1,336 research outputs found
Spin 1 fields in Riemann-Cartan space-times "via" Duffin-Kemmer-Petiau theory
We consider massive spin 1 fields, in Riemann-Cartan space-times, described
by Duffin-Kemmer-Petiau theory. We show that this approach induces a coupling
between the spin 1 field and the space-time torsion which breaks the usual
equivalence with the Proca theory, but that such equivalence is preserved in
the context of the Teleparallel Equivalent of General Relativity.Comment: 8 pages, no figures, revtex. Dedicated to Professor Gerhard Wilhelm
Bund on the occasion of his 70th birthday. To appear in Gen. Rel. Grav.
Equations numbering corrected. References update
Biodegradable nanoparticles containing benzopsoralens : an attractive strategy for modifying vascular function in pathological skin disorders
Psoralens are often used to treat skin disorders such as psoriasis, vitiligo and others. The toxicity and fast degradation of these drugs can be diminished by encapsulation in drug delivery systems (DDS). Nanoparticles (NPs) containing the benzopsoralen (BP) (3-ethoxy carbonyl-2H-benzofuro[3,2-e]-1-benzopiran-2-one) were prepared by the solvent evaporation technique, and parameters such as particle size, zeta potential, drug encapsulation efficiency, and external morphology were evaluated. The analysis revealed that the NPs are spherical and possessed a smooth external surface with diameter of 815 ± 80 nm, they present low tendency toward aggregation, as confirmed by their zeta potential (+17.3±2.9 mV) and the encapsulation efficiency obtained was 74%. The intracellular distribution of NPs as well as their uptake by tissues was monitored by using laser confocal microscopy and transmission electron microscopy. The use of benzopsoralen in association with ultraviolet light (360 nm) revealed morphological characteristics of cell damage such as cytosolic vesiculation, mitochondria condensation, and swelling of both the granular endoplasmic reticulum and the nuclear membrane. The primary target of DDS and drugs in vascular system are endothelial cells and an attractive strategy for modifying vascular function in various pathological states of skin disorders, cancer and inflammation. The result presented in this work indicates that PLGA NP could be a promising delivery system for benzopsoralen in connection with ultraviolet irradiation therapy (PUVA) for further application in different therapies.CNPq , CAPES, FAPESP (Braisl
Do firms share the same functional form of their growth rate distribution? A new statistical test
We introduce a new statistical test of the hypothesis that a balanced panel
of firms have the same growth rate distribution or, more generally, that they
share the same functional form of growth rate distribution. We applied the test
to European Union and US publicly quoted manufacturing firms data, considering
functional forms belonging to the Subbotin family of distributions. While our
hypotheses are rejected for the vast majority of sets at the sector level, we
cannot rejected them at the subsector level, indicating that homogenous panels
of firms could be described by a common functional form of growth rate
distribution.Comment: 17 pages, 3 figures, 2 table
Effects due to a scalar coupling on the particle-antiparticle production in the Duffin-Kemmer-Petiau theory
The Duffin-Kemmer-Petiau formalism with vector and scalar potentials is used
to point out a few misconceptions diffused in the literature. It is explicitly
shown that the scalar coupling makes the DKP formalism not equivalent to the
Klein-Gordon formalism or to the Proca formalism, and that the spin-1 sector of
the DKP theory looks formally like the spin-0 sector. With proper boundary
conditions, scattering of massive bosons in an arbitrary mixed vector-scalar
square step potential is explored in a simple way and effects due to the scalar
coupling on the particle-antiparticle production and localization of bosons are
analyzed in some detail
Profile of porcine respiratory disease complex associated with Pasteurella multocida in Minas Gerais state, Brazil.
Projeto/Plano de Ação: 02.10.61600-01
Exact Solution of Photon Equation in Stationary G\"{o}del-type and G\"{o}del Space-Times
In this work the photon equation (massless Duffin-Kemmer-Petiau equation) is
written expilicitly for general type of stationary G\"{o}del space-times and is
solved exactly for G\"{o}del-type and G\"{o}del space-times. Harmonic
oscillator behaviour of the solutions is discussed and energy spectrum of
photon is obtained.Comment: 9 pages,RevTeX, no figure, revised for publicatio
Twisted and Nontwisted Bifurcations Induced by Diffusion
We discuss a diffusively perturbed predator-prey system. Freedman and
Wolkowicz showed that the corresponding ODE can have a periodic solution that
bifurcates from a homoclinic loop. When the diffusion coefficients are large,
this solution represents a stable, spatially homogeneous time-periodic solution
of the PDE. We show that when the diffusion coefficients become small, the
spatially homogeneous periodic solution becomes unstable and bifurcates into
spatially nonhomogeneous periodic solutions.
The nature of the bifurcation is determined by the twistedness of an
equilibrium/homoclinic bifurcation that occurs as the diffusion coefficients
decrease. In the nontwisted case two spatially nonhomogeneous simple periodic
solutions of equal period are generated, while in the twisted case a unique
spatially nonhomogeneous double periodic solution is generated through
period-doubling.
Key Words: Reaction-diffusion equations; predator-prey systems; homoclinic
bifurcations; periodic solutions.Comment: 42 pages in a tar.gz file. Use ``latex2e twisted.tex'' on the tex
files. Hard copy of figures available on request from
[email protected]
Chlorambucil encapsulation into PLGA nanoparticles and cytotoxic effects in breast cancer cell.
HodgeRank as a new tool to explore the structure of a social representation
Social representation theory is a branch of social psychology that aims to identify the framework of concepts, ideas, opinions, beliefs, or feelings shared by the individuals within a social group, regarding a social object. Two main problems arise in this theory. The first concerns the identification of the content of the representation, which is the set of cognitive elements shared by the group; the second concerns its structure, which is the way these elements are organized and related among themselves. It is desirable that the methods to address these problems be simple, in regards to the feasibility of the data collection, and reliable, in the sense that they should provide a clear picture of the content and the structure of the representation. No single method proposed in the literature until now fully satisfies these features at the same time. Here we propose the use of HodgeRank, a global ranking method based on the Hodge combinatorial theory, as a new tool to explore the structure of a social representation. In this proposal, the input data is the same as those required for the hierarchical word associations, which is the main method in the field of social representations. However, the HodgeRank provides richer results when compared to the usual approach to analysing this kind of data, based on the VergĂ©sâ double-entry table. The main outcome of the HodgeRank is a graph, analogous to an electric circuit, from which some structural elements of the representation can already be identified. Moreover, the HodgeRank technique identifies the sources of inconsistencies between the global ranking and the aggregated answers within the social group. We interpret such inconsistencies in terms of the stability of the representation and use them to raise conjectures about the potential dynamics of the representation. We illustrate the application of this method in the study of a social representation of COVID-19 within a group of students and also within a group of faculty members from higher education institutions in Brazil
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