19,733 research outputs found
The young massive stellar cluster associated to RCW121
We report NIR broad and narrow band photometric observations in the direction
of the IRAS17149-3916 source that reveal the presence of a young cluster of
massive stars embedded in an HII region coincident with RCW121. These
observations, together with published radio data, MSX and Spitzer images were
used to determine some of the physical parameters of the region. We found 96
cluster member candidates in an area of about 1.5 x 2.0 square arcmin, 30% of
them showing excess emission in the NIR. IRS 1, the strongest source in the
cluster with an estimated spectral type of O5V-O6V ZAMS based on the
color-magnitude diagram, is probably the main ionizing source of the HII region
detected at radio wavelengths. Using the integrated Brgamma and the 5 GHz flux
densities, we derived a mean visual extinction AV=5.49 magnitudes. From the
observed size of the Brgamma extended emission, we calculated the emission
measure E and the electron density ne, characteristic of compact HII regions.Comment: 18 pages, 8 figures, accepted for publication on AJ (February/2006
Dormência em sementes de hortaliças.
A presente revisão de literatura objetivou os fatores que induzem a dormência, as categorias e mecanismos de dormência, assim como, métodos para superar a dormência em sementes de hortaliças.bitstream/item/72481/1/doc-1361.pd
Peletização de sementes de hortaliças.
A presente revisão de literatura objetivou divulgar a técnica de peletização de sementes de hortaliças desenvolvida pela Embrapa Hortaliças, para melhorara a semeadura e/ou o desenvolvimento ou sobrevivência de espécies cultivads, a fim de reduzir os custos com as operações de transplante.bitstream/item/72475/1/doc-1371.pd
Avaliação de doenças da mangueira.
A região semi-árida do Vale do Submédio São Francisco é responsável por mais de 90% do volume de manga exportado pelo Brasil. esta região a produtividade é elevada devido a características climáticas favoráveis e ao manejo fitotécnico intenso. No entanto, a intensificação do cultivo e algumas práticas de manejo vêm gerando ou agravando problemas fitossanitários, com conseqüente aumento de perdas de produção. As doenças que ocorrem na mangueira resultam em perdas quantitativas, ou seja, menor número de frutos formado, mas principalmente perdas qualitativas (redução no tamanho e apodrecimento de frutos). Este tipo de perda pode prejudicar o trânsito internacional da manga desta região.bitstream/item/133830/1/ID-31564.pdfApostila distribuida aos participantes do Curso de Avaliação de Doenças da Mangueira, Petrolina, maio 2005
The true nature of the alleged planetary nebula W16-185
We report the discovery of a small cluster of massive stars embedded in a NIR
nebula in the direction of the IRAS15411-5352 point source, which is related to
the alleged planetary nebula W16-185. The majority of the stars present large
NIR excess characteristic of young stellar objects and have bright counterparts
in the Spitzer IRAC images; the most luminous star (IRS1) is the NIR
counterpart of the IRAS source. We found very strong unresolved Brgamma
emission at the IRS1 position and more diluted and extended emission across the
continuum nebula. From the sizes and electron volume densities we concluded
that they represent ultra-compact and compact HII regions, respectively.
Comparing the Brgamma emission with the 7 mm free-free emission, we estimated
that the visual extinction ranges between 14 and 20 mag. We found that only one
star (IRS1) can provide the number of UV photons necessary to ionize the
nebula.Comment: 30 pages, 15 figures, 2 tables V3: minor grammatical changes. Figure
4 is available in pdf file. Accepted for publication in AJ, April / 200
Nambu monopoles interacting with lattice defects in two-dimensional artificial square spin ice
The interactions between an excitation (similar to a pair of Nambu monopoles)
and a lattice defect are studied in an artificial two-dimensional square spin
ice. This is done by considering a square array of islands containing only one
island different from all others. This difference is incorporated in the
magnetic moment (spin) of the "imperfect" island and several cases are studied,
including the special situation in which this distinct spin is zero (vacancy).
We have shown that the two extreme points of a malformed island behave like two
opposite magnetic charges. Then, the effective interaction between a pair of
Nambu monopoles with the deformed island is a problem involving four magnetic
charges (two pairs of opposite poles) and a string. We also sketch the
configuration of the field lines of these four charges to confirm this picture.
The influence of the string on this interaction decays rapidly with the string
distance from the defect.Comment: 7 pages, 13 figure
- …