Further examinations of carbon/polyesterimide thick-film resistors

A carbon (carbon black and/or graphite)/polyesterimide resin system has been used as a material for polymer thick-film resistors. The physical and chemical properties of this system as a function of curing temperature were evaluated by means of resistance measurements during the curing process, thermogravimetric analysis, adhesion measurements and scanning electron microscopy examinations. The temperature range between 250 and 300 C has been chosen as the most suitable. The basic electrical properties and the resistance stability to low and high temperature shocks and humidity exposure have been evaluated in relation to the conductive filler used in the ink.     

Repair of Composites: Design Choices Leading to Lower Life-Cycle Cost

The fabrication cost of composite aircraft structures is revisited and the effect of part size on cost is examined with emphasis on design decisions which affect the ease of (bonded) repair and the total cost of the part and subsequent repairs. The case of moderately loaded stiffened fuselage or wing panels under compression is analysed in detail and the fabrication cost of the panel made as a single piece or as an assembly of smaller identical components or modules is determined. The cost of special purpose repairs for two different damage sizes is compared to removing and replacing damaged modules. Hand layup and automated processing are compared. It is found that for certain repair sizes removing and replacing modules leads to lower overall cost as compared to applying a special purpose repair.     

Wave propagation in a restricted class of orthotropic inhomogeneous half-planes

This work presents closed-form solutions for free-field motions in a certain type of orthotropic, continuously inhomogeneous half-planes that include both incident and reflected waves from the traction-free horizontal surface. A state of plane strain holds and both pressure and vertically polarized shear waves are considered. The methodology is restricted to media with orthotropic material characteristics that vary quadratically with respect to the depth coordinate. The method of solution is a hybrid approach based on the plane wave decomposition technique, augmented by appropriate functional transformation relations for the displacement vector. The existence of a unique analytical solution as superposition of incident P- or SV-waves and the corresponding reflected P- and SV-waves is proved under certain restrictions on the incident wave direction. Finally, a numerical study reveals the influence of material inhomogeneity and orthotropy on the displacement free-field motion.     

Dimension-specific intertrial priming effects are task-specific: Evidence for multiple weighting systems.

Feature singleton search is faster when the target-defining dimension repeats across consecutive trials than when it changes (Found & Müller, 1996). However, this dimension repetition benefit (DRB) has also been demonstrated for the tasks with no search component (Mortier, Theeuwes, & Starreveld, 2005). If DRBs in the search and non-search tasks have the same origin, significant DRBs across trials of different tasks should rise. Two different tasks varied either in a predictable manner (Experiment 1) or randomly (Experiment 2) across trials. In detection task, search displays containing either color or orientation singletons were used. Discrimination task required identification of either color or orientation of a single presented item (non-search display). In Experiment 3, participants performed only the discrimination task, while the search and non-search displays varied randomly. There were significant DRBs for both tasks when the task repeated but not when the task changed (Experiments 1 and 2). DRBs were significant both when the display type repeated and when it changed (Experiment 3). Overall, the findings can be well explained by assuming multiple, independent dimension-weighting systems generating DRBs in different tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activated Sintering of Magnesium Oxide from Sea Water

The process of activated sintering of magnesium oxide obtained from sea water (by precipitation with 80 % and 120 % of the stoichiometric quantity of the dolomite lime) was examined with addition of 1, 2 and 5 wt.-% TiO₂, at temperatures of 1600 °C and 1700 °C with soaking at the maximum temperature of 1, 3 and 5 hours, respectively. The product density and porosity were examined and the dependencies obtained were described by appropriate analytical expressions. The compatibility relationships between the addition of TiO₂ and the B₂O₃ content in the sintered magnesium oxide samples were determined, based on an important theorem due to Onsanger. The phenomenological cofficients were calculated for two irreversible processes, namely, those of formation of Ca₂B₂O₅and CaTiO₃, respectively.     

Functional amphiphilic block copolyethers as carriers of caffeic acid phenethyl ester

Amphiphilic diblock copolymers consisting of hydrophilic polyglycidol (PG) and hydrophobic poly(allylglycidyl ether) (PAGE) were prepared by sequential anionic ring‐opening polymerization of allylglycidyl ether and ethoxyethyl glycidyl ether followed by removal of the protective ethoxyethyl groups. The polymerization was initiated by partially deprotonated dodecanol and performed in solvent‐free conditions. The copolymers were composed of a hydrophobic dodecyl residue attached to a block of PAGE with a fixed degree of polymerization (dp = 44) and differing in length of the PG block (dp = 16 and 66, corresponding to PG contents of 25 and 60 mol%, respectively). The two copolymers were spontaneously soluble in water. Above a certain critical concentration, they formed well‐defined self‐assembled nanoparticles. Their characterization parameters were determined by static and dynamic light scattering. The aggregates of the more hydrophobic copolymer, C₁₂‐PAGE‐PG25, were characterized by considerably larger dimensions and molar mass, reaching 78.6 nm and 253.0 × 10⁶ g mol^?1, respectively, than those of the more hydrophilic copolymer, C₁₂‐PAGE‐PG60. The hydrophobic moieties were proved to create a favorable environment for solubilization of caffeic acid phenethyl ester (CAPE) (the main active ingredient of propolis with cytotoxic and antioxidant activities), whereas the numerous hydroxyl groups from the PG moieties brought additional benefits related to the biocompatibility of the copolymers. Preliminary experiments with L929 fibroblast cells showed that the aggregates displayed no signs of toxicity in the applied in vitro test system, suggesting their appropriateness as a drug delivery platform. The CAPE‐loaded aggregates, however, showed dose‐dependent cytotoxic effects, indicating that CAPE retained its cytotoxic activity. © 2019 Society of Chemical Industry