4,911 research outputs found
Water Maser Emission from the Active Nucleus in M51
22 GHz water vapor `kilomaser' emission is reported from the central region
of the Whirlpool galaxy M 51 (NGC 5194). The red-shifted spectral features
(Vlsr ~ 560 km/s), flaring during most of the year 2000, originate from a
spatially unresolved maser spot of size < 30 mas (< 1.5 pc), displaced by < 250
mas from the nucleus. The data provide the first direct evidence for the
association of an H2O kilomaser with an active galactic nucleus (AGN). In early
2001, blue-shifted maser emission (Vlsr ~ 435 km/s) was also detected. Red- and
blue-shifted features bracket the systemic velocity asymmetrically. Within the
standard model of a rotating Keplerian torus, this may either suggest the
presence of a highly eccentric circumnuclear cloud or red- and blue-shifted
`high velocity' emission from a radially extended torus. Most consistent with
the measured H2O position is, however, an association of the red-shifted H2O
emission with the northern part of the bipolar radio jet. In this scenario, the
(weaker) northern jet is receding while the blue-shifted H2O emission is
associated with the approaching southern jet.Comment: 9 pages, 1 figur
Strongly Coupled Semi-Direct Mediation of Supersymmetry Breaking
Strongly coupled semi-direct gauge mediation models of supersymmetry breaking
through massive mediators with standard model charges are investigated by means
of composite degrees of freedom. Sizable mediation is realized to generate the
standard model gaugino masses for a small mediator mass without breaking the
standard model symmetries.Comment: 7 pages; v2: the model generalized, gaugino mass corrected; v3:
explanations expanded, references adde
Specific heat and low-lying excitations in the mixed state for a type II superconductor
Low temperature behavior of the electronic specific heat in the mixed
state is by the self-consistent calculation of the Eilenberger theory. In
addition to -term ( is a Sommerfeld coefficient), has
significant contribution of -term intrinsic in the vortex state. We
identify the origin of the -term as (i) V-shape density of states in the
vortex state and (ii) Kramer-Pesch effect of vortex core shrinking upon
lowering . These results both for full-gap and line node cases reveal that
the vortex core is a richer electronic structure beyond the normal core
picture.Comment: Accepted in Phys. Rev. B. 5 pages, 5 figure
Utilizando R para manipular dados de projeção climática.
O Laboratório de Modelagem Agroambiental (LMA) da Embrapa Informática Agropecuária utiliza dados de projeção climática para realização de simulações de cenários agrícolas futuros. Grande parte desses dados é disponibilizada no formato NetCDF. A NetCDF é uma biblioteca livre, que possui funções de manipulação de dados armazenados em matrizes que contêm dimensões, variáveis e metadados. É utilizada em linguagens como C, C++, Fortran, Java, R entre outras. Essa combinação entre linguagem, biblioteca e arquivo possibilita criação, acesso e compartilhamento de dados científicos. Os arquivos NetCDF possuem informações descritivas sobre os dados que contêm (os chamados metadados). Podem armazenar diferentes tipos de variáveis numéricas e caracteres. Além disso, o formato é eficiente, permitindo ao usuário acessar um pequeno subconjunto de uma grande base de dados, visualizar simultaneamente o mesmo arquivo por mais de um leitor e anexar dados a um arquivo NetCDF, sem ter que copiar sua base de dados ou redefinir sua estrutura. Antes de serem utilizados, esses dados passam por diversos processamentos, tais como recorte temporal e espacial, reamostragem de grade e extração de dados. O objetivo deste trabalho é demonstrar como tais processamentos podem ser realizados utilizando o R
The Distribution of H2O Maser Emission in the Nucleus of NGC 4945
We present the first interferometer map of the water maser emission in the
active nucleus of NGC 4945. Although the declination of the galaxy is about -49
degrees, we were able to make the observations with the southernmost antennas
of the Very Long Baseline Array. Strong maser emission is present in three
velocity ranges, one near the systemic velocity and two shifted roughly
symmetrically by +/-(100-150) km/s. This is the first detection of highly
blue-shifted water emission in NGC 4945. We determined the position of the
maser to be RA(B1950)= 13 02 32.28 +/- 0.02 ; Dec(B1950)= -49 12 01.9 +/- 0.1.
The uncertainties in earlier estimates are at least several arcseconds. The
maser lies within 2'' (36 pc at a distance of 3.7 Mpc) of the peaks in 1.4 GHz
continuum and 1.6 micron emission from the nucleus. The mappable maser emission
is distributed roughly linearly over about 40 milliarcseconds (0.7 pc) at a
position angle of about 45 degrees, which is close to the 43 +/- 2 degree
position angle of the galactic disk. The red and blue-shifted emission
symmetrically stradle the systemic emission on the sky, which suggests material
in edge-on circular motion around a central object. The position-velocity
structure indicates a binding mass of about one million Suns, within a volume
of radius about 0.3 pc. This implies that the central engine radiates on the
order of 10% of its Eddington luminosity.Comment: 18 pages, including 5 Postscript figures. Accepted for publication in
ApJ Letter
All-or-none switching of transcriptional activity on single DNA molecules caused by a discrete conformational transition
Recently, it has been confirmed that long duplex DNA molecules with sizes
larger than several tens of kilo-base pairs (kbp), exhibit a discrete
conformational transition from an elongated coil state to a compact globule
state upon the addition of various kinds of chemical species that usually
induce DNA condensation. In this study, we performed a single-molecule
observation on a large DNA, Lambda ZAP II DNA (ca. 41 kbp), in a solution
containing RNA polymerase and substrates along with spermine, a tetravalent
cation, at different concentrations, by use of fluorescence staining of both
DNA and RNA. We found that transcription, or RNA production, is completely
inhibited in the compact state, but is actively performed in the unfolded coil
state. Such an all-or-none effect on transcriptional activity induced by the
discrete conformational transition of single DNA molecules is discussed in
relation to the mechanism of the regulation of large-scale genetic activity.Comment: 14 pages, 2 figure
Avaliação de banco de dados raster para o projeto Natdata.
O projeto Natdata pretende sobrepor esses desafios, visando, ao final, a implantação de uma plataforma que integre os dados de recursos naturais da Embrapa, ainda muito heterogêneos e provenientes de diferentes domínios, e muitas vezes de outras instituições, garantindo a manutenção de sua semântica
Toward a New Distance to the Active Galaxy NGC 4258: II. Centripetal Accelerations and Investigation of Spiral Structure
We report measurements of centripetal accelerations of maser spectral
components of NGC 4258 for 51 epochs spanning 1994 to 2004. This is the second
paper of a series, in which the goal is determination of a new geometric maser
distance to NGC 4258 accurate to possibly ~3%. We measure accelerations using a
formal analysis method that involves simultaneous decomposition of maser
spectra for all epochs into multiple, Gaussian components. Components are
coupled between epochs by linear drifts (accelerations) from their centroid
velocities at a reference epoch. For high-velocity emission, accelerations lie
in the range -0.7 to +0.7 km/s/yr indicating an origin within 13 degrees of the
disk midline (the perpendicular to the line-of-sight to the black hole).
Comparison of high-velocity emission projected positions in VLBI images, with
those derived from acceleration data, provides evidence that masers trace real
gas dynamics. High-velocity emission accelerations do not support a model of
trailing shocks associated with spiral arms in the disk. However, we find
strengthened evidence for spatial periodicity in high-velocity emission, of
wavelength 0.75 mas. This supports suggestions of spiral structure due to
density waves in the nuclear accretion disk of an active galaxy. Accelerations
of low-velocity (systemic) emission lie in the range 7.7 to 8.9 km/s/yr,
consistent with emission originating from a concavity where the thin, warped
disk is tangent to the line-of-sight. A trend in accelerations of low-velocity
emission as a function of Doppler velocity may be associated with disk geometry
and orientation, or with the presence of spiral structure.Comment: Accepted to ApJ, 48 pages and 20 figure
Big Data e monitoramento agroambiental.
O objetivo do trabalho foi criar uma estrutura para processamento de vários índices de vegetação para o sensor RapidEye, na qual qualquer operador possa escolher o índice por meio de sua aplicação e obter a geração automática para todo e qualquer município do Brasil de maneira relativamente automatizada
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