Special issue: Illuminating occupations at the heart of social problems

As this special issue of the Journal of Occupational Science goes to press, the timing seems particularly pertinent to consider the intersection between how society and the rise of social problems impact upon and are influenced by the occupational lives that people, as individuals and collectives, lead. It seems that in all domains of life - work, school, home, leisure, and others - people are having to navigate the challenges of adapting their current occupations or adapting to new occupations as they seek to maintain the health and well-being of themselves and those around them. It is in times of such uncertainty that the complexity of occupation, as central to social life, becomes more visible to a range of societal actors. Drawing on liberatory pedagogical theory in occupation-based learning, Simaan illuminates a classroom activity using his research on occupations associated with olive growing in Palestine

Fermi-surface transformation across the pseudogap critical point of the cuprate superconductor La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_4

The electrical resistivity $\rho$ and Hall coefficient R$_H$ of the tetragonal single-layer cuprate Nd-LSCO were measured in magnetic fields up to $H = 37.5$ T, large enough to access the normal state at $T \to 0$, for closely spaced dopings $p$ across the pseudogap critical point at $p^\star = 0.235$. Below $p^\star$, both coefficients exhibit an upturn at low temperature, which gets more pronounced with decreasing $p$. Taken together, these upturns show that the normal-state carrier density $n$ at $T = 0$ drops upon entering the pseudogap phase. Quantitatively, it goes from $n = 1 + p$ at $p = 0.24$ to $n = p$ at $p = 0.20$. By contrast, the mobility does not change appreciably, as revealed by the magneto-resistance. The transition has a width in doping and some internal structure, whereby R$_H$ responds more slowly than $\rho$ to the opening of the pseudogap. We attribute this difference to a Fermi surface that supports both hole-like and electron-like carriers in the interval $0.2 < p < p^\star$, with compensating contributions to R$_H$. Our data are in excellent agreement with recent high-field data on YBCO and LSCO. The quantitative consistency across three different cuprates shows that a drop in carrier density from $1 + p$ to $p$ is a universal signature of the pseudogap transition at $T=0$. We discuss the implication of these findings for the nature of the pseudogap phase.Comment: 11 pages, 12 figure

Human influences on historical and current wildlife distributions from Lewis & Clark to today

Although it is well known that humans are strong modifiers of their environment, there is a need for greater understanding of human-wildlife interactions, both historically as well as currently. Historical journals can help shed light on early human-wildlife interactions, and the Lewis & Clark journals contain some of the earliest and detailed written descriptions of a large part of the United States before Euro-American settlement. I used the journal entries to assess the influence of humans on wildlife distribution and abundance. Areas with denser human population, the Columbia Basin and the Pacific Coast, had lower species diversity and abundance of large mammals. The opposite was observed on the Plains. Overhunting before Euro- American contact accentuated by the introduction of the horse may have been major contributors responsible for the historic absence of some species that are present in the archaeological record. The information gained from the Lewis & Clark journals shows the considerable human influence on wildlife under relatively low human population densities. This has major implications for conservation biology and ecological restoration, since human influence is often underestimated when considering the pre-settlement condition. Species ranges are dynamic and change greatly over time. In order to identify large-scale patterns in range contractions and/or expansions, I compared historic and current geographical ranges of 43 North American carnivores and ungulates. Seventeen of the species had undergone range contractions over >20% of their historic range. In areas of higher human influence, species were more likely to contract and less likely to persist. Species richness declined considerably since historic times, and the temperate grasslands and temperate broadleaf/mixed forest biomes lost the highest average number of species, while the boreal forest and tundra showed fewer numbers of species lost. The study of species range changes contributed new quantitative information about human influences on range contractions in North America. The results can be used to improve our knowledge of historical reference conditions, for the creation of wildlife reserves, and for wildlife re-introductions

The use of remote sensing and Geographic Information Systems (GIS) in assessing changes in stream morphology and vegetation

Remote sensing and Geographic Information Systems (GIS) are well known tools for the study of time change analysis in natural systems. However, long-term studies of riparian systems using large-scale aerial photography are less common. The purpose of this project was to combine large scale aerial photography, GIS, Global Positioning Systems (GPS) and ground truthing for conducting a time change analysis study of an eastern Oregon riparian area over a 20 year time period. The objectives were to assess changes in stream morphology and vegetation that occurred in grazed and exclosed areas from 1979 to 1998. In addition, the viability of using large-scale (1:4000) aerial photography combined with GIS/GPS and ground truthing in this study was evaluated. GIS layers of vegetation and stream morphology parameters were developed from geocorrected images. Ground truthing included the collection of vegetation and stream channel measurements. In addition, older aerial photography and previously collected survey data were available for this study. The area of land changing to water and vice versa was calculated over the 41 ha large study area. This area of change (3.65 ha) was slightly larger than the area of no change (3.2 ha). The length of the thalweg and streambank, sinuosity and stream area remained relatively the same. Most of the changes were associated with the islands. Their number decreased, but their area increased, suggesting an increase in stability. Stream width decreased in both grazed and exclosed sites. Shrub and tree cover increased from 1979 to 1998 over the whole study area from 23% to 34%, and this increase was similar in grazed and exclosed sites. The variability of shrub/tree cover within and between the grazed and exclosed sites was high. Topography and stream dynamics appeared to control changes in stream morphology, including erosion, deposition and island formation. We could find no association between the observed changes and the grazing treatment. The use of large-scale aerial photography, GIS and GPS proved to be a powerful tool for detecting change over time and it is expected that these techniques will become more common in rangeland analysis. It is anticipated that the methods used in this study can be applied to and will help in monitoring of other rangeland streams

The ecological boundaries of six Carolina bays: Community composition and ecotone distribution

Community and environmental gradients within the ecological boundaries of Carolina bay wetlands may provide important information on the interaction between Carolina bays and associated uplands, and may also provide guidance for improved management. We established twelve 30-m transects on the sloping rims of each of six Carolina bays in northeastern South Carolina to characterize the community gradient, as well as important environmental factors producing this gradient. Mid-points of the transects were placed on jurisdictional wetland boundaries. Hydrology, soil properties, and plant species composition were measured within these transects. On average, transects included an elevation change of 0.6 m that corresponded with gradients of hydrology, soil properties, and community characteristics. Decreasing surface soil moisture (i.e., fewer flood events) and decreasing soil nutrients were associated with a shift from shrub-bog vegetation with relatively low alpha diversity and prominence of evergreens to a relatively diverse and heterogeneous community characterized by grasses, herbs, low shrubs, and vines. Ecotones, identified by abrupt changes in community composition, were more frequently found outside jurisdictional wetland boundaries. Likewise, five near-endemic and endemic plant species were found outside the wetland boundaries. Our data reinforce the need for better understanding of how Carolina bays interact with adjacent landscape elements, and specifically how ecological boundaries are influenced by this interaction

Evidence for a small hole pocket in the Fermi surface of underdoped YBa2Cu3Oy

The Fermi surface of a metal is the fundamental basis from which its properties can be understood. In underdoped cuprate superconductors, the Fermi surface undergoes a reconstruction that produces a small electron pocket, but whether there is another, as yet undetected portion to the Fermi surface is unknown. Establishing the complete topology of the Fermi surface is key to identifying the mechanism responsible for its reconstruction. Here we report the discovery of a second Fermi pocket in underdoped YBa2Cu3Oy, detected as a small quantum oscillation frequency in the thermoelectric response and in the c-axis resistance. The field-angle dependence of the frequency demonstrates that it is a distinct Fermi surface and the normal-state thermopower requires it to be a hole pocket. A Fermi surface consisting of one electron pocket and two hole pockets with the measured areas and masses is consistent with a Fermi-surface reconstruction caused by the charge-density-wave order observed in YBa2Cu3Oy, provided other parts of the reconstructed Fermi surface are removed by a separate mechanism, possibly the pseudogap.Comment: 23 pages, 5 figure