68 research outputs found
Stationary solutions for the parity-even sector of the CPT-even and Lorentz-covariance-violating term of the standard model extension
In this work, we focus on some properties of the parity-even sector of the
CPT-even electrodynamics of the standard model extension. We analyze how the
six non-birefringent terms belonging to this sector modify the static and
stationary classical solutions of the usual Maxwell theory. We observe that the
parity-even terms do not couple the electric and magnetic sectors (at least in
the stationary regime). The Green's method is used to obtain solutions for the
field strengths E and B at first order in the Lorentz- covariance-violating
parameters. Explicit solutions are attained for point-like and spatially
extended sources, for which a dipolar expansion is achieved. Finally, it is
presented an Earth-based experiment that can lead (in principle) to an upper
bound on the anisotropic coefficients as stringent as
Comment: 8 pages, revtex style, revised published version, to appear in EPJC
(2009
Trans-sialidase from Trypanosoma cruzi enhances the adhesion properties and fibronectin-driven migration of thymocytes
In experimental Trypanosoma cruzi infections, severe thymic atrophy leads to release of activated CD4+CD8+ double-positive (DP) T cells to the periphery. In humans, activated DP T cells are found in the blood in association with severe cardiac forms of human chronic Chagas disease. The mechanisms underlying the premature thymocyte release during the chagasic thymic atrophy remain elusive. We tested whether the migratory properties of intrathymic thymocytes are modulated by the parasite trans-sialidase (TS). We found that TS affected the dynamics of thymocytes undergoing intrathymic maturation, and these changes were accompanied by an increase in the number of recent DP thymic emigrants in the peripheral lymphoid organs. We demonstrated that increased percentages of blood DP T cell subsets were associated with augmented antibody titers against TS in chagasic patients with chronic cardiomyopathy. In vitro studies showed that TS was able to activate the MAPK pathway and actin filament mobilization in thymocytes. These effects were correlated with its ability to modulate the adhesion of thymocytes to thymic epithelial cells and their migration toward extracellular matrix. These findings point to effects of TS that could influence the escape of immature thymocytes in Chagas disease.Fil: Nardy, Ana FlĂĄvia F.R.. Universidade Federal do Rio de Janeiro; BrasilFil: Silva Filho, Joao Luiz da. Universidade Federal do Rio de Janeiro; BrasilFil: Perez, Ana Rosa. Universidad Nacional de Rosario. Facultad de Ciencias MĂ©dicas. Instituto de InmunologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Meis, Juliana de. Instituto Oswaldo Cruz; BrasilFil: Farias de Oliveira, DĂ©sio AurĂ©lio. Instituto Oswaldo Cruz; BrasilFil: Penha, Luciana. Universidade Federal do Rio de Janeiro; BrasilFil: Oliveira, Isadora de AraĂșjo. Universidade Federal do Rio de Janeiro; BrasilFil: Dias, Wagner B.. Universidade Federal do Rio de Janeiro; BrasilFil: Todeschini, Adriane. Universidade Federal do Rio de Janeiro; BrasilFil: Freire de Lima, CĂ©lio Geraldo. Universidade Federal do Rio de Janeiro; BrasilFil: Bellio, Maria. Universidade Federal do Rio de Janeiro; BrasilFil: Caruso Neves, Celso. Universidade Federal do Rio de Janeiro; BrasilFil: Pinheiro, Ana AcĂĄcia. Universidade Federal do Rio de Janeiro; BrasilFil: Takiya, Christina Maeda. Universidade Federal do Rio de Janeiro; BrasilFil: Bottasso, Oscar Adelmo. Universidad Nacional de Rosario. Facultad de Ciencias MĂ©dicas. Instituto de InmunologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Savino, Wilson. Instituto Oswaldo Cruz; BrasilFil: Morrot, Alexandre. Universidade Federal do Rio de Janeiro; Brasi
Planck early results XVIII : The power spectrum of cosmic infrared background anisotropies
Peer reviewe
Planck Early Results XVIII: The power spectrum of cosmic infrared background anisotropies
Using Planck maps of six regions of low Galactic dust emission with a total area of about 140 deg2, we determine the angular power spectra of
cosmic infrared background (CIB) anisotropies from multipole â = 200 to â = 2000 at 217, 353, 545 and 857 GHz. We use 21-cm observations of
Hi as a tracer of thermal dust emission to reduce the already low level of Galactic dust emission and use the 143 GHz Planck maps in these fields
to clean out cosmic microwave background anisotropies. Both of these cleaning processes are necessary to avoid significant contamination of the
CIB signal. We measure correlated CIB structure across frequencies. As expected, the correlation decreases with increasing frequency separation,
because the contribution of high-redshift galaxies to CIB anisotropies increases with wavelengths. We find no significant difference between the
frequency spectrum of the CIB anisotropies and the CIB mean, with âI/I=15% from 217 to 857 GHz. In terms of clustering properties, the
Planck data alone rule out the linear scale- and redshift-independent bias model. Non-linear corrections are significant. Consequently, we develop
an alternative model that couples a dusty galaxy, parametric evolution model with a simple halo-model approach. It provides an excellent fit to
the measured anisotropy angular power spectra and suggests that a different halo occupation distribution is required at each frequency, which
is consistent with our expectation that each frequency is dominated by contributions from different redshifts. In our best-fit model, half of the
anisotropy power at â=2000 comes from redshifts z 2 at 353
and 217 GHz, respectively
Planck early results XXIV : Dust in the diffuse interstellar medium and the Galactic halo
Peer reviewe
NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics
Xenarthrans â anteaters, sloths, and armadillos â have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset
- âŠ