922 research outputs found
Quantização de Laços no Modelo BF 2+1 Dimensional com Campos de Matéria.
O objetivo deste trabalho Ă© explorar as simetrias e desenvolver a dinâmica associada a um modelo do tipo BF com campos escalares acoplados, tanto a nĂvel clássico quanto a nĂvel quântico. Para tal, desenvolvem-se ferramentas matemáticas apropriadas para se tratar
em geral uma teoria de calibre topológica do tipo Yang-Mills, para formular uma ação covariante e estudar suas simetrias via o método de quantização canônica de Dirac, também conhecido como método hamiltoniano vinculado. Este método é desenvolvido extensamente
para os casos abeliano e não-abeliano do nosso modelo, e em seguida quantiza-se o caso abeliano via laços para analisar o desenvolvimento da mecânica quântica nestas teorias
de calibre descrevendo a base para nossos funcionais de estado, chamada de rede de
cargas, bem como o c´alculo de alguns observ´aveis associados a nossos estados cinem´aticos
e f´ısicos
Desempenho Produtivo de Ovinos Barriga Negra em Roraima: 2017/2018.
bitstream/item/199615/1/COT-86-Barriga-negra.pd
Regolith behavior under asteroid-level gravity conditions: Low-velocity impacts into mm- and cm-sized grain targets
In situ observations of small asteroids show that surfaces covered by
boulders and coarse terrain are frequent on such bodies. Regolith grain sizes
have distributions on approximately mm and cm scales, and the behavior of such
large grains in the very low-gravity environments of small body surfaces
dictates their morphology and evolution. In order to support the understanding
of natural processes (e.g., the recapturing of impact ejecta) or
spacecraft-induced interactions (e.g., the fate of a small lander), we aim to
experimentally investigate the response of coarse-grained target surfaces to
very-low-speed impacts (below 2 m/s). We present the outcome of 86 low-speed
impacts of a cm-sized spherical projectile into a bed of simulated regolith,
composed of irregular mm- and cm-sized grains. These impacts were performed
under vacuum and microgravity conditions. Our results include measurements for
the projectile coefficient of restitution and penetration depth, as well as
ejecta production, speed, and mass estimation. We find that impact outcomes
include the frequent occurrence of projectile bouncing and tangential rolling
on the target surface upon impact. Ejecta is produced for impact speeds higher
than about 12 cm/s, and ejecta speeds scale with the projectile to target the
grain size ratio and the impact speed. Ejected mass estimations indicate that
ejecta is increasingly difficult to produce for increasing grain sizes.
Coefficients of restitution of rebounding projectiles do not display a
dependency on the target grain size, unlike their maximum penetration depth,
which can be scaled with the projectile to target grain size ratio. Finally, we
compare our experimental measurements to spacecraft data and numerical work on
Hayabusa 2's MASCOT landing on the surface of the asteroid Ryugu
Nonlinear electrodynamics and the Pioneer 10/11 spacecraft anomaly
The occurrence of the phenomenon known as photon acceleration is a natural
prediction of nonlinear electrodynamics (NLED). This would appear as an
anomalous frequency shift in any modeling of the electromagnetic field that
only takes into account the classical Maxwell theory. Thus, it is tempting to
address the unresolved anomalous, steady; but time-dependent, blueshift of the
Pioneer 10/11 spacecrafts within the framework of NLED. Here we show that
astrophysical data on the strength of the magnetic field in both the Galaxy and
the local (super)cluster of galaxies support the view on the major Pioneer
anomaly as a consequence of the phenomenon of photon acceleration. If
confirmed, through further observations or lab experiments, the reality of this
phenomenon should prompt to take it into account in any forthcoming research on
both cosmological evolution and origin and dynamical effects of primordial
magnetic fields, whose seeds are estimated to be very weak.Comment: Final version accepted for publication in Europhysics Letters, uses
EPL style, 7 page
Wheat cultivation: Identification and estimation of areas using LANDSAT data
The feasibility of using automatically processed multispectral data obtained from LANDSAT to identify wheat and estimate the areas planted with this grain was investigated. Three 20 km by 40 km segments in a wheat growing region of Rio Grande do Sul were aerially photographed using type 2443 Aerochrome film. Three maps corresponding to each segment were obtained from the analysis of the photographs which identified wheat, barley, fallow land, prepared soil, forests, and reforested land. Using basic information about the fields and maps made from the photographed areas, an automatic classification of wheat was made using MSS data from two different periods: July to September and July to October 1979. Results show that orbital data is not only useful in characterizing the growth of wheat, but also provides information of the intensity and extent of adverse climate which affects cultivation. The temporal and spatial characteristics of LANDSAR data are also demonstrated
The challenge of early diagnosis of autoimmune lymphoproliferative syndrome in children with suspected autoinflammatory/autoimmune disorders
OBJECTIVES: To test the usefulness of an extended panel of lymphocyte subsets in combination with Oliveira's diagnostic criteria for the identification of autoimmune lymphoproliferative syndrome (ALPS) in children referred to a paediatric rheumatology centre. METHODS: Patients referred from 2015 to 2018 to our rheumatology unit for an autoimmune or autoinflammatory condition were retrospectively analysed. Oliveira's required criteria [chronic lymphoproliferation and elevated double-negative T (DNT)] were applied as first screening. Flow cytometry study included double-negative CD4-CD8-TCR\u3b1\u3b2+ T lymphocytes (DNT), CD25+CD3+, HLA-DR+CD3+ T cells, B220+ T cells and CD27+ B cells. Data were analysed with a univariate logistic regression analysis, followed by a multivariate analysis. Sensitivity and specificity of the Oliveira's required criteria were calculated. RESULTS: A total of 264 patients were included in the study and classified as: (i) autoimmune diseases (n\u2009=\u200926); (ii) juvenile idiopathic arthritis (JIA) (35); (iii) monogenic systemic autoinflammatory disease (27); (iv) periodic fever, aphthous stomatitis, pharyngitis and adenitis syndrome (100); (v) systemic undefined recurrent fever (45); (vi) undetermined-systemic autoinflammatory disease (14); or (vii) ALPS (17). Oliveira's required criteria displayed a sensitivity of 100% and specificity of 79%. When compared with other diseases the TCR\u3b1\u3b2+B220+ lymphocytes were significantly increased in ALPS patients. The multivariate analysis revealed five clinical/laboratory parameters positively associated to ALPS: splenomegaly, female gender, arthralgia, elevated DNT and TCR\u3b1\u3b2+B220+ lymphocytes. CONCLUSIONS: Oliveira's required criteria are useful for the early suspicion of ALPS. TCR\u3b1\u3b2+B220+ lymphocytes should be added in the diagnostic work-up of patients referred to the paediatric rheumatology unit for a suspected autoimmune or autoinflammatory condition, providing a relevant support in the early diagnosis of ALPS
Photon frequency conversion induced by gravitational radiation
We consider propagation of gravitational radiation in a magnetized
multicomponent plasma. It is shown that large density perturbations can be
generated, even for small deviations from flat space, provided the cyclotron
frequency is much larger than the plasma frequency. Furthermore, the induced
density gradients can generate frequency conversion of electromagnetic
radiation, which may give rise to indirect observational effect of the
gravitational waves.Comment: 13 pages, 1 figure, uses revtex, Accepted for publication in Phys.
Rev. D, Revised, appendix adde
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