1,072 research outputs found
Shear viscosity of the quark matter
We discuss shear viscosity of the quark matter by using Kubo formula. The
shear viscosity is calculated in the framework of the quasi-particle RPA for
the Nambu-Jona-Lasinio model. We obtain a formula that the shear viscosity is
expressed by the quadratic form of the quark spectral function in the chiral
symmetric phase. The magnitude of the shear viscosity is discussed assuming the
Breit-Wigner type for the spectral function.Comment: 5 pages, 6 figure
The symmetry energy at subnuclear densities and nuclei in neutron star crusts
We examine how the properties of inhomogeneous nuclear matter at subnuclear
densities depend on the density dependence of the symmetry energy. Using a
macroscopic nuclear model we calculate the size and shape of nuclei in neutron
star matter at zero temperature in a way dependent on the density dependence of
the symmetry energy. We find that for smaller symmetry energy at subnuclear
densities, corresponding to larger density symmetry coefficient L, the charge
number of nuclei is smaller, and the critical density at which matter with
nuclei or bubbles becomes uniform is lower. The decrease in the charge number
is associated with the dependence of the surface tension on the nuclear density
and the density of a sea of neutrons, while the decrease in the critical
density can be generally understood in terms of proton clustering instability
in uniform matter.Comment: 13 pages, 9 figures; Fig. 6 corrected, typos correcte
Tetraquark particle in the string model
We discuss possibility of the existence of tetraquark states made of four
quarks in the string (flux tube) model. The new particle is composed of a
diquark and an anti-diquark which are connected by a color flux. It is shown
that the vibrational and rotational excited states of the string explain some
non- mesons observed experimentally. Moreover we discuss the decay
widths of such tetraquarks with the use of the Schwinger mechanism.Comment: 5 pages, 6 figure
First order phase transition in the quark matter
We investigate chiral phase transition of the first order in the quark
matter. Using the Nambu-Jona-Lasinio model, an equation of state of the quark
matter which is similar to the van der Waals' one is obtained. Moreover the
specific heat and the compressibility are calculated. It is shown that they are
enhanced in the symmetry broken phase, in particular diverge near the
tricritical point.Comment: 6 pages, 7 figure
Latent heat in the chiral phase transition
The chiral phase transition at finite temperature and density is discussed in
the framework of the QCD-like gauge field theory. The thermodynamical potential
is investigated using a variational approach. Latent heat generated in the
first-order phase transition is calculated. It is found that the latent heat is
enhanced near the tricritical point and is more than several hundred MeV per
quark.Comment: 6 pages, 3 figure
Detection and identification of Leishmania species within naturally infected sand flies in the Andean areas of Ecuador by a polymerase chain reaction
The surveillance of prevalent Leishmania and sand fly species in endemic areas is important for prediction of the risk and expansion of leishmaniasis. In this study, we developed a polymerase chain reaction (PCR)-based method for detection of Leishmania minicircle DNA within individual sand flies. Using this method, we detected minicircle DNA in 6 (3.3%) of 183 sand flies, while 5 (3.5%) of 143 were positive for Leishmania promastigotes in the same areas by microscopic examination. The species were identified as Leishmania (Leishmania) mexicana by nucleotide sequencing of the cytochrome b gene. Additionally, all the Leishmania-positive sand flies were identified as Lutzomyia ayacuchensis by the restriction enzyme digestion of the PCR-amplified 18S ribosomal RNA gene fragments. Since this combined method is relatively easy and can process a large number of samples, it will be a powerful tool for the rapid identification of prevalent sand fly and Leishmania species as well as monitoring the infection rate in sand fly populations in endemic areas.Fil: Kato, Hirotomo. Yamaguchi University; JapónFil: Uezato, Hiroshi. University of the Ryukyus; JapónFil: Katakura, Ken. Hokkaido University; JapónFil: Calvopina, Manuel. Kochi University. Kochi Medical School; JapónFil: Marco, Jorge Diego. Kochi University. Kochi Medical School; Japón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Patología Experimental. Universidad Nacional de Salta. Facultad de Ciencias de la Salud. Instituto de Patología Experimental; ArgentinaFil: Barroso, Paola Andrea. Kochi University. Kochi Medical School; Japón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Patología Experimental. Universidad Nacional de Salta. Facultad de Ciencias de la Salud. Instituto de Patología Experimental; ArgentinaFil: Gomez, Eduardo. Universidad Católica de Guayaquil; EcuadorFil: Mimori, Tatsuyuki. Kumamoto University; JapónFil: Korenaga, Masataka. Kochi University. Kochi Medical School; JapónFil: Iwata, Hiroyuki. Yamaguchi University; JapónFil: Nonaka, Shigeo. University ok the Ryukyus; JapónFil: Hashiguchi, Yoshihisa. Kochi University. Kochi Medical School; Japó
Nonclassical rotational behavior at the vicinity of the lamda point
The rotational property of a quantum liquid at the vicinity of the lambda
point is examined. In a liquid helium 4 just above the lambda point, under the
strong influence of Bose statistics, the coherent many-body wave function grows
to an intermediate size between a macroscopic and a microscopic one, which is
of a different nature from the thermal fluctuations. It must reflect in the
rotational properties such as the moment of inertia. Beginning with the bosons
without the condensate, we make a perturbation calculation of its
susceptibility with respect to the repulsive interaction, and examine how, with
decreasing temperature, the growth of the coherent wave function gradually
changes the rotational behavior of a liquid:The moment of inertia slightly
decreases just above the lambda point. This means that at the vicinity of the
lambda point, the mechanical superfluid density does not always agree with the
thermodynamical one.We compare the result to the experiment by Hess and
Fairbank. A new interpretation of the shear viscosity just above the lambda
point is given from this viewpoint.Comment: 12pages, 5figure
Quantum gas-liquid condensation in an attractive Bose gas
Gas-liquid condensation (GLC) in an attractive Bose gas is studied on the
basis of statistical mechanics. Using some results in combinatorial
mathematics, the following are derived: (1) With decreasing temperature, the
Bose-statistical coherence grows in the many-body wave function, which gives
rise to the divergence of the grand partition function prior to Bose-Einstein
condensation. It is a quantum-mechanical analogue to the GLC in a classical gas
(quantum GLC). (2) This GLC is triggered by the bosons with zero momentum.
Compared with the classical GLC, an incomparably weaker attractive force
creates it. For the system showing the quantum GLC, we discuss a cold helium 4
gas at sufficiently low pressure.Comment: 12 pages, 8 figure
Variational Approach to the Chiral Phase Transition in the Linear Sigma Model
The chiral phase transition at finite temperature is investigated in the
linear sigma model, which is regarded as a low energy effective theory of QCD
with three momentum cutoff, in the variational method with the Gaussian
approximation in the functional Schroedinger picture. It is shown that the
Goldstone theorem is retained and the meson pair excitations are automatically
included by taking into account the linear response to the external fields. It
is pointed out that the behavior of chiral phase transition depends on the
three-momentum cutoff, which leads to the careful treatment of the problem.Comment: 14 pages, 5 figures, using PTPTeX cl
Leishmania isoenzyme polymorphisms in Ecuador: Relationships with geographic distribution and clinical presentation
Background: Determinants of the clinical presentation of the leishmaniases are poorly understood but Leishmania species and strain differences are important. To examine the relationship between clinical presentation, species and isoenzyme polymorphisms, 56 Leishmania isolates from distinct presentations of American tegumentary leishmaniasis (ATL) from Ecuador were analyzed.
Methods: Isolates were characterized by multilocus enzyme electrophoresis for polymorphisms of 11 isoenzymes. Patients were infected in four different ecologic regions: highland and lowland jungle of the Pacific coast, Amazonian lowlands and Andean highlands.
Results: Six Leishmania species constituting 21 zymodemes were identified: L. (Viannia) panamensis (21 isolates,
7 zymodemes), L. (V.) guyanensis (7 isolates, 4 zymodemes), L. (V.) braziliensis (5 isolates, 3 zymodemes), L.
(Leishmania) mexicana (11 isolates, 4 zymodemes), L. (L.) amazonensis (10 isolates, 2 zymodemes) and L. (L.) major
(2 isolates, 1 zymodeme). L. panamensis was the species most frequently identified in the Pacific region and was
associated with several clinical variants of cutaneous disease (CL); eight cases of leishmaniasis recidiva cutis (LRC) found in the Pacific highlands were associated with 3 zymodemes of this species. Mucocutaneous leishmaniasis
found only in the Amazonian focus was associated with 3 zymodemes of L. braziliensis. The papular variant of CL,
Uta, found in the Andean highlands was related predominantly with a single zymodeme of L. mexicana.
Conclusion: Our data show a high degree of phenotypic variation within species, and some evidence for associations between specific variants of ATL (i.e. Uta and LRC) and specific Leishmania zymodemes. This study
further defines the geographic distribution of Leishmania species and clinical variants of ATL in Ecuador
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