Power dependence of pure spin current injection by quantum interference

We investigate the power dependence of pure spin current injection in GaAs bulk and quantum-well samples by a quantum interference and control technique. Spin separation is measured as a function of the relative strength of the two transition pathways driven by two laser pulses. By keeping the relaxation time of the current unchanged, we are able to relate the spin separation to the injected average velocity. We find that the average velocity is determined by the relative strength of the two transitions in the same way as in classical interference. Based on this, we conclude that the density of injected pure spin current increases monotonically with the excitation laser intensities. The experimental results are consistent with theoretical calculations based on Fermi's golden rule.Comment: 6 pages, 4 figure

Hunter-Gatherer Inter-Band Interaction Rates: Implications for Cumulative Culture

Our species exhibits spectacular success due to cumulative culture. While cognitive evolution of social learning mechanisms may be partially responsible for adaptive human culture, features of early human social structure may also play a role by increasing the number potential models from which to learn innovations. We present interview data on interactions between same-sex adult dyads of Ache and Hadza hunter-gatherers living in multiple distinct residential bands (20 Ache bands; 42 Hadza bands; 1201 dyads) throughout a tribal home range. Results show high probabilities (5%–29% per year) of cultural and cooperative interactions between randomly chosen adults. Multiple regression suggests that ritual relationships increase interaction rates more than kinship, and that affinal kin interact more often than dyads with no relationship. These may be important features of human sociality. Finally, yearly interaction rates along with survival data allow us to estimate expected lifetime partners for a variety of social activities, and compare those to chimpanzees. Hadza and Ache men are estimated to observe over 300 men making tools in a lifetime, whereas male chimpanzees interact with only about 20 other males in a lifetime. High intergroup interaction rates in ancestral humans may have promoted the evolution of cumulative culture

Sensory and repetitive behaviors among children with autism spectrum disorder at home

Atypical sensory and repetitive behaviors are defining features of autism spectrum disorder (ASD) and are thought to be influenced by environmental factors; however, there is a lack of naturalistic research exploring contexts surrounding these behaviors. The current study involved video recording observations of 32 children with ASD (2 – 12 years of age) engaging in sensory and repetitive behaviors during home activities. Behavioral coding was used to determine what activity contexts, sensory modalities, and stimulus characteristics were associated with specific behavior types: hyperresponsive, hyporesponsive, sensory seeking, and repetitive/stereotypic. Results indicated that hyperresponsive behaviors were most associated with activities of daily living and family-initiated stimuli, whereas sensory seeking behaviors were associated with free play activities and child-initiated stimuli. Behaviors associated with multiple sensory modalities simultaneously were common, emphasizing the multi-sensory nature of children’s behaviors in natural contexts. Implications for future research more explicitly considering context are discussed

The Segmented Aperture Interferometric Nulling Testbed (SAINT) III: Control Systems Analysis and Preliminary Results

This work presents a detailed current performance analysis for the telescope, pointing, and coronagraph com- ponent subsystems of the Segmented Aperture Interferometric Nulling Testbed (SAINT). The project pairs an active segmented mirror with the Visible Nulling Coronagraph (VNC) towards demonstrating capabilities for the future space observatories needed to directly detect and characterize Earth-sized worlds around nearby stars. We describe approaches to optimize subsystem wavefront sensing and control parameters, summarizing relevant scal- ing relations between these parameters, residual errors, and observed contrast measurements. Preliminary results from diagnostic testing under various control states are presented along with intermediate contrast measurements towards demonstrating the full system

Evidence-Based Behavioral Interventions for Repetitive Behaviors in Autism

Restricted and repetitive behaviors (RRBs) are a core symptom of autism spectrum disorders (ASD). There has been an increased research emphasis on repetitive behaviors; however, this research primarily has focused on phenomenology and mechanisms. Thus, the knowledge base on interventions is lagging behind other areas of research. The literature suggests there are evidence-based practices to treat “lower order” RRBs in ASD (e.g., stereotypies); yet, there is a lack of a focused program of intervention research for “higher order” behaviors (e.g., insistence on sameness). This paper will (a) discuss barriers to intervention development for RRBs; (b) review evidence-based interventions to treat RRBs in ASD, with a focus on higher order behaviors; and (c) conclude with recommendations for practice and research

Feasibility of exposure response prevention to treat repetitive behaviors of children with autism and an intellectual disability: A brief report

There is a lack of evidence-based behavioral therapies or pharmacotherapies to treat repetitive behaviors found in autism. Effective behavioral therapies are needed to counter any negative consequences these behaviors may have on the child’s early learning and socialization. The purpose of this proof-of-principle study was to test the feasibility of modifying exposure response prevention, an evidence-based strategy for obsessive–compulsive disorder, to treat the repetitive behaviors found in autism. Five school-aged participants (ages 5–11) diagnosed with an autism spectrum disorder participated in the study. Our preliminary findings suggest it is feasible, and potentially efficacious, to modify standard exposure response prevention to treat the specific forms of repetitive behaviors found in individuals with autism and comorbid intellectual disabilities. A larger clinical trial is needed to substantiate these preliminary findings

Comparing aging and fitness effects on brain anatomy

Recent studies suggest that cardiorespiratory fitness (CRF) mitigates the brain’s atrophy typically associated with aging, via a variety of beneficial mechanisms. One could argue that if CRF is generally counteracting the negative effects of aging, the same regions that display the greatest age-related volumetric loss should also show the largest beneficial effects of fitness. To test this hypothesis we examined structural MRI data from 54 healthy older adults (ages 55–87), to determine the overlap, across brain regions, of the profiles of age and fitness effects. Results showed that lower fitness and older age are associated with atrophy in several brain regions, replicating past studies. However, when the profiles of age and fitness effects were compared using a number of statistical approaches, the effects were not entirely overlapping. Interestingly, some of the regions that were most influenced by age were among those not influenced by fitness. Presumably, the age-related atrophy occurring in these regions is due to factors that are more impervious to the beneficial effects of fitness. Possible mechanisms supporting regional heterogeneity may include differential involvement in motor function, the presence of adult neurogenesis, and differential sensitivity to cerebrovascular, neurotrophic and metabolic factors

Limitation of Algal Growth by Iron Deficiency in the Australian Subantarctic Region

In March 1998 we measured iron in the upper water column and conducted iron- and nutrient-enrichment bottle-incubation experiments in the open-ocean Subantarctic region southwest of Tasmania, Australia. In the Subtropical Convergence Zone (∼42°S, 142°E), silicic acid concentrations were low (\u3c 1.5μM) in the upper water column, whereas pronounced vertical gradients in dissolved iron concentration (0.12-0.84 nM) were observed., presumably reflecting the interleaving of Subtropical and Subantarctic waters, and mineral aerosol input. Results of a bottle-incubation experiment performed at this location indicate that phytoplankton growth rates were limited by iron deficiency within the iron-poor layer of the euphotic zone. In the Subantarctic water mass (∼46.8°S, 142°E), low concentrations of dissolved iron (0.05-0.11nM) and silicic acid (\u3c 1μM) were measured throughout the upper water column, and our experimental results indicate that algal growth was limited by iron deficiency. These observations suggest that availability of dissolved iron is a primary factor limiting phytoplankton growth over much of the Subantarctic Southern Ocean in the late summer and autumn