Circadian (daily) regulation of metabolic pathways implies that food may be metabolized differentially over the daily cycle. To test that hypothesis, we monitored the metabolism of older subjects in a whole-room respiratory chamber over two separate 56-h sessions in a random crossover design. In one session, one of the 3 daily meals was presented as breakfast, whereas in the other session, a nutritionally equivalent meal was presented as a lateevening snack. The duration of the overnight fast was the same for both sessions. Whereas the two sessions did not differ in overall energy expenditure, the respiratory exchange ratio (RER) was different during sleep between the two sessions. Unexpectedly, this difference in RER due to daily meal timing was not due to daily differences in physical activity, sleep disruption, or core body temperature (CBT). Rather, we found that the daily timing of nutrient availability coupled with daily/circadian control of metabolism drives a switch in substrate preference such that the late-evening Snack Session resulted in significantly lower lipid oxidation (LO) compared to the Breakfast Session. Therefore, the timing of meals during the day/night cycle affects how ingested food is oxidized or stored in humans, with important implications for optimal eating habits.

Controlled-geometry voids were introduced into unimplanted and Ti-implanted high-purity c-axis sapphire substrates using microfabrication techniques and ion beam etching, and subsequently transferred to an internal interface by hot-pressing. The morphological evolution of cracklike and channellike defects oriented parallel to the basal plane in response to anneals at 1700°C was studied. The healing behavior of defects in the unimplanted and Ti-ionimplanted samples differs significantly. Ti additions appear to reverse the directional dependence of the healing characteristics in undoped sapphire, greatly stabilizing defects with edges aligned along the [IT001 direction, while reducing the stability of defects with edges aligned parallel to the [1120] direction relative to unimplanted sapphire. The healing characteristics of unimplanted and Ti-implanted sapphire substrates are compared and contrasted with those observed previously in Ca-and Mg-ion-implanted sapphire.

Controlled-geometry voids were introduced into Mgimplanted and Ca-implanted sapphire substrates using microfabrication techniques and ion beam etching, and were subsequently transferred to an internal interface by hot-pressing. The morphological evolution of cracklike and channel-like defects in response to anneals at 1700°C was studied. The healing behavior of defects in the Ca-and Mgion-implanted samples differs significantly. Mg additions appear to reduce the directional dependence of the healing characteristics and thus homogenize the evolution. Destabilization of the basal plane by Ca may contribute to the rapid healing of cracks oriented parallel to the basal plane. The healing characteristics of pore channels in Ca-implanted samples indicate a strong residual energetic barrier to healing stemming from surface energy anisotropy. Despite this, defects in Ca-implanted sapphire healed more rapidly than crystallographically and geometrically identical defects in Mg-implanted sapphire. Thus, the results suggest that Ca additions increase transport rates sufficiently to more than compensate for the relatively higher energetic barriers to pore channel breakup.

Increased fatigue is a predictor of morbidity and mortality in older adults. Fatigability defines a change in performance or self-reported fatigue in response to physical activity (PA). However, the relationship of fatigability to PA-related energy expenditure (PAEE) is unknown. Changes in performance, fatigue, and energy expenditure were measured simultaneously in 17 adults (11 females, 74-94 years old) performing eight standardized PA tasks with various energy expenditure requirements in a whole-room indirect calorimeter. Change in performance was objectively measured using a PA movement monitor and change in fatigue was self-reported on a seven-point scale for each task. Performance and perceived fatigability severity scores were calculated as a ratio of change in performance and fatigue, respectively, and PAEE. We found that change in both objective performance and self-reported fatigue were associated with energy expenditure (Spearman rho = -0.72 and -0.68, respectively, p < 0.001) on a task requiring relatively high level of energy expenditure. The performance and perceived fatigability severity scores were significantly correlated (rho = 0.77, p < 0.001) on this task. In summary, results of this proof of concept pilot study show that both perceived and performance fatigability severity scores are related to PAEE-induced fatigue on a task requiring relatively high level of energy expenditure. We conclude that fatigability severity is a valid measure of PAEE-induced fatigue in older adults.

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Integrated gasification fuel cell (IGFC)