Material constant sensitivity boundary integral equation for anisotropic solids

In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd.     

Spatial orientation on a vertical maze in free-ranging fox squirrels (Sciurus niger).

To determine how squirrels return to remembered locations in an arboreal environment, wild fox squirrels (Sciurus niger) were trained on an outdoor vertical maze. Squirrels were trained on 1 route and tested with all routes accessible. Possible mechanisms of spatial orientation were distinguished with manipulations such as rotations, shifts, and blocked routes. Squirrels consistently used an extra-maze, allothetic frame of reference to orient and appeared to organize their memory of the route hierarchically. This study demonstrates that a laboratory technique, the maze, can be successfully brought into the field to measure mechanisms of spatial orientation under natural conditions in free-ranging wild rodents. Such studies will allow researchers to determine what kind of spatial information is acquired by wild animals under natural conditions and how this information is used. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduction of Pathogens Using Hot Water and Lactic Acid on Beef Trimmings

Beef trimmings from young or mature beef cattle were obtained commercially. Trimmings within age type then were inoculated with about 6.0 log₁₀ CFU/mL of rifampicin-resistant. Escherichia coli O157:H7 and Salmonella typhimurium (ATCC 13311) were randomly assigned to 1 of 3 treatments (control; 95 °C hot water alone, or with 2% L-lactic acid). After treatment, trimmings were ground, held for 0, 14, 28, or 42 d in chub packages at 4 °C, and total aerobic plat counts, E. coli O157:H7, and S. typhimurium counts were determined. Non-inoculated trimmings were also treated and samples were evaluated for pH, fat, moisture, TBA, meat color by colorimeter, and meat color, and odor by trained sensory panels. Trimmings treated with water or hot water plus lactic acid reduced levels of E. coli O157:H7 and S. typhimurium and tended to be darker after treatment. Meat odor in the final product was not affected by treatment.     

Legumes seeds protein isolates in the production of ascorbic acid microparticles

This study evaluated the use of pea (Pisum sativum) and cowpea (Vigna unguiculata) protein isolates (PPI and CPI) in the microencapsulation of ascorbic acid (AA), by spray drying. PPI and CPI were used pure or mixed with maltodextrin (M) as wall materials of AA. The process yield was improved from 66% to 86% by the addition of M (CPI/M and PPI/M); also, AA particles yield was 79%. The AA retention from the drying process was higher in PPI/M (69%) than in CPI/M (66%), and this was attributed to PPI proteolysis profile, demonstrated by the SDS–PAGE electrophoresis. Scanning electron microscopy revealed that AA particles were similarly spherical and shriveled. Mean particle sizes of PPI/M/AA and CPI/M/AA were 7 and 8 μm, respectively. This study showed the exploration of protein isolates from legumes in the development of a microparticulate system containing AA with great potential for use in human health.     

Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)]/layered double hydroxide nanocomposites

BACKGROUND: The thermomechanical performance of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) is associated with its crystallization. Enhanced nucleation using a stearate‐functionalized synthetic layered double hydroxide (LDH) presents a potential solution. RESULTS: PHBV crystallization varied with concentration of LDH. At lower LDH concentration, thermal history‐induced cold crystallization was present. The extent of this order–disorder transition decreased with increasing LDH concentration and was completely eliminated at 7 wt% LDH. PHBV did not have a melt recrystallization peak but the introduction of LDH resulted in an increasingly pronounced melt recrystallization with increasing LDH concentration. Polarized optical microscopy coupled with differential scanning calorimetry and wide angle X‐ray diffraction (WAXD) analysis indicated increased lamella thickness in the nanocomposites compared to pure PHBV. WAXD and transmission electron microscopy showed that the nanocomposites had an intercalated but aggregated dispersion. CONCLUSION: The concentration of nanofiller provides unique effects in PHBV. Mechanical performance was found to scale with composition as determined using dynamic mechanical analysis and tensile testing. Copyright © 2008 Society of Chemical Industry     

Corrosion of friction stir welded magnesium alloy AM50

The microstructure of a friction stir welded magnesium alloy AM50 was examined by means of optical light microscopy. The chemical composition, particularly the iron content, and morphology of the oxide film were analyzed and discerned via auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Corrosion behaviour of the welds and base materials were investigated by virtue of neutral salt spray tests and potentiodynamic polarization measurements in conventional cells and in a mini cell. The results demonstrate that minor increases in iron concentration as might be speculated to occur as a consequence of tool/work piece interaction during the welding process on the corrosion resistance of the weld can be ignored. The corrosion morphology was predominantly influenced by the distribution of the Mg₁₇Al₁₂ phase. Here, it was also found that the corrosion resistance of the friction stir weld varied in response to changes in the joint microstructure.     

Photophysical properties of Eu supported on silica gel functionalized with propyl β-diketonates

New luminescent materials consisting of Eu³⁺ supported on silica gel functionalized with acetylacetone (EuAPG) and benzoyltrifiuoroacetone (EuBPG) showed a much more intense emission than Eu³⁺ supported either on silica gel (EuSG) or on silica gel functionalized with imidazole (EuIPG). The lifetimes of the Eu³⁺⁵D₀→⁷F₂ transition in the samples were determined. All the silica contained about 0.2–0.3 wt.% of Eu³⁺.     

Strategic control in a naming task: Changing routes or changing deadlines?

S. Monsell, K. E. Patterson, A. Graham, C. H. Hughes, and R. Milroy (1992) reported that high-frequency irregular words are named faster when presented in a "pure" block than when mixed with nonwords. They attributed this effect to a de-emphasis of an assembly route in the pure block. The current authors replicated this effect in Experiment 1. In Experiments 2 and 3, similar effects resulted from mixing high- and low-frequency regular words with nonwords and from mixing high- and low-frequency irregular words together. Further, in all cases, the more slowly named stimuli were named faster in mixed blocks than in pure blocks. An alternative to the de-emphasis account, which is based on strategic control of initiation of articulation, was supported in Experiment 4 by confirming the alternative account's novel prediction of a regularity effect for high-frequency words in pure blocks. Implications for the single- versus dual-route debate and for interpretations of strategy effects in general are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Construction of age-related reference limits for 24-h blood pressure pattern

Blood pressure (BP) is recursively variable during the day-night cycle because of a physiological circadian rhythm. The aim of this study is, therefore, to show how to construct the population reference limits (desms) for BP in its time varying 24-h pattern, starting from a small sample, in order to facilitate their use in a local context. The sample for standardization comprised 427 clinically healthy subjects (211 males and 216 females), ranging in age from 16 to 100 years, attending their routine activities. The procedure begins with the statistical biometry related to the sample, and proceeds with the computation of the BP desms related to (1) the time-qualified discrete values; (2) the parameters of circadian rhythm; (3) the daily pressure load. The pertaining rules are explained step by stop, allowing each one to prepare the proper local desms for BP 24-h pattern. These standards may be useful for validating the individual BP monitoring according to the upper limits of the circadian physiological variability in the diagnostic procedure for identifying hypertensive subjects.     

Thiazolium‐Based Catalysts for the Etherification of Benzylic Alcohols under Solvent‐Free Conditions

Thiazolium and imidazolium hybrid materials were prepared by radical reactions between a mercaptopropyl‐modified SBA‐15 mesoporous silica and bis‐vinylthiazolium or bis‐vinylimidazolium dibromide salts. These hybrid materials were characterized by several techniques and were employed in the etherification reaction of 1‐phenylethanol. Solvent‐free conditions at 160 °C under different gas phases (oxygen, air, nitrogen and argon) were used. The thiazolium‐based material displayed excellent performances. Further studies were carried out using unsupported thiazolium salts, with or without a methyl group at the C‐2 position of the thiazolium moiety. These studies allowed us to propose a reaction mechanism. The supported thiazolium‐based material was successfully used in the etherification reaction of two other benzylic alcohols and also in seven consecutive cycles. This work represents the first use of thiazolium‐based compounds as catalysts for the etherification reaction of alcohols.