3,471 research outputs found
Measurements and analysis of the upper critical field on an underdoped and overdoped compounds
The upper critical field is one of the many non conventional
properties of high- cuprates. It is possible that the
anomalies are due to the presence of inhomogeneities in the local charge
carrier density of the planes. In order to study this point, we
have prepared good quality samples of polycrystalline
using the wet-chemical method, which has demonstrated to produce samples with a
better cation distribution. In particular, we have studied the temperature
dependence of the second critical field, , through the magnetization
measurements on two samples with opposite average carrier concentration
() and nearly the same critical temperature, namely
(underdoped) and (overdoped). The results close to do not
follow the usual Ginzburg-Landau theory and are interpreted by a theory which
takes into account the influence of the inhomogeneities.Comment: Published versio
Nonrelativistic Quantum Analysis of the Charged Particle-Dyon System on a Conical Spacetime
In this paper we develop the nonrelativistic quantum analysis of the charged
particle-dyon system in the spacetime produced by an idealized cosmic string.
In order to do that, we assume that the dyon is superposed to the cosmic
string. Considering this peculiar configuration {\it conical} monopole
harmonics are constructed, which are a generalizations of previous monopole
harmonics obtained by Wu and Yang(1976 {\it Nucl. Phys. B} {\bf 107} 365)
defined on a conical three-geometry. Bound and scattering wave functions are
explicitly derived. As to bound states, we present the energy spectrum of the
system, and analyze how the presence of the topological defect modifies
obtained result. We also analyze this system admitting the presence of an extra
isotropic harmonic potential acting on the particle. We show that the presence
of this potential produces significant changes in the energy spectrum of the
system.Comment: Paper accepted for publication in Classical and Quantum Gravit
Neospora caninum em bovinos de assentamentos rurais em CorumbĂĄ, MS.
Este trabalho vem complementar açÔes de avaliação sanitåria dos assentamentos rurais com foco nas perdas por problemas reprodutivos, através da inclusão de um levantamento epidemiológico de animais portadores de Neospora caninum.bitstream/CPAP-2010/57323/1/CT85.pd
Correlators of Giant Gravitons from dual ABJ(M) Theory
We generalize the operators of ABJM theory, given by Schur polynomials, in
ABJ theory by computing the two point functions in the free field and at finite
limits. These polynomials are then identified with the states of
the dual gravity theory. Further, we compute correlators among giant gravitons
as well as between giant gravitons and ordinary gravitons through the
corresponding correlators of ABJ(M) theory. Finally, we consider a particular
non-trivial background produced by an operator with an -charge of
and find, in presence of this background, due to the contribution of
the non-planar corrections, the large expansion is replaced by
and respectively.Comment: Latex, 32+1 pages, 2 figures, journal versio
B stars as a diagnostic of star-formation at low and high redshift
We have extended the evolutionary synthesis models by Leitherer et al.
(1999b) by including a new library of B stars generated from the IUE
high-dispersion spectra archive. We present the library and show how the
stellar spectral properties vary according to luminosity classes and spectral
types. We have generated synthetic UV spectra for prototypical young stellar
populations varying the IMF and the star formation law. Clear signs of age
effects are seen in all models. The contribution of B stars in the UV line
spectrum is clearly detected, in particular for greater ages when O stars have
evolved. With the addition of the new library we are able to investigate the
fraction of stellar and interstellar contributions and the variation in the
spectral shapes of intense lines. We have used our models to date the spectrum
of the local super star cluster NGC1705-1. Photospheric lines of CIII1247,
SiIII1417, and SV1502 were used as diagnostics to date the burst of NGC 1705-1
at 10 Myr. We have selected the star-forming galaxy 1512-cB58 as a first
application of the new models to high-z galaxies. This galaxy is at z=2.723, it
is gravitationally lensed, and its high signal-to-noise Keck spectrum show
features typical of local starburst galaxies, such as NGC 1705-1. Models with
continuous star formation were found to be more adequate for 1512-cB58 since
there are spectral features typical of a composite stellar population of O and
B stars. A model with Z =0.4Z_solar and an IMF with alpha=2.8 reproduces the
stellar features of the 1512-cB58 spectrum.Comment: 23 pages with figures, see
http://sol.stsci.edu/~demello/welcomeb.htm
Strings from Feynman Graph counting : without large N
A well-known connection between n strings winding around a circle and
permutations of n objects plays a fundamental role in the string theory of
large N two dimensional Yang Mills theory and elsewhere in topological and
physical string theories. Basic questions in the enumeration of Feynman graphs
can be expressed elegantly in terms of permutation groups. We show that these
permutation techniques for Feynman graph enumeration, along with the Burnside
counting lemma, lead to equalities between counting problems of Feynman graphs
in scalar field theories and Quantum Electrodynamics with the counting of
amplitudes in a string theory with torus or cylinder target space. This string
theory arises in the large N expansion of two dimensional Yang Mills and is
closely related to lattice gauge theory with S_n gauge group. We collect and
extend results on generating functions for Feynman graph counting, which
connect directly with the string picture. We propose that the connection
between string combinatorics and permutations has implications for QFT-string
dualities, beyond the framework of large N gauge theory.Comment: 55 pages + 10 pages Appendices, 23 figures ; version 2 - typos
correcte
Vacuum polarization induced by a cylindrical boundary in the cosmic string spacetime
In this paper we investigate the Wightman function, the renormalized vacuum
expectation values of the field square, and the energy-momentum tensor for a
massive scalar field with general curvature coupling inside and outside of a
cylindrical shell in the generalized spacetime of straight cosmic string. For
the general case of Robin boundary condition, by using the generalized
Abel-Plana formula, the vacuum expectation values are presented in the form of
the sum of boundary-free and boundary-induced parts. The asymptotic behavior of
the vacuum expectation values of the field square, energy density and stresses
are investigated in various limiting cases. The generalization of the results
to the exterior region is given for a general cylindrically symmetric static
model of the string core with finite support.Comment: 21 pages, 5 figure
Fermionic current densities induced by magnetic flux in a conical space with a circular boundary
We investigate the vacuum expectation value of the fermionic current induced
by a magnetic flux in a (2+1)-dimensional conical spacetime in the presence of
a circular boundary. On the boundary the fermionic field obeys MIT bag boundary
condition. For irregular modes, a special case of boundary conditions at the
cone apex is considered, when the MIT bag boundary condition is imposed at a
finite radius, which is then taken to zero. We observe that the vacuum
expectation values for both charge density and azimuthal current are periodic
functions of the magnetic flux with the period equal to the flux quantum
whereas the expectation value of the radial component vanishes. For both
exterior and interior regions, the expectation values of the current are
decomposed into boundary-free and boundary-induced parts. For a massless field
the boundary-free part in the vacuum expectation value of the charge density
vanishes, whereas the presence of the boundary induces nonzero charge density.
Two integral representations are given for the boundary-free part in the case
of a massive fermionic field for arbitrary values of the opening angle of the
cone and magnetic flux. The behavior of the induced fermionic current is
investigated in various asymptotic regions of the parameters. At distances from
the boundary larger than the Compton wavelength of the fermion particle, the
vacuum expectation values decay exponentially with the decay rate depending on
the opening angle of the cone. We make a comparison with the results already
known from the literature for some particular cases.Comment: 34 pages, 6 figure
Glueball calculations in large-N_c gauge theory
We use the light-front Hamiltonian of transverse lattice gauge theory to
compute from first principles the glueball spectrum and light-front
wavefunctions in the leading order of the 1/N_c colour expansion. We find
0^{++}, 2^{++}, and 1^{+-} glueballs having masses consistent with N_c=3 data
available from Euclidean lattice path integral methods. The wavefunctions
exhibit a light-front constituent gluon structure.Comment: 4 pages, 2 figures, uses macro boxedeps.tex, minor corrections in
revised versio
Effect of One Year of Cryopreservation on the Activity of Lysosomal Hydrolases from EBV-Transformed Lymphocytes
Background. The Epstein-Barr virus (EBV) was used as an agent of B lymphocyte proliferation for subsequent diagnosis of lysosomal storage disease.
Due to the constant handling of long-preserved samples in our cell bank, we decided to observe the behavior and then compare cultured and frozen samples for at least one year's cryopreservation. Methods. Twenty-five samples from healthy individuals were used to assess the
possible changes in activity of enzymes ÎČ-galactosidase, ÎČ-glucosidase, α-iduronidase, α-galactosidase, and α-glucosidase. Transmission electron microscopy was used to confirm cell transformation of B lymphocytes into EBV-infected cells, generating lymphoblastoid cell lines.
Results. Transmission electron microscopy findings confirmed previous reports in the literature that is, significant and evident morphological changes in the nucleus occur after day 12 and the consequent cell transformation into EBV-infected cells. After thawing and subsequent treatment with the five enzymes utilized, we observed no significant changes in samples cryopreserved for more than one year, as compared to samples cultured for 12 days
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