1,425 research outputs found
Granular cell tumor of the trachea as a rare cause of dyspnea in a young woman
Tracheal granular cell tumors are rare neurogenic neoplasms characterized by an indolent behavior. We report the case of a young woman affected by this tumor with non-specific clinical presentation. We performed a literature search in order to identify all the cases of tracheal granular cell tumor and to summarize the current state of knowledge about this rare disease
Computer simulations of hard pear-shaped particles
We report results obtained from Monte Carlo simulations investi-
gating mesophase formation in two model systems of hard pear-shaped
particles. The first model considered is a hard variant of the trun-
cated Stone-Expansion model previously shown to form nematic and
smectic mesophases when embedded within a 12-6 Gay-Berne-like po-
tential [1]. When stripped of its attractive interactions, however, this system is found to lose its liquid crystalline phases. For particles of length to breadth ratio k = 3, glassy behaviour is seen at high pressures, whereas for k = 5 several bi-layer-like domains are seen, with high intradomain order but little interdomain orientational correlation. For the second model, which uses a parametric shape parameter based on the generalised Gay-Berne formalism, results are presented for particles with elongation k = 3; 4 and 5. Here, the systems with k = 3 and 4 fail to display orientationally ordered phases, but that with k = 5 shows isotropic, nematic and, unusually for a hard-particle model, interdigitated smectic A2 phases.</p
Instantons and Matter in N=1/2 Supersymmetric Gauge Theory
We extend the instanton calculus for N=1/2 U(2) supersymmetric gauge theory
by including one massless flavor. We write the equations of motion at leading
order in the coupling constant and we solve them exactly in the
non(anti)commutativity parameter C. The profile of the matter superfield is
deformed through linear and quadratic corrections in C. Higher order
corrections are absent because of the fermionic nature of the back-reaction.
The instanton effective action, in addition to the usual 't Hooft term,
includes a contribution of order C^2 and is N=1/2 invariant. We argue that the
N=1 result for the gluino condensate is not modified by the presence of the new
term in the effective action.Comment: 33 pages, harvmac; v2: minor changes, added references; v3: added
analysis of the instanton measure in section
Instanton Calculations for N=1/ 2 super Yang-Mills Theory
We study (anti-) instantons in super Yang-Mills theories defined on a non
anticommutative superspace. The instanton solution that we consider is the same
as in ordinary SU(2) N=1 super Yang-Mills, but the anti-instanton receives
corrections to the U(1) part of the connection which depend quadratically on
fermionic coordinates, and linearly on the deformation parameter C. By
substituting the exact solution into the classical Lagrangian the topological
charge density receives a new contribution which is quadratic in C and quartic
in the fermionic zero-modes. The topological charge turns out to be zero. We
perform an expansion around the exact classical solution in presence of a
fermionic background and calculate the full superdeterminant contributing to
the one-loop partition function. We find that the one-loop partition function
is not modified with respect to the usual N=1 super Yang-Mills.Comment: 27 pages, harmvac, Redone the computation of topological charge, a
section has been rewritten and references adde
Direct sampling of complex landscapes at low temperatures: the three-dimensional +/-J Ising spin glass
A method is presented, which allows to sample directly low-temperature
configurations of glassy systems, like spin glasses. The basic idea is to
generate ground states and low lying excited configurations using a heuristic
algorithm. Then, with the help of microcanonical Monte Carlo simulations, more
configurations are found, clusters of configurations are determined and
entropies evaluated. Finally equilibrium configuration are randomly sampled
with proper Gibbs-Boltzmann weights.
The method is applied to three-dimensional Ising spin glasses with +- J
interactions and temperatures T<=0.5. The low-temperature behavior of this
model is characterized by evaluating different overlap quantities, exhibiting a
complex low-energy landscape for T>0, while the T=0 behavior appears to be less
complex.Comment: 9 pages, 7 figures, revtex (one sentence changed compared to v2
Ultrametricity in 3D Edwards-Anderson spin glasses
We perform an accurate test of Ultrametricity in the aging dynamics of the
three dimensional Edwards-Anderson spin glass. Our method consists in
considering the evolution in parallel of two identical systems constrained to
have fixed overlap. This turns out to be a particularly efficient way to study
the geometrical relations between configurations at distant large times. Our
findings strongly hint towards dynamical ultrametricity in spin glasses, while
this is absent in simpler aging systems with domain growth dynamics. A recently
developed theory of linear response in glassy systems allows to infer that
dynamical ultrametricity implies the same property at the level of equilibrium
states.Comment: 4 pages, 5 figure
Programa de Enriquecimiento Instrumental (PEI) básico en niños con TDAH y Dislexia
Testes de eficácia do Programa de Enriquecimento Instrumental (PEI), versão básica, sobre inteligibilidade, processamento visoespacial e flexibilidade cognitiva. Como essas habilidades podem estar comprometidas em distúrbios neurológicos, como TDAH e dislexia, sua eficácia foi investigada em 22 crianças. Ou o grupo experimental (GE) foi comparado ou controlado por testes neuropsicológicos, com 26 sessões intervencionistas. Uma interação entre ou grupo nenhum momento e como diferenças de desempenho entre os dois nos analisaram momentos. Essa comparação revela o principal interesse das tarefas de flexibilidade cognitiva com um grande tamanho de efeito; em oito medidas com efeito moderado tamanho (incluindo medidas de inteligência,visospatial processamento e funções executivas) e em 13 medidas com tamanho de efeito pequeno. Ou grupo de controle apresentou maior ganho apenas em consulta. Conclui-se que o IPE básico mostra principalmente os efeitos da flexibilidade cognitiva em crianças com TDAH e dislexia
Percolation model for structural phase transitions in LiHIO mixed crystals
A percolation model is proposed to explain the structural phase transitions
found in LiHIO mixed crystals as a function of the
concentration parameter . The percolation thresholds are obtained from Monte
Carlo simulations on the specific lattices occupied by lithium atoms and
hydrogen bonds. The theoretical results strongly suggest that percolating
lithium vacancies and hydrogen bonds are indeed responsible for the solid
solution observed in the experimental range .Comment: 4 pages, 2 figure
Modeling tourists' personality in recommender systems: how does personality influence preferences for tourist attractions?
Personalization is increasingly being perceived as an important factor for the effectiveness of Recommender Systems (RS). This is especially true in the tourism domain, where travelling comprises emotionally charged experiences, and therefore, the more about the tourist is known, better recommendations can be made. The inclusion of psychological aspects to generate recommendations, such as personality, is a growing trend in RS and they are being studied to provide more personalized approaches. However, although many studies on the psychology of tourism exist, studies on the prediction of tourist preferences based on their personality are limited. Therefore, we undertook a large-scale study in order to determine how the Big Five personality dimensions influence tourists' preferences for tourist attractions, gathering data from an online questionnaire, sent to Portuguese individuals from the academic sector and their respective relatives/friends (n=508). Using Exploratory and Confirmatory Factor Analysis, we extracted 11 main categories of tourist attractions and analyzed which personality dimensions were predictors (or not) of preferences for those tourist attractions. As a result, we propose the first model that relates the five personality dimensions with preferences for tourist attractions, which intends to offer a base for researchers of RS for tourism to automatically model tourist preferences based on their personality.GrouPlanner Project under the
European Regional Development Fund POCI-01-0145-FEDER29178 and by National Funds through the FCT – Fundação para a
Ciência e a Tecnologia (Portuguese Foundation for Science and
Technology) within the Projects UIDB/00319/2020 and
UIDB/00760/202
Balloon Measurements of Cosmic Ray Muon Spectra in the Atmosphere along with those of Primary Protons and Helium Nuclei over Mid-Latitude
We report here the measurements of the energy spectra of atmospheric muons
and of the cosmic ray primary proton and helium nuclei in a single experiment.
These were carried out using the MASS superconducting spectrometer in a balloon
flight experiment in 1991. The relevance of these results to the atmospheric
neutrino anomaly is emphasized. In particular, this approach allows
uncertainties caused by the level of solar modulation, the geomagnetic cut-off
of the primaries and possible experimental systematics to be decoupled in the
comparison of calculated fluxes of muons to measured muon fluxes. The muon
observations cover the momentum and depth ranges of 0.3-40 GeV/c and 5-886
g/cmsquared, respectively. The proton and helium primary measurements cover the
rigidity range from 3 to 100 GV, in which both the solar modulation and the
geomagnetic cut-off affect the energy spectra at low energies.Comment: 31 pages, including 17 figures, simplified apparatus figure, to
appear in Phys. Rev.
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