Now showing items 21-40 of 5943

    • Degrees of symmetry in quantum field theories 

      Maris, Theodor August Johannes; Dillenburg, Darcy; Jacob, Gerhard; Liberman, Bernardo (1972) [Journal article]
      A hierarchy of possible symmetries in quantum field theory is defined, which reaches from a purely mathematical invariance to the conventional physical invariance, including the commonly discussed type of spontaneously ...
    • Nuclear-quadrupole interactions in perovskite-type compounds of hf/sup 181/ studied by the perturbed-angular-correlation technique 

      Andrade, Pedro da Rocha; Forker, Manfred; Rogers, John David; Kunzler, Julio Vitor (1972) [Journal article]
      Measurements of nuclear-quadrupole-interaction constants in perovskite-type compounds of PbHf03, SnHf03, CaHf03, and SrHf03 have been performed using the perturbed-angularcorrelation technique. A range of fundamental ...
    • Observation of the transparency of a resonant medium to zero-degree optical pulses 

      Grieneisen, Hans Peter Henrik; Goldhar, J.; Kurnit, N.A.; Javan, A.; Schlossberg, H.R. (1972) [Journal article]
      Experiments are described in which low-intensity laser pulses of zero area [f:'m8(z, t) dt=O) are propagated through a degenerate resonantly absorbing medium with greatly reduced absorption. These pulses are constructed ...
    • Probing the spin-orbit coupling of nuclear protons 

      Jacob, Gerhard; Maris, Theodor August Johannes; Schneider, Claudio; Teodoro, Maria Ribeiro (1973) [Journal article]
      The strong absorption in quasi-free scattering opens a possibility of measuring the spin-orbit coupling of nuclear protons. Cross sections for polarized incoming protons are expected to exhibit pronounced asymmetries, with ...
    • Exact photocount statistics : lasers near threshold 

      Lax, Melvin; Zwanziger, Marcus Guenter (1973) [Journal article]
      A previously constructed laser model with quantum (noncommuting) noise sources was shown to lead near threshold to a quantum rotating-wave Van der Pol oscillator. A full dynamical correspondence between quantum and classical ...
    • Magnetic breakdown and phase-coherent galvanomagnetic effects 

      Silva, Cylon Eudoxio Tricot Goncalves da; Falicov, Leo M. (1973) [Journal article]
      This paper presents a generalization of Pippard's network-model approach for the calculation of transport properties in metals in the presence of magnetic breakdown and partial phase coherence of the wave function. The ...
    • Study of rare-earth ions implanted into copper, aluminum, silver, and rhodium 

      Gebbie, D.W.; Scherer, Claudio; Huber, D.L.; Heestand, G.M.; Borches, R.R. (1973) [Journal article]
      Various even-even isotopes of Er, Dy, and Yb have been Coulomb excited to their first 2+ states and implanted into metallic foils of Cu, AI, Ag, and Rh. The attenuation of the subsequent y-ray angular distribution was ...
    • Study of the hyperfine magnetic field acting on /sup 181/ta nuclei in ni matrix 

      Livi, Flavio Pohlmann; Livi, Rogerio Pohlmann; Rogers, John David; Zawislak, Fernando Claudio (1973) [Journal article]
      Hyperfine interactions for Ta impurities in a polycrystalline nickel matrix produced by quenching from the melt have been studied using the perturbed-angular-correlation technique. An effective hyperfine field of -89.8 ± ...
    • Temperature dependence of the single-crystal elastic constants of co-rich co-fe alloys 

      Wazzan, A.R.; Bristoti, Anildo; Robinson, L.B.; Ahmedieh, A. (1973) [Journal article]
      The single-crystal elastic moduli, C11, C12, and C44 of three fcc cobalt-iron alloys (Co-6 at. % Fe, Co-8 at.% Fe, Co-10 at.% Fe) were measured in the range 0-315 °c. In addition C11 for the Co-6 at. % Fe alloy, and C' = ...
    • Proton spin-lattice relaxation in TMMC [(ch/Sub 3/)/Sub 4/Nmncl/Sub 3/] 

      Hone, Daniel; Scherer, Claudio; Borsa, Ferdinando (1974) [Journal article]
      We examine the temperature and frequency dependence of the proton spin-1attice re1axation rate 1/T 1, as a probe of the electron-spin dynamics of the quasi-one-dimensional exchange-coupled paramagnet TMMC [(CH3) 4NMnC1J. ...
    • On the electron-muon mass ratio 

      Dillenburg, Darcy; Maris, Theodor August Johannes (1975) [Journal article]
      The quantum electrodynamics (QED) of electrons is considered as a theory with a passive dilatation invariance which is perturbed by the electromagnetic coupling to hadrons and muons. A stability criterium is introduced and ...
    • Resonant Raman Scattering from Polaritons in Znse 

      Nicola, Jorge Humberto; Leite, Rogerio Cézar de Cerqueira (1975) [Journal article]
      Raman scattering from polaritons was studied near resonance in ZnSe. Detailed dispersion curves were determined experimentally for different incident frequencies and compared with theoretical results. Measurements of ...
    • Light scattering by lithium tantalate at room temperature 

      Penna, Antonio Fernando S.; Chaves, Alaor Silverio; Andrade, Pedro da Rocha; Porto, Sergio P.S. (1976) [Journal article]
      The room-temperature Raman spectra of LiTa03 for all symmetry phonons are investigated. We make a new assignment of the phonons, which agrees with the selection rules of a C3 symmetry instead of C3V, contrary to Kaminow ...
    • Electric quadrupole interactions of /sup 111/cd nuclei in the cubic ag lattice doped with sn impurity 

      Zawislak, Fernando Claudio; Livi, Rogerio Pohlmann; Schaf, Jacob; Behar, Moni (1976) [Journal article]
      The electric quadrupole interactions produced by near-neighbor impurity atoms of Sn on 111Cd probe nuclei in a cubic Ag lattice were studied by the time-differential perturbed angular correlation technique. The effects of ...
    • Testes de múltipla escolha e de resposta livre em física geral 

      Buchweitz, Bernardo (1976) [Journal article]
      São comparados os resultados de questões de múltipla escolha com os de questões de resposta livre de provas aplicadas em um curso de Física Geral. As questões comparadas envolveram diferentes níveis de comportamento e foram ...
    • Arquivamento em disco magnético e controle de periódicos através de um minicomputador 

      Berto, Zuleika; Costa Junior, Moacir Indio da (1977) [Journal article]
      É apresentado um novo sistema de armazenamento de registros dos periódicos correntes da Biblioteca em arquivo constituído por um disco magnético e controlado por minicomputador.
    • Temperature dependence of the electric field gradient in cubic ag metal doped with impurities 

      Zawislak, Fernando Claudio; Livi, Rogerio Pohlmann; Baumvol, Israel Jacob Rabin; Schaf, Jacob; Behar, Moni (1977) [Journal article]
    • Quasi-free scattering of polarized electrons by polarized nuclear protons 

      Herscovitz, Victoria Elnecave; Maris, Theodor August Johannes; Teodoro, Maria Ribeiro (1977) [Journal article]
      It Is shown that quasi-free electron scattering in a suitable geometry takes place on strongly polarized nuclear protons. A calculation for the single particle model of 160 predicts large asymmetries for the scattering of ...
    • Strip photometry of diffuse objects : i. the structure of comets kohoutek (1973 xii) and bradfield (1974 iii) 

      Strauss, Federico Maximo (1977) [Journal article]
      A high signal to noise ratio and good one dimensional resolution are obtained by scanning a narrow slit across extended objects. Several observations of two comets give information on total brightness and on the density ...
    • Some comments about a static-localized solution for the massive thirring model 

      Falomir, H.; Fanchiotti, H.; Saravi, R.E. Gamboa; Girotti, Horacio Oscar; Martin, H. (1977) [Journal article]
      We derive the stability equation for a static-localized solution of the two-dimensional massive Thirring model. The corresponding eigenvalue spectrum is determined and compared with the eigenvalue spectrum of the stability ...