160 research outputs found
Transition from quintessence to phantom phase in quintom model
Assuming the Hubble parameter is a continuous and differentiable function of
comoving time, we investigate necessary conditions for quintessence to phantom
phase transition in quintom model. For power-law and exponential potential
examples, we study the behavior of dynamical dark energy fields and Hubble
parameter near the transition time, and show that the phantom-divide-line w=-1
is crossed in these models.Comment: LaTeX, 19 pages, four figures, some minor changes in Introduction,
two figures added and the references updated, accepted for publication in
Phys. Rev.
Neutrino oscillation in a space-time with torsion
Using the Einstein-Cartan-Dirac theory, we study the effect of torsion on
neutrino oscillation. We see that torsion cannot induce neutrino oscillation,
but affects it whenever oscillation exists for other reasons. We show that the
torsion effect on neutrino oscillation is as important as the neutrino mass
effect, whenever the ratio of neutrino number density to neutrino energy is
cm /eV, or the number density of the matter is cm.Comment: 7 pages, LaTex,Some typos corrected Journal: Int. J. Mod. Phys. A
(1999) (will be appeared
Determination of heavy metal content of processed fruit products from Tehran's market using ICP- OES: A risk assessment study
Abstract
In this study, the levels of Cd, Hg, Sn, Al, Pb and As of 72 samples (36 samples for fruits juices and 36 samples for fruits canned) of three different brands including of Peach, Orange, Cherry, and Pineapple (18 samples of each fruits) marketed in Tehran, Iran (2015) were evaluated using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) technique. Also, Probabilistic risk assessment (non-carcinogenic and carcinogenic risks) was estimated by models include target hazard quotient (THQ) and cancer risk (CR) in the Monte Carlo Simulation (MCS) model. However, all samples were contaminated with the heavy metals investigated, most of them not surpassed established standards. The range of concentration for Al, Sn, As, Cd, Hg, and Pb as average in fruit juices were reported as 340.62 (65.17â1039.2), 72.33 (49.76â119.4), 3.76 (1.137â18.36), 2.12 (0.89â3.44), 0.351 and 40.86 (27.87â66.1) ÎŒg/kg, respectively. The level of heavy metals measured in different kinds of fruit juices was ranked as AlâŻ>âŻSnâŻ>âŻPbâŻ>âŻAsâŻ>âŻCdâŻ>âŻHg, and for fruits canned this rank was PbâŻ>âŻAlâŻ>âŻSnâŻ>âŻAsâŻ>âŻCdâŻ>âŻHg. The range of concentration for Al, Sn, As, Cd, Hg, and Pb in fruits canned were reported as 361.23 (43.15â1121.2), 101.42 (71.45â141.61), 3.92 (1.279â19.50), 2.78 (1.09â5.56), 0.35 and 690.54 (470.56â910.14) ÎŒg/kg, respectively. The lead (Pb) concentration in 97.22% (35 out of 36 samples) of fruit juices samples surpassed Codex limit (0.05âŻmg/kg) and in all samples of FC was lower than the legal limit of Codex limit (1âŻmg/kg). All of the samples had Tin (Sn) lower than the legal limit of Codex (fruit juices 100âŻmg/kg and FC 250âŻmg/kg). The MCS indicated that the rank order of heavy metals in both adults and children based on THQ was AlâŻ>âŻSnâŻ>âŻAsâŻ>âŻPbâŻ>âŻCdâŻ>âŻHg. The THQ of Al and Sn in the FJ and FC, for both adults, and children, was considerably higher than 1 value. Also, CR of As in both adults and children were higher than 1E-6 value. Although the mean concentration of heavy metal in the FJ and FC was lower than the standard limit, the MCS indicated that adults and children are at considerable non-carcinogenic and carcinogenic risks.
Keywords:
Heavy metals Fruits juice Health risk assessment Monte Carlo simulation Fruit canned Food safety ICPOES
Geometric effects on critical behaviours of the Ising model
We investigate the critical behaviour of the two-dimensional Ising model
defined on a curved surface with a constant negative curvature. Finite-size
scaling analysis reveals that the critical exponents for the zero-field
magnetic susceptibility and the correlation length deviate from those for the
Ising lattice model on a flat plane. Furthermore, when reducing the effects of
boundary spins, the values of the critical exponents tend to those derived from
the mean field theory. These findings evidence that the underlying geometric
character is responsible for the critical properties the Ising model when the
lattice is embedded on negatively curved surfaces.Comment: 16 pages, 6 figures, to appear in J. Phys. A: Math. Ge
Lattice Kinetics of Diffusion-Limited Coalescence and Annihilation with Sources
We study the 1D kinetics of diffusion-limited coalescence and annihilation
with back reactions and different kinds of particle input. By considering the
changes in occupation and parity of a given interval, we derive sets of
hierarchical equations from which exact expressions for the lattice coverage
and the particle concentration can be obtained. We compare the mean-field
approximation and the continuum approximation to the exact solutions and we
discuss their regime of validity.Comment: 24 pages and 3 eps figures, Revtex, accepted for publication in J.
Phys.
Zero-range process with open boundaries
We calculate the exact stationary distribution of the one-dimensional
zero-range process with open boundaries for arbitrary bulk and boundary hopping
rates. When such a distribution exists, the steady state has no correlations
between sites and is uniquely characterized by a space-dependent fugacity which
is a function of the boundary rates and the hopping asymmetry. For strong
boundary drive the system has no stationary distribution. In systems which on a
ring geometry allow for a condensation transition, a condensate develops at one
or both boundary sites. On all other sites the particle distribution approaches
a product measure with the finite critical density \rho_c. In systems which do
not support condensation on a ring, strong boundary drive leads to a condensate
at the boundary. However, in this case the local particle density in the
interior exhibits a complex algebraic growth in time. We calculate the bulk and
boundary growth exponents as a function of the system parameters
Non-local SFT Tachyon and Cosmology
Cosmological scenarios built upon the generalized non-local String Field
Theory and -adic tachyons are examined. A general kinetic operator involving
an infinite number of derivatives is studied as well as arbitrary parameter
. The late time dynamics of just the tachyon around the non-perturbative
vacuum is shown to leave the cosmology trivial. A late time behavior of the
tachyon and the scale factor of the FRW metric in the presence of the
cosmological constant or a perfect fluid with is constructed explicitly
and a possibility of non-vanishing oscillations of the total effective state
parameter around the phantom divide is proven.Comment: 17 pages, LaTeX; v2: JHEP3 class is used, references adde
Accelerating universe from F(T) gravity
It is shown that the acceleration of the universe can be understood by
considering a F(T) gravity models. For these F(T) gravity models, a variant of
the accelerating cosmology reconstruction program is developed. Some explicit
examples of F(T) are reconstructed from the background FRW expansion history.Comment: 13 pages, references adde
Periodic boundary conditions on the pseudosphere
We provide a framework to build periodic boundary conditions on the
pseudosphere (or hyperbolic plane), the infinite two-dimensional Riemannian
space of constant negative curvature. Starting from the common case of periodic
boundary conditions in the Euclidean plane, we introduce all the needed
mathematical notions and sketch a classification of periodic boundary
conditions on the hyperbolic plane. We stress the possible applications in
statistical mechanics for studying the bulk behavior of physical systems and we
illustrate how to implement such periodic boundary conditions in two examples,
the dynamics of particles on the pseudosphere and the study of classical spins
on hyperbolic lattices.Comment: 30 pages, minor corrections, accepted to J. Phys.
Gravitational Geometric Phase in the Presence of Torsion
We investigate the relativistic and non-relativistic quantum dynamics of a
neutral spin-1/2 particle submitted an external electromagnetic field in the
presence of a cosmic dislocation. We analyze the explicit contribution of the
torsion in the geometric phase acquired in the dynamic of this neutral
spinorial particle. We discuss the influence of the torsion in the relativistic
geometric phase. Using the Foldy-Wouthuysen approximation, the non-relativistic
quantum dynamics are studied and the influence of the torsion in the
Aharonov-Casher and He-McKellar-Wilkens effects are discussed.Comment: 14 pages, no figur
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