2,338 research outputs found
Temperature effects on the magnetization of quasi-one-dimensional Peierls distorted materials
It is shown that temperature acts to disrupt the magnetization of Peierls
distorted quasi-one-dimensional materials (Q1DM). The mean-field finite
temperature phase diagram for the field theory model employed is obtained by
considering both homogeneous and inhomogeneous condensates. The tricritical
points of the second order transition lines of the gap parameter and
magnetization are explicitly calculated. It is also shown that in the absence
of an external static magnetic field the magnetization is always zero, at any
temperature. As expected, temperature does not induce any magnetization effect
on Peierls distorted Q1DM.Comment: 11 pages, 2 figure
Literacy: A cultural influence on functional left-right differences in the inferior parietal cortex
The current understanding of hemispheric interaction is limited. Functional hemispheric specialization is likely to depend on both genetic and environmental factors. In the present study we investigated the importance of one factor, literacy, for the functional lateralization in the inferior parietal cortex in two independent samples of literate and illiterate subjects. The results show that the illiterate group are consistently more right-lateralized than their literate controls. In contrast, the two groups showed a similar degree of left-right differences in early speech-related regions of the superior temporal cortex. These results provide evidence suggesting that a cultural factor, literacy, influences the functional hemispheric balance in reading and verbal working memory-related regions. In a third sample, we investigated grey and white matter with voxel-based morphometry. The results showed differences between literacy groups in white matter intensities related to the mid-body region of the corpus callosum and the inferior parietal and parietotemporal regions (literate > illiterate). There were no corresponding differences in the grey matter. This suggests that the influence of literacy on brain structure related to reading and verbal working memory is affecting large-scale brain connectivity more than grey matter per se
Surface nano-patterning through styrene adsorption on Si(100)
We present an ab initio study of the structural and electronic properties of
styrene molecules adsorbed on the dimerized Si(100) surface at different
coverages, ranging from the single-molecule to the full monolayer. The
adsorption mechanism primarily involves the vinyl group via a [2+2]
cycloaddition process that leads to the formation of covalent Si-C bonds and a
local surface derelaxation, while it leaves the phenyl group almost
unperturbed. The investigation of the functionalized surface as a function of
the coverage (e.g. 0.5 -- 1 ML) and of the substrate reconstruction reveals two
major effects. The first results from Si dimer-vinyl interaction and concerns
the controlled variation of the energy bandgap of the interface. The second is
associated to phenyl-phenyl interactions, which gives rise to a regular pattern
of electronic wires at surface, stemming from the pi-pi coupling. These
findings suggest a rationale for tailoring the surface nano-patterning of the
surface, in a controlled way.Comment: 19 pages (preprint), 4 figures, supplementary materia
Phase Transition in Asymmetrical Superfluids I: Equal Fermi Surfaces
In this paper, we study phase transitions in asymmetrical fermion
superfluids. In this scenario, the candidates to form pair are particles with
mismatched masses and chemical potentials. We derive an expression for the
critical temperature in terms of the gap and masses (or chemical potentials)
when the constraint of equal Fermi surfaces is imposed.Comment: RevTex, 11 pages, 2 figures, typos corrected and an appendix added,
accepted for publication in Phys. Rev.
Maximal acceleration or maximal accelerations?
We review the arguments supporting the existence of a maximal acceleration
for a massive particle and show that different values of this upper limit can
be predicted in different physical situations.Comment: 13 pages, Latex, to be published in Int. J. Mod. Phys.
Quantum normal-to-inhomogeneous superconductor phase transition in nearly two-dimensional metals
In multi-band systems, electrons from different orbitals coexist at the Fermi
surface. An attractive interaction among these quasi-particles gives rise to
inter-band or hybrid pairs which eventually condense in a superconducting
state. These quasi-particles have a natural mismatch of their Fermi
wave-vectors, , which depends on the strength of the hybridization
between their orbitals. The existence of this natural scale suggests the
possibility of inhomogeneous superconducting ground states in these systems,
even in the absence of an applied magnetic field. Furthermore, since
hybridization depends on pressure, this provides an external parameter to
control the wave-vectors mismatch at the Fermi surface. In this work, we study
the phase diagram of a two-dimensional, two-band metal with inter-band pairing.
We show that as the mismatch between the Fermi wave-vectors of the two hybrid
bands is reduced, the system presents a normal-to-inhomogeneous superconductor
quantum phase transition at a critical value of the hybridization
. The superconducting ground state for is characterized
by a wave-vector with magnitude . Here
is the superconducting gap in the homogeneous state and
the average Fermi velocity. We discuss the nature of the quantum critical point
(QCP) at and obtain the associated quantum critical exponents.Comment: 6 pages, 4 figure
Symmetry Nonrestoration in a Resummed Renormalized Theory at High Temperature
We reinvestigate the interesting phenomenon of symmetry nonrestoration at
high temperature in the multifield O(N_1) X O(N_2) model. We apply modified
self-consistent resummation (MSCR) in order to obtain the scalar dressed masses
and find in what circumstances a resummed multifield theory which has symmetry
(non)restoration can be renormalized. It is shown that, aside from the
consistency of the MSCR method, the basic ingredient that guarantees the
renormalization of a multifield model within a resummation approach is the T^2
mass behavior of field theory at high temperature.Comment: 14 pages, 1 ps figure, revtex, Phys. Rev. D versio
Pion dispersion relation at finite density and temperature
We study the behavior of the pion dispersion relation in a pion medium at
finite density and temperature. We introduce a pion chemical potential to
describe the finite pion number density and argue that such description is
valid during the hadronic phase of a relativistic heavy-ion collision between
chemical and thermal freeze-out. We make use of an effective Lagrangian that
explicitly respects chiral symmetry through the enforcement of the chiral Ward
identities. The pion dispersion relation is computed through the computation of
the pion self-energy in a non-perturbative fashion by giving an approximate
solution to the Schwinger-Dyson equation for this self-energy. The dispersion
relation is described in terms of a density and temperature dependent mass and
an index of refraction which is also temperature, density as well as momentum
dependent. The index of refraction is larger than unity for all values of the
momentum for finite and . We conclude by exploring some of the
possible consequences for the propagation of pions through the boundary between
the medium and vacuum.Comment: 7 pages, 5 figures, 3 new references, published versio
Are deciduous upper molars and lower canines useful for sex estimation?
Objective: This paper investigates whether deciduous upper molars and lower canines have sexual dimorphic features, exploring these teeth' dimensions and the presence of Zuckerkandl's tubercle and Carabelli's cusp on the first and second upper molars.
Design: We analyzed 64 pairs of dental plaster casts from 34 females and 30 males aged between 3 and 12 years. We measured the first and second deciduous upper molars and the lower deciduous canines (maximum mesiodistal and buccolingual length), and we registered the presence of the Zuckerkandl's tubercle and the Carabelli's cusp on the first and second upper molars, respectively.
Results: Regarding the differentiation between sexes using Carabelli's cusp and Zuckerkandl's tubercle, the classification was not independent of Carabelli's cusp presence only for tooth 65 (p = 0.035). In all other teeth, whether for Carabelli's cusp or Zuckerkandl's tubercle, their presence was similar for both sexes. There were statistically significant differences between sexes (p < 0.05) for the buccolingual measurements of both upper second molars, the first right upper molar, and the right canine. The developed model allowed for a 64.1% accuracy in sex estimation.
Conclusions: The study suggests that while Carabelli's cusp and Zuckerkandl's tubercle in upper deciduous molars don't consistently differ between sexes, tooth size, particularly the buccolingual measurements of certain teeth, including upper deciduous molars and lower canines, may provide a more reliable criterion for sex estimation. The developed model depicted moderate accuracy, underscoring the need for a multifactorial approach when estimating sex from skeletal remains. It suggests that while dental features can contribute to sex estimation, they should be used in conjunction with other skeletal or molecular markers to improve accuracy
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