400 research outputs found
Cognitive Vehicular Networks: An Overview
AbstractCognitive Radio (CR) is extending the applications of wireless communications worldwide. Cognitive radio verifies the electromagnetic spectrum availability and permits the modification of the transmission parameters using the interaction with the environment. The goal is to opportunistically occupy spectral bands with minimum interference to other users or applications. Cognitive radio for Vehicular Ad hoc Networks (CRVs or CR-VANETs) is a new trend in the automotive market. Recent and future vehicles will offer functionalities for the transmission of intra-vehicular commands and dynamic access to wireless services, while the car is in transit. This paper describes the cognitive radio technology and its signal processing perspectives for the automotive market
String-Loop Corrected Magnetic Black Holes
We discuss the form of the string-loop-corrected effective action obtained by
compactification of the heterotic string theory on the manifold
or on its orbifold limit and the loop-corrected magnetic black hole solutions
of the equations of motion. Effective 4D theory has N=2 local supersymmetry.
Using the string-loop-corrected prepotential of the N=2 supersymmetric theory,
which receives corrections only from the string world sheets of torus topology,
we calculate the loop corrections to the tree-level gauge couplings and solve
the loop-corrected equations of motion. At the string-tree level, the effective
gauge couplings decrease at small distances from the origin, and in this region
string-loop corrections to the gauge couplings become important. A possibility
of smearing the singularity of the tree-level supersymmetric solution with
partially broken supersymmetry by quantum corrections is discussed.Comment: Improved version. Mixing of the dilaton with other moduli properly
taken into account. Explanatory notes adde
Regularisation Techniques for the Radiative Corrections of Wilson lines and Kaluza-Klein states
Within an effective field theory framework we compute the most general
structure of the one-loop corrections to the 4D gauge couplings in one- and
two-dimensional orbifold compactifications with non-vanishing constant gauge
background (Wilson lines). Although such models are non-renormalisable, we keep
the analysis general by considering the one-loop corrections in three
regularisation schemes: dimensional regularisation (DR), Zeta-function
regularisation (ZR) and proper-time cut-off regularisation (PT). The relations
among the results obtained in these schemes are carefully addressed. With
minimal re-definitions of the parameters involved, the results obtained for the
radiative corrections can be applied to most orbifold compactifications with
one or two compact dimensions. The link with string theory is discussed. We
mention a possible implication for the gauge couplings unification in such
models.Comment: 37 pages, 1 Figure, LaTeX; minor correction
The alpha-prime stretched horizon in the Heterotic string
The linear alpha-prime corrections and the field redefinition ambiguities are
studied for half-BPS singular backgrounds representing a wrapped fundamental
string. It is showed that there exist schemes in which the inclusion of all the
linear alpha-prime corrections converts these singular solutions to black holes
with a regular horizon for which the modified Hawking-Bekenstein entropy is in
agreement with the statistical entropy.Comment: 22 pages JHEP; new discussions and more details added to section
Petrographic and geochemical characterization of the magmatic sequence of Seival Mine, Hilario Formation (Neoproterozoic Camaquã Basin), Rio Grande do Sul, Brazil
A Mina do Seival é constituída por rochas vulcânicas e diques de composição andesítica e traqui-andesítica, dispostas em duas sequências. A sequência I inclui rochas piroclásticas e efusivas, e a sequência II é representada pelos diques de composição andesítica. Ambas são incluídas na Associação Shoshonítica de Lavras do Sul. Este magmatismo é relacionado ao estágio pós-colisional do ciclo Brasiliano/Pan-Africano, situando-se estratigraficamente no Alogrupo Bom Jardim, pertencendo à Formação Hilário na Bacia do Camaquã (Neoproterozoico). A área possui intensa alteração hidrotermal e mineralizações de Cu. A mineralização e o magmatismo da Sequência II são controlados por estruturas tectônicas orientadas segundo N/NE e NO, que são relacionadas à distensão regional no período pós-colisional da Orogênese Brasiliano/Pan-Africana. Processos hidrotermais em diferentes temperaturas atuaram sobre estas rochas originando produtos de alteração pervasiva, principalmente clorita, corrensita e esmectita, com veios preenchidos por quartzo, carbonato, barita e minerais de cobre. Em ambas as sequências encaixantes da Mina do Seival é possível identificar a afinidade shoshonítica das rochas. Os elevados teores de Cu, Zn e Ni nos diques em relação às rochas piroclásticas e às efusivas, mesmo nas mais hidrotermalizadas, sugerem que as principais ocorrências de mineralização de Cu têm origem magmática. Os dados químicos de rocha total indicam que o enriquecimento dos elementos componentes da mineralização, Ag, Au, Cu e Zn, está relacionado aos diques da Sequência II. Os teores de Au e Cu são mais elevados nas amostras com menores concentrações de carbonatos, sugerindo que a carbonatação não tem relação com a deposição dos minérios.The Seival Mine consists of andesitic volcanic and trachy-andesitic volcanic and hipabissal rocks grouped into two volcanic sequences. The Sequence I is composed of pyroclastic rocks and effusive rocks, and sequence II by andesite dikes. The area shows intense hydrothermal alteration and Cu mineralization. This magmatism is related to the post-collisional stage of the cycle Brasiliano/Pan-African, and it is stratigraphically positioned in the Bom Jardim Allogroup, Hilário Formation, which is part of the Neoproterozoic Camaquã Basin. Sequence II magmatism and mineralization are controlled by tectonic structures with N/NE and NW orientation, which are related to regional extension during the post-collisional stage of Brasiliano/Pan-African Orogeny. Processes involving different temperatures caused pervasive alteration products, with generation of chlorite, corrensite and smectite, with veins filled by quartz, carbonate, barite and copper minerals. In both sequences of Seival Mine is possible to identify the shoshonitic affinity of host sequences, as pointed out by geochemical data. The higher contents of Cu, Zn, and Ni in andesite dikes in relation to pyroclastic and effusive rocks, even in the hydrothermally altered types, suggest that the main Cu mineralizations have magmatic origin. The Au and Cu contents are higher in samples with lower carbonate concentrations, which suggests than carbonate alteration have no relation with ore deposition
Systems Approach Reveals Nuclear Factor Erythroid 2-Related Factor 2/Protein Kinase R Crosstalk in Human Cutaneous Leishmaniasis
Leishmania parasites infect macrophages, causing a wide spectrum of human diseases, from cutaneous to visceral forms. In search of novel therapeutic targets, we performed comprehensive in vitro and ex vivo mapping of the signaling pathways upstream and downstream of antioxidant transcription factor [nuclear factor erythroid 2-related factor 2 (Nrf2)] in cutaneous leishmaniasis (CL), by combining functional assays in human and murine macrophages with a systems biology analysis of in situ (skin biopsies) CL patient samples. First, we show the PKR pathway controls the expression and activation of Nrf2 in Leishmania amazonensis infection in vitro. Nrf2 activation also required PI3K/Akt signaling and autophagy mechanisms. Nrf2- or PKR/Akt-deficient macrophages exhibited increased levels of ROS/RNS and reduced expression of Sod1 Nrf2-dependent gene and reduced parasite load. L. amazonensis counteracted the Nrf2 inhibitor Keap1 through the upregulation of p62 via PKR. This Nrf2/Keap1 observation was confirmed in situ in skin biopsies from Leishmania-infected patients. Next, we explored the ex vivo transcriptome in CL patients, as compared to healthy controls. We found the antioxidant response element/Nrf2 signaling pathway was significantly upregulated in CL, including downstream target p62. In silico enrichment analysis confirmed upstream signaling by interferon and PI3K/Akt, and validated our in vitro findings. Our integrated in vitro, ex vivo, and in silico approach establish Nrf2 as a central player in human cutaneous leishmaniasis and reveal Nrf2/PKR crosstalk and PI3K/Akt pathways as potential therapeutic targets
Quantum Attractor Flows
Motivated by the interpretation of the Ooguri-Strominger-Vafa conjecture as a
holographic correspondence in the mini-superspace approximation, we study the
radial quantization of stationary, spherically symmetric black holes in four
dimensions. A key ingredient is the classical equivalence between the radial
evolution equation and geodesic motion of a fiducial particle on the moduli
space M^*_3 of the three-dimensional theory after reduction along the time
direction. In the case of N=2 supergravity, M^*_3 is a para-quaternionic-Kahler
manifold; in this case, we show that BPS black holes correspond to a particular
class of geodesics which lift holomorphically to the twistor space Z of M^*_3,
and identify Z as the BPS phase space. We give a natural quantization of the
BPS phase space in terms of the sheaf cohomology of Z, and compute the exact
wave function of a BPS black hole with fixed electric and magnetic charges in
this framework. We comment on the relation to the topological string amplitude,
extensions to N>2 supergravity theories, and applications to automorphic black
hole partition functions.Comment: 43 pages, 6 figures; v2: typos and references added; v3: published
version, minor change
Elephant grass silage inoculated with cellulolytic fungi isolated from rumen
ABSTRACT The objective was to evaluate the inoculation with Aspergillus terreus and/or Trichoderma longibrachiatum on fermentation, chemical and microbiological composition of elephant grass ‘Cameroon’ silage (Cenchrus purpureus). Treatments were A. terreus at 105 colony forming units (CFU)/g (AT15), T. longibrachiatum at 105 CFU/g (TL20), a mixture of both at 105 CFU/g (MIX), and a control group without inoculation (CONTR). The design was completely randomized with seven replicates. The MIX silage was most stable, while CONTR, AT15, and TL20, had lower dry matter losses. There was no effect of inoculation in the chemical composition of silages. Only MIX silage (4.40) had pH above the minimum of 4.2 for humid grass silage and above the control (4.05). Bacteria from Diplococcus genus was identified at the opening of TL20 and CONTR silages. After air exposure, the population of rods, Lactobacillus, and total lactic acid bacteria was higher in theTL20 and MIX. The inclusion of a T. longibrachiatum and A. terreus mixture increases dry mater loss and silage pH. T. longibrachiatum was more efficient in maintaining populations of total lactic acid bacteria after opening; therefore, this strain has potential as an additive for elephant grass ‘Cameroon’ silage
The b--->s{\gamma} constraint in effective supergravities from string theory
We study the constraints from the decay in the
parameter space of effective supergravities from orbifold string theory and
with minimal supesymmetric particle content. Both the general dilaton-dominated
universal scenario as well as a non-universal scenario for the soft terms are
investigated. It is found that the recently reported CLEO upper and lower
bounds constrain the parameter space of the models under scrutiny. In
particular we find constraints on the values of the parameter and
the gluino masses. In this class of string scenarios the negative sign of the
Higgs mixing parameter , is phenomenologically preferred.Comment: LaTeX 11 pages, figures uuencoded included in a separate file, some
typos have been corrected,1 figure adde
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