Structure of the silicon vacancy in 6H-SiC after annealing identified as the carbon vacancy–carbon antisite pair

We investigated radiation-induced defects in neutron-irradiated and subsequently annealed 6H-silicon carbide (SiC) with electron paramagnetic resonance (EPR), the magnetic circular dichroism of the absorption (MCDA), and MCDA-detected EPR (MCDA-EPR). In samples annealed beyond the annealing temperature of the isolated silicon vacancy we observed photoinduced EPR spectra of spin S=1 centers that occur in orientations expected for nearest neighbor pair defects. EPR spectra of the defect on the three inequivalent lattice sites were resolved and attributed to optical transitions between photon energies of 999 and 1075 meV by MCDA-EPR. The resolved hyperfine structure indicates the presence of one single carbon nucleus and several silicon ligand nuclei. These experimental findings are interpreted with help of total energy and spin density data obtained from the standard local-spin density approximation of the density-functional theory, using relaxed defect geometries obtained from the self-consistent charge density-functional theory based tight binding scheme. We have checked several defect models of which only the photoexcited spin triplet state of the carbon antisite–carbon vacancy pair (CSi-VC) in the doubly positive charge state can explain all experimental findings. We propose that the (CSi-VC) defect is formed from the isolated silicon vacancy as an annealing product by the movement of a carbon neighbor into the vacancy

Cognitive Reserve and the Prevention of Dementia: the Role of Physical and Cognitive Activities

Purpose of Review: The article discusses the two most significant modifiable risk factors for dementia, namely, physical inactivity and lack of stimulating cognitive activity, and their effects on developing cognitive reserve. Recent Findings: Both of these leisure-time activities were associated with significant reductions in the risk of dementia in longitudinal studies. In addition, physical activity, particularly aerobic exercise, is associated with less age-related gray and white matter loss and with less neurotoxic factors. On the other hand, cognitive training studies suggest that training for executive functions (e.g., working memory) improves prefrontal network efficiency, which provides support to brain functioning in the face of cognitive decline. Summary: While physical activity preserves neuronal structural integrity and brain volume (hardware), cognitive activity strengthens the functioning and plasticity of neural circuits (software), thus supporting cognitive reserve in different ways. Future research should examine whether lifestyle interventions incorporating these two domains can reduce incident dementia

Fragmentation in archaeological context – studying the incomplete

International audienceThis introduction provides an overview of fragments and fragmentation in archaeology, aiming to map out a field that has rarely been subjected to synthesising efforts. First, it presents a background, taking John Chapman’s publication of ‘Fragmentation in Archaeology’ in 2000 as a starting point. It then moves on to explore issues within the wide range of perspectives on fragmented materials and fragmentation that have emerged during recent decades. Four themes where the archaeology of fragmentation has proven particularly creative are discussed: the ontological and existential character of fragments; fragmentation and the human body; methodological considerations regarding fragmented materials and their properties; and finally, the links between fragmentation studies and relational perspectives currently influencing many areas of archaeological thinking. Overall, it also gives an approach to the other contributions in this volume and places them in their theoretical and methodological context. Concluding reflections highlight some wider aspects of fragments as part of ever-changing assemblages, as well as the role of fragmentation as a means of embracing the complexity of past remains

The psychophysiological influence of exertion and affect on sport-specific cognitive and physical performance

Objectives: The purpose of the present study was to examine differences in cognitive and physical performance, affective states, perceived exertion, and physiological responses between trials with cognitive, physical, or combined cognitive and physical load. Design: Randomised cross-over trial. Methods: Highly trained competitive orienteers (n = 15 men; n = 10 women) completed three randomised trials comprised of: (1) sport-specific cognitive tests; (2) 35-minute cycling time trial; and (3) combined sport-specific cognitive tests and 35-minute cycling time trial. Measures taken during the trials recorded affective states, perceived exertion, heart rate, blood lactate, cycling watts, as well as working memory, updating, planning and decision making. Results: No significant differences in cognitive performance accuracy were observed within or across trials although reaction times improved within trials and were fastest in the combined trial. Blood lactate, heart rate, perceived exertion, negative affective states, and watts were highest in the physical trial. Conclusions: The combined load of undertaking sport-specific cognitive tests and a cycling time trial did not influence cognitive performance accuracy. Athletes produced greater watts when completing the physical task independently compared with the combined trial, however psychophysiological responses were worse. Further investigation is warranted to determine whether athletes' attentional focus underpins psychophysiological responses to dual-task sport performance

Occupational cognitive complexity and episodic memory in old age

The aim of this study was to investigate occupational cognitive complexity of main lifetime occupation in relation to level and 15-year change in episodic memory recall in a sample of older adults (≥ 65 years, n = 780). We used latent growth curve modelling with occupational cognitive complexity (O*NET indicators) as independent variable. Subgroup analyses in a sample of middle-aged (mean: 49.9 years) men (n = 260) were additionally performed to investigate if a general cognitive ability (g) factor at age 18 was predictive of future occupational cognitive complexity and cognitive performance in midlife. For the older sample, a higher level of occupational cognitive complexity was related to a higher level of episodic recall (β = 0.15, p < .001), but the association with rate of change (β = 0.03, p = .64) was not statistically significant. In the middle-aged sample, g at age 18 was both directly (β = 0.19, p = .01) and indirectly (via years of education after age 18, ab = 0.19) predictive of midlife levels of occupational cognitive complexity. Cognitive ability at age 18 was also a direct predictor of midlife episodic recall (β = 0.60, p ≤ 0.001). Critically, entry of the early adult g factor attenuated the association between occupational complexity and cognitive level (from β = 0.21, p = .01 to β = 0.12, p = .14). Overall, our results support a pattern of preserved differentiation from early to late adulthood for individuals with different histories of occupational complexity