Simulating the Response of Composite Plates to Fire

The present paper introduces a numerical study on the fire behavior of composites during exposure to a heating source at high incident power. A novel numerical model is proposed which is able to simulate the behavior of composite materials in fire environment providing the composites mass loss rate and heat release rate during heating source application. Two commercial software have been selected as platforms for the implementation of the proposed numerical model COMSOL and ANSYS. In COMSOL the model has been implemented by introducing proper field equations, while a macro, written in Ansys Parametric Design Language, has been used to allow the ANSYS FEM code to numerically simulate, by an incremental procedure, all the relevant physical phenomena related to fire. As an application, an experiment on thermal degradation over a laminated composite plate has been numerically simulated and the numerical model has been validated by comparing the COMSOL and Ansys numerical results to experimental literature data in terms of temperature profile over the panel thickness, Mass Loss Rate and Heat Release Rate. An excellent agreement has been found between the obtained numerical results and the experimental test data for both the adopted numerical platforms. However the ANSYS implementation, which showed to be the most effective in terms of accuracy of results and perspectives of applications to complex numerical models, led to the definition of a powerful tool able to assesses the fire performance of composite structures.     

Factors affecting primary care physician participation in Medicare

OBJECTIVES: This study investigates the levels of participation and the relative association of economic and noneconomic factors on primary care physician participation in the Medicare program. METHODS: Demographic information, participation in Medicare, and attitudes toward both the Medicare program and Medicare patients were collected in a written survey mailed to half the primary care physicians in Iowa. Ordinary least squares and logistic regression analyses were conducted to determine factors associated with the percentage of Medicare patients in a practice and the acceptance of all new Medicare patients, respectively. RESULTS: Two thirds of physicians were accepting all new Medicare patients, whereas 16% were accepting no new Medicare patients. Factors associated with having a higher percentage of Medicare patients in a practice were as follows: (1) a larger proportion of Medicare recipients in the county, (2) practice as a general internal medicine physician, (3) more years in practice at the current location, (4) greater enjoyment treating elderly patients, (5) less concern about having too many Medicare patients, and (6) a stronger belief that the Medicare program respects their professional judgment. Physicians less concerned about having too many Medicare patients in their practice and physicians in counties with a higher percentage of Medicare patients were significantly more likely to accept all new Medicare patients. CONCLUSIONS: These results suggest that as Medicare reforms are discussed, careful consideration of the impact of these reforms on noneconomic issues is important to ensure adequate physician participation and access for elderly patients through the Medicare program.     

Can amiodarone pulmonary toxicity be predicted in patients undergoing implantable cardioverter defibrillator implantation?

Implantable cardioverter defibrillator (ICD) implantation is rapidly becoming accepted as primary therapy for malignant ventricular arrhythmias. Many patients undergoing ICD implantation are on concomitant antiarrhythmic drugs to decrease shock frequency, slow tachycardia rate, and suppress supraventricular arrhythmias. Amiodarone is a potent antiarrhythmic agent that is also frequently used in the treatment of patients with refractory ventricular arrhythmias. Ten to forty percent of patients undergoing ICD implantation will also be taking amiodarone. It has been reported to cause pulmonary toxicity in about 5% of patients per year. Acute amiodarone toxicity presenting as adult respiratory distress syndrome has been reported much less frequently. Although perioperative morbidity due to amiodarone has been described, the risk, predictability, and consequences of acute pulmonary toxicity from amiodarone in patients undergoing ICD implantation have not been previously described. We reviewed the records of 99 consecutive patients undergoing ICD implantation at our institution from October 1987 to April 1992. Thirty-nine patients were taking 480 +/- 230 mg of amiodarone (median 400 mg, lower 20th percentile 400 mg, upper 80th percentile 800 mg) for 291 +/- 554 days prior to ICD implantation. Ten patients taking amiodarone developed acute pulmonary toxicity clinically manifesting as diffuse pulmonary infiltrates on chest radiography and adult respiratory distress syndrome with hypoxia (arterial pO2 < 60 mmHg) without evidence of pneumonia or elevated pulmonary capillary wedge pressure (PCW < or = 15 mmHg). Of the 60 patients not taking amiodarone none developed adult respiratory distress syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiovascular responses mediated by protease-activated receptor-2 (PAR-2) and thrombin receptor (PAR-1) are distinguished in mice deficient in PAR-2 or PAR-1

We developed mice deficient in protease-activated receptor-2 (PAR-2) or PAR-1 to explore the pathophysiological functions of these receptors. In this report, we evaluated mean arterial pressure and heart rate (HR) changes in response to PAR-1 or PAR-2 activation in anesthetized wild-type (WT), PAR-1-deficient (PAR-1(-/-)), and PAR-2-deficient (PAR-2(-/-)) mice. In WT mice, TFLLRNPNDK, a PAR-1 selective activating peptide, caused hypotension and HR decreases at 1 micromol/kg. TFLLRNPNDK also caused secondary hypertension following L-NAME pretreatment. These responses were absent in PAR-1(-/-) mice. In WT mice, SLIGRL, a PAR-2 selective activating peptide, caused hypotension without changing HR at 0.3 micromol/kg. SLIGRL did not induce hypertension following Nomega-nitrol-arginine-methyl ester-HCl (L-NAME). The response to SLIGRL was absent in PAR-2(-/-) mice. SFLLRN, a nonselective receptor activating peptide caused hypotension and HR decreases in WT mice at 0.3 micromol/kg, as well as secondary hypertension following L-NAME. SFLLRN still induced hypotension in PAR-1(-/-) mice, but HR decrease and secondary hypertension following L-NAME were absent. The hypotensive and bradycardic responses to SFLLRN and TFLLRNPNDK in PAR-2(-/-) mice were accentuated compared with WT mice. By using mouse strains deficient in either PAR-1 or PAR-2, we confirmed the in vivo specificity of TFLLRNPNDK and SLIGRL as respective activating peptides for PAR-1 and PAR-2, and the distinct hemodynamic responses mediated by activation of PAR-1 or PAR-2. Moreover, the accentuated response to PAR-1 activation in PAR-2-deficient mice suggests a compensatory response and potential receptor cross-talk.     

Eu Atomic Motion in EuSr2Cu3O7?δ and EuBa2Cu3O7?δ: A Comparative M?ssbauer Study

We present a comparative Mössbauer study of the ¹⁵¹Eu motions in the nonsuperconducting and superconducting cuprates EuSr₂Cu₃O_7– (ESCO) and EuBa₂Cu₃O_7– (EBCO), respectively, with the aim of investigating atomic-motion anharmonicities in these materials. In this study, a comparison with the results of a similar analysis of powdered samples of EBCO having oriented grains is also performed. We show that the Eu ion in ESCO, as well as in the common EBCO cuprates, does not move in a parabolic potential, but in a potential with a flat bottom. Moreover, for ESCO the flat part is about 1.5 times larger than for EBCO.     

Evaluating and improving the content access in KAD

We analyze in detail the content retrieval process in kad. kad implements content search (publish and retrieval) functions that use the Kademlia Distributed Hash Table for content routing. Node churn is quite common in peer-to-peer systems and results in information loss and stale routing table entries. To deal with node churn, kad issues parallel route requests and publishes multiple redundant copies of each piece of information. We identify the key design parameters in kad and present an analytical model to evaluate the impact of changes in the values of these parameters on the overall lookup latency and message overhead. Extensive measurements of the lookup performance using an instrumented client allow us to validate the model. The overall lookup latency is in most cases 5 s or larger. We elucidate the cause for such high lookup latencies and propose an improved scheme that significantly decreases the overall lookup latency without increasing the overhead.     

Postfailure Mechanics of Landslides: Laboratory Investigation of Flowslides in Pyroclastic Soils

Of all landslides, subaerial flowslides are the most dangerous. According to the literature, flowslides in saturated granular deposits are caused by static liquefaction induced by loss of stability. However, the catastrophic flowslides that occurred on steep slopes in Campania (southern Italy) in 1998, 1999, and 2005 were triggered by rainwater infiltration into shallow deposits of pyroclastic soils, which were initially unsaturated. Starting from the experience collected during the investigations of some of these landslides, the writers consider flowslide evolution as a result of a mechanical chain process characterized by saturation increase due to rainwater infiltration, mechanical degradation, volumetric collapse, and static liquefaction, culminating in complete fluidization of the soil. In the paper this chain process is investigated through wetting tests both in suction controlled triaxial apparatuses and in a well-equipped small scale slope model.     

On the Ontological Status of Plans and Norms

This article describes an ontological model of norms. The basic assumption is that a substantial part of a legal system is grounded on the concept of agency. Since a legal system aims at regulating a society, then its goal can be achieved only by affecting the behaviour of the members of the society. We assume that a society is made up of agents (which can be individuals, institutions, software programs, etc.), that agents have beliefs, goals and preferences, and that they commit to intentions in order to choose a line of behaviour. The role of norms, within a legal system, is to specify how and when the chosen behaviour agrees with the basic principles of the legal system. In this article, we show how a model based on plans can be the basis for the ontological representation of norms, which are expressed as constraints on the possible plans an agent may choose to guide its behaviour. Moreover, the paper describes how the proposed model can be linked to the upper level of a philosophically well-founded ontology (DOLCE); in this way, the model is set in a wider perspective, which opens the way to further developments.     

Selenocarbamates As a Prodrug-Based Approach to Carbonic Anhydrase Inhibition

A study on the activity of selenocarbamates as a novel chemotype acting as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors is reported. Undergoing CA-mediated hydrolysis, selenocarbamates release selenolates behaving as zinc binding groups and effectively inhibiting CAs. A series of selenocarbamates characterised by high molecular diversity and complexity have been studied against different human CA isoforms such as hCA I, II, IX and XII. Selenocarbamates behave as masked selenols with potential biological applications as prodrugs for CAs inhibition-based strategies. X-ray studies provided insights into the binding mode of this novel class of CA inhibitors.