5,900 research outputs found
Family farming in the agricultural census of 2006: the legal mark and the options for their identification.
(Agricultura familiar no censo agropecuário 2006: o marco legal e as opções para sua identificação). Visando delimitar a agricultura familiar no Censo Agropecuário 2006, o Ministério do Desenvolvimento Agrário (MDA) e o Instituto Brasileiro de Geografia e Estatística (IBGE) elaboraram metodologia para construção de uma variável identificando os estabelecimentos agropecuários recenseados e que se ajustam ao conceito previsto na Lei n.11.326, de 24 de julho de 2006. O texto apresenta os passos metodológicos utilizados e alguns resultados
High-resolution radio imaging of two luminous quasars beyond redshift 4.5
Context. Radio-loud active galactic nuclei in the early Universe are rare.
The quasars J0906+6930 at redshift z=5.47 and J2102+6015 at z=4.57 stand out
from the known sample with their compact emission on milliarcsecond (mas)
angular scale with high (0.1-Jy level) flux densities measured at GHz radio
frequencies. This makes them ideal targets for very long baseline
interferometry (VLBI) observations. Aims. By means of VLBI imaging we can
reveal the inner radio structure of quasars and model their brightness
distribution to better understand the geometry of the jet and the physics of
the sources. Methods. We present sensitive high-resolution VLBI images of
J0906+6930 and J2102+6015 at two observing frequencies, 2.3 and 8.6 GHz. The
data were taken in an astrometric observing programme involving a global
five-element radio telescope array. We combined the data from five different
epochs from 2017 February to August. Results. For one of the highest redshift
blazars known, J0906+6930, we present the first-ever VLBI image obtained at a
frequency below 8 GHz. Based on our images at 2.3 and 8.6 GHz, we confirm that
this source has a sharply bent helical inner jet structure within ~3 mas from
the core. The quasar J2102+6015 shows an elongated radio structure in the
east-west direction within the innermost ~2 mas that can be described with a
symmetric three-component brightness distribution model at 8.6 GHz. Because of
their non-pointlike mas-scale structure, these sources are not ideal as
astrometric reference objects. Our results demonstrate that VLBI observing
programmes conducted primarily with astrometric or geodetic goals can be
utilized for astrophysical purposes as well.Comment: 8 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic
On the heating of source of the Orion KL hot core
We present images of the J=10-9 rotational lines of HC3N in the vibrationally
excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images
show that the spatial distribution and the size emission from the 1v7 and 1v5
levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and
peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is
unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear
indication that the HC is composed of condensations with very different
temperatures (170 K for the 1v7 peak and K for the 1v5 peak). The
temperature derived from the 1v7 and 1v5 lines increases with the projected
distance to the suspected main heating source I. Projection effects along the
line of sight could explain the temperature gradient as produced by source I.
However, the large luminosity required for source I, >5 10^5 Lsolar, to explain
the 1v5 line suggests that external heating by this source may not dominate the
heating of the HC. Simple model calculations of the vibrationally excited
emission indicate that the HC can be internally heated by a source with a
luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south
of source I). We also report the first detection of high-velocity gas from
vibrationally excited HC3N emission. Based on excitation arguments we conclude
that the main heating source is also driving the molecular outflow. We
speculate that all the data presented in this letter and the IR images are
consistent with a young massive protostar embedded in an edge-on disk.Comment: 13 pages, 3 figures, To be published in Ap.J. Letter
meson transparency in nuclei from resonant interactions
We investigate the meson nuclear transparency using some recent
theoretical developments on the in medium self-energy. The inclusion of
direct resonant -scattering and the kaon decay mechanisms leads to a
width much larger than in most previous theoretical approaches. The
model has been confronted with photoproduction data from CLAS and LEPS and the
recent proton induced production from COSY finding an overall good
agreement. The results support the need of a quite large direct -scattering contribution to the self-energy
Unconscious Learning. Conditioning to Subliminal Visual Stimuli.
Se analizó el papel de la consciencia en el condicionamiento pavloviano mediante dos experimentos en los que se utilizaron, como estímulos condicionados (ECs), palabras neutras visualmente enmascaradas y, como estímulo incondicionado (EI), un shock eléctrico. El intervalo inter-estímulo se estableció individualmente. Se utilizó un umbral de detección en el Experimento 1 y un umbral de identificación en el Experimento 2. La principal variable dependiente fue la respuesta de conductancia de la piel. Los resultados mostraron que la respuesta condicionada (RC) fue adquirida por el 58% de los sujetos que percibieron los estímulos por encima del umbral de identificación, por el 50% de los sujetos que percibieron los estímulos por debajo del umbral de detección y por el 11% de los sujetos que percibieron los estímulos por debajo del umbral de identificación, pero por encima del umbral de detección. Estos resultados sugieren que la conciencia de la contingencia EC-EI no es condición necesaria para adquirir una RC del sistema nervioso autónomo
Citation Flows in the Zones of Influence of Scientific
Domestic citation to papers from the same country and the greater citation impact of documents involving international collaboration are two phenomena that have been extensively studied and contrasted. Here, however, we showthat it is not somuch a national bias,but that papers have a greater impact on their immediate environments, an impact that is diluted as that environment grows. For this reason, the greatest biases are observed in countries
with a limited production. Papers that involve international collaboration have a greater impact in general, on the one hand, because they have multiple “immediate
environments,” and on the other because of their greater quality or prestige. In short, one can say that science knows no frontiers. Certainly there is a greater impact
on the authors’ immediate environment, but this does not necessarily have to coincide with their national environments, which fade in importance as the collaborative
environment expands
No asymmetric outflows from Sagittarius A* during the pericenter passage of the gas cloud G2
The gas cloud G2 falling toward Sagittarius A* (Sgr A*), the supermassive
black hole at the center of the Milky Way, is supposed to provide valuable
information on the physics of accretion flows and the environment of the black
hole. We observed Sgr A* with four European stations of the Global Millimeter
Very Long Baseline Interferometry Array (GMVA) at 86 GHz on 1 October 2013 when
parts of G2 had already passed the pericenter. We searched for possible
transient asymmetric structure -- such as jets or winds from hot accretion
flows -- around Sgr A* caused by accretion of material from G2. The
interferometric closure phases remained zero within errors during the
observation time. We thus conclude that Sgr A* did not show significant
asymmetric (in the observer frame) outflows in late 2013. Using simulations, we
constrain the size of the outflows that we could have missed to ~2.5 mas along
the major axis, ~0.4 mas along the minor axis of the beam, corresponding to
approximately 232 and 35 Schwarzschild radii, respectively; we thus probe
spatial scales on which the jets of radio galaxies are suspected to convert
magnetic into kinetic energy. As probably less than 0.2 Jy of the flux from Sgr
A* can be attributed to accretion from G2, one finds an effective accretion
rate eta*Mdot < 1.5*10^9 kg/s ~ 7.7*10^-9 Mearth/yr for material from G2.
Exploiting the kinetic jet power--accretion power relation of radio galaxies,
one finds that the rate of accretion of matter that ends up in jets is limited
to Mdot < 10^17 kg/s ~ 0.5 Mearth/yr, less than about 20% of the mass of G2.
Accordingly, G2 appears to be largely stable against loss of angular momentum
and subsequent (partial) accretion at least on time scales < 1 year.Comment: 5 pages, 2 figures, 1 table; A&A Letter, in press (submitted 2015
February 26; accepted 2015 March 31
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