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

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

Pulsar timing analysis in the presence of correlated noise

Pulsar timing observations are usually analysed with least-square-fitting procedures under the assumption that the timing residuals are uncorrelated (statistically "white"). Pulsar observers are well aware that this assumption often breaks down and causes severe errors in estimating the parameters of the timing model and their uncertainties. Ad hoc methods for minimizing these errors have been developed, but we show that they are far from optimal. Compensation for temporal correlation can be done optimally if the covariance matrix of the residuals is known using a linear transformation that whitens both the residuals and the timing model. We adopt a transformation based on the Cholesky decomposition of the covariance matrix, but the transformation is not unique. We show how to estimate the covariance matrix with sufficient accuracy to optimize the pulsar timing analysis. We also show how to apply this procedure to estimate the spectrum of any time series with a steep red power-law spectrum, including those with irregular sampling and variable error bars, which are otherwise very difficult to analyse.Comment: Accepted by MNRA

Direct iminization of PEEK

Semi-crystalline poly(ether ketone)s are important high-temperature engineering thermoplastics, but are difficult to characterize at the molecular level because of their insolubility in conventional organic solvents. Here we report that polymers of this type, including PEEK, react cleanly at high temperatures with low-volatility aralkyl amines to afford stable, noncrystalline poly(ether-imine)s, which are readily soluble in solvents such as chloroform, THF and DMF and so characterizable by conventional size-exclusion chromatography

Sustainable functionality : micro-housing for community-centric build environments

This thesis investigated the impact of micro-housing as a potential solution to the ever-rising worldwide crisis of insufficient housing availability. It focused predominately on the European region and in urban environments. Implementing a mixed-methods approach, this study analyzed the potential and social benefits of micro-housing developments in the region. The project combined quantitative data analysis of housing market trends and demographic shifts. The research examined various key aspects, including the financial accessibility of micro-housing units, spatial efficiency, impact on community building, and social interaction. The literature review involved the examination of academic articles, design studies, and an existing micro-housing project. The purpose was to establish a theoretical foundation and to identify global and regional trends, challenges, and innovations in compact housing solutions. Finally, the thesis applied a design thinking methodology in developing an original micro-housing concept. This included empathy mapping, ideation, material analysis, and smart housing. The outcome was tailored to the needs of students and elderly users and reflects design principles aligned with sustainability and circularity goals

Corpuscular model of two-beam interference and double-slit experiments with single photons

We introduce an event-based corpuscular simulation model that reproduces the wave mechanical results of single-photon double slit and two-beam interference experiments and (of a one-to-one copy of an experimental realization) of a single-photon interference experiment with a Fresnel biprism. The simulation comprises models that capture the essential features of the apparatuses used in the experiment, including the single-photon detectors recording individual detector clicks. We demonstrate that incorporating in the detector model, simple and minimalistic processes mimicking the memory and threshold behavior of single-photon detectors is sufficient to produce multipath interference patterns. These multipath interference patterns are built up by individual particles taking one single path to the detector where they arrive one-by-one. The particles in our model are not corpuscular in the standard, classical physics sense in that they are information carriers that exchange information with the apparatuses of the experimental set-up. The interference pattern is the final, collective outcome of the information exchanges of many particles with these apparatuses. The interference patterns are produced without making reference to the solution of a wave equation and without introducing signalling or non-local interactions between the particles or between different detection points on the detector screen.Comment: Accepted for publication in J. Phys. Soc. Jpn

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

International audienc

Peculiar case of branching of the trachea together with both, main and lobar, bronchi into a fetal lung

Abstract Using as study method the injection of plastic followed by corrosion, we described, on an 8 months fetal lung, a particular branching pattern of the right bronchial tree were the superior lobar bronchus arise on the right side of the trachea, at 4.1 cm cranial to tracheal bifurcation. Other features of tracheo-bronchial branching encountered in this case: the level and tracheal bifurcation site and origin and the trajectory of the main bronchi, the middle lobar bronchi of the right lung and apical bronchus of the inferior lobar bronchi. To these peculiarities of the tracheo-bronchial tree are described also the peculiarities of the pulmonary arteries branches, which accompanies bronchial ramifications.</jats:p