4,475 research outputs found
Teaching and critically reflective practice in Freire
Few of the many books written by Freire drew particular, and extended, attention to the teacher in the way Pedagogy of Freedom (1998) was able to do. While this entry draws on many other important works by Freire, it specifically probes elements of this book to place before readers some of the salient qualities and attributes Freire believed teachers, educators and thinkers of education ought to aspire to
Radio Timing and Optical Photometry of the Black Widow System PSR J1953+1846A in the Globular Cluster M71
We report on the determination of the astrometric, spin and orbital
parameters for PSR J1953+1846A, a "black widow" binary millisecond pulsar in
the globular cluster M71. By using the accurate position and orbital parameters
obtained from radio timing, we identified the optical companion in ACS/Hubble
Space Telescope images. It turns out to be a faint (m_F606W>=24, m_F814W>=23)
and variable star located at only ~0.06" from the pulsar timing position. The
light curve shows a maximum at the pulsar inferior conjunction and a minimum at
the pulsar superior conjunction, thus confirming the association with the
system. The shape of the optical modulation suggests that the companion star is
heated, likely by the pulsar wind. The comparison with the X-ray light curve
possibly suggests the presence of an intra-binary shock due to the interaction
between the pulsar wind and the material released by the companion. This is the
second identification (after COM-M5C) of an optical companion to a black widow
pulsar in a globular cluster. Interestingly, the two companions show a similar
light curve and share the same position in the color magnitude diagram.Comment: Accepted for publication by ApJ; 33 Pages, 10 Figures, 3 Table
Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12
We investigate on the relative inclination of the planets B and C orbiting
the pulsar PSR B1257+12 in connection with potential violations of the
equivalence principle (Abridged).Comment: LaTex2e, 10 pages, 1 table, 3 figures, 17 references. Small stylistic
changes. Version to appear in Journal of Astrophysics and Astronomy (JAA
Component release after exposure of Staphylococcus aureus cells to pulsed electric fields
The objective of this work was to get further insights on the mechanism of inactivation of bacterial cells by pulsed electric fields (PEF) through the study of the release of intracellular components after exposing Staphylococcus aureus cells in McIvlaine buffer (pH 7.0, 2 mS/cm) to PEF treatments of different intensity (18 and 25 kV/cm) and treatment times (from 20 to 400 mu s). Release of most compounds, except proteins, was almost immediate after the treatment, but the relative amount released depended on the molecule studied. A good correlation between the release of the smallest components studied (particularly ions) and membrane permeabilization (as measured by NaCl sensitization and PI entry) was observed. On the other hand, results obtained suggested that S. aureus inactivation by PEF would be related to the exit of cytoplasmic proteins of a molecular weight higher than 6 kDa. Results obtained in this work indicated that increasing PEF treatment time would reduce the capability of S. aureus cells to repair the electropores formed and suggested that this might be due to the formation of pores of a larger size, which S. aureus cells would be unable to reseal in a situation of homeostasis loss. Industrial relevance: Results reported here can help to design more effective treatments for microbial inactivation using PEF on food, and therefore facilitate its industrial implementation
Radio timing and optical photometry of the black widow system PSR J1518+0204C in the globular cluster M5
We report on the determination of astrometric, spin and orbital parameters
for PSR J1518+0204C, a "black widow" binary millisecond pulsar in the globular
cluster M5. The accurate position and orbital parameters obtained from radio
timing allowed us to search for the optical companion. By using WFC3/HST images
we identified a very faint variable star (m_F390W > 24.8, m_F606W > 24.3,
m_F814W > 23.1) located at only 0.25" from the pulsar's timing position. Due to
its strong variability, this star is visible only in a sub-sample of images.
However, the light curve obtained folding the available data with the orbital
parameters of the pulsar shows a maximum at the pulsar inferior conjunction and
a possible minimum at the pulsar superior conjunction. Furthermore, the shape
of the optical modulation indicates a heating process possibly due to the
pulsar wind. This is the first identification of an optical companion to a
black widow pulsar in the dense stellar environment of a globular cluster.Comment: Accepted for publication by ApJ; 24 Pages, 5 Figures, 1 Tabl
Micotoxinas: importância na alimentação e na saúde humana e animal.
Principais micotoxinas. Regulamentação de micotoxinas no Brasil e no mundo. Considerações finais.bitstream/CNPAT-2010/10830/1/Dc-110.pd
Is there Quark Matter in (Low-Mass) Pulsars?
The effect of the QCD phase transition is studied for the mass-radius
relation of compact stars and for hot and dense matter at a given proton
fraction used as input in core-collapse supernova simulations. The phase
transitions to the 2SC and CFL color superconducting phases lead to stable
hybrid star configurations with a pure quark matter core. In supernova
explosions quark matter could be easily produced due to -equilibrium,
small proton fractions and nonvanishing temperatures. A low critical density
for the phase transition to quark matter is compatible with present pulsar mass
measurements.Comment: 4 pages, 3 figures, talk given at the QM2008 conference, Jaipur,
India, February 4-10, 2008, JPG in pres
Quark-hadron phase transition in a neutron star under strong magnetic fields
We study the effect of a strong magnetic field on the properties of neutron
stars with a quark-hadron phase transition. It is shown that the magnetic field
prevents the appearance of a quark phase, enhances the leptonic fraction,
decreases the baryonic density extension of the mixed phase and stiffens the
total equation of state, including both the stellar matter and the magnetic
field contributions. Two parametrisations of a density dependent static
magnetic field, increasing, respectively, fast and slowly with the density and
reaching G in the center of the star, are considered. The
compact stars with strong magnetic fields have maximum mass configurations with
larger masses and radius and smaller quark fractions. The parametrisation of
the magnetic field with density has a strong influence on the star properties.Comment: 15 pages, 6 figures, 8 tables, accepted for publication in J. Phys.
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