782 research outputs found
Electromagnetic form factors of light vector mesons
The electromagnetic form factors G_E(q^2), G_M(q^2), and G_Q(q^2), charge
radii, magnetic and quadrupole moments, and decay widths of the light vector
mesons rho^+, K^{*+} and K^{*0} are calculated in a Lorentz-covariant,
Dyson-Schwinger equation based model using algebraic quark propagators that
incorporate confinement, asymptotic freedom, and dynamical chiral symmetry
breaking, and vector meson Bethe-Salpeter amplitudes closely related to the
pseudoscalar amplitudes obtained from phenomenological studies of pi and K
mesons. Calculated static properties of vector mesons include the charge radii
and magnetic moments: r_{rho+} = 0.61 fm, r_{K*+} = 0.54 fm, and r^2_{K*0} =
-0.048 fm^2; mu_{rho+} = 2.69, mu_{K*+} = 2.37, and mu_{K*0} = -0.40. The
calculated static limits of the rho-meson form factors are similar to those
obtained from light-front quantum mechanical calculations, but begin to differ
above q^2 = 1 GeV^2 due to the dynamical evolution of the quark propagators in
our approach.Comment: 8 pages of RevTeX, 5 eps figure
Sub-terahertz, microwaves and high energy emissions during the December 6, 2006 flare, at 18:40 UT
The presence of a solar burst spectral component with flux density increasing
with frequency in the sub-terahertz range, spectrally separated from the
well-known microwave spectral component, bring new possibilities to explore the
flaring physical processes, both observational and theoretical. The solar event
of 6 December 2006, starting at about 18:30 UT, exhibited a particularly
well-defined double spectral structure, with the sub-THz spectral component
detected at 212 and 405 GHz by SST and microwaves (1-18 GHz) observed by the
Owens Valley Solar Array (OVSA). Emissions obtained by instruments in
satellites are discussed with emphasis to ultra-violet (UV) obtained by the
Transition Region And Coronal Explorer (TRACE), soft X-rays from the
Geostationary Operational Environmental Satellites (GOES) and X- and gamma-rays
from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The sub-THz
impulsive component had its closer temporal counterpart only in the higher
energy X- and gamma-rays ranges. The spatial positions of the centers of
emission at 212 GHz for the first flux enhancement were clearly displaced by
more than one arc-minute from positions at the following phases. The observed
sub-THz fluxes and burst source plasma parameters were found difficult to be
reconciled to a purely thermal emission component. We discuss possible
mechanisms to explain the double spectral components at microwaves and in the
THz ranges.Comment: Accepted version for publication in Solar Physic
Anticorpos contra lentivírus de pequenos ruminantes em caprinos e ovinos em abatedouros do estado de Pernambuco
Tri-meson-mixing of -- and -- in the light-cone quark model
The radiative transition form factors of the pseudoscalar mesons {,
, } and the vector mesons {, , } are restudied
with -- and -- in tri-meson-mixing
pattern, which is described by tri-mixing matrices in the light-cone
constituent quark model. The experimental transition decay widths are better
reproduced with tri-meson-mixing than previous results in a two-mixing-angle
scenario of only two-meson - mixing and - mixing.Comment: 8 pages, 6 figures, final version to appear in EPJ
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Parity Violation Constraints Using Cosmic Microwave Background Polarization Spectra from 2006 and 2007 Observations by the QUaD Polarimeter
We constrain parity-violating interactions to the surface of last scattering using spectra from the QUaD experiment’s second and third seasons of observations by searching for a possible systematic rotation of the polarization directions of cosmic microwave background photons. We measure the rotation angle due to such a possible ‘‘cosmological birefringence’’ to be (random) (systematic) using QUaD’s 100 and 150 GHz temperature-curl and gradient-curl spectra over the spectra over the multipole range 200 << 2000, consistent with null, and constrain Lorentz-violating interactions to <2 10 GeV (68% confidence limit). This is the best constraint to date on electrodynamic parity violation on cosmological scales.Astronom
Second and Third Season QUaD Cosmic Microwave Background Temperature and Polarization Power Spectra
We report results from the second and third seasons of observation with the QUaD experiment. Angular
power spectra of the cosmic microwave background are derived for both temperature and polarization at
both 100 GHz and 150 GHz, and as cross-frequency spectra. All spectra are subjected to an extensive
set of jackknife tests to probe for possible systematic contamination. For the implemented data cuts and
processing technique such contamination is undetectable. We analyze the difference map formed between the
100 and 150 GHz bands and find no evidence of foreground contamination in polarization. The spectra are
then combined to form a single set of results which are shown to be consistent with the prevailing LCDM
model. The sensitivity of the polarization results is considerably better than that of any previous experiment—
for the first time multiple acoustic peaks are detected in the E-mode power spectrum at high significance
The QUAD Galactic Plane Survey 1: Maps and Analysis of Diffuse Emission
We present a survey of ~ 800 square degrees of the galactic plane observed with the QUaD telescope. The
primary product of the survey are maps of Stokes I, Q and U parameters at 100 and 150 GHz, with spatial
resolution 5 and 3.5 arcminutes respectively. Two regions are covered, spanning approximately 245 - 295°
and 315 - 5° in galactic longitude l, and -4 < b < +4° in galactic latitude b. At 0:02° square pixel size, the
median sensitivity is 74 and 107 kJy/sr at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy/sr for
Q and U. In total intensity, we find an average spectral index of α = 2:35+-0:01(stat)+-0:02(sys) for |b| ≤1°,
indicative of emission components other than thermal dust. A comparison to published dust, synchrotron
and free-free models implies an excess of emission in the 100 GHz QUaD band, while better agreement is
found at 150 GHz. A smaller excess is observed when comparing QUaD 100 GHz data to WMAP 5-year
W band; in this case the excess is likely due to the wider bandwidth of QUaD. Combining the QUaD and
WMAP data, a two-component spectral fit to the inner galactic plane (|b| ≤1°) yields mean spectral indices
of αs = -0:32+-0:03 and αd = 2:84+-0:03; the former is interpreted as a combination of the spectral indices
of synchrotron, free-free and dust, while the second is attributed largely to the thermal dust continuum. In
the same galactic latitude range, the polarization data show a high degree of alignment perpendicular to the
expected galactic magnetic field direction, and exhibit mean polarization fraction 1:38+-0:08(stat)+-0:1(sys)%
at 100 GHz and 1:70+-0:06(stat)+-0:1(sys)% at 150 GHz. We find agreement in polarization fraction between
QUaD 100 GHz and WMAP W band, the latter giving 1:1+-0:4%
Alain Crosnier’s role in modern carcinology: exploration, international collaboration, and taxonomy
Este artículo contiene 8 páginas, 5 figuras.The French carcinologist and oceanographer Alain Crosnier (1930–2021) had a most influential role in modern carcinology. This tribute reviews his contributions to organising oceanographic expeditions; expanding collections of specimens, particularly from the deep sea; and
supporting international collaboration for taxonomic investigations of the rich collections of
material obtained from these expeditions. His expertise and enthusiasm also extended to the
publication of the results of these investigations.Peer reviewe
Origin of the submillimeter radio emission during the time-extended phase of a solar flare
Solar flares observed in the 200-400 GHz radio domain may exhibit a slowly
varying and time-extended component which follows a short (few minutes)
impulsive phase and which lasts for a few tens of minutes to more than one
hour. The few examples discussed in the literature indicate that such
long-lasting submillimeter emission is most likely thermal bremsstrahlung. We
present a detailed analysis of the time-extended phase of the 2003 October 27
(M6.7) flare, combining 1-345 GHz total-flux radio measurements with X-ray,
EUV, and H{\alpha} observations. We find that the time-extended radio emission
is, as expected, radiated by thermal bremsstrahlung. Up to 230 GHz, it is
entirely produced in the corona by hot and cool materials at 7-16 MK and 1-3
MK, respectively. At 345 GHz, there is an additional contribution from
chromospheric material at a few 10^4 K. These results, which may also apply to
other millimeter-submillimeter radio events, are not consistent with the
expectations from standard semi-empirical models of the chromosphere and
transition region during flares, which predict observable radio emission from
the chromosphere at all frequencies where the corona is transparent.Comment: 27 pages, 7 figure
Leishmania amazonensis downregulates macrophage iNOS expression via Histone Deacetylase 1 (HDAC1): a novel parasite evasion mechanism.
The induced expression of nitric oxide synthase (iNOS) controls the intracellular growth of Leishmania in infected macrophages. Histones deacetylases (HDACs) negatively regulate gene expression through the formation of complexes containing transcription factors such as NF-κB p50/50. Herein, we demonstrated the occupancy of p50/p50_HDAC1 to iNOS promoter associated with reduced levels of H3K9Ac. Remarkably, we found increased levels of HDAC1 in L. amazonensis-infected macrophages. HDAC1 upregulation was not found in L. major-infected macrophages. The parasite intracellular load was reduced in HDAC1 knocked-down macrophages, which presented increased nitric oxide levels. HDAC1 silencing led to the occupancy of CBP/p300 to iNOS promoter and the rise of H3K9Ac modification. Importantly, the immunostaining of skin samples from hiporeactive cutaneous leishmaniasis patients infected with L. amazonensis, revealed high levels of HDAC1. In brief, L. amazonensis induces HDAC1 in infected macrophages, which contribute to parasite survival and is associated to hiporeactive stage found in L. amazonensis infected patients
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