2,557 research outputs found
The Electron Temperature Gradient in the Galactic Disk
We derive the electron temperature gradient in the Galactic disk using a
sample of HII regions that spans Galactocentric distances 0--17 kpc. The
electron temperature was calculated using high precision radio recombination
line and continuum observations for more than 100 HII regions. Nebular
Galactocentric distances were calculated in a consistent manner using the
radial velocities measured by our radio recombination line survey. The large
number of nebulae widely distributed over the Galactic disk together with the
uniformity of our data provide a secure estimate of the present electron
temperature gradient in the Milky Way. Because metals are the main coolants in
the photoionized gas, the electron temperature along the Galactic disk should
be directly related to the distribution of heavy elements in the Milky Way. Our
best estimate of the electron temperature gradient is derived from a sample of
76 sources for which we have the highest quality data. The present gradient in
electron temperature has a minimum at the Galactic Center and rises at a rate
of 287 +/- 46 K/kpc. There are no significant variations in the value of the
gradient as a function of Galactocentric radius or azimuth. The scatter we find
in the HII region electron temperatures at a given Galactocentric radius is not
due to observational error, but rather to intrinsic fluctuations in these
temperatures which are almost certainly due to fluctuations in the nebular
heavy element abundances. Comparing the HII region gradient with the much
steeper gradient found for planetary nebulae suggests that the electron
temperature gradient evolves with time, becoming flatter as a consequence of
the chemical evolution of the Milky Way's disk.Comment: 43 pages, 9 figures (accepted for publication in the ApJ
NON-DARCY FLOW EVALUATION OF UNCONSOLIDATED POROUS MEDIA IN A CLOSED LOOP PERMEAMETER
A new closed loop permeameter was implemented in this work to study the fluid flow through two different unconsolidated porous media. An apparent permeability, similar to that proposed by Barree and Conway, was described in this work in terms of the absolute permeability combined with a new fluid property description, the inertial contribution factor that accounts for the domain of viscous and inertial forces. Such approach discriminate those properties of the rock as intrinsic permeability from those related to the fluid as the inertial contribution factor. The apparent permeability equation of Barree and Conway was applied to different intervals of the experimental data in which it was possible to obtain the Forchheimer coefficients as well as the inertial contribution factors according to each interval. Two different types of unconsolidated porous media materials were utilized in the new Closed Loop Permeameter, sand (1-2 mm) and glass spheres (3.96 mm). The equation of Barree and Conway provided a great agreement fitting the experimental data in a wide non-Darcy Reynolds number range. It was observed an increase in the Forchheimer coefficient and decrease in the apparent permeability with the flow rate increase. The results indicate a correlation between the permeability and the inertial effects in the non-Darcy turbulent regions in which the porous media materials with low permeability values are probably more subjected to flow losses due to the inertial effects
Mutations Of Androgen Receptor Gene In Brazilian Patients With Male Pseudohermaphroditism.
We describe the identification of point mutations in the androgen receptor gene in five Brazilian patients with female assignment and behavior. The eight exons of the gene were amplified by the polymerase chain reaction (PCR) and analyzed for single-strand conformation polymorphism (SSCP) to detect the mutations. Direct sequencing of the mutant PCR products demonstrated single transitions in three of these cases: G-->A in case 1, within exon C, changing codon 615 from Arg to His; G-->A in case 2, within exon E, changing codon 752 from Arg to Gln, and C-->T in case 3, within exon B, but without amino acid change.31775-
Associação de virulência em linhagens Elites de sorgo a nove raças de Peronosclerospora sorghi e previsão de resistência de seus híbridos.
Analysis of flight parameters and georeferencing of images with different control points obtained by RPA
ArticleNew techniques for analysing the earth's surface have been explored, such as the use
of remotely piloted aircraft (RPA) to obtain aerial images. However, one of the obstacles of
photogrammetry is the reliability of the scenes, because in some cases, considerable geometric
errors are generated, thus necessitating adjustments. Some parameters used in these adjustments
are image overlaps and control points, which generate uncertainties about the amount and
arrangement of these points in an area. The aim of this study was to test the potential of a
commercial RPA for monitoring and its applicability in the management of and decision-making
about coffee crops with two different overlaps and to evaluate geometric errors by applying four
grids of georeferenced points. The study area is located in an experimental Arabica coffee
plantation measuring 0.65 ha. To capture the images, the flight altitude was standardized to a
30 m altitude from the ground, and a constant travel speed of 3 m s
-1 was used. The treatments
studied were two combinations of image overlap, namely, 80/80% and 70/60%. Six points were
tracked through Global Navigation Satellite System (GNSS) receivers and identified with signs,
followed by an RPA flight for image collection. The obtained results indicated distinct residual
error rates pointing to larger errors along Cartesian axis Y, demonstrating that the point
distribution directly affects the residual errors. The use of control points is necessary for image
adjustments, but to optimize their application, it is necessary to consider the shape of the area to
be studied and to distribute the points in a non-biased way relative to the coordinate axes. It is
concluded that the lower overlap can be recommended for use in the flight plan due to the high
resolution of the orthomosaic and the shorter processing time
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