105 research outputs found
Desenvolvimento profissional durante a implementação de inovações curriculares por professores do ensino secundário
Neste trabalho, apresentamos os primeiros resultados de uma pesquisa com cinco professores de física do ensino secundário que participaram de um projeto de inovação curricular na implementação de seqüências didáticas de ensino aprendizagem (Teaching and Learning Sequence) sobre Física Moderna. Por meio de questionário e entrevista semi-estruturada, buscou-se a partir da análise relacionar as fases de desenvolvimento profissional dos professores. Percebemos nos casos estudados, que alguns professores apresentaram uma discordância entre as fases deste desenvolvimento. Os resultados parecem indicar que a participação de professores em grupos de projetos inovadores no Ensino de Física, pode contribuir para consolidar seu desenvolvimento profissional na fase da experimentação ou diversificação
Dificuldades de professores de física em início de carreira
Neste trabalho, procuramos, através de uma pesquisa qualitativa, realizada por meio de entrevistas e narrativas, identificar as principais dificuldades encontradas por três professores de física em início de carreira. Percebemos nos casos estudados, que, ao se depararem com a realidade de sala de aula em suas primeiras experiências, os professores se chocam com questões básicas do ensino, como a indisciplina, a motivação dos estudantes, como se portar em sala e que, nos momentos iniciais, estas questões fazem parte do seu desenvolvimento profissional assim como muitas vezes determinam a continuidade ou não de alguns professores em suas carreiras. Apresentamos nossos dados, relacionando, classificando e analisando as principais dificuldades encontradas por estes professores, a luz de algumas teorias relacionadas à formação de professores
Measurement of the reaction \gamma p \TO K^ + \Lambda(1520) at photon energies up to 2.65 GeV
The reaction \gamma p \TO K^+\Lambda(1520) was measured in the energy range
from threshold to 2.65 GeV with the SAPHIR detector at the electron stretcher
facility ELSA in Bonn. The production cross section was
analyzed in the decay modes , , , and
as a function of the photon energy and the squared
four-momentum transfer . While the cross sections for the inclusive
reactions rise steadily with energy, the cross section of the process \gamma p
\TO K^+\Lambda(1520) peaks at a photon energy of about 2.0 GeV, falls off
exponentially with , and shows a slope flattening with increasing photon
energy. The angular distributions in the -channel helicity system indicate
neither a nor a exchange dominance. The interpretation of the
as a molecule is not supported.Comment: 11 pages, 16 figures, 4 table
Dificuldades de professores de física em início de carreira
Neste trabalho, procuramos, através de uma pesquisa qualitativa, realizada por meio de entrevistas e narrativas, identificar as principais dificuldades encontradas por três professores de física em início de carreira. Percebemos nos casos estudados, que, ao se depararem com a realidade de sala de aula em suas primeiras experiências, os professores se chocam com questões básicas do ensino, como a indisciplina, a motivação dos estudantes, como se portar em sala e que, nos momentos iniciais, estas questões fazem parte do seu desenvolvimento profissional assim como muitas vezes determinam a continuidade ou não de alguns professores em suas carreiras. Apresentamos nossos dados, relacionando, classificando e analisando as principais dificuldades encontradas por estes professores, a luz de algumas teorias relacionadas à formação de professores
Gerasimov-Drell-Hearn Sum Rule and the Discrepancy between the New CLAS and SAPHIR Data
Contribution of the K^+\Lambda channel to the Gerasimov-Drell-Hearn (GDH) sum
rule has been calculated by using the models that fit the recent SAPHIR or CLAS
differential cross section data. It is shown that the two data sets yield quite
different contributions. Contribution of this channel to the forward spin
polarizability of the proton has been also calculated. It is also shown that
the inclusion of the recent CLAS C_x and C_z data in the fitting data base does
not significantly change the result of the present calculation. Results of the
fit, however, reveal the role of the S_{11}(1650), P_{11}(1710), P_{13}(1720),
and P_{13}(1900) resonances for the description of the C_x and C_z data. A
brief discussion on the importance of these resonances is given. Measurements
of the polarized total cross section \sigma_{TT'} by the CLAS, LEPS, and MAMI
collaborations are expected to verify this finding.Comment: 15 pages, 8 figure
Measurement of gamma p --> K+ Lambda and gamma p --> K+ Sigma0 at photon energies up to 2.6 GeV
The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured
in the energy range from threshold up to a photon energy of 2.6 GeV. The data
were taken with the SAPHIR detector at the electron stretcher facility, ELSA.
Results on cross sections and hyperon polarizations are presented as a function
of kaon production angle and photon energy. The total cross section for Lambda
production rises steeply with energy close to threshold, whereas the Sigma0
cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross
sections together with their angular decompositions into Legendre polynomials
suggest contributions from resonance production for both reactions. In general,
the induced polarization of Lambda has negative values in the kaon forward
direction and positive values in the backward direction. The magnitude varies
with energy. The polarization of Sigma0 follows a similar angular and energy
dependence as that of Lambda, but with opposite sign.Comment: 21 pages, 25 figures, submitted to Eur. Phys. J.
Quantum-state control in optical lattices
We study the means to prepare and coherently manipulate atomic wave packets
in optical lattices, with particular emphasis on alkali atoms in the
far-detuned limit. We derive a general, basis independent expression for the
lattice operator, and show that its off-diagonal elements can be tailored to
couple the vibrational manifolds of separate magnetic sublevels. Using these
couplings one can evolve the state of a trapped atom in a quantum coherent
fashion, and prepare pure quantum states by resolved-sideband Raman cooling. We
explore the use of atoms bound in optical lattices to study quantum tunneling
and the generation of macroscopic superposition states in a double-well
potential. Far-off-resonance optical potentials lend themselves particularly
well to reservoir engineering via well controlled fluctuations in the
potential, making the atom/lattice system attractive for the study of
decoherence and the connection between classical and quantum physics.Comment: 35 pages including 8 figures. To appear in Phys. Rev. A. March 199
Evidence for the positive-strangeness pentaquark in photoproduction with the SAPHIR detector at ELSA
The positive--strangeness baryon resonance is observed in
photoproduction of the final state with the SAPHIR detector at
the Bonn ELectron Stretcher Accelerator ELSA. It is seen as a peak in the invariant mass distribution with a confidence level. We find
a mass MeV and an upper limit of the width
MeV at 90% c.l. From the absence of a signal in
the invariant mass distribution in at the
expected strength we conclude that the must be isoscalar.Comment: 9 pages, 4 figure
Atomic collision dynamics in optical lattices
We simulate collisions between two atoms, which move in an optical lattice
under the dipole-dipole interaction. The model describes simultaneously the two
basic dynamical processes, namely the Sisyphus cooling of single atoms, and the
light-induced inelastic collisions between them. We consider the J=1/2 -> J=3/2
laser cooling transition for Cs, Rb and Na. We find that the hotter atoms in a
thermal sample are selectively lost or heated by the collisions, which modifies
the steady state distribution of atomic velocities, reminiscent of the
evaporative cooling process.Comment: 17 pages, 15 figure
Laser cooling of trapped atoms to the ground state : a dark state in position space
We propose a scheme that allows us to laser cool trapped atoms to the ground state of a one-dimensional confining potential. The scheme is based on the creation of a dark state by designing the laser profile, so that the hottest atoms are coherently pumped to another internal level, and then repumped back. The scheme works beyond the Lamb-Dicke limit. We present results of a full quantum treatment for a one-dimensional model
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