22,699 research outputs found
The concept of social pharmacy
The 13th International Social Pharmacy Workshop will be held in Malta in July 2004. The Social Pharmacy Workshops are international conferences for research in social and behavioural pharmacy. Meetings are held every second year and participation has grown steadily since the first Workshop was held in Helsinki, Finland, in 1980. Following the successful 2002 conference in Sydney, Australia, the 2004 meeting in Malta will be the first one held in the Mediterranean area!peer-reviewe
Lattice vibrations and structural instability in Cesium near the cubic to tetragonal transition
Under pressure cesium undergoes a transition from a high-pressure fcc phase
(Cs-II) to a collapsed fcc phase (Cs-III) near 4.2GPa. At 4.4GPa there follows
a transition to the tetragonal Cs-IV phase. In order to investigate the lattice
vibrations in the fcc phase and seek a possible dynamical instability of the
lattice, the phonon spectra of fcc-Cs at volumes near the III-IV transition are
calculated using Savrasov's density functional linear-response LMTO method.
Compared with quasiharmonic model calculations including non-central
interatomic forces up to second neighbours, at the volume (
is the experimental volume of bcc-Cs with =6.048{\AA}), the
linear-response calculations show soft intermediate wavelength
phonons. Similar softening is also observed for
short wavelength and phonons and intermediate
wavelength phonons. The Born-von K\'{a}rm\'{a}n analysis of
dispersion curves indicates that the interplanar force constants exhibit
oscillating behaviours against plane spacing and the large softening of
intermediate wavelength phonons results from a
negative (110)-interplanar force-constant . The frequencies of the
phonons with around 1/3 become imaginary
and the fcc structure becomes dynamically unstable for volumes below .
It is suggested that superstructures corresponding to the
soft mode should be present as a precursor of tetragonal Cs-IV structure.Comment: 12 pages, 5 figure
Transitions in non-conserving models of Self-Organized Criticality
We investigate a random--neighbours version of the two dimensional
non-conserving earthquake model of Olami, Feder and Christensen [Phys. Rev.
Lett. {\bf 68}, 1244 (1992)]. We show both analytically and numerically that
criticality can be expected even in the presence of dissipation. As the
critical level of conservation, , is approached, the cut--off of the
avalanche size distribution scales as . The
transition from non-SOC to SOC behaviour is controlled by the average branching
ratio of an avalanche, which can thus be regarded as an order
parameter of the system. The relevance of the results are discussed in
connection to the nearest-neighbours OFC model (in particular we analyse the
relevance of synchronization in the latter).Comment: 8 pages in latex format; 5 figures available upon reques
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
MCMC Exploration of Supermassive Black Hole Binary Inspirals
The Laser Interferometer Space Antenna will be able to detect the inspiral
and merger of Super Massive Black Hole Binaries (SMBHBs) anywhere in the
Universe. Standard matched filtering techniques can be used to detect and
characterize these systems. Markov Chain Monte Carlo (MCMC) methods are ideally
suited to this and other LISA data analysis problems as they are able to
efficiently handle models with large dimensions. Here we compare the posterior
parameter distributions derived by an MCMC algorithm with the distributions
predicted by the Fisher information matrix. We find excellent agreement for the
extrinsic parameters, while the Fisher matrix slightly overestimates errors in
the intrinsic parameters.Comment: Submitted to CQG as a GWDAW-10 Conference Proceedings, 9 pages, 5
figures, Published Versio
Enhancement of VCO Linearity and Phase Noise by Implementing Frequency Locked Loop
This paper investigates the on-chip implementation of a frequency locked loop (FLL) over a VCO that decreases the phase noise and linearizes the transfer function. Implementation of the FLL inside a PLL is also investigated and a possible application is highlighted. Design of a special kind of low noise frequency detector without a reference frequency (frequency-to-voltage converter), which is the most critical component of the FLL, is also presented in a 0.25 ¿m BiCMOS process. Linearization and approximately 15 dBc/Hz phase noise suppression is demonstrated over a moderate phase noise LC VCO with a center frequency of 10 GHz
Dynamics of Fractal Solids
We describe the fractal solid by a special continuous medium model. We
propose to describe the fractal solid by a fractional continuous model, where
all characteristics and fields are defined everywhere in the volume but they
follow some generalized equations which are derived by using integrals of
fractional order. The order of fractional integral can be equal to the fractal
mass dimension of the solid. Fractional integrals are considered as an
approximation of integrals on fractals. We suggest the approach to compute the
moments of inertia for fractal solids. The dynamics of fractal solids are
described by the usual Euler's equations. The possible experimental test of the
continuous medium model for fractal solids is considered.Comment: 12 pages, LaTe
- …