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Absorbing Materials (absorbing + material)
Selected AbstractsX-ray colour maps of the cores of galaxy clustersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000J. S. Sanders We present an analysis of X-ray colour maps of the cores of clusters of galaxies, formed from the ratios of counts in different X-ray bands. Our technique groups pixels lying between contours in an adaptively smoothed image of a cluster. We select the contour levels to minimize the uncertainties in the colour ratios, whilst preserving the structure of the object. We extend the work of Allen & Fabian by investigating the spatial distributions of cooling gas and absorbing material in cluster cores. Their sample is almost doubled: we analyse archive ROSAT Position Sensitive Proportional Counter (PSPC) data for 33 clusters from the sample of the 55 brightest X-ray clusters in the sky. Many of our clusters contain strong cooling flows. We present colour maps of a sample of the clusters, in addition to adaptively smoothed images in different bands. Most of the cooling flow clusters display little substructure, unlike several of the non-cooling-flow clusters. We fitted an isothermal plasma model with galactic absorption and constant metallicity to the mid-over-high energy colours in our clusters. Those clusters with known strong cooling flows have inner contours which fit a significantly lower temperature than the outer contours. Clusters in the sample without strong cooling flows show no significant temperature variation. The inclusion of a metallicity gradient alone was not sufficient to explain the observations. A cooling flow component plus a constant temperature phase did account for the colour profiles in clusters with known strong cooling flow components. We also had to increase the levels of absorbing material to fit the low-over-high colours at the cluster centres. Our results provide more evidence that cooling flows accumulate absorbing material. No evidence for increased absorption was found for the non-cooling-flow clusters. [source] FS09.2 Contact allergy to a commercial alcohol prep swabCONTACT DERMATITIS, Issue 3 2004James S Taylor Allergic contact dermatitis to prepackaged disposable alcohol prep swabs is infrequently reported. A 60-year-old woman developed repeated episodes of dermatitis at sites of injections and venipunctures. History and patch testing revealed contact allergy to Kendall Webcol alchol prep swabs. There were negative patch test results to isopropyl alcohol (IPA), but positive reactions to the Webcol swab, to the inner surface of the packaging foil, to two other brands of alcohol swabs, and to bacitracin. UV absorbance profile analysis revealed the presence of UV absorbing materials at peaks of 221 and 280 nm within commercial IPA samples, including one from Kendall, which were absent from reagent grade IPA. Reports of similar cases identified IPA, propylene oxide, or both as the allergens; when swab ingredients were negative, compound allergy was proposed. A recent report from Korea identified dodecyldiaminoethylglycine and IPA as the allergens in the commercial disinfectant swab. Although the exact allergen is undetermined in our case, it may represent a chemical compound or contaminant that is used or acquired during the manufacturing of the swabs or foils. [source] Solving inverse electromagnetic problems using FDTD and gradient-based minimizationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2006Erik Abenius Abstract We address time-domain inverse electromagnetic scattering for determining unknown characteristics of an object from observations of the scattered field. Applications include non-destructive characterization of media and optimization of material properties, for example, the design of radar absorbing materials. Another application is model reduction where a detailed model of a complex geometry is reduced to a simplified model. The inverse problem is formulated as an optimal control problem where the cost function to be minimized is the difference between the estimated and observed fields, and the control parameters are the unknown object characteristics. The problem is solved in a deterministic gradient-based optimization algorithm using a parallel 2D FDTD scheme. Highly accurate analytical gradients are computed from the adjoint formulation. The inverse method is applied to the characterization of layered dispersive media and the determination of parameters in subcell models for thin sheets and narrow slots. Copyright © 2006 John Wiley & Sons, Ltd. [source] Optimum design of electromagnetic shielding rooms with minimum usage of absorbing materialsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010S. M. J. Razavi Abstract In this article, a novel method has been proposed to optimize the electromagnetic shielding rooms. This method is based on using minimum electromagnetic absorbing materials on the inner surface of the rooms. The positions of the absorbing materials are found optimally to produce a "best" performance for the shielding rooms. The ray-tracing method is used to predict the shielding effectiveness (SE) of the electromagnetic shielding rooms with apertures. The performance of the proposed method is verified by a comprehensive example. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010. [source] Polymer Bonded Ferrite Materials as EMC ComponentsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2003J. Töpfer Polymergebundene Ferrite; Ferritabsorber; Permeabilität; Dämpfung Abstract Polymer bonded ferrites composed of a mixture of Mn-Zn ferrites or Ni-Zn ferrites in a polymer binder (PE, PA) were prepared and tested as electromagnetic-wave absorbing materials. Test samples and cases were prepared by hot or injection molding. Permeability spectra show loss contributions in the frequency range 100-1000,MHz. Absorption measurements of injection molded polymer-ferrite cases display a 3-5,dB better attenuation characteristics compared to graphite-loaded polyamide housings. Polymer-gebundene Ferritwerkstoffe für EMV-Anwendungen Polymer-gebundene Ferritwerkstoffe auf der Basis von Ferrit (Mn-Zn oder Ni-Zn Ferrite) , Thermoplast Mischungen wurden präpariert und hinsichtlich ihrer Eignung zur Absorption elektromagnetischer Strahlung untersucht. Es wurden sowohl Testproben wie auch komplette Gehäusekomponenten durch Heißpressen oder Spritzgießen hergestellt. Die Permeabilitätsspektren weisen verlustbehaftete Komponenten im Frequenzbereich von 100-1000,MHz auf. Schirmdämpfungsmessungen an spritzgegossenen Gehäuseteilen zeigen eine um 3-5,dB bessere Dämpfung im Vergleich zu Graphit-gefüllten Polyamid-Gehäusen. [source] Reactive doping of PAni,CSA and its use in microwave absorbing materialsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2009R. S. Biscaro Abstract Conductive coatings have been studied for static dissipation and as microwave absorbing materials. The doping process of polyaniline (PAni), which makes it conductive, is an important stage that determines the coating performance. For this purpose, polyaniline was doped by reactive processing in a torque rheometer using different molar ratios between PAni and acid (PAni:CSA) at three different temperatures (80, 90, and 100°C). Aqueous solution doping was also used in the ratio of 1:2 of PAni/CSA, with the aim to investigate the influence of different methods of PAni doping on its characteristics and, consequently, on the performance of coatings. Thermal analyses of the processed materials showed that PAni doped by both routes, reactive and solution processing, showed similar behaviors. X-ray diffraction analyses showed a semicrystalline structure for the PAni,CSA doped by reactive processing using high CSA concentrations and temperature. It was also observed that the doping process affects the dispersion of the components into the conductive coatings. Microwave absorption measurements (8,12,GHz) of PU-doped PAni blends showed the dependence of the doping type, the PAni,CSA concentration, and the mixing conditions of the components on the coating performance; it was found up to 99% of attenuation of the incident radiation for some composites in a narrow frequency range. The microwave absorption efficiency of the coating samples prepared by using the reactive doping process indicates the advantage of this methodology over solution doping. Moreover, the reactive process addresses the environmental requirements. Copyright © 2008 John Wiley & Sons, Ltd. [source] Recent developments in the use of two-photon polymerization in precise 2D and 3D microfabrications,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2006Kwang-Sup Lee Abstract The use of two-photon polymerization (TPP) initiated by a photosensitizer's non-linear two-photon absorption in two- and three-dimensional (2D and 3D) microfabrications for various photonic applications has been intensively studied. Since TPP emerged as a new technology over a decade ago, a large variety of micro-objects including 3D micro-optical components, micromechanical devices, and 3D photonic crystals have been fabricated using TPP with a high spatial resolution of approximately submicron scale to 100,nm. Recent efforts have been made to improve the fabrication efficiency and precision of micro-objects obtained with TPP; in particular, many studies have been carried out with the aim of developing efficient two-photon absorbing chromophores. In this article, efforts to develop highly efficient two-photon absorbing materials and also describe recent attempts to enhance the resolution and improve the fabrication efficiency of nanofabrications based on two-photon polymerization are discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||