Geoffrey Pelling, Richard Mackay, P. Wright, A.J. Dickers, Lord Carver, Patrick Herbert, Morris Assa, Fergus Dodd, Richard Winfield, George Gellert, William Woodward, Caryn Margolies,
... chemistry Too much in the sun Anti-microscopes Positron beams Book Call A. & C. Black International Trade ...
1989 - Gale Group | The Economist
Positron is an excellent probe of lattice defects in solids. A thermallized positron delocalized in lattice can be trapped at open ... defects, e.g. vacancies, dislocations, grain boundaries etc. Positron annihilation spectroscopy is a non-destructive technique which ... lattice defects in solids on the atomic scale. Positron lifetime and Doppler broadening of annihilation photo-peak are the most common observables related to positron annihilation process. Positron lifetime spectroscopy enables to identify ...
Tópico(s): Atomic and Molecular Physics
1953 - Elsevier BV | Progress in Metal Physics
John Grant Crossword Editor, David Wade, Frances Gibb, Legal Affairs Correspondent, Andrew Billen, Clifford Longley, Andrew McEwen, Christopher Warman, Property Correspondent, Stephen Leather, Andrew Longmore, Peter Marsden, Director, Gordon Allan, Ronald Faux, David Rhys Jones, Cliff Feltham, Sheridan Morley, Clifford Webb, Robin Oakley, Philip Howard, Hilary Finch, David Smith, Ian Murray, Michael Binyon, Clive Davis, David Sapsted and Andrew Morgan, David Ennals, Chairman, Robert Kirkland, Sarah Jane Checkland, Art Market Correspondent, Majorie Wallace, Stuart Jones Football Correspondent, Colin Narbrough, Gerald Davies, Joe Joseph, Bernard Levin, Brian James, Henry Gee, Bryan Stiles, Jim Railton, Brightman, Sarah Thompson, Education Reporter, Malcolm Roberts, Brian Green, David Kirk, John Ballantine, Jonathan Braude, Konstanz, Peter Waymark, David Watts and Graham Searjeant, John Patten, Michael Clark, Martin Fletcher, Political Reporter, Michael Hamlyn, H. F., Rex Bellamy Tennis Correspondent, Sydney Friskin, Nicholas Harling, Dennis Signy, Michael Dann, John Higgins, Christopher Goulding, Robin Oakley, Political Editor, Kerry Gill, Peter Sawyer, William Holmes, Peter Davalle, Alan Lee, Cricket Correspondent, John Clare and Robin Oakley, Peter Bryan, Alexandra Jackson, Roland Rudd, Lawrence Norcross, Charles Knevitt, Pittsburgh, Richard Evans, Martin Fletcher and David Walker, Derek Harris Industrial editor, Pat Butcher, Joyce Whitehead, Maxwell Newton, Peter Dixon, Bryan Appleyard, Brian Beel, Derek Harris, Industrial Editor, Keith MacKlin, David Hands Rugby Correspondent, Christopher Thomas, Pat Butcher, Athletics Correspondent, Christopher Walker, Mandarin, Iain MacLeod, Clive White, Julian Brazier, Liz Smith, Alan Franks, Sarah Jane Checkland Art Market Correspondent, Michael Hornsby, Michael Seely, Bruce Martin, Daniel Ward, Alan Lee Cricket Correspondent, David Walker, David Sinclair, Graham Searjeant, Andrew Buckoke, Robert Fisk, Richard Morrison, Vince Wright, Francis Ritchie, Pearce Wright, Science Editor, Harvey Elliott Air Correspondent, Penny Perrick, Dominique Searle, Andrew McEwen, and Richard Wigg, Colin Campbell, David Young Energy Correspondent, Philip Jacobson, David Hands, Rugby Correspondent, Colin McQuillan, Clement Freud, Rodney Lord Economics Editor,
... Sundown Yacht Charters Ltd Dolphin Yacht Engines Ltd Positron Navigation Multhull Centre Multiple Display Advertising Items B. ...
1988 - Gale Group | TDA
The annihilation of positrons may occur either (1) when the positron is in motion, or (2) when it has already been stopped. In ... between any free or bound electron and the positron, whereas only very tightly bound electrons can annihilate a positron with emission of one light quantum only. The annihilation of positrons which are already stopped takes place practically only ... two quanta. The one-quantum annihilation of slow positrons is extremely unlikely since the positron cannot get to the tightly bound electrons owing ...
Tópico(s): Atomic and Molecular Physics
1935 - Royal Society | Proceedings of the Royal Society of London A Mathematical and Physical Sciences
The probability of the simultaneous of a positron and an electron, with the emission of two quanta of radiation, has been calculated by Dirac and several other authors. From considerations of ... and momentum it follows that an electron and positron can only annihilate one another with the emission ... bound in an atom could, therefore, annihilate a positron, represented by a hole on the Dirac theory, ... the condition where the kinetic energy of the positron is of the order of magnitude of the ... the fact that for these small energies, the positron does not get near the nucleus. In view ...
Tópico(s): Atomic and Molecular Physics
1934 - Royal Society | Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character
G. Frick, A. Gallmann, D. E. Alburger, D. H. Wilkinson, J.P. Coffin,
... image spectrometer has been used to measure the positron spectra of the isotopes ${\mathrm{O}}^{14}$, ${\mathrm{ ... mathrm{O}}^{14}$ reaction and it emits a positron group of ${E}_{max}=(4.085\ifmmode\pm\ ... means of scintillation detectors we find a second positron branch feeding the 1.04-MeV level of ${\ ... while the second branch is masked by other positron activities. We find ${\mathrm{T}}_{\mathrm{\textonehalf{}}}$=2. ... 0.010) MeV gamma rays in coincidence with positrons. Branching ratios of ${\mathrm{Si}}^{26}$, measured with ...
Tópico(s): X-ray Spectroscopy and Fluorescence Analysis
1963 - American Institute of Physics | Physical Review
... concerning the intensity and energy distribution of the positrons emitted by aRa(B + C) source are described. ... the results of Chadwick, Blackett and Occhialini (24 positrons against 2000 negative electrons). From the strength of ... theory of Jaeger and Hulme, the number of positrons excited by the internal pair production byγ-rays ... about 90 times as large. If the observed positrons are ascribed to the internal pair production by ... Arley and Moller. The energy distribution of the positrons shows that by far the greater part of ...
Tópico(s): Electron and X-Ray Spectroscopy Techniques
1939 - Elsevier BV | Physica
Springer Link
P. E. Mijnarends, Lars Hambro,
... developed to study surfaces using bright low-energy positron beams. These novel analysis tools exploit the unique properties of positron interaction with surfaces, which comprise the absence of exchange interaction, repulsive crystal potential and positron trapping in delocalized surface states at low energies. By applying reflection high-energy positron diffraction (RHEPD) one can benefit from the phenomenon ... surfaces with outstanding accuracy. The main advantages of positron annihilation induced Auger-electron spectroscopy (PAES) are the ...
Tópico(s): Graphene research and applications
1964 - Elsevier BV | Physics Letters
R.E. Sund, R.B. Walton, N. Norris, Malcolm H. MacGregor,
The characteristics of a positron beam produced with a converter system located after the first section of a three-section, L-band accelerator have been investigated. The number of positrons emerging from the accelerator per electron incident on ... 8 to 15 MeV. Other properties of the positron beam which were studied include the energy spectrum, ... influence of the magnetic focussing fields on the positron yields was investigated, and the energy of the positrons leaving the converter which were preferentially accelerated was ...
Tópico(s): Gyrotron and Vacuum Electronics Research
1964 - Elsevier BV | Nuclear Instruments and Methods
Springer Link
D. Stroud, Hannelore Ehrenreich,
The single-particle positron wave function in a solid may be calculated by a new technique which is entirely free of any theoretical ... systematic treatment of many-body effects in electron-positron annihilation processes. The positron wave function, which has the full crystal symmetry, ... practically isotropic, despite the angular variation of the positron wave function. The substantial anisotropy in Si is reproduced within experimental error. Use of a constant positron wave function somewhat reduces the agreement. The calculated ...
Tópico(s): X-ray Diffraction in Crystallography
1968 - American Institute of Physics | Physical Review
National Library of Medicine (NCBI)
C.L. Snead, A.N. Goland, F.W. Wiffen,
... was injected with 0.6 appm of helium. Positron lifetime measurements were performed following isochronal annealing between ... This substitutional helium is a trapping site for positrons. By monitoring the concentration and size of this trapping site through the measurement of the positron lifetimes it is concluded that migration of the ... boundaries were observed in annealing to 500° C. Positron-lifetime measurements are a useful complement to electron ... hélium. Des mesures de durée de vie des positrons ont été effectuées en suivant le recuit isochrone ...
Tópico(s): Bauxite Residue and Utilization
1977 - Elsevier BV | Journal of Nuclear Materials
Michael E. Phelps, E.J. Hoffman, C. Raybaud,
... E, Gómez-Vallejo V and Llop J (2012) Positron emission tomograghy with [13N]ammonia evidences long-term ... Zhang M (2012) Radiosynthesis of [13N]dantrolene, a positron emission tomography probe for breast cancer resistant protein, ... Benefits and risks of transforming data from dynamic positron emission tomography, with an application to hepatic encephalopathy, ... publication date: 1-Jan-2004. Schelbert H (2004) Positron Emission Tomography of the Heart: Methodology, Findings in ... publication date: 1-Oct-1985. Cone J (1985) Positron emission tomography: New analytic tool for vascular disease, ...
Tópico(s): S100 Proteins and Annexins
1977 - Lippincott Williams & Wilkins | Stroke
... and includes the effect of trapping on the positron distribution in the vicinity of the trap. Nonequilibrium ... to formulate the problem in order to include positron annihilation in a natural way. It is concluded ... is applicable if an initial distribution of thermalised positrons including the positron-phonon interaction is used. For stronger trapping the ... the golden rule is calculated and the corresponding positron density is examined. The positron density around the trap is altered by the ... by calculations of the time evolution of the positron density near a monovacancy.
Tópico(s): Graphene research and applications
1977 - IOP Publishing | Journal of Physics F Metal Physics
A positron pseudopotential is proposed that simplifies the description of a thermalized positron in a metal or alloy. The method is based on a factorization of the positron wave function into an energy-independent core function, which accounts for the detailed behavior of the positron when it approaches an ion core, and a ... number of alloys. The results indicate that the positron may have a strong preference or affinity for ... in binary alloys over the other. This relative positron affinity should lead to the positron preferentially annihilating ...
Tópico(s): X-ray Diffraction in Crystallography
1975 - American Physical Society | Physical review. B, Solid state
The momentum distribution of photon pairs from positrons annihilating in lithium, sodium, potassium, and rubidium has been measured over a wide temperature range. The results were analyzed to yield the momentum dependence of the enhancement factor, positron effective mass, and positron minimum energy in these metals. The annihilation rate ... body theoretical calculations. Assuming free-particle behavior, the positron effective mass has been determined to be approximately $ ... Using a more realistic momentum distribution for the positron, which includes the positron-phonon interaction, the effective ...
Tópico(s): Atomic and Molecular Physics
1975 - American Physical Society | Physical review. B, Solid state
Positron is an excellent probe of lattice defects in solids. A thermallized positron delocalized in lattice can be trapped at open ... defects, e.g. vacancies, dislocations, grain boundaries etc. Positron annihilation spectroscopy is a non-destructive technique which ... lattice defects in solids on the atomic scale. Positron lifetime and Doppler broadening of annihilation photo-peak are the most common observables related to positron annihilation process. Positron lifetime spectroscopy enables to identify ...
Tópico(s): Intermetallics and Advanced Alloy Properties
1975 - Pergamon Press | Scripta Metallurgica