10,824 research outputs found
Analytic Relations between Localizable Entanglement and String Correlations in Spin Systems
We study the relation between the recently defined localizable entanglement
and generalized correlations in quantum spin systems. Differently from the
current belief, the localizable entanglement is always given by the average of
a generalized string. Using symmetry arguments we show that in most spin 1/2
and spin 1 systems the localizable entanglement reduces to the spin-spin or
string correlations, respectively. We prove that a general class of spin 1
systems, which includes the Heisenberg model, can be used as perfect quantum
channel. These conclusions are obtained in analytic form and confirm some
results found previously on numerical grounds.Comment: 5 pages, RevTeX
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
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
Tuned liquid dampers simulation for earthquake response control of buildings
This paper is focused on the study of an earthquake protection system, the Tuned Liquid Damper (TLD), which
can, if adequately designed, reduce earthquake demands on buildings. This positive effect is accomplished taking
into account the oscillation of the free surface of a fluid inside a tank (sloshing). The behaviour of an isolated
Tuned Liquid Damper, subjected to a sinusoidal excitation at its base, with different displacement amplitudes,
was studied by finite element analysis. The efficiency of the TLD in improving the seismic response of an existing building, representative of modern architecture buildings in southern European countries was also evaluated based on linear dynamic analyses
Medida de desumanização baseada em traços: adaptação para a população Portuguesa
Although dehumanization (i.e., the denial of full humanness to others; Haslam, 2006) has been a frequent subject in social psychology, a set of traits designed to evaluate this phenomenon has not been validated to the Portuguese population. The main purpose of this study was to translate, culturally adapt and validate a set of dehumanization traits proposed by Haslam and colleagues (Haslam & Bain, 2007; Haslam, Bain, Douge, Lee & Bastian, 2005), which measure both the denial of uniquely human and human nature traits. A sample of 597 individuals (Mage = 40.83; SD = 11.50) were asked to rate a set of 52 traits on how much they perceived each as a characteristic of human nature and human uniqueness, as well as its desirability. T-tests were conducted to distinguish between low and high rated traits in each dimension, and to construct clusters of traits that differ in each dimension. We successfully provide a measure containing positive traits in both senses of humanness dimensions; however, we were only able to validate a human uniqueness measure with negative valence. Implications of this measure for future research on dehumanization processes are discussed.info:eu-repo/semantics/publishedVersio
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
Stochastic semiclassical fluctuations in Minkowski spacetime
The semiclassical Einstein-Langevin equations which describe the dynamics of
stochastic perturbations of the metric induced by quantum stress-energy
fluctuations of matter fields in a given state are considered on the background
of the ground state of semiclassical gravity, namely, Minkowski spacetime and a
scalar field in its vacuum state. The relevant equations are explicitly derived
for massless and massive fields arbitrarily coupled to the curvature. In doing
so, some semiclassical results, such as the expectation value of the
stress-energy tensor to linear order in the metric perturbations and particle
creation effects, are obtained. We then solve the equations and compute the
two-point correlation functions for the linearized Einstein tensor and for the
metric perturbations. In the conformal field case, explicit results are
obtained. These results hint that gravitational fluctuations in stochastic
semiclassical gravity have a ``non-perturbative'' behavior in some
characteristic correlation lengths.Comment: 28 pages, RevTeX, no figure
Obstetric Outcome of Twin Pregnancies Conceived by in Vitro fertilization (IVF) and Ovulation Induction Compared with those Conceived Spontaneously
Introduction: Uncontrolled studies suggest that twins conceived by in vitro fertilization have increased rates of preterm birth and low birth weight and would warrant increased antenatal monitoring. The objective of this study was to compare the obstetric outcome of twin pregnancies conceived by in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) and ovulation induction with those conceived spontaneously.
Methods: All twin deliveries achieved by IVF/ICSI (n=235) and ovulation induction (n=68) from September 1994 through December 2010 were evaluated. Both groups and an additional control group who conceived
spontaneously (n=997) and was delivered during the same time period were compared with each other.
Results: In univariate analysis, patients who conceived with the assistance of IVF/ICSI had a significantly higher risk of being older (p=0.01), nulliparous (p=0.01), having hypertensive disorders (p=0.012), gestational diabetes mellitus (p=0.031), cesarean section (p=0.008) and lower gestational age at birth, compared with
the control group. Newborns had similar birthweights in all groups (2229±544g; 2102±619g; 2251±553g). Spontaneous pregnancies had a higher risk of being monochorionic 38.4% versus 16.2% and 10.2% (p=0.01). Multivariate analysis however showed that patients who conceived with the assistance of IVF/ICSI only had a higher risk of gestational diabetes (OR=1.91,95%CI 1.168-3.120; p=0.01).
Conclusions: Our study shows that twin pregnancies conceived with the assistance of IVF/ICSI had a higher risk of gestacional diabetes and a lower gestacional age at birth. Birthweights were similar, as was the incidence of perinatal death, low birth weight infants, and congenital malformations
Desempenho de variedades de milho em diferentes densidades populacionais na safrinha em Pedro Afonso, TO.
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