11,577 research outputs found
Lattice calculations on the spectrum of Dirac and Dirac-K\"ahler operators
We present a matrix technique to obtain the spectrum and the analytical index
of some elliptic operators defined on compact Riemannian manifolds. The method
uses matrix representations of the derivative which yield exact values for the
derivative of a trigonometric polynomial. These matrices can be used to find
the exact spectrum of an elliptic operator in particular cases and in general,
to give insight into the properties of the solution of the spectral problem. As
examples, the analytical index and the eigenvalues of the Dirac operator on the
torus and on the sphere are obtained and as an application of this technique,
the spectrum of the Dirac-Kahler operator on the sphere is explored.Comment: 11 page
Stabilization of Extra Dimensions and The Dimensionality of the Observed Space
We present a simple model for the late time stabilization of extra
dimensions. The basic idea is that brane solutions wrapped around extra
dimensions, which is allowed by string theory, will resist expansion due to
their winding mode. The momentum modes in principle work in the opposite way.
It is this interplay that leads to dynamical stabilization. We use the idea of
democratic wrapping \cite{art5}-\cite{art6}, where in a given decimation of
extra dimensions, all possible winding cases are considered. To simplify the
study further we assumed a symmetric decimation in which the total number of
extra dimensions is taken to be where N can be called the order of the
decimation. We also assumed that extra dimensions all have the topology of
tori. We show that with these rather conservative assumptions, there exists
solutions to the field equations in which the extra dimensions are stabilized
and that the conditions do not depend on . This fact means that there exists
at least one solution to the asymmetric decimation case. If we denote the
number of observed space dimensions (excluding time) by , the condition for
stabilization is for pure Einstein gravity and for dilaton
gravity massaged by string theory parameters.Comment: Final versio
Phenomenological Analysis of and Elastic Scattering Data in the Impact Parameter Space
We use an almost model-independent analytical parameterization for and
elastic scattering data to analyze the eikonal, profile, and
inelastic overlap functions in the impact parameter space. Error propagation in
the fit parameters allows estimations of uncertainty regions, improving the
geometrical description of the hadron-hadron interaction. Several predictions
are shown and, in particular, the prediction for inelastic overlap
function at TeV shows the saturation of the Froissart-Martin
bound at LHC energies.Comment: 15 pages, 16 figure
Numerical understanding of regional scale water table behavior in the Guadalupe Valley aquifer, Baja California, Mexico
International audienceA regional groundwater flow model was developed, in order to evaluate the water table behavior in the region of the Guadalupe Valley, in Baja California, Mexico. The State of Baja California has been subject to an increment of the agricultural, urban and industrials activities, implicating a growing water-demand. However, the State is characterized by its semi-arid climate with low surface water availability; resulting in an extensive use of groundwater in local aquifer. Based on historic piezometric information of the last two decades, however, a negative evolution could be observed, resulting a negative storage volume. So far, there is not an integral hydrogeological evaluation that determine the real condition of the groundwater resource, and that permit to planning a management of the Guadalupe Valley Aquifer. A steady-state calibration model was carried out in order to obtain the best possible match to measured levels at the Guadalupe Valley Aquifer. The contours of calculated water table elevations for January 1983 were reproduced. Generally, the comparison of the observed and calculated water table configurations have a good qualitative and quantitatively adjustment. Nowadays, it is count with a hydrogeological model that can be used for simulates the groundwater flow in the region of the Guadalupe Valley
Vibrating Winding Branes, Wrapping Democracy and Stabilization of Extra Dimensions in Dilaton Gravity
We show that, in the context of dilaton gravity, a recently proposed
democratic principle for intersection possibilities of branes winding around
extra dimensions yield stabilization, even with the inclusion of momentum modes
of the wrapped branes on top of the winding modes. The constraints for
stabilization massaged by string theory inputs forces the number of observed
dimensions to be three. We also discuss consequences of adding ordinary matter
living in the observed dimensions.Comment: Added a section discussing the linear and non-linear stability of the
equilibrium point of the scale factors of the extra dimensions. Corrected a
typo in the original field equations and other typos. Added and changed
references. Final version appeared in JHE
Critical phenomena of thick branes in warped spacetimes
We have investigated the effects of a generic bulk first-order phase
transition on thick Minkowski branes in warped geometries. As occurs in
Euclidean space, when the system is brought near the phase transition an
interface separating two ordered phases splits into two interfaces with a
disordered phase in between. A remarkable and distinctive feature is that the
critical temperature of the phase transition is lowered due to pure geometrical
effects. We have studied a variety of critical exponents and the evolution of
the transverse-traceless sector of the metric fluctuations.Comment: revtex4, 4 pages, 4 figures, some comments added, typos corrected,
published in PR
Metodologia para análise de rentabilidade e riscos de sistemas agroflorestais.
Este trabalho propõe uma metodologia para avaliação da rentabilidade e riscos de sistemas agroflorestais e de cada um dos seus componentes culturais, através da combinação da técnica Monte Carlo, comumente utilizada para avaliar riscos em investimentos, com um método de rateio dos custos comuns entre os componentes culturais, possibilitando a análise do sistema como um todo e a análise isolada de cada um desses componentes.bitstream/CPAF-AC/3989/1/doc47.pd
Cell death induced by the application of alternating magnetic fields to nanoparticle-loaded dendritic cells
In this work, the capability of primary, monocyte-derived dendritic cells
(DCs) to uptake iron oxide magnetic nanoparticles (MNPs) is assessed and a
strategy to induce selective cell death in these MNP-loaded DCs using external
alternating magnetic fields (AMFs) is reported. No significant decrease in the
cell viability of MNP-loaded DCs, compared to the control samples, was observed
after five days of culture. The amount of MNPs incorporated into the cytoplasm
was measured by magnetometry, which confirmed that 1 to 5 pg of the particles
were uploaded per cell. The intracellular distribution of these MNPs, assessed
by transmission electron microscopy, was found to be primarily inside the
endosomic structures. These cells were then subjected to an AMF for 30 min, and
the viability of the blank DCs (i.e., without MNPs), which were used as control
samples, remained essentially unaffected. However, a remarkable decrease of
viability from approximately 90% to 2-5% of DCs previously loaded with MNPs was
observed after the same 30 min exposure to an AMF. The same results were
obtained using MNPs having either positive (NH2+) or negative (COOH-) surface
functional groups. In spite of the massive cell death induced by application of
AMF to MNP-loaded DCs, the amount of incorporated magnetic particles did not
raise the temperature of the cell culture. Clear morphological changes at the
cell structure after magnetic field application were observed using scanning
electron microscopy. Therefore, local damage produced by the MNPs could be the
main mechanism for the selective cell death of MNP-loaded DCs under an AMF.
Based on the ability of these cells to evade the reticuloendothelial system,
these complexes combined with an AMF should be considered as a potentially
powerful tool for tumour therapy.Comment: In Press. 33 pages, 11 figure
Coalescence and Anti-Coalescence Interference of Two-Photon Wavepacket in a Beam Splitter
We study a general theory on the interference of two-photon wavepacket in a
beam splitter (BS). We find that the perfect coalescence interference requires
a symmetric spectrum of two-photon wavepacket which can be entangled or
un-entangled. Furthermore, we introduce a two-photon wavepacket with
anti-symmetric spectrum, which is related with photon entanglement and shows a
perfect anti-coalescence effect. The theory present uniform and complete
explanation to two-photon interference.Comment: 5 pages, 2 figure
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