Exchange reactions of poly(arylene ether ketone) dithioketals with aliphatic diols: formation and deprotection of poly(arylene ether ketal)s

The dithioketal derivatives of industrially important, semi-crystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential dithioketalization, dithioketal-ketal exchange, ketal hydrolysis, and re-dithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials

Some issues when using Fourier analysis for the extraction of modal parameters

It is sometimes necessary to determine the manner in which structures deteriorate with respect to time; for instance when quantifying a material's ability to withstand sustained dynamic loads. In such cases, it is well established that loss of structural integrity is reflected by variations in modal characteristics such as stiffness. This paper addresses some practical limitations of Fourier analysis with respect to temporal resolution and the uncertainties associated with extracting variations in modal parameters. The statistical analysis of numerous numerical experiments shows how techniques, such as data overlapping and zero-padding, can be used to improve the sensitivity of modal parameter extraction

Asymptotic Karlin-Rubin's Theorem with Application to Signal Detection in a Subspace Cone

International audienc

Mechanical evaluation of a fire retardant through-thickness reinforced sandwich structure for marine applications

One of the main restrictions in adopting polymer composite materials for primary and secondary structural applications in marine vessels over 50 meters in length is concerns regarding fire retardancy and also a lack of design guidelines in general. The aim of this study is to evaluate the edgewise compression strength and core-shear strength of a fire retardant sandwich structure reinforced with through thickness composite ‘bridges’ under ambient conditions. These properties are important for structural components subjected to in-plane loads such as bulkheads. Core shear strength of the through-thickness reinforced sandwich far exceeded non-reinforced sandwich. However, edgewise compression strength and stiffness of the reinforced case was found to be similar to the unreinforced case

Performance metrics for the evaluation of hyperspectral chemical identification systems

Remote sensing of chemical vapor plumes is a difficult but important task for many military and civilian applications. Hyperspectral sensors operating in the long-wave infrared regime have well-demonstrated detection capabilities. However, the identification of a plume’s chemical constituents, based on a chemical library, is a multiple hypothesis testing problem which standard detection metrics do not fully describe. We propose using an additional performance metric for identification based on the so-called Dice index. Our approach partitions and weights a confusion matrix to develop both the standard detection metrics and identification metric. Using the proposed metrics, we demonstrate that the intuitive system design of a detector bank followed by an identifier is indeed justified when incorporating performance information beyond the standard detection metrics.United States. Defense Threat Reduction Agency (Air Force contract FA8721-05-C-0002

La escuela atrapada en la red : Algunos signos de su parálisis

El presente trabajo intentará explorar algunos interrogantes sobre la cultura escolar ¿es posible incluir en la escuela las nuevas tecnologías de la información y la comunicación? ¿Es solo cuestión de aparatos? ¿En qué consiste la mass-mediatización de la cultura? ¿La escuela puede procesar el pasaje de la cultura de la espera a la mass-mediática? ¿Estas nuevas características producen cambios significativos o sólo son metabolizadas por la cultura escolar? ¿La escuela está en peligro de extinción?Trabajo presentado en el Panel 7: Producciones, encuentros y conflictos de la cultura material de la escuelaFacultad de Humanidades y Ciencias de la EducaciónSociedad Argentina de Historia de la Educación (SAHE

A Randomized Prospective Study on Outcomes of an Empathy Intervention among Second-Year Student Pharmacists

Objective. To determine the impact of a single, 3-day intervention on empathy levels as measured by the validated Jefferson Scale of Empathy-Health Profession Students version (JSE-HPS). Methods. Forty second-year student pharmacists were recruited to participate in a non-blinded prospective study. Subjects were randomized to an intervention group (n=20) or control group (n=20) and completed the JSE-HPS at baseline, 7 days postintervention, and 90 days postintervention. The intervention group consisted of a 3-day simulation, each day including a designated activity with loss of dominant hand usage, vision, and speech. Results. The 3-day simulation increased empathy levels in the intervention group compared to the control group 7 days postintervention (p=0.035). However, there were no effects on empathy levels 90 days postintervention (p=0.38). Conclusion. Empathy scores increased but were not sustained in the long-term with a 3-day empathy intervention

Thermoplastic infusible resin systems: candidates for the marine sector?

This work investigated the feasibility of the use of a novel infusible thermoplastic resin (Elium 150 from Arkema) for composite laminate manufacture by resin infusion methods and possible application in the shipbuilding sector. We compared the properties of Elium glass-fibre laminates with those of laminates infused with state-of-the-art thermosetting epoxy and urethane acrylate resins. The Elium laminates matched the mechanical performance (flexure and interlaminar shear strength) of the epoxy and surpassed that of the urethane acrylate counterpart. However, the mechanical performance of the Elium laminates after immersion in water at 35 oC for 28 days deteriorated compared to urethane acrylate, but was comparable in flexural properties to that of the epoxy. The combination of superior mechanical performance coupled with acceptable environmental resistance and comparable composite laminate manufacturing conditions makes the infusible thermoplastic a possible future candidate matrix over commercial thermosetting resin options