18,216 research outputs found
The Coester Line in Relativistic Mean Field Nuclear Matter
The Walecka model contains essentially two parameters that are associated
with the Lorentz scalar (S) and vector (V) interactions. These parameters are
related to a two-body interaction consisting of S and V, imposing the condition
that the two-body binding energy is fixed. We have obtained a set of different
values for the nuclear matter binding energies at equilibrium densities. We
investigated the existence of a linear correlation between and ,
claimed to be universal for nonrelativistic systems and usually known as the
Coester line, and found an approximate linear correlation only if remains
constant. It is shown that the relativistic content of the model, which is
related to the strength of , is responsible for the shift of the Coester
line to the empirical region of nuclear matter saturation.Comment: 7 pages, 5 figure
Mapping the train model for earthquakes onto the stochastic sandpile model
We perform a computational study of a variant of the ``train'' model for
earthquakes [PRA 46, 6288 (1992)], where we assume a static friction that is a
stochastic function of position rather than being velocity dependent. The model
consists of an array of blocks coupled by springs, with the forces between
neighbouring blocks balanced by static friction. We calculate the probability,
P(s), of the occurrence of avalanches with a size s or greater, finding that
our results are consistent with the phenomenology and also with previous models
which exhibit a power law over a wide range. We show that the train model may
be mapped onto a stochastic sandpile model and study a variant of the latter
for non-spherical grains. We show that, in this case, the model has critical
behaviour only for grains with large aspect ratio, as was already shown in
experiments with real ricepiles. We also demonstrate a way to introduce
randomness in a physically motivated manner into the model.Comment: 14 pages and 6 figures. Accepted in European Physical Journal
A Complex Case of Cholestasis in a Patient with ABCB4 and ABCB11 Mutations
The low-phospholipid-associated cholelithiasis (LPAC) syndrome is a form of symptomatic cholelithiasis occurring in young adults, characterized by recurrence of symptoms after cholecystectomy and presence of hepatolithiasis. The case refers to a healthy 39-year-old Caucasian male who presented with abdominal pain and jaundice. His blood tests showed conjugated hyperbilirubinemia and elevated liver enzymes (total bilirubin 6.65 mg/dL, γ-glutamyltransferase 699 IU/L) and abdominal computed tomography revealed dilation of common bile duct and left intrahepatic ducts. Magnetic resonance cholangiopancreatography identified choledocholithiasis, retrieved by endoscopic retrograde cholangiopancreatography, after which there was a worsening of jaundice (total bilirubin 23 mg/dL), which persisted for several weeks, possibly due to ciprofloxacin toxicity. After an extensive workup including liver biopsy, the identification of two foci of hepatolithiasis on reevaluation abdominal ultrasound raised the hypothesis of LPAC syndrome and the patient was started on ursodeoxycholic acid, with remarkable improvement. Genetic testing identified the mutation c.1954A>G (p.Arg652Gly) in ABCB4 gene (homozygous) and c.1331T>C (p.Val444Ala) in ABCB11 gene (heterozygous). In conclusion, we describe the unique case of an adult male with choledocholithiasis, hepatolithiasis, and persistent conjugated hyperbilirubinemia after retrieval of stones, fulfilling the criteria for LPAC syndrome and with possible superimposed drug-induced liver injury, in whom ABCB4 and ABCB11 mutations were found, both of which had not been previously described in association with LPAC.info:eu-repo/semantics/publishedVersio
Clustering Properties of Dynamical Dark Energy Models
We provide a generic but physically clear discussion of the clustering
properties of dark energy models. We explicitly show that in quintessence-type
models the dark energy fluctuations, on scales smaller than the Hubble radius,
are of the order of the perturbations to the Newtonian gravitational potential,
hence necessarily small on cosmological scales. Moreover, comparable
fluctuations are associated with different gauge choices. We also demonstrate
that the often used homogeneous approximation is unrealistic, and that the
so-called dark energy mutation is a trivial artifact of an effective, single
fluid description. Finally, we discuss the particular case where the dark
energy fluid is coupled to dark matter.Comment: 5 page
Exactly Solvable Models of Interacting Spin-s Particles in one-dimension
We consider the exact solution of a many-body problem of spin- particles
interacting through an arbitrary U(1) invariant factorizable -matrix. The
solution is based on a unified formulation of the quantum inverse scattering
method for an arbitrary -dimensional monodromy matrix. The respective
eigenstates are shown to be given in terms of creation fields by a general
new recurrence relation. This allows us to derive the spectrum and the
respective Bethe ansatz equations.Comment: 10 pages, plain late
Tipos nomenclaturais de Crhysobalanaceae depositados no acervo de Herbário IAN (Embrapa Amazônia Oriental) - Belém, PA, Brasil.
Cosmic String Network Evolution in arbitrary Friedmann-Lemaitre models
We use the velocity-dependent one-scale model by Martins & Shellard to
investigate the evolution of a GUT long cosmic string network in arbitrary
Friedmann-Lemaitre models. Four representative models are used to show that in
general there is no scaling solution. The implications for structure formation
are briefly discussed.Comment: 8 pages, 4 postscript figures included, submitted to Phys. Rev.
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