34,918 research outputs found
Experimental Animal Models of Bruises in Forensic Medicine
Estimating bruise age is a central issue in both human and veterinary forensic medicine. Since 1957 experimental animal models have been developed in order to find an objective way for dating bruises. Experimental bruises have been inflicted in cows, sheep, pigs, rabbits, chickens, mice and rats, and in young and mature animals of both sexes. Although a number of analyses have addressed the timing of bruises, a consensus regarding an optimal method for determining bruise age has not been achieved. In this paper, a review of experimental animal models of bruises is presented
Critical behavior of a one-dimensional monomer-dimer reaction model with lateral interactions
A monomer-dimer reaction lattice model with lateral repulsion among the same
species is studied using a mean-field analysis and Monte Carlo simulations. For
weak repulsions, the model exhibits a first-order irreversible phase transition
between two absorbing states saturated by each different species. Increasing
the repulsion, a reactive stationary state appears in addition to the saturated
states. The irreversible phase transitions from the reactive phase to any of
the saturated states are continuous and belong to the directed percolation
universality class. However, a different critical behavior is found at the
point where the directed percolation phase boundaries meet. The values of the
critical exponents calculated at the bicritical point are in good agreement
with the exponents corresponding to the parity-conserving universality class.
Since the adsorption-reaction processes does not lead to a non-trivial local
parity-conserving dynamics, this result confirms that the twofold symmetry
between absorbing states plays a relevant role in determining the universality
class. The value of the exponent , which characterizes the
fluctuations of an interface at the bicritical point, supports the
Bassler-Brown's conjecture which states that this is a new exponent in the
parity-conserving universality class.Comment: 19 pages, 22 figures, to be published in Phys. Rev
Modeling temporal fluctuations in avalanching systems
We demonstrate how to model the toppling activity in avalanching systems by
stochastic differential equations (SDEs). The theory is developed as a
generalization of the classical mean field approach to sandpile dynamics by
formulating it as a generalization of Itoh's SDE. This equation contains a
fractional Gaussian noise term representing the branching of an avalanche into
small active clusters, and a drift term reflecting the tendency for small
avalanches to grow and large avalanches to be constricted by the finite system
size. If one defines avalanching to take place when the toppling activity
exceeds a certain threshold the stochastic model allows us to compute the
avalanche exponents in the continum limit as functions of the Hurst exponent of
the noise. The results are found to agree well with numerical simulations in
the Bak-Tang-Wiesenfeld and Zhang sandpile models. The stochastic model also
provides a method for computing the probability density functions of the
fluctuations in the toppling activity itself. We show that the sandpiles do not
belong to the class of phenomena giving rise to universal non-Gaussian
probability density functions for the global activity. Moreover, we demonstrate
essential differences between the fluctuations of total kinetic energy in a
two-dimensional turbulence simulation and the toppling activity in sandpiles.Comment: 14 pages, 11 figure
Quantum noise limited and entanglement-assisted magnetometry
We study experimentally the fundamental limits of sensitivity of an atomic
radio-frequency magnetometer. First we apply an optimal sequence of state
preparation, evolution, and the back-action evading measurement to achieve a
nearly projection noise limited sensitivity. We furthermore experimentally
demonstrate that Einstein-Podolsky-Rosen (EPR) entanglement of atoms generated
by a measurement enhances the sensitivity to pulsed magnetic fields. We
demonstrate this quantum limited sensing in a magnetometer utilizing a truly
macroscopic ensemble of 1.5*10^12 atoms which allows us to achieve
sub-femtoTesla/sqrt(Hz) sensitivity.Comment: To appear in Physical Review Letters, April 9 issue (provisionally
Interacting Monomer-Dimer Model with Infinitely Many Absorbing States
We study a modified version of the interacting monomer-dimer (IMD) model that
has infinitely many absorbing (IMA) states. Unlike all other previously studied
models with IMA states, the absorbing states can be divided into two equivalent
groups which are dynamically separated infinitely far apart. Monte Carlo
simulations show that this model belongs to the directed Ising universality
class like the ordinary IMD model with two equivalent absorbing states. This
model is the first model with IMA states which does not belong to the directed
percolation (DP) universality class. The DP universality class can be restored
in two ways, i.e., by connecting the two equivalent groups dynamically or by
introducing a symmetry-breaking field between the two groups.Comment: 5 pages, 5 figure
Nonuniversal Critical Spreading in Two Dimensions
Continuous phase transitions are studied in a two dimensional nonequilibrium
model with an infinite number of absorbing configurations. Spreading from a
localized source is characterized by nonuniversal critical exponents, which
vary continuously with the density phi in the surrounding region. The exponent
delta changes by more than an order of magnitude, and eta changes sign. The
location of the critical point also depends on phi, which has important
implications for scaling. As expected on the basis of universality, the static
critical behavior belongs to the directed percolation class.Comment: 21 pages, REVTeX, figures available upon reques
Dynamic behavior of driven interfaces in models with two absorbing states
We study the dynamics of an interface (active domain) between different
absorbing regions in models with two absorbing states in one dimension;
probabilistic cellular automata models and interacting monomer-dimer models.
These models exhibit a continuous transition from an active phase into an
absorbing phase, which belongs to the directed Ising (DI) universality class.
In the active phase, the interface spreads ballistically into the absorbing
regions and the interface width diverges linearly in time. Approaching the
critical point, the spreading velocity of the interface vanishes algebraically
with a DI critical exponent. Introducing a symmetry-breaking field that
prefers one absorbing state over the other drives the interface to move
asymmetrically toward the unpreferred absorbing region. In Monte Carlo
simulations, we find that the spreading velocity of this driven interface shows
a discontinuous jump at criticality. We explain that this unusual behavior is
due to a finite relaxation time in the absorbing phase. The crossover behavior
from the symmetric case (DI class) to the asymmetric case (directed percolation
class) is also studied. We find the scaling dimension of the symmetry-breaking
field .Comment: 5 pages, 5 figures, Revte
Three-body Thomas-Ehrman shifts of analog states of Ne and N
The lowest-lying states of the Borromean nucleus Ne (O+ +
) and its mirror nucleus N (N+ + ) are compared by using
the hyperspheric adiabatic expansion. Three-body resonances are computed by use
of the complex scaling method. The measured size of O and the low-lying
resonances of F (O+) are first used as constraints to
determine both central and spin-dependent two-body interactions. The
interaction obtained reproduces relatively accurately both experimental
three-body spectra. The Thomas-Ehrman shifts, involving excitation energy
differences, are computed and found to be less than 3% of the total Coulomb
energy shift for all states.Comment: 9 pages, 3 postscript figures, revtex style. To be published in Phys.
Rev.
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