Microstructure of (Fe0.2Co0.8)0.8(Fe2.38Co0.62O4): A Magnetic Oxidation Resistant Composite Formed by Coprecipitation

The metal–ferrite composite (Fe_0.2Co_0.8)_0.8(Fe_2.38Co_0.62O₄) has been studied by X-ray diffractometry measurements and high-resolution transmission electron microscopy. Spinel ferrite occurs in highly crystalline domains 100–150 nm in size, and the iron–cobalt alloy occurs in smaller and less-crystalline domains (10–20 nm). Both phases are heterogeneous in composition. The metal is embedded in the spinel phase, located near the edges, and overlaid by a poorly crystallized layer or misshapen regions containing small spinel crystals and amorphous phases. By annealing under vacuum up to 800°C, the misshapen regions disappear and the size of the metallic regions increases. The concentration of iron in the metallic regions decreases and their structure changes to face-centered cubic, while the spinel becomes enriched in iron.     

Structural evolution in gel-derived mullite precursors

The evolution of mullite from organo-metal gel precursors above 700 °C is found to be strongly influenced in both gel pieces and powdered samples by the thermal pretreatment at lower temperatures. Under the present conditions, the optimum preheating temperature was found to be 350 °C, at which temperature an anomalously high concentration was found of an Al species with a characteristic ²⁷Al magic-angle spinning NMR resonance at about 30 ppm. Such Al sites are often described as pentaco-ordinated, but an alternative assignment is considered. The optimum temperature for the formation of this Al site is also optimal for the catalytic formation of aromatic molecules from the residual organic fragments and/or solvent present. Mass spectrometry shows that under the present reaction conditions, these aromatics are thermally stable up to at least 900 °C in air, and the prolonged presence of their decomposition products (CO and water) could facilitate the transformation of the gel to crystalline mullite. The ²⁹Si NMR spectra indicate at least three different Si environments, including one which may arise from the formation of silicon oxycarbide glasses in these gels.     

Differential effects of hippocampectomy on classically conditioned rabbit nictitating membrane response related to interstimulus interval.

The effects of hippocampal ablation on acquisition rates and temporal characteristics of classically conditioned nictitating membrane responses were examined in 54 New Zealand albino rabbits trained with a 150-, 300-, or 600-msec interstimulus interval. Acquisition rates were accelerated in the 150- and 600-msec groups. No effect was present in the 300-msec group. Response onset latencies were also affected in the 150-msec group. Results indicate that damage to the hippocampus influences the acquisition of classically conditioned responses only when temporal parameters are relatively complex. Findings also support the notion that the hippocampus modulates learned motor behavior by a neural model of the response to be executed. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anticipated affective consequences of physical activity adoption and maintenance.

Objective: The expected emotional consequences of future actions are thought to play an important role in health behavior change. This research examined whether anticipated affective consequences of success and failure vary across stages of physical activity change and differentially predict physical activity adoption as compared to maintenance. Design: Using a prospective design over a 3-month period, a community sample of 329 healthy, middle-aged adults were assessed at 2 time points. Main Outcome Measures: Anticipated positive and negative emotions, stage of behavior change (precontemplation [PC], contemplation [C], preparation [P], action [A], maintenance [M]), and level of physical activity. Results: At baseline, anticipated positive emotions were greater in C versus PC, whereas anticipated negative emotions were greater in M versus A and in M versus P. Higher anticipated positive but not negative emotions predicted physical activity adoption and maintenance after 3 months. Conclusion: Although the expected affective consequences of future success and failure differentiated among individuals in the early and later stages of physical activity change, respectively; only the anticipated affective consequences of success predicted future behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response perseveration in psychopaths.

Prison psychopaths and nonpsychopaths performed a card-playing task involving monetary rewards and punishments under three conditions. In all conditions, the probability of punishment increased by 10% with every block of 10 cards from 10% to 100%. The dependent measure—number of cards played before terminating the task—provided a measure of response perseveration. As predicted, psychopaths played significantly more cards (and lost more money) than did nonpsychopaths when the task involved immediate feedback only. Although providing subjects with a display illustrating their cumulative response feedback did little to reduce this deficit, there were no group differences apparent when cumulative feedback was accompanied by a 5-s waiting period during which subjects were prevented from making another response. The results suggest that procedures designed to reduce psychopaths' maladaptive perseveration by imposing a delay between response feedback and the next opportunity to respond may prove clinically important. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the double-layer structure of the boundary layer adjacent to a sidewall of a differentially heated cavity

This study is concerned with the transition of the boundary layer adjacent to a sidewall of a differentially heated cavity to a double-layer structure and with the important flow and heat transfer features of the double-layer structure. The transition to the double-layer structure is examined by comparing numerical and experimental results. The mechanism responsible for the formation of the double-layer structure, i.e. the stratification of the fluid in the core, is discussed. Detailed discussion of the energy balance adjacent to the sidewall reveals that the heat transfer in the double-layer structure is rather complex. There is an opposing horizontal thermal diffusion within the double-layer structure.     

Isotopic determination of organic keto acid pentafluorobenzyl esters in biological fluids by negative chemical ionization gas chromatography/mass spectrometry.

A rapid, single-step procedure for the extraction and derivatization of organic alpha-keto acids from microliter quantities of human plasma has been developed. The keto acids were analyzed as the pentafluorobenzyl (PFB) ester by methane negative chemical ionization gas chromatography/mass spectrometry. The PFB esters possess excellent chromatographic properties and required no further derivatization to block the keto group. They fragment to produce intense carboxylate anions, often as the sole ion in the spectrum, and offer detection limits below 1 pmol. This derivative is suitable for isotopic analysis of organic keto acids because it does not introduce any additional isotopic complexity into the target molecule. Normal human plasma 4-methyl-2-oxopentanoic acid levels were 34.9 +/- 5.3 mumol.L-1 and could be determined with 1.1% precision by isotope dilution GC/MS. We have used this procedure to study leucine and 4-methyl-2-oxopentanoic acid metabolism by using stable isotopically labeled tracers in a variety of normal and abnormal conditions.