19,137 research outputs found
Quantum Effects in the Spacetime of a Magnetic Flux Cosmic String
In this work we compute the vacuum expectation values of the energy-momentum
tensor and the average value of a massive, charged scalar field in the presence
of a magnetic flux cosmic string for both zero- and finite-temperature cases.Comment: To appear in the Int. Journal of Modern Phys. A (special issue).
Proceedings of the Second International Londrina Winter School on
Mathematical Methods in Physics, Londrina, Brazil, August 200
Momentum space saturation model for deep inelastic scattering and single inclusive hadron production
We show how the AGBS model, originally developed for deep inelastic
scattering applied to HERA data on the proton structure function, can also
describe the RHIC data on single inclusive hadron yield for and
collisions through a new simultaneous fit. The single inclusive hadron
production is modeled through the color glass condensate, which uses the
quark(and gluon)--condensate amplitudes in momentum space. The AGBS model is
also a momentum space model based on the asymptotic solutions of the BK
equation, although a different definition of the Fourier transform is used.
This aspect is overcome and a description entirely in transverse momentum of
both processes arises for the first time. The small difference between the
simultaneous fit and the one for HERA data alone suggests that the AGBS model
describes very well both kind of processes and thus emerges as a good tool to
investigate the inclusive hadron production data. We use this model for
predictions at LHC energies, which agree very well with available experimental
data.Comment: 10 pages, 7 figure
Magnetic properties and critical behavior of disordered Fe_{1-x}Ru_x alloys: a Monte Carlo approach
We study the critical behavior of a quenched random-exchange Ising model with
competing interactions on a bcc lattice. This model was introduced in the study
of the magnetic behavior of Fe_{1-x}Ru_x alloys for ruthenium concentrations
x=0%, x=4%, x=6%, and x=8%. Our study is carried out within a Monte Carlo
approach, with the aid of a re-weighting multiple histogram technique. By means
of a finite-size scaling analysis of several thermodynamic quantities, taking
into account up to the leading irrelevant scaling field term, we find estimates
of the critical exponents \alpha, \beta, \gamma, and \nu, and of the critical
temperatures of the model. Our results for x=0% are in excellent agreement with
those for the three-dimensional pure Ising model in the literature. We also
show that our critical exponent estimates for the disordered cases are
consistent with those reported for the transition line between paramagnetic and
ferromagnetic phases of both randomly dilute and Ising models. We
compare the behavior of the magnetization as a function of temperature with
that obtained by Paduani and Branco (2008), qualitatively confirming the
mean-field result. However, the comparison of the critical temperatures
obtained in this work with experimental measurements suggest that the model
(initially obtained in a mean-field approach) needs to be modified
Casimir energy in a small volume multiply connected static hyperbolic pre-inflationary Universe
A few years ago, Cornish, Spergel and Starkman (CSS), suggested that a
multiply connected ``small'' Universe could allow for classical chaotic mixing
as a pre-inflationary homogenization process. The smaller the volume, the more
important the process. Also, a smaller Universe has a greater probability of
being spontaneously created. Previously DeWitt, Hart and Isham (DHI) calculated
the Casimir energy for static multiply connected flat space-times. Due to the
interest in small volume hyperbolic Universes (e.g. CSS), we generalize the DHI
calculation by making a a numerical investigation of the Casimir energy for a
conformally coupled, massive scalar field in a static Universe, whose spatial
sections are the Weeks manifold, the smallest Universe of negative curvature
known. In spite of being a numerical calculation, our result is in fact exact.
It is shown that there is spontaneous vacuum excitation of low multipolar
components.Comment: accepted for publication in phys. rev.
Superfluid to normal phase transition and extreme regularity of superdeformed bands
We derive the exact semiclassical expression for the second inertial
parameter for the superfluid and normal phases. Interpolation between
these limiting values shows that the function changes sign at the
spin , which is critical for a rotational spectrum. The quantity
turns out to be a sensitive measure of the change in static pairing
correlations. The superfluid-to-normal transition reveals itself in the
specific variation of the ratio versus spin with the
plateau characteristic of the normal phase. We find this dependence to be
universal for normal deformed and superdeformed bands. The long plateau with a
small value explains the extreme regularity of
superdeformed bands.Comment: 30 pages in LaTeX, 6 figures (PostScript). To be published in
Yadernaya Fizika (Physics of Atomic Nuclei), special edition dedecated to the
90th birthday of Prof. I. I. Gurevit
Nanofibers as a Vehicle for the Synthetic Attactant TRIMEDLURE to be Used for Ceratitis capitata Wied: (Diptera, Tethritidae) Capture
 The Mediterranean fruit fly (medfly), Ceratitis capitata (Wied.) is considered a serious pest of citrus fruits in the southeast of Brazil because of the direct economic impact they have on fruit production and quarantine restrictions for fruit exports. Monitoring and detection of the medfly, using food bait and synthetic attractants, is a key step towards signalling the need for management and control. The aim of this study has been to verify the attractiveness of innovative nanofiber formulations with Trimedlure (TML) for the male of C. capitata in laboratory and field cage tests.Material and Methods: The nanofibers were produced by solution or emulsion electrospinning, containing TML and polymers, such as polycaprolactone, PEG-polycaprolactone, ethyl cellulose and polyvinyl acetate-PVP.Results: At the laboratory the electrophysiological responses were accessed by the eletroanntenogram technique and in the field by the cage test. The bioactivity of C. capitata antennae was highest when stimulated with all TML nanofiber treatments rather than their controls. There were no differences among the TML nanofiber treatments. In the field cages the same number of medflies were found on the adhesive traps baited with one of each of the TML nanofibers
First Trimester Prediction of Pre-Eclampsia in Low Risk Pregnancies: Determining the Cut-Off in a Portuguese Group
Objective:We aimed to identify the cut-off for risk of pre-eclampsia (PE) in Portuguese population by applying the first trimester prediction model from Fetal Medicine Foundation (FMF) in a prospective enrolled cohort of low risk pregnant women.
Population and methods: A prospective cohort of low risk singleton pregnancies underwent routine first-trimester scree -
ning from 2011 through 2013. Maternal characteristics, blood pressure, uterine artery Doppler, levels of pregnancy-associated plasma protein-A (PAPP-A) and free b-human chorionic gonadotropin were evaluated. The prediction of PE in first trimester was calculated through software Astraia, the outcome obtained from medical records and the cutoff value was subse quently calculated.
Results:Of the 273 enrolled patients, 7 (2.6%) developed PE. In first trimester women who developed PE presented higher uterine arteries resistance, represented by higher values of lowest and mean uterine pulsatility index, p <0.005. There was no statistical significance among the remaining maternal characteristics, body mass index, blood pressure and PAPP-A. Using the FMF first trimester PE algorithm, an ideal cut-off of 0.045 (1/22) would correctly detect 71% women who developed PE for a 12% false positive rate and a likelihood ratio of 12.98 (area under the curve: 0.69; confidence interval 95%: 0.39-0.99). By applying the reported cutoff to our cohort, we would obtain 71.4% true positives, 88.3% true negatives, 11.4% false positives and 28.6% false negatives.
Conclusion: By applying a first trimester PE prediction model to low risk pregnancies derived from a Portuguese population, a significant proportion of patients would have been predicted as high risk. New larger studies are required to confirm the present findings
Enraizamento de estacas de urucuzeiro Bixa orellana L.
bitstream/item/34014/1/CPATU-CirTec55-2.pd
A new non-Fermi liquid fixed point
We study a new exchange interaction in which the conduction electrons with
pseudo spin interact with the impurity spin . Due to the
overscreening of the impurity spin by higher conduction electron spin, a new
non-trivial intermediate coupling strength fixed point is realized. Using the
numerical renormalization group (NRG), we show that the low-energy spectra are
described by a non-Fermi liquid excitation spectrum. A conformal field theory
analysis is compared with NRG results and excellent agreement is obtained.
Using the double fusion rule to generate the operator spectrum with the
conformal theory, we find that the specific heat coefficient and magnetic
susceptibility will diverge as , that the scaling dimension of an
applied magnetic field is , and that exchange anisotropy is always
relevant. We discuss the possible relevance of our work to two-level system
Kondo materials and dilute cerium alloys, and we point out a paradox in
understanding the Bethe-Ansatz solutions to the multichannel Kondo model.Comment: Revised. 20 page
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