Search

This article focuses on a laboratory materials-testing program that was aimed at: (1) identifying candidate shrinkage-compensating concrete (SCC) mixture designs for possible later field evaluations; and (2) performing mechanical property evaluations of the candidate mixtures under various simulated weather and curing conditions. The SCC mixtures were produced by using a Type K portland cement. Results of the laboratory concrete mixture design, property evaluation, and sensitivity testing verified that sec mixtures should be viable mixtures for bridge decks to reduce shrinkage cracking. The testing revealed that: (1) time-of-set of sec was faster than for ordinary portland cement concrete by about 100 min, as was the rate of slump loss; (2) the compressive and splitting tensile strengths of the SCC mixtures were higher than those of conventional concrete mixtures using Type I portland cement; (3) the compressive strengths of concrete mixtures with both the Type K and Type I cements were enhanced by the addition of silica fume; (4) the SCC concrete restrained length bar specimens exhibited significant early (first 7 days) expansion; (5) type K cement restrained mortar bars exhibited ~4 times more expansion than mortar bars made with Type I cement; and (6) type K cement mixtures are quite sensitive to proper moist curing if they are to achieve proper shrinkage compensation.

Research indicates that rat taste receptor cells contain epithelial sodium channels which are directly involved in NH4Cl and KCl transduction taste mechnanism. Experiments designed to assess the effects of epithelial sodium channel antagonists benzamil and amiloride on the physiology of chorda tympani nerves from male Sprague-Dawley rats are described. Evidence suggests that multiple transcellular pathways are involved in salt taste transduction.

This paper reviews some of the past instrumentation and performance measuring used by the U. S. Army Corps of Engineers to develop its rigid-pavement design procedures, and it will consider two areas where future studies could improve our understanding of rigid pavement performance. Results of instrumental model tests and full-scale traffic tests gave confidence in the Westergaard edge-loaded analytical model to calculate design stresses. This model has been the backbone of the design concept for more than 40 years, and it continues to serve the Corps well. Also, performance measurements of joints developed the concept of joint load transfer that allowed more economical design of pavements and that also defined standards of joint design. There are still challenges facing the Corps, where instrumentation and performance measurements in the field can help develop better design standards. The actual effects of temperature and moisture gradients on rigid-pavement performance and bonding in rigid-pavement overlays remain poor and could be improved by field measurements., The procedure used by the US Army Corps of Engineers for rigid-pavement design is evaluated. Testing results have proven the accuracy of the Westergaard edge-loaded analytical model, which has always been the basis of determining design stresses. The inclusion of the joint load transfer concept in the theoretical model was also verified through field testing and performance. Results show that this concept improves the efficiency of pavement design.

This paper examines the mechanical response of precast panel pavement repair joints under static aircraft loadings using the finite-element method. Three-dimensional finite-element models were developed using the Abaqus software code, and their results were compared to and validated against results of full-scale field tests and theoretical calculations. Unlike previous pavement repair modelling efforts for precast panels and dowel retrofitting studies, all parts of the repair joint were modelled, including the dowels, dowel slot material, parent concrete, precast panel and pavement sublayers. Results show that high stress concentrations occur in the dowel slot material and that the current panel design is likely to be improved by modifying the dowel diameter. [ABSTRACT FROM AUTHOR]

Abstract: It has been reported previously that exposure to static high magnetic fields of 7 T or above in superconducting magnets has behavioral effects on rats. In particular, magnetic field exposure acutely but transiently suppressed rearing and induced walking in tight circles; the direction of circular locomotion was dependent on the rats'' orientation within the magnet. Furthermore, when magnet exposure was paired with consumption of a palatable, novel solution, rats acquired a persistent taste aversion. In order to confirm these results under more controlled conditions, we exposed rats to static magnetic fields of 4 to 19.4 T in a 189 mm bore, 20 T resistive magnet. By using a resistive magnet, field strengths could be arbitrary varied from −19.4 to 19.4 T within the same bore. Rearing was suppressed after exposure to 4 T and above; circling was observed after 7 T and above. Conditioned taste aversion was acquired after 14 T and above. The effects of the magnetic fields were dependent on orientation. Exposure to +14 T induced counter-clockwise circling, while exposure to −14 T induced clockwise circling. Exposure with the rostral–caudal axis of the rat perpendicular to the magnetic field produced an attenuated behavioral response compared to exposure with the rostral–caudal axis parallel to the field. These results in a single resistive magnet confirm and extend our earlier findings using multiple superconducting magnets. They demonstrate that the behavioral effects of exposure within large magnets are dependent on the magnetic field, and not on non-magnetic properties of the machinery. Finally, the effects of exposure to 4 T are clinically relevant, as 4 T magnetic fields are commonly used in functional MRI assays. [Copyright &y& Elsevier]

Abstract: A gustatory transduction mechanism for free fatty acids (FFAs) has been described in isolated rat taste receptor cells; however, the ability of behaving rats to detect FFAs has not been characterized. Through conditioned taste aversion (CTA) methodology, this study defines the ability of rats to detect and avoid the two principal FFA components of corn oil, linoleic and oleic acid. Following taste aversion conditioning, rats avoided both linoleic and oleic acid at greater than or equal to 66 μM and failed to avoid either 44 μM linoleic or oleic acid. Rats demonstrated generalized avoidances between 88 μM linoleic and oleic acid irrespective of presenting the FFAs as either unesterified acids dissolved in 5 mM ethanol or aqueous sodium salts, sodium linoleate and sodium oleate. Following a CTA to linoleic acid, rats did not show generalized avoidance of NaCl or ethanol, two potentially concomitant tastants in the oral cavity. A CTA to linoleic or oleic acid did produce a generalized avoidance to the other FFA. These results support the ability of rats to detect linoleic and oleic acid (>44 μM) and suggest that the two FFAs share common orosensory properties. Furthermore, it is unlikely that the detection of the FFAs is due to an enhancement of other concomitant tastants such as saliva or the delivery solution. [Copyright &y& Elsevier]

Benzodiazepines are one of the most commonly prescribed anxiolytic drugs in America, and between 2006 and 2015 prescription rates increased by an estimated 27.1%. Weight gain is a common side effect of these drugs and it may result from increased feeding caused by drug-enhanced food palatability. We investigated the role of specific GABA A receptor subtypes involved with benzodiazepine-induced food consumption through third ventricle injections of L-838,417, a partial agonist of GABA A α2, α3, and α5 subunits, and a full antagonist of the α1 receptor subunit. A microanalysis of the licking behavior of adult male rats to a sucrose solution was used to isolate drug effects on specific consummatory behaviors that include: hedonic taste evaluation, food approach behavior, and oromotor function. L-838,417 dose-dependently increased intake through increases in the motivation to approach the solution (shorter pause intervals between bouts of licking) and through enhancement of measures associated with hedonic taste evaluation. Oromotor depressant effects previously associated with broad-spectrum benzodiazepine receptor agonists were not observed. These results indicate that nuclei in proximity to the ventricles respond to GABA A α2, α3, or α5 activation to induce motivation to feed, absent of α1 receptor subunit activation. Furthermore, activation of the α1 subunit is not necessary for benzodiazepine hyperphagia and may instead contribute to the oromotor depressant and sedative properties of classic benzodiazepine agonists. Hypothalamic nuclei such as the paraventricular nucleus may be involved in the benzodiazepine-increased motivation to feed, while the parabrachial nucleus of the hindbrain could contribute to benzodiazepine-induced enhancement of taste palatability., (Copyright © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.)

Gene-environment interactions play a role in the development of obesity but specific effects of diet on the orosensory detection of fatty acids have yet to be clarified. The objective of this study is to characterize the effect of prolonged (5-week) exposure to a high-fat (60%) diet on the behavioral sensitivity to the fatty acid linoleate following a conditioned taste aversion in obesity-prone and obesity-resistant rats. Exposure to the high-fat diet significantly enhanced the sensitivity of obesity-resistant (S5B/Pl) rats to linoleate while producing no effect on the fatty acid sensitivity for obesity-prone rats. Specifically, high-fat diet fed S5B/Pl rats showed stronger initial avoidance of linoleate and slower extinction rates than their normal diet cohorts. Our study suggests that prolonged dietary fat consumption may alter the behavioral sensitivity to fatty acids particularly in obesity-resistant animals.