Ergodic Properties of Microcanonical Observables

The problem of the existence of a Strong Stochasticity Threshold in the FPU-beta model is reconsidered, using suitable microcanonical observables of thermodynamic nature, like the temperature and the specific heat. Explicit expressions for these observables are obtained by exploiting rigorous methods of differential geometry. Measurements of the corresponding temporal autocorrelation functions locate the threshold at a finite value of the energy density, that results to be indipendent of the number of degrees of freedom.Comment: 19 pages, 6 figure

Empedocles and the Other Physiologists in Aristotle’s Physics II 8

In this paper I propose to show: 1) that in Phys. II 8 Aristotle takes Empedocles as a paradigm for a theoretical position common to all philosophers who preceded him: the view that materialism implies a mechanistic explanation of natural becoming; and 2) that, since Empe­docles is regarded as a philosopher who clearly expresses the position of all mechanistic materialists, Aristotle builds his teleological arguments precisely to refute him. Indeed, Aristotle believes that refuting the argu­ments of Empedocles – the champion of mechanism – means refut­ing the mechanistic theory itself. In order to illustrate this point, I will discuss some passages from Phys. II 8, while also turning to consider the Neoplatonic commentators on Aristotle’s Physics. I will then endeav­our to explain why in 198b19 ff. Aristotle formulates the argument of rain, which has attracted so much attention from scholars of the Phys­ics: I will consider whether Aristotle believes that rain serves a purpose, contrary to what he claims with regard to meteorological phenomena in Meteorologica

Intraoperative redosing of cefazolin and risk for surgical site infection in cardiac surgery.

Intraoperative redosing of prophylactic antibiotics is recommended for prolonged surgical procedures, although its efficacy has not been assessed. We retrospectively compared the risk of surgical site infections in 1,548 patients who underwent cardiac surgery lasting >240 min after preoperative administration of cefazolin prophylaxis. The overall risk of surgical site infection was similar among patients with (43 [9.4%] of 459) and without (101 [9.3%] of 1,089) intraoperative redosing (odds ratio [OR] 1.01, 95% confidence interval [CI] 0.70-1.47). However, redosing was beneficial in procedures lasting >400 min: infection occurred in 14 (7.7%) of 182 patients with redosing and in 32 (16.0%) of 200 patients without (adjusted OR 0.44, 95% CI 0.23-0.86). Intraoperative redosing of cefazolin was associated with a 16% reduction in the overall risk for surgical site infection after cardiac surgery, including procedures lasting <240 min

Achieving a given reflectance for unpolarized light by controlling the incidence angle and the thickness of a transparent thin film on an absorbing substrate: application to energy equipartition in the four-detector photopolarimeter

At a given wavelength λ we determine all possible solution pairs (ϕ, ζ) of the incidence angle ϕ and the thickness ζ of a transparent thin film on an absorbing substrate that achieve a given unpolarized light reflectance Ru. The trajectory of the point that represents a solution pair in the ζ, ϕ plane depends on the optical properties of the film and substrate and on whether Ru is greater than or less than the normal-incidence reflectance -R0 of the bare substrate. When Ru \u3e - R0, the specified reflectance is achieved over a limited range of ϕ. At the least possible incidence angle, the film thickness is ≈ ⅛ th wave. As an application we consider SiO2 films on Si detectors that produce Ru. = 0.75, 0.6667, and 0.50 at λ = 337 and 633 nm. If the first three detectors of the four-detector photopolarimeter (FDP) are coated to have these reflectance levels, with the reflectance diminishing in the direction of propagation of the light beam, and the last detector is antireflection coated (e.g., with a quarter-wave Si3N4 layer), equipartition of energy among the four detectors is accomplished for incident unpolarized light. Such a condition is desirable in the operation of the FDP. The ellipsometric parameters of the coated surfaces and the FDP instrument matrix are also calculated

Achieving a given reflectance for unpolarized light by controlling the incidence angle and the thickness of a transparent thin film on an absorbing substrate: application to energy equipartition in the four-detector photopolarimeter

At a given wavelength λ we determine all possible solution pairs (ϕ, ζ) of the incidence angle ϕ and the thickness ζ of a transparent thin film on an absorbing substrate that achieve a given unpolarized light reflectance Ru. The trajectory of the point that represents a solution pair in the ζ, ϕ plane depends on the optical properties of the film and substrate and on whether Ru is greater than or less than the normal-incidence reflectance -R0 of the bare substrate. When Ru \u3e - R0, the specified reflectance is achieved over a limited range of ϕ. At the least possible incidence angle, the film thickness is ≈ ⅛ th wave. As an application we consider SiO2 films on Si detectors that produce Ru. = 0.75, 0.6667, and 0.50 at λ = 337 and 633 nm. If the first three detectors of the four-detector photopolarimeter (FDP) are coated to have these reflectance levels, with the reflectance diminishing in the direction of propagation of the light beam, and the last detector is antireflection coated (e.g., with a quarter-wave Si3N4 layer), equipartition of energy among the four detectors is accomplished for incident unpolarized light. Such a condition is desirable in the operation of the FDP. The ellipsometric parameters of the coated surfaces and the FDP instrument matrix are also calculated

Duality in quantum transport models

We develop the \u2018duality approach\u2019, that has been extensively studied for classical models of transport, for quantum systems in contact with a thermal \u2018Lindbladian\u2019 bath. The method provides (a) a mapping of the original model to a simpler one, containing only a few particles and (b) shows that any dynamic process of this kind with generic baths may be mapped onto one with equilibrium baths. We exemplify this through the study of a particular model: the quantum symmetric exclusion process introduced in [1]. As in the classical case, the whole construction becomes intelligible by considering the dynamical symmetries of the problem

Photopolarimeter based on planar grating diffraction

A division-of-amplitude photopolarimeter (DOAP) is described that employs a diffraction grating in the conventional spectrometer orientation with the grating grooves normal to the plane of incidence. Four coplanar diffracted orders are used for polarimetric analysis to determine all four Stokes parameters of incident light simultaneously and virtually instantaneously (with the speed being determined solely by the photodetectors and their associated electronics); a fifth order is used for alignment by autocollimation or by use of a position-sensing quadrant detector. To sensitize the instrument for the +45° and -45° azimuths of incident linearly polarized light and for the handedness of incident circular polarization (i.e., for the third and fourth Stokes parameters), we insert two linear polarizers in two diffracted orders with their transmission axes inclined at appropriate angles with respect to the plane of incidence. The calibration and testing of an instrument of this type that uses an Al-coated 600-groove/mm holographic grating at 632.8-nm wavelength are reported as an example

Estimating the burden of malaria in Senegal : Bayesian zero-inflated binomial geostatistical modeling of the MIS 2008 data

The Research Center for Human Development in Dakar (CRDH) with the technical assistance of ICF Macro and the National Malaria Control Programme (NMCP) conducted in 2008/2009 the Senegal Malaria Indicator Survey (SMIS), the first nationally representative household survey collecting parasitological data and malaria-related indicators. In this paper, we present spatially explicit parasitaemia risk estimates and number of infected children below 5 years. Geostatistical Zero-Inflated Binomial models (ZIB) were developed to take into account the large number of zero-prevalence survey locations (70%) in the data. Bayesian variable selection methods were incorporated within a geostatistical framework in order to choose the best set of environmental and climatic covariates associated with the parasitaemia risk. Model validation confirmed that the ZIB model had a better predictive ability than the standard Binomial analogue. Markov chain Monte Carlo (MCMC) methods were used for inference. Several insecticide treated nets (ITN) coverage indicators were calculated to assess the effectiveness of interventions. After adjusting for climatic and socio-economic factors, the presence of at least one ITN per every two household members and living in urban areas reduced the odds of parasitaemia by 86% and 81% respectively. Posterior estimates of the ORs related to the wealth index show a decreasing trend with the quintiles. Infection odds appear to be increasing with age. The population-adjusted prevalence ranges from 0.12% in Thille-Boubacar to 13.1% in Dabo. Tambacounda has the highest population-adjusted predicted prevalence (8.08%) whereas the region with the highest estimated number of infected children under the age of 5 years is Kolda (13940). The contemporary map and estimates of malaria burden identify the priority areas for future control interventions and provide baseline information for monitoring and evaluation. Zero-Inflated formulations are more appropriate in modeling sparse geostatistical survey data, expected to arise more frequently as malaria research is focused on eliminatio

Generalized minority games with adaptive trend-followers and contrarians

We introduce a simple extension of the minority game in which the market rewards contrarian (resp. trend-following) strategies when it is far from (resp. close to) efficiency. The model displays a smooth crossover from a regime where contrarians dominate to one where trend-followers dominate. In the intermediate phase, the stationary state is characterized by non-Gaussian features as well as by the formation of sustained trends and bubbles.Comment: 4 pages, 6 figure