The influence of oil viscosity and refrigerant quality on evaporator performance

The presence of oil in an evaporator degrades performance by reducing evaporator heat pick-up and by increasing the evaporator pressure drops. It can be demonstrated that there is an optimum refrigerant mass flow rate for a given refrigerant-oil combination and oil concentration. Also, oil viscosity has an effect on the evaporator performance at low oil concentrations. Finally, it is suggested that low viscosity oil be used at low oil concentrations and high viscosity oil at high oil concentrations.     

"Rereading text: Words and their context": Erratum.

Reports an error in the original article by B. A. Levy et al (Canadian Journal of Psychology, 1991[Dec], Vol 45[4], 492–506). Corrections to tables 2 and 3 regarding mean reading times during original reading and rereading in Exps 1 and 2, respectively, are provided. (The following abstract of this article originally appeared in PA Vol 79:18597.) Two experiments examined whether the benefits of rereading are mediated by abstract word-level representations and are subject to the reader's focus of attention (T. H. Carr and J. S. Brown; see record 1990-27485-001). The effect of prior reading history was measured when 50 undergraduates reread a normal text and a scrambled word version of the text. The prior reading history was either with the normal or the scrambled version. In Exp 1, readers were oriented to surface level processing by a Greek letter detection task while reading. In Exp 2, Ss were oriented to message level processing by being required to write a summary of the text after each rereading. Transfer to normal text rereading is context specific, and this specificity is resistant to influences by focus of attention. Transfer to rereading scrambled word displays is variable, usually nonspecific, and perhaps open to attentional strategy. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grain Growth in CaO-Stabilized ZrO2 in the Presence of a Liquid Phase

Calcia-stabilized zirconia, CSZ (7.5 wt% CaO), with impurities of A1₂O₃, SiO₂, MgO, Fe₂O₃, and TiO₂, was sintered in air at 1783 K for times (t) up to 230 h. The microstructure consisted of grains of CSZ with small amounts of pores and a CaO-Al₂O₃-SiO₂ eutectic. Grain diameters grew in proportion to t^1/3. The results are consistent with a mechanism in which grain growth is limited by diffusion of Zr⁴⁺ ions through the liquid eutectic.     

Influence of bentonite clay on the rheological behaviour of fresh mortars

Fine mineral additives are often used in the formulation of ready-mix mortars as thickeners and thixotropic agents. Yet, these attributed fresh state properties are not clearly defined from the rheological point of view. In the present study, we consider the influence of bentonite (montmorillonite-based clay mineral) on the rheological behaviour of mortars, including in particular creep and thixotropy. The mortar pastes are subjected to different shear-rates and then allowed to creep under fixed shear stresses until reaching steady state, which corresponds to either rest if the applied stress is smaller than the yield stress or permanent flow otherwise. The evolution of the creep strain is investigated depending on shear history for different contents of bentonite. The microstructure rebuilding kinetics after shear (thixotropy) is considered by analysing the temporal evolution of the creep strain for different applied shear stresses (lower than the yield stress). As expected, bentonite is found to enhance the mortar creep (or sag) resistance. This enhancement consists of both an increase of the yield stress recovered after shear, and a diminution of the characteristic time for yield stress recovery (related to microstructure rebuilding).     

Semiochemical basis of infestation of honey bee brood byVarroa jacobsoni

Capping of workerApis mellifera cells is elicited by four fatty acid methyl esters (Methyl palmitate, methyl oleate, methyl linoleate, and methyl linolenate) that are present on the surface of the worker and drone larvae only a few hours before the cell is closed. The amount of the pheromone reaches its maximum value when the cell has just been capped, at 8.5 and at 10.25 days of age, respectively, for worker and drone larvae. Thereafter, the amount of the pheromone decreases to its initial level. These data suggest that the esters also have a role in the capping of the drone cells, the temporal signal allowing the worker bees to recognize the age of the larvae and then to do the appropriate behavior. Two pheromonal components, methyl palmitate and methyl linolenate, and the inactive ethyl palmitate are kairomones attractive toVarroa females. Their secretion by the larvae follows the same pattern of development as the pheromonal signal. The longer and greater kairomonal signal in drone larvae, compared to worker secretion, could explain the preference ofVarroa towards drone brood.     

UV-radiation curing of waterbased urethane–acrylate coatings

A kinetic study of the drying and UV-curing of waterbased urethane–acrylate formulation was conducted by means of infrared spectroscopy. The water release upon heating of the dispersion was shown to depend on the temperature and on the film thickness. The drying of a 30 μm thick coating was completed in <2 min upon heating in an oven at 80°C. The influence of a number of critical factors on the polymerization kinetics has been investigated, namely the type of photoinitiator, the sample temperature, the chemical structure of the functionalized oligomer and its acid content. As expected, the latter factor has a strong effect on the properties of the UV-cured coatings, in particular their hardness and their hydrophilic character. The water uptake and the softening of coatings placed in a wet atmosphere was found to be directly related to the carboxylic acid content of the urethane–acrylate polymer. This phenomenon is fully reversible and does not affect the long term properties of the UV-cured coatings.