV/c. This experiment clearly exhibits a pair of nucleons interacting inside the 4-helium nucleus. From the kinematical point of view, the continuum shows a 'bumpy' shape, this bump shifts with increasing recoil momentum in a characteristic way. From the dynamical point of view, an overall agreement is observed between the data and a microscopic calculation, this calculation predicts that scattering on an interacting pair is the dominant process. Furthermore, above 250 MeV/c, the momentum distribution in the continuum appears very close to the momentum distribution of deuterium. In order to get a better understanding of the reaction mechanism in these measurements of high momentum, we have performed a transverse longitudinal separation of the 3 He(e,e'p)x cross section at the highest possible recoil momentum, 260 MeV/c. Since the two responses involve different couplings (respectively magnetic and coulomb coupling), this technique provides us with a very good test of our understanding of the reaction. The experimental responses have been compared to a microscopic calculation. This calculation cannot reproduce simultaneously the two responses. According to the wave function, it either slightly overestimates the longitudinal and strongly underestimates the transverse, or it clearly overestimates the longitudinal and slightly underestimates the transverse. It is interesting to consider the ratio between the integral of the longitudinal and the transverse one, since it is independent of the wave function: its theoretical value is 0.429, whereas a ratio of 0.175±0.046±0.049 is

  19. Chemical compatibility study of lithium titanate with Indian reduced activation ferritic martensitic steel

    Sonak, Sagar; Jain, Uttam; Haldar, Rumu; Kumar, Sanjay

    2015-01-01

    Highlights: • Chemical compatibility between Li_2TiO_3 and Indian RAFM steel has been studied at ITER operating temperature. • The lithium titanate chemically reacted with ferritic martensitic steel to form a brittle and non-adherent oxide layer. • The layer grew in a parabolic manner as a function of heating time. • Diffusion of oxygen (from Li_2TiO_3) appears to be controlling the oxide layer. - Abstract: Chemical compatibility between lithium titanate and Indian reduced activation ferritic-martensitic steel (In-RAFMS) was studied for the first time under ITER operating temperature. Lithium titanate required for the study was synthesized in-house. Coupons of In-RAFMS were packed inside lithium titanate powder and heated at 550 °C up to 900 h under inert argon atmosphere. The lithium titanate chemically reacted with ferritic martensitic steel to form a brittle and non-adherent oxide layer. The layer grew in a parabolic manner as a function of heating time. Microstructural and phase evolution of this oxide layer was studied using XRD, SEM and EPMA. Iron and chromium enriched zones were found within the oxide layer. Diffusion of oxygen (from Li_2TiO_3) appears to be controlling the oxide layer.

  20. Study of helium and beryllium atoms with strong and short laser field; Etude des atomes d'helium et de beryllium en champ laser intense et bref

    Laulan, St

    2004-09-01

    We present a theoretical study of the interaction between a two-active electron atom and an intense (10{sup 14} to 10{sup 15} W/cm{sup 2}) and ultrashort (from a few 10{sup -15} to a few 10{sup -18} s) laser field. In the first part, we describe the current experimental techniques able to produce a coherent radiation of high power in the UV-XUV regime and with femtosecond time duration. A theoretical model of a laser pulse is defined with such characteristics. Then, we develop a numerical approach based on B-spline functions to describe the atomic structure of the two-active electron system. A spectral non perturbative method is proposed to solve the time dependent Schroedinger equation. We focalize our attention on the description of the atomic double continuum states. Finally, we expose results on the double ionization of helium and beryllium atoms with intense and short laser field. In particular, we present total cross section calculations and ejected electron energy distributions in the double continuum after one- and two-photon absorption. (author)

  1. Drug-Drug/Drug-Excipient Compatibility Studies on Curcumin using Non-Thermal Methods

    Moorthi Chidambaram

    2014-05-01

    Full Text Available Purpose: Curcumin is a hydrophobic polyphenol isolated from dried rhizome of turmeric. Clinical usefulness of curcumin in the treatment of cancer is limited due to poor aqueous solubility, hydrolytic degradation, metabolism, and poor oral bioavailability. To overcome these limitations, we proposed to fabricate curcumin-piperine, curcumin-quercetin and curcumin-silibinin loaded polymeric nanoformulation. However, unfavourable combinations of drug-drug and drug-excipient may result in interaction and rises the safety concern. Hence, the present study was aimed to assess the interaction of curcumin with excipients used in nanoformulations. Methods: Isothermal stress testing method was used to assess the compatibility of drug-drug/drug-excipient. Results: The combination of curcumin-piperine, curcumin-quercetin, curcumin-silibinin and the combination of other excipients with curcumin, piperine, quercetin and silibinin have not shown any significant physical and chemical instability. Conclusion: The study concludes that the curcumin, piperine, quercetin and silibinin is compatible with each other and with other excipients.

  2. Study on Compatibility of Polymer Hydrodynamic Size and Pore Throat Size for Honggang Reservoir

    Dan-Dan Yin

    2014-01-01

    Full Text Available Long core flow experiment was conducted to study problems like excessive injection pressure and effective lag of oil wells during the polymer flooding in Honggang reservoir in Jilin oilfield. According to the changes in viscosity and hydrodynamic dimensions before and after polymer solution was injected into porous media, the compatibility of polymer hydrodynamic dimension and the pore throat size was studied in this experiment. On the basis of the median of radius R of pore throats in rocks with different permeability, dynamic light scattering method (DLS was adopted to measure the hydrodynamic size Rh of polymer solution with different molecular weights. The results state that three kinds of 1500 mg/L concentration polymer solution with 2000 × 104, 1500 × 104, and 1000 × 104 molecular weight matched well with the pore throat in rocks with permeability of 300 mD, 180 mD, and 75 mD in sequence. In this case, the ratios of core pore throat radius median to the size of polymer molecular clew R/Rh are 6.16, 5.74, and 6.04. For Honggang oil reservoir in Jilin, when that ratio ranges from 5.5 to 6.0, the compatibility of polymer and the pore structure will be relatively better.

  3. Obtention of graft copolymers by ionizing radiation, characterization and study of hemo-compatible properties

    Queiroz, A.A.A. de.

    1993-01-01

    The present work had as objectives the obtention and characterization of grafting copolymers by radiation induced polymerization and the study of its hemo compatible properties. The relationship between grafting conditions and anti-trombogenicity was examined for the purpose of clearing the necessity of controlling grafting conditions to enhance the copolymers blood compatibility. Two methods were chosen to accomplish the irradiation: mutual and pre-irradiation (peroxidation) of the films in 6O Co source and electron beam accelerator. Primarily grafting parameters were studied in the systems of the monomers N, N-dimethyl acrylamide (DMAA) and acrylic acid (AA) with the polymeric films: poly (tetrafluoroethylene) (PTFE), poly (ethylene-co-tetrafluoroethylene) (PETFE), low density polyethylene (LDPE) and poly (vinyl chloride) (PVC). The simultaneous irradiation was effective in the polymerization of all the substrates above mentioned, although the peroxidation method has given better results for PETFE-DMAA, LDPE-g-DMAA, LDPE-g-AA and PVC-g-AA. In the system AA/LDPE and AA/PVC the homo polymerization was controlled by the addition of the comonomer N, N-dimethyl acrylic acid (DMA). As for the grafting parameters, low dose rate and low irradiation dose, showed to be very effective for the graftability of DMAA and AA on the substrates. (author). 129 refs, 51 figs, 7 tabs

  4. Studies of Helium Based Gas Mixtures Using a Small Cell Drift Chamber

    Heise, Jaret; British Columbia U.

    2006-01-01

    An international collaboration is currently working on the construction and design of an asymmetric B Factory at the Stanford Linear Accelerator Center that will be ready to collect data in 1999. The main physics motivation for such a facility is to test the description and mechanism of CP violation in the Standard Model of particle physics and provide insight into the question of why more matter than antimatter is observed in the universe today. In particular, this experiment will measure CP violation in the decay of B mesons. In the early stages of this effort, the Canadian contingent proposed to build the central tracking chamber for the BABAR detector. Presently, a prototype drift chamber is in operation and studies are being performed to test some of the unique features of drift chamber design dictated by the conditions of the experiment. Using cosmic muons, it is possible to study tracking and pattern recognition in the prototype chamber, and therefore calculate the efficiency and spatial resolution of the prototype chamber cells. These performance features will be used to test whether or not the helium-based gas mixtures proposed for the BABAR drift chamber are a viable alternative to the more traditional argon-based gases

  5. Electromagnetic Compatibility Studies: LTE BS vs. Aeronautical Radionavigation Services in 694-790 MHz Frequency Band

    Stankevičius Evaldas

    2014-10-01

    Full Text Available This paper presents the sharing analysis of the 694–790 MHz frequency band for Mobile services IMT and Aeronautical radio-navigation services (ARNS using SEAMCAT (established by CEPT software based on the statistical simulation (Monte-Carlo method. In 2012 the World Radiocommunication Conference (WRC-12 decided to allocate the 694–790 MHz frequency band (the so-called 700 MHz band to mobile services IMT (excluding aeronautical mobile after WRC-15 conference. But this agreement raises electromagnetic compatibility problems, which should be solved until WRC-15 [1]. This study was carried out in two phases: first applying theoretical analysis, then statistical Monte-Carlo simulations with SEAMCAT software tool in order to verify results obtained in theoretical approach. Analytical calculations shows that the required protection distances between ARNS stations and the MS base stations are 132 km. The obtained results from SEAMCAT simulations indicate that separation distance should be above 100 km. These results illustrate that the systems are not electromagnetically compatible. The possible mitigation technic could be antenna pattern correction.

  6. Development and study of airborne spectrometer system being compatible with nuclear emergency monitoring

    Jiangqi, Fang; Huaiwu, Wang; Mingkao, Hu; Renkang, Gu

    2002-01-01

    The exploitation and use of nuclear energy are of great importance to developing of national economy and maintaining state security. But it also has a possibility of serious accident. Based on the principles of airborne gamma ray spectrometry in the uranium exploration, nuclear emergency monitoring has been developed. This method has high sensitivity to the radioactive nuclides in the air and on the ground, and with the advantage of fast measuring in large area. Hence, in the middle of 1980s, some developed countries began to survey the scope and degree of nuclear accident contamination and environmental radiation level monitoring in the surrounding nuclear facilities, it can also be used to search for the lost radioactive sources. According to the actual situation and compatible guideline, National Nuclear Emergency Office consigned this project to our Center. After development and study on the Airborne gamma ray spectrometer system associated NaI(Tl) used for the uranium exploration, a compatible spectrometer system associated NaI(Tl) was established in a short period by us, which can fulfill airborne nuclear emergency survey basically. In normal situation, it was proved that the start-up time is less than two hours including transport to the airport. The system has high sensitivity to radioactive plume of 41 Ar and can respond rapidly to artificial sources, such as 192 Ir, 60 Co, 137 Cs and 131 I etc

  7. Recent materials compatibility studies in refractory metal-alkali metal systems for space power applications.

    Harrison, R. W.; Hoffman, E. E.; Davies, R. L.

    1972-01-01

    Advanced Rankine and other proposed space power systems utilize refractory metals in contact with both single-phase and two-phase alkali metals at elevated temperatures. A number of recent compatibility experiments are described which emphasize the excellent compatibility of refractory metals with the alkali metals, lithium, sodium, and potassium, under a variety of environmental conditions. The alkali metal compatibilities of tantalum-, columbium-, molybdenum-, and tungsten-base alloys are discussed.

  8. Comparative study of image contrast in scanning electron microscope and helium ion microscope.

    O'Connell, R; Chen, Y; Zhang, H; Zhou, Y; Fox, D; Maguire, P; Wang, J J; Rodenburg, C

    2017-12-01

    Images of Ga + -implanted amorphous silicon layers in a 110 n-type silicon substrate have been collected by a range of detectors in a scanning electron microscope and a helium ion microscope. The effects of the implantation dose and imaging parameters (beam energy, dwell time, etc.) on the image contrast were investigated. We demonstrate a similar relationship for both the helium ion microscope Everhart-Thornley and scanning electron microscope Inlens detectors between the contrast of the images and the Ga + density and imaging parameters. These results also show that dynamic charging effects have a significant impact on the quantification of the helium ion microscope and scanning electron microscope contrast. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

  9. Preliminary study on helium turbomachine for high temperature gas-cooled reactor

    Chen Yihua; Wang Jie; Zhang Zuoyi

    2003-01-01

    In the high temperature gas-cooled reactor (HTGR), gas turbine cycle is a new concept in the field of nuclear power. It combines two technologies of HTGR and gas turbine cycle, which represent the state-of-the-art technologies of nuclear power and fossil fuel generation respectively. This approach is expected to improve safety and economy of nuclear power plant significantly. So it is a potential scheme with competitiveness. The heat-recuperated cycle is the main stream of gas turbine cycle. In this cycle, the work medium is helium, which is very different from the air, so that the design features of the helium turbomachine and combustion gas turbomachine are different. The paper shows the basic design consideration for the heat-recuperated cycle as well as helium turbomachine and highlights its main design features compared with combustion gas turbomachine

  10. Study of edge plasma properties comparing operation in hydrogen and helium in RFX

    Spolaore, M.; Antoni, V.; Bagatin, M.; Desideri, D.; Fattorini, L.; Martines, E.; Serianni, G.; Tramontin, L.; Vianello, N.

    2001-01-01

    The properties of the edge plasma in the reversed field pinch RFX have been investigated by comparing the operation in helium with those normally performed in hydrogen. It has been found that a spontaneous velocity shear layer takes place in the edge region also in helium discharges. The edge structure of hydrogen and helium discharges have been interpreted using a momentum balance equation, which takes into account anomalous viscosity and friction with neutrals. The electrostatic turbulence properties are also compared: it is found that electrostatic turbulence drives most of the particle losses and a small fraction of the energy losses also for the He discharges. The modifications of the mean profiles, including the ExB velocity, during PPCD are briefly discussed and compared with the results obtained in hydrogen

  11. Photoionization study of doubly-excited helium at ultra-high resolution

    Kaindl, G.; Schulz, K.; Domke, M. [Freie Universitaet Berlin (Germany)] [and others

    1997-04-01

    Ever since the pioneering work of Madden & Codling and Cooper, Fano & Prats on doubly-excited helium in the early sixties, this system may be considered as prototypical for the study of electron-electron correlations. More detailed insight into these states could be reached only much later, when improved theoretical calculations of the optically-excited {sup 1}P{sup 0} double-excitation states became available and sufficiently high energy resolution ({delta}E=4.0 meV) was achieved. This allowed a systematic investigation of the double-excitation resonances of He up to excitation energies close to the double-ionization threshold, I{sub infinity}=79.003 eV, which stimulated renewed theoretical interest into these correlated electron states. The authors report here on striking progress in energy resolution in this grazing-incidence photon-energy range of grating monochromators and its application to hitherto unobservable states of doubly-excited He. By monitoring an extremely narrow double-excitation resonance of He, with a theoretical lifetime width of less than or equal to 5 {mu}eV, a resolution of {delta}E=1.0 meV (FWHM) at 64.1 eV could be achieved. This ultra-high spectral resolution, combined with high photon flux, allowed the investigation of new Rydberg resonances below the N=3 ionization threshold, I{sub 3}, as well as a detailed comparison with ab-initio calculations.

  12. Mass spectrometer diagnostic technique in the study of stationary afterglow plasmas in helium, argon and krypton

    Langenwalter, M.

    1979-01-01

    Since some years the method of massspectrometric monitoring has become an important tool in the analysis of time resolved (or stationary) afterglow plasmas. The present thesis reports the construction and testing of a new fully bakeable UHV-stationary-afterglow-apparatus using a hollow cathode discharge as plasma source for the first time. The hollow cathode is moveable perpendicular to its axis relative to the sampling orifice (i.e. a very small hole at the centre of the plasma container's boundary), so that the radical distribution of the charged particle density can be studied. Several specific extraction conditions for ions from the plasma especially the sampling probe potential have been systematically investigated. Results are illustrated and discussed. The new apparatus has been tested by determining the ambipolar diffusion coefficient of the molecular ion He 2 + in a pure Helium-plasma in thermal equilibrium. The present result (Dsub(a2) = 603 +- 38 / P 0 cm 2 s -1 ) is in agreement with results reported by other workers. Finally an example for the radial behaviour of the Ar + -sampling current in an Argon-discharge for several different times in the afterglow period is given. The shown behaviour agrees relatively well with the theoretically predicted radial ion density distribution, i.e. the zero-order Ressel'function. (Author)

  13. Helium implanted RAFM steels studied by positron beam Doppler Broadening and Thermal Desorption Spectroscopy

    Carvalho, I; Schut, H; Fedorov, A; Luzginova, N; Desgardin, P; Sietsma, J

    2013-01-01

    Reduced Activation Ferritic/Martensitic steels are being extensively studied because of their foreseen application in fusion and Generation IV fission reactors. To mimic neutron irradiation conditions, Eurofer97 samples were implanted with helium ions at energies of 500 keV and 2 MeV and doses of 5x10 15 -10 16 He /cm 2 , creating atomic displacements in the range 0.07–0.08 dpa. The implantation induced defects were characterized by positron beam Doppler Broadening (DB) and Thermal Desorption Spectroscopy (TDS). The DB data could be fitted with one or two layers of material, depending on the He implantation energy. The S and W values obtained for the implanted regions suggest the presence of not only vacancy clusters but also positron traps of the type present in a sub-surface region found on the reference sample. The traps found in the implanted layers are expected to be He n V m clusters. For the 2 MeV, 10 16 He/cm 2 implanted sample, three temperature regions can be observed in the TDS data. Peaks below 450 K can be ascribed to He released from vacancies in the neighbourhood of the surface, the phase transition is found at 1180 K and the peak at 1350 K is likely caused by the migration of bubbles.

  14. Radiolysis study of actinide complexing agent by irradiation with helium ion beam

    Sugo, Yumi; Taguchi, Mitsumasa; Sasaki, Yuji; Hirota, Koichi; Kimura, Takaumi

    2009-01-01

    α-Radiolysis of N,N,N',N'-tetraoctyldiglycolamide (TODGA) in n-dodecane was investigated by the irradiation with helium ion beam provided by a tandem accelerator. The radiation chemical yield for the degradation of TODGA by helium ion beam irradiation was less than that by γ-rays irradiation. It is considered that the radical cations of n-dodecane, which contribute to the charge transfer reaction with the TODGA molecules, decrease by recombination in track by high LET radiations such as α-particles.

  15. Contribution to the study of solid helium-3 by nuclear magnetic resonance; Contribution a l'etude de l'helium trois solide par resonance magnetique nucleaire

    Landesman, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    Due to the unusually large zero point motion of helium three atoms in the solid, the overlap of the atomic wave functions is very important. As a consequence, there are exchange interactions, the theoretical calculation and the experimental measurement of which are discussed. Nuclear magnetic resonance is especially well suited for the latter.A detailed theory is given for both exchange narrowing and Zeeman-exchange cross relaxation, which phenomena are used to measure the exchange interaction as a function of molar volume. The alignment temperature is thus known; it goes down when the pressure goes up and is never higher than three milli degrees. An influence of helium four impurities on the exchange interactions between helium three atoms which are neighbours of the substitutional He is shown. (author) [French] Par suite de l'amplitude exceptionnelle des mouvements de point zero dans l'helium trois solide, le recouvrement des fonctions d'onde atomiques est tres important. Il en resulte des interactions d' echange dont on discute l'evaluation theorique et la mise en evidence experimentale. Cette derniere peut se faire par resonance magnetique; on etudie theoriquement les phenomenes de retrecissement par echange et de relaxation Zeeman-echange que l'on met a profit pour determiner les interactions d'echange en fonction du volume molaire. On en deduit que la temperature d'alignement nucleaire diminue quand on comprime le solide et est au plus de 3x10{sup -3} K. L'influence des impuretes d'helium quatre sur les interactions d'echange entre atomes {sup 3}He voisins de {sup 4}He est mise en evidence. (auteur)

  16. Helium behaviour in nuclear glasses

    Fares, T.

    2011-01-01

    The present thesis focuses on the study of helium behavior in R7T7 nuclear waste glass. Helium is generated by the minor actinides alpha decays incorporated in the glass matrix. Therefore, four types of materials were used in this work. These are non radioactive R7T7 glasses saturated with helium under pressure, glasses implanted with 3 He + ions, glasses doped with curium and glasses irradiated in nuclear reactor. The study of helium solubility in saturated R7T7 glass has shown that helium atoms are inserted in the glass free volume. The results yielded a solubility of about 10 16 at. cm -3 atm. -1 . The incorporation limit of helium in this type of glass has been determined; its value amounted to about 2*10 21 at. cm -3 , corresponding to 2.5 at.%. Diffusion studies have shown that the helium migration is controlled by the single population dissolved in the glass free volume. An ideal diffusion model was used to simulate the helium release data which allowed to determine diffusion coefficients obeying to the following Arrhenius law: D = D 0 exp(-E a /kBT), where D 0 = 2.2*10 -2 and 5.4*10 -3 cm 2 s -1 and E a = 0.61 eV for the helium saturated and the curium doped glass respectively. These results reflect a thermally activated diffusion mechanism which seems to be not influenced by the glass radiation damage and helium concentrations studied in the present work (up to 8*10 19 at. g -1 , corresponding to 0.1 at.%). Characterizations of the macroscopic, structural and microstructural properties of glasses irradiated in nuclear reactor did not reveal any impact associated with the presence of helium at high concentrations. The observed modifications i.e. a swelling of 0.7 %, a decrease in hardness by 38 %, an increase between 8 and 34 % of the fracture toughness and a stabilization of the glass structure under irradiation, were attributed to the glass nuclear damage induced by the irradiation in reactor. Characterizations by SEM and TEM of R7T7 glasses implanted

  17. Numerical studies on helium cooled divertor finger mock up with sectorial extended surfaces

    Rimza, Sandeep; Satpathy, Kamalakanta; Khirwadkar, Samir; Velusamy, Karupanna

    2014-01-01

    Highlights: • Studies on heat transfer enhancement for divertor finger mock-up. • Heat transfer characteristics of jet impingement with extended surfaces have been investigated. • Effect of critical parameters that influence the thermal performance of the finger mock-up by CFD approach. • Effect of extended surface in enhancing heat removal potential with pumping power assessed. • Practicability of the chosen design is verified by structural analysis. - Abstract: Jet impinging technique is an advance divertor concept for the design of future fusion power plants. This technique is extensively used due to its high heat removal capability with reasonable pumping power and for safe operation. In this design, plasma-facing components are fabricated with numerous fingers cooled by helium jets to reduce the thermal stresses. The present study is focused towards finding an optimum performance of one such finger mock-up through systematic computational fluid dynamics (CFD) studies. Heat transfer characteristics of jet impingement have been numerically investigated with sectorial extended surfaces (SES). The result shows that addition of SES enhances heat removal potential with minimum pumping power. Detailed parametric studies on critical parameters that influence thermal performance of the finger mock-up have been analyzed. Thermo-mechanical analysis has been carried out through finite element based approach to know the state of stress in the assembly as a result of large temperature gradients. It is seen that the stresses are within the permissible limits for the present design. The whole numerical simulation has been carried out using general-purpose CFD software (ANSYS FLUENT, Release 14.0, User Guide, Ansys, Inc., 2011). Benchmark validation studies have been performed against high-heat flux experiments (B. Končar, P. Norajitra, K. Oblak, Appl. Therm. Eng., 30, 697–705, 2010) and a good agreement is noticed between the present simulation and the reported

  18. Differential scanning calorimetry as a screening technique in compatibility studies of acyclovir extended release formulations

    Barboza, Fernanda M.; Vecchia, Debora D.; Tagliari, Monika P.; Ferreira, Andrea Granada; Silva, Marcos A.S.; Stulzer, Hellen K.

    2009-01-01

    Acyclovir (ACV) has been investigated during the past years, mainly due to its antiviral activity. Assessment of possible incompatibility between an active component and different excipients along with the evaluation of thermal stability are crucial parts of a normal study prior to the final formulation setting of a medicine. Thermal analysis studies were used as important and complementary tools during pre-formulation to determine the compatibility of drug excipients with the purpose of developing an acyclovir extended release formulation. Fourier transform infrared spectroscopy and X-ray powder diffraction analyses were also realized. The results showed that ACV only exhibited interaction which could influence the stability of the product in the binary mixtures of ACV/magnesium stearate. (author)

  19. Clustering of Helium Atoms at a ½

    Berg, F. v.d.; Heugten, W. v.; Caspers, L.M.; Veen, A. v.; Hosson, J.Th.M. de

    1977-01-01

    Atomistic calculations on a ½<111>{110} edge dislocation show a restricted tendency of clustering of helium atom along this dislocation. Clusters with up to 4 helium atoms have been studied. A cluster with 3 helium proved to be most stable.

  20. Theoretical study of helium insertion and diffusion in 3C-SiC

    Van Ginhoven, Renee M.; Chartier, Alain; Meis, Constantin; Weber, William J.; Rene Corrales, L.

    2006-01-01

    Insertion and diffusion of helium in cubic silicon carbide have been investigated by means of density functional theory. The method was assessed by calculating relevant properties for the perfect crystal along with point defect formation energies. Results are consistent with available theoretical and experimental data. Helium insertion energies were calculated to be lower for divacancy and silicon vacancy defects compared to the other mono-vacancies and interstitial sites considered. Migration barriers for helium were determined by using the nudged elastic band method. Calculated activation energies for migration in and around vacancies (silicon vacancy, carbon vacancy or divacancy) range from 0.6 to 1.0 eV. Activation energy for interstitial migration is calculated to be 2.5 eV. Those values are discussed and related to recent experimental activation energies for migration that range from 1.1 [P. Jung, J. Nucl. Mater. 191-194 (1992) 377] to 3.2 eV [E. Oliviero, A. van Veen, A.V. Fedorov, M.F. Beaufort, J.F. Bardot, Nucl. Instrum. Methods Phys. Res. B 186 (2002) 223; E. Oliviero, M.F. Beaufort, J.F. Bardot, A. van Veen, A.V. Fedorov, J. Appl. Phys. 93 (2003) 231], depending on the SiC samples used and on helium implantation conditions

  1. Helium, iron and electron particle transport and energy transport studies on the TFTR tokamak

    Synakowski, E.J.; Efthimion, P.C.; Rewoldt, G.; Stratton, B.C.; Tang, W.M.; Grek, B.; Hill, K.W.; Hulse, R.A.; Johnson, D.W.; Mansfield, D.K.; McCune, D.; Mikkelsen, D.R.; Park, H.K.; Ramsey, A.T.; Redi, M.H.; Scott, S.D.; Taylor, G.; Timberlake, J.; Zarnstorff, M.C.

    1993-03-01

    Results from helium, iron, and electron transport on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor

  2. Helium, Iron and Electron Particle Transport and Energy Transport Studies on the TFTR Tokamak

    Synakowski, E. J.; Efthimion, P. C.; Rewoldt, G.; Stratton, B. C.; Tang, W. M.; Grek, B.; Hill, K. W.; Hulse, R. A.; Johnson, D .W.; Mansfield, D. K.; McCune, D.; Mikkelsen, D. R.; Park, H. K.; Ramsey, A. T.; Redi, M. H.; Scott, S. D.; Taylor, G.; Timberlake, J.; Zarnstorff, M. C. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Kissick, M. W. (Wisconsin Univ., Madison, WI (United States))

    1993-03-01

    Results from helium, iron, and electron transport on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.

  3. Study on Compatibility between Converters and Casting Machines for Daily Steelmaking and Continuous Casting Scheduling

    MA Feng-cai; ZHANG Qun

    2009-01-01

    In this paper, daily production scheduling is studied based on the Third Steelmaking Plant of Wuhan Iron and steel corporation (WISCO). To make sure the daily production plan is feasible, method of casting gToup is established, and the compatibility between two converters and three continuous casting devices in the Third Steelmaking Plant of WISCO is analyzed. The process flow chart of daily production scheduling is given in this paper. Then, algorithms and procedures for the simulation of daily production plan is developed. Using the actual data from the Third Steelmaking Plant, the feasible daily steelmaking plan and cast plan are given. The plan contains 7 groups of cast plan, figured out 54 converters, and a- bout 13,500 tons steel.

  4. The SYNERGY biodegradable polymer everolimus eluting coronary stent: Porcine vascular compatibility and polymer safety study.

    Wilson, Gregory J; Marks, Angela; Berg, Kimberly J; Eppihimer, Michael; Sushkova, Natalia; Hawley, Steve P; Robertson, Kimberly A; Knapp, David; Pennington, Douglas E; Chen, Yen-Lane; Foss, Aaron; Huibregtse, Barbara; Dawkins, Keith D

    2015-11-15

    SYNERGY is a novel platinum chromium alloy stent that delivers abluminal everolimus from an ultrathin poly-lactide-co-glycide (PLGA) biodegradable polymer. This study evaluated the in vivo degradation of the polymer coating, everolimus release time course, and vascular compatibility of the SYNERGY stent. SYNERGY stents were implanted in arteries of domestic swine. Devices were explanted at predetermined time points (up to 120 days) and the extent of PLGA coating or everolimus remaining on the stents was quantified. Everolimus levels in the arterial tissue were also evaluated. A pathological analysis on coronary arteries of single and overlapping stents was performed at time points between 5 and 270 days. PLGA bioabsorption began immediately after implantation, and drug release was essentially complete by 90 days; PLGA absorption was substantially complete by 120 days (>90% of polymer was absorbed) leaving a bare metal SYNERGY stent. Vascular response was similar among SYNERGY and control stents (bare metal, polymer-only, and 3× polymer-only). Mild increases in para-strut fibrin were seen for SYNERGY at an early time point with no significant differences in all other morphological and morphometric parameters through 270 days or endothelial function (eNOS immunostaining) at 90 or 180 days. Inflammation was predominantly minimal to mild for all device types. In a swine model, everolimus was released by 90 days and PLGA bioabsorption was complete shortly thereafter. The SYNERGY stent and its biodegradable polymer, even at a 3× safety margin, demonstrated vascular compatibility similar to bare metal stent controls. © 2015 Wiley Periodicals, Inc.

  5. Compatibility studies of nevirapine in physical mixtures with excipients for oral HAART

    Oliveira, G.G.G. de; Ferraz, H.G. [Department of Pharmacy, Faculty of Pharmaceutical Health, University of Sao Paulo, Sao Paulo 05508-900 (Brazil); Severino, P. [Department of Biotechnological Processes, School of Chemical Engineering, University of Campinas, Campinas 13083-970 (Brazil); Department of Pharmaceutical Technology, Faculty of Health Sciences, Fernando Pessoa University, Porto 4200-150 (Portugal); Souto, E.B., E-mail: eliana@ufp.edu.pt [Department of Pharmaceutical Technology, Faculty of Health Sciences, Fernando Pessoa University, Porto 4200-150 (Portugal); Institute for Biotechnology and Bioengineering, Centre for Genomics and Biotechnology, University of Tras-os-Montes e Alto Douro (IBB-CGB/UTAD), 5001-801 Vila Real (Portugal)

    2013-03-01

    Nevirapine is a hydrophobic non-nucleoside reverse transcriptase inhibitor, used in first line regimens of highly active antiretroviral therapy (HAART). The drug has more than one crystalline form, which may have implications for its behaviour during production and also for its in vivo performance. This study was aimed at exploring the suitability of thermoanalytical methods for the solid-state characterization of commercial crystalline forms of nevirapine. The drug powder was characterized by ultraviolet spectrophotometry, stereoscopy, scanning electron microscopy, wide-angle X-ray diffraction, measurements of density, flowability, solubility and intrinsic dissolution rate (IDR), differential scanning calorimetry, thermogravimetric analysis, and photostability measurements. The results showed that nevirapine has high stability and is not susceptible to degradation under light exposure. The drug showed compatibility with the excipients tested (lactose, microcrystalline cellulose, polyvinylpyrrolidone and polyvinyl acetate copolymer (PVP/PVA), and hydroxypropylmethylcellulose (HPMC)). Nevirapine has low solubility, an acid medium being the most appropriate medium for assessing the release of the drug from dosage forms. However, the data obtained from IDR testing indicate that dissolution is the critical factor for the bioavailability of this drug. - Graphical abstract: Bulk nevirapine powder analysed by scanning electron microscopy and the drug solubility profile in various buffer solutions. The pH values of the media in which the tests were conducted are also presented. Highlights: Black-Right-Pointing-Pointer Nevirapine shows more than one crystalline form, that influence its in vivo and in vitro behaviour. Black-Right-Pointing-Pointer DSC and TGA were used for solid-state characterization of crystalline forms of nevirapine. Black-Right-Pointing-Pointer Nevirapine is compatible with lactose, microcrystalline cellulose, PVP/PVA copolymers and HPMC. Black

  6. Compatibility studies of nevirapine in physical mixtures with excipients for oral HAART

    Oliveira, G.G.G. de; Ferraz, H.G.; Severino, P.; Souto, E.B.

    2013-01-01

    Nevirapine is a hydrophobic non-nucleoside reverse transcriptase inhibitor, used in first line regimens of highly active antiretroviral therapy (HAART). The drug has more than one crystalline form, which may have implications for its behaviour during production and also for its in vivo performance. This study was aimed at exploring the suitability of thermoanalytical methods for the solid-state characterization of commercial crystalline forms of nevirapine. The drug powder was characterized by ultraviolet spectrophotometry, stereoscopy, scanning electron microscopy, wide-angle X-ray diffraction, measurements of density, flowability, solubility and intrinsic dissolution rate (IDR), differential scanning calorimetry, thermogravimetric analysis, and photostability measurements. The results showed that nevirapine has high stability and is not susceptible to degradation under light exposure. The drug showed compatibility with the excipients tested (lactose, microcrystalline cellulose, polyvinylpyrrolidone and polyvinyl acetate copolymer (PVP/PVA), and hydroxypropylmethylcellulose (HPMC)). Nevirapine has low solubility, an acid medium being the most appropriate medium for assessing the release of the drug from dosage forms. However, the data obtained from IDR testing indicate that dissolution is the critical factor for the bioavailability of this drug. - Graphical abstract: Bulk nevirapine powder analysed by scanning electron microscopy and the drug solubility profile in various buffer solutions. The pH values of the media in which the tests were conducted are also presented. Highlights: ► Nevirapine shows more than one crystalline form, that influence its in vivo and in vitro behaviour. ► DSC and TGA were used for solid-state characterization of crystalline forms of nevirapine. ► Nevirapine is compatible with lactose, microcrystalline cellulose, PVP/PVA copolymers and HPMC. ► The acid form of nevirapine is the most appropriate for assessing release profile from

  7. Neutron studies of liquid and solid helium: Progress report, May 1, 1987-April 30, 1988

    Glyde, H.R.

    1988-01-01

    Liquid and solid helium are prototype simple and solids displaying a wide spectrum of quantum properties. Understanding gained in these simple systems can be readily applied to more complicated materials. Neutron scattering studies carried out at DOE supported national facilities and the associated development of theory and models continue to reveal new physics in these facinating materials. During the past year we have measured the dynamic for factor, S(Q,ω), in superfluid and normal liquid 4 He accurately as a function of temperature. This shows that the sharp one-phonon excitation, which exists in the superfluid phase below T/sub lambda/, either disappears at or changes entirely in character at the transition to the normal phase. Thus the sharp one-phonon excitation can be associated with superfluidity (or a condensate). However, we find the weight of scattering in the one-phonon peak, Z(Q,T), is not porportional to the superfluid density, /rho//sub S/(T). We have also measured S(Q,ω) in the range 3 ≤ Q ≤ 15 /angstrom//sup /minus/1/ in order to obtain the width W(Q) and peak position, E(Q), of S(Q,ω) as a function of Q. We have made microscopic calculations of S(Q,ω) in the range 3 ≤ Q ≤ 15 /angstrom//sup /minus/1/ in both liquid 3 He and 4 He. The aim is a first principles evaluation of W(Q) and E(Q) as a function of Q for comparsion with experiments

  8. A Hartree–Fock study of the confined helium atom: Local and global basis set approaches

    Young, Toby D., E-mail: tyoung@ippt.pan.pl [Zakład Metod Komputerowych, Instytut Podstawowych Prolemów Techniki Polskiej Akademia Nauk, ul. Pawińskiego 5b, 02-106 Warszawa (Poland); Vargas, Rubicelia [Universidad Autónoma Metropolitana Iztapalapa, División de Ciencias Básicas e Ingenierías, Departamento de Química, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, D.F. C.P. 09340, México (Mexico); Garza, Jorge, E-mail: jgo@xanum.uam.mx [Universidad Autónoma Metropolitana Iztapalapa, División de Ciencias Básicas e Ingenierías, Departamento de Química, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, D.F. C.P. 09340, México (Mexico)

    2016-02-15

    Two different basis set methods are used to calculate atomic energy within Hartree–Fock theory. The first is a local basis set approach using high-order real-space finite elements and the second is a global basis set approach using modified Slater-type orbitals. These two approaches are applied to the confined helium atom and are compared by calculating one- and two-electron contributions to the total energy. As a measure of the quality of the electron density, the cusp condition is analyzed. - Highlights: • Two different basis set methods for atomic Hartree–Fock theory. • Galerkin finite element method and modified Slater-type orbitals. • Confined atom model (helium) under small-to-extreme confinement radii. • Detailed analysis of the electron wave-function and the cusp condition.

  9. Electronic properties of physisorbed helium

    Kossler, Sarah

    2011-01-01

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  10. Electronic properties of physisorbed helium

    Kossler, Sarah

    2011-09-22

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  11. A study of formation of iron nanoparticles in aluminium matrix with helium pores

    Kichanov, S.E.; Kozlenko, D. P.; Belushkin, A.V.; Reutov, V.F.; Samoilenko, S.O.; Jirák, Zdeněk; Savenko, B. N.; Bulavin, L. A.; Zubavichus, Y.V.

    2012-01-01

    Roč. 351, č. 1 (2012), "012013-1"-"012013-5" ISSN 1742-6588. [International Workshop on SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor - Devoted to the 75th anniversary of Yu M Ostanevich's Birth /2./. Dubna, 27.05.2011-30.05.2011] Institutional research plan: CEZ:AV0Z10100521 Keywords : iron nanoparticles * aluminium matrix * helium pores Subject RIV: BM - Solid Matter Physics ; Magnetism

  12. A Simulation Study for the Virtual Commissioning of the CERN Central Helium Liquefier

    Rogez, E; Moraux, A; Pezzetti, M; Gayet, P; Coppier, H

    2009-01-01

    This paper describes the implication of dynamic simulation in cryogenics processes. The simulation aims to prepare plant commissioning and operation, and to validate the efficiency of the new process control logic. PLC programs have been tested on a process simulator integrating physical models of valves, heat exchangers, turbines, phase separator, and helium data. The model has shown the capacity to reproduce cold-box dynamic behaviour, from 300 K to 4.5 K.

  13. Defects in TiN and HfN studied by helium thermal desorption spectrometry

    Hoondert, W.H.B.; Thijsse, B.J.; Beuckel, A. van den

    1994-01-01

    Point defects in sub-stoichiometric TiN 1-x and HfN 1-x were investigated by helium thermal desorption spectrometry (300-1800K) following He + ion implantation at energies up to 3000eV. It was found that the low energy spectra are dominated by helium dissociating from the structural vacancies on the nitrogen sublattice; the activation energy for dissociation is 2.2eV for TiN. Above a few hundred electron volts the ions begin to produce several other types of defects, from which helium dissociates with activation energies in the range 2.6-4.0eV. The identity of these defects is discussed. The results for the two nitrides were similar in many respects. The most significant difference observed is that in TiN low energy He + ions generate damage on the N sublattice of a type that is not observed for HfN. Activation energies for HfN are found to be consistently 0.7eV lower than for TiN. ((orig.))

  14. Compatibility Study of Protective Relaying in a Grid-Connected Fuel Cell

    Staunton, R.H.

    2004-04-15

    A 200-kW fuel cell produced by International Fuel Cells (IFC), a United Technologies Company, began operation at the National Transportation Research Center (NTRC) in early June 2003. The NTRC is a joint Oak Ridge National laboratory (ORNL) and University of Tennessee research facility located in Knoxville, Tennessee. This research activity investigated the protective relaying functions of this fully commercialized fuel cell power plant, which uses ''synthesized'' protective relays. The project's goal is to characterize the compatibility between the fuel cell's interconnection protection system and the local distribution system or electric power system (EPS). ORNL, with assistance from the Electric Power Research Institute-Power Electronics Applications Center (EPRI-PEAC) in Knoxville, Tennessee, monitored and characterized the system compatibility over a period of 6 months. Distribution utility engineers are distrustful of or simply uncomfortable with the protective relaying and hardware provided as part of distributed generation (DG) plants. Part of this mistrust is due to the fact that utilities generally rely on hardware from certain manufacturers whose reliability is well established based on performance over many years or even decades. Another source of concern is the fact that fuel cells and other types of DG do not use conventional relays but, instead, the protective functions of conventional relays are simulated by digital circuits in the distributed generator's grid interface control unit. Furthermore, the testing and validation of internal protection circuits of DG are difficult to accomplish and can be changed by the vendor at any time. This study investigated and documented the safety and protective relaying present in the IFC fuel cell, collected data on the operation of the fuel cell, recorded event data during EPS disturbances, and assessed the compatibility of the synthesized protective circuits and the local

  15. A Study on the Compatibility of 3-D Seismic Velocity Structures with Gravity Data of Taiwan

    Horng-Yuan Yen Hsien-Hsiang Hsieh

    2010-01-01

    Full Text Available The Bouguer anomaly of Taiwan has been revised in this study based on more accurate terrain data provided by the Taiwanese Digital Terrain Model compiled by the Taiwan Forestry Bureau. Three seismic velocity models, those determined by Rau and Wu (1995, Kim et al. (2005, and Wu et al. (2007 respectively, were selected for our study. We converted their velocity models to density models using the relationship between P-wave velocity and rock density proposed by Ludwig et al. (1970 and Barton (1986, and then calculated their corresponding gravity anomalies. According to the correlation coefficient between the Bouguer anomalies calculated from the velocity models and the revised Bouguer anomalies, the Kim et al. model was more compatible with gravity data than the other two velocity models. The differences between the revised gravity anomaly and the calculated gravity anomalies trend toward positive values at elevations higher than 2000 m. This indicates that the velocities at the shallower depths beneath the mountainous area of the three models are overdetermined, i.e., higher than the real velocities. This ratiocination implies that the crustal thickness beneath the Central Range is less than 55 km which was obtained from the velocity models.

  16. Microbiological studies to select compatible rhizobia for application in wastelands using molecular and nuclear techniques

    Abdel Raouf, A.M.N

    2010-01-01

    The present work aimed at utilization of wastelands and improving their fertility status through the following topics:1- Isolation and identification of rhizobia from wastelands, then selecting the most resistant isolate to saline conditions.2- Studying the effect of radiation on the most salt tolerant rhizobia and marketing rhizobia using molecular and microbiological techniques.3- Identification and culturing of selected compatible rhizobia to be used in application experiments as a bio fertilizer to inoculate the leguminous crops in order to improve the efficiency of the Rhizobium-legume symbiosis and reclamation of wastelands.4- Application of molecular and nuclear techniques such 16S ribosomal RNA and studying the sequence for these strains for comparison between the most potent rhizobia.5- Determination of protein profile for the most potent rhizobia to throw light about similarities between these strains.6- Attempts to apply polymerase chain reaction (PCR) and use primers for differentiation between the most potent rhizobia.7- Experimental fields for growing some leguminous plants inoculated with irradiated and non-irradiated rhizobia and irrigated with different concentrations of sea water and their effects on growth and total N content of plants.

  17. In vivo study of rat cortical hemodynamics using a stereotaxic-apparatus-compatible photoacoustic microscope.

    Guo, Heng; Chen, Qian; Qi, Weizhi; Chen, Xingxing; Xi, Lei

    2018-04-19

    Brain imaging is an important technique in cognitive neuroscience. In this article, we designed a stereotaxic-apparatus-compatible photoacoustic microscope for the studies of rat cortical hemodynamics. Compared with existing optical resolution photoacoustic microscopy (ORPAM) systems, the probe owns feature of fast, light and miniature. In this microscope, we integrated a miniaturized ultrasound transducer with a center frequency of 10 MHz to detect photoacoustic signals and a 2-dimensional (2D) microelectromechanical system (MEMS) scanner to achieve raster scanning of the optical focus. Based on phantom evaluation, this imaging probe has a high lateral resolution of 3.8 μm and an effective imaging domain of 2 × 2 mm 2 . Different from conventional ORPAMs, combining with standard stereotaxic apparatus enables broad studies of rodent brains without any motion artifact. To show its capability, we successfully captured red blood cell flow in the capillary, monitored the vascular changes during bleeding and blood infusion and visualized cortical hemodynamics induced by middle cerebral artery occlusion. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies.

    Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus; Hansen, Steen Honoré

    2015-05-15

    Microwave ovens have been used extensively in organic synthesis in order to accelerate reaction rates. Here, a set up comprising a microwave oven combined with silicon carbide (SiC) plates for the controlled microwave heating of model formulations has been applied in order to investigate, if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. In the accelerated stability studies, a design of experiments (DoE) approach was applied in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating leading to temperatures between 150°C and 180°C as compared to accelerated stability studies performed at 40°C and 80°C using a conventional oven. Ranking of the reactivity of the excipients could be made in the DoE studies performed at 150-180°C, which was representative for the ranking obtained after storage at 40°C and 80°C. It was possible to reduce the time needed for drug-excipient compatibility testing of the three model formulations from weeks to less than an hour in the three case studies. The microwave oven is therefore considered to be an interesting alternative to conventional thermal techniques for the investigation of drug-excipient interactions during preformulation. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Stimulus-Response Compatibility effect in the near-far dimension: A developmental study

    Aurélien Richez

    2016-08-01

    Full Text Available The present study investigates the developmental aspect of stimulus-response compatibility effect in 8 to 11-years-old children. The task consisted in manually responding to the colour of a pawn presented on a chessboard at different distances. Manual responses were provided by reaching a proximal or distal location depending on the colour of the stimulus. We found that reaction time was affected by the conflict generated by the response suggested by the location of the stimulus and the response required according to its colour. This was not the case for movement time despite we found a higher rate of long duration movements in the incongruent than in the congruent spatial condition. The SRC effect was however observed in children older than 10 years old. These findings provide additional evidence for a reorganization of the perceptual system during the period of 8 to 10 years, integrating progressively multimodal information and preparing more efficiently the body to act in the environment.

  20. Biodiesel feasibility study: An evaluation of material compatibility; performance; emission and engine durability

    Fazal, M.A.; Haseeb, A.S.M.A.; Masjuki, H.H. [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2011-02-15

    Biodiesel, derived from the transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long-chain fatty acid alkyl esters. In spite of having some application problems, recently it is being considered as one of the most promising alternative fuels in internal combustion engine. From scientific literatures, this paper has collected and analyzed the data on both advantages and disadvantages of biodiesel over conventional diesel. Since the aim of this study is to evaluate the biodiesel feasibility in automobiles, the first section is dedicated to materials compatibility in biodiesel as compared to that in diesel. The highest consensus is related to enhanced corrosion of automotive parts due to its compositional differences. In the subsequent sections, data on performance, emission and engine durability have been analyzed and compared. In this case, the highest consensus is found in reducing emissions as well as in increasing moving parts sticking, injector coking and filter plugging. This paper has also summarized the factors of biodiesel in contributing these technical performances. (author)

  1. Chemical compatibility study between ceramic breeder and EUROFER97 steel for HCPB-DEMO blanket

    Mukai, Keisuke, E-mail: keisuke.mukai@kit.edu [Institute for Applied Materials (IAM), Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Sanchez, Fernando [National Fusion Laboratory, Division of Fusion Technology, CIEMAT, 28040 Madrid (Spain); Knitter, Regina [Institute for Applied Materials (IAM), Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany)

    2017-05-15

    Chemical compatibility between ceramic breeder (Li{sub 4}SiO{sub 4} + 20 mol% addition of Li{sub 2}TiO{sub 3}) and EUROFER97 steel was examined in this study. These materials were contacted and heated at 623, 823 and 1073 K under He + 0.1 vol.% H{sub 2} atmosphere for up to 12 weeks. Limited influence was found in the breeder specimens, although losses of the constituent elements appeared near the surface of the breeder pellets heated at 1073 K. For the EUROFER specimens with formation of a corrosion layer, element diffusivity was estimated based on diffusion kinetics. In the temperature range, effective diffusion coefficients of oxygen into EUROFER steel were in the range from 3.5 × 10{sup −134} to 2.5 × 10{sup −112} cm/s{sup 2} and found to be faster than that of Li. The coefficients yielded an activation energy of 0.93 eV for oxygen diffusion into EUROFER steel and predicted the possible thickness of the corrosion layer after operational periods.

  2. Studies on in vitro biostability and blood compatibility of polyurethane potting compound based on aromatic polymeric MDI for extracorporeal devices.

    Hridya, V K; Jayabalan, M

    2009-12-01

    Polyurethane potting compound based on aromatic isocyanurate of polymeric MDI, poly propylene glycol (PPG400) and trimethylol propane (TMP) has significant favourable properties, good pot life and setting characteristics. The cured potting compound of this formulation has appreciable thermal stability and mechanical properties. In vitro biostability of cured potting compound has been found to be excellent without any significant degradation in simulated physiological media and chemical environment. Studies on blood-material interaction and cytotoxicity reveal in vitro blood compatibility and compatibility with cells of this potting compound.

  3. Molecular dynamics study of the role of symmetric tilt grain boundaries on the helium distribution in nickel

    Torres, E.; Pencer, J.

    2018-04-01

    Helium impurities, from either direct implantation or transmutation reactions, have been associated with embrittlement in nickel-based alloys. Helium has very low solubility in nickel, and has been found to aggregate at lattice defects such as vacancies, dislocations, and grain boundaries. The retention and precipitation of helium in nickel-based alloys have deleterious effects on the material mechanical properties. However, the underlying mechanisms that lead to helium effects in the host metal are not fully understood. In the present work, we investigate the role of symmetric tilt grain boundary (STGB) structures on the distribution of helium in nickel using molecular dynamics simulations. We investigate the family of STGBs specific to the 〈 110 〉 tilt axis. The present results indicate that accumulation of helium at the grain boundary may be modulated by details of grain boundary geometry. A plausible correlation between the grain boundary energy and misorientation with the accumulation and mobility of helium is proposed. Small clusters with up to 6 helium atoms show significant interstitial mobility in the nickel bulk, but also become sites for nucleation and grow of more stable helium clusters. High-energy GBs are found mainly populated with small helium clusters. The high mobility of small clusters along the GBs indicates the role of these GBs as fast two-dimensional channels for diffusion. In contrast, the accumulation of helium in large helium clusters at low-energy STGB creates a favorable environment for the formation of large helium bubbles, indicating a potential role for low-energy STGB in promoting helium-induced GB embrittlement.

  4. Calcium Chloride and Calcium Gluconate in Neonatal Parenteral Nutrition Solutions without Cysteine: Compatibility Studies Using Laser Light Obscuration Methodology

    Robert K. Huston

    2018-02-01

    Full Text Available There are no compatibility studies for neonatal parenteral nutrition solutions without cysteine containing calcium chloride or calcium gluconate using light obscuration as recommended by the United States Pharmacopeia (USP. The purpose of this study was to do compatibility testing for solutions containing calcium chloride and calcium gluconate without cysteine. Solutions of TrophAmine and Premasol (2.5% amino acids, containing calcium chloride or calcium gluconate were compounded without cysteine. Solutions were analyzed for particle counts using light obscuration. Maximum concentrations tested were 15 mmol/L of calcium and 12.5 mmol/L of phosphate. If the average particle count of three replicates exceeded USP guidelines, the solution was determined to be incompatible. This study found that 12.5 and 10 mmol/L of calcium and phosphate, respectively, are compatible in neonatal parenteral nutrition solutions compounded with 2.5% amino acids of either TrophAmine or Premasol. There did not appear to be significant differences in compatibility for solutions containing TrophAmine or Premasol when solutions were compounded with either CaCl2 or CaGlu-Pl. This study presents data in order to evaluate options for adding calcium and phosphate to neonatal parenteral nutrition solutions during shortages of calcium and cysteine.

  5. Helium cooling of fusion reactors

    Wong, C.P.C.; Baxi, C.; Bourque, R.; Dahms, C.; Inamati, S.; Ryder, R.; Sager, G.; Schleicher, R.

    1994-01-01

    On the basis of worldwide design experience and in coordination with the evolution of the International Thermonuclear Experimental Reactor (ITER) program, the application of helium as a coolant for fusion appears to be at the verge of a transition from conceptual design to engineering development. This paper presents a review of the use of helium as the coolant for fusion reactor blanket and divertor designs. The concept of a high-pressure helium cooling radial plate design was studied for both ITER and PULSAR. These designs can resolve many engineering issues, and can help with reaching the goals of low activation and high performance designs. The combination of helium cooling, advanced low-activation materials, and gas turbine technology may permit high thermal efficiency and reduced costs, resulting in the environmental advantages and competitive economics required to make fusion a 21st century power source. ((orig.))

  6. First principles study of inert-gas (helium, neon, and argon) interactions with hydrogen in tungsten

    Kong, Xiang-Shan [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China); Hou, Jie [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Li, Xiang-Yan [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China); Wu, Xuebang, E-mail: xbwu@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China); Liu, C.S., E-mail: csliu@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China); Chen, Jun-Ling; Luo, G.-N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2017-04-15

    We have systematically evaluated binding energies of hydrogen with inert-gas (helium, neon, and argon) defects, including interstitial clusters and vacancy-inert-gas complexes, and their stable configurations using first-principles calculations. Our calculations show that these inert-gas defects have large positive binding energies with hydrogen, 0.4–1.1 eV, 0.7–1.0 eV, and 0.6–0.8 eV for helium, neon, and argon, respectively. This indicates that these inert-gas defects can act as traps for hydrogen in tungsten, and impede or interrupt the diffusion of hydrogen in tungsten, which supports the discussion on the influence of inert-gas on hydrogen retention in recent experimental literature. The interaction between these inert-gas defects and hydrogen can be understood by the attractive interaction due to the distortion of the lattice structure induced by inert-gas defects, the intrinsic repulsive interaction between inert-gas atoms and hydrogen, and the hydrogen-hydrogen repelling in tungsten lattice.

  7. A numerical study of shock-acceleration of a diffuse helium cylinder. Revision 1

    Greenough, J.A.; Jacobs, J.W.

    1995-08-01

    The development of a shock-accelerated diffuse Helium cylindrical inhomogeneity is investigated using a new numerical method. The new algorithm is a higher-order Godunov implementation of the so-called multi-fluid equations. This system correctly models multiple component mixtures by accounting for differential compressibility effects. This base integrator is embedded in an implementation of adaptive mesh refinement (AMR) that allows efficient increase in resolution by concentrating the computational effort where high accuracy, or increased resolution, are required. Qualitative and quantitative comparison with previous experimental data is excellent. The simulations show that counter-sign vortex blobs are deposited in the jet core by baroclinic generation of the curved shock wave as it traverses the jet. This vorticity deposition occurs over timescales that scale with the shock passage time (∼ 10microsec). Three phases of development are identified and characterized. The first is the weak deformation (WD) phase, where there is weak distortion of the Helium jet due to weak vorticity induced velocity effects. The second phase is the strong deformation (SD) phase where there is large distortion for the jet and the vortex blobs due to large induced velocity effects. The last is a relaxation/reorganization (RR) phase where the vorticity field is reorganized into point-like vortex pair. This class of problem has applications in such disparate fields as inertial confinement fusion (ICF) and high-speed combustion

  8. A numerical study of shock-acceleration of a diffuse helium cylinder

    Greenough, J.A.; Bell, J.; Colella, P.

    1995-08-01

    The development of a shock-accelerated diffuse Helium cylindrical inhomogeneity is investigated using a new numerical method. The new algorithm is a higher-order Godunov implementation of the so-called multi-fluid equations. This system correctly models multiple component mixtures by accounting for differential compressibility effects. This base integrator is embedded in an implementation of adaptive mesh refinement (AMR) that allows efficient increase in resolution where the computational effort is concentrated where high accuracy, or increased resolution, are required. Qualitative and quantitative comparison with previous experimental data is excellent. The simulations show that counter-sign vortex blobs are deposited in the jet core by baroclinic generation of the curved shock wave as it traverses the jet. This vorticity deposition occurs over timescales that scale with the shock passage time (∼ 10μsec). Three phases of development are identified and characterized. The first is the weak deformation (WD) phase, where there is weak distortion of the Helium jet due to weak vorticity induced velocity effects. The second phase is the strong deformation (SD) phase where there is large distortion for the jet and the vortex blobs due to large induced velocity effects. The last is a relaxation/reorganization (RR) phase where the vorticity field reorganizes into point-like vortex pair

  9. Visualization study of helium-air counter flow through a small opening

    Fumizawa, Motoo

    2007-01-01

    Buoyancy-driven counter flows of helium-air were investigated through horizontal and inclined small openings. Counter flows may occur following a window opening as ventilation, fire in the room as well as a pipe rupture accident in a high temperature gas-cooled nuclear reactor. The experiment has carried out by a test chamber filled with helium and flow was visualized by the smoke wire method. The flow behavior has recorded by a high-speed camera with a computer system. The image of the flow was transferred to the digital data, thus the flow velocity was measured by PTV software. The mass fraction in the test chamber was measured by electronic balance. The detected data was arranged by the densimetric Floude number of the counter flow rate that derived from the dimensional analysis. The method of mass increment was developed and applied to measure the counter flow rate. By removing the cover plate placed on the top of the opening, the counter flow initiated. Air enters the test chamber and the mass of the gas mixture in the test chamber increased. The volumetric counter flow rate was evaluated from the mass increment data. In the case of inclination openings, the results of both methods were compared. The inclination angle for maximum densimetric Floude number decreased with increasing length-to-diameter ratio of the opening. For a horizontal opening, the results from the method of mass increment agreed with those obtained by other authors for a water-brine system. (author)

  10. The Compatibility of Feminist Theology and Gestalt Therapy: A Study of "Practical-Values."

    Hinksman, Barrie

    2001-01-01

    An on-going theoretical issue for pastoral counseling concerns the integration of psychological and theological concepts. The possibility of exploring the compatibility of Gestalt psychotherapy and feminist theology is considered with reference to the 'practical-values' of each, and it is proposed that there is significant common ground between…

  11. Helium in inert matrix dispersion fuels

    Veen, A. van; Konings, R.J.M.; Fedorov, A.V.

    2003-01-01

    The behaviour of helium, an important decay product in the transmutation chains of actinides, in dispersion-type inert matrix fuels is discussed. A phenomenological description of its accumulation and release in CERCER and CERMET fuel is given. A summary of recent He-implantation studies with inert matrix metal oxides (ZrO 2 , MgAl 2 O 4 , MgO and Al 2 O 3 ) is presented. A general picture is that for high helium concentrations helium and vacancy defects form helium clusters which convert into over-pressurized bubbles. At elevated temperature helium is released from the bubbles. On some occasions thermal stable nano-cavities or nano-pores remain. On the basis of these results the consequences for helium induced swelling and helium storage in oxide matrices kept at 800-1000 deg. C will be discussed. In addition, results of He-implantation studies for metal matrices (W, Mo, Nb and V alloys) will be presented. Introduction of helium in metals at elevated temperatures leads to clustering of helium to bubbles. When operational temperatures are higher than 0.5 melting temperature, swelling and helium embrittlement might occur

  12. Antiprotonic helium atomcules

    Sauge Sébastien

    2012-10-01

    Full Text Available About 3% of antiprotons ( stopped in helium are long-lived with microsecond lifetimes, against picoseconds in all other materials. This unusual longevity has been ascribed to the trapping of on metastable bound states in He+ helium atom-molecules thus named atomcules. Apart from their unique dual structure investigated by laser spectroscopy – a near-circular quasi-classical Rydberg atom with l ~ n – 1 ~ 37 or a special diatomic molecule with a negatively charged nucleus in high rotational state with J = l – the chemical physics aspects of their interaction with other atoms or molecules constitute an interesting topic for molecular physics. While atomcules may resist to million collisions in helium, molecular contaminants such as H2 are likely to destroy them in a single one, down to very low temperatures. In the Born-Oppenheimer framework, we interpret the molecular interaction obtained by ab initio quantum chemical calculations in terms of classical reactive channels, with activation barriers accounting for the experiments carried out in He and H2. From classical trajectory Monte Carlo simulations, we show that the thermalization stage strongly quenches initial populations, thus reduced to a recovered 3 % trapping fraction. This work illustrates the pertinence of chemical physics concepts to the study of exotic processes involving antimatter. New insights into the physico-chemistry of cold interstellar radicals are anticipated.

  13. First-principles study of helium clustering at initial stage in ThO2

    Shao Kuan; Han Han; Zhang Wei; Wang Chang-Ying; Guo Yong-Liang; Ren Cui-Lan; Huai Ping

    2017-01-01

    The clustering behavior of helium atoms in thorium dioxide has been investigated by first-principles calculations. The results show that He atoms tend to form a cluster around an octahedral interstitial site (OIS). As the concentration of He atoms in ThO 2 increases, the strain induced by the He atoms increases and the octahedral interstitial site is not large enough to accommodate a large cluster, such as a He hexamer. We considered three different Schottky defect (SD) configurations (SD 1 , SD 2 , and SD 3 . When He atoms are located in the SD sites, the strain induced by the He atoms is released and the incorporation and binding energies decrease. The He trimer is the most stable cluster in SD 1 . Large He clusters, such as a He hexamer, are also stable in the SDs. (paper)

  14. Experimental study of the density of the helium-nitrogen gas system at low temperatures.

    Milyutin, V. A.

    2017-11-01

    At the Department of TOT, an experimental setup was created to measure the density of a binary gas system from 100 to 300 K and pressures up to 16 MPa and with any mixture compositions. Experimental density for the helium-nitrogen system were determined by the piezometer of constant volume method. The amount of substance in the piezometer was measured by volumetric method. In this setup, the mixture of He - N2 was prepared in a special mixer for a series of p-v-T experiments, the concentration was determined by calculation using the equations of state of pure components. In the experiment, mixtures were prepared with molar concentrations, lying close to the range: 0.2, 0.4, 0.6 and 0.8.

  15. First-Principles Molecular Dynamics Study on Helium- filled Carbon Nanotube

    Agusta, M K; Prasetiyo, I; Saputro, A G; Dipojono, H K; Maezono, R

    2016-01-01

    Investigation on carbon nanotube (CNT) filled by Helium (He) atoms is conducted using Density Functional Theory and Molecular Dynamics Simulation. It reveals that He atom is repelled by CNT's wall and find its stable position at the tube center. Vibrational analysis on modes corespond to radial inward and outward breathing movement of CNT shows that He filling tends to pull the CNT wall in inward direction. Furthermore, examination on C-C stretch mode reveals that the existence of He improve the stiffness of CNT's wall. Molecular dynamics calculations which are done on (3,3) and (5,5) nanotube with 0.25 gr/cm 3 and 0.5 gr/cm 3 He density at 300 K and 1500 K confirms the increase of stiffness of CNT wall by interaction with He atoms. Effects of variation of chirality, temperature and He density on CNT wall stiffness is also reported. (paper)

  16. Particle balance studies in TEXTOR during experiments of pellet injection, helium injection, and ICR-heating

    Banno, T.; Finken, K.H.; Gray, D.S.; Winter, J.

    1995-01-01

    Analysis based on the particle conservation law has been carried out to observe the global fuelling process in tokamak discharges. The response of the net recycling flux from the first wall is investigated in the tokamak TEXTOR, using calibrated signals of the gas feed rate, the neutral gas pressure in the vessel, the total amount of electrons, and the particle removal rates by the ALT-II belt-pump limiter and by a main pump unit. Net absorption (pumping) of hydrogen by the wall is observed for almost all tokamak discharges since a new wall conditioning technique called siliconisation is employed. The net absorption or fuelling depending on the discharge condition influenced by injection of pellets, by helium gas injection combined with neutral beam injection, and by rf heating can be interpreted in terms of the particle-induced desorption effect with depth profile taken into consideration. ((orig.))

  17. Study on blood compatibility of the radiation sterilized disposable burette transfusion apparatus

    Chen Guochong; Liu Wen; Liu Qingfang

    2011-01-01

    The blood compatibility of the radiation sterilized disposable burette transfusion apparatus was investigated to provide evidence for the safety of radiation sterilized medical devices. The initial bacteria burden of the disposable burette transfusion apparatus was examined according to the ISO11737 standard, and the whole blood clotting time, prothrombin time, partial thromboplastin time and hemolysis rate of the samples were determined. There was no significant difference between the radiation sterilized samples and negative controls on WBCT, PT and PTT (p>0.05). Haemolysis test showed that the haemolysis rate of the sample sterilized by irradiation was 1.38%, which was coincidence with the criteria of the medical devices. After sterilization by irradiation, disposable burette transfusion apparatus show good blood compatibility, which could be considered that radiation sterilization is a biologically safe method for the medical apparatus. (authors)

  18. Dopant-induced ignition of helium nanoplasmas—a mechanistic study

    Heidenreich, Andreas; Schomas, Dominik; Mudrich, Marcel

    2017-12-01

    Helium (He) nanodroplets irradiated by intense near-infrared laser pulses form a nanoplasma by avalanche-like electron impact ionizations (EIIs) even at lower laser intensities where He is not directly field ionized, provided that the droplets contain a few dopant atoms which provide seed electrons for the EII avalanche. In this theoretical paper on calcium and xenon doped He droplets we elucidate the mechanism which induces ionization avalanches, termed ignition. We find that the partial loss of seed electrons from the activated droplets starkly assists ignition, as the Coulomb barrier for ionization of helium is lowered by the electric field of the dopant cations, and this deshielding of the cation charges enhances their electric field. In addition, the dopant ions assist the acceleration of the seed electrons (slingshot effect) by the laser field, supporting EIIs of He and also causing electron loss by catapulting electrons away. The dopants’ ability to lower the Coulomb barriers at He as well as the slingshot effect decrease with the spatial expansion of the dopant, causing a dependence of the dopants’ ignition capability on the dopant mass. Here, we develop criteria (impact count functions) to assess the ignition capability of dopants, based on (i) the spatial overlap of the seed electron cloud with the He atoms and (ii) the overlap of their kinetic energy distribution with the distribution of Coulomb barrier heights at He. The relatively long time delays between the instants of dopant ionization and ignition (incubation times) for calcium doped droplets are determined to a large extent by the time it takes to deshield the dopant ions.

  19. Advanced Valve Technology. Volume 2. Materials Compatibility and Liquid Propellant Study

    1967-11-01

    the other 300 series stainless steels. Table 1-2 lists those materials considered to be compatible with hydrazine for long-term application. PHYSICAL...Lubricity (1) - Unsatisfactory lubricating performance was found for hydrazine in a series of low-load short duration ball bearing and gear tests at...Continued) MATERIALS TEST TEMP OF CERPAM ICS Rockflux 75 Sauereisen P-i 60 Sauereisen 31 60 Temporall 1500 60 ADHE SI VES Epon 422 80 1-33 PENTABORANE

  20. Liquid helium target

    Fujii, Y.; Kitami, T.; Torikoshi, M.

    1984-12-01

    A liquid helium target system has been built and used for the experiment on the reaction 4 He(γ, p). The target system has worked satisfactorily; the consumption rate of liquid helium is 360 ml/h and the cryogenic system retains liquid helium for about ten hours. The structure, operation and performance of the target system are reported. (author)

  1. COMPATIBILITY STUDIES OF INTERSPECIFIC IN VITRO MICROGRAFTING OF AGARWOOD ( Aquilaria malaccensis LAMK.

    NURITA TORUAN-MATHIUS

    2008-01-01

    Full Text Available Aquilaria spp produced agarwood as nonwood forest production, and has high economic value. A. malaccensis is susceptible to white rot diseases and termites. On the other hand most of the community plantations are a mixed culture with rubber trees, oil palms and with high risk of con-tamination causing white root diseases. Besides that, vegetative propagation by cuttings, stumping or air layering are still very diffi cult with low percentage of growth. h e objectives of this research were to analyze the best suitable micrograft type, changes of SDS-PAGE protein band patterns of compatible and incompatible micrografts with several combinations of gaharu planlets in in vitro condition, and histology of union area between rootstocks and scion. h e results showed that wedge or V type was the best of the micrografs. MS medium with the addition of 3 mg/L IBA was the best medium for gaharu planlet growth after micrografting. Acclimatization was conducted in husk chacoal and top soil (1:1 medium and grown under plastic house of 70% shading with paranet. Compatible combination (Ac/Am of micrografting showed that anatomy structure of union area is the same as anatomy structure of non micrograftd planlet. While incompatible (Gv/Am mi-crografting produced necrotic layer growth from pith and parenchymateous tissues of the wood in union area along the middle of radial shoot. Recovery period of union area between stocks and scion is initiated by callus formation from the pith and parenchymatous tissues of the wood. Callus will diff erentiate into mature cells or tissue and become combined phloem and xylem vessels be-tween rootstocks and scion. SDS-PAGE protein band pattern on compatible combination was the same as plants originated from seedlings. While, incompatible combination produced new protein bands with molecular weight around 21 and 30 kD.

  2. Comparative study of electromagnetic compatibility methods in printed circuit board design tools

    Marinova, Galia

    2002-01-01

    The paper considers the state-of-the art in electromagnetic compatibility (EMC) oriented printed circuit board (PCB) design. A general methodology of EMC oriented PCB design is synthesized. The main CAD tools available today are estimated and compared for their abilities to treat EMC oriented design. To help non experts a knowledge-base containing more than 50 basic rules for EMC-oriented PCB design is proposed. It can be applied in the PCB design CAD tools that possess rule-builders or it can help interactive design. Trends in this area of EMC-oriented PCB design are deduced. (Author)

  3. The relation between task characteristics, BI quality and task compatibility: An explorative study

    Gaardboe, Rikke; Jonasen, Tanja Svarre; Nyvang, Tom

    2018-01-01

    The purpose of this article is to investigate the relationship between task characteristics, business intelligence (BI) quality, and task compatibility. It is essential to investigate this relationship, as BI often builds up data from the organization's existing information systems, and thus......, is a supplement. In addition, there is a gap within existing research about task characteristics and BI. We conducted a survey of three companies, where 104 BI end users answered the questionnaire. Our findings reveal that BI users who experience high information quality solve difficult tasks, have a specified...

  4. Study on mechanical properties of the laminated composite materials with compatible heat treatments

    Pashkov, P.O.; Pektemirov, B.G.; Yaroshenko, A.P.

    1980-01-01

    Considered is the behaviour during axial extension of trilament composite materials, the mechanical properties of which are formed mainly by heat treatment. Application in the composite of the materials with compatible heat treatment is most rational. It is shown that for (ATsMg+N18K8M5T+ATsMg), (KhN78+VKS+KhH78) composites, the constituents of which are relatively plastic and tightly bound with each other, the tensile strength and uniform strain are changed additively

  5. Performance of ventilators compatible with magnetic resonance imaging: a bench study.

    Chikata, Yusuke; Okuda, Nao; Izawa, Masayo; Onodera, Mutsuo; Nishimura, Masaji

    2015-03-01

    Magnetic resonance imaging (MRI) is indispensable for diagnosing brain and spinal cord abnormalities. Magnetic components cannot be used during MRI procedures; therefore, patient support equipment must use MRI-compatible materials. However, little is known of the performance of MRI-compatible ventilators. At commonly used settings, we tested the delivered tidal volume (V(T)), F(IO2), PEEP, and operation of the high-inspiratory-pressure-relief valves of 4 portable MRI-compatible ventilators (Pneupac VR1, ParaPAC 200DMRI, CAREvent MRI, iVent201) and one ICU ventilator (Servo-i). Each ventilator was set in volume control/continuous mandatory ventilation mode. Breathing frequency and V(T) were tested at 10 breaths/min and 300, 500, and 700 mL, respectively. The Pneupac VR1 has fixed V(T) and frequency combinations, so it was tested at V(T) = 300 mL and 20 breaths/min, V(T) = 500 mL and 12 breaths/min, and V(T) = 800 mL and 10 breaths/min. F(IO2) was 0.6 and 1.0. At the air-mix setting, F(IO2) was fixed at 0.5 with the Pneupac VR1, 0.45 with the ParaPAC 200DMRI, and 0.6 with the CAREvent MRI. PEEP was set at 5 and 10 cm H2O, and pressure relief was set at 30 and 40 cm H2O. V(T) error varied widely among ventilators (-28.1 to 25.5%). As V(T) increased, error decreased with the Pneupac VR1, ParaPAC 200DMRI, and CAREvent MRI (P ventilators (-29.2 to 42.5%). Only the Servo-i maintained V(T), F(IO2), and PEEP at set levels. The pressure-relief valves worked in all ventilators. None of the MRI-compatible ventilators maintained V(T), F(IO2), and PEEP at set levels. Vital signs of patients with unstable respiratory mechanics should be monitored during transport and MRI. Copyright © 2015 by Daedalus Enterprises.

  6. Behaviour of helium after implantation in molybdenum

    Viaud, C.; Maillard, S.; Carlot, G.; Valot, C.; Gilabert, E.; Sauvage, T.; Peaucelle, C.; Moncoffre, N.

    2009-01-01

    This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature

  7. Study of steam, helium and supercritical CO2 turbine power generations in prototype fusion power reactor

    Ishiyama, Shintaro; Muto, Yasushi; Kato, Yasuyoshi; Nishio, Satoshi; Hayashi, Takumi; Nomoto, Yasunobu

    2008-01-01

    Power generation systems such as steam turbine cycle, helium turbine cycle and supercritical CO 2 (S-CO 2 ) turbine cycle are examined for the prototype nuclear fusion reactor. Their achievable cycle thermal efficiencies are revealed to be 40%, 34% and 42% levels for the heat source outlet coolant temperature of 480degC, respectively, if no other restriction is imposed. In the current technology, however, low temperature divertor heat source is included. In this actual case, the steam turbine system and the S-CO 2 turbine system were compared in the light of cycle efficiency and plant cost. The values of cycle efficiency were 37.7% and 36.4% for the steam cycle and S-CO 2 cycle, respectively. The construction cost was estimated by means of component volume. The volume became 16,590 m 3 and 7240 m 3 for the steam turbine system and S-CO 2 turbine system, respectively. In addition, separation of permeated tritium from the coolant is much easier in S-CO 2 than in H 2 O. Therefore, the S-CO 2 turbine system is recommended to the fusion reactor system than the steam turbine system. (author)

  8. Experimental study of the critical density of heat flux in open channels cooled with helium - II

    Pron'ko, V.G.; Gorokhov, V.V.; Saverin, V.N.

    1981-01-01

    Experimental values of the critical density of a heat flux qsub(cr) in uniformly heated open channels cooled with helium-2 are reported for the first time. The experimental test bench and experimental element are described. Experimental data are obtained in cylindrical channels of 12Kh18N1OT steel with inner diameter d=0.8, 1.8; 2.8 mm and ratio l/d=20.8, 44, 85. The channel orientation has varied from vertical to horizontal position, the immersion depth - from 100, to 600 mm. It has been found that the heat transfer crisis propagation over the whole length of the channel with He-2 occurs practically instantaneously. The qsub(cr) value depends essentially on the bath liquid temperature, angle of inclivnation and relative length (l/d) of the channel with qsub(cr) approximately (l/d)sup(-1.5) being independent of the depth of channel immersion. The obtained values of critical density of a heat flux in channels are papproximately by an order less than those found for a great bulk of He-2. The results presented may be used for designing various types of devices cooled with He-2 and development of heat exchange theory in it [ru

  9. QM/MM study of dislocation—hydrogen/helium interactions in α-Fe

    Zhao, Yi; Lu, Gang

    2011-01-01

    Impurities such as hydrogen (H) and helium (He) interact strongly with dislocations in metals. Using a multiscale quantum-mechanics/molecular-mechanics (QM/MM) approach, we have examined the interactions between the impurities (H and He) with dislocations (edge and screw) in α-Fe. The impurity trapping at the dislocation core is examined by calculating the impurity-dislocation binding energy and the impurity solution energy. We find that in general both H and He prefer the tetrahedral sites at the dislocation core, as well as in the bulk; the exceptions are due to deformed structures at the dislocation cores. Both H and He have a greater solution energy and binding energy to the edge dislocation than to the screw dislocation. The impurity pipe diffusion along the dislocation core is investigated using the QM/MM nudged-elastic-band method. We find that the diffusion barrier along the screw dislocation is lower than the bulk value for both H and He impurities. For the edge dislocation, although H has similar diffusion barriers as in the bulk, He has much higher diffusion energy barriers compared with the bulk. Finally we have examined the impurity effect on the dislocation mobility. We find that both H and He can lower the Peierls energy barrier for the screw dislocation significantly. The H enhanced dislocation mobility is consistent with experimental observations

  10. A materials compatibility study in FM-1, a liquid component of a paste extrudable explosive

    Goods, S.H.; Shepodd, T.J.; Mills, B.E. [Sandia National Labs., Livermore, CA (United States); Foster, P. [Mason and Hanger-Silas Mason Co., Inc., Amarillo, TX (United States). Pantex Plant

    1993-09-01

    The chemical compatibility of various metallic and organic containment materials with a constituent of a paste extrudable explosive (PEX) has been examined through a series of long-term exposures. Corrosion coupons and mechanical test specimens (polymers only) were exposed to FM-1, a principal liquid component of PEX, at 74{degree}C. RX-08-FK is the LLNL designator for this formulation. Compatibility was determined by measuring changes in weight, physical dimensions, and mechanical properties, by examining the coupons for discoloration, surface attack, and corrosion products, and by analyzing for dissolved metals in the FM-1. Of the metals and alloys examined, none of the 300 series stainless steels exhibited adequate corrosion resistance after 74 days of exposure. Copper showed evidence of severe uniform surface attack. Monel 400 also exhibited signs of chemical attack. Nickel and tantalum showed less evidence of attack, although neither, was immune to the liquid. Gold coupons developed a ``tarnish`` film. The gold along with an aluminum alloy, 6061 (in the T6 condition) performed the most satisfactorily. A wide range of polymers were tested for 61 days at 74{degree}C. The materials that exhibited the most favorable response in terms of weight change, dimensional stability, and mechanical properties were Kalrez, PTFE Teflon, and polyethylene.

  11. Energy and angle resolved studies of double photo-ionisation of helium by electron time-of-flight coincidence spectroscopy

    Viefhaus, J.; Avaldi, L.; Heiser, F.; Hentges, R.; Gessner, O.; Ruedel, A.; Wiedenhoeft, M.; Wieliczek, K.; Becker, U. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany)

    1996-10-28

    Helium double photo-ionization is studied by a novel coincidence technique which employs time-of-flight spectrometers. Using this technique it is possible to collect simultaneously all the electron pairs, with different energy sharing, emitted by the absorption of a single energetic incident photon. The measurements, in a configuration where the two electrons emerge at 180{sup o} relative angle, provide the more complete information on the contribution of the ungerade amplitude to the triple differential cross section and allow the establishment of a relative scale for the full coincidence angular distribution measured by other experiments at the same photon energies, but only for a few selected energy-sharing conditions. (author).

  12. Experimental and numerical study on transient heat transfer for helium gas flowing over a twisted plate with different length

    Wang, Li; Liu, Qiusheng; Fukuda, Katsuya

    2015-01-01

    This study was conducted to investigate the transient heat transfer process between the solid surface and the coolant (helium gas) in Very High Temperature Reactor (VHTR). Forced convection transient heat transfer for helium gas flowing over a twisted plate with different length was experimentally and theoretically studied. The heat generation rate of the twisted plate was increased with a function of Q = Q_0exp(t/τ)(where t is time, τ is period). Experiment was carried out at various periods ranged from 35 ms to 14 s and gas temperature of 303 K under 500 kPa. The flow velocities ranged from 4 m/s to 10 m/s. Platinum plates with a thickness of 0.1 mm and width of 4 mm were used as the test heaters. The plates were twisted with the same helical pitch of 20 mm, and length of 26.8 mm, 67.8 mm and 106.4 mm (pitch numbers of 1, 3 and 5), respectively. Based on the experimental data, it was found that the average heat transfer coefficient approaches the quasi-steady-state value when the dimensionless period τ* (τ* = τU/L, U is flow velocity, and L is effective length) is larger than about 100 and it becomes higher when τ* is small. The heat transfer coefficient decreases with the increase of twisted plate length under the same period of heat generation rate. According to the experimental data, the distribution for heat transfer coefficient along the heater is nonlinear. Numerical simulation results were obtained for average surface temperature difference, heat flux and heat transfer coefficient of the twisted plates with different length and showed reasonable agreement with experimental data. Based on the numerical simulation, mechanism of local heat transfer coefficient distribution was clarified. (author)

  13. Helium turbo-expander with an alternator

    Akiyama, Yoshitane

    1980-01-01

    Study was made on a helium turbo-expander, the heart of helium refrigerator systems, in order to develop a system which satisfies the required conditions. A helium turbo-expander with externally pressurized helium gas bearings at the temperature of liquid nitrogen and an alternator as a brake have been employed. The essential difference between a helium turbo-expander and a nitrogen turbo-expander was clarified. The gas bearing lubricated with nitrogen at room temperature and the gas bearing lubricated with helium at low temperature were tested. The flow rate of helium in a helium refrigerator for a large superconducting magnet is comparatively small, therefore a helium turbine must be small, but the standard for large turbine design can be applied to such small turbine. Using the alternator as a brake, the turbo-expander was easily controllable electrically. The prototype turbo-expander was made, and the liquefaction test with it and MHD power generation test were carried out. (Kako, I.)

  14. Helium supply demand in future years

    Laverick, C.

    1975-01-01

    Adequate helium will be available to the year 2000 AD to meet anticipated helium demands for present day applications and the development of new superconducting technologies of potential importance to the nation. It is almost certain that there will not be enough helium at acceptable financial and energy cost after the turn of the century to meet the needs of the many promising helium based technologies now under development. Serious consideration should be given to establishing priorities in development and application based upon their relative value to the country. In the first half of the next century, three ways of estimating helium demand lead to cumulative ranges of from 75 to 125 Gcf (economic study), 89 to 470 Gcf (projected national energy growth rates) and 154 to 328 Gcf (needs for new technologies). These needs contrast with estimated helium resources in natural gas after 2000 AD which may be as low as 10 or 126 Gcf depending upon how the federal helium program is managed and the nation's natural gas resources are utilized. The technological and financial return on a modest national investment in further helium storage and a rational long term helium program promises to be considerable

  15. Compatibility Study for Plastic, Elastomeric, and Metallic Fueling Infrastructure Materials Exposed to Aggressive Formulations of Ethanol-blended Gasoline

    Kass, Michael D [ORNL; Pawel, Steven J [ORNL; Theiss, Timothy J [ORNL; Janke, Christopher James [ORNL

    2012-07-01

    In 2008 Oak Ridge National Laboratory began a series of experiments to evaluate the compatibility of fueling infrastructure materials with intermediate levels of ethanol-blended gasoline. Initially, the focus was elastomers, metals, and sealants, and the test fuels were Fuel C, CE10a, CE17a and CE25a. The results of these studies were published in 2010. Follow-on studies were performed with an emphasis on plastic (thermoplastic and thermoset) materials used in underground storage and dispenser systems. These materials were exposed to test fuels of Fuel C and CE25a. Upon completion of this effort, it was felt that additional compatibility data with higher ethanol blends was needed and another round of experimentation was performed on elastomers, metals, and plastics with CE50a and CE85a test fuels. Compatibility of polymers typically relates to the solubility of the solid polymer with a solvent. It can also mean susceptibility to chemical attack, but the polymers and test fuels evaluated in this study are not considered to be chemically reactive with each other. Solubility in polymers is typically assessed by measuring the volume swell of the polymer exposed to the solvent of interest. Elastomers are a class of polymers that are predominantly used as seals, and most o-ring and seal manufacturers provide compatibility tables of their products with various solvents including ethanol, toluene, and isooctane, which are components of aggressive oxygenated gasoline as described by the Society of Automotive Engineers (SAE) J1681. These tables include a ranking based on the level of volume swell in the elastomer associated with exposure to a particular solvent. Swell is usually accompanied by a decrease in hardness (softening) that also affects performance. For seal applications, shrinkage of the elastomer upon drying is also a critical parameter since a contraction of volume can conceivably enable leakage to occur. Shrinkage is also indicative of the removal of one or more

  16. Fabrication of aluminum nitride crucibles for molten salt and plutonium compatibility studies

    Phillips, J.A.

    1991-01-01

    The overall objective of this research was to fabricate a calcium oxide sinter-aided aluminum nitride crucible and determine the compatibility of this crucible with molten chloride salts and plutonium metal in the DOR process. Calcium oxide sinter-aided aluminum nitride was preferred over yttrium oxide sinter-aided aluminum nitride because of (1) the presence of calcium chloride, calcium oxide, and calcium metal in the molten salts utilized in the DOR process, and (2) the higher volatility of the secondary phases formed compared with phases resulting from the addition of yttrium oxide during the aluminum nitride sintering process. The calcium oxide system may yield a higher purity crystal structure with fewer secondary phases present than in the yttrium oxide system. The secondary phases that are present in the grain boundaries may be unreactive with the calcium chloride salt due to the presence of calcium in the secondary phases

  17. Compatibility study between U-UO{sub 2} cermet fuel and T91 cladding

    Mishra, Sudhir, E-mail: sudhir@barc.gov.in [Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Kaity, Santu; Khan, K.B. [Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Sengupta, Pranesh; Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2016-12-01

    Cermet is a new fuel concept for the fast reactor system and is ideally designed to combine beneficial properties of both ceramic and metal. In order to understand fuel clad chemical compatibility, diffusion couples were prepared with U-UO{sub 2} cermet fuel and T91 cladding material. These diffusion couples were annealed at 923–1073 K for 1000 h and 1223 K for 50 h, subsequently their microstructures were examined using scanning electron microscope (SEM), X-ray energy dispersive spectroscope (EDS) and electron probe microanalyser (EPMA). It was observed that the interaction between the fuel and constituents of T91 clad was limited to a very small region up to the temperature 993 K and discrete U{sub 6}(Fe,Cr) and U(Fe,Cr){sub 2} intermetallic phases developed. Eutectic microstructure was observed in the reaction zone at 1223 K. The activation energy for reaction at the fuel clad interface was determined.

  18. Complementation studies with the novel "Bungowannah" virus provide new insights in the compatibility of pestivirus proteins.

    Richter, Maria; Reimann, Ilona; Wegelt, Anne; Kirkland, Peter D; Beer, Martin

    2011-09-30

    In recent years several atypical pestiviruses have been described. Bungowannah virus is the most divergent virus in this group. Therefore, heterologous complementation was used to clarify the phylogenetic relationship and to analyze the exchangeability of genome regions encoding structural proteins. Using a BVDV type 1 backbone, chimeric constructs with substituted envelope proteins E(rns), E1 and E2, were investigated. While all constructs replicated autonomously, infectious high titer chimeric virus could only be observed after exchanging the complete E1-E2 encoding region. The complementation of E1 and E2 alone resulted only in replicons. Complementation of BVDV-E(rns) was only efficient if Bungowannah virus-E(rns) was expressed from a bicistronic construct. Our data provide new insights in the compatibility of pestivirus proteins and demonstrate that heterologous complementation could be useful to characterize new pestiviruses. Copyright © 2011 Elsevier Inc. All rights reserved.

  19. FLiNaK compatibility studies with Inconel 600 and silicon carbide

    Yoder, Graydon L., E-mail: yodergljr@ornl.gov [Oak Ridge National Laboratory, Bldg. 5700, MS 6167 Bethel Valley Rd., Oak Ridge, TN 37831 (United States); Heatherly, Dennis; Wilson, Dane [Oak Ridge National Laboratory, Bldg. 5700, MS 6167 Bethel Valley Rd., Oak Ridge, TN 37831 (United States); Caja, Mario [Electrochemical Systems, Inc. (ESI), 9320 Collingwood Rd., Knoxville, TN 37922 (United States)

    2016-10-15

    Highlights: • A versatile experimental design has been developed to examine liquid fluoride salt materials compatibility behavior. • Samples of silicon carbide and a grafoil/nickel spiral wound gasket were exposed to FLiNaK salt at 700 °C for 90 days and showed no degradation. • Alloy 600 showed material effects penetrating up to 300 μm below the salt interface after exposure to the salt for 90 days at 700 °C. • Comparison of the Alloy 600 corrosion results with existing data indicated that results were comparable to the few corrosion results available for Alloy 600. • Sapphire viewing windows incorporated in the experiment showed fogging by condensed salt components at the highest test temperatures. - Abstract: A small liquid fluoride salt test apparatus has been constructed and testing has been conducted to examine the compatibility of silicon carbide (SiC), Inconel 600 and a spiral wound gasket material in FLiNaK, the ternary eutectic alkaline metal fluoride salt mixture. These tests were conducted to evaluate materials and sealing systems that could be used in fluoride salt systems. Three months of testing at 700 °C was conducted to assure that these materials and seals would be acceptable when operating under prototypic operating conditions. The SiC specimens showed little or no change over the test period, while the spiral wound gasket material did not show any degradation except that salt might have been seeping into the outermost spirals of the gasket. The Inconel 600 specimens showed regions of voiding which penetrated the specimen surface to about 250 μm in depth. Analysis indicated that the salt had leached chrome from the Inconel surface, as was expected for this material.

  20. Evaluation of US demo helium-cooled blanket options

    Wong, C.P.C.; McQuillan, B.W.; Schleicher, R.W.

    1995-10-01

    A He-V-Li blanket design was developed as a candidate for the U.S. fusion demonstration power plant. This paper presents an 18 MPa helium-cooled, lithium breeder, V-alloy design that can be coupled to the Brayton cycle with a gross efficiency of 46%. The critical issue of designing to high gas pressure and the compatibility between helium impurities and V-alloy are addressed

  1. Study of diffusion mechanisms of helium atoms in face-centered cubic metals after α - implantation in a cyclotron

    Sciani, V.; Lucki, G.; Jung, P.

    1984-01-01

    Helium has been homogeneously introduced into gold foils at room temperature by alpha implantation in a CV-28 cyclotron. After implantation the helium release was observed in isothermal and linear heating experiments. The diffusion coefficient follows an Arrhenius behaviour with D sub(o) = 0.1 cm 2 /s and ΔH = 1.7 eV. Possible diffusion mechanisms are discussed. (Author) [pt

  2. Helium release from metals with face-centered cubic structure

    Sciani, V.; Lucki, G.; Jung, P.

    1984-01-01

    The helium release from gold sheets of 5 and 54 μm of thickness and helium concentrations from 10 -9 to 10 -5 ap of He during the isothermal and linear annealing is studied. The helium was put in the sample through the implantation of alpha particles, with variable energy,in the cyclotron. The free diffusion of the atoms of the helium, where the diffusion coefficient follows an Arrhenius law is studied. (E.G.) [pt

  3. Experimental and numerical thermohydraulic study of a supercritical helium loop in forced convection under pulsed heat loads

    Lagier, Benjamin

    2014-01-01

    Future fusion reactor devices such as ITER or JT-60SA will produce thermonuclear fusion reaction in plasmas at several millions of degrees. The confinement in the center of the chamber is achieved by very intense magnetic fields generated by superconducting magnets. These coils have to be cooled down to 4.4 K through a forced flow of supercritical helium. The cyclic behavior of the machines leads to pulsed thermal heat loads which will have to be handled by the refrigerator. The HELIOS experiment built in CEA Grenoble is a scaled down model of the helium distribution system of the tokamak JT-60SA composed of a saturated helium bath and a supercritical helium loop. The thesis work explores HELIOS capabilities for experimental and numerical investigations on three heat load smoothing strategies: the use of the saturated helium bath as an open thermal buffer, the rotation speed variation of the cold circulator and the bypassing of the heated section. The developed model describes well the physical evolutions of the helium loop (pressure, temperature, mass flow) submitted to heat loads observed during experiments. Advanced controls have been tested and validated to improve the stability of the refrigerator and to optimize the refrigeration power. (author) [fr

  4. Cooling with Superfluid Helium

    Lebrun, P; Tavian, L [European Organization for Nuclear Research, Geneva (Switzerland)

    2014-07-01

    The technical properties of helium II (‘superfluid’ helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Keywords: superfluid helium, cryogenics.

  5. Experimental study on cryogenic adsorption of methane by activated carbon for helium coolant purification of High-Temperature Gas-cooled Reactor

    Chang, Hua; Wu, Zong-Xin; Jia, Hai-Jun

    2017-01-01

    Highlights: • The cryogenic CH 4 adsorption on activated carbon was studied for design of HTGR. • The breakthrough curves at different conditions were analyzed by the MTZ model. • The CH 4 adsorption isotherm was fitted well by the Toth model and the D-R model. • The work provides valuable reference data for helium coolant purification of HTGR. - Abstract: The cryogenic adsorption behavior of methane on activated carbon was investigated for helium coolant purification of high-temperature gas-cooled reactor by using dynamic column breakthrough method. With helium as carrier gas, experiments were performed at −196 °C and low methane partial pressure range of 0–120 Pa. The breakthrough curves at different superficial velocities and different feed concentrations were measured and analyzed by the mass-transfer zone model. The methane single-component adsorption isotherm was obtained and fitted well by the Toth model and the Dubinin-Radushkevich model. The adsorption heat of methane on activated carbon was estimated. The cryogenic adsorption process of methane on activated carbon has been verified to be effective for helium coolant purification of high-temperature gas-cooled reactor.

  6. The study on electromagnetic compatibility of DC electric motor in HAPS

    Junping, Geng; Ronghong, Jin; Yu, Fan; Bo, Liu; Jiaqiang, Li; Yuebo, Cheng; Zhongyuan, Wang [Shanghai Jiao Tong Univ., Dpt. Electronic Engineering, Shanghai (China)

    2005-10-01

    The electromagnetic compatibility (EMC) problem of high altitude platform systems (HAPS) is investigated in this paper. A physical model for electromagnetic interferences (EMI) of electromagnetic radiation of spark discharge in DC electric motor is proposed. Based on this model, EMI frequency points has been estimated by approximative equation for the given structure and size of a motor, and EMI frequency points, peak values that received by the ports of antennas and far-field pattern have been calculated. The estimated results are consistent with the calculated ones. These frequency bands and spatial directions with max EMI should be avoided in the valid information when the HAPS system is being designed. Two methods are taken to shield electromagnetic radiation, either to mount a metal plate near the DC electric motor (EMI source), or to mount a perfect conductor board near the antenna array (sensitive element), are valid to shield electromagnetic radiation, but to mount a metal plate near the EMI source is more effective. (authors)

  7. Study of Material Compatibility for a Thermal Energy Storage System with Phase Change Material

    Songgang Qiu

    2018-03-01

    Full Text Available The suitability of stainless steel 316L and Inconel 625 for use in a latent heat thermal energy storage (TES system was investigated. A NaCl–NaF eutectic mixture with a melting temperature of 680 °C was used as the phase change material (PCM. Containers were filled with the PCM prior to heating to 750 °C, then examined after 100 and 2500 h of high-temperature exposure by analyzing the material surface and cross-section areas. A small amount of corrosion was present in both samples after 100 h. Neither sample suffered significant damage after 2500 h. The undesirable inter-granular grain boundary attack found in SS316L samples was in the order of 1–2 µm in depth. On Inconel 625 sample surface, an oxide complex formed, resisting material dissolution into the PCM. The surface morphology of tested samples remained largely unchanged after 2500 h, but the corrosion pattern changed from an initially localized corrosion penetration to a more uniform type. After 2500 h, the corrosion depth of Inconel 625 remained at roughly 1–2 µm, indicating that the corrosion rate decelerated. Both materials demonstrated good compatibility with the chosen NaF–NaCl eutectic salt, but the low corrosion activity in Inconel 625 samples shows a performance advantage for long term operation.

  8. Compatibility study of Trichoderma harzianum Rifai and rice fungicides, and effects on three fungal plant pathogens

    Manuel Francisco Rodríguez Saldaña

    2017-04-01

    Full Text Available This research took place at the Provincial Plant Sanitation Laboratory, in Camaguey, Cuba, between September 2013 and September 2015. The in vitro compatibility and antagonistic capacity of Trichoderma harzianum Rifai (strain A-34 on rice pathogens (Bipolaris oryzae Breda de Haan, Sarocladium oryzae (Sawada w., Gams and D. Hawksworth and Magnaporthe grisea (Hebert Barr, was determined against pesticides used on rice. Assessment using traditional methods of microbiological isolation of mycelial growth, sporulation and conidial germination of the antagonist, to determine if the action mechanisms (antibiosis, competence, parasitism against fungal pathogens, was made between 24 and 216 hours of application. A bifactorial design in dual culture was used for statistical analysis, along with scales for determination of microbial antagonistic capacity. Active ingredients tebuconazol + procloraz, trifloxistrobin+ ciproconazole, and epoxiconazole + kresoxim-methyl, affected mycelial growth of the antagonist. Moreover, the antagonist against active ingredients carbendazim, copper oxychloride, azoxystrobin and tebuconazo + triadimenol showed mycelial growth, sporulation and pathogen interaction, affecting their growth by means of coiling, penetration, granulation, and cell lysis, between 96 and 216 hours.

  9. Study on the Chemical Compatibility of Silicon Carbide regarding Uranium Dioxide

    Braun, J.; Sauder, C.; Guéneau, C.; Alpettaz, T.; Balbaud, F.; Allegri, P.; Brackx, E.

    2013-01-01

    Conclusions/perspectives: • SiC/SiC composites are considered in SFR reactors as structure materials. • Knudsen Cell Mass Spectrometry combined with thermodynamic calculations to investigate the compatibility of UO 2+x regarding SiC: - Open system; - Signals overlapping issues →New spectrometer to work at different energies; - Temperature limited by the molecular beam regime →Improvement of pumping capacity. • UO 2.15 /SiC at 1500°C: - Strong interaction; - Reduction of UO 2+x by SiC; - CO formation. To a lesser extend SiO, CO 2 ; - Formation of USi 1.88 ; U 3 Si 5 ; U 3 Si 2 C 2 ; UC; UC 2 . • UO 2.02 /SiC: - 1200°C – Limited reaction; • 1350/1500°C – Three areas (UC/USi x on the periphery - UO 2 at the center - USi x in-between)/ Characteristic of a gaseous diffusion; • 1650°C – Crucible strongly-attacked – liquid-phase detected. Perspectives: - Diffusion couples: closed system; - Alternative crucible (Ta -W)

  10. Diffusion of helium and nucleation-growth of helium-bubbles in metallic materials

    Zhang Chonghong; Chen Keqin; Wang Yinshu

    2001-01-01

    Studies of diffusion and aggregation behaviour of helium in metallic materials are very important to solve the problem of helium embrittlement in structural materials used in the environment of nuclear power. Experimental studies on helium diffusion and aggregation in austenitic stainless steels in a wide temperature range have been performed in authors' research group and the main results obtained are briefly summarized. The mechanism of nucleation-growth of helium-bubbles has been discussed and some problems to be solved are also given

  11. Theoretical and experimental studies on transient heat transfer for forced convection flow of helium gas over a horizontal cylinder

    Liu Qiusheng; Katsuya Fukuda; Zhang Zheng

    2005-01-01

    Forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a horizontal cylinder (heater) was theoretically and experimentally studied. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. It was clarified that the surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. The temperature distribution near the cylinder becomes larger as the surface temperature increases. The values of numerical solution for surface temperature and heat flux agree well with the experimental data for the cylinder diameter of 1 mm. However, the heat flux shows difference from the experimental values for the cylinder diameters of 0.7 mm and 2.0 mm. In the experimental studies, the authors measured heat flux, surface temperature, and transient heat transfer coefficients for forced convection flow of helium gas over horizontal cylinders under wide experimental conditions. The platinum cylinders with diameters of 1.0 mm, 0.7 mm, and 2.0 mm were used as test heaters and heated by electric current with an exponential increase of Q 0exp (t/τ) . The gas flow velocities ranged from 2 to 10 m/s, the gas temperatures ranged from 303 to 353 K, and the periods ranged from 50 ms to 20 s. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The transient heat transfer shows less dependence on the gas flowing velocity when the period becomes very shorter. The heat transfer shifts to the quasi-steady-state heat transfer for longer periods and shifts to the transient heat transfer for shorter periods at the same flow velocity. It also approaches the quasi-steady-state one for higher flow velocity at the same period. The transient heat transfer coefficients show significant dependence on

  12. Relation between the conditions of helium ion implantation and helium void equilibrium parameters

    Neklyudov, I.M.; Rybalko, V.F.; Ruzhitskij, V.V.; Tolstolutskaya, G.D.

    1981-01-01

    The conditions of helium thermodynamic equilibrium in a system of voids produced by helium ion bombardment of a metal sample are studied. As an initial equation for description of the equilibrium the Clapeyron equation was used. The equation is obtained relating basic parameters of helium voids (average diameter and density) to irradiation parameters (dose, ion energy (straggling)) and properties of the metal (surface tension coefficient, yield strength). Comparison of the calculations with experimental data on helium in nickel found in literature shows that the equation yields satisfactory resutls for the dose range 1.10 16 -1x10 17 cm -2 and temperatures T [ru

  13. A study of artefacts in simultaneous PET and MR imaging using a prototype MR compatible PET scanner

    Slates, R.B.; Farahani, K.; Marsden, P.K.; Taylor, J.; Summers, P.E.; Williams, S.; Beech, J.

    1999-01-01

    We have assessed the possibility of artefacts that can arise in attempting to perform simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) using a small prototype MR compatible PET scanner (McPET). In these experiments, we examine MR images for any major artefacts or loss in image quality due to inhomogeneities in the magnetic field, radiofrequency interference or susceptibility effects caused by operation of the PET system inside the MR scanner. In addition, possible artefacts in the PET images caused by the static and time-varying magnetic fields or radiofrequency interference from the MR system were investigated. Biological tissue and a T 2 -weighted spin echo sequence were used to examine susceptibility artefacts due to components of the McPET scanner (scintillator, optical fibres) situated in the MR field of view. A range of commonly used MR pulse sequences was studied while acquiring PET data to look for possible artefacts in either the PET or MR images. Other than a small loss in signal-to-noise using gradient echo sequences, there was no significant interaction between the two imaging systems. Simultaneous PET and MR imaging of simple phantoms was also carried out in different MR systems with field strengths ranging from 0.2 to 4.7 T. The results of these studies demonstrate that it is possible to acquire PET and MR images simultaneously, without any significant artefacts or loss in image quality, using our prototype MR compatible PET scanner. (author)

  14. Apparent oxygen utilization rates calculated from tritium and helium-3 profiles at the Bermuda Atlantic Time-series Study site

    R. H. R. Stanley

    2012-06-01

    Full Text Available We present three years of Apparent Oxygen Utilization Rates (AOUR estimated from oxygen and tracer data collected over the ocean thermocline at monthly resolution between 2003 and 2006 at the Bermuda Atlantic Time-series Study (BATS site. We estimate water ages by calculating a transit time distribution from tritium and helium-3 data. The vertically integrated AOUR over the upper 500 m, which is a regional estimate of export, during the three years is 3.1 ± 0.5 mol O2 m−2 yr−1. This is comparable to previous AOUR-based estimates of export production at the BATS site but is several times larger than export estimates derived from sediment traps or 234Th fluxes. We compare AOUR determined in this study to AOUR measured in the 1980s and show AOUR is significantly greater today than decades earlier because of changes in AOU, rather than changes in ventilation rates. The changes in AOU are likely a methodological artefact associated with problems with early oxygen measurements.

  15. Exergoeconomic assessment and parametric study of a Gas Turbine-Modular Helium Reactor combined with two Organic Rankine Cycles

    Mohammadkhani, F.; Shokati, N.; Mahmoudi, S.M.S.; Yari, M.; Rosen, M.A.

    2014-01-01

    An exergoeconomic analysis is reported for a combined system with a net electrical output of 299 MW in which waste heat from a Gas Turbine-Modular Helium Reactor (GT-MHR) is utilized by two Organic Rankine Cycles (ORCs). A parametric study is also done to reveal the effects on the exergoeconomic performance of the combined system of such significant parameters as compressor pressure ratio, turbine inlet temperature, temperatures of evaporators, pinch point temperature difference in the evaporators and degree of superheat at the ORC (Organic Rankine Cycle) turbines inlet. Finally the combined cycle performance is optimized from the viewpoint of exergoeconomics. The results show that the precooler, the intercooler and the ORC condensers exhibit the worst exergoeconomic performance. For the overall system, the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate are determined to be 37.95%, 6876 $/h and 11,242 $/h, respectively. Also, it is observed that the unit cost of electricity produced by the GT-MHR turbine increases with increasing GT-MHR turbine inlet temperature but decreases as the other above mentioned parameters increase. - Highlights: • An exergoeconomic analysis is performed for the GT-MHR/ORC (Organic Rankine Cycle) combined cycle. • The effects of decision parameters on the exergoeconomic performance are studied. • The highest exergy destructions occur in the precooler, intercooler and condenser. • Superheating the working fluid at the ORC turbine inlet is not necessary. • Thermodynamic and exergoeconomic optimal conditions differ from each other

  16. Helium the disappearing element

    Sears, Wheeler M

    2015-01-01

    The subject of the book is helium, the element, and its use in myriad applications including MRI machines, particle accelerators, space telescopes, and of course balloons and blimps. It was at the birth of our Universe, or the Big Bang, where the majority of cosmic helium was created; and stellar helium production continues. Although helium is the second most abundant element in the Universe, it is actually quite rare here on Earth and only exists because of radioactive elements deep within the Earth. This book includes a detailed history of the discovery of helium, of the commercial industry built around it, how the helium we actually encounter is produced within the Earth, and the state of the helium industry today. The gas that most people associate with birthday party balloons is running out. “Who cares?” you might ask. Well, without helium, MRI machines could not function, rockets could not go into space, particle accelerators such as those used by CERN could not operate, fiber optic cables would not...

  17. Helium dilution refrigerator

    1973-01-01

    A new system of continuous heat exchange for a helium dilution refrigerator is proposed. The 3 He effluent tube is concurrent with the affluent mixed helium tube in a vertical downward direction. Heat exchange efficiency is enhanced by placing in series a number of elements with an enlarged surface area

  18. A Web-based searchable system to confirm magnetic resonance compatibility of implantable medical devices in Japan: a preliminary study.

    Fujiwara, Yasuhiro; Fujioka, Hitoshi; Watanabe, Tomoko; Sekiguchi, Maiko; Murakami, Ryuji

    2017-09-01

    Confirmation of the magnetic resonance (MR) compatibility of implanted medical devices (IMDs) is mandatory before conducting magnetic resonance imaging (MRI) examinations. In Japan, few such confirmation methods are in use, and they are time-consuming. This study aimed to develop a Web-based searchable MR safety information system to confirm IMD compatibility and to evaluate the usefulness of the system. First, MR safety information for intravascular stents and stent grafts sold in Japan was gathered by interviewing 20 manufacturers. These IMDs were categorized based on the descriptions available on medical package inserts as: "MR Safe," "MR Conditional," "MR Unsafe," "Unknown," and "No Medical Package Insert Available". An MR safety information database for implants was created based on previously proposed item lists. Finally, a Web-based searchable system was developed using this database. A questionnaire was given to health-care personnel in Japan to evaluate the usefulness of this system. Seventy-nine datasets were collected using information provided by 12 manufacturers and by investigating the medical packaging of the IMDs. Although the datasets must be updated by collecting data from other manufacturers, this system facilitates the easy and rapid acquisition of MR safety information for IMDs, thereby improving the safety of MRI examinations.

  19. Friction and wear studies of graphite and a carbon-carbon composite in air and in helium

    Li, C.C.; Sheehan, J.E.

    1980-10-01

    Sliding friction and wear tests were conducted on a commercial isotropic graphite and a carbon-carbon composite in air, purified helium, and a helium environment containing controlled amounts of impurities simulating the primary coolant chemistry of a high-temperature gas-cooled reactor (HTGR). The friction and wear characteristics of the materials investigated were stable and were found to be very sensitive to the testing temperature. In general, friction and wear decreased with increasing temperature in the range from ambient to 950 0 C. This temperature dependence is concluded to be due to chemisorption of impurities to form lubricating films and oxidation at higher temperatures, which reduce friction and wear. Graphite and carbon-carbon composites are concluded to be favorable candidate materials for high-temperature sliding service in helium-cooled reactors

  20. Particle energy loss spectroscopy and SEM studies of topography development in thin aluminium films implanted with high doses of helium

    Barfoot, K.M.; Webb, R.P.; Donnelly, S.E.

    1984-01-01

    Development of topography in thin (55.5 μg cm -2 ) self-supporting aluminium films, caused by high fluence (approx. 10 17 ions cm -2 ) irradiation with 5 keV helium ions, has been observed. This has been achieved by measuring the topography-enhanced energy straggling of 0.40 MeV 4 He + ions transmitted through the foils and detected with an electrostatic analyser of resolution 0.2 keV. Features, about 0.7 μm in width, are observed with scanning electron microscopy. TRIM Monte Carlo calculations of the implantation processes are performed in order to follow the helium implantation and damage depth distributions. It is deduced that a form of thin film micro-wrinkling has occurred which is caused by the relief of stress brought about by the implantation of helium. (author)

  1. Study on flow rate measurement and visualization of helium-air exchange flow through a small opening

    Fumizawa, Motoo

    1992-01-01

    This paper deals with an experimental investigation on buoyancy-driven exchange flows through horizontal and inclined openings. The method of the mass increment was developed to measure the flow rate in helium-air system and a displacement fringe technique was adopted in Mach-Zehnder interferometer to visualize the flow. As the result, the followings were obtained: Flow visualization results indicate that the upward and downward plumes of helium and air break through the opening intermittently, and they swing in the lateral direction through the horizontal opening. It is clearly visualized that the exchange flows through the inclined openings take place smoothly and stably in the separated passages. The inclination angle for the maximum Froude number decreases with increasing length-to-diameter ratio in the helium-air system, on the contrary to Mercer's experimental results in the water-brine system indicating that the angle remains almost constant. (author)

  2. Study of UO2 mechanical behaviour implanted with helium ions using X-ray micro-diffraction and mechanical modeling

    Ibrahim, Marcelle

    2015-01-01

    In order to study the mechanical behavior of nuclear fuel during direct long term storage, UO 2 polycrystals were implanted with Helium ions at a thin surface layer (1 μm approximately), which leads to stress and strain fields in the layer. Strains were measured, at the grains scale, by X-ray micro-diffraction, using synchrotron radiation (ESRF). Image analysis methods were developed for an automatic analysis of the large number of diffraction patterns. Applying statistical tools to Laue patterns allows an automatic detection of low quality images, and enhances the measurement precision. At low layer thickness, the mechanical interaction between grains can be neglected. At higher thickness, experimental results showed a higher mechanical interaction near grain boundaries that can be modeled using finite elements method. Geostatistical tools were used to quantify these interactions. The swelling and the elastic constants in the implanted layer can be estimated through the measured strains on a large number of grains with different orientations. This work allows the determination of the swelling of nuclear fuel in irradiation conditions, as well as the modification of its elastic properties. (author) [fr

  3. Studies on the effects of helium on the microstructural evolution of V-3.8Cr-3.9Ti

    Doraiswamy, N.; Kestel, B.; Alexander, D.E. [Argonne National Labs., IL (United States)

    1997-04-01

    The favorable physical and mechanical properties of V-3.8Cr-3.9Ti (wt.%), when subjected to neutron irradiation, has lead to considerable attention being focused on it for use in fusion reactor structural applications. However, there is limited data on the effects of helium on physical and mechanical properties of this alloy. Understanding these effects are important since helium will be generated by direct {alpha}-injection or transmutation reactions in the fusion environment, typically at a rate of {approx}5 appm He/dpa. Helium has been shown to cause substantial embrittlement, even at room temperature in vanadium and its alloys. Recent simulations of the fusion environment using the Dynamic Helium Charging Experiments (DHCE) have also indicated that the mechanical properties of vanadium alloys are altered by the presence of helium in post irradiation tests performed at room temperature. While the strengths were lower, room temperature ductilities of the DHCE specimens were higher than those of non-DHCE specimens. These changes have been attributed to the formation of different types of hardening centers in these alloys due to He trapping. Independent thermal desorption experiments suggest that these hardening centers may be associated with helium-vacancy-X (where X = O, N, and C) complexes. These complexes are stable below 290{degrees}C and persist at room temperature. However, there has been no direct microstructural evidence correlating the complexes with irradiation effects. An examination of the irradiation induced microstructure in samples preimplanted with He to different levels would enable such a correlation.

  4. Study of interstellar helium from photometric observations at 58.4 nm of the interplanetary environment from Prognoz 6 satellite

    Dalaudier, Francis.

    1981-06-01

    This thesis is devoted to an ''interplanetary helium'' experiment, the aim of the work being to acquire a greater understanding of the local interstellar environment and its interaction with the solar system. Measurements made from the Prognoz 6 satellite on ultraviolet fluxes from hydrogen (121.6 nm) and neutral and ionized helium (58.4 nm and 30.4 nm respectively) were used to construct a computer model. Most of the work performed deals with comparing and interpreting the results obtained [fr

  5. Exotic helium molecules

    Portier, M.

    2007-12-01

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range 4 He 2 (2 3 S 1 -2 3 P 0 ) molecule, or a 4 He 2 (2 3 S 1 -2 3 S 1 ) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 ± 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range 4 He 2 (2 3 S 1 -2 3 S 1 ) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime τ = (1.4 ± 0.3) μs is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  6. A liquid helium saver

    Avenel, O.; Der Nigohossian, G.; Roubeau, P.

    1976-01-01

    A cryostat equipped with a 'liquid helium saver' is described. A mass flow rate M of helium gas at high pressure is injected in a counter-flow heat exchanger extending from room to liquid helium temperature. After isenthalpic expansion through a calibrated flow impedance this helium gas returns via the low pressure side of the heat exchanger. The helium boil-off of the cryostat represents a mass flow rate m, which provides additional precooling of the incoming helium gas. Two operating regimes appear possible giving nearly the same efficiency: (1) high pressure (20 to 25 atm) and minimum flow (M . L/W approximately = 1.5) which would be used in an open circuit with helium taken from a high pressure cylinder; and (2) low pressure (approximately = 3 atm), high flow (M . L/W > 10) which would be used in a closed circuit with a rubber diaphragm pumping-compressing unit; both provide a minimum theoretical boil-off factor of about 8%. Experimental results are reported. (U.K.)

  7. A reliability study on brain activation during active and passive arm movements supported by an MRI-compatible robot.

    Estévez, Natalia; Yu, Ningbo; Brügger, Mike; Villiger, Michael; Hepp-Reymond, Marie-Claude; Riener, Robert; Kollias, Spyros

    2014-11-01

    In neurorehabilitation, longitudinal assessment of arm movement related brain function in patients with motor disability is challenging due to variability in task performance. MRI-compatible robots monitor and control task performance, yielding more reliable evaluation of brain function over time. The main goals of the present study were first to define the brain network activated while performing active and passive elbow movements with an MRI-compatible arm robot (MaRIA) in healthy subjects, and second to test the reproducibility of this activation over time. For the fMRI analysis two models were compared. In model 1 movement onset and duration were included, whereas in model 2 force and range of motion were added to the analysis. Reliability of brain activation was tested with several statistical approaches applied on individual and group activation maps and on summary statistics. The activated network included mainly the primary motor cortex, primary and secondary somatosensory cortex, superior and inferior parietal cortex, medial and lateral premotor regions, and subcortical structures. Reliability analyses revealed robust activation for active movements with both fMRI models and all the statistical methods used. Imposed passive movements also elicited mainly robust brain activation for individual and group activation maps, and reliability was improved by including additional force and range of motion using model 2. These findings demonstrate that the use of robotic devices, such as MaRIA, can be useful to reliably assess arm movement related brain activation in longitudinal studies and may contribute in studies evaluating therapies and brain plasticity following injury in the nervous system.

  8. The energy and stability of helium-related cluster in nickel: A study of molecular dynamics simulation

    Gong, Hengfeng, E-mail: gonghengfeng@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Division of Nuclear Materials and Engineering, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Wang, Chengbin; Zhang, Wei; Xu, Jian [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Division of Nuclear Materials and Engineering, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Huai, Ping, E-mail: huaiping@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Division of Nuclear Materials and Engineering, Shanghai 201800 (China); Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Deng, Huiqiu; Hu, Wangyu [Hunan University, Department of Applied Physics, Changsha 410082 (China)

    2016-02-01

    Highlights: • The He-related clusters exhibit the very high symmetry. • The trapping capability of vacancy to defects becomes weak due to the pre-existed SIA. • The average length of He{sub N}V{sub 1} clusters is longer than one of He{sub N} and He{sub N}V{sub 1}SIA{sub 1} cluster. - Abstract: Using molecular dynamics simulation, we investigated the energy and stability of helium-related cluster in nickel. All the binding energies of the He-related clusters are demonstrated to be positive and increase with the cluster sizes. Due to the pre-existed self-interstitial nickel atom, the trapping capability of vacancy to defects becomes weak. Besides, the minimum energy configurations of He-related clusters exhibit the very high symmetry in the local atomistic environment. And for the He{sub N} and He{sub N}V{sub 1}SIA{sub 1} clusters, the average length of He–He bonds shortens, but it elongates for the He{sub N}V{sub 1} clusters with helium cluster sizes. The helium-to-vacancy ratio plays a decisive role on the binding energies of He{sub N}V{sub M} cluster. These results can provide some excellent clues to insight the initial stage of helium bubbles nucleation and growth in the Ni-based alloys for the Generation-IV Molten Salt Reactor.

  9. CONTENT AND LANGUAGE INTEGRATED LEARNING (CLIL: AN EXPERIMENTAL STUDY ON CLIL COMPATIBILITY WITH THE MODERN GREEK EDUCATIONAL SYSTEM

    Catherine Georgopoulou Theodosiou

    2016-06-01

    Full Text Available This paper focuses on the Content and Language Integrated Learning (CLIL method for (foreign language teaching. The CLIL approach is rapidly gaining momentum across Europe and all over the world. It is the result of recent European Union efforts to develop and apply innovative educational practices of interdisciplinary character in order to bridge the gap between foreign language education and optimum learning outcomes. In order to investigate the compatibility of CLIL with the contemporary Greek educational reality, a small-scale experimental research study was set up, including the development of original e-learning material, a pilot class instruction based on this material and the evaluation of the results. The class instruction was based on Project-Based Learning whereas Collaborative Learning was supported by the Edmodo e-learning platform. Information on the progress of the pilot class instruction and the learning outcomes achieved was disseminated through a wiki set up for this task.

  10. Design and performance study of the helium-cooled T-tube divertor concept

    Ihli, T.; Raffray, A.R.; Abdel-Khalik, S.I.; Shin, S.

    2007-01-01

    The ARIES-CS study has been launched with the goal of developing through physics and engineering optimization an attractive power plant concept based on a compact stellarator configuration. The study included an effort to characterize the divertor location and corresponding heat load distribution, and to develop a He-cooled divertor concept that could accommodate a heat flux of at least 10 MW/m 2 , and that would integrate well with the other power core components. This paper describes the design study of this divertor concept, which, although developed for a compact stellarator, is well suited for a tokamak configuration also

  11. Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies

    Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus

    2015-01-01

    , if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. The accelerated stability studies performed in the microwave oven using...... a design of experiments (DoE) approach in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric......, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating...

  12. DUPIC fuel compatibility assessment

    Choi, Hang Bok; Rho, G. H.; Park, J. W. [and others

    2000-03-01

    The purpose of this study is to assess the compatibility of DUPIC(Direct Use of Spent PWR Fuel in CANDU Reactors) fuel with the current CANDU 6 reactor, which is one of the technology being developed to utilize the spent PWR fuel in CANDU reactors. The phase 1 study of this project includes the feasibility analysis on applicability of the current core design method, the feasibility analysis on operation of the DUPIC fuel core, the compatibility analysis on individual reactor system, the sensitivity analysis on the fuel composition, and the economic analysis on DUPIC fuel cycle. The results of the validation calculations have confirmed that the current core analysis system is acceptable for the feasibility study of the DUPIC fuel compatibility analysis. The results of core simulations have shown that both natural uranium and DUPIC fuel cores are almost the same from the viewpoint of the operational performance. For individual reactor system including reactively devices, the functional requirements of each system are satisfied in general. However, because of the pronounced power flattening in the DUPIC core, the radiation damage on the critical components increases, which should be investigated more in the future. The DUPIC fuel composition heterogeneity dose not to impose any serious effect on the reactor operation if the fuel composition is adjusted. The economics analysis has been performed through conceptual design studies on the DUPIC fuel fabrication, fuel handling in a plant, and spent fuel disposal, which has shown that the DUPIC fuel cycle is comparable to the once-trough fuel cycle considering uncertainties associated with unit costs of the fuel cycle components. The results of Phase 1 study have shown that it is feasible to use the DUPIC fuel in CANDU reactors without major changes in hardware. However further studies are required to confirm the safety of the reactor under accident condition.

  13. DUPIC fuel compatibility assessment

    Choi, Hang Bok; Rho, G. H.; Park, J. W. and others

    2000-03-01

    The purpose of this study is to assess the compatibility of DUPIC(Direct Use of Spent PWR Fuel in CANDU Reactors) fuel with the current CANDU 6 reactor, which is one of the technology being developed to utilize the spent PWR fuel in CANDU reactors. The phase 1 study of this project includes the feasibility analysis on applicability of the current core design method, the feasibility analysis on operation of the DUPIC fuel core, the compatibility analysis on individual reactor system, the sensitivity analysis on the fuel composition, and the economic analysis on DUPIC fuel cycle. The results of the validation calculations have confirmed that the current core analysis system is acceptable for the feasibility study of the DUPIC fuel compatibility analysis. The results of core simulations have shown that both natural uranium and DUPIC fuel cores are almost the same from the viewpoint of the operational performance. For individual reactor system including reactively devices, the functional requirements of each system are satisfied in general. However, because of the pronounced power flattening in the DUPIC core, the radiation damage on the critical components increases, which should be investigated more in the future. The DUPIC fuel composition heterogeneity dose not to impose any serious effect on the reactor operation if the fuel composition is adjusted. The economics analysis has been performed through conceptual design studies on the DUPIC fuel fabrication, fuel handling in a plant, and spent fuel disposal, which has shown that the DUPIC fuel cycle is comparable to the once-trough fuel cycle considering uncertainties associated with unit costs of the fuel cycle components. The results of Phase 1 study have shown that it is feasible to use the DUPIC fuel in CANDU reactors without major changes in hardware. However further studies are required to confirm the safety of the reactor under accident condition

  14. Electrochemical, Polarization, and Crevice Corrosion Testing of Nitinol 60, A Supplement to the ECLSS Sustaining Materials Compatibility Study

    Lee, R. E.

    2016-01-01

    In earlier trials, electrochemical test results were presented for six noble metals evaluated in test solutions representative of waste liquids processed in the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS). Subsequently, a seventh metal, Nitinol 60, was added for evaluation and subjected to the same test routines, data analysis, and theoretical methodologies. The previous six test metals included three titanium grades, (commercially pure, 6Al-4V alloy and 6Al-4V low interstitial alloy), two nickel-chromium alloys (Inconel(RegisteredTrademark) 625 and Hastelloy(RegisteredTrademark) C276), and one high-tier stainless steel (Cronidur(RegisteredTrademark) 30). The three titanium alloys gave the best results of all the metals, indicating superior corrosive nobility and galvanic protection properties. For this current effort, the results have clearly shown that Nitinol 60 is almost as noble as titanium, being very corrosion-resistant and galvanically compatible with the other six metals electrochemically and during long-term exposure. is also quite noble as it is very corrosion resistant and galvanically compatible with the other six metals from both an electrochemical perspective and long-term crevice corrosion scenario. This was clearly demonstrated utilizing the same techniques for linear, Tafel and cyclic polarization, and galvanic coupling of the metal candidate as was done for the previous study. The high nobility and low corrosion susceptibility for Nitinol 60 appear to be intermediate to the nickel/chromium alloys and the titanium metals with indications that are more reflective of the titanium metals in terms of general corrosion and pitting behavior.

  15. Theoretical Study of the Pyridine-Helium van der Waals Complexes

    v, Hubert; Henriksen, Christian; Fernandez, Berta

    2015-01-01

    In this study we evaluate a high-level ab initio ground-state intermolecular potential-energy surface for the pyridine–He van der Waals complex, using the CCSD(T) method and Dunning’s augmented correlation consistent polarized valence double-ζ basis set extended with a set of 3s3p2d1f1g midbond...

  16. Studies on Methods for Detection of Salmonella SP. in Meat with Regard to Equivalency and Compatibility

    Paulsen, P.; Smulders, F. J.M. [Institute for Meat Hygiene, Meat Technology and Food Science, University for Veterinary Medicine, Vienna (Austria); Girma, Z. [Addis Ababa University, Debre Zeit (Ethiopia); Farghaly, R. [South Valley University, Qena (Egypt)

    2005-01-15

    This contribution summarizes research activities on the evaluation of methods for detection of Salmonella in meat, especially poultry. The following items were under study: (1) studies on motility media for detection of Salmonella spp.: evaluation of MSRV media of different manufacturers; evaluation of novobiocine supplementation to MSRV and DIASALM media; abuse studies of incubation temperature; comparison of DIASALM medium vs. MSRV; (2) Salmonella antigen detection by a commercial EIA (Vidas System). The findings and information from other sources (references, technical papers) are to be combined in a database to give a comprehensive overview on the currently applied methodology. Basic considerations on the structure of this database are demonstrated. (author)

  17. Series solutions to partial differential equations. A study of the singularities, expansions, and solutions of Schroedinger's equation for the helium atom

    Mahlab, M.S.

    1975-01-01

    All the presently available techniques for solving Schroedinger's differential equation for helium-like atoms display poor convergence of the wave function in the neighborhood of the singularities of the Hamiltonian operator. In general most of the methods of solving this equation will converge in the appropriate limit to the exact wave function; however, convergence is slow, especially near the singularities of this differential equation. These difficulties become readily apparent from local energy studies. A technique is presented that avoids these difficulties. The wave function it produces is specifically most accurate at the singularities of the Hamiltonian. The novel aspect of this treatment is the subdivision of the space spanned by the wave function. Different expansions are picked such that they converge rapidly in each of the different subdivisions. These expansions may be constructed in such a way that they obey the boundary conditions in their respective subdivision. Most importantly, all the information available from the recursion relations associated with the differential equation may be incorporated into these expansions. A systematic procedure is presented such that these expansions may be brought together to form a wave function that satisfies all the continuity requirements. An S-state helium wave function was constructed to demonstrate that this method of treatment is feasible, and capable of indefinite systematic improvement. A discussion of several new asymptotic expansions that were constructed for the helium wave function, as well as an improved functional form for the small electron-nucleus wave function, is included in this presentation

  18. A comparative study on total reflection X-ray fluorescence determination of low atomic number elements in air, helium and vacuum atmospheres using different excitation sources

    Misra, N. L.; Kanrar, Buddhadev; Aggarwal, S. K.; Wobrauschek, Peter; Rauwolf, M.; Streli, Christina

    2014-09-01

    A comparison of trace element determinations of low atomic number (Z) elements Na, Mg, Al, P, K and Ca in air, helium and vacuum atmospheres using W Lβ1, Mo Kα and Cr Kα excitations has been made. For Mo Kα and W Lβ1 excitations a Si (Li) detector with beryllium window was used and measurements were performed in air and helium atmospheres. For Cr Kα excitation, a Si (Li) detector with an ultra thin polymer window (UTW) was used and measurements were made in vacuum and air atmospheres. The sensitivities of the elemental X-ray lines were determined using TXRF spectra of standard solutions and processing them by IAEA QXAS program. The elemental concentrations of the elements in other solutions were determined using their TXRF spectra and pre-determined sensitivity values. The study suggests that, using the above experimental set up, Mo Kα excitation is not suited for trace determination of low atomic number element. Excitation by WLβ1 and helium atmosphere, the spectrometer can be used for the determination of elements with Z = 15 (P) and above with fairly good detection limits whereas Cr Kα excitation with ultra thin polymer window and vacuum atmosphere is good for the elements having Z = 11 (Na) and above. The detection limits using this set up vary from 7048 pg for Na to 83 pg for Ti.

  19. Study on the conductor-insulator friction at liquid helium temperature

    Batakov, Yu.P.; Kostenko, A.I.; Semenov, O.V.; Trokhachev, G.V.

    1982-01-01

    A study is made on conductor heating as a result of friction following displacements under coolina conditions close to those for conductors in superconducting magnets with cryostatic stabilization. Sliding of a 2x15 mm 2 copper plate an averawithge surface roughness of 1m over fiberglas0 μ textolite and teflon is studied. ''Sudden'' displacements are caused by application of the displacing force exceeding the static frictional force several times. If in case of friction displacements.are caused by the action of a force equal to the static frictional force, stops increasing the displacement time are possible. This may ta.ke place following the displacement of the conductor parts in the superconducting magnet coils, owing to which the displacement may turn out to be not ''sudden''. In this case in designing superconducting magnets the tolerances for conductor portion displacements, which do not affect the magnet normal operation, may be less strict

  20. Study of a new direct current atmospheric pressure glow discharge in helium

    Gielniak, B. [University of Hamburg, Institute for Inorganic and Applied Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany); Fiedler, T. [Johannes Gutenberg-University Mainz, Institute for Inorganic and Analytical Chemistry, Duesbergweg 10-14, 55128 Mainz (Germany); Broekaert, J.A.C., E-mail: jose.broekaert@chemie.uni-hamburg.de [University of Hamburg, Institute for Inorganic and Applied Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany)

    2011-01-15

    In this study a new DC-APGD operated in He was developed and characterized. The discharge is operated at 0.9 kV and about 25-35 mA and at a gas flow of 100 ml/min. The source was spectroscopically studied and parameters such as the rotational temperature (T{sub rot}), the excitation temperature (T{sub exc}), the ionization temperature (T{sub ion}) and the electron number density (n{sub e}) were determined. The current-voltage characteristic of the source was studied as well. At optimized conditions the discharge operates in the normal region of the current-voltage characteristic. Rotational and excitation temperatures determined with the use of OH band and Fe I lines as thermometric species were of the order of about 900-1200 and 4500-5500 K, respectively. This indicates that despite of the atmospheric pressure, the discharge is not in LTE. Spatially resolved temperature measurements were performed with axial as well as radial resolution and showed relatively flat profiles. Axially resolved emission intensity profiles for several species such as H, N{sub 2}, N{sub 2}{sup +}, OH, He and Hg were determined. It also was found that H{sub 2} introduced into the He by electrolysis of acid solutions such as in ECHG considerably increases the spectroscopically measured gas temperatures but decreases the analyte line intensities, as shown for Hg.

  1. Study of a new direct current atmospheric pressure glow discharge in helium

    Gielniak, B.; Fiedler, T.; Broekaert, J.A.C.

    2011-01-01

    In this study a new DC-APGD operated in He was developed and characterized. The discharge is operated at 0.9 kV and about 25-35 mA and at a gas flow of 100 ml/min. The source was spectroscopically studied and parameters such as the rotational temperature (T rot ), the excitation temperature (T exc ), the ionization temperature (T ion ) and the electron number density (n e ) were determined. The current-voltage characteristic of the source was studied as well. At optimized conditions the discharge operates in the normal region of the current-voltage characteristic. Rotational and excitation temperatures determined with the use of OH band and Fe I lines as thermometric species were of the order of about 900-1200 and 4500-5500 K, respectively. This indicates that despite of the atmospheric pressure, the discharge is not in LTE. Spatially resolved temperature measurements were performed with axial as well as radial resolution and showed relatively flat profiles. Axially resolved emission intensity profiles for several species such as H, N 2 , N 2 + , OH, He and Hg were determined. It also was found that H 2 introduced into the He by electrolysis of acid solutions such as in ECHG considerably increases the spectroscopically measured gas temperatures but decreases the analyte line intensities, as shown for Hg.

  2. Effect of helium on void formation in nickel

    Brimhall, J.L.; Simonen, E.P.

    1977-01-01

    This study examines the influence of helium on void formation in self-ion irradiated nickel. Helium was injected either simultaneously with, or prior to, the self-ion bombardment. The void microstructure was characterized as a function of helium deposition rate and the total heavy-ion dose. In particular, at 575 0 C and 5 X 10 -3 displacements per atom per second the void density is found to be proportional to the helium deposition rate. The dose dependence of swelling is initially dominated by helium driven nucleation. The void density rapidly saturates after which swelling continues with increasing dose only from void growth. It is concluded that helium promotes void nucleation in nickel with either helium implantation technique, pre-injection or simultaneous injection. Qualitative differences, however, are recognized. (Auth.)

  3. Helium trapping in aluminum and sintered aluminum powders

    Das, S.K.; Kaminsky, M.; Rossing, T.

    1975-01-01

    The surface erosion of annealed aluminum and of sintered aluminum powder (SAP) due to blistering from implantation of 100-keV 4 He + ions at room temperature has been investigated. A substantial reduction in the blistering erosion rate in SAP was observed from that in pure annealed aluminum. In order to determine whether the observed reduction in blistering is due to enhanced helium trapping or due to helium released, the implanted helium profiles in annealed aluminum and in SAP have been studied by Rutherford backscattering. The results show that more helium is trapped in SAP than in aluminum for identical irradiation conditions. The observed reduction in erosion from helium blistering in SAP is more likely due to the dispersion of trapped helium at the large Al-Al 2 O 3 interfaces and at the large grain boundaries in SAP than to helium release

  4. Space shuttle OMS helium regulator design and development

    Wichmann, H.; Kelly, T. L.; Lynch, R.

    1974-01-01

    Analysis, design, fabrication and design verification testing was conducted on the technological feasiblity of the helium pressurization regulator for the space shuttle orbital maneuvering system application. A prototype regulator was fabricated which was a single-stage design featuring the most reliable and lowest cost concept. A tradeoff study on regulator concepts indicated that a single-stage regulator with a lever arm between the valve and the actuator section would offer significant weight savings. Damping concepts were tested to determine the amount of damping required to restrict actuator travel during vibration. Component design parameters such as spring rates, effective area, contamination cutting, and damping were determined by test prior to regulator final assembly. The unit was subjected to performance testing at widely ranging flow rates, temperatures, inlet pressures, and random vibration levels. A test plan for propellant compatibility and extended life tests is included.

  5. Fundamental Experiments at Liquid Helium Temperatures (Low Temperature Studies of Anomalous Surface Shielding and Related Phenomena).

    1984-09-30

    study of the copper surface indicated that the copper oxide layer was approximately 20 Angstroms thick. Hanni and Madey 3 2 have evaluated the...REFERENCES 1. John Bardeen, "Comments on Shielding by Surface States," in Near Zero: New Frontiers of Physics, to be published. 2. R. S. Hanni and...Michel, H. E. Rorschach, and G. T. Trammel, Phys. Rev. 168 (1968), 737. 31. C. Herring, Phys. Rev. 171 (1968), 1361. 32. R. S. Hanni and J.M.J. Madey

  6. Elastic helium scattering studies of ordered overlayers of Ar, Kr, and Xe physisorbed on Ag(111)

    Gibson, K.D.; Cerjan, C.; Light, J.C.; Sibener, S.J.

    1988-01-01

    We describe experiments that measured the angle resolved intensity of He (E/sub i/ = 18 and 66 meV) elastically scattering from the surfaces of rare gas overlayers physisorbed on Ag(111). These studies were done on a layer-by-layer basis for 1, 2, 3, and ∼25 ordered overlayers of Ar, Kr, and Xe. Two types of experiments are described. The first is diffraction, where the scattered He intensity was measured as a function of the detector angle, with the incident polar and azimuthal angles held constant. In the second type of experiment, selective adsorption, we measured the specular intensity as a function of incident angle. The purpose of these experiments was to examine the He--surface potential, to assess the relative contributions that various He--rare gas pair potentials, nonadditive multibody terms, and He--substrate interactions make to the systems studied. The experiments are compared with the results of accurate close-coupling calculations, in order to quantitatively perform these assessments. The comparisons between the selective adsorption data and scattering calculations demonstrate the extreme sensitivity that such measurements have to the He--surface potential. In particular, observable changes in the calculated selective adsorption spectra appear when different He--rare gas potentials are tested, or when various nonadditive terms are included in the potential. The results suggest that further refinements in the He-heavy--rare gas pair potentials may be in order

  7. Agile software development and its compatibility with a document-driven approach? A case study

    Heeager, Lise Tordrup; Nielsen, Peter Axel

    2009-01-01

    however have a desire to adopt agile development processes while maintaining compliance with a quality assurance standard or even a process standard. We have studied the software development process of a Danish pharmaceutical company. For market reasons the company has to comply the US Food and Drug...

  8. Studies of Interactions of Positive Helium Ions with Small Neutrals at Temperatures Below 50K

    Schauer, Martin Michael

    1990-01-01

    Interactions of He^+ ions with small neutrals are important because of their fundamental nature and applicability to other areas of research. In the past, very little work has been done on such systems at very low temperatures (T Boehringer and Arnold (1986) and Johnsen, Chen, and Biondi (1980). A new method of detecting the ions in the trap was also developed and implemented. The Fourier Transform Ion Z-resonance (FTIZR) technique took advantage of an induced coherence in the oscillations of the ions in the trap. This method allowed for measurement of faster ion -neutral reactions. This method was demonstrated by studying the non -resonant charge transfer process ^3He ^+{+}^4He{toatop >=ts}^3He{+}^4He^+. These measurements confirmed that the forward reaction is endothermic by about 1.1 meV.

  9. Status of helium-production reaction studies with a spallation neutron source

    Haight, R.C.; Bateman, F.B.; Chadwick, M.B.

    1994-01-01

    Alpha--particle production cross sections and spectra are being measured at the spallation source of fast neutrons at the Los Alamos Meson Physics Facility (LAMPF). Detectors at angles of 30, 60, 90 and 135 degree are used to identify alpha particles, measure their energy spectra, and indicate the time-of-flight, and hence the energy, of the neutrons inducing the reaction. The useful neutron energy ranges from less than 1 MeV to approximately 50 MeV for the present experimental setup. Targets under study at present include C, N, O, 27 Al, Si, 51 V, 56 Fe, 59 Co, 58,60 Ni, 89 Y and 93 Nb. Results for 59 Co illustrate the capabilities of the approach

  10. Ab initio study of interaction of helium with edge and screw dislocations in tungsten

    Bakaev, Alexander, E-mail: bakaev_vic@mail.ru [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol 2400 (Belgium); Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, Peter the Great St. Petersburg Polytechnic University, 29 Polytekhnicheskaya str., 195251 St. Petersburg (Russian Federation); Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden (Germany); Terentyev, Dmitry [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol 2400 (Belgium); Grigorev, Petr [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol 2400 (Belgium); Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, Peter the Great St. Petersburg Polytechnic University, 29 Polytekhnicheskaya str., 195251 St. Petersburg (Russian Federation); Ghent University, Applied Physics EA17 FUSION-DC, St. Pietersnieuwstraat, 41 B4, B-9000 Gent (Belgium); Posselt, Matthias [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden (Germany); Zhurkin, Evgeny E. [Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, Peter the Great St. Petersburg Polytechnic University, 29 Polytekhnicheskaya str., 195251 St. Petersburg (Russian Federation)

    2017-02-15

    Highlights: • Both screw (SD) and edge dislocations (ED) offer trapping sites for He in tungsten. • He atom is attracted to SD and ED with the interaction energy of ~1.3 and ~3.0 eV, respectively. • The attraction of He to dislocations can contribute to the nucleation of He clusters at high T. - Abstract: The interaction of a single He atom with edge and screw dislocations in tungsten has been studied using ab initio calculations. It was revealed that He is strongly attracted to the core of both dislocations with the interaction energy of −1.3 and −3.0 eV for screw and edge dislocations, respectively, which corresponds to the detrapping temperature in thermal desorption spectroscopy experiments of about 500 K and 1050 K, respectively. The lowest energy positions for He around the dislocation cores are identified and the atomic structures are rationalized on the basis of elasticity theory considerations. Both types of dislocations exhibit a higher binding energy for He as compared to the He-He binding (known as self-trapping) and are weaker traps as compared to a single vacancy. It is, thus, concluded that the strong attraction to dislocation lines can contribute to the nucleation of He clusters in the temperature range which already excludes He self-trapping.

  11. Hydrogen- and helium-implanted silicon: Low-temperature positron-lifetime studies

    Mäkinen, S.; Rajainmäki, H.; Linderoth, Søren

    1991-01-01

    High-purity single-crystal samples of float-zoned Si have been implanted with 6.95-MeV protons and with 25-MeV 3He2 ions at 15 K, and the positron-lifetime technique has been used to identify the defects created in the samples, and to study the effects of H and He on the annealing of point defects...... in Si. The results have been compared with those of proton-irradiated Si. A 100–300-K annealing stage was clearly observed in hydrogen (H+) -implanted Si, and this stage was almost identical to that in the p-irradiated Si. The final annealing state of the H+-implanted Si started at about 400 K......, and it is connected to annealing out of negatively charged divacancy-oxygen pairs. This stage was clearly longer than that for the p-irradiated Si, probably due to the breakup of Si-H bonds at about 550 K. The 100-K annealing stage was not seen with the He-implanted samples. This has been explained by assuming...

  12. Ab initio study of interaction of helium with edge and screw dislocations in tungsten

    Bakaev, Alexander; Terentyev, Dmitry; Grigorev, Petr; Posselt, Matthias; Zhurkin, Evgeny E.

    2017-01-01

    Highlights: • Both screw (SD) and edge dislocations (ED) offer trapping sites for He in tungsten. • He atom is attracted to SD and ED with the interaction energy of ~1.3 and ~3.0 eV, respectively. • The attraction of He to dislocations can contribute to the nucleation of He clusters at high T. - Abstract: The interaction of a single He atom with edge and screw dislocations in tungsten has been studied using ab initio calculations. It was revealed that He is strongly attracted to the core of both dislocations with the interaction energy of −1.3 and −3.0 eV for screw and edge dislocations, respectively, which corresponds to the detrapping temperature in thermal desorption spectroscopy experiments of about 500 K and 1050 K, respectively. The lowest energy positions for He around the dislocation cores are identified and the atomic structures are rationalized on the basis of elasticity theory considerations. Both types of dislocations exhibit a higher binding energy for He as compared to the He-He binding (known as self-trapping) and are weaker traps as compared to a single vacancy. It is, thus, concluded that the strong attraction to dislocation lines can contribute to the nucleation of He clusters in the temperature range which already excludes He self-trapping.

  13. Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

    Wagner, A.

    1978-08-01

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min -1 can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected

  14. Feedback from physical activity monitors is not compatible with current recommendations: A recalibration study.

    Thompson, Dylan; Batterham, Alan M; Peacock, Oliver J; Western, Max J; Booso, Rahuman

    2016-10-01

    Wearable devices to self-monitor physical activity have become popular with individuals and healthcare practitioners as a route to the prevention of chronic disease. It is not currently possible to reconcile feedback from these devices with activity recommendations because the guidelines refer to the amount of activity required on top of normal lifestyle activities (e.g., 150 minutes of moderate-to-vigorous intensity activity per week over-and-above normal moderate-to-vigorous lifestyle activities). The aim of this study was to recalibrate the feedback from self-monitoring. We pooled data from four studies conducted between 2006 and 2014 in patients and volunteers from the community that included both sophisticated measures of physical activity and 10-year risk for cardiovascular disease and type 2 diabetes (n=305). We determined the amount of moderate-to-vigorous intensity activity that corresponded to FAO/WHO/UNU guidance for a required PAL of 1.75 (Total Energy Expenditure/Basal Metabolic Rate). Our results show that, at the UK median PAL, total moderate-to-vigorous intensity physical activity will be around 735 minutes per week (~11% of waking time). We estimate that a 4% increase in moderate-to-vigorous intensity activity will achieve standardised guidance from FAO/WHO/UNU and will require ~1000 minutes of moderate-to-vigorous intensity activity per week. This study demonstrates that feedback from sophisticated wearable devices is incompatible with current physical activity recommendations. Without adjustment, people will erroneously form the view that they are exceeding recommendations by several fold. A more appropriate target from self-monitoring that accounts for normal moderate-to-vigorous lifestyle activities is ~1000 minutes per week, which represents ~15% of waking time. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  15. An electromagnetic compatibility study of cardiac pacemaker to low frequency interferences

    Andretzko, J.P.; Hedjiedj, A.; Babouri, A.; Guendouz, L.; Nadi, M.

    2006-01-01

    This paper presents an experimental study of the behaviour of cardiac pacemaker submitted to low frequency electromagnetic interferences. The method used in this study is progressive. It consists in starting from the target (the cardiac pacemaker), identifying and quantifying the disturbances (the source), and then introducing secondary influencing parameters in stepwise fashion. The general problematic consists in checking this immunity in relation with led disruptions and in relation with beaming disruptions. The experimental approach suggests two kind of tests corresponding to the two studied coupling modes. The first one corresponds to a direct applying of the disruptive signal between the pacemaker terminals. The objective of this phase is to determine the characteristics of the signal (amplitude and frequency) which are detected by the pacemaker and which generate modifications of its operation. In the second phase the pacemaker is subjected to a variable low frequency magnetic field. This last interacts with the pacemaker by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. The objective of this phase is to characterize the signal (magnetic field) likely to generate these disturbances. Tests are carried out on six single chamber pacemaker and five dual chamber pacemaker. The interfering signal frequencies are 50 Hz, 60 Hz, 10 khz and 25 khz. Tracking and programming of the pacemaker housing is achieved with the telemetry system. In this study, the devices have all been configured in inhibited stimulation (S.S.I. or V.V.I. mode according to the international codification), this configuration being the most widespread. The housing stimulates the basic frequency in the absence o f intrinsic activity, the stimulation can be inhibited in each chamber by a

  16. An electromagnetic compatibility study of cardiac pacemaker to low frequency interferences

    Andretzko, J.P.; Hedjiedj, A.; Babouri, A.; Guendouz, L.; Nadi, M. [Nancy-1 Univ. Henri Poincare, Lab. d' Instrumentation Electronique de Nancy, Faculte des Sciences, 54 - Vandoeuvre les Nancy (France)

    2006-07-01

    This paper presents an experimental study of the behaviour of cardiac pacemaker submitted to low frequency electromagnetic interferences. The method used in this study is progressive. It consists in starting from the target (the cardiac pacemaker), identifying and quantifying the disturbances (the source), and then introducing secondary influencing parameters in stepwise fashion. The general problematic consists in checking this immunity in relation with led disruptions and in relation with beaming disruptions. The experimental approach suggests two kind of tests corresponding to the two studied coupling modes. The first one corresponds to a direct applying of the disruptive signal between the pacemaker terminals. The objective of this phase is to determine the characteristics of the signal (amplitude and frequency) which are detected by the pacemaker and which generate modifications of its operation. In the second phase the pacemaker is subjected to a variable low frequency magnetic field. This last interacts with the pacemaker by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. The objective of this phase is to characterize the signal (magnetic field) likely to generate these disturbances. Tests are carried out on six single chamber pacemaker and five dual chamber pacemaker. The interfering signal frequencies are 50 Hz, 60 Hz, 10 khz and 25 khz. Tracking and programming of the pacemaker housing is achieved with the telemetry system. In this study, the devices have all been configured in inhibited stimulation (S.S.I. or V.V.I. mode according to the international codification), this configuration being the most widespread. The housing stimulates the basic frequency in the absence o f intrinsic activity, the stimulation can be inhibited in each chamber by a

  17. Realization of mechanical rotation in superfluid helium

    Gordon, E. B.; Kulish, M. I.; Karabulin, A. V.; Matyushenko, V. I.; Dyatlova, E. V.; Gordienko, A. S.; Stepanov, M. E.

    2017-09-01

    The possibility of using miniaturized low-power electric motors submerged in superfluid helium for organization of rotation inside a cryostat has been investigated. It has been revealed that many of commercial micromotors can operate in liquid helium consuming low power. Turret with 5 sample holders, assembled on the base of stepper motor, has been successfully tested in experiments on the nanowire production in quantized vortices of superfluid helium. Application of the stepper motor made it possible in a single experiment to study the effect of various experimental parameters on the yield and quality of the nanowires. The promises for continuous fast rotation of the bath filled by superfluid helium by using high-speed brushless micromotor were outlined and tested. Being realized, this approach will open new possibility to study the guest particles interaction with the array of parallel linear vortices in He II.

  18. Compatibility studies on Mo-coating systems for nuclear fuel cladding applications

    Koh, Huan Chin; Hosemann, Peter; Glaeser, Andreas M.; Cionea, Cristian

    2017-12-01

    To improve the safety factor of nuclear power plants in accident scenarios, molybdenum (Mo), with its high-temperature strength, is proposed as a potential fuel-cladding candidate. However, Mo undergoes rapid oxidation and sublimation at elevated temperatures in oxygen-rich environments. Thus, it is necessary to coat Mo with a protective layer. The diffusional interactions in two systems, namely, Zircaloy-2 (Zr2) on a Mo tube, and iron-chromium-aluminum (FeCrAl) on a Mo rod, were studied by aging coated Mo substrates in high vacuum at temperatures ranging from 650 °C to 1000° for 1000 h. The specimens were characterized using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and nanoindentation. In both systems, pores in the coating increased in size and number with increasing temperature over time, and cracks were also observed; intermetallic phases formed between the Mo and its coatings.

  19. Study of Oxidizing Agents for Tritium Removal in ITER -Compatible Conditions: Alternatives to Oxygen and Ozone

    Tabares, F. L.; Tafalla, D.; Ferreira, J. A.; Gomez-Aleixandre, C.; Maria Albella, J.; Soria, J.; Rodriguez-Ramos, I.

    2007-01-01

    In the present report, the studies of tritiated carbon-film removal by oxidizing agents other than Oxygen and Ozone in ITER are described. Exposure of laboratory produced a-C:H/D films and tokamak flakes (Asdex Upgrade and Textor) to nitric oxide, water and hydrogen peroxide has been carried out. Temperatures of exposure up to 350 degree centigree were used, and thermal desorption of the samples at temperatures up to 750 degree centigree was performed for sample characterization prior to and after the treatment. Elastic Recoil Detection Analysis (ERDA), Infrared Spectroscopy, XPS and Nano indentation hardness analysis were applied to the characterization of the physical and chemical changes of the samples. This work was done under the EFDA Task 04-1175. (Author) 8 refs

  20. Study of Oxidizing Agents for Tritium Removal in ITER -Compatible Conditions: Alternatives to Oxygen and Ozone

    Tabares, F. L.; Tafalla, D.; Ferreira, J. A.; Gomez-Aleixandre, C.; Maria Albella, J.; Soria, J.; Rodriguez-Ramos, I.

    2007-07-20

    In the present report, the studies of tritiated carbon-film removal by oxidizing agents other than Oxygen and Ozone in ITER are described. Exposure of laboratory produced a-C:H/D films and tokamak flakes (Asdex Upgrade and Textor) to nitric oxide, water and hydrogen peroxide has been carried out. Temperatures of exposure up to 350 degree centigree were used, and thermal desorption of the samples at temperatures up to 750 degree centigree was performed for sample characterization prior to and after the treatment. Elastic Recoil Detection Analysis (ERDA), Infrared Spectroscopy, XPS and Nano indentation hardness analysis were applied to the characterization of the physical and chemical changes of the samples. This work was done under the EFDA Task 04-1175. (Author) 8 refs.

  1. MRI compatibility study of an integrated PET/RF-coil prototype system at 3 T

    Akram, Md Shahadat Hossain; Obata, Takayuki; Suga, Mikio; Nishikido, Fumihiko; Yoshida, Eiji; Saito, Kazuyuki; Yamaya, Taiga

    2017-10-01

    We have been working on the development of a PET insert for existing magnetic resonance imaging (MRI) systems for simultaneous PET/MR imaging, which integrates radiofrequency (RF)-shielded PET detector modules with an RF head coil. In order to avoid interferences between the PET detector circuits and the different MRI-generated electromagnetic fields, PET detector circuits were installed inside eight Cu-shielded fiber-reinforced plastic boxes, and these eight shielded PET modules were integrated in between the eight elements of a 270-mm-diameter and 280-mm-axial-length cylindrical birdcage RF coil, which was designed to be used with a 3-T clinical MRI system. The diameter of the PET scintillators with a 12-mm axial field-of-view became 255 mm, which was very close to the imaging region. In this study, we have investigated the effects of this PET/RF-coil integrated system on the performance of MRI, which include the evaluation of static field (Bo) inhomogeneity, RF field (B1) distribution, local specific absorption rate (SAR) distribution, average SAR, and signal-to-noise ratio (SNR). For the central 170-mm-diameter and 80-mm-axial-length of a homogenous cylindrical phantom (with the total diameter of 200 mm and axial-length of 100 mm), an increase of about a maximum of 3 μT in the Bo inhomogeneity was found, both in the central and 40-mm off-centered transverse planes, and a 5 percentage point increase of B1 field inhomogeneity was observed in the central transverse plane (from 84% without PET to 79% with PET), while B1 homogeneity along the coronal plane was almost unchanged (77%) following the integration of PET with the RF head coil. The average SAR and maximum local SAR were increased by 1.21 and 1.62 times, respectively. However, the SNR study for both spin-echo and gradient-echo sequences showed a reduction of about 70% and 60%, respectively, because of the shielded PET modules. The overall results prove the feasibility of this integrated PET/RF-coil system

  2. Study on cryogenic adsorption capability of trace nitrogen and methane by activated carbon for cooIant helium purification

    Chang Hua; Wu Zongxin

    2014-01-01

    A fixed-bed apparatus with dynamic two-route proportional gas mixing system was designed to investigate the cryogenic adsorption behavior of nitrogen and methane on activated carbon for designing the helium purification system of high-temperature gas-cooled reactors (HTGR). With helium as carrier gas and at the impurity partial pressure of tens Pa, experiments were performed at near atmospheric pressure and by dynamic column breakthrough method at -196°C. The breakthrough curves and desorption curves were measured. By analyzing the breakthrough curve, both the equilibrium adsorption capacity and the kinetic adsorption capacity at breakthrough point were determined. Based on mass-transfer zone model, the experimental breakthrough curves were analyzed. (author)

  3. Complementary study of the internal porous silicon layers formed under high-dose implantation of helium ions

    Lomov, A. A., E-mail: lomov@ftian.ru; Myakon’kikh, A. V. [Russian Academy of Sciences, Institute of Physics and Technology (Russian Federation); Chesnokov, Yu. M. [National Research Centre “Kurchatov Institute” (Russian Federation); Shemukhin, A. A.; Oreshko, A. P. [Moscow State University (Russian Federation)

    2017-03-15

    The surface layers of Si(001) substrates subjected to plasma-immersion implantation of helium ions with an energy of 2–5 keV and a dose of 5 × 10{sup 17} cm{sup –2} have been investigated using high-resolution X-ray reflectivity, Rutherford backscattering, and transmission electron microscopy. The electron density depth profile in the surface layer formed by helium ions is obtained, and its elemental and phase compositions are determined. This layer is found to have a complex structure and consist of an upper amorphous sublayer and a layer with a porosity of 30–35% beneath. It is shown that the porous layer has the sharpest boundaries at a lower energy of implantable ions.

  4. Preliminary study of blood compatibility of PTFE copolymerized with DMAA through gamma rays compared to PET and aflon films

    Queiroz, A.A.A. de; Higa, O.Z.

    1990-01-01

    The new method developed by Imai and Nosa was used for the evaluation of blood compatibility of poly(tetrafluoroethylene) (PTFE) grafted films with N,N - dimethylacrylamide (DMAA). The amount of the formed thrombus was measured gravimetrically at an appropriate interval of time after calcium chloride being added to the ACD blood in contact to the tested material. It was concluded that the method of modifying the polymeric surface of PTFE by grafting the hydrophilic monomer DMAA improved its blood compatibility. (author)

  5. Compatibility studies of copper, brass and cupronickel with Hytherm-500 thermofluid

    Pujar, M.G.; Dayal, R.K.; Gnanamoorthy, J.B.

    1989-01-01

    Carbon steel used as a structural material in thermofluid/water heat exchangers in the Fast Breeder Test Reactor (FBTR) got perforated resulting in leakage. To suggest an alternative better corrosion resistant material for these exchangers, corrosion resistance studies of copper based alloy systems in both a s received and pickled conditions were carried out in the thermofluid medium (Hytherm-500) at room temperature (∼298 K), 373 K and 423 K upto 500 h duration. The tested materials, copper, admiralty brass and 70/30 cupronickel were found to have excellent corrosion resistance in both as-received and pickled conditions. In all the cases corrosion rates decreased with increased duration of exposure. All the above materials showed better corrosion resistance in pickled condition compared to that in as-received condition. The relative corrosion resistance of these three alloys was as follows: admiralty brass > cop per > cupronickel. This trend in the corrosion resistance was observed in both as-received and pickled conditions. In general, the corrosion resistance in pickled condition was found to be better than that in as-received condition. (author). 3 refs., 3 figs., 2 tabs

  6. Compatibility of scientific research and specialty training in general practice. A cross-sectional study.

    Kötter, Thomas; Carmienke, Solveig; Herrmann, Wolfram J

    2014-01-01

    In many departments of General Practice (GP) in Germany, young doctors who are trainees also work as researchers. Often these trainees work part time at the university and part time as a trainee in clinical practice. However, little is known about the situation of the actors involved. The aim of the study was to investigate the perspectives of GP trainees, heads of departments and GP trainers regarding the combination of research and GP training. We conducted a web-based survey with the heads of all German departments of General Practice, GP trainees who also conduct research and their GP trainers. The questionnaires consisted of open and closed questions. The results were analyzed using descriptive statistics and qualitative methods. 28 heads of GP departments and 20 GP trainees responded. The trainees were mostly very satisfied with their situation as a trainee. However, the trainees considered the combination of research and GP training as difficult. The respondents name as problems the coordination of multiple jobs and the lack of credibility given to research in General Practice. They name as solutions research-enabling training programs and uniform requirements in training regarding research. The combination of GP training and scientific research activity is perceived as difficult. However, well-organized and designed programs can improve the quality of the combination.

  7. Study of compatibility of oligo-chitosan and ginkgo bilobal polyprenol influences on micronuclear rates and p53, gadd45 protein expression of radiated mice

    Guo Jianping; Wang Yongli; Wei Jinping; Yang Zhongtian; Liu Chunhui

    2012-01-01

    Study of compatibility of oligo-chitosan and ginkgo bilobal polyprenol (GP) influences on micronuclear rate and p53, gadd45 protein expression of radiated mice. Survival rate and survival time of 30-day-time of radiated mice was studied with the mixture of compatibility of oligo-chitosan and different density of GP. High survival rate of mixture density was screening. Another study on this mixture density was about micronuclear rates of marrow and p53, gadd45 protein of spleen after mice were radiated 12 h. The mixture of 300 mg/kg oligo-chitosan and 5 mg/kg GP could increase remarkably the survival rate and survival time of 30-day-time of radiated mice and degrade micronuclear rates and p53, gadd45 protein expression. Compatibility of oligo-chitosan and GP effectively raise the survival rate of radiated mice. It could proved initially that the mixture has the function of radiation protection. (authors)

  8. Electrons on the surface of liquid helium

    Lambert, D.K.

    1979-05-01

    Spectroscopic techniques were used to study transitions of electrons between bound states in the potential well near a helium surface. The charge density distribution of electrons on the surface was independently obtained from electrical measurements. From the measurements, information was obtained both about the interaction of the bound state electrons with the surface of liquid helium and about local disorder in the positions of electrons on the surface

  9. Study on Off-Design Steady State Performances of Helium Gas Turbo-compressor for HTGR-GT

    Qisen Ren; Xiaoyong Yang; Zhiyong Huang; Jie Wang

    2006-01-01

    The high temperature gas-cooled reactor (HTGR) coupled with direct gas turbine cycle is a promising concept in the future of nuclear power development. Both helium gas turbine and compressor are key components in the cycle. Under normal conditions, the mode of power adjustment is to control total helium mass in the primary loop using gas storage vessels. Meanwhile, thermal power of reactor core is regulated. This article analyzes off-design performances of helium gas turbine and compressors for high temperature gas-cooled reactor with gas turbine cycle (HTGR-GT) at steady state level of electric power adjustment. Moreover, performances of the cycle were simply discussed. Results show that the expansion ratio of turbine decreases as electric power reduces but the compression ratios of compressors increase, efficiencies of both turbine and compressors decrease to some extent. Thermal power does not vary consistently with electric power, the difference between these two powers increases as electric power reduces. As a result of much thermal energy dissipated in the temperature modulator set at core inlet, thermal efficiency of the cycle has a widely reduction under partial load conditions. (authors)

  10. A high resolution helium atom scattering and far infrared study of the dynamics and the lateral potential energy surface of CO molecules chemisorbed on Cu(001)

    Graham, A.P.; Hofmann, F.; Toennies, J.P.; Williams, G.P.; Hirschmugl, C.J.; Ellis, J.

    1998-01-01

    Inelastic helium scattering (HAS) and infrared reflection adsorption spectroscopy (IRAS) have been used to measure the isotope shifts of the frequencies of both the parallel and perpendicular frustrated translation modes, as well as the frustrated rotation mode of CO molecules at on top sites on Cu(001). The measured isotope shifts for four different isotopomers indicates a significant rotational contribution to the parallel frustrated translation (T-mode), where the vibrational amplitude of the oxygen atom is significantly larger than for the carbon atom. Conversely, for the frustrated rotation the vibrational amplitude of the carbon atom was observed to be larger than for the oxygen atom. At surface temperatures above T s =100 K a careful analysis of the peak shape of the HAS quasielastic peak shows a small broadening, which is attributed to a rapid diffusion of the CO molecules. The measured dynamic diffusion barrier of 31±10 meV is compatible with the shape of the potential at the on-top site and makes it possible to extend the potential energy surface to the region between the on-top sites. copyright 1998 American Institute of Physics

  11. Compatibility of stainless steels and lithiated ceramics with beryllium

    Flament, T.; Fauvet, P.; Sannier, J.

    1988-07-01

    The introduction of beryllium as a neutron multiplier in ceramic blankets of thermonuclear fusion reactors may give rise to the following compatibility problems: (i) oxidation of Be by ceramics (lithium aluminate and silicates) or by water vapour; (ii) interaction between beryllium and austenitic and martensitic steels. The studies were done in contact tests under vacuum and in tests under wet sweeping helium. The contact tests under vacuum have revealed that the interaction of beryllium with ceramics seems to be low up to 700°C, the interaction of beryllium with steels is significant and is characterized by the formation of a diffusion layer and of a brittle Be-Fe-Ni compound. With type 316 L austenitic steel, this interaction appears quite large at 600°C whereas it is noticeable only at 700°C with martensitic steels. The experiments carried out with sweeping wet helium at 600°C have evidenced a slight oxidation of beryllium due to water vapour which can be enhanced in the front of uncompletely dehydrated ceramics.

  12. Thermal stability and environmental compatibility of Inconel 617

    Kimball, O.F.

    1989-01-01

    The thermal stability and environmental compatibility of Inconel 617, a prime nuclear process heat steam reformer candidate alloy, are described in this paper. This commercially available wrought nickel-base alloy has excellent high-temperature strength but is subject to loss of toughness and ductility due to thermal instability. Work done to improve the thermal stability of this alloy is discussed. Room-temperature tensile and toughness data and microstructural information for Inconel 617 specimens exposed at elevated temperatures are presented. Preliminary data indicate that controlling the chemistry of Inconel 617 can provide a substantial improvement in thermal stability. Preliminary work to define the range of high-temperature gas-cooled reactor (HTGR) primary coolant compositions within which minimal deleterious gas/metal reactions occur with Inconel 617 is described. Within this gas chemistry range a stable surface oxide forms and only slight carburization occurs. In other gas chemistry ranges, rapid carburization or decarburization can occur. The gas corrosion experiments discussed are part of a series of relatively short-term exposures to HTGR helium in which the effects of different H 2 O concentrations (0.01 to 1.0 Pa) were determined as a function of the systematic variation of a second constituent (CO and CH 4 for this work) in the test gas. The composition of the basic HTGR helium was 40 Pa H 2 , 4 Pa CO, 0.02 Pa CO 2 , 2 Pa CH 4 in helium at 0.2 MPa. Two other CO levels (1 and 12 Pa) and one additional CH 4 level (0.63 Pa) were used in these experiments. Experimental exposure methods are discussed and the results of gas-metal interaction studies are presented. These results include carbon analyses and optical and scanning electron microscopy to determine the morphology and type of surface and subsurface microstructures. (author). 15 refs, 6 figs, 5 tabs

  13. Diffuse helium and hydrogen degassing to reveal hidden geothermal resources in oceanic volcanic islands: The Canarian archipelago case study

    Rodríguez, Fátima; Pérez, Nemesio M.; Padrón, Eleazar; Dionis, Samara; López, Gabriel; Melián, Gladys V.; Asensio-Ramos, María; Hernández, Pedro A.; Padilla, German; Barrancos, José; Marrero, Rayco; Hidalgo, Raúl

    2015-04-01

    During geothermal exploration, the geochemical methods are extensively used and play a major role in both exploration and exploitation phases. They are particularly useful to assess the subsurface temperatures in the reservoir, the origin of the fluid, and flow directions within the reservoir. The geochemical exploration is based on the assumption that fluids on the surface reflect physico-chemical and thermal conditions in the geothermal reservoir at depth. However, in many occasions there is not any evidence of endogenous fluids manifestations at surface, that traditionally evidence the presence of an active geothermal system. Discovery of new geothermal systems will therefore require exploration of areas where the resources are either hidden or lie at great depths. Geochemical methods for geothermal exploration at these areas must include soil gas surveys, based on the detection of anomalously high concentrations of some hydrothermal gases in the soil atmosphere, generally between 40 cm and 1 meter depth from the surface. Among soil gases, particularly interest has been addressed to non-reactive and/or highly mobile gases. They offer important advantages for the detection of vertical permeability structures, because their interaction with the surrounding rocks or fluids during the ascent toward the surface is minimum. This is the case of helium (He) and hydrogen (H2), that have unique characteristics as a geochemical tracer, owing to their chemical and physical characteristics. Enrichments of He and H2 observed in the soil atmosphere can be attributed almost exclusively to migration of deep-seated gas toward the surface. In this work we show the results of soil gas geochemistry studies, focused mainly in non-reactive and/or highly mobile gases as He and H2, in five minning grids at Tenerife and Gran Canaria, Canay Islands, Spain, during 2011-2014. The primary objective was to use different geochemical evidences of deep-seated gas emission to sort the possible

  14. Compatible Lie Bialgebras

    Wu Ming-Zhong; Bai Cheng-Ming

    2015-01-01

    A compatible Lie algebra is a pair of Lie algebras such that any linear combination of the two Lie brackets is a Lie bracket. We construct a bialgebra theory of compatible Lie algebras as an analogue of a Lie bialgebra. They can also be regarded as a “compatible version” of Lie bialgebras, that is, a pair of Lie bialgebras such that any linear combination of the two Lie bialgebras is still a Lie bialgebra. Many properties of compatible Lie bialgebras as the “compatible version” of the corresponding properties of Lie bialgebras are presented. In particular, there is a coboundary compatible Lie bialgebra theory with a construction from the classical Yang–Baxter equation in compatible Lie algebras as a combination of two classical Yang–Baxter equations in Lie algebras. Furthermore, a notion of compatible pre-Lie algebra is introduced with an interpretation of its close relation with the classical Yang–Baxter equation in compatible Lie algebras which leads to a construction of the solutions of the latter. As a byproduct, the compatible Lie bialgebras fit into the framework to construct non-constant solutions of the classical Yang–Baxter equation given by Golubchik and Sokolov. (paper)

  15. Development of a new, rapid and sensitive HPTLC method for estimation of Milnacipran in bulk, formulation and compatibility study

    Gautam Singhvi

    2017-05-01

    Full Text Available A simple, sensitive and rapid high performance thin layer chromatographic (HPTLC method has been developed and validated for quantitative determination of Milnacipran Hydrochloride (MIL in bulk and formulations. The chromatographic development was carried out on HPTLC plates precoated with silica gel 60 F254 using a mixture of acetonitrile, water and ammonia (6:0.6:1.6 (v/v/v as mobile phase. Detection was carried out densitometrically at 220 nm. The Rf value of drug was found to be 0.63 ± 0.02. The method was validated as per ICH guideline with respect to linearity, accuracy, precision, robustness etc. The calibration curve was found to be linear over a range of 100–1000 ng μL−1 with a regression coefficient of 0.999. The accuracy was found to be very high (99.12–100.87%. %RSD values for intra-day and inter-day variation were not more than 1.43. The method has demonstrated high sensitivity and specificity. The method was applied for compatibility studies also. The method is new, simple and economic for routine estimation of MIL in bulk, preformulation studies and pharmaceutical formulation to help the industries as well as researchers for their sensitive determination of MIL rapidly at low cost in routine analysis.

  16. Examination of the Compatibility of the Questions Used by Social Studies Teachers in the Class with the Program Achievements According to the SOLO Taxonomy

    Keskin, Yusuf; Keskin, Sevgi C.; Kirtel, Aysegül

    2016-01-01

    The purpose of this study is to examine the compatibility of the questions used by the social studies branch teachers in the level of 6th and 7th grade with the achievements included in the teaching program. Structure of observed learning outcome (SOLO) taxonomy, which was presented by Biggs and Colis (1982) as an alternative to Bloom's cognitive…

  17. Investigation of impurity-helium solid phase decomposition

    Boltnev, R.E.; Gordon, E.B.; Krushinskaya, I.N.; Martynenko, M.V.; Pel'menev, A.A.; Popov, E.A.; Khmelenko, V.V.; Shestakov, A.F.

    1997-01-01

    The element composition of the impurity-helium solid phase (IHSP), grown by injecting helium gas jet, involving Ne, Ar, Kr, and Xe atoms and N 2 molecules, into superfluid helium, has been studied. The measured stoichiometric ratios, S = N H e / N I m, are well over the values expected from the model of frozen together monolayer helium clusters. The theoretical possibility for the freezing of two layers helium clusters is justified in the context of the model of IHSP helium subsystem, filled the space between rigid impurity centers. The process of decomposition of impurity-helium (IH)-samples taken out of liquid helium in the temperature range 1,5 - 12 K and the pressure range 10-500 Torr has been studied. It is found that there are two stages of samples decomposition: a slow stage characterized by sample self cooling and a fast one accompanied by heat release. These results suggest, that the IHSP consists of two types of helium - weakly bound and strongly bound helium - that can be assigned to the second and the first coordination helium spheres, respectively, formed around heavy impurity particles. A tendency for enhancement of IHSP thermo stability with increasing the impurity mass is observed. Increase of helium vapor pressure above the sample causes the improvement of IH sample stability. Upon destruction of IH samples, containing nitrogen atoms, a thermoluminescence induced by atom recombination has been detected in the temperature region 3-4,5 K. This suggests that numerous chemical reactions may be realized in solidified helium

  18. Preliminary study on application of Pd composite membrane in helium purification system of high-temperature gas-cooled reactor

    Cai Jianhua; Yang Xiaoyong; Wang Jie; Yu Suyuan

    2008-01-01

    Helium purification system (HPS) is the main part of the helium auxiliary system of high-temperature gas-cooled reactors (HTGR), also in fusion reactors. Some exploratory work was carried out on the application of Pd composite membrane in the separation of He and H 2 . A typical single stripper permeator with recycle (SSP) system was designed, based on the design parameters of a small scale He purification test system CIGNE in CADARACHE, CEA, France, and finite element analysis method was used to solve the model. The total length of membrane module is fixed to 0.5 m. The results show that the concentration of H 2 is found to reduce from 1 000 μL/L in feed gas to 5 μL/L in the product He (the upper limitation of HPS in HTGR). And the molar ratio of product He to feed gas is 96.18% with the optimized ratio of sweep gas to retentive gas 0. 3970. It's an exponential distribution of H 2 concentration along the membrane module. The results were also compared with the other two popular designs, two stripper in series permeator (TSSP) and continuous membrane column (CMC). (authors)

  19. A Molecular dynamics study of helium bubble stability during high-energy displacement cascades in alpha-iron

    Pu, Jin; Yang, Li; Zu, Xiaotao; Gao, Fei

    2007-01-01

    The interactions of high-energy displacement cascades with helium bubbles in a-Fe are investigated using molecular dynamics simulations. Initial bubbles with the volumes of 212 and 636 (angstrom)3 are considered, and the helium-to-vacancy (He/V) ratio in the bubbles varies from 0.5 to 3. Primary knock-on atom (PKA) energy, Ep, is up to 40 keV. The results show that the change of nm-sized He bubbles due to displacement cascade does not depend much on the bubble size, but rather on the He/V ratio and the recoil energy. For the initial He/V ratio less than 1, the size of the bubbles decreases with increasing PKA energy, but the He/V ratio increases. However, for the initial He/V ratio of 3, the size of the bubbles increases, and the He/V ratio decreases with PKA energy. For the initial He/V ratio of 1, the ratio of the small bubble decreases slightly, but the ratio of the large bubble remains unchanged for lower PKA energy, and increases slightly for higher PKA energy. The reasons for these observed phenomena have been explained

  20. Helium refrigerator for 'SULTAN'

    Arpagaus, M.; Erlach, H.; Quack, H.

    1984-01-01

    The authors describe the helium refrigerator designed for the SULTAN test facility. SULTAN (Supraleiter-Testanlage) is intended to serve for the developments and testing of high field superconducting magnets. These magnets are needed mainly for future applications in nuclear fusion. (Auth.)

  1. Cosmological helium production simplified

    Bernstein, J.; Brown, L.S.; Feinberg, G.

    1988-01-01

    We present a simplified model of helium synthesis in the early universe. The purpose of the model is to explain clearly the physical ideas relevant to the cosmological helium synthesis, in a manner that does not overlay these ideas with complex computer calculations. The model closely follows the standard calculation, except that it neglects the small effect of Fermi-Dirac statistics for the leptons. We also neglect the temperature difference between photons and neutrinos during the period in which neutrons and protons interconvert. These approximations allow us to express the neutron-proton conversion rates in a closed form, which agrees to 10% accuracy or better with the exact rates. Using these analytic expressions for the rates, we reduce the calculation of the neutron-proton ratio as a function of temperature to a simple numerical integral. We also estimate the effect of neutron decay on the helium abundance. Our result for this quantity agrees well with precise computer calculations. We use our semi-analytic formulas to determine how the predicted helium abundance varies with such parameters as the neutron life-time, the baryon to photon ratio, the number of neutrino species, and a possible electron-neutrino chemical potential. 19 refs., 1 fig., 1 tab

  2. Retention of hydrogen isotopes and helium in nickel

    Okada, Mitsumasa; Sato, Rikiya; Yamaguchi, Kenji; Yamawaki, Michio [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab.

    1996-10-01

    In the present study, a thin foil of nickel was irradiated by H{sub 2}{sup +}, D{sub 2}{sup +} and He{sup +} to a fluence of 1.2-6.0x10{sup 20}/m{sup 2} using the TBTS (Tritium Beam Test System) apparatus. The thermal desorption spectroscopy (TDS) technique was employed to evaluate the total amount of retained hydrogen isotope and helium atoms in nickel. In the spectra, two peaks appeared at 440-585K and 720-735K for helium. Hydrogen isotopes irradiation after helium preirradiation were found to enhance the helium release and to decrease the peak temperatures. Helium irradiation after hydrogen isotopes preirradiation were found to enhance the helium release, but the peak temperature showed little difference from that without preirradiation. (author)

  3. Experimental Validation of the LHC Helium Relief System Flow Modeling

    Fydrych, J; Riddone, G

    2006-01-01

    In case of simultaneous resistive transitions in a whole sector of magnets in the Large Hadron Collider, the helium would be vented from the cold masses to a dedicated recovery system. During the discharge the cold helium will eventually enter a pipe at room temperature. During the first period of the flow the helium will be heated intensely due to the pipe heat capacity. To study the changes of the helium thermodynamic and flow parameters we have simulated numerically the most critical flow cases. To verify and validate numerical results, a dedicated laboratory test rig representing the helium relief system has been designed and commissioned. Both numerical and experimental results allow us to determine the distributions of the helium parameters along the pipes as well as mechanical strains and stresses.

  4. Helium bubble bursting in tungsten

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    2013-01-01

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz

  5. Femtosecond spectroscopy on alkali-doped helium nanodroplets; Femtosekundenspektroskopie an alkalidotierten Helium-Nanotroepfchen

    Claas, P.

    2006-01-15

    In the present thesis first studies on the short-time dynamics in alkali dimers and microclusters, which were bound on the surface of superfluid helium droplets, were presented. The experiments comprehended pump-probe measurements on the fs scale on the vibration dynamics on the dimers and on the fragmentation dynamics on the clusters. Generally by the studies it was shown that such extremely short slopes can also be observed on helium droplets by means of the femtosecond spectroscopy.

  6. High-temperature helium-loop facility

    Tokarz, R.D.

    1981-09-01

    The high-temperature helium loop is a facility for materials testing in ultrapure helium gas at high temperatures. The closed loop system is capable of recirculating high-purity helium or helium with controlled impurities. The gas loop maximum operating conditions are as follows: 300 psi pressure, 500 lb/h flow rate, and 2100 0 F temperature. The two test sections can accept samples up to 3.5 in. diameter and 5 ft long. The gas loop is fully instrumented to continuously monitor all parameters of loop operation as well as helium impurities. The loop is fully automated to operate continuously and requires only a daily servicing by a qualified operator to replenish recorder charts and helium makeup gas. Because of its versatility and high degree of parameter control, the helium loop is applicable to many types of materials research. This report describes the test apparatus, operating parameters, peripheral systems, and instrumentation system. The experimental capabilities and test conand presents the results that have been obtained. The study has been conducted using a four-phase approach. The first phase develops the solution to the steady-state radon-diffusion equation in one-dimensieered barriers; disposal charge analysis; analysis of spent fuel policy implementation; spent f water. Field measurements and observations are reported for each site. Analytical data and field measurements are presented in tables and maps. Uranium concentrations in the sediments which were above detection limits ranged from 0.10 t 51.2 ppM. The mean of the logarithms of the uranium concentrations was 0.53. A group of high uranium concentrations occurs near the junctions of quadrangles AB, AC, BB, a 200 mK. In case 2), x-ray studies of isotopic phase separation in 3 He-- 4 He bcc solids were carried out by B. A. Fraass

  7. Dipole moments of molecules solvated in helium nanodroplets

    Stiles, Paul L.; Nauta, Klaas; Miller, Roger E.

    2003-01-01

    Stark spectra are reported for hydrogen cyanide and cyanoacetylene solvated in helium nanodroplets. The goal of this study is to understand the influence of the helium solvent on measurements of the permanent electric dipole moment of a molecule. We find that the dipole moments of the helium solvated molecules, calculated assuming the electric field is the same as in vacuum, are slightly smaller than the well-known gas-phase dipole moments of HCN and HCCCN. A simple elliptical cavity model quantitatively accounts for this difference, which arises from the dipole-induced polarization of the helium

  8. Cooling performance of helium-gas/water coolers in HENDEL

    Inagaki, Yoshiyuki; Takada, Shoji; Hayashi, Haruyoshi; Kobayashi, Toshiaki; Ohta, Yukimaru; Shimomura, Hiroaki; Miyamoto, Yoshiaki

    1994-01-01

    The helium engineering demonstration loop (HENDEL) has four helium-gas/water coolers where the cooling water flows in the tubes and helium gas on the shell side. Their cooling performance was studied using the operational data from 1982 to 1991. The heat transfer of helium gas on the shell was obtained for segmental and step-up baffle type coolers. Also, the change with operation time was investigated. The cooling performance was lowered by the graphite powder released from the graphite components for several thousand hours and thereafter recovered because the graphite powder from the components was reduced and the powder in the cooler shell was blown off during the operation. (orig.)

  9. Helium Exhaust Studies in H-Mode Discharges in the DIII-D Tokamak Using an Argon-Frosted Divertor Cryopump

    Wade, M.R.; Hillis, D.L.; Hogan, J.T.; Mahdavi, M.A.; Maingi, R.; West, W.P.; Brooks, N.H.; Burrell, K.H.; Groebner, R.J.; Jackson, G.L.; Klepper, C.C.; Laughon, G.; Menon, M.M.; Mioduszewski, P.K.

    1995-01-01

    The first experiments demonstrating exhaust of thermal helium in a diverted, H-mode deuterium plasma have been performed on the DIII-D tokamak. The helium, introduced via gas puffing, is observed to reach the plasma core, and then is readily removed from the plasma with a time constant of ∼10--20 energy-confinement times by an in-vessel cryopump conditioned with argon frosting. Detailed analysis of the helium profile evolution suggests that the exhaust rate is limited by the exhaust efficiency of the pump (∼5%) and not by the intrinsic helium-transport properties of the plasma

  10. Studies on MHD pressure drop and heat transfer of helium-lithium annular-mist flow in a transverse magnetic field

    Inoue, Akira; Aritomi, Masanori; Takahashi, Minoru; Matsuzaki, Mitsuo; Narita, Yoshihito; Yano, Toshikazu.

    1987-01-01

    Pressure drop and heat transfer coefficient of helium-lithium annular-mist flow in a rectangular duct were investigated experimentally under a transverse magnetic field at system pressure of 0.2 MPa. A ratio of MHD pressure drop to that of non-magnetic field increases with magnetic flux density and a mass flow rate ratio of lithium to helium in low helium velocity region. However, as increasing the helium velocity, the increment of MHD pressure drop with the magnetic flux density is much reduced and then becomes almost zero. At this condition, the MHD pressure drop of the annular-mist flow becomes much smaller than that of lithium single phase flow with the same lithium mass flow at the high magnetic flux density. Heat transfer coefficient ratio of the helium-lithium annular-mist flow to helium single phase in the non-magnetic field is well correlated by a ratio of the mass flow rate of lithium to helium. The heat transfer coefficient in the magnetic field increases with the magnetic flux density and then terminates at a certain value depending on the mass flow rate ratio and the helium velocity. These characteristics of the MHD pressure drop and the heat transfer in the magnetic field suggest that the helium-lithium annular-mist flow is effectively applicable to cooling of the high heat flux wall in a strong magnetic field like a first wall of a magnetic confinement fusion reactors. (author)

  11. Blood compatibility--a perspective.

    Ratner, B D

    2000-01-01

    This perspective on blood- materials interactions is intended to introduce the set of papers stemming from the symposium, "Devices and Diagnostics in Contact with Blood: Issues in Blood Compatibility at the Close of the 20th Century," organized on August 4-6, 1999 at the University of Washington by the University of Washington Engineered Biomaterials (UWEB) Engineering Research Center. This article outlines some of the history of blood contacting materials, overviews the work that has originated at the University of Washington over the past 28 years, speculates on the origins of the controversies on blood compatibility and considers the issues that should be addressed in future studies.

  12. Quantum fluid dynamics based current-density functional study of a helium atom in a strong time-dependent magnetic field

    Vikas

    2011-01-01

    Evolution of the helium atom in a strong time-dependent (TD) magnetic field (B) of strength up to 10 11 G is investigated through a quantum fluid dynamics (QFD) based current-density functional theory (CDFT). The TD-QFD-CDFT computations are performed through numerical solution of a single generalized nonlinear Schroedinger equation employing vector exchange-correlation potentials and scalar exchange-correlation density functionals that depend both on the electronic charge-density and the current-density. The results are compared with that obtained from a B-TD-QFD-DFT approach (based on conventional TD-DFT) under similar numerical constraints but employing only scalar exchange-correlation potential dependent on electronic charge-density only. The B-TD-QFD-DFT approach, at a particular TD magnetic field-strength, yields electronic charge- and current-densities as well as exchange-correlation potential resembling with that obtained from the time-independent studies involving static (time-independent) magnetic fields. However, TD-QFD-CDFT electronic charge- and current-densities along with the exchange-correlation potential and energy differ significantly from that obtained using B-TD-QFD-DFT approach, particularly at field-strengths >10 9 G, representing dynamical effects of a TD field. The work concludes that when a helium atom is subjected to a strong TD magnetic field of order >10 9 G, the conventional TD-DFT based approach differs 'dynamically' from the CDFT based approach under similar computational constraints. (author)

  13. Advanced Heat Transfer Studies in Superfluid Helium for Large-scale High-yield Production of Superconducting Radio Frequency Cavities

    Peters, Benedikt J; Schirm, Karl-Martin; Koettig, Torsten

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches in superconducting radio frequency cavities. In the presented work the occurring thermal effects during such events are investigated both theoretically and experimentally. In the theoretical part the entire heat transfer process from the heat generation to the detection is covered. The experimental part focuses on the effects in superfluid helium. Previous publications observed the detection of an OST signal that was faster than the second sound velocity. This fast propagation could be verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound was linked to OST signals for the first time, which improves the understanding of the OST signal and allows to gather information about the heating pulse. Additionally, OSTs were used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resol...

  14. Experimental study on the ( mu /sup 4/He)/sub 2S//sup +/ metastable system in helium gas

    Bertin, A; Duclos, J; Gastaldi, Ugo; Gorini, G; Neri, G; Picard, J; Pitzurra, O; Placci, A; Polacco, E; Torelli, G; Vitale, A; Zavattini, E

    1975-01-01

    The authors report the results of an experimental investigation on the properties of the ( mu He)/sub 2S//sup +/ metastable muonic system, which was performed stopping negative muons in a pure helium target at pressures ranging from 10 to 50 atm, and observing the total yield and the differential time distribution of the X-rays released in delayed coincidence with the arrival of muons. At each pressure P, information was obtained on the following quantities: a) the total disappearance rate lambda /sub 2S, tot/(P) of the ( mu He)/sub 2S//sup +/ system, b) the disappearance rates lambda /sub A/(P) and lambda /sub St/(P) of the ( mu He)/sub 2S//sup +/ system for external Auger effect and Stark-mixing collisions. (35 refs).

  15. Steady state heat transfer experimental studies of LHC superconducting cables operating in cryogenic environment of superfluid helium

    Santandrea, Dario; Tuccillo, Raffaele; Granieri, Pier Paolo

    The heat management is a basic and fundamental aspect of the superconducting magnets used in the CERN Large Hadron Collider. Indeed, the coil temperature must be kept below the critical value, despite the heat which can be generated or deposited in the magnet during the normal operations. Therefore, this thesis work aims at determining the heating power which can be extracted from the superconducting cables of the LHC, specially through their electrical insulation which represents the main thermal barrier. An experimental measurement campaign in superfluid helium bath was performed on several samples reproducting the main LHC magnets. The heating power was generated in the sample by Joule heating and the temperature increase was measured by means of Cernox bare chip and thermocouples. An innovative instrumentation technique which also includes the in-situ calibration of the thermocouples was developed. A thorough uncertainty analysis on the overall measurement chain concluded the experimental setup. The prese...

  16. Functional quality of MR-compatible automatic biopsy guns compared with conventional ferromagnetic biopsy systems. An in vitro study

    Langen, H.J.; Landwehr, P.

    2001-01-01

    Comparative evaluation of specimens obtained with different MR-compatible biopsy systems and a conventional ferromagnetic system. Methods: Biopsies of a pig liver were performed post-mortem with three different MR-compatible (Somatex; E-Z-EM; Daum) and one conventional biopsy system (Somatex), five with each device. The specimens were measured and the histopathological quality was graded on a scale from 0 (no tissue) to 9 (best). The tip of the needle was examined with an electron microscope before and after biopsy to demonstrate abrasion. Results: The histopathological score between the first and fifth specimen taken with one biopsy device showed no significant difference. The conventional system yielded significantly better results in nearly all categories (p 2 ) were significantly smaller than those from the conventional system (9.98 mm 2 ). The needle tip abrasion of the different biopsy systems determined by electron microscopy showed no substantial difference. (orig.) [de

  17. Magnetic resonance-compatible robotic and mechatronics systems for image-guided interventions and rehabilitation: a review study.

    Tsekos, Nikolaos V; Khanicheh, Azadeh; Christoforou, Eftychios; Mavroidis, Constantinos

    2007-01-01

    The continuous technological progress of magnetic resonance imaging (MRI), as well as its widespread clinical use as a highly sensitive tool in diagnostics and advanced brain research, has brought a high demand for the development of magnetic resonance (MR)-compatible robotic/mechatronic systems. Revolutionary robots guided by real-time three-dimensional (3-D)-MRI allow reliable and precise minimally invasive interventions with relatively short recovery times. Dedicated robotic interfaces used in conjunction with fMRI allow neuroscientists to investigate the brain mechanisms of manipulation and motor learning, as well as to improve rehabilitation therapies. This paper gives an overview of the motivation, advantages, technical challenges, and existing prototypes for MR-compatible robotic/mechatronic devices.

  18. Helium-induced hardening effect in polycrystalline tungsten

    Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

    2017-09-01

    In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

  19. Case Studies in Crewed Spacecraft Environmental Control and Life Support System Process Compatibility and Cabin Environmental Impact

    Perry, J. L.

    2017-01-01

    Contamination of a crewed spacecraft's cabin environment leading to environmental control and life support system (ECLSS) functional capability and operational margin degradation or loss can have an adverse effect on NASA's space exploration mission figures of merit-safety, mission success, effectiveness, and affordability. The role of evaluating the ECLSS's compatibility and cabin environmental impact as a key component of pass trace contaminant control is presented and the technical approach is described in the context of implementing NASA's safety and mission success objectives. Assessment examples are presented for a variety of chemicals used in vehicle systems and experiment hardware for the International Space Station program. The ECLSS compatibility and cabin environmental impact assessment approach, which can be applied to any crewed spacecraft development and operational effort, can provide guidance to crewed spacecraft system and payload developers relative to design criteria assigned ECLSS compatibility and cabin environmental impact ratings can be used by payload and system developers as criteria for ensuring adequate physical and operational containment. In additional to serving as an aid for guiding containment design, the assessments can guide flight rule and procedure development toward protecting the ECLSS as well as approaches for contamination event remediation.

  20. Applying Climate Compatible Development and economic valuation to coastal management: A case study of Kenya's mangrove forests.

    Huxham, Mark; Emerton, Lucy; Kairo, James; Munyi, Fridah; Abdirizak, Hassan; Muriuki, Tabitha; Nunan, Fiona; Briers, Robert A

    2015-07-01

    Mangrove forests are under global pressure. Habitat destruction and degradation persist despite longstanding recognition of the important ecological functions of mangroves. Hence new approaches are needed to help stakeholders and policy-makers achieve sound management that is informed by the best science. Here we explore how the new policy concept of Climate Compatible Development (CCD) can be applied to achieve better outcomes. We use economic valuation approaches to combine socio-economic data, projections of forest cover based on quantitative risk mapping and storyline scenario building exercises to articulate the economic consequences of plausible alternative future scenarios for the mangrove forests of the South Kenya coast, as a case study of relevance to many other areas. Using data from 645 household surveys, 10 focus groups and 74 interviews conducted across four mangrove sites, and combining these with information on fish catches taken at three landing sites, a mangrove carbon trading project and published data allowed us to make a thorough (although still partial) economic valuation of the forests. This gave a current value of the South Coast mangroves of USD 6.5 million, or USD 1166 ha(-1), with 59% of this value on average derived from regulating services. Quantitative risk mapping, projecting recent trends over the next twenty years, suggests a 43% loss of forest cover over that time with 100% loss at the most vulnerable sites. Much of the forest lost between 1992 and 2012 has not been replaced by high value alternative land uses hence restoration of these areas is feasible and may not involve large opportunity costs. We invited thirty eight stakeholders to develop plausible storyline scenarios reflecting Business as Usual (BAU) and CCD - which emphasises sustainable forest conservation and management - in twenty years time, drawing on local and regional expert knowledge of relevant policy, social trends and cultures. Combining these scenarios with

  1. Evaluation of group A1B erythrocytes converted to type as group O: studies of markers of function and compatibility

    Gao, Hong-Wei; Zhuo, Hai-Long; Zhang, Xue; Ji, Shou-Ping; Tan, Ying-Xia; Li, Su-Bo; Jia, Yan-Jun; Xu, Hua; Wu, Qing-Fa; Yun, Zhi-Min; Luo, Qun; Gong, Feng

    2016-01-01

    Background Enzymatic conversion of blood group A1B red blood cells (RBC) to group O RBC (ECO) was achieved by combined treatment with α-galactosidase and α-N-acetylgalactosaminidase. The aim of this study was to evaluate the function and safety of these A1B-ECO RBC in vitro. Materials and methods A 20% packed volume of A1B RBC was treated with enzymes in 250 mM glycine buffer, pH 6.8. The efficiency of the conversion of A and B antigen was evaluated by traditional typing in test tubes, gel column agglutination technology and fluorescence-activated cell sorting (FACS) analysis. The physiological and metabolic parameters of native and ECO RBC were compared, including osmotic fragility, erythrocyte deformation index, levels of 2,3-diphosphoglycerate, ATP, methaemoglobin, free Na+, and free K+. The morphology of native and ECO RBC was observed by scanning electron microscopy. Residual α-galactosidase or α-N-acetylgalactosaminidase in A1B-ECO RBC was detected by double-antibody sandwich ELISA method. Manual cross-matching was applied to ensure blood compatibility. Results The RBC agglutination tests and FACS results showed that A1B RBC were efficiently converted to O RBC. Functional analysis suggested that the conversion process had little impact on the physiological and metabolic parameters of the RBC. The residual amounts of either α-galactosidase or α-N-acetylgalactosaminidase in the A1B-ECO RBC were less than 10 ng/mL of packed RBC. About 18% of group B and 55% of group O sera reacted with the A1B-ECO RBC in a sensitive gel column cross-matching test. Discussion The conversion process does not appear to affect the morphological, physiological or metabolic parameters of A1B-ECO RBC. However, the A1B-ECO RBC still reacted with some antigens. More research on group O and B sera, which may partly reflect the complexity of group A1 the safety of A1B-ECO RBC is necessary before the application of these RBC in clinical transfusion. PMID:26509826

  2. Compatibility of Mating Preferences

    Bingol, Haluk O.; Basar, Omer

    2016-01-01

    Human mating is a complex phenomenon. Although men and women have different preferences in mate selection, there should be compatibility in these preferences since human mating requires agreement of both parties. We investigate how compatible the mating preferences of men and women are in a given property such as age, height, education and income. We use dataset of a large online dating site (N = 44, 255 users). (i) Our findings are based on the "actual behavior" of users trying to find a dat...

  3. Electromagnetic compatibility in power electronics

    Costa , François; Revol , Bertrand

    2014-01-01

    Scientists largely attribute the recent deterioration of the electromagnetic environment to power electronics. This realization has spurred the study of methodical approaches to electromagnetic compatibility designs as explored in this text. The book addresses major challenges, such as handling numerous parameters vital to predicting electro magnetic effects and achieving compliance with line-harmonics norms, while proposing potential solutions.

  4. Role of value compatibility in IT adoption

    Bunker, Deborah; Kautz, Karlheinz; Nguyen, Anne Luu Thanh

    2007-01-01

    Compatibility has been recognised as an important element in the adoption of IT innovations in organisations but as a concept it has been generally limited to technical or functional factors. Compatibility is also significant, however, with regard to value compatibility between the organisation......, and the adopted IT innovation. We propose a framework to determine value compatibility analysing the organisation's and information system's structure, practices and culture, and explore the value compatibility of an organisation with its adopted self-service computer-based information system. A case study......-service acceptance and training issues experienced by the case organisation. These findings add insight into the problems experienced with value compatibility and the adoption of the information systems, and show the potential use of the proposed framework in the detection of such problems.Journal of Information...

  5. Film boiling heat transfer in liquid helium

    Inai, Nobuhiko

    1979-01-01

    The experimental data on the film boiling heat transfer in liquid helium are required for investigating the stability of superconducting wires. On the other hand, liquid helium has the extremely different physical properties as compared with the liquids at normal temperature such as water. In this study, the experiments on pool boiling were carried out, using the horizontal top surface of a 20 mm diameter copper cylinder in liquid helium. For observing individual bubbles, the experiments on film boiling from a horizontal platinum wire were performed separately in liquid nitrogen and liquid helium, and photographs of floating-away bubbles were taken. The author pointed out the considerable upward shift of the boiling curve near the least heat flux point in film boiling from the one given by the Berenson's equation which has been said to agree comparatively well with the data on the film boiling of the liquids at normal temperature, and the reason was investigated. Consequently, a model for film boiling heat transfer was presented. Also one equation expressing the film boiling at low heat flux for low temperature liquids was proposed. It represents well the tendency to shift from Berenson's equation of the experimental data on film boiling at the least heat flux point for liquid helium, liquid nitrogen and water having extremely different physical properties. Some discussions are added at the end of the paper. (Wakatsuki, Y.)

  6. Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets

    Pentlehner, D.; Slenczka, A.

    2015-01-01

    Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (Δν > 100 cm −1 ) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time

  7. Neutral helium beam probe

    Karim, Rezwanul

    1999-10-01

    This article discusses the development of a code where diagnostic neutral helium beam can be used as a probe. The code solves numerically the evolution of the population densities of helium atoms at their several different energy levels as the beam propagates through the plasma. The collisional radiative model has been utilized in this numerical calculation. The spatial dependence of the metastable states of neutral helium atom, as obtained in this numerical analysis, offers a possible diagnostic tool for tokamak plasma. The spatial evolution for several hypothetical plasma conditions was tested. Simulation routines were also run with the plasma parameters (density and temperature profiles) similar to a shot in the Princeton beta experiment modified (PBX-M) tokamak and a shot in Tokamak Fusion Test Reactor tokamak. A comparison between the simulation result and the experimentally obtained data (for each of these two shots) is presented. A good correlation in such comparisons for a number of such shots can establish the accurateness and usefulness of this probe. The result can possibly be extended for other plasma machines and for various plasma conditions in those machines.

  8. Socio-compatible energy policies

    Renn, O.; Albrecht, G.; Kotte, U.; Peters, H.P.; Stegelmann, H.U.

    1985-01-01

    The socio-compatibility project comprises three central analytical elements: 1) The arborescent value analysis: Eminent social groups (such as the trade-unions or the ecological institutes) were questioned on their values and criteria applied to evaluate different energy systems. 2) The energy system and scenario impact analysis: Indicators deduced from the arborescent value analysis serve to approximately cover the value dimensions affected by above criteria. 3) Impact analysis weighing executed by a group of arbitrarily chosen citizens. All reflections considered, it is evident that none of the energy policies discussed may claim the title 'socio-compatible'. The individual, i.e. neither scientist nor politician, cannot decide upon the socio-compatibility of one or the other concept. An altogether socially compatible solution accepted and classified as such by different social groups may only crystallize and be set against different options by the political formation of opinion. The studys' primary concern lies in furnishing information, i.e. aids for politicians having to decide on energy policies. Above all the study aimed at finding out about reactions, social protest, opposition or approval to be coped with by those who, having the say in political matters, want to speak up for one of the energy policies under public discussion. (orig./HSCH) [de

  9. A study on nuclear heat load tolerable for NET/TF coils cooled by internal flow of helium II

    Hofmann, A.

    1988-02-01

    NbTi cables cooled by internal flow of superfluid helium are considered an option for the design of NET/TF coils with about 11 T peak fields. Starting from an available winding cross section of 0.61x0.61 m 2 for a 8 MA turns coil made of a 16 kA conductor it is shown that sufficient hydraulic cross section can be provided within such cables to remove the expected thermal load resulting from nuclear heating with exponential decay from inboard to outboard side of the winding. The concept is a pancake type coil with 1.8 K helium fed-in the high field region of each pancake. The temperature distribution within such coils is calculated, and the local safety margin is determined from temperature and field. The calculation takes account of nuclear and a.c. heating, and of thermal conductance between the individual layers and the coil casing. It is shown that operation with 1.8 K inlet and about 3 K outlet temperature is possible. The electrical insulation with about 0.5 mm thickness proves to provide sufficient thermal insulation. No additional thermal shield is required between the coil casing and the winding package. Two different types of conductors are being considered: a) POLO type cable with quadratic cross section and a central circular coolant duct, and b) an LCT type cable with two conductors wound in hand. Both concepts with about 500 m length of the cooland channels are shown to meet the requirements resulting from a peak nuclear heat load of 0.3 mW/cm 3 in the inboard turns. The hydraulic diameters are sufficient to operate each coils with self-sustained fountain effect pumps. Even appreciably higher heat loads with up to 3 mW/cm 3 of nuclear heating can be tolerated for the POLO type cable when the hydraulic diameter is enlarged to its maximum of 17 mm. (orig.) [de

  10. Analysis of visible spectral lines in LHD helium discharge

    Wan, B.N.; Goto, M.; Morita, S.

    1999-06-01

    In this study, visible spectral lines in LHD helium discharges are analyzed and it was found that they could be well fitted with gaussian profile. The results reveal a simple mechanism of helium atom recycling. Ion temperatures were also derived from the fitting. A typical value of the ion temperature obtained was about 6 eV. (author)

  11. Deposition, milling, and etching with a focused helium ion beam

    Alkemade, P.F.A.; Veldhoven, E. van

    2012-01-01

    The recent successful development of the helium ion microscope has produced both a new type of microscopy and a new tool for nanoscale manufacturing. This chapter reviews the first explorations in this new field in nanofabrication. The studies that utilize the Orion helium ion microscope to grow or

  12. Phenomenological studies and modelling of the gaseous impurities oxidation and adsorption mechanisms in helium: application for the purification system optimization in gas cooled nuclear reactors

    Legros, F.

    2008-01-01

    In GEN IV studies on future fission nuclear reactors, two concepts using helium as a coolant have been selected: GFR and VHTR. Among radioactive impurities and dusts, helium can contain H 2 , CO, CH 4 , CO 2 , H 2 O, O 2 , as well as nitrogenous species. To optimize the reactor functioning and lifespan, it is necessary to control the coolant chemical composition using a dedicated purification system. A pilot designed at the CEA allows studying this purification system. Its design includes three unit operations: H 2 and CO oxidation on CuO, then two adsorption steps. This study aims at providing a detailed analysis of the first and second purification steps, which have both been widely studied experimentally at laboratory scale. A first modelling based on a macroscopic approach was developed to represent the behaviour of the reactor and has shown that the CuO fixed bed conversion is dependent on the chemistry (mass transfer is not an issue) and is complete. The results of the structural analysis of the solids allow considering the CuO as particles made of 200 nm diameter grains. Hence, a new model at grain scale is proposed. It is highlighted that the kinetic constants from these two models are related with a scale factor which depends on geometry. A competition between carbon monoxide and hydrogen oxidation has been shown. Activation energies are around 30 kJ.mol-1. Simulation of the simultaneous oxidations leads to consider CO preferential adsorption. A similar methodology has been applied for CO 2 and H 2 O adsorption. The experimental isotherms showed a Langmuir type adsorption. Using this model, experimental and theoretical results agree. (author) [fr

  13. Surface electrons of helium films

    Studart, N.; Hipolito, O.

    1986-01-01

    Theoretical calculations of some properties of two-dimensional electrons on a liquid helium film adsorbed on a solid substrate are reviewed. We describe the spectrum of electron bound states on bulk helium as well on helium films. The correlational properties, such as the structure factor and correlation energy, are determined as functions of the film thickness for different types of substrates in the framework of a Generalized Random-Phase Approximation. The collective excitations of this system are also described. The results for electrons on the surface of thin films and bulk helium are easily obtained. we examine the electron interaction with the excitations of the liquid helium surface resulting in a new polaron state, which was observed very recently. The ground state energy and the effective mass of this polaron are determined by using the path-integral formalism and unitary-transformation method. Recent speculations about the phase diagram of electrons on the helium film are also discussed. (Author) [pt

  14. Feasibility of lunar Helium-3 mining

    Kleinschneider, Andreas; Van Overstraeten, Dmitry; Van der Reijnst, Roy; Van Hoorn, Niels; Lamers, Marvin; Hubert, Laurent; Dijk, Bert; Blangé, Joey; Hogeveen, Joel; De Boer, Lennaert; Noomen, Ron

    With fossil fuels running out and global energy demand increasing, the need for alternative energy sources is apparent. Nuclear fusion using Helium-3 may be a solution. Helium-3 is a rare isotope on Earth, but it is abundant on the Moon. Throughout the space community lunar Helium-3 is often cited as a major reason to return to the Moon. Despite the potential of lunar Helium-3 mining, little research has been conducted on a full end-to-end mission. This abstract presents the results of a feasibility study conducted by students from Delft University of Technology. The goal of the study was to assess whether a continuous end-to-end mission to mine Helium-3 on the Moon and return it to Earth is a viable option for the future energy market. The set requirements for the representative end-to-end mission were to provide 10% of the global energy demand in the year 2040. The mission elements have been selected with multiple trade-offs among both conservative and novel concepts. A mission architecture with multiple decoupled elements for each transportation segment (LEO, transfer, lunar surface) was found to be the best option. It was found that the most critical element is the lunar mining operation itself. To supply 10% of the global energy demand in 2040, 200 tons of Helium-3 would be required per year. The resulting regolith mining rate would be 630 tons per second, based on an optimistic concentration of 20 ppb Helium-3 in lunar regolith. Between 1,700 to 2,000 Helium-3 mining vehicles would be required, if using University of Wisconsin’s Mark III miner. The required heating power, if mining both day and night, would add up to 39 GW. The resulting power system mass for the lunar operations would be in the order of 60,000 to 200,000 tons. A fleet of three lunar ascent/descent vehicles and 22 continuous-thrust vehicles for orbit transfer would be required. The costs of the mission elements have been spread out over expected lifetimes. The resulting profits from Helium

  15. The study on the electrical resistivity of Cu/V multilayer films subjected to helium (He) ion irradiation

    Wang, P. P.; Xu, C.; Fu, E. G.; Du, J. L.; Gao, Y.; Wang, X. J.; Qiu, Y. H.

    2018-05-01

    Sputtering-deposited Cu/V multilayer films with the individual layer thickness varying from 2.5 nm to 100 nm were irradiated by 1 MeV helium (He) ion at the fluence of 6 ×1016 ions ·cm-2 at room temperature. The resistivity of Cu/V multilayer films after ion irradiation was evaluated as a function of individual layer thickness at 300 K and compared with their resistivity before ion irradiation. The results show that the resistivity change before and after ion irradiation is largely determined by the interface structure, grain boundary and radiation induced defects. A model amended based on the model used in describing the resistivity of as-deposited Cu/V multilayer films was proposed to describe the resistivity of ion irradiated Cu/V multilayer films by considering the point defects induced by ion irradiation, the effect of interface absorption on defects and the effect of interface microstructure in the multilayer films.

  16. Hydrogen and helium adsorption on potassium

    Garcia, R.; Mulders, N.; Hess, G.

    1995-01-01

    A previous quartz microbalance study of adsorption of helium on sodium indicates that the inert layer is surprisingly small. Similar experiments with hydrogen on sodium show layer by layer growth below a temperature of 7K. These results motivated the authors to extend the experiments to lower temperatures. A suitable apparatus, capable of reaching 0.45 K, while still enabling them to do in situ alkali evaporation, has been constructed. The authors will report on the results of microbalance adsorption experiments of helium and hydrogen on potassium

  17. Compatibility study of trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin (TNAD) with some energetic components and inert materials

    Yan Qilong; Li Xiaojiang; Zhang Laying; Li Jizhen; Li Hongli; Liu Ziru

    2008-01-01

    The compatibility of trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin (TNAD) with some energetic components and inert materials of solid propellants was studied by using the pressure DSC method where, cyclotetramethylenetetranitroamine (HMX), cyclotrimethylenetrinitramine (RDX), 1,4-dinitropiperazine (DNP), 1.25/1-NC/NG mixture, lead 3-nitro-1,2,4-triazol-5-onate (NTO-Pb), aluminum powder (Al, particle size = 13.6 μm) and N-nitrodihydroxyethylaminedinitrate (DINA) were used as energetic components and polyethylene glycol (PEG), polyoxytetramethylene-co-oxyethylene (PET), addition product of hexamethylene diisocyanate and water (N-100), 2-nitrodianiline (2-NDPA), 1,3-dimethyl-1,3-diphenyl urea (C 2 ), carbon black (C.B.), aluminum oxide (Al 2 O 3 ), cupric 2,4-dihydroxy-benzoate (β-Cu), cupric adipate (AD-Cu) and lead phthalate (φ-Pb) were used as inert materials. It was concluded that the binary systems of TNAD with NTO-Pb, RDX, PET and Al powder are compatible, and systems of TNAD with DINA and HMX are slightly sensitive, and with 2-NDPA, φ-Pb, β-Cu, AD-Cu and Al 2 O 3 are sensitive, and with PEG, N-100, C 2 and C.B. are incompatible. The impact and friction sensitivity data of the TNAD and TNAD in combination with the other energetic materials under present study was also obtained, and there was no consequential affiliation between sensitivity and compatibility

  18. Failure study of helium-cooled tungsten divertor plasma-facing units tested at DEMO relevant steady-state heat loads

    Ritz, G; Pintsuk, G; Linke, J; Hirai, T; Norajitra, P; Reiser, J; Giniyatulin, R; Makhankov, A; Mazul, I

    2009-01-01

    Tungsten was selected as armor material for the helium-cooled divertor in future DEMO-type fusion reactors and fusion power plants. After realizing the design and testing of them under cyclic thermal loads of up to ∼14 MW m -2 , the tungsten divertor plasma-facing units were examined by metallography; they revealed failures such as cracks at the thermal loaded and as-machined surfaces, as well as degradation of the brazing layers. Furthermore, in order to optimize the machining processes, the quality of tungsten surfaces prepared by turning, milling and using a diamond cutting wheel were examined. This paper presents a metallographic examination of the tungsten plasma-facing units as well as technical studies and the characterization on machining of tungsten and alternative brazing joints.

  19. Failure study of helium-cooled tungsten divertor plasma-facing units tested at DEMO relevant steady-state heat loads

    Ritz, G.; Hirai, T.; Norajitra, P.; Reiser, J.; Giniyatulin, R.; Makhankov, A.; Mazul, I.; Pintsuk, G.; Linke, J.

    2009-12-01

    Tungsten was selected as armor material for the helium-cooled divertor in future DEMO-type fusion reactors and fusion power plants. After realizing the design and testing of them under cyclic thermal loads of up to ~14 MW m-2, the tungsten divertor plasma-facing units were examined by metallography; they revealed failures such as cracks at the thermal loaded and as-machined surfaces, as well as degradation of the brazing layers. Furthermore, in order to optimize the machining processes, the quality of tungsten surfaces prepared by turning, milling and using a diamond cutting wheel were examined. This paper presents a metallographic examination of the tungsten plasma-facing units as well as technical studies and the characterization on machining of tungsten and alternative brazing joints.

  20. Canada's helium output rising fast

    1966-12-01

    About 12 months from now, International Helium Limited will be almost ready to start up Canada's second helium extraction plant at Mankota, in Saskatchewan's Wood Mountain area about 100 miles southwest of Moose Jaw. Another 80 miles north is Saskatchewan's (and Canada's) first helium plant, operated by Canadian Helium and sitting on a gas deposit at Wilhelm, 9 miles north of Swift Current. It contains almost 2% helium, some COD2U, and the rest nitrogen. One year in production was apparently enough to convince Canadian Helium that the export market (it sells most of its helium in W. Europe) can take a lot more than it's getting. Construction began this summer on an addition to the Swift Current plant that will raise its capacity from 12 to 36MMcf per yr when it goes on stream next spring. Six months later, International Helium's 40 MMcf per yr plant to be located about 4 miles from its 2 Wood Mountain wells will double Canada's helium output again.

  1. Helium atoms and molecules in strong magnetic fields

    Mori, K.

    Recent theoretical studies have shown that the neutron star surface may be composed of helium or heavier elements as hydrogen may be quickly depleted by diffuse nuclear burning Chang Bildsten However while Hydrogen atmospheres have been studied in great details atomic data for helium is available only for He ion Pavlov Bezchastnov 2005 We performed Hartree-Fock type calculation for Helium atom and molecules and computed their binding ionization and dissociation energies in strong magnetic fields B sim10 12 -- 10 15 G We will present ionization balance of Helium atmospheres at typical magnetic field strengths and temperatures to radio-quiet neutron stars and AXPs We will also discuss several implications of helium atmosphere to X-ray data of isolated neutron stars focusing on the detected spectral features

  2. Reaction of yttria-stabilized zirconia with zirconium, silicon and Zircaloy-4 at high temperature: a compatibility study for cermet fuels

    Arima, T.; Tateyama, T.; Idemitsu, K.; Inagaki, Y.

    2003-01-01

    Compatibility studies for cermet (ceramic and metal) fuels have been completed for a temperature range of 1073-1423 K. A reaction between yttria-stabilized zirconia (YSZ), as a simulated fuel, and Zr, as a candidate for a metallic matrix, has been observed at temperatures ≥1273 K, which means the formation of a metallic reaction layer at the interface between YSZ and Zr and the occurrence of metallic phases inside the YSZ. Similar results were observed for the YSZ-Zry4 (cladding) system. On the other hand, the degree of reaction was relatively large for the YSZ-Si (metallic matrix) system, and Si diffused into the YSZ. However, the maximum fuel center-line temperature can be predicted to be less than ∼1273 K for cermet fuels. Therefore, compatibility between the ceramic fuel and the metallic matrix should be good under normal reactor operational conditions. Furthermore, since the temperature of the fuel-cladding gap is lower, the cermet fuel and the cladding material are compatible

  3. Orion A helium abundance

    Tsivilev, A.P.; Ershov, A.A.; Smirnov, G.T.; Sorochenko, R.L.

    1986-01-01

    The 22.4-GHz (H,He)66-alpha and 36.5-GHz (H,He)56-alpha radio recombination lines have been observed at several Jaffe-Pankonin positions in the central part of the Orion A source. The measured relative abundance of ionized helium increases with distance, averaging 11.6 percent at peripheral points. The observed behavior is interpreted by a blister-type model nebula, which implies that Orion A has a true He abundance of 12 percent, is moving with a radial velocity of 5 km/sec, and is expanding. 18 references

  4. Simulation of liquid helium

    Ceperley, D.M.

    1985-07-01

    The author discusses simulation methods for quantum mechanical systems at finite temperatures. Recently it has been shown that static properties of some quantum systems can be obtained by simulation in a straightforward manner using path integrals, albeit with an order of magnitude more computing effort needed than for the corresponding classical systems. Some dynamical information can be gleaned from these simulations as will be discussed below. But this is very limited - there is no quantum version of the molecular dynamics method. The path integral method is illustrated by discussing the application to liquid helium. 12 refs., 8 figs

  5. The adsorption of helium atoms on coronene cations

    Kurzthaler, Thomas; Rasul, Bilal; Kuhn, Martin; Scheier, Paul, E-mail: Paul.Scheier@uibk.ac.at, E-mail: andrew.ellis@le.ac.uk [Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Lindinger, Albrecht [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany); Ellis, Andrew M., E-mail: Paul.Scheier@uibk.ac.at, E-mail: andrew.ellis@le.ac.uk [Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2016-08-14

    We report the first experimental study of the attachment of multiple foreign atoms to a cationic polycyclic aromatic hydrocarbon (PAH). The chosen PAH was coronene, C{sub 24}H{sub 12}, which was added to liquid helium nanodroplets and then subjected to electron bombardment. Using mass spectrometry, coronene cations decorated with helium atoms were clearly seen and the spectrum shows peaks with anomalously high intensities (“magic number” peaks), which represent ion-helium complexes with added stability. The data suggest the formation of a rigid helium layer consisting of 38 helium atoms that completely cover both faces of the coronene ion. Additional magic numbers can be seen for the further addition of 3 and 6 helium atoms, which are thought to attach to the edge of the coronene. The observation of magic numbers for the addition of 38 and 44 helium atoms is in good agreement with a recent path integral Monte Carlo prediction for helium atoms on neutral coronene. An understanding of how atoms and molecules attach to PAH ions is important for a number of reasons including the potential role such complexes might play in the chemistry of the interstellar medium.

  6. Prognostic factors and recurrence of hepatitis B-related hepatocellular carcinoma after argon-helium cryoablation: a prospective study.

    Wang, Chunping; Lu, Yinying; Chen, Yan; Feng, Yongyi; An, Linjing; Wang, Xinzhen; Su, Shuhui; Bai, Wenlin; Zhou, Lin; Yang, Yongping; Xu, Dongping

    2009-01-01

    To determine the long-term prognosis of hepatocellular carcinoma (HCC) after argon-helium cryoablation and identify the risk factors that predict metastasis and recurrence. A total of 156 patients with hepatitis B-related HCC less than 5 cm in diameter who underwent curative cryoablation were followed up prospectively for tumor metastasis and recurrence. Immunohistochemistry was used to analyze the expression of vascular endothelial growth factor (VEGF). HBV basal core promoter (BCP) and precore mutations were detected by DNA sequence analysis. Post-treatment prognostic factors influencing survival, tumor metastasis and recurrence were assessed by univariate and multivariate analyses. The variables included the expression of VEGF in HCC tissues, clinical and pathologic characteristics of patients, and HBV features (HBV DNA level, HBV genotype, BCP mutation). The median follow-up period of the 156 patients was 37 months (range 8-48 months). The 1-, 2-, and 3-year overall survival rates were 92, 82 and 64%, respectively. The 1-, 2-, and 3-year recurrence-free survival rates were 72, 56 and 43%, respectively. Eighty-five patients (54.5%) had tumor recurrence or metastasis. The multivariate analysis showed that Child-Pugh class and the expression of VEGF in HCC tissues could be used as independent prognostic factors for overall survival. Meanwhile, the expression of VEGF in HCC tissues and HBV BCP mutations were found to be independent prognostic factors for recurrence-free survival. Strong expression of VEGF in HCC tissues and HBV BCP mutations are important risk predictors for recurrence or metastasis of HCC smaller than 5 cm in diameter.

  7. A performance study on three qPCR quantification kits and their compatibilities with the 6-dye DNA profiling systems.

    Lin, Sze-Wah; Li, Christina; Ip, Stephen C Y

    2018-03-01

    DNA quantification plays an integral role in forensic DNA profiling. Not only does it estimate the total amount of amplifiable human autosomal and male DNA to ensure optimal amplification of target DNA for subsequent analysis, but also assesses the extraction efficiency and purity of the DNA extract. Latest DNA quantification systems even offer an estimate for the degree of DNA degradation in a sample. Here, we report the performance of three new generation qPCR kits, namely Investigator ® Quantiplex HYres Kit from QIAGEN, Quantifiler ® Trio DNA Quantification Kit from Applied Biosystems™, and PowerQuant ® System from Promega, and their compatibilities with three 6-dye DNA profiling systems. Our results have demonstrated that all three kits generate standard curves with satisfactory consistency and reproducibility, and are capable of screening out traces of male DNA in the presence of 30-fold excess of female DNA. They also exhibit a higher tolerance to PCR inhibition than Quantifiler ® Human DNA Quantification Kit from Applied Biosystems™ in autosomal DNA quantification. PowerQuant ® , as compared to Quantiplex HYres and Quantifiler ® Trio, shows a better precision for both autosomal and male DNA quantifications. Quantifiler ® Trio and PowerQuant ® in contrast to Quantiplex HYres offer better correlations with lower discrepancies between autosomal and male DNA quantification, and their additional degradation index features provide a detection platform for inhibited and/or degraded DNA template. Regarding the compatibility between these quantification and profiling systems: (1) both Quantifiler ® Trio and PowerQuant ® work well with GlobalFiler and Fusion 6C, allowing a fairly accurate prediction of their DNA typing results based on the quantification values; (2) Quantiplex HYres offers a fairly reliable IPC system for detecting any potential inhibitions on Investigator 24plex, whereas Quantifiler ® Trio and PowerQuant ® suit better for Global

  8. An efficient continuous flow helium cooling unit for Moessbauer experiments

    Herbert, I.R.; Campbell, S.J.

    1976-01-01

    A Moessbauer continuous flow cooling unit for use with liquid helium over the temperature range 4.2 to 300K is described. The cooling unit can be used for either absorber or source studies in the horizontal plane and it is positioned directly on top of a helium storage vessel. The helium transfer line forms an integral part of the cooling unit and feeds directly into the storage vessel so that helium losses are kept to the minimum. The helium consumption is 0.12 l h -1 at 4.2 K decreasing to 0.055 l h -1 at 40 K. The unit is top loading and the exchange gas cooled samples can be changed easily and quickly. (author)

  9. Comment on theories for helium-assisted void nucleation

    Russell, K.C.

    1976-01-01

    Voids form by agglomeration of irradiation-induced vacancies which remain after preferential absorption of self interstitials at dislocation lines. Helium which is formed by (n,α) transmutations and, in simulation studies, may be ion-implanted, often plays an important, but puzzling role. In some materials, very few voids form in the absence of helium, even after intense irradiation. In many other materials , voids form readily under a variety of irradiation conditions, even in the absence of helium. Why some materials require helium - typically in the 10 -6 apa (atom per atom) range - and others do not, and the reason for that particular level are by no means clear. The physics of void nucleation, particularly the role of helium, have been the subject of several theoretical papers. This note presents a critique of these theories, and then briefly outlines a new analysis which is not subject to their limitations. (Auth.)

  10. High Efficiency Regenerative Helium Compressor, Phase I

    National Aeronautics and Space Administration — Helium plays several critical rolls in spacecraft propulsion. High pressure helium is commonly used to pressurize propellant fuel tanks. Helium cryocoolers can be...

  11. Photoassociation of cold metastable helium atoms

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to

  12. 2017 Status report-Tritium aging studies on stainless steel: Effect of hydrogen, tritium and decay helium on the fracture-toughness properties of stem, cup and block forgings

    Morgan, Michael J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-06-28

    The materials of construction of tritium reservoirs are forged stainless steels. During service, the structural properties of the stainless steel change over time because of the diffusion of tritium into the reservoir wall and its radioactive decay to helium-3. This aging effect can cause cracks to initiate and grow which could result in a tritium leak or delayed failure of a tritium reservoir. Numerous factors affect the tendency for crack formation and propagation and are being investigated in this program. The goal of the research is to provide relevant fracture mechanics data that can be used by the design agencies in their assessments of tritium reservoir structural integrity. In this status report, new experimental results are presented on the effects of tritium and decay helium on the cracking properties of specimens taken from actual tritium reservoir forgings instead of the experimental forgings of past programs. The properties measured are more representative of actual reservoir properties because the microstructure of the specimens tested are more like that of the actual tritium reservoirs. The program was designed to measure the effects of material variables on tritium compatibility and includes two stainless steels (Type 304L and 316L stainless steel), multiple yield strengths (360-500 MPa), and multiple forging shapes (Stem, Cup, and Block).

  13. A helium regenerative compressor

    Swift, W.L.; Nutt, W.E.; Sixsmith, H.

    1994-01-01

    This paper discusses the design and performance of a regenerative compressor that was developed primarily for use in cryogenic helium systems. The objectives for the development were to achieve acceptable efficiency in the machine using conventional motor and bearing technology while reducing the complexity of the system required to control contamination from the lubricants. A single stage compressor was built and tested. The compressor incorporates aerodynamically shaped blades on a 218 mm (8.6 inches) diameter impeller to achieve high efficiency. A gas-buffered non-contact shaft seal is used to oppose the diffusion of lubricant from the motor bearings into the cryogenic circuit. Since it is a rotating machine, the flow is continuous and steady, and the machine is very quiet. During performance testing with helium, the single stage machine has demonstrated a pressure ratio of 1.5 at a flow rate of 12 g/s with measured isothermal efficiencies in excess of 30%. This performance compares favorably with efficiencies generally achieved in oil flooded screw compressors

  14. Helium production in reactor materials

    Lippincott, E.P.; McElroy, W.N.; Farrar, H. IV.

    1975-02-01

    Comparisons of integral helium production measurements with predictions based on ENDF/B Version IV cross sections have been made. It is concluded that an ENDF/B helium production cross section file should be established in order to ensure a complete and consistent cross section evaluation to meet accuracies required for LMFBR, CTR, and LWR applications. (U.S.)

  15. Socially compatible technology management

    Tschiedel, R.

    1989-01-01

    The public has a critical eye on the impacts of technology, and there is a growing awareness of the social impacts in addition to health hazards and economic and ecologic impacts. 'Socially compatible technology management' is the magic formula frequently used which has emerged as a political demand in the course of the social controversy about the hazards of large-scale technology. It marks a position in the conflict between those who declare existing market and policy instruments to be sufficient regulatory tools, and those who understand the incidents ranging from inadequacy to desaster as a warning, and call for more precaution in decisions with an impact on the future. The concept of 'social compatibility' has to be given shape by elaborating criteria and methods for achieving this goal. The book shows that social compatibility cannot sufficiently be defined either as a quality of a technology and of a socio-technical system (acceptability), or as the willingness of the people concerned to accept a technology (acceptance). The investigation explains by means of empirical analysis and examples that participation is the only way to combine acceptability and acceptance into a socially compatibly designed technology. The leading theoretical and political formula developed for this purpose is 'acquisition'. To put it in a provocative way: Man has to learn to manage and master technical systems as if they were an integral part of themselves. Which means, man has to acquire the required knowledge and skill in the changing social structures, and the real power of disposal. Sociology of technology is a branch of research that can and should give support in the process of designing and managing technological systems in a way compatible with social needs. (orig./HP) [de

  16. Study of a decaying helium plasma having a high neutral particle density; Etude d'un plasma d'helium, a forte densite de neutres, en regime de relaxation

    Deloche, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    We have shown theoretically, in a high pressure, decaying helium plasma, the effect at low energy of inelastic collisions between neutral particles on the population densities of excited molecules and electron-ion recombination coefficient. The formalism of Bates (1962) has been used, taking into account simultaneously collisional mechanisms with electrons, collisional mechanisms with neutrals and radiative processes. The variation of the population densities and electron-ion recombination coefficient with respect to the pressure is given for different values of electron density and temperature. These theoretical results indicate an effect of pressure large enough to be measured and allow us to define the most favorable experimental conditions. (author) [French] L'effet des collisions inelastiques entre particules neutres dans un plasma d'helium, en regime de relaxation, a basse temperature electronique et forte densite de neutres, a ete mis en evidence, theoriquement, aussi bien dans le calcul des densites de population des molecules excitees que dans la determination du coefficient de recombinaison electron-ion. Nous avons utilise le formalisme de Bates (1962) en tenant compte simultanement des mecanismes collisionnels avec les electrons, des mecanismes collisionnels avec les neutres et des phenomenes radiatifs. La variation des densites de population et du coefficient de recombinaison electron-ion en fonction de la pression est donnee pour differentes valeurs de la densite electronique et de la temperature. Ces resultats theoriques laissent prevoir un effet de la pression suffisamment important pour qu'il puisse etre mesure et permettent de definir les conditions experimentales les plus favorables. (auteur)

  17. Exotic helium molecules; Molecules exotiques d'helium

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  18. Exotic helium molecules; Molecules exotiques d'helium

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  19. Hydrogen Process Coupling to Modular Helium Reactors

    Shenoy, Arkal; Richards, Matt; Buckingham, Robert

    2009-01-01

    The U.S. Department of Energy (DOE) has selected the helium-cooled High Temperature Gas-Cooled Reactor (HTGR) as the concept to be used for the Next Generation Nuclear Plant (NGNP), because it is the most advanced Generation IV concept with the capability to provide process heat at sufficiently high temperatures for production of hydrogen with high thermal efficiency. Concurrently with the NGNP program, the Nuclear Hydrogen Initiative (NHI) was established to develop hydrogen production technologies that are compatible with advanced nuclear systems and do not produce greenhouse gases. The current DOE schedule for the NGNP Project calls for startup of the NGNP plant by 2021. The General Atomics (GA) NGNP pre-conceptual design is based on the GA Gas Turbine Modular Helium Reactor (GT-MHR), which utilizes a direct Brayton cycle Power Conversion System (PCS) to produce electricity with a thermal efficiency of 48%. The nuclear heat source for the NGNP consists of a single 600-MW(t) MHR module with two primary coolant loops for transport of the high-temperature helium exiting the reactor core to a direct cycle PCS for electricity generation and to an Intermediate Heat Exchanger (IHX) for hydrogen production. The GA NGNP concept is designed to demonstrate hydrogen production using both the thermochemical sulfur-iodine (SI) process and high-temperature electrolysis (HTE). The two primary coolant loops can be operated independently or in parallel. The reactor design is essentially the same as that for the GT-MHR, but includes the additional primary coolant loop to transport heat to the IHX and other modifications to allow operation with a reactor outlet helium temperature of 950 .deg. C (vs. 850 .deg. C for the GT-MHR). The IHX transfers a nominal 65 MW(t) to the secondary heat transport loop that provides the high-temperature heat required by the SI-based and HTE-based hydrogen production facilities. Two commercial nuclear hydrogen plant variations were evaluated with

  20. Two Simon tasks with different sources of conflict: an ERP study of motion- and location-based compatibility effects.

    Galashan, Daniela; Wittfoth, Matthias; Fehr, Thorsten; Herrmann, Manfred

    2008-07-01

    Behavioral and electrophysiological correlates of two Simon tasks were examined using comparable stimuli but different task-irrelevant and conflict-inducing stimulus features. Whereas target shape was always the task-relevant stimulus attribute, either target location (location-based task) or motion direction within the target stimuli (motion-based task) was used as a source of conflict. Data from ten healthy participants who performed both tasks are presented. In the motion-based task the incompatible condition showed smaller P300 amplitudes at Pz than the compatible condition and the location-based task yielded a trend towards a reduced P300 amplitude in the incompatible condition. For both tasks, no P300 latency differences between the conditions were found at Pz. The results suggest that the motion-based task elicits behavioral and electrophysiological effects comparable with regular Simon tasks. As all stimuli in the motion-based Simon task were presented centrally the present data strongly argue against the attention-shifting account as an explanatory approach.

  1. A study of the switching mechanism and electrode material of fully CMOS compatible tungsten oxide ReRAM

    Chien, W. C.; Chen, Y. C.; Lai, E. K.; Lee, F. M.; Lin, Y. Y.; Chuang, Alfred T. H.; Chang, K. P.; Yao, Y. D.; Chou, T. H.; Lin, H. M.; Lee, M. H.; Shih, Y. H.; Hsieh, K. Y.; Lu, Chih-Yuan

    2011-03-01

    Tungsten oxide (WO X ) resistive memory (ReRAM), a two-terminal CMOS compatible nonvolatile memory, has shown promise to surpass the existing flash memory in terms of scalability, switching speed, and potential for 3D stacking. The memory layer, WO X , can be easily fabricated by down-stream plasma oxidation (DSPO) or rapid thermal oxidation (RTO) of W plugs universally used in CMOS circuits. Results of conductive AFM (C-AFM) experiment suggest the switching mechanism is dominated by the REDOX (Reduction-oxidation) reaction—the creation of conducting filaments leads to a low resistance state and the rupturing of the filaments results in a high resistance state. Our experimental results show that the reactions happen at the TE/WO X interface. With this understanding in mind, we proposed two approaches to boost the memory performance: (i) using DSPO to treat the RTO WO X surface and (ii) using Pt TE, which forms a Schottky barrier with WO X . Both approaches, especially the latter, significantly reduce the forming current and enlarge the memory window.

  2. Photoionization of helium dimers

    Havermeier, Tilo

    2010-01-01

    The helium dimer is one of the most weakly bound systems in the universe. This makes it an interesting quantum mechanical object for investigation. These Van der Waals Clusters can be produced in an expansion of a cryogenic gas jet through a small nozzle into vacuum. In the present experiment we examine the interaction of He dimers with synchrotron radiation at an energy range from 64 to 78 eV. We observed different pathways leading to single ionization of both He atoms of the dimer compound. This two close standing ions begin now to dissociate in cause of their coulomb potential. All charged fragments were detected in coincidence with a COLTRIMS system. Especially Interatomic Coulombic Decay (ICD) and the two step process (TS1) were clearly identified. Furthermore a distribution of the internuclear distance was obtained from the measured Kinetic Energy Release (KER). (orig.)

  3. Ab initio investigation of helium in Y_2Ti_2O_7: Mobility and effects on mechanical properties

    Danielson, T.; Tea, E.; Hin, C.

    2016-01-01

    Oxide nanoclusters (NCs) in nanostructured ferritic alloys (NFAs) are known to be efficient trapping sites for the transmutation product helium. In this study, the migration barriers and potential energy surfaces of helium in Y_2Ti_2O_7 are presented to explain the mobility of helium through oxide NCs and shed light on the accumulation of helium and the trapping mechanisms of the oxides. A complex tunnel-shaped potential energy surface is identified and gives rise to relatively large migration barriers. Subsequently, the effect of helium accumulation on the mechanical properties of Y_2Ti_2O_7 oxide nanoclusters is investigated and it is shown that the mechanical properties of the oxide do not significantly degrade as helium accumulates. - Highlights: • Migration barriers of helium in Y_2Ti_2O_7 are calculated using the climbing image nudged elastic band. • Helium Potential energy surfaces are calculated. • Mechanical properties of varying helium concentrations are presented.

  4. Comparative Evaluation of Retentive Properties of Two Compatible Ball Attachments in Mandibular Implant-Retained Overdentures: An In Vitro Study

    Maryam Memarian

    2018-02-01

    Full Text Available Objectives: The retentive properties of implant-retained overdentures (IRO may be influenced by the type of attachments. The aim of this research was to compare the retention of two dental implant systems with compatible ball attachments, namely Straumann® system (SS and Rhein83 SRL system (RS after fatigue testing.Materials and Methods: Two laboratory models consisting of two parallel Straumann® fixtures at a distance of 22 mm were prepared. Five pairs of each systems' ball attachments were examined (n=5. The samples were soaked in artificial saliva. The retention strength values (RSV were recorded before the fatigue test and after 1100, 2200, 3300, 4400, and 5500 insertion and removal cycles at a speed of 51 mm/minute with a 50-N load cell in a universal testing machine. The data were analyzed by repeated measures analysis of variance (ANOVA followed by independent sample t-test with Bonferroni corrections.Results: There was a decrease in the RSV in both systems after 5500 cycles of insertion and removal. There was a significant statistical difference between the RSV of the normal Sphero Block of the RS (17.52±0.68 N and that of the Spare Lamella retention inserts of the SS (19.72±0.74 N, P=0.001.Conclusions: Although the RSVs of the RS and SS were almost similar before the fatigue test, as the number of insertion and removal cycles increased, the RSV decreased more significantly in the RS compared to the SS.

  5. Thermal release behavior of helium from copper irradiated by He+ ions

    Yamauchi, T.; Tokura, S.; Yamanaka, S.; Miyake, M.

    1988-01-01

    Thermal release behavior of helium from copper irradiated by 20 keV He + ions with a dose of 2x10 15 to 3x10 17 ions/cm 2 has been studied. The shape of the thermal release curves and thew number of helium release peaks strongly depend on the irradiation dose. Results from SEM surface observastion after post-irradiation heating suggested that helium release caused various surface damages such as blistering, flaking, and hole formation. Helium release resulting in small holes was analyzed and helium bubble growth mechanisms are discussed. (orig.)

  6. Compatible quantum theory

    Friedberg, R; Hohenberg, P C

    2014-01-01

    Formulations of quantum mechanics (QM) can be characterized as realistic, operationalist, or a combination of the two. In this paper a realistic theory is defined as describing a closed system entirely by means of entities and concepts pertaining to the system. An operationalist theory, on the other hand, requires in addition entities external to the system. A realistic formulation comprises an ontology, the set of (mathematical) entities that describe the system, and assertions, the set of correct statements (predictions) the theory makes about the objects in the ontology. Classical mechanics is the prime example of a realistic physical theory. A straightforward generalization of classical mechanics to QM is hampered by the inconsistency of quantum properties with classical logic, a circumstance that was noted many years ago by Birkhoff and von Neumann. The present realistic formulation of the histories approach originally introduced by Griffiths, which we call ‘compatible quantum theory (CQT)’, consists of a ‘microscopic’ part (MIQM), which applies to a closed quantum system of any size, and a ‘macroscopic’ part (MAQM), which requires the participation of a large (ideally, an infinite) system. The first (MIQM) can be fully formulated based solely on the assumption of a Hilbert space ontology and the noncontextuality of probability values, relying in an essential way on Gleason's theorem and on an application to dynamics due in large part to Nistico. Thus, the present formulation, in contrast to earlier ones, derives the Born probability formulas and the consistency (decoherence) conditions for frameworks. The microscopic theory does not, however, possess a unique corpus of assertions, but rather a multiplicity of contextual truths (‘c-truths’), each one associated with a different framework. This circumstance leads us to consider the microscopic theory to be physically indeterminate and therefore incomplete, though logically coherent. The

  7. ATR-FTIR Based Pre and Post Formulation Compatibility Studies for the Design of Niosomal Drug Delivery System Containing Nonionic Amphiphiles and Chondroprotective Drug

    Khan, M.I.; Madni, A.; Ahmad, S.; Rehmanand, M.; Mahmood, M.A.; Khan, A.

    2015-01-01

    Pharmaceutical compatibility studies are considered as the most important and first screening stage during development of pharmaceutical drug product. Attenuated total reflectance/fourier transform infrared (ATR-FTIR) is one of the techniques currently available to pharmaceutical scientists for investigating the compatibilities between active drug and inactive pharmaceutical ingredients. The present study was designed to assess the interaction among different niosomes forming components i.e nonionic amphiphiles and chondroprotective/antiinflamatory drug Diacerein by ATR-FTIR method. Physical mixtures and niosomes were prepared by physical mixing and thin film hydration method, respectively. The individual niosomal components, physical mixtures as well as niosomal formulations were analyzed. The spectra of Diacerein showed characteristic peaks at 3300 cm/sup -1/(-COOH) and 760 cm/sup -1/(msubstituted benzene), Span 60 at 2916 cm/sup -1/(-OH), Span 80 at 1740 cm/sup -1/(5- membered ring), Span 85 at 1643 cm/sup -1/(ketone with 5-membered ring), Tween 20 at 1734 cm/sup 1/ (5-membered ring) and Tween 80 at 3488 cm/sup -1/(-OH). The characteristic peaks of Diacerein were present in niosomal formulations with slight shift at 3355-3379 cm/sup -1/(-COOH) and 760-770 cm/sup -1/(m-substituted benzene). This work suggested no significant interaction in characteristic peaks of Diacerein after combining with nonionic surfactants as physical mixtures and niosomal formulations which proposed potential for niosomes to encapsulate diacerein in their micro vicinity. (author)

  8. Quantum dissipative dynamics and decoherence of dimers on helium droplets

    Schlesinger, Martin

    2011-01-01

    In this thesis, quantum dynamical simulations are performed in order to describe the vibrational motion of diatomic molecules in a highly quantum environment, so-called helium droplets. We aim to reproduce and explain experimental findings which were obtained from dimers on helium droplets. Nanometer-sized helium droplets contain several thousands of 4 He atoms. They serve as a host for embedded atoms or molecules and provide an ultracold ''refrigerator'' for them. Spectroscopy of molecules in or on these droplets reveals information on both the molecule and the helium environment. The droplets are known to be in the superfluid He II phase. Superfluidity in nanoscale systems is a steadily growing field of research. Spectra obtained from full quantum simulations for the unperturbed dimer show deviations from measurements with dimers on helium droplets. These deviations result from the influence of the helium environment on the dimer dynamics. In this work, a well-established quantum optical master equation is used in order to describe the dimer dynamics effectively. The master equation allows to describe damping fully quantum mechanically. By employing that equation in the quantum dynamical simulation, one can study the role of dissipation and decoherence in dimers on helium droplets. The effective description allows to explain experiments with Rb 2 dimers on helium droplets. Here, we identify vibrational damping and associated decoherence as the main explanation for the experimental results. The relation between decoherence and dissipation in Morse-like systems at zero temperature is studied in more detail. The dissipative model is also used to investigate experiments with K 2 dimers on helium droplets. However, by comparing numerical simulations with experimental data, one finds that further mechanisms are active. Here, a good agreement is obtained through accounting for rapid desorption of dimers. We find that decoherence occurs in the electronic manifold of the

  9. High Reynolds number flows using liquid and gaseous helium

    Donnelly, R.J.

    1991-01-01

    Consideration is given to liquid and gaseous helium as test fluids, high Reynolds number test requirements in low speed aerodynamics, the measurement of subsonic flow around an appended body of revolution at cryogenic conditions in the NTF, water tunnels, flow visualization, the six component magnetic suspension system for wind tunnel testing, and recent aerodynamic measurements with magnetic suspension systems. Attention is also given to application of a flow visualization technique to a superflow experiment, experimental investigations of He II flows at high Reynolds numbers, a study of homogeneous turbulence in superfluid helium, and thermal convection in liquid helium

  10. Orientation, alignment and polarisation in electron-helium collisions

    Beijers, J.P.M.

    1987-01-01

    In this thesis electron-photon coincidence experiments to study the excitation of helium by electron impact are updated. This is achieved by cross firing a well collimated and mono-energetic electron beam with a thermal helium beam and measuring the angular and/or polarisation distribution of the decay photons in coincidence with the inelastically scattered electrons. In this way target parameters are determined for the 2 1 P, 3 1 P, 3 1 D and 3 3 P states of helium. (Auth.)

  11. Operating Manual of Helium Refrigerator (Rev. 2)

    Song, K.M.; Son, S.H.; Kim, K.S.; Lee, S.K.; Kim, M.S. [Korea Electric Power Research Institute, Taejon (Korea)

    2002-07-01

    A helium refrigerator was installed as a supplier of 20K cold helium to the cryogenic distillation system of WTRF pilot plant. The operating procedures of the helium refrigerator, helium compressor and auxiliary apparatus are described for the safety and efficient operation in this manual. The function of the helium refrigerator is to remove the impurities from the compressed helium of about 250psig, to cool down the helium from ambient temperature to 20K through the heat exchanger and expansion engine and to transfer the cold helium to the cryogenic distillation system. For the smoothly operation of helium refrigerator, the preparation, the start-up, the cool-down and the shut-down of the helium refrigerator are described in this operating manual. (author). 3 refs., 14 tabs.

  12. Biomolecular ions in superfluid helium nanodroplets

    Gonzalez Florez, Ana Isabel

    2016-01-01

    The function of a biological molecule is closely related to its structure. As a result, understanding and predicting biomolecular structure has become the focus of an extensive field of research. However, the investigation of molecular structure can be hampered by two main difficulties: the inherent complications that may arise from studying biological molecules in their native environment, and the potential congestion of the experimental results as a consequence of the large number of degrees of freedom present in these molecules. In this work, a new experimental setup has been developed and established in order to overcome the afore mentioned limitations combining structure-sensitive gas-phase methods with superfluid helium droplets. First, biological molecules are ionised and brought into the gas phase, often referred to as a clean-room environment, where the species of interest are isolated from their surroundings and, thus, intermolecular interactions are absent. The mass-to-charge selected biomolecules are then embedded inside clusters of superfluid helium with an equilibrium temperature of ∝0.37 K. As a result, the internal energy of the molecules is lowered, thereby reducing the number of populated quantum states. Finally, the local hydrogen bonding patterns of the molecules are investigated by probing specific vibrational modes using the Fritz Haber Institute's free electron laser as a source of infrared radiation. Although the structure of a wide variety of molecules has been studied making use of the sub-Kelvin environment provided by superfluid helium droplets, the suitability of this method for the investigation of biological molecular ions was still unclear. However, the experimental results presented in this thesis demonstrate the applicability of this experimental approach in order to study the structure of intact, large biomolecular ions and the first vibrational spectrum of the protonated pentapeptide leu-enkephalin embedded in helium

  13. Biomolecular ions in superfluid helium nanodroplets

    Gonzalez Florez, Ana Isabel

    2016-07-01

    The function of a biological molecule is closely related to its structure. As a result, understanding and predicting biomolecular structure has become the focus of an extensive field of research. However, the investigation of molecular structure can be hampered by two main difficulties: the inherent complications that may arise from studying biological molecules in their native environment, and the potential congestion of the experimental results as a consequence of the large number of degrees of freedom present in these molecules. In this work, a new experimental setup has been developed and established in order to overcome the afore mentioned limitations combining structure-sensitive gas-phase methods with superfluid helium droplets. First, biological molecules are ionised and brought into the gas phase, often referred to as a clean-room environment, where the species of interest are isolated from their surroundings and, thus, intermolecular interactions are absent. The mass-to-charge selected biomolecules are then embedded inside clusters of superfluid helium with an equilibrium temperature of ∝0.37 K. As a result, the internal energy of the molecules is lowered, thereby reducing the number of populated quantum states. Finally, the local hydrogen bonding patterns of the molecules are investigated by probing specific vibrational modes using the Fritz Haber Institute's free electron laser as a source of infrared radiation. Although the structure of a wide variety of molecules has been studied making use of the sub-Kelvin environment provided by superfluid helium droplets, the suitability of this method for the investigation of biological molecular ions was still unclear. However, the experimental results presented in this thesis demonstrate the applicability of this experimental approach in order to study the structure of intact, large biomolecular ions and the first vibrational spectrum of the protonated pentapeptide leu-enkephalin embedded in helium

  14. Laser spectroscopy of antiprotonic helium

    Hori, M

    2005-01-01

    When antiprotons (i.e. the antimatter counterpart of protons) are stopped in helium gas, 97% of them annihilate within picoseconds by reacting with the helium nuclei; a 3% fraction, however, survive with an anomalously long lifetime of several microseconds. This longevity is due to the formation of antiprotonic helium, which is a three-body Rydberg atom composed of an antiproton, electron, and helium nucleus. The ASACUSA experimental collaboration has recently synthesized large numbers of these atoms using CERN's Antiproton Decelerator facility, and measured the atom's transition frequencies to 60 parts per billion by laser spectroscopy. By comparing the experimental results with recent three-body QED calculations and the known antiproton cyclotron frequency, we were able to show that the antiproton mass and charge are the same as the corresponding proton values to a precision of 10 parts per billion. Ongoing and future series of experiments will further improve the experimental precision by using chirp-compe...

  15. High Accuracy Vector Helium Magnetometer

    National Aeronautics and Space Administration — The proposed HAVHM instrument is a laser-pumped helium magnetometer with both triaxial vector and omnidirectional scalar measurement capabilities in a single...

  16. Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

    Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

    1994-09-01

    The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement.

  17. A review of helium gas turbine technology for high-temperature gas-cooled reactors

    No, Hee Cheon; Kim, Ji Hwan; Kim, Hyeun Min

    2007-01-01

    Current High-Temperature Gas-cooled Reactors (HTGRs) are based on a closed brayton cycle with helium gas as the working fluid. Thermodynamic performance of the axial-flow helium gas turbines is of critical concern as it considerably affects the overall cycle efficiency. Helium gas turbines pose some design challenges compared to steam or air turbomachinery because of the physical properties of helium and the uniqueness of the operating conditions at high pressure with low pressure ratio. This report present a review of the helium Brayton cycle experiences in Germany and in Japan. The design and availability of helium gas turbines for HTGR are also presented in this study. We have developed a new throughflow calculation code to calculate the design-point performance of helium gas turbines. Use of the method has been illustrated by applying it to the GTHTR300 reference

  18. Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

    Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

    1994-01-01

    The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement. ((orig.))

  19. Determination of migration of ion-implanted helium in silica by proton backscattering spectrometry

    Szakacs, G.; Szilagyi, E.; Paszti, F.; Kotai, E.

    2008-01-01

    Understanding the processes caused by ion implantation of light ions in dielectric materials such as silica is important for developing the diagnostic systems used in fusion and fission environments. Recently, it has been shown that ion-implanted helium is able to escape from SiO 2 films. To study this process in details, helium was implanted into the central part of a buried SiO 2 island up to a fluence of 4 x 10 17 He/cm 2 . The implanted helium could be detected in the SiO 2 island, if the oxide was insulated properly from the vacuum. The shape of the helium depth distributions was far from SRIM simulation because helium distributed in the whole 1 μm thick oxide layer. After the ion implantation, helium was observed only on the implanted spot. After nine months the implanted helium filled out the whole oxide island as it was expected from the high diffusivity

  20. Isotopic tailoring with 59Ni to study the effect of helium on microstructural evolution and mechanical properties of neutron-irradiated Fe-Cr-Ni alloys

    Garner, F.A.; Hamilton, M.L.; Greenwood, L.R.; Stubbins, J.F.; Oliver, B.M.

    1992-03-01

    Tensile testing on three model Fe-Cr-Ni alloys removed from four discharges of the 59 Ni isotopic doping experiment in FFTF-MOTA indicates that helium/dpa ratios typical of fusion reactors do not produce changes in the yield strength or elongation that are significantly different from those at much lower helium generation rates. It also appears that tensile properties approach a saturation level that is dependent only on the final irradiation temperature, but not prior temperature history or thermomechanical starting condition. The saturation in mechanical properties reflects a similar saturation in microstructure that is independent of starting condition. The successful conduct of an isotopic doping experiment was found to require post-irradiation measurement of the helium levels in order to compensate for uncertainties in the cross sections for burn-out and burn-in of 59 Ni and for uncertainties in neutron flux and spectra in the vicinity of the edge of the core

  1. Quadratic Poisson brackets compatible with an algebra structure

    Balinsky, A. A.; Burman, Yu.

    1994-01-01

    Quadratic Poisson brackets on a vector space equipped with a bilinear multiplication are studied. A notion of a bracket compatible with the multiplication is introduced and an effective criterion of such compatibility is given. Among compatible brackets, a subclass of coboundary brackets is described, and such brackets are enumerated in a number of examples.

  2. Electron impact excitation of helium: A ploarization correlation study of the 31P state at 40 eV incident energy

    Harris, C.L.; Dorio, L.A.; Neill, P.A.

    1996-01-01

    Recently the Convergent Close-Coupling calculations, (CCC), of Fursa and Bray have been very successful predicting the behavior of the electron impact coherence parameters (EICP) for electron impact excitation of helium. In the present experimental study the linear Stokes parameters P 1 and P 2 have been measured for He(3 1 P) excitation using the polarization correlation technique. Data will be presented for electron impact energies of 40eV and 50eV. At present no other experimental data is available at 40eV. At 50eV angular correlation data measured using the VUV 3 1 P-1 1 S photons are available only out to a maximum electron scattering angle of 85 degrees. Due to the disadvantageous differential cross section and 40:1 branching ratio in favor of the VUV decay, the uncertainties in the present data are large. However, at selected electron scattering angles they are sufficient to distinguish the lack of convergence of the CCC predictions for the 69 state calculations (CCC69) in comparison with the 75 state model (CCC75). In particular at 50 eV incident electron energy and 120 degrees scattering angle the charge cloud alignment angles predicted by the two calculations differ by 90 degrees

  3. Compatibility of structural materials with fusion reactor coolant and breeder fluids

    DeVan, J.H.

    1979-01-01

    Fusion reactors are characterized by a lithium-containing blanket, a heat transfer medium that is integral with the blanket and first wall, and a heat engine that couples to the heat transfer medium. A variety of lithium-containing substances have been identified as potential blanket materials, including molten lithium metal, molten LiF-BeF 2 , Pb-Li alloys, and solid ceramic compounds such as Li 2 O. Potential heat transfer media include liquid lithium, liquid sodium, molten nitrates, water, and helium. Each of these coolants and blankets requires a particular set of chemical and mechanical properties with respect to the associated reactor and heat engine structural materials. This paper discusses the materials factors that underlie the selection of workable combinations of blankets and coolants. It also addresses the materials compatibility problems generic to those blanket-coolant combinations currently being considered in reactor design studies. (orig.)

  4. Psychological compatibility of women's handball team

    Shalar O.G.

    2010-02-01

    Full Text Available The results of study of psychological compatibility of womanish handball commands are presented. The psychological climate of command is investigational. Certain and adapted methods of estimation of psychological compatibility in the command playing types of sport. Psychological tests allow to expose the strong and weak sides of psychology of sportsmen. These information can be used for more effective program of psychological preparation of sportsmen development. It is necessary to improve determination of separate individual qualities of personality of sportsmen.

  5. Preliminary Overview of a Helium Cooling System for the Secondary Helium Loop in VHTR-based SI Hydrogen Production Facilities

    Shin, Youngjoon; Cho, Mintaek; Kim, Dahee; Lee, Taehoon; Lee, Kiyoung; Kim, Yongwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    Nuclear hydrogen production facilities consist of a very high temperature gas-cooled nuclear reactor (VHTR) system, intermediate heat exchanger (IHX) system, and a sulfur-iodine (SI) thermochemical process. This study focuses on the coupling system between the IHX system and SI thermochemical process. To prevent the propagation of the thermal disturbance owing to the abnormal operation of the SI process components from the IHX system to the VHTR system, a helium cooling system for the secondary helium of the IHX is required. In this paper, the helium cooling system has been studied. The temperature fluctuation of the secondary helium owing to the abnormal operation of the SI process was then calculated based on the proposed coupling system model. Finally, the preliminary conceptual design of the helium cooling system with a steam generator and forced-draft air-cooled heat exchanger to mitigate the thermal disturbance has been carried out. A conceptual flow diagram of a helium cooling system between the IHX and SI thermochemical processes in VHTR-based SI hydrogen production facilities has been proposed. A helium cooling system for the secondary helium of the IHX in this flow diagram prevents the propagation of the thermal disturbance from the IHX system to the VHTR system, owing to the abnormal operation of the SI process components. As a result of a dynamic simulation to anticipate the fluctuations of the secondary helium temperature owing to the abnormal operation of the SI process components with a hydrogen production rate of 60 mol·H{sub 2}/s, it is recommended that the maximum helium cooling capacity to recover the normal operation temperature of 450 .deg. C is 31,933.4 kJ/s. To satisfy this helium cooling capacity, a U-type steam generator, which has a heat transfer area of 12 m{sup 2}, and a forced-draft air-cooled condenser, which has a heat transfer area of 12,388.67 m{sup 2}, are required for the secondary helium cooling system.

  6. Cryogenic filter method produces super-pure helium and helium isotopes

    Hildebrandt, A. F.

    1964-01-01

    Helium is purified when cooled in a low pressure environment until it becomes superfluid. The liquid helium is then filtered through iron oxide particles. Heating, cooling and filtering processes continue until the purified liquid helium is heated to a gas.

  7. Structure of biodiesel based bicontinuous microemulsions for environmentally compatible decontamination: A small angle neutron scattering and freeze fracture electron microscopy study.

    Wellert, S; Karg, M; Imhof, H; Steppin, A; Altmann, H-J; Dolle, M; Richardt, A; Tiersch, B; Koetz, J; Lapp, A; Hellweg, T

    2008-09-01

    Most toxic industrial chemicals and chemical warfare agents are hydrophobic and can only be solubilized in organic solvents. However, most reagents employed for the degradation of these toxic compounds can only be dissolved in water. Hence, microemulsions are auspicious media for the decontamination of a variety of chemical warfare agents and pesticides. They allow for the solubilization of both the lipophilic toxics and the hydrophilic reagent. Alkyl oligoglucosides and plant derived solvents like rapeseed methyl ester enable the formulation of environmentally compatible bicontinuous microemulsions. In the present article the phase behavior of such a microemulsion is studied and the bicontinuous phase is identified. Small angle neutron scattering (SANS) and freeze fracture electron microscopy (FFEM) measurements are used to characterize the structure of the bicontinuous phase and allow for an estimation of the total internal interface. Moreover, also the influence of the co-surfactant (1-pentanol) on the structural parameters of the bicontinuous phase is studied with SANS.

  8. Use of double and triple-ion irradiation to study the influence of high levels of helium and hydrogen on void swelling of 8-12% Cr ferritic-martensitic steels

    Kupriiyanova, Y. E.; Bryk, V. V.; Borodin, O. V.; Kalchenko, A. S.; Voyevodin, V. N.; Tolstolutskaya, G. D.; Garner, F. A.

    2016-01-01

    In accelerator-driven spallation (ADS) devices, some of the structural materials will be exposed to intense fluxes of very high energy protons and neutrons, producing not only displacement damage, but very high levels of helium and hydrogen. Unlike fission flux-spectra where most helium and hydrogen are generated by transmutation in nickel and only secondarily in iron or chromium, gas production in ADS flux-spectra are rather insensitive to alloy composition, such that Fe-Cr base ferritic alloys also generate very large gas levels. While ferritic alloys are known to swell less than austenitic alloys in fission spectra, there is a concern that high gas levels in fusion and especially ADS facilities may strongly accelerate void swelling in ferritic alloys. In this study of void swelling in response to helium and hydrogen generation, irradiation was conducted on three ferritic-martensitic steels using the Electrostatic Accelerator with External Injector (ESUVI) facility that can easily produce any combination of helium to dpa and/or hydrogen to dpa ratios. Irradiation was conducted under single, dual and triple beam modes using 1.8 MeV Cr+3, 40 keV He+, and 20 keV H+. In the first part of this study we investigated the response of dual-phase EP-450 to variations in He/dpa and H/dpa ratio, focusing first on dual ion studies and then triple ion studies, showing that there is a diminishing influence on swelling with increasing total gas content. In the second part we investigated the relative response of three alloys spanning a range of starting microstructure and composition. In addition to observing various synergisms between He and H, the most important conclusion was that the tempered martensite phase, known to lag behind the ferrite phase in swelling in the absence of gases, loses much of its resistance to void nucleation when irradiated at large gas/dpa levels.

  9. Use of double and triple-ion irradiation to study the influence of high levels of helium and hydrogen on void swelling of 8–12% Cr ferritic-martensitic steels

    Kupriiyanova, Y.E., E-mail: fomenkoj@kipt.kharkov.ua [National Science Centre Kharkov Institute of Physics and Technology, 1, Akademicheskaya St., Kharkov, 61108 (Ukraine); Bryk, V.V.; Borodin, O.V.; Kalchenko, A.S.; Voyevodin, V.N.; Tolstolutskaya, G.D. [National Science Centre Kharkov Institute of Physics and Technology, 1, Akademicheskaya St., Kharkov, 61108 (Ukraine); Garner, F.A. [Radiation Effects Consulting, Richland, WA 99354 (United States)

    2016-01-15

    In accelerator-driven spallation (ADS) devices, some of the structural materials will be exposed to intense fluxes of very high energy protons and neutrons, producing not only displacement damage, but very high levels of helium and hydrogen. Unlike fission flux-spectra where most helium and hydrogen are generated by transmutation in nickel and only secondarily in iron or chromium, gas production in ADS flux-spectra are rather insensitive to alloy composition, such that Fe–Cr base ferritic alloys also generate very large gas levels. While ferritic alloys are known to swell less than austenitic alloys in fission spectra, there is a concern that high gas levels in fusion and especially ADS facilities may strongly accelerate void swelling in ferritic alloys. In this study of void swelling in response to helium and hydrogen generation, irradiation was conducted on three ferritic-martensitic steels using the Electrostatic Accelerator with External Injector (ESUVI) facility that can easily produce any combination of helium to dpa and/or hydrogen to dpa ratios. Irradiation was conducted under single, dual and triple beam modes using 1.8 MeV Cr{sup +3}, 40 keV He{sup +}, and 20 keV H{sup +}. In the first part of this study we investigated the response of dual-phase EP-450 to variations in He/dpa and H/dpa ratio, focusing first on dual ion studies and then triple ion studies, showing that there is a diminishing influence on swelling with increasing total gas content. In the second part we investigated the relative response of three alloys spanning a range of starting microstructure and composition. In addition to observing various synergisms between He and H, the most important conclusion was that the tempered martensite phase, known to lag behind the ferrite phase in swelling in the absence of gases, loses much of its resistance to void nucleation when irradiated at large gas/dpa levels.

  10. Compatibility study of the different pole figures in one and the same specimen. Comparison between the results obtained by neutron and by X-ray diffraction

    Pernot, M.; Penelle, R.; Dervin, P.

    1981-01-01

    Development of a calculation to show directly the compatibility of the different pole figures in the same specimen is exposed. A review of the method by serial development is given. Experimental methods are described. The position of the anisotropy axes is determined. Compatibilities resulting from X-ray and from neutron diffraction is analysed [fr

  11. Spectroscopy of helium hydride and triatomic hydrogen molecules

    Ketterle, W.

    1986-07-01

    Helium hydride and triatomic hydrogen has been produced by charge exchange between fast mass selected beams of molecular ions and alkali vapor. Using this method, the first discrete spectra of helium hydride were obtained. Fine electronic transitions with resolved rotational structure were observed in the visible and near infrared. Four isotopic mixtures were studied. Furthermore the first lifetime measurement of triatomic hydrogen states were performed and compared to theoretical predictions. (orig.)

  12. THE POPULATION OF HELIUM-MERGER PROGENITORS: OBSERVATIONAL PREDICTIONS

    Fryer, Chris L.; Belczynski, Krzysztof; Bulik, Tomasz; Berger, Edo; Thöne, Christina; Ellinger, Carola

    2013-01-01

    The helium-merger gamma-ray burst (GRB) progenitor is produced by the rapid accretion onto a compact remnant (neutron star or black hole) when it undergoes a common envelope inspiral with its companion's helium core. This merger phase produces a very distinct environment around these outbursts and recent observations suggest that, in some cases, we are detecting the signatures of the past merger in the GRB afterglow. These observations allow us, for the first time, to study the specific features of the helium-merger progenitor. In this paper, we couple population synthesis calculations to our current understanding of GRB engines and common envelope evolution to make observational predictions for the helium-merger GRB population. Many mergers do not produce GRB outbursts and we discuss the implications of these mergers with the broader population of astrophysical transients.

  13. The adsorption of helium atoms on small cationic gold clusters.

    Goulart, Marcelo; Gatchell, Michael; Kranabetter, Lorenz; Kuhn, Martin; Martini, Paul; Gitzl, Norbert; Rainer, Manuel; Postler, Johannes; Scheier, Paul; Ellis, Andrew M

    2018-04-04

    Adducts formed between small gold cluster cations and helium atoms are reported for the first time. These binary ions, Aun+Hem, were produced by electron ionization of helium nanodroplets doped with neutral gold clusters and were detected using mass spectrometry. For a given value of n, the distribution of ions as a function of the number of added helium atoms, m, has been recorded. Peaks with anomalously high intensities, corresponding to so-called magic number ions, are identified and interpreted in terms of the geometric structures of the underlying Aun+ ions. These features can be accounted for by planar structures for Aun+ ions with n ≤ 7, with the addition of helium having no significant effect on the structures of the underlying gold cluster ions. According to ion mobility studies and some theoretical predictions, a 3-D structure is expected for Au8+. However, the findings for Au8+ in this work are more consistent with a planar structure.

  14. Technique to eliminate helium induced weld cracking in stainless steels

    Chin-An Wang; Chin, B.A.

    1992-01-01

    Experiments have shown that Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 Mpa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials

  15. Stellar pulsation and the abundance of helium

    Schmidt, E.G.

    1978-01-01

    It has been suggested that the appearance of nonvariable stars within the Cepheid strip could be explained by a range in the helium abundance of Population I stars. In order to study this possibility, spectra were obtained of the main-sequence B stars in the galactic cluster NGC 129, which contains a nonvariable Cepheid-strip star, and M25, which contains a relatively hot Cepheid. Unfortunately, several of the stars in these clusters turn out to be helium-weak stars. In NGC 129 two stars which appear normal give a normal abundance, while in M25 all of the observed stars have abnormally low abundances. The significance of the low abundance in M25 is not clear. The abundance in NGC 129 is not low enough to support the above suggestion. 4 figures, 2 tables

  16. Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

    S. S. Bulanov

    2015-06-01

    Full Text Available The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He^{3} ions, having almost the same penetration depth as He^{4} with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.

  17. The effect of green helium-neon laser on the healing of extraction wounds: histological study in rats

    Nicolli Filho, Walter Domingos; Picon, Luciana Christofolini; Okamoto, Tetuo; Cardenuto, Ney

    1993-01-01

    A histological study on healing of extraction wounds following laser irradiation, using a green He-Ne laser, was carried out in rats. The results suggest that this kind of treatment has no significant beneficial effect on bony wound healing. Proliferation of fibroblasts and formation of trabecular osteoid were found to be not more pro eminent within the irradiated group. (author)

  18. Studies on the feasibility of the LWRs waste-thorium in-core fuel cycle in the Gas Turbine-Modular Helium Reactor

    Talamo, Alberto

    2006-01-01

    The capability to operate on LWRs waste constitutes one of the major benefits of the Gas Turbine-Modular Helium Reactor; in this paper, it has been evaluated the possibility to incinerate the LWRs waste and to simultaneously breed fissile 233 U by fertile thorium. Since a mixture of pure 239 Pu-thorium has shown a quite poor neutron economy, the LWRs waste-thorium fuel performance has been also tested when plutonium and thorium are allocated in different TRISO particles. More precisely, when fissile and fertile actinides share the same TRISO kernel, the resonance at 0.29eV of the fission and capture microscopic cross sections of 239 Pu diminishes also the absorption rate of fertile 232 Th and thus it degrades the breeding process. Consequently, in the present studies, two different types of fuel have been utilized: the Driver Fuel, made of LWRs waste, and the Transmutation Fuel, made of fertile thorium. Since, in the thermal neutron energy range, the microscopic capture cross section of 232 Th is about 80-100 times smaller than the fission one of 239 Pu, setting thorium in particles with a large kernel and LWRs waste in particles with a small one makes the volume integrated reaction rates better equilibrated. At the light of the above consideration, which drives to load as much thorium as possible, for the Transmutation Fuel they have been selected the JAERI TRISO particles packed 40%; whereas, for the Driver Fuel they have been tested different packing fractions and kernel radii. Since no configuration allowed the reactor to work, the above procedure has been repeated when fertile particles are packed 20%; the latter choice permits over one year of operation, but the build up of 233 U represents only a small fraction of the depleted 239 Pu. Finally, the previous configuration has been also investigated when the fertile and fissile fuels share the same kernel or when the fertile fuel axially alternates with the fissile one. (author)

  19. The study of capability natural uranium as fuel cycle input for long life gas cooled fast reactors with helium as coolant

    Ariani, Menik, E-mail: menikariani@gmail.com; Satya, Octavianus Cakra; Monado, Fiber [Department of Physics, Faculty of Mathematics and Natural Sciences, Sriwijaya University, jl Palembang-Prabumulih km 32 Indralaya OganIlir, South of Sumatera (Indonesia); Su’ud, Zaki [Nuclear and Biophysics Research Division, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, jlGanesha 10, Bandung (Indonesia); Sekimoto, Hiroshi [CRINES, Tokyo Institute of Technology, 2-12-11N1-17 Ookayama, Meguro-Ku, Tokyo (Japan)

    2016-03-11

    The objective of the present research is to assess the feasibility design of small long-life Gas Cooled Fast Reactor with helium as coolant. GCFR included in the Generation-IV reactor systems are being developed to provide sustainable energy resources that meet future energy demand in a reliable, safe, and proliferation-resistant manner. This reactor can be operated without enrichment and reprocessing forever, once it starts. To obtain the capability of consuming natural uranium as fuel cycle input modified CANDLE burn-up scheme was adopted in this system with different core design. This study has compared the core with three designs of core reactors with the same thermal power 600 MWth. The fuel composition each design was arranged by divided core into several parts of equal volume axially i.e. 6, 8 and 10 parts related to material burn-up history. The fresh natural uranium is initially put in region 1, after one cycle of 10 years of burn-up it is shifted to region 2 and the region 1 is filled by fresh natural uranium fuel. This concept is basically applied to all regions, i.e. shifted the core of the region (i) into region (i+1) region after the end of 10 years burn-up cycle. The calculation results shows that for the burn-up strategy on “Region-8” and “Region-10” core designs, after the reactors start-up the operation furthermore they only needs natural uranium supply to the next life operation until one period of refueling (10 years).

  20. Tritium decay helium-3 effects in tungsten

    M. Shimada

    2017-08-01

    Full Text Available Tritium (T implanted by plasmas diffuses into bulk material, especially rapidly at elevated temperatures, and becomes trapped in neutron radiation-induced defects in materials that act as trapping sites for the tritium. The trapped tritium atoms will decay to produce helium-3 (3He atoms at a half-life of 12.3 years. 3He has a large cross section for absorbing thermal neutrons, which after absorbing a neutron produces hydrogen (H and tritium ions with a combined kinetic energy of 0.76 MeV through the 3He(n,HT nuclear reaction. The purpose of this paper is to quantify the 3He produced in tungsten by tritium decay compared to the neutron-induced helium-4 (4He produced in tungsten. This is important given the fact that helium in materials not only creates microstructural damage in the bulk of the material but alters surface morphology of the material effecting plasma-surface interaction process (e.g. material evolution, erosion and tritium behavior of plasma-facing component materials. Effects of tritium decay 3He in tungsten are investigated here with a simple model that predicts quantity of 3He produced in a fusion DEMO FW based on a neutron energy spectrum found in literature. This study reveals that: (1 helium-3 concentration was equilibrated to ∼6% of initial/trapped tritium concentration, (2 tritium concentration remained approximately constant (94% of initial tritium concentration, and (3 displacement damage from 3He(n,HT nuclear reaction became >1 dpa/year in DEMO FW.

  1. Detergent-compatible bacterial amylases.

    Niyonzima, Francois N; More, Sunil S

    2014-10-01

    Proteases, lipases, amylases, and cellulases are enzymes used in detergent formulation to improve the detergency. The amylases are specifically supplemented to the detergent to digest starchy stains. Most of the solid and liquid detergents that are currently manufactured contain alkaline enzymes. The advantages of using alkaline enzymes in the detergent formulation are that they aid in removing tough stains and the process is environmentally friendly since they reduce the use of toxic detergent ingredients. Amylases active at low temperature are preferred as the energy consumption gets reduced, and the whole process becomes cost-effective. Most microbial alkaline amylases are used as detergent ingredients. Various reviews report on the production, purification, characterization, and application of amylases in different industry sectors, but there is no specific review on bacterial or fungal alkaline amylases or detergent-compatible amylases. In this mini-review, an overview on the production and property studies of the detergent bacterial amylases is given, and the stability and compatibility of the alkaline bacterial amylases in the presence of the detergents and the detergent components are highlighted.

  2. Laser Spectroscopy of Antiprotonic Helium Atoms

    2002-01-01

    %PS205 %title\\\\ \\\\Following the discovery of metastable antiprotonic helium atoms ($\\overline{p}He^{+} $) at KEK in 1991, systematic studies of their properties were made at LEAR from 1991 to 1996. In the first two years the lifetime of $\\overline{p}He^{+}$ in liquid and gaseous helium at various temperatures and pressures was measured and the effect of foreign gases on the lifetime of these atoms was investigated. Effects were also discovered which gave the antiproton a 14\\% longer lifetime in $^4$He than in $^3$He, and resulted in important differences in the shape of the annihilation time spectra in the two isotopes.\\\\ \\\\Since 1993 laser spectroscopy of the metastable $\\overline{p}He^{+}$ atoms became the main focus of PS205. Transitions were stimulated between metastable and non-metastable states of the $\\overline{p}He^{+}$ atom by firing a pulsed dye laser beam into the helium target every time an identified metastable atom was present (Figure 1). If the laser frequency matched the transition energy, the...

  3. Bed system performance in helium circulation mode

    Kim, Yean Jin; Jung, Kwang Jin; Ahn, Do Hee; Chung, Hong Suk [UST, Daejeon (Korea, Republic of); Kang, Hee Suk [KAERI, Daejeon (Korea, Republic of); Yun, Sei Hun [NFRI, Deajeon (Korea, Republic of)

    2016-05-15

    As a part of the International Thermonuclear Experimental Reactor (ITER) Project, We have conducted an experiment for storing hydrogen to depleted uranium and zirconium cobalt. The helium blanket effect has been observed in experiments using metal hydrides. The collapse of the hydrogen isotopes are accompanied by the decay heat and helium-3. Helium-3 dramatically reduces the hydrogen isotope storage capacity by surrounding the metal. This phenomenon is called a helium blanket effect. In addition the authors are working on the recovery and removal techniques of helium-3. In this paper, we discuss the equipment used to test the helium blanket effect and the results of a helium circulation experiment. The helium-3 produced surrounds the storage material surface and thus disturbs the reaction of the storage material and the hydrogen isotope. Even if the amount of helium-3 is small, the storage capacity of the SDS bed significantly drops. This phenomenon is the helium blanket effect. To resolve this phenomenon, a circulating loop was introduced. Using a circulating system, helium can be separated from the storage material. We made a helium loop that includes a ZrCo bed. Then using a metal bellows pump, we tested the helium circulation.

  4. Fertilization compatibility of spawning corals

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set includes experimental results of fertilization assays to characterize genetic compatibility between individual parental genotypes. Targeted species...

  5. Renormalization-group study of superfluidity and phase separation of helium mixtures immersed in a disordered porous medium

    Lopatnikova, A.; Berker, A.N.

    1997-01-01

    Superfluidity and phase separation in 3 He- 4 He mixtures immersed in aerogel are studied by renormalization-group theory. The quenched disorder imposed by aerogel, both at the atomic level and at the geometric level, is included. The calculation is conducted via the coupled renormalization-group mappings, near and away from aerogel, of the quenched probability distributions of random interactions. Random-bond effects on the onset of superfluidity and random-field effects on superfluid-superfluid phase separation are seen. The quenched randomness causes the λ line of second-order phase transitions of superfluidity onset to reach zero temperature, in agreement with general predictions and experiments. The effects of the atomic and geometric randomness of aerogel are investigated separately and jointly. copyright 1997 The American Physical Society

  6. Ion implantation as a method of studying inhomogeneities in superconductors: results for indium films with embedded helium particles

    Fogel, N.Ya.; Moshenski, A.A.; Dmitrenko, I.M.

    1978-01-01

    The paper considers the applicability of ion implantation into superconductors to investigate inhomogeneity effects on their macroscopic properties. Noble-gas-ion implantation into thin superconducting films is shown to be a unique means of systematically studying these effects in a single sample. Data demonstrating the effect of inhomogeneities on the critical current, Isub(c) in the mixed state and phase-transition smearing in He + -ion-irradiated indium films are presented. First, experimental evidence was obtained to support the Larkin-Ovchinnikov theory which relates Isub(c) and the phase-transition smearing to inhomogeneities of the electron-electron interaction constant g(r) and the electron mean free path (r). Results are presented for parallel critical field anomalies in He-implanted indium films which are due to an implantation-induced anisotropy of xi(t). Changes in the critical parameters for the film resulting from the implantation are compared to structural changes. (Auth.)

  7. It is compatible the sport in scholar age with other social roles? A study through Self-Determination Theory

    Amado Alonso, Diana; Leo Marcos, Francisco Miguel; Sánchez Oliva, David; González Ponce, Inmaculada; López Chamorro, José María

    2012-01-01

    The main aim of this study was to examine the relationship between perception of conflict or utility of the sport regarding other social roles and self-determination level in young athletes, focusing on differences among these variables with respect to sex. Hence, we used a sample size of 1897 players from different sport modalities, 1378 male and 519 female. Participants filled a questionnaire to assess self-determination level and other to measure conflict between social roles. Results show...

  8. Wastes vitrification by plasma torch: study of a glass formulation compatible with a wide range of B wastes

    Poitou, S.; Richaud, D.; Fiquet, O.; Gramondi, P.; Massit, H.

    2001-01-01

    Within the context of radioactive waste management, CEA has equipped itself with a 'PLASMARC' device. The central element of this device is a plasma torch treatment furnace. It has been implemented and validated for the vitrification of low level radioactive wastes. Meanwhile, the plasma torch presents potentially interests for immobilizing under an inert form in vitreous matrices, B wastes which are generally divided and of complex chemical composition. The application of this process to this type of wastes has been studied here. The obtained results show that with the plasma torch it is possible to make glasses with a high amount of silicon and aluminium oxide and which are adapted to the treatment / packaging of the B wastes. (O.M.)

  9. A study on the compatibility between one-bottle dentin adhesives and composite resins using micro-shear bond strength.

    Song, Minju; Shin, Yooseok; Park, Jeong-Won; Roh, Byoung-Duck

    2015-02-01

    This study was performed to determine whether the combined use of one-bottle self-etch adhesives and composite resins from same manufacturers have better bond strengths than combinations of adhesive and resins from different manufacturers. 25 experimental micro-shear bond test groups were made from combinations of five dentin adhesives and five composite resins with extracted human molars stored in saline for 24 hr. Testing was performed using the wire-loop method and a universal testing machine. Bond strength data was statistically analyzed using two way analysis of variance (ANOVA) and Tukey's post hoc test. Two way ANOVA revealed significant differences for the factors of dentin adhesives and composite resins, and significant interaction effect (p composite resin (p composite resin than other manufacturer's composite resin. Not all combinations of adhesive and composite resin by same manufacturers failed to show significantly higher bond strengths than mixed manufacturer combinations.

  10. Pierre Gorce working on a helium pump.

    1975-01-01

    This type of pump was designed by Mario Morpurgo, to circulate liquid helium in superconducting magnets wound with hollow conductors. M. Morpurgo, Design and construction of a pump for liquid helium, CRYIOGENICS, February 1977, p. 91

  11. Convective mixing in helium white dwarfs

    Vauclair, G.; Fontaine, G.

    1979-01-01

    The conditions under which convective mixing episodes take place between the helium envelopes and the underlying carbon layers in helium-rich white dwarfs are investigated. It is found that, for essentially any value of the initial helium content less than the maximum mass a helium convection zone can have, mixing does occur, and leads, in the vast majority of cases, to an almost pure carbon superficial composition. Mixing products that show only traces of carbon while retaining helium-dominated envelopes are possible only if the initial helium content is quite close to the maximum possible mass of the helium convection zone. In the presence of turbulence, this restriction could be relaxed, however, and the helium-rich lambda4670 stars may possibly be explained in this fashion

  12. Problem-based learning and larger student groups: mutually exclusive or compatible concepts – a pilot study

    Lymn Joanne S

    2008-06-01

    Full Text Available Abstract Background Problem-based learning is recognised as promoting integration of knowledge and fostering a deeper approach to life-long learning, but is associated with significant resource implications. In order to encourage second year undergraduate medical students to integrate their pharmacological knowledge in a professionally relevant clinical context, with limited staff resources, we developed a novel clustered PBL approach. This paper utilises preliminary data from both the facilitator and student viewpoint to determine whether the use of this novel methodology is feasible with large groups of students. Methods Students were divided into 16 groups (20–21 students/group and were allocated a PBL facilitator. Each group was then divided into seven subgroups, or clusters, of 2 or 3 students wh each cluster being allocated a specific case. Each cluster was then provided with more detailed clinical information and studied an individual and distinct case-study. An electronic questionnaire was used to evaluate both student and facilitator perception of this clustered PBL format, with each being asked to rate the content, structure, facilitator effectiveness, and their personal view of the wider learning experience. Results Despite initial misgivings, facilitators managed this more complex clustered PBL methodology effectively within the time restraints and reported that they enjoyed the process. They felt that the cases effectively illustrated medical concepts and fitted and reinforced the students' pharmacological knowledge, but were less convinced that the scenario motivated students to use additional resources or stimulated their interest in pharmacology. Student feedback was broadly similar to that of the facilitators; although they were more positive about the scenario stimulating the use of additional resources and an interest in pharmacology. Conclusion This clustered PBL methodology can be successfully used with larger groups of

  13. It is compatible the sport in scholar age with other social roles? A study through Self-Determination Theory

    Amado Alonso, Diana

    2012-01-01

    Full Text Available The main aim of this study was to examine the relationship between perception of conflict or utility of the sport regarding other social roles and self-determination level in young athletes, focusing on differences among these variables with respect to sex. Hence, we used a sample size of 1897 players from different sport modalities, 1378 male and 519 female. Participants filled a questionnaire to assess self-determination level and other to measure conflict between social roles. Results showed that utility of sport was positive and significantly associated with self-determined motivation, whereas conflict between roles was related with amotivation. Moreover, male athletes showed higher scores in all types of motivation that refer Self-Determination Theory, being the group that perceived the greater incompatibility between sport and other social roles according to their growth age. As a conclusion, we emphasize the necessity to promote intrinsic motives of practice in both sex to increase commitment with the sport activity, and avoid sport dropout that might be happened because of the demands of other contexts that surround young athletes.

  14. Study of the /sup 233/Th(. gamma. ,xn)226,222/supTh/ reaction at. gamma. -energies <= 60 MeV using a helium jet

    Jungclas, H

    1974-01-01

    A helium jet system is set up for the transport and investigation of daughter products of the nuclear reaction /sup 232/Th (..gamma..,xn) at E/sub..gamma../<=60 MeV. The theoretical fundamentals for the target kinematics such as photoexcitation, evaporation cascade and range of heavy ions are presented. Activation experiments with thick thorium tetrafluoride targets and catcher foils for the reaction products emitted showed a nuclide-dependent forwards-backwards ratio which agrees with the calculated values within 1-2 standard deviations of the statistic error. A target system with thorium nitrate coated glass wool is tested with the helium in 'on-line' operation and after irradiation is used for the investigation of the long-lived activities with the excess pressure jet. The radioactive decay series of the transported reaction products are identified by alpha spectroscopy.

  15. Ab initio calculation of the interaction potentials of helium, neon, and methane as well as theoretical studies on their thermophysical properties and those of water vapor

    Hellmann, Robert

    2009-01-01

    Thermophysical properties of the pure gases helium, neon, methane and water vapor were calculated for low densities over wide temperature ranges. Statistical thermodynamics was used for the determination of the pressure virial coefficients. The kinetic theory of gases was utilized for the calculation of the transport and relaxation properties. So far kinetic theory was limited to linear molecules and has now been extended to molecules of arbitrary geometry to enable calculations on methane and water vapor. The interaction potentials, which are needed for all computations, were determined for helium, neon and methane from the supermolecular approach using quantum chemical ab initio methods. For water the interaction potentials were taken from the literature. The calculated values of the thermophysical properties for the four gases show very good agreement with the best experimental data. At very low and very high temperatures the theoretical values are more accurate than experimental data. (orig.)

  16. Surface acidity and solid-state compatibility of excipients with an acid-sensitive API: case study of atorvastatin calcium.

    Govindarajan, Ramprakash; Landis, Margaret; Hancock, Bruno; Gatlin, Larry A; Suryanarayanan, Raj; Shalaev, Evgenyi Y

    2015-04-01

    The objectives of this study were to measure the apparent surface acidity of common excipients and to correlate the acidity with the chemical stability of an acid-sensitive active pharmaceutical ingredient (API) in binary API-excipient powder mixtures. The acidity of 26 solid excipients was determined by two methods, (i) by measuring the pH of their suspensions or solutions and (ii) the pH equivalent (pHeq) measured via ionization of probe molecules deposited on the surface of the excipients. The chemical stability of an API, atorvastatin calcium (AC), in mixtures with the excipients was evaluated by monitoring the appearance of an acid-induced degradant, atorvastatin lactone, under accelerated storage conditions. The extent of lactone formation in AC-excipient mixtures was presented as a function of either solution/suspension pH or pHeq. No lactone formation was observed in mixtures with excipients having pHeq > 6, while the lactone levels were pronounced (> 0.6% after 6 weeks at 50°C/20% RH) with excipients exhibiting pHeq 6, 3-6, and < 3) were consistent with the reported solution pH-stability profile of AC. In contrast to the pHeq scale, lactone formation did not show any clear trend when plotted as a function of the suspension/solution pH. Two mechanisms to explain the discrepancy between the suspension/solution pH and the chemical stability data were discussed. Acidic excipients, which are expected to be incompatible with an acid-sensitive API, were identified based on pHeq measurements. The incompatibility prediction was confirmed in the chemical stability tests using AC as an example of an acid-sensitive API.

  17. Helium localization around the microscopic impurities embedded to liquid helium

    Gordon, E.B.; Shestakov, A.F.

    2000-01-01

    The structure and properties of the environment round the impurity atoms (Im) embedded in liquid helium are considered. It is shown that there are two qualitatively different types of structure of the He atom layer next to Im - attraction and repulsion structures. For the center attraction structure (strong Im-He interaction) the Im-He separation is longer than the equilibrium one for the pair Im-He potential, and the density and localization of He atoms are higher than in the bulk. It this case the He atom content in the layer, n, is almost independent of applied pressure. In the repulsion structure realized for alkaline metal atoms the Im-He separation is shorter than the equilibrium one and the density is lower than in the helium bulk. At T approx 1 K occupied are several states with different n and their energies differ only by approx 0.1 K, an increase in pressure resulting in a considerable reduction of n. The optical and EPR spectra of the atoms embedded to liquid and solid helium are interpreted on the basis of the analysis carried out. A simple model is proposed to evaluate the helium surroundings characteristics from the experimental pressure dependences of atomic line shifts in the absorption and emission spectra. The attraction structures in 3 He - 4 He mixtures are suggested to be highly enriched by 4 He atoms which the repulsion structures - by 3 He atoms. a possibility for existence of phase transitions in helium shells surrounding impurity atoms is considered

  18. Helium behaviour in aluminium under hydrostatic pressure

    Sokurskij, Yu.N.; Tebus, V.N.; Zudilin, V.A.; Tumanova, G.M.

    1989-01-01

    Effect of hydrostatic compression on equilibrium helium bubbles in low aluminium-lithium alloy irradiated in reactor at 570 K is investigated. Measurements of hydrostatic density and electron-microscopic investigations have shown, that application of up to 2 GPa pressure reduces equilibrium size of helium bubbles and reduces helium swelling. Kinetics and thermodynamics of the process are considered with application of 'rigid sphere' equation which describes helium state in bubbles

  19. Study on restriction method for end-wall boundary layer thickness in axial helium gas compressor for gas turbine high temperature gas cooled reactor

    Takada, Shoji; Takizuka, Takakazu; Yan, Xing; Kunitomi, Kazuhiko; Inagaki, Yoshiyuki

    2009-01-01

    Aerodynamic performance test was carried out using a 1/3 scale, 4-stage model of the helium gas compressor to investigate an effect of end-wall over-camber to prevent decrease of axial velocity in the end-wall boundary layer. The model compressor consists of a rotor, 500 mm in diameter, which is driven by an electric motor at a rotational speed of 10800 rpm. The rotor blade span of the first stage is 34 mm. The test was carried out under the condition that the helium gas pressure of 0.88 MPa, temperature of 30degC, and mass flow rate of 12.47 kg/s at the inlet. A 3-dimensional aerodynamic code, which was verified using the test data, showed that axial velocity was lowered by using a blade which increased the inlet blade angle around the end-wall region of the casing side in comparison with that using the original design blade, because the inlet flow angle mismatched with the inlet blade angle of the rotor blade, as opposed to the prediction by a conventional air compressor design method. The overall adiabatic efficiency of the full scale 20-stage helium gas compressor was predicted 89.7% from the Reynolds number dependency of the test data by using the original design blade. (author)

  20. Rotons, Superfluidity, and Helium Crystals

    Balibar, Sébastien

    2006-09-01

    Fritz London understood that quantum mechanics could show up at the macroscopic level, and, in 1938, he proposed that superfluidity was a consequence of Bose-Einstein condensation. However, Lev Landau never believed in London's ideas; instead, he introduced quasiparticles to explain the thermodynamics of superfluid 4He and a possible mechanism for its critical velocity. One of these quasiparticles, a crucial one, was his famous "roton" which he considered as an elementary vortex. At the LT0 conference (Cambridge, 1946), London criticized Landau and his "theory based on the shaky grounds of imaginary rotons". Despite their rather strong disagreement, Landau was awarded the London prize in 1960, six years after London's death. Today, we know that London and Landau had both found part of the truth: BEC takes place in 4He, and rotons exist. In my early experiments on quantum evaporation, I found direct evidence for the existence of rotons and for evaporation processes in which they play the role of photons in the photoelectric effect. But rotons are now considered as particular phonons which are nearly soft, due to some local order in superfluid 4He. Later we studied helium crystals which are model systems for the general study of crystal surfaces, but also exceptional systems with unique quantum properties. In our recent studies of nucleation, rotons show their importance again: by using acoustic techniques, we have extended the study of liquid 4He up to very high pressures where the liquid state is metastable, and we wish to demonstrate that the vanishing of the roton gap may destroy superfluidity and trigger an instability towards the crystalline state.

  1. Explosive helium burning in white dwarf stars

    Khokhlov, A.M. (AN SSSR, Moscow. Astronomicheskij Sovet)

    1984-04-01

    Helium burning kinetics in white dwarfs has been considered at constant temperatures T >= 10/sup 9/ K and densities rho >10/sup 5/ g/cm/sup 3/. It is found, that helium detonation in white dwarfs does not lead to formation of light (A < 56) elements. Thus, helium white dwarf model for supernova 1 is inconsistent with observations.

  2. Influence of short heat pulses on the helium boiling heat transfer rate

    Andreev, V.K.; Deev, V.I.; Savin, A.N.; Kutsenko, K.V.

    1987-01-01

    Investigation results on heat transfer in the process of helium boiling on a heated wall under conditions of pulsed heat effect are described. Results of the given study point to one of possible ways of heat exchange intensification in boiling helium by supplying short heat pulse to the heater. Even short-time noncontrolled or incidental increase in the heater capacity during experiment with boiling helium can result in a considerable disagreement of experimental data on heat transfer

  3. Muonium and neutral muonic helium

    Orth, H.

    1981-01-01

    In this brief article the current status on muonium spectroscopy with emphasis on recent developments will be summarized. The experimental and theoretical progress of the muonic helium atom will be reviewed. Future directions in this field of research will be discussed. (orig./HSI)

  4. Electric response in superfluid helium

    Chagovets, Tymofiy

    2016-01-01

    Roč. 488, May (2016), s. 62-66 ISSN 0921-4526 R&D Projects: GA ČR GP13-03806P Institutional support: RVO:68378271 Keywords : superfluid helium * electric response * second sound * ions in He II Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.386, year: 2016

  5. Production of negative helium ions

    Toledo, A.S. de; Sala, O.

    1977-01-01

    A negative helium ion source using potassium charge exchange vapor has been developed to be used as an injector for the Pelletron accelerator. 3 He and α beam currents of up to 2μA have been extracted with 75% particle transmission through the machine [pt

  6. Experimental evidence for the suitability of ELMing H-mode operation in ITER with regard to core transport of helium

    Wade, M.R.; Hillis, D.L.; Burrell, K.H.

    1996-09-01

    Studies have been conducted in DIII-D to assess the viability of the ITER design with regard to helium ash removal, including both global helium exhaust studies and detailed helium transport studies. With respect to helium ash accumulation, the results are encouraging for successful operation of ITER in ELMing H-mode plasmas with conventional high-recycling divertor operation. Helium can be removed from the plasma core with a characteristic time constant of ∼ 8 energy confinement times, even with a central source of helium. Furthermore, the exhaust rate is limited by the pumping efficiency of the system and not by transport of helium within the plasma core. Helium transport studies have shown that D He /X eff ∼ 1 in all confinement regimes studied to date and there is little dependence of D He /X eff on normalized gyroradius in dimensionless scaling studies, suggesting that D He /X eff will be ∼ 1 in ITER. These observations suggest that helium transport within the plasma core should be sufficient to prevent unacceptable fuel dilution in ITER. However, helium exhaust is also strongly dependent on many factors (e.g., divertor plasma conditions, plasma and baffling geometry, flux amplification, pumping speed, etc.) that are difficult to extrapolate. Studies have revealed the helium diffusivity decreases as the plasma density increases, which is unfavorable to ITER's extremely high density operation

  7. Helium production technology based on natural gas combustion and beneficial use of thermal energy

    Nakoryakov Vladimir E.

    2016-01-01

    Full Text Available Helium is widely used in all industries, including power plant engineering. In recent years, helium is used in plants operating by the Brayton cycle, for example, in the nuclear industry. Using helium-xenon mixture in nuclear reactors has a number of advantages, and this area is rapidly developing. The hydrodynamics and mass transfer processes in single tubes with various cross-sections as well as in inter-channel space of heating tube bundle were studied at the Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences. Currently, there is a strongest shortage in helium production. The main helium production method consists in the liquefaction of the natural gas and subsequent separation of helium from remaining gas with its further purification using membranes.

  8. Low temperature calorimetry and transmission electron microscopy of helium bubbles in Cu

    Syskakis, E.

    1985-08-01

    Helium has been introduced into 100 μm thick pure Cu specimens by implantation of α-particles at T = 300 K. Post-implantation annealing of the specimens at high temperatures caused helium to precipitate into bubbles. We have measured the low-temperature heat capacity of helium confined in bubbles of average radius of less than 100 A. The size of the bubbles was obtained by transmission electron microscope investigations. We have observed that helium liquifies at low temperatures and undergoes the transition to the superfluid state in bubbles of average radius larger than 35 A. The confining geometry of bubbles is new and possesses unique features for investigations of confined helium. It provides the possibility to study properties of extremely small, spherical, completely isolated Bose ''particles'' consisting of 10 4 helium atoms each. Furthermore, as we show, it can be known with better accuracy than formerly investigated confining geometries. (orig./BHO)

  9. Modeling of helium bubble nucleation and growth in neutron irradiated boron doped RAFM steels

    Dethloff, Christian; Gaganidze, Ermile; Svetukhin, Vyacheslav V.; Aktaa, Jarir

    2012-01-01

    Reduced activation ferritic/martensitic (RAFM) steels are promising candidates for structural materials in future fusion technology. In addition to other irradiation defects, the transmuted helium is believed to strongly influence material hardening and embrittlement behavior. A phenomenological model based on kinetic rate equations is developed to describe homogeneous nucleation and growth of helium bubbles in neutron irradiated RAFM steels. The model is adapted to different 10 B doped EUROFER97 based heats, which already had been studied in past irradiation experiments. Simulations yield bubble size distributions, whereby effects of helium generation rate, surface energy, helium sinks and helium density are investigated. Peak bubble diameters under different conditions are compared to preliminary microstructural results on irradiated specimens. Helium induced hardening was calculated by applying the Dispersed Barrier Hardening model to simulated cluster size distributions. Quantitative microstructural investigations of unirradiated and irradiated specimens will be used to support and verify the model.

  10. Modeling of helium bubble nucleation and growth in neutron irradiated boron doped RAFM steels

    Dethloff, Christian, E-mail: christian.dethloff@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Gaganidze, Ermile [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Svetukhin, Vyacheslav V. [Ulyanovsk State University, Leo Tolstoy Str. 42, 432970 Ulyanovsk (Russian Federation); Aktaa, Jarir [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2012-07-15

    Reduced activation ferritic/martensitic (RAFM) steels are promising candidates for structural materials in future fusion technology. In addition to other irradiation defects, the transmuted helium is believed to strongly influence material hardening and embrittlement behavior. A phenomenological model based on kinetic rate equations is developed to describe homogeneous nucleation and growth of helium bubbles in neutron irradiated RAFM steels. The model is adapted to different {sup 10}B doped EUROFER97 based heats, which already had been studied in past irradiation experiments. Simulations yield bubble size distributions, whereby effects of helium generation rate, surface energy, helium sinks and helium density are investigated. Peak bubble diameters under different conditions are compared to preliminary microstructural results on irradiated specimens. Helium induced hardening was calculated by applying the Dispersed Barrier Hardening model to simulated cluster size distributions. Quantitative microstructural investigations of unirradiated and irradiated specimens will be used to support and verify the model.

  11. On the shear strength of tungsten nano-structures with embedded helium

    Smirnov, R.D.; Krasheninnikov, S.I.

    2013-01-01

    Modification of plastic properties of tungsten nano-structures under shear stress load due to embedded helium atoms is studied using molecular dynamics modelling. The modelling demonstrates that the yield strength of tungsten nano-structures reduces significantly with increasing embedded helium concentration. At high helium concentrations (>10 at%), the yield strength decreases to values characteristic to the pressure in helium nano-bubbles, which are formed in tungsten under such conditions and thought to be responsible for the formation of nano-fuzz on tungsten surfaces irradiated with helium plasma. It is also shown that tungsten plastic flow strongly facilitates coagulation of helium clusters to larger bubbles. The temperature dependencies of the yield strength are obtained. (letter)

  12. Development Status of the Helium Circulator for the HCS of HCCR-TBS

    Lee, Eo Hwak; Jin, Hyung Gon; Yoon, Jae Sung; Kim, Suk Kwon; Lee, Dong Won; Lee, Si Woo; Cho, Seung Yon

    2016-01-01

    The calculated eddy current loss on the stainless steel sealing cap of the magnetic coupling device is very high. To solve the eddy current loss problem of the sealing cap, a glass fiber composite, non-conductive and high strength material, is adapted as a material of the sealing cap. The HCCR TBM will be cooled down by HCS (Helium Cooling System), supply high pressure (8 MPa) and temperature (300 .deg. C) helium coolant with 1.15 kg/s of mass flow for nominal operation. The real-scale helium circulator, which is main component of the HCS, has been developed since 2014. In present study, design and manufacture progress of the helium circulator and its verification test plan are described. The real-scale circulator has been developed to provide high temperature and pressure of helium flow as a coolant of the HCCR TBM. To prevent helium leakage, magnetic coupling design was adapted between the shaft and the impeller

  13. Field investigation with regard to the impermeability of clay formations. Helium-4 soil gas surveys in sedimentary basins as a tentative study of secondary permeability in clayey sequences

    Lombardi, S.; Benvegnu, F.; Brondi, A.; Polizzano, C.

    1993-01-01

    This report deals with a tentative study for the detection of the secondary permeability in clayey formations conducted in several sedimentary basins in Central Italy, by means of geochemical methods. The main purposes are: to try a geochemical method, based on the distribution of deep origin gases in soil gas ( 4 He and 222 Rn), to detect buried fault systems and to study the permeability of clay as a potential migration pathway for nuclides of radioactive waste deposits; to verify the effectiveness of this method for the selection of suitable sites for radwaste disposal. This research programme consists in a collaboration between ENEA and the University of Rome within the communitarian programme for the disposal of high level and long-live radwaste. Investigations concerned sedimentary basins filled by sand-clay formations 1000-2000 meters thick and characterized by different tectonic: Era and Chiani-Paglia Valleys (Tuscany and North Latium), structural trenches due to extensive tectonics along the tyrrhenian edge, and Vasto region, a basin in the 'Adriatic foretrench', characterized by compressive tectonics. The investigated areas are near or directly correspond to geothermal fields or to hydrocarbon reservoirs supplying gases which may migrate upward along fractures. Almost 4000 soil gas samples were collected in the three surveyed areas; the sampling density was of about 1.5 points / km 2 , normally used in the regional scale surveys. The obtained results show that the observed helium anomalies are distributed or elongated according to the main tectonic features of the substratum (fault systems, fractures, deep structures); the magnitude of anomalies seems to correlate with the nature of the deep gas reservoir (i.e. oil in Vasto), geothermal reservoir in the Paglia valley. These observations seem to confirm that the presence of deep origin gases in soils is controlled by tectonics. Clay thickness does not significantly control the uprising of deep gases: in

  14. Production of lipase and protease from an indigenous Pseudomonas aeruginosa strain and their evaluation as detergent additives: compatibility study with detergent ingredients and washing performance.

    Grbavčić, Sanja; Bezbradica, Dejan; Izrael-Živković, Lidija; Avramović, Nataša; Milosavić, Nenad; Karadžić, Ivanka; Knežević-Jugović, Zorica

    2011-12-01

    An indigenous Pseudomonas aeruginosa strain has been studied for lipase and protease activities for their potential application in detergents. Produced enzymes were investigated in order to assess their compatibility with several surfactants, oxidizing agents and commercial detergents. The crude lipase appeared to retain high activity and stability in the presence of several surfactants and oxidizing agents and it was insusceptible to proteolysis. Lutensol® XP80 and Triton® X-100 strongly activated the lipase for a long period (up to 40 and 30% against the control after 1h) while the protease activity was enhanced by the addition of Triton® WR1339 and Tween® 80. The washing performance of the investigated surfactants was significantly improved with the addition of the crude enzyme preparation. Studies were further undertaken to improve enzymes production. The optimization of fermentation conditions led to an 8-fold increase of lipase production, while the production of protease was enhanced by 60%. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Simplicity works for superfluid helium

    Bowley, Roger

    2000-01-01

    The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

  16. Simplicity works for superfluid helium

    Bowley, Roger [University of Nottingham, Nottingham (United Kingdom)

    2000-02-01

    The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

  17. Growth rate effects on the formation of dislocation loops around deep helium bubbles in Tungsten

    Sandoval, Luis; Perez, Danny; Uberuaga, Blas P.; Voter, Arthur Ford

    2016-01-01

    Here, the growth process of spherical helium bubbles located 6 nm below a (100) surface is studied using molecular dynamics and parallel replica dynamics simulations, over growth rates from 10"6 to 10"1"2 helium atoms per second. Slower growth rates lead to a release of pressure and lower helium content as compared with fast growth cases. In addition, at slower growth rates, helium bubbles are not decorated by multiple dislocation loops, as these tend to merge or emit given sufficient time. At faster rates, dislocation loops nucleate faster than they can emit, leading to a more complicated dislocation structure around the bubble.

  18. Simulation study of the second-generation MR-compatible SPECT system based on the inverted compound-eye gamma camera design

    Lai, Xiaochun; Meng, Ling-Jian

    2018-02-01

    In this paper, we present simulation studies for the second-generation MRI compatible SPECT system, MRC-SPECT-II, based on an inverted compound eye (ICE) gamma camera concept. The MRC-SPECT-II system consists of a total of 1536 independent micro-pinhole-camera-elements (MCEs) distributed in a ring with an inner diameter of 6 cm. This system provides a FOV of 1 cm diameter and a peak geometrical efficiency of approximately 1.3% (the typical levels of 0.1%-0.01% found in modern pre-clinical SPECT instrumentations), while maintaining a sub-500 μm spatial resolution. Compared to the first-generation MRC-SPECT system (MRC-SPECT-I) (Cai 2014 Nucl. Instrum. Methods Phys. Res. A 734 147-51) developed in our lab, the MRC-SPECT-II system offers a similar resolution with dramatically improved sensitivity and greatly reduced physical dimension. The latter should allow the system to be placed inside most clinical and pre-clinical MRI scanners for high-performance simultaneous MRI and SPECT imaging.

  19. Compatibility study of a parenteral microdose polyethylene glycol formulation in medical devices and identification of degradation impurity by 2D-LC/MS.

    Dai, Lulu; Yeh, Geoffrey K; Ran, Yingqing; Yehl, Peter; Zhang, Kelly

    2017-04-15

    Polyethylene glycol (PEG) based formulation and polyvinylchloride (PVC) tubing are frequently used for drug delivery and administration. The compatibility of a parenteral drug microdose formulation in intravenous infusion (IV) devices was studied to support the clinical determination of absolute bioavailability by the microdosing method. The investigational microdose formulation containing PEG was found prone to significant loss of potency within hours of storage in the PVC IV tubing due to degradation. Degradation occurred only when both PEG and PVC tubing were present. The degradation product could not be detected by LC/MS due to the significant interference from the high concentration of PEG (4%) matrix and the extremely low level of drug (0.6ppm). To obtain structural information of the degradation impurity and understand the cause of the degradation, a simple heart-cutting 2D-LC/MS approach was utilized to effectively separate the impurity from the complex PEG oligomers and overcome the matrix interference, enabling mass spectrometric analysis of the impurity. An oxidation- dominated mechanism was proposed in which the combination of PEG auto-oxidation and dehydrochlorination of the PVC tubing yielded an oxidative environment that enhanced radical propagation and accelerated degradation of the investigational parent drug. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Interface strength of SiC/SiC composites with and without helium implantation using micro-indentation test

    Saito, M.; Ohtsuka, S.

    1998-01-01

    Helium implantation effects on interface strength of SiC/SiC composite were studied using the micro-indentation fiber push-out method. Helium implantation was carried out with an accelerator at about 400 K. Total amount of implanted helium was approximately 10000 appm. Increase of the fiber push-in load was observed in as-implanted specimen. After post-implantation-annealing at 1673 K for 1 h, the change of the fiber push-in load by helium implantation was not observed. Effects of helium implantation on the interface are discussed. (orig.)

  1. HeREF-2003: Helium Refrigeration Techniques

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 Cost per participant: 500.- CHF Language: Bilingual English...

  2. HeREF-2003 : Helium Refrigeration Techniques

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. • Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 • Cost per participant: 500.- CHF ...

  3. Compatibility of heat resistant alloys with boron carbide, (4)

    Baba, Sinichi; Saruta, Toru; Ooka, Kiichi; Tanaka, Isao; Aoyama, Isao

    1985-07-01

    This paper relates to the compatibility test of control rod sheath (Hastelloy XR alloy) and neutron absorber (boronated graphite) for the VHTR, which has been researched and developed by JAERI. The irradiation was conducted by using the OGL-1 irradiation facility in the JMTR in order to study reaction behaviour between Hastelloy XR alloy and boronated graphite as well as to determine a reaction barrier performance of refractory metal foils Nb, Mo, W and Re. Irradiation conditions were as follows. Neutron dose : 4.05 x 10 22 m -2 (E 18 m -2 (E > 0.16 pJ, 1 Mev). Helium coolant : Average temperature 855 0 C, Pressure 2.94 MPa, Total impurity concentration 400 kBq/m 3 . Irradiation time : 5.0 Ms (1390 hours). Post-irradiation examinations i.e. visual inspection, dimensional inspection, weight measurement, metallography, hardness test, morphological observations by SEM and analysis of element distributions by EPMA were carried out. In the result, reaction products of Hastelloy XR alloy were observed in the ellipsoidal form locally. These results were same as those of the out-of-pile tests. Obvious irradiation effects were not detectable but a little accelarated increase in reaction depth of Hastelloy XR alloy by heat effect of specimens was observed. The refractory metal foils had a good performance of reaction barrier between Hastelloy XR alloy and boronated graphite. Furthermore, movement of Ni, Fe and Cr in the reaction area of Hastelloy XR alloy, difference in the reaction depth of B and C, irradiation effects on diffusion coefficient, lithium production and heat effect are discussed. (author)

  4. The work compatibility improvement framework: preliminary findings of a case study for defining and measuring the human-at-work system.

    Genaidy, A; Karwowski, W; A-Rehim, A

    2007-11-01

    Although researchers traditionally examined the 'risk' characteristics of work settings in health studies, few work models, such as the 'demand-control' and 'motivation-hygiene theory', advocated the study of the positive and the negative aspects of work for the ultimate improvement of work performance. The objectives of the current study were: (a) to examine the positive and negative characteristics of work in the machining department in a small manufacturing plant in the Midwest USA, and, (b) to report the prevalence of musculoskeletal and stress outcomes. A focus group consisting of worker experts from the different job categories in the machining department confirmed the management's concerns. Accordingly, 56 male and female workers, employed in three shifts, were surveyed on the demand/energizer profiles of work characteristics and self-reported musculoskeletal/stress symptoms. On average, one-fourth to one-third of the workers reported 'high' demand, and over 50% of the workers documented 'low' energizers for certain work domains/sub-domains, such as 'physical task content'/'organizational' work domains and 'upper body postural loading'/'time organization' work sub-domains. The prevalence of workers who reported 'high' musculoskeletal/stress disorder cases, was in the range of 25-35% and was consistent with the results of 'high' demands and 'low' energizers. The results of this case study confirm the importance of adopting a comprehensive view for work improvement and sustainable growth opportunities. It is paramount to consider the negative and positive aspects of work characteristics to ensure optimum organizational performance. The Work Compatibility Improvement Framework, proposed in the reported research, is an important endeavor toward the ultimate improvement and sustainable growth of human and organizational performance.

  5. Effects of Impurity on the Corrosion Behavior of Alloy 617 in the Helium Environment

    Jung, Sujin; Kim, Dong Jin; Lee, Gyeong Geun

    2013-01-01

    The helium coolant in the primary circuit inevitably includes minor impurities such as H 2 , CO, CH 4 , and H 2 O under operating condition. Material degradation is aggravated through oxidation, carburization, and decarburization under the impure helium environment. In this study, high-temperature corrosion tests were carried out at 850-950 .deg. C in the impure helium environment. The mass changes of the specimens were measured and the microstructures were analyzed quantitatively. In addition, all corrosion tests were conducted in the pure helium environment and the results were compared to the results under the impure helium. Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures under the impure helium environment. All specimens had similar microstructure in the outer Cr-oxide layers, internal Al-oxides, and carbide-depleted zone. The weight increase of the corroded specimens in the pure helium was relatively reduced. Microstructure result, oxide layer and carbide depleted zone were hardly ever observed. The impurity in helium affected the corrosion behavior of Alloy 617 and may cause a decrease in the mechanical properties. Therefore, the control of minor impurities in VHTR helium is necessary for the application of Alloy 617 to the IHX material of a VHTR

  6. Hot helium flow test facility summary report

    1980-06-01

    This report summarizes the results of a study conducted to assess the feasibility and cost of modifying an existing circulator test facility (CTF) at General Atomic Company (GA). The CTF originally was built to test the Delmarva Power and Light Co. steam-driven circulator. This circulator, as modified, could provide a source of hot, pressurized helium for high-temperature gas-cooled reactor (HTGR) and gas-cooled fast breeder reactor (GCFR) component testing. To achieve this purpose, a high-temperature impeller would be installed on the existing machine. The projected range of tests which could be conducted for the project is also presented, along with corresponding cost considerations

  7. Study On Electromagnetic Compatibility of Powerline Communication Systems%电力线通信系统的电磁兼容性研究

    郭晓刚; 赵建峰; 李国庆

    2017-01-01

    电磁兼容性(Electromagnetic Compatibility,EMC)是电力线通信(Power Line Communication,PLC)系统的关键技术之一.首先介绍了PLC技术的发展概况和相应EMC研究的基本情况;并介绍了有代表性的国家或地区和重要的标准化组织在PLC技术的EMC法律法规和标准方面的最新进展;然后介绍了我国在该领域的试验结果和研究成果;最后指出该领域存在的问题、同时对发展方向提出建议.上述研究总结了PLC技术的EMC法规和标准化的最新进展,可作为我国发展PLC时制定合理的EMC法规和管理制度的有益参考.%EMC is one of the key technologies of PLC.Firstly,the development profile of PLC technology and its EMC study overview were introduced in the paper.Then the PLC EMC progresses on the regulations of representative countries or regions,as well as the standards of the important standardized organizations were described.After that,the testing results and the study achievements of some Chinese organizations were presented.Finally,the problems were pointed out,and some suggestions on development directions were proposed.The study is the summary of the latest status of PLC EMC regulations and standardization,which is a favorable reference for making the rules and administration of PLC EMC for China.

  8. Limitations of superfluid helium droplets as host system revealed by electronic spectroscopy of embedded molecules

    Premke, Tobias

    2016-02-19

    Superfluid helium nanodroplets serve a unique cryogenic host system ideal to prepare cold molecules and clusters. Structures as well as dynamic processes can be examined by means of high resolution spectroscopy. Dopant spectra are accompanied by helium-induced spectroscopic features which reveal information on the dopant to helium interaction. For this reason the experimental research focuses on the investigation of such helium-induced effects in order to provide new information on the microsolvation inside the droplets. Since the quantitative understanding of helium-induced spectral features is essential to interpret molecular spectra recorded in helium droplets, this study contributes further experimental details on microsolvation in superfluid helium droplets. For this purpose two contrary systems were examined by means of high resolution electronic spectroscopy. The first one, phthalocyanine (Pc), is a planar organic molecule offering a huge and planar surface to the helium atoms and thus, the non-superfluid helium solvation layer can form different structures. The second system is iodine and in contrast to Pc it is of simple molecular shape. That means that in this case different complex structures of the non-superfluid helium solvation layer and the dopant can be expected to be avoided. Thus, both molecules should show clear differences in their microsolvation behavior. In this work a detailed examination of different spectroscopic properties of phthalocyanine is given by means of fluorescence excitation and dispersed emission spectroscopy. It raises legitimate doubts about the assignment of experimentally observed signals to features predicted by the model of the microsolvation. Even though there are no experimental observations which disprove the empirical model for the solvation in helium droplets, an unambiguous assignment of the helium-induced spectroscopic structures is often not possible. In the second part of this work, the investigation of the

  9. Influence of ion implanted helium on deuterium trapping in Kh18N10T stainless steel

    Tolstolutskaya, G.D.; Ruzhitskij, V.V.; Kopanets, I.E.

    2004-01-01

    The results are presented on evolution of distribution profiles and helium and deuterium thermal desorption ion implanted in steel 18Cr10NiTi. Accumulation, trapping, retention and microstructure evolution are studied; effect helium and hydrogen simultaneous implantation on these processes is also studied

  10. Imprints from the solar cycle on the helium atom and helium pickup ion distributions

    D. Rucinski

    Full Text Available Neutral interstellar helium atoms penetrate into the solar system almost unaffected by gas–plasma interactions in the heliospheric interface region, and thus can be considered as carriers of original information on the basic parameters (like density, temperature, bulk velocity of the Very Local Interstellar Medium (VLISM. Such information can nowadays be derived from analysis of data obtained from different experimental methods: in situ measurements of He atoms (Ulysses, observations of the solar backscattered He 584 A radiation (EUVE, in situ measurements of He + pickup ions (AMPTE, Ulysses, Wind, SOHO, ACE. In view of the current coordinated international ISSI campaign devoted to the study of the helium focusing cone structure and its evolution, we analyze expected variations of neutral He density, of He + pickup fluxes and of their phase space distributions at various phases of the solar activity cycle based on a realistic time-dependent modelling of the neutral helium and He + pickup ion distributions, which reflect solar cycle-induced variations of the photoionization rate. We show that the neutral helium density values are generally anticorrelated with the solar activity phase and in extreme cases (near the downwind axis the maximum-to-minimum density ratio may even exceed factors of ~ 3 at 1 AU. We also demonstrate that in the upwind hemisphere (at 1 AU and beyond the He + fluxes are correlated with the solar cycle activity, whereas on the downwind side the maximum of the expected flux up to distances of ~ 3 AU occurs around solar minimum epoch, and only further away does the correlation with solar activity become positive. Finally, we present the response of the phase space distribution spectra of He + pickup ions (in the solar wind frame for different epochs of the solar cycle and heliocentric distances from 1 to 5 AU covering the range of Ulysses, Wind and ACE observations.

    Key words. Solar physics, astrophysics and astronomy

  11. Imprints from the solar cycle on the helium atom and helium pickup ion distributions

    D. Rucinski

    2003-06-01

    Full Text Available Neutral interstellar helium atoms penetrate into the solar system almost unaffected by gas–plasma interactions in the heliospheric interface region, and thus can be considered as carriers of original information on the basic parameters (like density, temperature, bulk velocity of the Very Local Interstellar Medium (VLISM. Such information can nowadays be derived from analysis of data obtained from different experimental methods: in situ measurements of He atoms (Ulysses, observations of the solar backscattered He 584 A radiation (EUVE, in situ measurements of He + pickup ions (AMPTE, Ulysses, Wind, SOHO, ACE. In view of the current coordinated international ISSI campaign devoted to the study of the helium focusing cone structure and its evolution, we analyze expected variations of neutral He density, of He + pickup fluxes and of their phase space distributions at various phases of the solar activity cycle based on a realistic time-dependent modelling of the neutral helium and He + pickup ion distributions, which reflect solar cycle-induced variations of the photoionization rate. We show that the neutral helium density values are generally anticorrelated with the solar activity phase and in extreme cases (near the downwind axis the maximum-to-minimum density ratio may even exceed factors of ~ 3 at 1 AU. We also demonstrate that in the upwind hemisphere (at 1 AU and beyond the He + fluxes are correlated with the solar cycle activity, whereas on the downwind side the maximum of the expected flux up to distances of ~ 3 AU occurs around solar minimum epoch, and only further away does the correlation with solar activity become positive. Finally, we present the response of the phase space distribution spectra of He + pickup ions (in the solar wind frame for different epochs of the solar cycle and heliocentric distances from 1 to 5 AU covering the range of Ulysses, Wind and ACE observations.Key words. Solar physics, astrophysics and astronomy

  12. Compatible Spatial Discretizations for Partial Differential Equations

    Arnold, Douglas, N, ed.

    2004-11-25

    From May 11--15, 2004, the Institute for Mathematics and its Applications held a hot topics workshop on Compatible Spatial Discretizations for Partial Differential Equations. The numerical solution of partial differential equations (PDE) is a fundamental task in science and engineering. The goal of the workshop was to bring together a spectrum of scientists at the forefront of the research in the numerical solution of PDEs to discuss compatible spatial discretizations. We define compatible spatial discretizations as those that inherit or mimic fundamental properties of the PDE such as topology, conservation, symmetries, and positivity structures and maximum principles. A wide variety of discretization methods applied across a wide range of scientific and engineering applications have been designed to or found to inherit or mimic intrinsic spatial structure and reproduce fundamental properties of the solution of the continuous PDE model at the finite dimensional level. A profusion of such methods and concepts relevant to understanding them have been developed and explored: mixed finite element methods, mimetic finite differences, support operator methods, control volume methods, discrete differential forms, Whitney forms, conservative differencing, discrete Hodge operators, discrete Helmholtz decomposition, finite integration techniques, staggered grid and dual grid methods, etc. This workshop seeks to foster communication among the diverse groups of researchers designing, applying, and studying such methods as well as researchers involved in practical solution of large scale problems that may benefit from advancements in such discretizations; to help elucidate the relations between the different methods and concepts; and to generally advance our understanding in the area of compatible spatial discretization methods for PDE. Particular points of emphasis included: + Identification of intrinsic properties of PDE models that are critical for the fidelity of numerical

  13. Helium-induced weld cracking in austenitic and martensitic steels

    Lin, H.T.; Chin, B.A.

    1991-01-01

    Helium was uniformly implanted into type 316 stainless steel and Sandvik HT-9 (12Cr-1MoVW) to levels of 0.18 to 256 and 0.3 to 1 a.p.p.m., respectively, using the ''tritium trick'' technique. Autogenous bead-on-plate, full penetration, welds were then produced under fully constrained conditions using the gas tungsten arc welding (GTAW) process. The control and hydrogen-charged plates of both alloys were sound and free of any weld defects. For the 316 stainless steel, catastrophic intergranular fracture occurred in the heat-affected zone (HAZ) of welds with helium levels ≥ 2.5 a.p.p.m. In addition to the HAZ cracking, brittle fracture along the centreline of the fusion zone was also observed for the welds containing greater than 100 a.p.p.m. He. For HT-9, intergranular cracking occurred in the HAZ along prior-austenite grain boundaries of welds containing 1 a.p.p.m. He. Electron microscopy observations showed that the cracking in the HAZ originated from the growth and coalescence of grain-boundary helium bubbles and that the fusion-zone cracking resulted from the growth of helium bubbles at dendrite boundaries. The bubble growth kinetics in the HAZ is dominated by stress-induced diffusion of vacancies into bubbles. Results of this study indicate that the use of conventional GTAW techniques to repair irradiation-degraded materials containing even small amounts of helium may be difficult. (author)

  14. Randomized, Observer-blind, Split-face Compatibility Study with Clindamycin Phosphate 1.2%/Benzoyl Peroxide 3.75% gel and Facial Foundation Makeup.

    Bhatia, Neal; Pillai, Radhakrishnan

    2015-09-01

    Cosmetic compatibility in the treatment of acne is an important issue significantly impacting quality of life, but often overlooked, as dermatologists commonly recommended avoidance of cosmetic foundations when treating adult female patients. Fixed combinations of clindamycin/benzoyl peroxide are widely used in the treatment of acne, but little is known about the impact of their concomitant use with facial foundation. To assess the compatibility of clindamycin phosphate 1. 2%/benzoyl peroxide 3. 75% gel with foundation makeup for up to six hours after application. Twenty-nine female subjects applied makeup to their face after randomly applying clindamycin phosphate 1. 2%/benzoyl peroxide 3. 75% gel to one side of the face. Investigator and subject self- assessment included facial skin attributes, facial tolerability, and cosmetic compatibility post-application and at Hour 6; as well as cutaneous tolerability. No statistical difference was noted between the treated and untreated side of the face in terms of coverage, blotchiness, appearance, skin tone, or visual smoothness. Tolerability was excellent, with no erythema, edema, dryness, and peeling post-makeup application. For both the treated and untreated side, there was a slight lack of improvement in cosmetic appearance six hours post-makeup application. Clindamycin/benzoyl peroxide 3. 75% gel was shown to have excellent cosmetic compatibility with facial foundation.

  15. Impulse approximation in solid helium

    Glyde, H.R.

    1985-01-01

    The incoherent dynamic form factor S/sub i/(Q, ω) is evaluated in solid helium for comparison with the impulse approximation (IA). The purpose is to determine the Q values for which the IA is valid for systems such a helium where the atoms interact via a potential having a steeply repulsive but not infinite hard core. For 3 He, S/sub i/(Q, ω) is evaluated from first principles, beginning with the pair potential. The density of states g(ω) is evaluated using the self-consistent phonon theory and S/sub i/(Q,ω) is expressed in terms of g(ω). For solid 4 He resonable models of g(ω) using observed input parameters are used to evaluate S/sub i/(Q,ω). In both cases S/sub i/(Q, ω) is found to approach the impulse approximation S/sub IA/(Q, ω) closely for wave vector transfers Q> or approx. =20 A -1 . The difference between S/sub i/ and S/sub IA/, which is due to final state interactions of the scattering atom with the remainder of the atoms in the solid, is also predominantly antisymmetric in (ω-ω/sub R/), where ω/sub R/ is the recoil frequency. This suggests that the symmetrization procedure proposed by Sears to eliminate final state contributions should work well in solid helium

  16. Liquid helium plant in Dubna

    Agapov, N.N.; Baldin, A.M.; Kovalenko, A.D.

    1995-01-01

    The liquid-helium cooling capacity installed at the Laboratory of High Energies is about 5 kw at a 4.5 K temperature level. It is provided with four industrial helium liquefiers of 1.6 kw/4.5 K each. They have been made by the Russian enterprise NPO GELYMASH and upgraded by the specialists of the Laboratory. The first one was put into operation in 1980, the two others in 1991, and the last one is under commissioning. The development of the LHE cryoplant was concerned with the construction of the new superconducting accelerator Nuclotron aimed to accelerate nuclei and heavy ions up to energies of 6 GeV/u. The first test run at the Nuclotron was carried out in March 1993, and the total running time has been about 2000 hours up to now. Since 1992 the cryoplant has been intensively used by the users outside the Laboratory. More than a million liters of liquid helium was provided in 1993 for such users. The reliability of the cryoplant system was as high as 98 percent for 4500 hours of operation in 1993-1994. 7 refs., 4 figs., 1 tab

  17. Automation of the helium jet transport system for nuclear recoil products

    Bellido, Luis F.; Pedrosa, Paulo S.

    1996-09-01

    A computer code and an interface hardware to automate the acquisition data and the sample changer in a helium jet transport system of recoil nucleus was developed for an IBM or compatible personal microcomputer. The software works with a Spectrum-ACE/ADCAM ORTEC's multichannel analysers and the interface card uses the 03EFh port to command the sample changer. This system allows to measure, by gamma spectrometry, radionuclides with half-lives of order of seconds produced from nuclear reactions. (author)

  18. Parallel-plate third sound waveguides with fixed and variable plate spacings for the study of fifth sound in superfluid helium

    Jelatis, G.J.

    1983-01-01

    Third sound in superfluid helium four films has been investigated using two parallel-plate waveguides. These investigations led to the observation of fifth sound, a new mode of sound propagation. Both waveguides consisted of two parallel pieces of vitreous quartz. The sound speed was obtained by measuring the time-of-flight of pulsed third sound over a known distance. Investigations from 1.0-1.7K were possible with the use of superconducting bolometers, which measure the temperature component of the third sound wave. Observations were initially made with a waveguide having a plate separation fixed at five microns. Adiabatic third sound was measured in the geometry. Isothermal third sound was also observed, using the usual, single-substrate technique. Fifth sound speeds, calculated from the two-fluid theory of helium and the speeds of the two forms of third sound, agreed in size and temperature dependence with theoretical predictions. Nevertheless, only equivocal observations of fifth sound were made. As a result, the film-substrate interaction was examined, and estimates of the Kapitza conductance were made. Assuming the dominance of the effects of this conductance over those due to the ECEs led to a new expression for fifth sound. A reanalysis of the initial data was made, which contained no adjustable parameters. The observation of fifth sound was seen to be consistent with the existence of an anomalously low boundary conductance

  19. LOFA analyses for the water and helium cooled SEAFP reactors

    Sponton, L.; Sjoeberg, A.; Nordlinder, S.

    2001-01-01

    This study was performed in the frame of the European long-term fusion safety programme 1999 (SEAFP99). Loss of flow accidents (LOFA) have been studied for two cases, first for a helium cooled reactor with advanced dual-coolant (DUAL) blanket at 100% nominal power. The second case applies to a water-cooled reactor at 20% nominal power. Both transients were simulated with the code MELCOR 1.8.4. The results for the helium cooled reactor show that with a natural circulation flow of helium after the pump stops, the first wall temperature will stay below the temperature for excepted failure of the construction material. For the water cooled reactor, the results show that the pressurizer set point for its liquid volumetric inventory is reached before the plasma facing components attain a critical temperature. The pressurizer set point will induce a plasma shutdown

  20. On the theory of helium diffusion in stellar outer layers

    Ponce D, S.; Verga, A.D.

    1986-01-01

    We discuss the approximations usually made in the different approaches to diffusion in stellar outer layers. We analyze the hypotheses of binary diffusion and diffusion over a non altered background both analytically and numerically. Numerical calculations are applied to central stars of planetary nebulae in which a depletion of helium is observed. We find that in this case helium diffusion may be considered as a binary process but cannot be decoupled from the structure computation. We present an alternative method for studying diffusion and apply it to the central stars. We thus solve a stationary hydrodynamic model for a completely ionized H-He plasma, which takes into account consistently the behavior of all the species. We find equilibrium abundance distributions very different from those obtained according to the trace element approaches while helium and electron densities increase with depth in the atmosphere, protons tend to decrease. However, preliminary studies of the stability show that these are not the actual distributions. (author)

  1. The evolution of US helium-cooled blankets

    Wong, C.P.C.; Schultz, K.R.; Cheng, E.T.

    1991-01-01

    This paper reviews and compares four helium-cooled fusion reactor blanket designs. These designs represent generic configurations of using helium to cool fusion reactor blankets that were studied over the past 20 years in the United States of America (US). These configurations are the pressurized module design, the pressurized tube design, the solid particulate and gas mixture design, and the nested shell design. Among these four designs, the nested shell design, which was invented for the ARIES study, is the simplest in configuration and has the least number of critical issues. Both metallic and ceramic-composite structural materials can be used for this design. It is believed that the nested shell design can be the most suitable blanket configuration for helium-cooled fusion power and experimental reactors. (orig.)

  2. Self-trapping of helium in metals

    Wilson, W.D.; Bisson, C.L.; Baskes, M.I.

    1981-01-01

    Atomistic calculations are presented which demonstrate that helium atoms in a metal lattice are able to cluster with each other, producing vacancies and nearby self-interstitial defects. Even a small number of helium atoms is found to be sufficient to create these large distortions. As few as five interstitial helium can spontaneously produce a lattice vacancy and nearby self-interstitial. An eight-helium-atom cluster gives rise to two such defects, and 16 helium atoms to more than five self-interstitial vacancy pairs. It was noted that the self-interstitials prefer to agglomerate on the same ''side'' of the helium cluster rather than to spread themselves out uniformly. The binding energy of each additional helium atom to these clusters increases with helium concentration and the trap is apparently unsaturable. A rate theory using these atomistic binding energies has been used to calculate the kinetics of helium-bubble nucleation and growth. The results are consistent with measurements of the properties of helium resulting from tritium decay

  3. Interfaces and helium thin films : static properties and collective modes

    Pricaupenko, L.

    1994-12-01

    In the first part of this thesis are described the collective modes in thin films and at the free surface of helium 4. The second part deals with the spreading out of a model to describe the inhomogeneous helium 3. The influence of the quantum statistics on damping properties has also been given. In the third part is tackled some static properties of mixtures at interfaces. The instability growth rates in mixed films has been studied. At last is described the de-mixture study of two isotopes in a confined medium. (O.L.). 86 refs., 86 figs., 2 tabs

  4. Theoretical and experimental investigation of magnetic field related helium leak in helium vessel of a large superconducting magnet

    Bhattachryya, Pranab; Gupta, Anjan Dutta; Dhar, S.; Sarma, P. R.; Mukherjee, Paramita

    2017-06-01

    The helium vessel of the superconducting cyclotron (SCC) at the Variable Energy Cyclotron centre (VECC), Kolkata shows a gradual loss of insulation vacuum from 10-7 mbar to 10-4 mbar with increasing coil current in the magnet. The insulation vacuum restores back to its initial value with the withdrawal of current. The origin of such behavior has been thought to be related to the electromagnetic stress in the magnet. The electromagnetic stress distribution in the median plane of the helium vessel was studied to figure out the possible location of the helium leak. The stress field from the possible location was transferred to a simplified 2D model with different leak geometries to study the changes in conductance with coil current. The leak rate calculated from the changes in the leak geometry was compared with the leak rate calculated from the experimental insulation vacuum degradation behavior to estimate the initial leak shape and size.

  5. Helium turbomachinery operating experience from gas turbine power plants and test facilities

    McDonald, Colin F.

    2012-01-01

    The closed-cycle gas turbine, pioneered and deployed in Europe, is not well known in the USA. Since nuclear power plant studies currently being conducted in several countries involve the coupling of a high temperature gas-cooled nuclear reactor with a helium closed-cycle gas turbine power conversion system, the experience gained from operated helium turbomachinery is the focus of this paper. A study done as early as 1945 foresaw the use of a helium closed-cycle gas turbine coupled with a high temperature gas-cooled nuclear reactor, and some two decades later this was investigated but not implemented because of lack of technology readiness. However, the first practical use of helium as a gas turbine working fluid was recognized for cryogenic processes, and the first two small fossil-fired helium gas turbines to operate were in the USA for air liquefaction and nitrogen production facilities. In the 1970's a larger helium gas turbine plant and helium test facilities were built and operated in Germany to establish technology bases for a projected future high efficiency large nuclear gas turbine power plant concept. This review paper covers the experience gained, and the lessons learned from the operation of helium gas turbine plants and related test facilities, and puts these into perspective since over three decades have passed since they were deployed. An understanding of the many unexpected events encountered, and how the problems, some of them serious, were resolved is important to avoid them being replicated in future helium turbomachines. The valuable lessons learned in the past, in many cases the hard way, particularly from the operation in Germany of the Oberhausen II 50 MWe helium gas turbine plant, and the technical know-how gained from the formidable HHV helium turbine test facility, are viewed as being germane in the context of current helium turbomachine design work being done for future high efficiency nuclear gas turbine plant concepts. - Highlights:

  6. Single ionization of helium by fast proton impact: Searching for projectile coherence

    Gassert, H; Waitz, M; Kim, H-K; Bauer, T; Laucke, A; Müller, Ch; Voigtsberger, J; Weller, M; Rist, J; Pahl, K; Honig, M; Pitzer, M; Zeller, S; Jahnke, T; Schmidt, L Ph H; Schmidt-Böcking, H; Chuluunbaatar, O; Bulychev, A A; Zaytsev, S A; Kouzakov, K A

    2015-01-01

    The fully differential cross section (FDCS) for single ionization p + He → p + e + He + at proton energy of 1 MeV is studied both experimentally and theoretically. The 3D angular electron distribution is presented. The role of electron-electron correlations both in a trial helium ground-state wave function and in the final helium state is inspected. (paper)

  7. Irreversible adsorption of atmospheric helium on olivine: A lobster pot analogy

    Protin, Marie; Blard, Pierre-Henri; Marrocchi, Yves; Mathon, François

    2016-04-01

    This study reports new experimental results that demonstrate that large amounts of atmospheric helium may be adsorbed onto the surfaces of olivine grains. This behavior is surface-area-related in that this contamination preferentially affects grains that are smaller than 125 μm in size. One of the most striking results of our study is that in vacuo heating at 900 °C for 15 min is not sufficient to completely remove the atmospheric contamination. This suggests that the adsorption of helium may involve high-energy trapping of helium through irreversible anomalous adsorption. This trapping process of helium can thus be compared to a ;lobster pot; adsorption: atmospheric helium easily gets in, but hardly gets out. While this type of behavior has previously been reported for heavy noble gases (Ar, Kr, Xe), this is the first time that it has been observed for helium. Adsorption of helium has, until now, generally been considered to be negligible on silicate surfaces. Our findings have significant implications for helium and noble gas analysis of natural silicate samples, such as for cosmic-ray exposure dating or noble gas characterization of extraterrestrial material. Analytical procedures in future studies should be adapted in order to avoid this contamination. The results of this study also allow us to propose an alternative explanation for previously described matrix loss of cosmogenic 3He.

  8. Structural changes in a copper alloy due to helium implantation

    Moreno, D.; Eliezer, D.

    1996-01-01

    The most suitable nuclear fusion reaction for energy production occurs between the two heavy hydrogen isotopes, deuterium and tritium. Structural materials in fusion reactors will be exposed to helium implantation over a broad range of energies. The deformation and partial exfoliation of surface layers due to hydrogen isotopes and helium contribute to the total erosion of the first wall. For this reason, one of the most important criteria in the choice of materials for the first wall of fusion reactors is the material's damage resistance. Recent advances in developing nuclear fusion reactors reveal that efficient heat removal from plasma-facing components is very important. Copper and copper alloys are considered an attractive choice for transporting such a high heat flux without thermal damage as they have high thermal conductivity. In the present study the authors report on the structural changes in a copper alloy, due to the helium implantation on the very near surface area, observed by transmission electron microscopy

  9. ELECTRON ENERGY DECAY IN HELIUM AFTERGLOW PLASMAS AT CRYOGENIC TEMPERATURES

    Goldan, P. D.; Cahn, J. H.; Goldstein, L.

    1963-10-15

    Studies of decaying afterglow plasmas in helium were ined near 4 deg K by immersion in a liquid helium bath. By means of a Maser Radiometer System, the electron temperature was followed below 200 deg K. Guided microwave propagation and wave interaction techniques premit determination of election number density and collision frequencies for momentum transfer. Electron temperature decay rates of the order of 150 mu sec/p(mm Hg alpha 4.2 deg K) were found. Since thermal relaxation by elastic collisions should be some two orders of magnitude faster than this, the electrons appear to be in quasiequilibrium with a slowly decaying internal heating source. Correlation of the expected decay rates of singlet metastable helium atoms with the electron temperature decay gives good agreement with the present experiment. (auth)

  10. Helium diffusion in nickel at high temperatures

    Philipps, V.

    1980-09-01

    Helium has been implanted at certain temperatures between 800 and 1250 0 C into single and polycrystalline Ni-samples with implantation depths between 15 and 90 μm. Simultaneously the helium reemission from the sample is measured by a mass-spectrometer. It has been shown that the time dependence of the observed reemission rate is governed by volume diffusion of the helium. Measuring this time dependence as a function of temperature the helium diffusion constant has been determined. The He-diffusion is interpreted as a interstitial diffusion hindered by thermal vacancies. Depending on the implantation depth more or less of the implanted helium remains in the sample and forms large helium bubbles. (orig./GSCH)

  11. Test of a cryogenic helium pump

    Lue, J.W.; Miller, J.R.; Walstrom, P.L.; Herz, W.

    1981-01-01

    The design of a cryogenic helium pump for circulating liquid helium in a magnet and the design of a test loop for measuring the pump performance in terms of mass flow vs pump head at various pump speeds are described. A commercial cryogenic helium pump was tested successfully. Despite flaws in the demountable connections, the piston pump itself has performed satisfactorily. A helium pump of this type is suitable for the use of flowing supercritical helium through Internally Cooled Superconductor (ICS) magnets. It has pumped supercritical helium up to 7.5 atm with a pump head up to 2.8 atm. The maximum mass flow rate obtained was about 16 g/s. Performance of the pump was degraded at lower pumping speeds

  12. High temperature tensile properties of 316 stainless steel implanted with helium

    Hasegawa, Akira; Yamamoto, Norikazu; Shiraishi, Haruki

    1993-01-01

    Helium embrittlement is one of the problems in structural materials for fusion reactors. Recently, martensitic steels have been developed which have a good resistance to high-temperature helium embrittlement, but the mechanism has not yet been clarified. In this paper, tensile behaviors of helium implanted austenitic stainless steels, which are sensitive to the helium embrittlement, were studied and compared with those of martensitic steels under the same experimental conditions, and the effect of microstructure on helium embrittlement was discussed. Helium was implanted by 300 appm at 573-623 K to miniature tensile speciments of 316 austenitic steels using a cyclotron accelerator. Solution annealed (316SA) and 20% cold worked (316CW) specimens were used. Post-implantation tensile tests were carried out at 573, 873 and 973 K. Yield stress at 573 K increased with the helium implantation in 316SA and 316CW, but the yield stress changes of 316SA at 873 and 973 K were different from that of 316CW. Black-dots were observed in the as-implanted specimen and bubbles were observed in the speciments tensile-tested at 873 and 973 K. Intergranular fracture was observed at only 973 K in both of the 316SA and 316CW specimens. Therefore, cold work did not suppress the high-temperature helium embrittlement under this experimental condition. The difference in the influence of helium on type 316 steel and 9Cr martensitic steels were discussed. Test temperature change of reduction in are showed clearly that helium embrittlement did not occur in 9Cr martensitic steels but occurred in 316 austenitic steels. Fine microstructures of 9Cr martensitic steels should suppress helium embrittlement at high temperatures. (author)

  13. Final report on the Controlled Cold Helium Spill Test in the LHC tunnel at CERN

    Dufay-Chanat, L; Casas-Cubillos, J; Chorowski, M; Grabowski, M; Jedrusyna, A; Lindell, G; Nonis, M; Koettig, T; Vauthier, N; van Weelderen, R; Winkler, T

    2015-01-01

    The 27 km circumference LHC underground tunnel is a space in which the helium cooled LHC magnets are installed. The vacuum enclosures of the superconducting magnets are protected by over-pressure safety relief devices that open whenever cold helium escapes either from the magnet cold enclosure or from the helium supply headers, into this vacuum enclosure. A 3-m long no stay zone around these devices is defined based on scale model studies, protecting the personnel against cold burns or asphyxia caused by such a helium release event. Recently, several simulation studies have been carried out modelling the propagation of the helium/air mixture, resulting from the opening of such a safety device, along the tunnel. The released helium flows vary in the range between 1 kg/s and 0.1 kg/s. To validate these different simulation studies, real life mock-up tests have been performed inside the LHC tunnel, releasing helium flow rates of 1 kg/s, 0.3 kg/s and 0.1 kg/s. For each test, up to 1000 liters of liquid helium wer...

  14. A metastable helium trap for atomic collision physics

    Colla, M.; Gulley, R.; Uhlmann, L.; Hoogerland, M.D.; Baldwin, K.G.H.; Buckman, S.J.

    1999-01-01

    Full text: Metastable helium in the 2 3 S state is an important species for atom optics and atomic collision physics. Because of its large internal energy (20eV), long lifetime (∼8000s) and large collision cross section for a range of processes, metastable helium plays an important role in atmospheric physics, plasma discharges and gas laser physics. We have embarked on a program of studies on atom-atom and electron-atom collision processes involving cold metastable helium. We confine metastable helium atoms in a magneto-optic trap (MOT), which is loaded by a transversely collimated, slowed and 2-D focussed atomic beam. We employ diode laser tuned to the 1083 nm (2 3 S 1 - 2 3 P2 1 ) transition to generate laser cooling forces in both the loading beam and the trap. Approximately 10 million helium atoms are trapped at temperatures of ∼ 1mK. We use phase modulation spectroscopy to measure the trapped atomic density. The cold, trapped atoms can collide to produce either atomic He + or molecular He 2 + ions by Penning Ionisation (PI) or Associative Ionisation (AI). The rate of formation of these ions is dependant upon the detuning of the trapping laser from resonance. A further laser can be used to connect the 2 3 S 1 state to another higher lying excited state, and variation of the probe laser detuning used to measure interatomic collision potential. Electron-atom collision processes are studied using a monochromatic electron beam with a well defined spatial current distribution. The total trap loss due to electron collisions is measured as a function of electron energy. Results will be presented for these atomic collision physics measurements involving cold, trapped metastable helium atoms. Copyright (1999) Australian Optical Society

  15. Backscattered Helium Spectroscopy in the Helium Ion Microscope: Principles, Resolution and Applications

    van Gastel, Raoul; Hlawacek, G.; Dutta, S.; Poelsema, Bene

    2015-01-01

    We demonstrate the possibilities and limitations for microstructure characterization using backscattered particles from a sharply focused helium ion beam. The interaction of helium ions with matter enables the imaging, spectroscopic characterization, as well as the nanometer scale modification of

  16. Heat transfer in two-phase flow of helium

    Subbotin, V.I.; Deev, V.I.; Solodovnikov, V.V.; Arkhipov, V.V.

    1986-01-01

    The results of experimental study of heat transfer in two-phase helium flow are presented. The effect of operating parameters (pressure, mass velocity, heat flux and quality) on boiling heat transfer intensity was investigated. A significant influence of boiling process prehistory on heat transfer coefficients was demonstrated. On the basis of experimental data obtained three typical regimes of flow boiling heat transfer were found. Analogy of heat transfer in flow boiling and pool boiling of helium and noncryogenic liquids was established. Correlations were developed which are in close agreement with available heat transfer data

  17. Supercritical Helium Cooling of the LHC Beam Screens

    Hatchadourian, E; Tavian, L

    1998-01-01

    The cold mass of the LHC superconducting magnets, operating in pressurised superfluid helium at 1.9 K, must be shielded from the dynamic heat loads induced by the circulating particle beams, by means of beam screens maintained at higher temperature. The beam screens are cooled between 5 and 20 K by forced flow of weakly supercritical helium, a solution which avoids two-phase flow in the long, narr ow cooling channels, but still presents a potential risk of thermohydraulic instabilities. This problem has been studied by theoretical modelling and experiments performed on a full-scale dedicated te st loop.

  18. Conductivity change of defective graphene by helium ion beams

    Yuichi Naitou

    2017-04-01

    Full Text Available Applying a recently developed helium ion microscope, we demonstrated direct nano-patterning and Anderson localization of single-layer graphene (SLG on SiO2/Si substrates. In this study, we clarified the spatial-resolution-limitation factor of direct nano-patterning of SLG. Analysis of scanning capacitance microscopy measurements reveals that the conductivity of helium ion (H+-irradiated SLG nanostructures depends on their geometrical size, i.e., the smaller the H+-irradiated SLG region, the higher its conductivity becomes. This finding can be explained by the hopping carrier transport across strongly localized states of defective SLG.

  19. fMRI-compatible rehabilitation hand device

    Tzika Aria

    2006-10-01

    Full Text Available Abstract Background Functional magnetic resonance imaging (fMRI has been widely used in studying human brain functions and neurorehabilitation. In order to develop complex and well-controlled fMRI paradigms, interfaces that can precisely control and measure output force and kinematics of the movements in human subjects are needed. Optimized state-of-the-art fMRI methods, combined with magnetic resonance (MR compatible robotic devices for rehabilitation, can assist therapists to quantify, monitor, and improve physical rehabilitation. To achieve this goal, robotic or mechatronic devices with actuators and sensors need to be introduced into an MR environment. The common standard mechanical parts can not be used in MR environment and MR compatibility has been a tough hurdle for device developers. Methods This paper presents the design, fabrication and preliminary testing of a novel, one degree of freedom, MR compatible, computer controlled, variable resistance hand device that may be used in brain MR imaging during hand grip rehabilitation. We named the device MR_CHIROD (Magnetic Resonance Compatible Smart Hand Interfaced Rehabilitation Device. A novel feature of the device is the use of Electro-Rheological Fluids (ERFs to achieve tunable and controllable resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. The device consists of four major subsystems: a an ERF based resistive element; b a gearbox; c two handles and d two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. The smart hand device is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time. Results Laboratory tests of the device indicate that it was able to meet its design objective to resist up to approximately 50% of the maximum handgrip force. The detailed

  20. Helium leak testing methods in nuclear applications

    Ahmad, Anis

    2004-01-01

    Helium mass-spectrometer leak test is the most sensitive leak test method. It gives very reliable and sensitive test results. In last few years application of helium leak testing has gained more importance due to increased public awareness of safety and environment pollution caused by number of growing chemical and other such industries. Helium leak testing is carried out and specified in most of the critical area applications like nuclear, space, chemical and petrochemical industries

  1. Study on plasma pre-functionalized PVC film grafted with TiO2/PVP to improve blood compatible and antibacterial properties

    Suganya, Arjunan; Shanmugavelayutham, Gurusamy; Rodríguez, Carmen Serra

    2017-01-01

    Research into the design of new biopolymers/polymer functionalized with nanoparticles is of tremendous interest to the medical sector, particularly with regard to blood-contacting devices. In this present study, a steady blood compatible and active antibacterial coating was fabricated by the grafting of titanium dioxide (TiO 2 )/polyvinylpyyrolidone (PVP) onto a polyvinyl chloride (PVC) film surface via the direct-current glow discharge plasma method. To enhance the chemical interaction between TiO 2 /PVP and PVC, the surfaces of the PVC films were functionalized by different plasmas (air, argon, and oxygen) before coating. In this study, the plasma parameters were varied, such as treatment time of about 5–20 min for a constant power of 100 W, potential 300 V, and a constant gas pressure of 2 Pa for air, argon, and oxygen gas environment. Then, the different plasma treatments on the PVC films, TiO 2 /PVP were grafted using a simple dip-coating method. In addition, the TiO 2 /PVP-grafted PVC films were characterized by contact angle, attenuated total reflectance Fourier transform infrared spectroscopy, field-emission scanning electron microscope, and x-ray photo electron spectroscopy. Importantly, TiO 2 /PVP is grafted onto the PVC surface due to the plasma-based retained functionality and demonstrates adhesive efficiency, which was observed by XPS. The bio-stability of the TiO 2 /PVP-modified PVC film was evaluated by in vitro platelet activation analysis and protein adsorption analysis. Then, the antibacterial properties were evaluated by the agar diffusion method against Escherichia coli . The result reveals that the grafting of TiO 2 /PVP was slightly higher for the 15 min oxygen plasma-functionalized PVC, which significantly decreases the platelet adhesion and protein adsorption. Moreover, the antibacterial properties of the 15 min oxygen plasma-functionalized PVC with TiO 2 /PVP-grafted film is also greatly improved compared with an air- and argon

  2. Study of the compatibility and competitiveness of sterile males in the framework of the struggle by the sterile insect technique against the Ceratitis

    Azzabi, Jihene

    2007-01-01

    We evaluated under semi-natural field-cage conditions sexual compatibility and competitivity of laboratory strain (Genetic Sexing Strain GSS) ''Vienna 8''. The GSS strain is produced under mass (rearing conditions at the facility of production of sterile males at Sidi Thabat. Wild flies were obtained from infested Sommer oranges. Twenty-five wild males, 25 wild females and 25 GSS were released into cage and mating pairs collected. The determination of indices such as the Isolation Index (ISI), the Male Relative Index (MRPI), the Stalker Index (I) and the Relative Sterile Index (RSI) shows that there is no compatibility and competitiveness between the two strains with a tendency to behaviour of sexual isolation. Sterile male tests dissection irradiated at the dose of (0 Gy, 110 Gy, 120 Gy, 130 Gy and 145 Gy) and correspondent female spermatic show the important damage of the irradiation on the cells but decrease the quality of the sterile male (mating duration, sperm transfer.). (Author)

  3. An apparatus for studying electrical breakdown in liquid helium at 0.4 K and testing electrode materials for the neutron electric dipole moment experiment at the Spallation Neutron Source

    Ito, T. M., E-mail: ito@lanl.gov; Ramsey, J. C.; Clayton, S. M.; Currie, S. A.; Griffith, W. C.; Makela, M.; Tang, Z.; Wei, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Yao, W.; Cianciolo, V. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Beck, D. H.; Williamson, S. E. [Loomis Laboratory of Physics, University of Illinois, Urbana, Illinois 61801 (United States); Crawford, C.; Wagner, D. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States); Filippone, B. W.; Schmid, R. [W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Seidel, G. M. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)

    2016-04-15

    We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1–2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures at 0.4 K. We also measured the current between two electrodes. Our initial results, I < 1 pA at 45 kV, correspond to a lower bound on the effective volume resistivity of liquid helium of ρ{sub V} > 5 × 10{sup 18} Ω cm. This lower bound is 5 times larger than the bound previously measured. We report the design, construction, and operational experience of the apparatus, as well as initial results.

  4. Experimental study of cross-section ratios in the collisions of Cq+ and Oq+ (q = 1–4) on atomic helium in strong-interaction region

    Chen Xi-Meng; Jiang Li-Juan; Zhou Peng; Zhou Chun-Lin; Gao Zhi-Min; Qiu Xi-Yu; Cui Ying; Wang Xing-An; Lou Feng-Jun; Lü Xue-Yang; Jia Juan-Juan; Chen Lin; Shao Jian-Xiong; Lü Ying; Wang Fan

    2011-01-01

    We have measured the cross-section ratios of helium induced by C q+ and O q+ (q = 1–4) in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections (SI, SC, SLSI, and DLSI), total double-ionization cross-sections (DI, DC, TI, SLDI, and DLDI) and cross-sections of every process (SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI), which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly. (atomic and molecular physics)

  5. A statistical study of coronal densities from X-ray line ratios of helium-like ions - Ne IX and Mg XI

    Linford, G. A.; Lemen, J. R.; Strong, K. T.

    1988-01-01

    Since the repair of the Solar Maximum Mission (SMM) spacecraft, the Flat Crystal Spectrometer (FCS) has recorded many high temperature spectra of helium-like ions under a wide variety of coronal conditions including active regions, long duration events, compact events, and double flares. The plasma density and temperature are derived from the ratios R and G, where R = f/i, G = (f + i)/r, and r, f, and i denote the resonance, forbidden, and intercombination line fluxes. A new method for obtaining the density and temperature for events observed with the FCS aboard SMM is presented. The results for these events are presented and compared to earlier results, and the method is evaluated based on these comparisons.

  6. Helium Extraction from LNG End Flash

    Kim, Donghoi

    2014-01-01

    Helium is an invaluable element as it is widely used in industry such as cryo-genics and welding due to its unique properties. However, helium shortage is expected in near future because of increasing demand and the anxiety of sup-ply. Consequently, helium production has attracted the attention of industry. The main source of He is natural gas and extracting it from LNG end-flash is considered as the most promising way of producing crude helium. Thus, many process suppliers have proposed proc...

  7. New helium spectrum variable and a new helium-rich star

    Walborn, N.R.

    1974-01-01

    HD 184927, known previously as a helium-rich star, has been found to have a variable helium spectrum; the equivalent widths of five He I lines are larger by an average of 46 percent on a 1974 spectrogram than on one obtained with the same equipment in 1970. HD 186205 has been found to be a new, pronounced helium-rich star. (auth)

  8. Helium transfer line installation details.

    G. Perinic

    2007-01-01

    A particularity of the 32 m long four in one helium transfer line in between the cold box in USC55 and the cavern UX5 is the fact that the transfer line passes through a hole in the crane rail support beam. In order to ensure the alignment of the suspension rail in the interconnecting tunnel with the hole in the rail support as well as the connection points at both ends required precise measurements of the given geometries as well as the installation of a temporary target for the verification of the theoretical predictions.

  9. Skin blood flow from gas transport: helium xenon and laser Doppler compared

    Neufeld, G.R.; Galante, S.R.; Whang, J.M.; DeVries, D.; Baumgardner, J.E.; Graves, D.J.; Quinn, J.A.

    1988-01-01

    A study was designed to compare three independent measures of cutaneous blood flow in normal healthy volunteers: xenon-133 washout, helium flux, and laser velocimetry. All measurements were confined to the volar aspect of the forearm. In a large group of subjects we found that helium flux through intact skin changes nonlinearly with the controlled local skin temperature whereas helium flux through stripped skin, which is directly proportional to skin blood flow, changes linearly with cutaneous temperature over the range 33 degrees to 42 degrees. In a second group of six volunteers we compared helium flux through stripped skin to xenon-133 washout (intact skin) at a skin temperature of 33 degrees, and we found an essentially linear relationship between helium flux and xenon measured blood flow. In a third group of subjects we compared helium flux blood flow (stripped skin) to laser doppler velocimetric (LDV) measurements (intact skin) at adjacent skin sites and found a nonlinear increase in the LDV skin blood flow compared to that determined by helium over the same temperature range. A possible explanation for the nonlinear increases of helium flux through intact skin and of LDV output with increasing local skin temperature is that they reflect more than a change in blood flow. They may also reflect physical changes in the stratum corneum, which alters its diffusional resistance to gas flux and its optical characteristics

  10. Skin blood flow from gas transport: helium xenon and laser Doppler compared

    Neufeld, G.R.; Galante, S.R.; Whang, J.M.; DeVries, D.; Baumgardner, J.E.; Graves, D.J.; Quinn, J.A.

    1988-03-01

    A study was designed to compare three independent measures of cutaneous blood flow in normal healthy volunteers: xenon-133 washout, helium flux, and laser velocimetry. All measurements were confined to the volar aspect of the forearm. In a large group of subjects we found that helium flux through intact skin changes nonlinearly with the controlled local skin temperature whereas helium flux through stripped skin, which is directly proportional to skin blood flow, changes linearly with cutaneous temperature over the range 33 degrees to 42 degrees. In a second group of six volunteers we compared helium flux through stripped skin to xenon-133 washout (intact skin) at a skin temperature of 33 degrees, and we found an essentially linear relationship between helium flux and xenon measured blood flow. In a third group of subjects we compared helium flux blood flow (stripped skin) to laser doppler velocimetric (LDV) measurements (intact skin) at adjacent skin sites and found a nonlinear increase in the LDV skin blood flow compared to that determined by helium over the same temperature range. A possible explanation for the nonlinear increases of helium flux through intact skin and of LDV output with increasing local skin temperature is that they reflect more than a change in blood flow. They may also reflect physical changes in the stratum corneum, which alters its diffusional resistance to gas flux and its optical characteristics.

  11. Radiation damage in gallium-stabilized δ-plutonium with helium bubbles

    Wu, FengChao [CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China); Wang, Pei [Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Liu, XiaoYi [CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China); Wu, HengAn, E-mail: wuha@ustc.edu.cn [CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China)

    2017-02-15

    To understand the role of helium on self-irradiation effects in δ-plutonium, microstructure evolutions due to α-decay events near pre-existing helium bubbles in gallium-stabilized δ-plutonium are investigated using molecular dynamics simulations. Bubble promoting effect plays a dominating role in point defects production, resulting in increasing number of point defects. When lightweight helium atoms act as media, energy transfer discrepancy and altered spatial morphology of point defects induced by mass effect are revealed. The evolution of stacking faults surrounding the disordered core is studied and their binding effect on the propagation of point defects are presented. The cascade-induced bubble coalescence, resolution and re-nucleation driven by internal pressure are obtained in the investigation on helium behaviors. The intrinsic tendency in our simulated self-irradiation with helium bubbles is significant for understanding the underlying mechanism of aging in plutonium and its alloys.

  12. Quantum transition and decoherence of levitating polaron on helium film thickness under an electromagnetic field

    Kenfack, S. C.; Fotue, A. J.; Fobasso, M. F. C.; Djomou, J.-R. D.; Tiotsop, M.; Ngouana, K. S. L.; Fai, L. C.

    2017-12-01

    We have studied the transition probability and decoherence time of levitating polaron in helium film thickness. By using a variational method of Pekar type, the ground and the first excited states of polaron are calculated above the liquid-helium film placed on the polar substrate. It is shown that the polaron transits from the ground to the excited state in the presence of an external electromagnetic field in the plane. We have seen that, in the helium film, the effects of the magnetic and electric fields on the polaron are opposite. It is also shown that the energy, transition probability and decoherence time of the polaron depend sensitively on the helium film thickness. We found that decoherence time decreases as a function of increasing electron-phonon coupling strength and the helium film thickness. It is seen that the film thickness can be considered as a new confinement in our system and can be adjusted in order to reduce decoherence.

  13. Yonsei Evolutionary Population Synthesis (YEPS). II. Spectro-photometric Evolution of Helium-enhanced Stellar Populations

    Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook, E-mail: chulchung@yonsei.ac.kr, E-mail: sjyoon0691@yonsei.ac.kr [Center for Galaxy Evolution Research, Yonsei University, Seoul 03722 (Korea, Republic of)

    2017-06-20

    The discovery of multiple stellar populations in Milky Way globular clusters (GCs) has stimulated various follow-up studies on helium-enhanced stellar populations. Here we present the evolutionary population synthesis models for the spectro-photometric evolution of simple stellar populations (SSPs) with varying initial helium abundance ( Y {sub ini}). We show that Y {sub ini} brings about dramatic changes in spectro-photometric properties of SSPs. Like the normal-helium SSPs, the integrated spectro-photometric evolution of helium-enhanced SSPs is also dependent on metallicity and age for a given Y {sub ini}. We discuss the implications and prospects for the helium-enhanced populations in relation to the second-generation populations found in the Milky Way GCs. All of the models are available at http://web.yonsei.ac.kr/cosmic/data/YEPS.htm.

  14. Impact of helium implantation and ion-induced damage on reflectivity of molybdenum mirrors

    Garcia-Carrasco, A., E-mail: alvarogc@kth.se [Department of Fusion Plasma Physics, Royal Institute of Technology (KTH), Teknikringen 31, 100 44 Stockholm (Sweden); Petersson, P.; Hallén, A. [Department of Fusion Plasma Physics, Royal Institute of Technology (KTH), Teknikringen 31, 100 44 Stockholm (Sweden); Grzonka, J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, 02-507 Warsaw (Poland); Institute of Electronic Materials Technology, 133 Wolczynska Str., 01-919 Warsaw (Poland); Gilbert, M.R. [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Fortuna-Zalesna, E. [Faculty of Materials Science and Engineering, Warsaw University of Technology, 02-507 Warsaw (Poland); Rubel, M. [Department of Fusion Plasma Physics, Royal Institute of Technology (KTH), Teknikringen 31, 100 44 Stockholm (Sweden)

    2016-09-01

    Molybdenum mirrors were irradiated with Mo and He ions to simulate the effect of neutron irradiation on diagnostic first mirrors in next-generation fusion devices. Up to 30 dpa were produced under molybdenum irradiation leading to a slight decrease of reflectivity in the near infrared range. After 3 × 10{sup 17} cm{sup −2} of helium irradiation, reflectivity decreased by up to 20%. Combined irradiation by helium and molybdenum led to similar effects on reflectivity as irradiation with helium alone. Ion beam analysis showed that only 7% of the implanted helium was retained in the first 40 nm layer of the mirror. The structure of the near-surface layer after irradiation was studied with scanning transmission electron microscopy and the extent and size distribution of helium bubbles was documented. The consequences of ion-induced damage on the performance of diagnostic components are discussed.

  15. Yonsei Evolutionary Population Synthesis (YEPS). II. Spectro-photometric Evolution of Helium-enhanced Stellar Populations

    Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook

    2017-01-01

    The discovery of multiple stellar populations in Milky Way globular clusters (GCs) has stimulated various follow-up studies on helium-enhanced stellar populations. Here we present the evolutionary population synthesis models for the spectro-photometric evolution of simple stellar populations (SSPs) with varying initial helium abundance ( Y ini ). We show that Y ini brings about dramatic changes in spectro-photometric properties of SSPs. Like the normal-helium SSPs, the integrated spectro-photometric evolution of helium-enhanced SSPs is also dependent on metallicity and age for a given Y ini . We discuss the implications and prospects for the helium-enhanced populations in relation to the second-generation populations found in the Milky Way GCs. All of the models are available at http://web.yonsei.ac.kr/cosmic/data/YEPS.htm.

  16. Single ionization of helium by positron and electron impact

    Samanta, R; Purkait, M; Mandal, C R

    2012-01-01

    Four-body formalism of Boundary Corrected Continuum Intermediate State (BCCIS-4B) approximation is introduced to study the (e, 2e) reaction for Helium targets. The influence of the description of the ejected electron on triple differential cross sections is analyzed.

  17. Transportation system of recoil nucleus by helium jet

    Cabral, S.C.; Borges, A.M.; Lemos Junior, O.F.; Auler, L.T.; Silva, A.G. da

    1981-01-01

    The transportation system of recoil nucleus by helium jet, is studied. It is used a technique aiming to put in the detection area (region of low background) the recoils, produced by nuclear reactions between target and particle beams, those produced with the help of cyclotron CV-28. (E.G.) [pt

  18. Spectroscopy of antiproton helium atoms

    Hayano, Ryugo

    2005-01-01

    Antiproton helium atom is three-body system consisting of an antiproton, electrons and a helium nucleus (denoted by the chemical symbol, p-bar H + ). The authors produced abundant atoms of p-bar 4 He + , and p-bar 3 He + in a cooled He gas target chamber stopping the p-bar beam decelerated to approximately 100 keV in the Antiproton Decelerator at CERN. A precision laser spectroscopy on the atomic transitions in the p-bar 4 He + , and in p-bar 3 He + was performed. Principle of laser spectroscopy and various modifications of the system to eliminate factors affecting the accuracy of the experiment were described. Deduced mass ratio of antiproton and proton, (|m p -bar - m p |)/m p reached to the accuracy of 10 ppb (10 -8 ) as of 2002, as adopted in the recent article of the Particle Data Group by P.J. Mohr and B.N. Taylor. This value is the highest precise data for the CPT invariance in baryon. In future, antihydrogen atoms will be produced in the same facility, and will provide far accurate value of antiproton mass thus enabling a better confirmation of CPT theorem in baryon. (T. Tamura)

  19. Strange matter and Big Bang helium synthesis

    Madsen, J.; Riisager, K.

    1985-01-01

    Stable strange quark matter produced in the QCD phase transition in the early universe will trap neutrons and repel protons, thus reducing primordial helium production, Ysub(p). For reasonable values of Ysub(p), the radius of strange droplets must exceed 10 -6 cm if strange matter shall solve the dark-matter problem without spoiling Big Bang helium synthesis. (orig.)

  20. Post-giant evolution of helium stars

    Schoenberner, D.

    1977-01-01

    Extremely hydrogen deficient stars (helium stars and R Coronae Borealis variables) are considered to be remnants of double shell source stars (of the asymptotic giant branch). The evolution of stars with a condensed C/O-core and a helium envelope is followed numerically from the red giant stage to the white dwarf domain, crossing the regions of R CrB- and helium stars (so far analyzed). They have typically masses M/M(sun) = 0.7 and luminosities log L/L(sun) = 4.1. The time for crossing the helium star domain is some 10 3 years. The corresponding times in the R CrB-region amounts up to several 10 4 years. The lower limit of the death rate of helium stars is estimated to be 4 x 10 -14 pc -3 yr -1 . This value is only a factor of ten lower than the birth rate of all non-DA white dwarfs. It is therefore possible that the helium stars are the precursors of helium rich white dwarfs. As a consequence, a significant fraction of all stars which end their lives as white dwarfs should pass through the helium star phase. (orig.) [de

  1. Organ protection by the noble gas helium

    Smit, K.F.

    2017-01-01

    The aims of this thesis were to investigate whether helium induces preconditioning in humans, and to elucidate the mechanisms behind this possible protection. First, we collected data regarding organ protective effects of noble gases in general, and of helium in particular (chapters 1-3). In chapter

  2. Radioactive ions and atoms in superfluid helium

    Dendooven, P.G.; Purushothaman, S.; Gloos, K.; Aysto, J.; Takahashi, N.; Huang, W.; Harissopulos, S; Demetriou, P; Julin, R

    2006-01-01

    We are investigating the use of superfluid helium as a medium to handle and manipulate radioactive ions and atoms. Preliminary results on the extraction of positive ions from superfluid helium at temperatures close to 1 K are described. Increasing the electric field up to 1.2 kV/cm did not improve

  3. Deformation compatibility control for engineering structures methods and applications

    Zhu, Hanhua; Chen, Mengchong; Deng, Jianliang

    2017-01-01

    This book presents essential methods of deformation compatibility control, and explicitly addresses the implied conditions on the methods’ deformation compatibility. Consequently, these conditions can be considered in engineering structure design, while the conditions on stable equilibrium can be taken into account in the design method. Thus, the designed deformation and the actual deformation of the respective structure are approximately identical, guaranteeing both the flexibility of the construction material in force transmission and the equilibrium of force in the structure. Though equilibrium theory in engineering structures has been extensively studied, there has been comparatively little research on compatibility. In the limited researches available, the topics are primarily the theories and assumptions on the deformation compatibility, while few systematic works focus on the mechanical theoretical principles and methods of deformation compatibility control. As such, the flexibility of the constructi...

  4. 3D numerical simulation of fluid–solid coupled heat transfer with variable property in a LBE-helium heat exchanger

    Chen, Fei, E-mail: chenfei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); North China University of Water Resources and Electric Power, 36 Beihuan Road, Zhengzhou, Henan 450011 (China); Cai, Jun, E-mail: caijun@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Li, Xunfeng, E-mail: lixunfeng@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Huai, Xiulan, E-mail: hxl@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Wang, Yongwei, E-mail: wangyongwei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China)

    2014-07-01

    Highlights: • Heat transfer in heat exchanger can be improved by increasing helium's flow rate. • The outlet temperature of helium decreases with increasing helium's flow rate. • Balance is necessary between good heat transfer and high helium outlet temperature. - Abstract: LBE-helium experimental loop of ADS (LELA) and LBE-helium heat exchanger have been designed and constructed with the supporting of the “ADS Transmutation System” project of Chinese Academy of Sciences. In order to investigate the flow and heat transfer characteristics between LBE and helium, 3D numerical simulation of fluid–solid coupled heat transfer with variable property in the LBE-helium heat exchanger is conducted in the present study. The effects of mass-flow-rates of helium and LBE in the shell-side and tube-side on the heat transfer performance are addressed. It is found that the heat transfer performance can be significantly improved by increasing helium mass-flow-rate in the shell-side. In order to easily and quickly obtain the outlet temperatures of helium and LBE, a concept of modified effectiveness is introduced and correlated as the function of tube-side to shell-side heat capacity rate ratio. The results show that the outlet temperature of helium decreases with increasing helium mass-flow-rate. Therefore, considering the utilization of high-temperature helium in the future, for example power generation, there should be a tradeoff between good heat transfer performance and high outlet helium temperature when confirming helium mass-flow-rate.

  5. Modeling Secondary Neutral Helium in the Heliosphere

    Müller, Hans-Reinhard; Möbius, Eberhard; Wood, Brian E.

    2016-01-01

    An accurate, analytic heliospheric neutral test-particle code for helium atoms from the interstellar medium (ISM) is coupled to global heliospheric models dominated by hydrogen and protons from the solar wind and the ISM. This coupling enables the forward-calculation of secondary helium neutrals from first principles. Secondaries are produced predominantly in the outer heliosheath, upwind of the heliopause, by charge exchange of helium ions with neutral atoms. The forward model integrates the secondary production terms along neutral trajectories and calculates the combined neutral helium phase space density in the innermost heliosphere where it can be related to in-situ observations. The phase space density of the secondary component is lower than that of primary neutral helium, but its presence can change the analysis of primaries and the ISM, and can yield valuable insight into the characteristics of the plasma in the outer heliosheath. (paper)

  6. THE HELIUM CONTENT OF GLOBULAR CLUSTERS: NGC 6121 (M4)

    Villanova, S.; Geisler, D.; Piotto, G.; Gratton, R. G.

    2012-01-01

    In the context of the multiple stellar population scenario in globular clusters, helium (He) has been proposed as a key element to interpret the observed multiple main sequences, subgiant branches, and red giant branches, as well as the complex horizontal branch (HB) morphology. In particular, second-generation stars belonging to the bluer part of the HB are thought to be more He-rich (ΔY = 0.03 or more) but also more Na-rich/O-poor than those located in the redder part that should have Y equal to the cosmological value. Up to now this hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed an He content of Y = 0.25 ± 0.01, fully compatible with the primordial He content of the universe, and were all Na-poor/O-rich. Here we study hot blue horizontal branch (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. Our goal is to complete the partial results obtained for NGC 6752, focusing our attention on targets located on the bluer part of the HB of M4. We observed six BHB stars using the VLT2/UVES spectroscopic facility. Spectra of signal-to-noise ratio ∼ 150 were obtained and the very weak He line at 5875 Å measured for all our targets. We compared this feature with synthetic spectra to obtain He abundances. In addition O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous He content with a mean value of Y = 0.29 ± 0.01(random) ± 0.01(systematic), which is enhanced by ΔY ∼ 0.04 with respect to the most recent measurements of the primordial He content of the universe (Y ∼ 0.24/0.25). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by Δ(Y) = 0.02/0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H] = –1.06 ± 0.02 (internal error), in agreement with other studies

  7. The Helium Content of Globular Clusters: NGC 6121 (M4)

    Villanova, S.; Geisler, D.; Piotto, G.; Gratton, R. G.

    2012-03-01

    In the context of the multiple stellar population scenario in globular clusters, helium (He) has been proposed as a key element to interpret the observed multiple main sequences, subgiant branches, and red giant branches, as well as the complex horizontal branch (HB) morphology. In particular, second-generation stars belonging to the bluer part of the HB are thought to be more He-rich (ΔY = 0.03 or more) but also more Na-rich/O-poor than those located in the redder part that should have Y equal to the cosmological value. Up to now this hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed an He content of Y = 0.25 ± 0.01, fully compatible with the primordial He content of the universe, and were all Na-poor/O-rich. Here we study hot blue horizontal branch (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. Our goal is to complete the partial results obtained for NGC 6752, focusing our attention on targets located on the bluer part of the HB of M4. We observed six BHB stars using the VLT2/UVES spectroscopic facility. Spectra of signal-to-noise ratio ~ 150 were obtained and the very weak He line at 5875 Å measured for all our targets. We compared this feature with synthetic spectra to obtain He abundances. In addition O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous He content with a mean value of Y = 0.29 ± 0.01(random) ± 0.01(systematic), which is enhanced by ΔY ~ 0.04 with respect to the most recent measurements of the primordial He content of the universe (Y ~ 0.24/0.25). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by Δ(Y) = 0.02/0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H] = -1.06 ± 0.02 (internal error), in agreement with other studies available in

  8. Use of Helium-3 and Tritium tracers in oceanography

    Andrie, Chantal

    1987-01-01

    As tritium considered as a transient tracer has become one of the most promising tool for the study of oceanic circulation and of the ocean capacity to absorb anthropogenic carbon, and as the simultaneous use of its radioactive descendant, Helium-3, brings an additional information (together, these tracers build up a clock in the study of water masses), and as all helium-3 and tritium measurements are made by mass spectroscopy, this research thesis addresses the analytical process, the detection limit, and the method reproducibility associated with this use of both tracers. The author reports and discusses helium-3 data obtained during a measurement campaign which allowed the localisation of an active source and the evidence of an intermediate back current, and tritium data obtained during another measurement campaign which allowed the description of the high time variability of convection processes, and an assessment of water renewal delays and of some deep water circulations. He also reports and discusses the simultaneous use of helium-3 data and tritium data to localize areas where convection processes occur. A theoretical approach to this simultaneous use is proposed which uses a mixing model which distinguishes the venting transit time. Measurement campaigns were performed in Red Sea, western Mediterranean Sea, and north-eastern Atlantic Ocean [fr

  9. Determination of helium in beryl minerals

    Souza Barcellos, E. de.

    1985-08-01

    In order to obtain the diffusion coefficients of helium in beryl and phenacite samples at various temperatures, helium leak rates were measured in these minerals at these temperatures. Mass spectrometry (MS) was used to obtain helium leak rates and the gas flow was plotted against time. The gas quantity determined by MS was first obtained at various temperatures until no helium leak rate was detected. After that, these samples were irradiated with fast neutrons to produce helium which was measured again. This procedure was used to estimate the experimental error. The quantity of helium produced by interaction of gamma radiation with beryl minerals was theoretically calculated from the amount of thorium-232 at the neighbourhood of the samples. The quantity of helium produced in the minerals due to uranium and thorium decay was calculated using the amount of these heavy elements, and the results were compared with the amounts determined by MS. The amount of potassium-40 was determined in order to derive the quantity of argonium-40, since some workers found argonium in excess in these minerals. The quantity of helium in the beryl samples (s) was determined in the center and in the surface of the samples in order to obtain informations about the effectiveness of the Be(α, η) He reaction. Beryl and phenacite minerals were choosen in this research since they are opposite each other with respect to the helium contents. Both have beryllium in their compositon but beryl hold a large amount of helium while phenacite, in spite of having about three times more beryllium than beryl, do not hold the gas. (author) [pt

  10. Development of evaluation method of long-term confinement performance for canister. Part 1. Fundamental study of analyses method for helium leak detection

    Takeda, Hirofumi; Toriu, Daisuke; Ushijima, Satoru

    2014-01-01

    The storage management of spent nuclear fuel for ageing degradation is becoming a global issue, so we researched the present status and measures of the management in each country. In particular, for the concrete cask storage, a leak detecting method that detects the leak from the change in canister surface temperature has been proposed. We performed thermal hydraulics analysis to clarify the phenomenon and to work toward practical use of the detecting method. For analyzing the leak phenomenon with high accuracy, it is necessary to stably solve the low-Mach number flow problem considering compressibility of gas. Therefore, we originally modified the conventional compressible flow solution method and proposed a new method which is applicable to thermo-hydraulics phenomenon and satisfies the mass conservation law with high accuracy. For the cavity natural convection analysis, the mass conservation in a calculating area was satisfied with high accuracy. As for the analysis of leak from the cavity, a helium leak phenomenon could be calculated stably by using the proposed method. The pressure in the cavity and the change of the mass could be also analyzed validly. As for the temperature distribution in the cavity, it was confirmed that the temperature changes before and after the leak. (author)

  11. An apparatus for studying electrical breakdown in liquid helium at 0.4 K and testing electrode materials for the neutron electric dipole moment experiment at the Spallation Neutron Source.

    Ito, T M; Ramsey, J C; Yao, W; Beck, D H; Cianciolo, V; Clayton, S M; Crawford, C; Currie, S A; Filippone, B W; Griffith, W C; Makela, M; Schmid, R; Seidel, G M; Tang, Z; Wagner, D; Wei, W; Williamson, S E

    2016-04-01

    We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1-2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures at 0.4 K. We also measured the current between two electrodes. Our initial results, I 5 × 10(18) Ω cm. This lower bound is 5 times larger than the bound previously measured. We report the design, construction, and operational experience of the apparatus, as well as initial results.

  12. PULSATIONS IN HYDROGEN BURNING LOW-MASS HELIUM WHITE DWARFS

    Steinfadt, Justin D. R.; Bildsten, Lars; Arras, Phil

    2010-01-01

    Helium core white dwarfs (WDs) with mass M ∼ sun undergo several Gyr of stable hydrogen burning as they evolve. We show that in a certain range of WD and hydrogen envelope masses, these WDs may exhibit g-mode pulsations similar to their passively cooling, more massive carbon/oxygen core counterparts, the ZZ Cetis. Our models with stably burning hydrogen envelopes on helium cores yield g-mode periods and period spacings longer than the canonical ZZ Cetis by nearly a factor of 2. We show that core composition and structure can be probed using seismology since the g-mode eigenfunctions predominantly reside in the helium core. Though we have not carried out a fully nonadiabatic stability analysis, the scaling of the thermal time in the convective zone with surface gravity highlights several low-mass helium WDs that should be observed in search of pulsations: NLTT 11748, SDSS J0822+2753, and the companion to PSR J1012+5307. Seismological studies of these He core WDs may prove especially fruitful, as their luminosity is related (via stable hydrogen burning) to the hydrogen envelope mass, which eliminates one model parameter.

  13. Helium bubbles aggravated defects production in self-irradiated copper

    Wu, FengChao; Zhu, YinBo; Wu, Qiang; Li, XinZhu; Wang, Pei; Wu, HengAn

    2017-12-01

    Under the environment of high radiation, materials used in fission and fusion reactors will internally accumulate numerous lattice defects and bubbles. With extensive studies focused on bubble resolution under irradiation, the mutually effects between helium bubbles and displacement cascades in irradiated materials remain unaddressed. Therefore, the defects production and microstructure evolution under self-irradiation events in vicinity of helium bubbles are investigated by preforming large scale molecular dynamics simulations in single-crystal copper. When subjected to displacement cascades, distinguished bubble resolution categories dependent on bubble size are observed. With the existence of bubbles, radiation damage is aggravated with the increasing bubble size, represented as the promotion of point defects and dislocations. The atomic mechanisms of heterogeneous dislocation structures are attributed to different helium-vacancy cluster modes, transforming from the resolved gas trapped with vacancies to the biased absorption of vacancies by the over-pressured bubble. In both cases, helium impedes the recombination of point defects, leading to the accelerated formation of interstitial loops. The results and insight obtained here might contribute to understand the underlying mechanism of transmutant solute on the long-term evolution of irradiated materials.

  14. Impact of neutron irradiation on thermal helium desorption from iron

    Hu, Xunxiang, E-mail: hux1@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Field, Kevin G. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Taller, Stephen [University of Michigan, Ann Arbor, MI 48109 (United States); Katoh, Yutai [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Wirth, Brian D. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); University of Tennessee, Knoxville, TN 37996 (United States)

    2017-06-15

    The synergistic effect of neutron irradiation and transmutant helium production is an important concern for the application of iron-based alloys as structural materials in fission and fusion reactors. In this study, we investigated the impact of neutron irradiation on thermal helium desorption behavior in high purity iron. Single crystalline and polycrystalline iron samples were neutron irradiated in HFIR to 5 dpa at 300 °C and in BOR-60 to 16.6 dpa at 386 °C, respectively. Following neutron irradiation, 10 keV He ion implantation was performed at room temperature on both samples to a fluence of 7 × 10{sup 18} He/m{sup 2}. Thermal desorption spectrometry (TDS) was conducted to assess the helium diffusion and clustering kinetics by analyzing the desorption spectra. The comparison of He desorption spectra between unirradiated and neutron irradiated samples showed that the major He desorption peaks shift to higher temperatures for the neutron-irradiated iron samples, implying that strong trapping sites for He were produced during neutron irradiation, which appeared to be nm-sized cavities through TEM examination. The underlying mechanisms controlling the helium trapping and desorption behavior were deduced by assessing changes in the microstructure, as characterized by TEM, of the neutron irradiated samples before and after TDS measurements.

  15. Commercial helium reserves, continental rifting and volcanism

    Ballentine, C. J.; Barry, P. H.; Hillegonds, D.; Fontijn, K.; Bluett, J.; Abraham-James, T.; Danabalan, D.; Gluyas, J.; Brennwald, M. S.; Pluess, B.; Seneshens, D.; Sherwood Lollar, B.

    2017-12-01

    Helium has many industrial applications, but notably provides the unique cooling medium for superconducting magnets in medical MRI scanners and high energy beam lines. In 2013 the global supply chainfailed to meet demand causing significant concern - the `Liquid Helium Crisis' [1]. The 2017 closure of Quatar borders, a major helium supplier, is likely to further disrupt helium supply, and accentuates the urgent need to diversify supply. Helium is found in very few natural gas reservoirs that have focused 4He produced by the dispersed decay (a-particle) of U and Th in the crust. We show here, using the example of the Rukwa section of the Tanzanian East African Rift, how continental rifting and local volcanism provides the combination of processes required to generate helium reserves. The ancient continental crust provides the source of 4He. Rifting and associated magmatism provides the tectonic and thermal mechanism to mobilise deep fluid circulation, focusing flow to the near surface along major basement faults. Helium-rich springs in the Tanzanian Great Rift Valley were first identified in the 1950's[2]. The isotopic compositions and major element chemistry of the gases from springs and seeps are consistent with their release from the crystalline basement during rifting [3]. Within the Rukwa Rift Valley, helium seeps occur in the vicinity of trapping structures that have the potential to store significant reserves of helium [3]. Soil gas surveys over 6 prospective trapping structures (1m depth, n=1486) show helium anomalies in 5 out of the 6 at levels similar to those observed over a known helium-rich gas reservoir at 1200m depth (7% He - Harley Dome, Utah). Detailed macroseep gas compositions collected over two days (n=17) at one site allows us to distinguish shallow gas contributions and shows the deep gas to contain between 8-10% helium, significantly increasing resource estimates based on uncorrected values (1.8-4.2%)[2,3]. The remainder of the deep gas is

  16. Multicoincidence measurements of double photoionization in helium

    Huetz, A.; Andric, L.; Selles, P.; Mazeau, J.; Lablanquie, P.

    1994-01-01

    A new toroidal analyser has been used to study the double photoionization of helium, for energies down to 4 eV above threshold. The two electrons are detected with equal energies, and coincidences between them for various angles of emission can be obtained simultaneously. The plane of detection contains the photon beam, in contrast with recent experiments performed in the plane perpendicular to the photon beam. The angular correlation function is extracted directly from the present measurements, which are shown to be insensitive to the Stokes parameters of the photon beam. The width of that function is not observed to vary significantly from 4 eV to 17.6 eV above threshold. (author)

  17. Pulsation of high luminosity helium stars

    King, D.S.; Wheeler, J.C.; Cox, J.P.; Cox, A.N.; Hodson, S.W.

    1979-01-01

    Preliminary calculations are made on a systematic restudy of the linear and nonlinear pulsations of helium stars allowing for more recent and higher estimates of the effective temperature and for the high carbon abundance. Linear and nonlinear models are used. Results show qualitative agreement with earlier ones, models with sufficiently large L/M have a very hot blue edge for their instability strip, very large L/M values lead to dynamically unstable models which would appear to eject mass and therefore may not be realistic models for the pulsating RCrB stars, for the sequence studied a reasonable mass could be greater than or equal to 1.5 Msub solar. 12 references

  18. Observation of the antimatter helium-4 nucleus.

    2011-05-19

    High-energy nuclear collisions create an energy density similar to that of the Universe microseconds after the Big Bang; in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high-energy accelerator of heavy nuclei provides an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus (4He), also known as the anti-α (α), consists of two antiprotons and two antineutrons (baryon number B = -4). It has not been observed previously, although the α-particle was identified a century ago by Rutherford and is present in cosmic radiation at the ten per cent level. Antimatter nuclei with B antimatter nuclei and a benchmark for possible future observations of 4He in cosmic radiation.

  19. Helium hammer in superfluid transfer

    Tward, E.; Mason, P. V.

    1984-01-01

    Large transient pressure pulses, referred to as a helium hammer, which occurred in the transfer line of the main cryogenic tank during the development tests of the Infrared Astronomical Satellite, launched on January 25, 1983, are analyzed, and the measures taken to prevent a failure described. The modifications include an installation of a 2.3-liter surge tank upstream, and a back-up relief valve downstream, of a burst disk. The surge tank is designed to attenuate a 0.33-MPa pressure pulse at the inlet down to 0.092 MPa at the outlet. A mechanism of the pulse generation is suggested, which involves flashing and rapid recondensation of the small amount of liquid entering the warm section of a transition to room temperature.

  20. Materials compatibility information data bank

    Mead, K.E.

    1977-01-01

    A major concern in the design of weapons systems is the compatibility of the materials used with each other and with the enclosed environment. Usually these systems require long term storage with a high reliability for proper function at the end of this storage period. Materials selection is then based on both past experience and laboratory accelerated aging experiments to assure this long term reliability. To assist in the task of materials selection a computerized materials compatibility data bank is being established. This data bank will provide a source of annotated information and references to personnel and documents for both the designer and materials engineer to draw on for guidance in materials selection. The data bank storage and information retrieval philosophy will be discussed and procedures for information gathering outlined. Examples of data entries and search routines will be presented to demonstrate the usefulness and versatility of the proposed system