Nondiffusive spin dynamics in a two-dimensional electron gas

We describe measurements of spin dynamics in the two-dimensional electron gas in GaAs=GaAlAs quantum wells. Optical techniques, including transient spin-grating spectroscopy, are used to probe the relaxation rates of spin polarization waves in the wave vector range from zero to 6 x 104 cm-1. We find that the spin polarization lifetime is maximal at a nonzero wave vector, in contrast with expectations based on ordinary spin diffusion, but in quantitative agreement with recent theories that treat diffusion in the presence of spin-orbit couplin

The Relationship of Implicit Theories to Elementary Teachers’ Patterns of Engagement in a Mathematics-Focused Professional Development Setting

As elementary teachers aim to deepen their mathematical understandings, they engage in a relearning process that involves not only revisiting but also reconstructing their knowledge. To do so, meaningful engagement in immersion and practice-based experiences is required. This exploratory case study investigated the engagement patterns of two elementary teachers with varying implicit beliefs as they participated in a professional development that focused on relearning mathematics. Data were collected on the two participants in the form of video narratives, observation protocols, and interviews. Attention was given to their patterns of engagement in collaborative group settings as the participants moved through different phases of the professional development lesson. Results indicated that the engagement patterns of the two participants closely aligned with learning behaviors described in the implicit beliefs theory. In this way, the results suggested an extension of the implicit theories model to the relearning context. Additional implications and future questions are provided

The role of gaping behaviour in habitat partitioning between coexisting intertidal mussels

Background Environmental heterogeneity plays a major role in invasion and coexistence dynamics. Habitat segregation between introduced species and their native competitors is usually described in terms of different physiological and behavioural abilities. However little attention has been paid to the effects of behaviour in habitat partitioning among invertebrates, partially because their behavioural repertoires, especially marine benthic taxa, are extremely limited. This study investigates the effect of gaping behaviour on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. These two species show partial habitat segregation on the south coast of South Africa, the lower and upper areas of the mussel zone are dominated by P. perna and M. galloprovincialis respectively, with overlap in the middle zone. During emergence, intertidal mussels will either keep the valves closed, minimizing water loss and undergoing anaerobic metabolism, or will periodically open the valves maintaining a more efficient aerobic metabolism but increasing the risk of desiccation. Results Our results show that, when air exposed, the two species adopt clearly different behaviours. M. galloprovincialis keeps the shell valves closed, while P. perna periodically gapes. Gaping behaviour increased water loss in the indigenous species, and consequently the risk of desiccation. The indigenous species expressed significantly higher levels of stress protein (Hsp70) than M. galloprovincialis under field conditions and suffered significantly higher mortality rates when exposed to air in the laboratory. In general, no intra-specific differences were observed in relation to intertidal height. The absence of gaping minimises water loss but exposes the invasive species to other stresses, probably related to anoxic respiration. Conclusions Gaping affects tolerance to desiccation, thus influencing the vertical zonation of the two species. Valve closure exposes the invasive species to higher stress and associated energy demands, but it minimizes water loss, allowing this species to dominate the upper mussel zone, where the gaping indigenous P. perna cannot survive. Thus even very simple behaviour can influence the outcome of interactions between indigenous and invasive species

Host movement dominates the predicted effects of climate change on parasite transmission between wild and domestic mountain ungulates

Climate change is shifting the transmission of parasites, which is determined by host density, ambient temperature and moisture. These shifts can lead to increased pressure from parasites, in wild and domestic animals, and can impact the effectiveness of parasite control strategies. Understanding the interactive effects of climate on host movement and parasite life histories will enable targeted parasite management, to ensure livestock productivity and avoid additional stress on wildlife populations. To assess complex outcomes under climate change, we applied a gastrointestinal nematode transmission model to a montane wildlife–livestock system, based on host movement and changes in abiotic factors due to elevation, comparing projected climate change scenarios with the historic climate. The wildlife host, Alpine ibex (Capra ibex ibex), undergoes seasonal elevational migration, and livestock are grazed during the summer for eight weeks. Total parasite infection pressure was more sensitive to host movement than to the direct effect of climatic conditions on parasite availability. Extended livestock grazing is predicted to increase parasite exposure for wildlife. These results demonstrate that movement of different host species should be considered when predicting the effects of climate change on parasite transmission, and can inform decisions to support wildlife and livestock health.<br/

Using expletives to enhance therapeutic outcomes: A case report

# Background Swearing deserves attention in the physical therapy setting due to its potential positive effects on pain, physical performance, and therapeutic alliance. The purpose of this case report is to describe the strategic use of swearing in the clinical setting. # Case Presentation A 44-year-old female completed an episode of physical therapy after undergoing patellofemoral arthroplasty. Swearing was formally included into the plan of care, and the patient swore out loud during the most challenging and painful interventions. # Results The patient reported that repeating a swear word was funny, distracted the patient, and made the patient feel more confident. The patient and physical therapist self-reported a strong therapeutic alliance. # Conclusion There is evidence repeating a swear word out loud can strengthen the therapeutic alliance, improve physical performance, and decrease pain. This is, to our knowledge, the first report of a patient swearing during an episode of physical therapy care

Approximating Mexican highways with slime mould

Plasmodium of Physarum polycephalum is a single cell visible by unaided eye. During its foraging behavior the cell spans spatially distributed sources of nutrients with a protoplasmic network. Geometrical structure of the protoplasmic networks allows the plasmodium to optimize transport of nutrients between remote parts of its body. Assuming major Mexican cities are sources of nutrients how much structure of Physarum protoplasmic network correspond to structure of Mexican Federal highway network? To find an answer undertook a series of laboratory experiments with living Physarum polycephalum. We represent geographical locations of major cities by oat flakes, place a piece of plasmodium in Mexico city area, record the plasmodium's foraging behavior and extract topology of nutrient transport networks. Results of our experiments show that the protoplasmic network formed by Physarum is isomorphic, subject to limitations imposed, to a network of principle highways. Ideas and results of the paper may contribute towards future developments in bio-inspired road planning

Structural basis of synaptic vesicle assembly promoted by α-synuclein.

α-synuclein (αS) is an intrinsically disordered protein whose fibrillar aggregates are the major constituents of Lewy bodies in Parkinson's disease. Although the specific function of αS is still unclear, a general consensus is forming that it has a key role in regulating the process of neurotransmitter release, which is associated with the mediation of synaptic vesicle interactions and assembly. Here we report the analysis of wild-type αS and two mutational variants linked to familial Parkinson's disease to describe the structural basis of a molecular mechanism enabling αS to induce the clustering of synaptic vesicles. We provide support for this 'double-anchor' mechanism by rationally designing and experimentally testing a further mutational variant of αS engineered to promote stronger interactions between synaptic vesicles. Our results characterize the nature of the active conformations of αS that mediate the clustering of synaptic vesicles, and indicate their relevance in both functional and pathological contexts

Non-diffusive spin dynamics in a two-dimensional electrongas

We describe measurements of spin dynamics in thetwo-dimensional electron gas in GaAs/GaAlAs quantum wells. Opticaltechniques, including transient spin-grating spectroscopy, are used toprobe the relaxation rates of spin polarization waves in the wavevectorrange from zero to 6E4 cm-1. We find that the spin polarization lifetimeis maximal at nonzero wavevector, in contrast with expectation based onordinary spin diffusion, but in quantitative agreement with recenttheories that treat diffusion in the presence of spin-orbitcoupling

Cellular automaton supercolliders

Gliders in one-dimensional cellular automata are compact groups of non-quiescent and non-ether patterns (ether represents a periodic background) translating along automaton lattice. They are cellular-automaton analogous of localizations or quasi-local collective excitations travelling in a spatially extended non-linear medium. They can be considered as binary strings or symbols travelling along a one-dimensional ring, interacting with each other and changing their states, or symbolic values, as a result of interactions. We analyse what types of interaction occur between gliders travelling on a cellular automaton `cyclotron' and build a catalog of the most common reactions. We demonstrate that collisions between gliders emulate the basic types of interaction that occur between localizations in non-linear media: fusion, elastic collision, and soliton-like collision. Computational outcomes of a swarm of gliders circling on a one-dimensional torus are analysed via implementation of cyclic tag systems