1,684 research outputs found

    Renormalizability of generalized quantum electrodynamics

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    In this work we present the study of the renormalizability of the Generalized Quantum Electrodynamics (GQED4GQED_{4}). We begin the article by reviewing the on-shell renormalization scheme applied to GQED4GQED_{4}. Thereafter, we calculate the explicit expressions for all the counter-terms at one-loop approximation and discuss the infrared behavior of the theory as well. Next, we explore some properties of the effective coupling of the theory which would give an indictment of the validity regime of theory: m2≤k2<mP2m^{2} \leq k^{2} < m_{P}^{2}. Afterwards, we make use of experimental data from the electron anomalous magnetic moment to set possible values for the theory free parameter through the one-loop contribution of Podolsky mass-dependent term to Pauli's form factor F2(q2)F_{2}(q^{2}).Comment: 9 page

    Biofuels and Rural Economic Development in Latin America and the Caribbean

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    Biofuel expansion is seen as a way to reduce dependence on fossil fuels, as an alternative energy source for transportation and other uses, as a way to reduce Green House Gases, and as way to revitalize the agricultural sector. Very little discussions have been focused on Latin America, except for Brazil. Potential negative impacts re-enforce the need of performing more in depth analysis of the potential impact of biofuels expansion in Latin America and the Caribbean (LAC). Paper estimates biofuels production potential based on current production situation and develops a forward-looking analysis of the long-term impact of biofuels expansion in Latin America and its effects on prices, trade, food security, malnutrition and other indicators using the IMPACT-WATER model developed by IFPRI. The analysis conducted for this paper of potential crops in the region show that from a technical and productivity standpoint in which to base biofuels expansion continues to be sugarcane and palm oil trees. Most countries in Latin America will not have a production constraint in terms of meeting existing and projected mandatory blends requirements. However, if the goal is to obtain energy independence, this result only holds for a few countries, with obvious food security implications as countries dedicate higher shares of their agricultural land to biofuels expansion. Our analysis, and those made in other studies, show that biofuels expansion is not likely to have a binding land production constraint in Latin America, with a few exceptions. The forward-looking estimations from the IMPACT-WATER model show that Brazil will continue to be the major player in the ethanol market. Brazil will expand its ethanol exports to meet growing demand in other countries including some in Latin America. Other countries such as Argentina and Colombia will likely continue their biofuels expansion plans, although our estimate show that they will not likely meet their demand based on current production potential. The IMPACT-WATER simulations also show that biofuels impacts on food security and malnutrition will likely happen in those countries where the feedstock used for biofuels production is a critical component of a major share of the population, other things equal. An example of this potential is Mexico and most of the Central America region, where a high proportion of the diet is composed of maize. The extent to which biofuels efforts can contribute towards addressing or affecting all broader contextual issues depend on a series of strategic determinants of impact success, ranging from the characteristics of installed capacity and industrial organization and coordination to whether any nascent market for biofuels will be economically sustainable and financially viable without continuous government support or interventions.Community/Rural/Urban Development, Resource /Energy Economics and Policy,

    Quantifying offshore fore-arc deformation and splay-fault slip using drowned Pleistocene shorelines, Arauco Bay, Chile

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    Indexación: Web of Science; Scopus.Most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial timescales. Here we study millennial deformation associated with an active splay-fault system in the Arauco Bay area off south central Chile. We describe hitherto unrecognized drowned shorelines using high-resolution multibeam bathymetry, geomorphic, sedimentologic, and paleontologic observations and quantify uplift rates using a Landscape Evolution Model. Along a margin-normal profile, uplift rates are 1.3 m/ka near the edge of the continental shelf, 1.5 m/ka at the emerged Santa María Island, −0.1 m/ka at the center of the Arauco Bay, and 0.3 m/ka in the mainland. The bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal-scale Santa María splay-fault system. We modeled surface deformation using two different structural scenarios: deep-reaching normal faults and deep-reaching reverse faults with shallow extensional structures. Our preferred model comprises a blind reverse fault extending from 3 km depth down to the plate interface at 16 km that slips at a rate between 3.0 and 3.7 m/ka. If all the splay-fault slip occurs during every great megathrust earthquake, with a recurrence of ~150–200 years, the fault would slip ~0.5 m per event, equivalent to a magnitude ~6.4 earthquake. However, if the splay-fault slips only with a megathrust earthquake every ~1000 years, the fault would slip ~3.7 m per event, equivalent to a magnitude ~7.5 earthquake. ©2017. American Geophysical Union.http://onlinelibrary.wiley.com/doi/10.1002/2016JB013339/epd

    Semiclassical theory for small displacements

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    Characteristic functions contain complete information about all the moments of a classical distribution and the same holds for the Fourier transform of the Wigner function: a quantum characteristic function, or the chord function. However, knowledge of a finite number of moments does not allow for accurate determination of the chord function. For pure states this provides the overlap of the state with all its possible rigid translations (or displacements). We here present a semiclassical approximation of the chord function for large Bohr-quantized states, which is accurate right up to a caustic, beyond which the chord function becomes evanescent. It is verified to pick out blind spots, which are displacements for zero overlaps. These occur even for translations within a Planck area of the origin. We derive a simple approximation for the closest blind spots, depending on the Schroedinger covariance matrix, which is verified for Bohr-quantized states.Comment: 16 pages, 4 figures

    The canonical structure of Podolsky's generalized electrodynamics on the Null-Plane

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    In this work we will develop the canonical structure of Podolsky's generalized electrodynamics on the null-plane. This theory has second-order derivatives in the Lagrangian function and requires a closer study for the definition of the momenta and canonical Hamiltonian of the system. On the null-plane the field equations also demand a different analysis of the initial-boundary value problem and proper conditions must be chosen on the null-planes. We will show that the constraint structure, based on Dirac formalism, presents a set of second-class constraints, which are exclusive of the analysis on the null-plane, and an expected set of first-class constraints that are generators of a U(1) group of gauge transformations. An inspection on the field equations will lead us to the generalized radiation gauge on the null-plane, and Dirac Brackets will be introduced considering the problem of uniqueness of these brackets under the chosen initial-boundary condition of the theory

    Interleukin-3 prevents neuronal death induced by amyloid peptide

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    <p>Abstract</p> <p>Background</p> <p>Interleukin-3 (IL-3) is an important glycoprotein involved in regulating biological responses such as cell proliferation, survival and differentiation. Its effects are mediated via interaction with cell surface receptors. Several studies have demonstrated the expression of IL-3 in neurons and astrocytes of the hippocampus and cortices in normal mouse brain, suggesting a physiological role of IL-3 in the central nervous system. Although there is evidence indicating that IL-3 is expressed in some neuronal populations, its physiological role in these cells is poorly known.</p> <p>Results</p> <p>In this study, we demonstrated the expression of IL-3 receptor in cortical neurons, and analyzed its influence on amyloid β (Aβ)-treated cells. In these cells, IL-3 can activate at least three classical signalling pathways, Jak/STAT, Ras/MAP kinase and the PI 3-kinase. Viability assays indicated that IL-3 might play a neuroprotective role in cells treated with Aβ fibrils. It is of interest to note that our results suggest that cell survival induced by IL-3 required PI 3-kinase and Jak/STAT pathway activation, but not MAP kinase. In addition, IL-3 induced an increase of the anti-apoptotic protein Bcl-2.</p> <p>Conclusion</p> <p>Altogether these data strongly suggest that IL-3 neuroprotects neuronal cells against neurodegenerative agents like Aβ.</p

    p-adic Cellular Neural Networks

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    In this article we introduce the p-adic cellular neural networks which are mathematical generalizations of the classical cellular neural networks (CNNs) introduced by Chua and Yang. The new networks have infinitely many cells which are organized hierarchically in rooted trees, and also they have infinitely many hidden layers. Intuitively, the p-adic CNNs occur as limits of large hierarchical discrete CNNs. More precisely, the new networks can be very well approximated by hierarchical discrete CNNs. Mathematically speaking, each of the new networks is modeled by one integro-differential equation depending on several p-adic spatial variables and the time. We study the Cauchy problem associated to these integro-differential equations and also provide numerical methods for solving them

    p-adic cellular neural networks: Applications to image processing

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    The p-adic cellular neural networks (CNNs) are mathematical generalizations of the neural networks introduced by Chua and Yang in the 80s. In this work we present two new types of -adic CNNs that can perform computations with real data, and whose dynamics can be understood almost completely. The first type of networks are edge detectors for grayscale images. The stationary states of these networks are organized hierarchically in a lattice structure. The dynamics of any of these networks consists of transitions toward some minimal state in the lattice. The second type is a new class of reaction–diffusion networks. We investigate the stability of these networks and show that they can be used as filters to reduce noise, preserving the edges, in grayscale images polluted with additive Gaussian noise. The networks introduced here were found experimentally. They are abstract evolution equations on spaces of real-valued functions defined in the p-adic unit ball for some prime number p. In practical applications the prime p is determined by the size of image, and thus, only small primes are used. We provide several numerical simulations showing how these networks work
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