Using aluminium triflate as a co‐catalyst for the polymerization of o‐phenylenediamine and its derivatives

Aromatic diamine monomers, including o‐phenylenediamine (oPD), 4‐methyl‐o‐phenylenediamine (4Me‐oPD), 4,5‐dimethyl‐o‐phenylenediamine (dMe‐oPD) and 4‐(tert‐butyl)‐o‐phenylenediamine (tBu‐oPD), were polymerized by chemical oxidation using ammonium persulfate as an oxidant. Aluminium triflate (Al(OTf)₃) was also used for the first time as a co‐catalyst under various reaction conditions for the polymerization of oPD derivatives. The polymerization yield was improved when Al(OTf)₃ was introduced to the polymerization reaction for most polymers. The solubility of poly(4‐methyl‐o‐phenylenediamine) (P(4Me‐oPD)), poly(4,5‐dimethyl‐o‐phenylenediamine) (P(dMe‐oPD)) and poly(4‐(tert‐butyl)‐o‐phenylenediamine) (P(tBu‐oPD)) polymers was improved compared with the poly(o‐phenylenediamine) (P(oPD)) polymers in most common solvents. The homopolymers obtained were characterized by Fourier transform IR spectroscopy, UV?visible spectroscopy, ¹H and ¹³C NMR, wide‐angle X‐ray diffraction, DSC and TGA. The results showed that the yield, solubility and structure of the polymers are significantly dependent on the polymerization conditions. DSC measurements indicated that the polymers exhibited melting and crystallization transitions. The polymers also showed good thermal stability and decompose above 400 °C in nitrogen. © 2013 Society of Chemical Industry     

Dielectric behaviour in Co-substituted NiSb ferrites

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Prestress losses in fibreglass pretensioned concrete compression members

Fibreglass has been used recently as a prestressing material in concrete structures, and it has demonstrated some advantages over steel tendons especially in corrosive environments. An experimental estimation of the long term losses of concrete columns and piles pretensioned with fibreglass (S-2 glass) is presented in this paper. Three identical sets of steel and fibreglass specimens with nominal dimensions of 152 mm×102 mm×2.6 m (6 in ×4 in ×102 in) were instrumented and tested to evaluate prestress losses under axial compression loads at different stress levels. Results after 20 months show that prestress losses in fibreglass tendons are less than those in steel tendons. The effective prestress for fibreglass pretensioned specimens can be predicted accurately using the step-by-step method. The measured data were compared with several models. For a practical applied stress of 0.3f_c ^′, the current ACI and Bazant equations for creep and shrinkage predicted the strain history, prestress losses, and effective prestress of fibreglass pretensioned concrete specimens with good accuracy.

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Resume La fibre de verre a été récemment utilisée comme matériau de précontrainee dans les structures en béton et présente certains avantages sur les armatures d'acier, surtout dans les environnements corrosifs. C'est la dégradation des structures en béton préconstraint et en béton armé dans ce type d'environment qui a conduit à rechercher d'autres matériaux de précontrainte plus durables. C'est ainsi que la fibre de verre est apparue comme une solution de remplacement. Elle a pour propriétés une haute résistance à la traction, une bonne adhérence et une excellente résistance à la corrosion. Le présent rapport donne une estimation expérimentale des pertes à long terme des poteaux et des pieux précontraints par prétension avec de la fibre de verre. Trois séries identiques d'éléments d'acier et de fibre de verre avec des dimensions nominales de 152 mm × 102 mm × 2,6 m ont été essayées pour évaluer les pertes de précontrainte sous des charges de compression axiale à différents niveaux de contrainte. Les résultats après 20 mois ont indiqué qu'avec les armatures d'acier les pertes sont plus importantes qu'avec des armatures de fibre de verre. L'efficacité de la précontrainte des éléments avec fibres de verre peut être déterminée avec exactitude. Les données mesurées sont comparées avec plusieurs modèles de fluage et de retrait. Pour une contrainte de 0,3 f_c ^' exercée, les équations actuelles de l'ACI et Bažant pour le fluage et le retrait ont permis de prévoir avec une assez grande précision le processus de déformation, les pertes de précontrainte et l'efficacité de la précontrainte des éléments de béton à fibres de verre.

     

Carcinoma of prostate metastatic to breast

A case with 1-cm distraction elongation of a child's thumb metacarpal 7 years after initial injury is presented. The thumb to long finger pinch was improved by this procedure. The metacarpal elongation has been maintained for 3 years. The mechanism of this repair appears to be ossification of connective tissue. Immobilization until bony union is complete is recommended to avoid loss of length gained.     

Fibre interactions in two-dimensional composites by micro-Raman spectroscopy

In the study of fracture processes in composite materials, the interactions between broken and intact fibres are of critical importance. Indeed, the redistribution of stress from a failed fibre to its unfailed adjacent neighbours, and the stress concentration induced in these, determine the extent to which a break in one fibre will cause more breaks in neighbouring fibres. The overall failure pattern is a direct function of the stress concentration factors. In this paper we use laser micro-Raman spectroscopy to study the extent of stress transfer and redistribution caused by fibre fracture in two-dimensional Kevlar 149 based microcomposites. The strain along the fibres was mapped at different levels of load, and specimens with different inter-fibre distances were used to study the fibre content effect. The experimental stress concentration factors were compared with values predicted from various theoretical models. The stress concentration factors generally agreed with those literature models that include interfibre distance and matrix effects. The overall failure pattern was found not to be a direct function of the stress concentration factors in this system, as fracture propagates from fibre to fibre even at large interfibre distances, and is apparently accompanied by relatively low values of the stress concentration factors. The critical cluster size, beyond which final fracture of the composite occurs in a catastrophic manner, was found to be larger than five adjacent fibre breaks in the present system, for all interfibre distances studied.Visiting Stein Fellow at Drexel University, July-September 1994.     

New device and method for measuring thermal conductivity of thin-films

Thermal sensitive paints (TSPs) are used for global nonintrusive detection of boundary layer transition in flow over the surface of wind tunnel research models. Since the transition is a transient process, the TSP should have a fast response characteristic. A low paint thermal conductivity is required for fast response. A thin-film thermal conductivity meter (TFTCM) was designed and built to measure thermal conductivity of the TSPs, which are typically between 50 and 150 microm thick. In this paper, the design and operating features of the TFTCM are described. Measurement of the thermal conductivity with this TFTCM of three standard thin-film low conductivity specimens, Kapton, Teflon, and Borofloat glass, showed good agreement with the manufacturer quoted values, thus validating the instrument and the procedure. Consistently repeatable values for thermal conductivity (k=0.41 +/- 0.02 W/m K) were also obtained for the TSP specimen (TSB-B, 75 microm) tested.     

Large-scale channel characterization at 28 GHz on a university campus in the United Arab Emirates

Telecommunication Systems - Millimeter wave (mm-wave) communication is one of the key enabling technologies for meeting the requirements of the fifth generation (5G) wireless communication systems....     

Integrating program analyses with programmer productivity tools

Because software continues to grow in size and complexity, programmers increasingly rely on productivity tools to understand, debug, and modify their programs. These tools typically use program analyses to produce information for the programmer. This is problematic because it is based on the assumption that the programmer and program analyses all use the same vocabulary. If the programmer and analyses did not use the same vocabulary then the results of the analyses will be meaningless to the programmer. For example, ‘v124 may be NULL’ does not mean much to the programmer but ‘myStack may be NULL’ is meaningful. Often, the programmer and analyses prefer different vocabularies. While the programmer prefers his programs' source code, an analysis will prefer a simplified representation. Unfortunately, writing an analysis that works on the source code is difficult because the analysis must deal with the idiosyncracies of the source language (e.g. nested classes). In comparison, writing an analysis on SSA form is easy but the output of the analysis is not meaningful to the programmer; it must somehow be translated into something the programmer understands. We present a system, RTalk, that makes it easy to support both the programmers' and the analysis' needs. RTalk generates a translator between the programmers' and the analysis' vocabulary. Thus both the programmer and the analysis can use the vocabulary most natural to them. We demonstrate the effectiveness of RTalk by describing program understanding and program optimization tools that we have already built using RTalk. Copyright © 2011 John Wiley & Sons, Ltd.