183 research outputs found
Geographical Variation in Medication Prescriptions: A Multiregional Drug-Utilization Study
Background: Studies have emphasized the importance of geographical factors and general practitioner (GP) characteristics in influencing drug prescriptions. Objectives: To: (i) ascertain the prevalence rate (PR) of use of drugs in six therapeutic categories used for chronic conditions; (ii) assess how geographical characteristics and GP characteristics may influence drug prescribing. Methods: This study is part of the EDU.RE.DRUG Project, a national collaborative project founded by Italian Medicine Agency (AIFA). Cross-sectional analyses were undertaken employing the pharmacy-claim databases of four local health units (LHUs) located in two Italian regions: Lombardy and Campania. Six drug categories were evaluated: proton-pump inhibitors; antibiotics; respiratory-system drugs; statins; agents acting on the renin 12angiotensin system; psychoanaleptic drugs. The PR was estimated according to drug categories at the LHU level. A linear multivariate regression analysis was undertaken to evaluate the association between the PR and geographical area, age and sex of GPs, number of patients, and percentage of patients aged >65 per GP. Results: LHUs in Campania showed a PR that was significantly higher than that in Lombardy. Antibiotics showed the highest PR in all the LHUs assessed, ranging from 32.5% in Lecco (Lombardy) to 59.7% in Naples-2 (Campania). Multivariate linear regression analysis confirmed the association of the PR with geographical area for all drug categories. Being located in Campania increased the possibility of receiving a drug prescription from the categories considered, with estimates more marked for antibiotics, proton-pump-inhibitors, and respiratory-system drugs. Conclusions: This study provides information about the PR of medications used for treating common and costly conditions in Italy and highlighted a significant geographical variation. These insights could help to develop area-specific strategies to optimize prescribing behavior
Simulations for dynamics of granular mixtures in a rotating drum
Abstract We present a simple model and carry out simulations to investigate the dynamics of mixtures of granular material within a rotating drum. On the basis of the commonly held belief (supported by considerable experimental evidence) that segregation is due to motion of particles on the active layer, the bulk playing little or no role, we introduce a 2d lattice gas model which takes into account the rotational frequency, frictional forces, and the gravitational field, and represents segregation tendencies via activated effective grain-grain interactions. Our results include the onset of segregation perpendicular to the drum axis, the appearance and subsequent coarsening of bands and peculiarities of the effects of periodic modulation of the drum. Observed effects such as the segregation of rougher (smoother) particles into the bellies (necks) of the modulation are reproduced by our simulation
Fixed Versus Free Combinations of Antihypertensive Drugs: Analyses Of Real-World Data Of Persistence With Therapy In Italy
Purpose: To analyse the pattern of use and cost of antihypertensive drugs in new users in an Italian population, and explore the patient/treatment factors associated with the risk of therapy discontinuation. Patients and methods: In this retrospective study, information was collected from a population-based electronic primary-care database. Persistence with medication use 1 year from therapy initiation was evaluated for each user using the gap method. Each new user was classified according to his/her pattern of use as: \u201ccontinuer\u201d, \u201cdiscontinuer\u201d \u201cswitching\u201d or \u201cadd-on\u201d. A Cox regression model was used to analyse the factors influencing therapy discontinuation. Primary-care costs comprised specialists\u2019 visits, diagnostic procedures and pharmacologic therapies. Results: Among 14,999 subjects included in persistence analyses, 55.1% of cases initially started on monotherapy were classified as discontinuers vs 36.5% of cases taking combination therapy (42.3% vs 32.7%, respectively, for free and fixed combinations, P < 0.01). Old age, high cardiovascular risk and being in receipt of fixed-combination therapy were associated with greater persistence. Overall, the primary-care cost/person/year of hypertension management was 3c\u20ac95.3 (IQR, 144.9). The monotherapy cost was \u20ac88 per patient (IQR, 132.9), and that for combination therapy was \u20ac151\ub1148.3. The median cost/patient with a fixed combination was lower than that for a free combination (\u20ac98.4 (IQR, 155.3) and \u20ac154.9 (IQR, 182.6), respectively). Conclusion: The initial type of therapy prescribed influences persistence. Prescribing fixed combinations might be a good choice as initial therapy
Study of the one-dimensional off-lattice hot-monomer reaction model
Hot monomers are particles having a transient mobility (a ballistic flight)
prior to being definitely absorbed on a surface. After arriving at a surface,
the excess energy coming from the kinetic energy in the gas phase is dissipated
through degrees of freedom parallel to the surface plane. In this paper we
study the hot monomer-monomer adsorption-reaction process on a continuum
(off-lattice) one-dimensional space by means of Monte Carlo simulations. The
system exhibits second-order irreversible phase transition between a reactive
and saturated (absorbing) phases which belong to the directed percolation (DP)
universality class. This result is interpreted by means of a coarse-grained
Langevin description which allows as to extend the DP conjecture to transitions
occurring in continuous media.Comment: 13 pages, 5 figures, final version to appear in J. Phys.
Application of a renormalization group algorithm to nonequilibrium cellular automata with one absorbing state
We improve a recently proposed dynamically driven renormalization group
algorithm for cellular automata systems with one absorbing state, introducing
spatial correlations in the expression for the transition probabilities. We
implement the renormalization group scheme considering three different
approximations which take into account correlations in the stationary
probability distribution. The improved scheme is applied to a probabilistic
cellular automaton already introduced in the literature.Comment: 7 pages, 4 figures, to be published in Phys. Rev.
Maximal height statistics for 1/f^alpha signals
Numerical and analytical results are presented for the maximal relative
height distribution of stationary periodic Gaussian signals (one dimensional
interfaces) displaying a 1/f^alpha power spectrum. For 0<alpha<1 (regime of
decaying correlations), we observe that the mathematically established limiting
distribution (Fisher-Tippett-Gumbel distribution) is approached extremely
slowly as the sample size increases. The convergence is rapid for alpha>1
(regime of strong correlations) and a highly accurate picture gallery of
distribution functions can be constructed numerically. Analytical results can
be obtained in the limit alpha -> infinity and, for large alpha, by
perturbation expansion. Furthermore, using path integral techniques we derive a
trace formula for the distribution function, valid for alpha=2n even integer.
From the latter we extract the small argument asymptote of the distribution
function whose analytic continuation to arbitrary alpha > 1 is found to be in
agreement with simulations. Comparison of the extreme and roughness statistics
of the interfaces reveals similarities in both the small and large argument
asymptotes of the distribution functions.Comment: 17 pages, 8 figures, RevTex
Numerical study of a first-order irreversible phase transition in a CO+NO catalyzed reaction model
The first-order irreversible phase transitions (IPT) of the Yaldran-Khan
model (Yaldran-Khan, J. Catal. 131, 369, 1991) for the CO+NO reaction is
studied using the constant coverage (CC) ensemble and performing epidemic
simulations. The CC method allows the study of hysteretic effects close to
coexistence as well as the location of both the upper spinodal point and the
coexistence point. Epidemic studies show that at coexistence the number of
active sites decreases according to a (short-time) power law followed by a
(long-time) exponential decay. It is concluded that first-order IPT's share
many characteristic of their reversible counterparts, such as the development
of short ranged correlations, hysteretic effects, metastabilities, etc.Comment: 17 pages, 10 figure
Phase Transitions and Oscillations in a Lattice Prey-Predator Model
A coarse grained description of a two-dimensional prey-predator system is
given in terms of a 3-state lattice model containing two control parameters:
the spreading rates of preys and predators. The properties of the model are
investigated by dynamical mean-field approximations and extensive numerical
simulations. It is shown that the stationary state phase diagram is divided
into two phases: a pure prey phase and a coexistence phase of preys and
predators in which temporal and spatial oscillations can be present. The
different type of phase transitions occuring at the boundary of the prey
absorbing phase, as well as the crossover phenomena occuring between the
oscillatory and non-oscillatory domains of the coexistence phase are studied.
The importance of finite size effects are discussed and scaling relations
between different quantities are established. Finally, physical arguments,
based on the spatial structure of the model, are given to explain the
underlying mechanism leading to oscillations.Comment: 11 pages, 13 figure
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
Nonextensivity of the cyclic Lattice Lotka Volterra model
We numerically show that the Lattice Lotka-Volterra model, when realized on a
square lattice support, gives rise to a {\it finite} production, per unit time,
of the nonextensive entropy . This finiteness only occurs for for the growth mode
(growing droplet), and for for the one (growing stripe). This
strong evidence of nonextensivity is consistent with the spontaneous emergence
of local domains of identical particles with fractal boundaries and competing
interactions. Such direct evidence is for the first time exhibited for a
many-body system which, at the mean field level, is conservative.Comment: Latex, 6 pages, 5 figure
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