Buffalo National River Ecosystems - Part II

The priorities were established for the Buffalo National River Ecosystem Studies through meetings and correspondence with Mr. Roland Wauer and other personnel of the Office of Natural Sciences, Southwest Region of the National Park Service. These priorities were set forth in the appendix of contract no. CX 700050443 dated May 21, 1975

Tuning the effects of Landau-level mixing on anisotropic transport in quantum Hall systems

Electron-electron interactions in half-filled high Landau levels in two-dimensional electron gases in a strong perpendicular magnetic field can lead to states with anisotropic longitudinal resistance. This longitudinal resitance is generally believed to arise from broken rotational invariance, which is indicated by charge density wave (CDW) order in Hartree-Fock calculations. We use the Hartree-Fock approximation to study the influence of externally tuned Landau level mixing on the formation of interaction induced states that break rotational invariance in two-dimensional electron and hole systems. We focus on the situation when there are two non-interacting states in the vicinity of the Fermi level and construct a Landau theory to study coupled charge density wave order that can occur as interactions are tuned and the filling or mixing are varied. We examine in detail a specific example where mixing is tuned externally through Rashba spin-orbit coupling. We calculate the phase diagram and find the possibility of ordering involving coupled striped or triangular charge density waves in the two levels. Our results may be relevant to recent transport experiments on quantum Hall nematics in which Landau-level mixing plays an important role.Comment: 25 pages, 6 figure

Evaluation of an alternative transport initiative in Perth, Western Australia 2000-2004

Issue addressed: Perth Western Australia, has the highest proportion of per capita car ownership in Australia. Despite the various health, environmental and traffic-related benefits, the uptake of alternative forms of transportation such as walking, cycling and public transport are low.Methods: In response to a growing reliance on motorised transport, the Department for Planning and Infrastructure's (DPI's) Cycling Unit conducts an annual Bike to Work Breakfast to promote cycling as a viable form of transport to work. During this event a short cross sectional survey is distributed to assess the usual cycling behaviours of attendees. Topical issues relating to cycling are also investigated.Results: Results from the 2004 survey indicated that the majority of respondents cycled at least 2-3 times per week (85%) to improve fitness (88%), for enjoyment (70%) and because it was a cost effective means of transport (45%). Most of the respondents (92%) supported the need for more cycle friendly infrastructure such as advanced stop lines at intersections and safety measures such as wearing cycle helmets (85%). These findings were consistent with results from similar surveys conducted between 2000 and 2003.Conclusions: The DPI's Bike to Work Breakfast is a popular event within the cycling calendar that provides the opportunity to gain a snapshot of cycling behaviours and attitudes of cyclists. Prior consultation with the evaluators in the developed of the survey instrument has the potential to investigate barriers and enablers to cycling on a regular basis. Age and gender differences could also be explored

On Orbital Period Changes in Nova Outbursts

We propose a new mechanism that produces an orbital period change during a nova outburst. When the ejected material carries away the specific angular momentum of the white dwarf, the orbital period increases. A magnetic field on the surface of the secondary star forces a fraction of the ejected material to corotate with the star, and hence the binary system. The ejected material thus takes angular momentum from the binary orbit and the orbital period decreases. We show that for sufficiently strong magnetic fields on the surface of the secondary star, the total change to the orbital period could even be negative during a nova outburst, contrary to previous expectations. Accurate determinations of pre- and post-outburst orbital periods of recurrent nova systems could test the new mechanism, in addition to providing meaningful constraints on otherwise difficult to measure physical quantities. We apply our mechanism to outbursts of the recurrent nova U Sco.Comment: Accepted for publication in MNRA

Clients’ experiences of one-to-one low-intensity interventions for common mental health problems : an interpretative phenomenological analysis

Objectives: Common mental health disorders such as depression and anxiety are highly prevalent and carry significant health care and economic burdens. The UK’s improving access to psychological therapies (IAPT) initiative was developed as a cost-effective way of reducing the pernicious effects of these disorders. IAPT interventions, such as guided self-help, have been subjected to considerable quantitative evaluation. However, there has been minimal investigation into clients’ experiences of the one-to-one low-intensity interventions (LIIs), which form a key component of IAPT service provision. Qualitative exploration could provide rich data regarding experiences of psychological change and factors affecting therapeutic experiences. This will enable informative, client led insights into how low-intensity therapy can be improved. Methods: Interpretative phenomenological analysis of eight semi-structured interviews was used to develop an idiosyncratic understanding of clients’ experiences of one-to-one LIIs following entry into a randomized control trial (RCT). Results: Four superordinate themes were identified from clients’ accounts: goals and expectations of therapy, beneficial aspects of therapy, non-beneficial aspects of therapy, and the experience of psychological change. A heuristic model of interrelationships between factors is proposed. Conclusions: Both therapeutic techniques and relationships contribute to beneficial therapeutic experiences. The results reported here can be used to inform practice by harnessing the most beneficial aspects of therapy, such as developing adaptive therapeutic approaches to clients’ clinical needs and facilitating idiosyncratic processes of psychological change. Due to limited qualitative research in this area, further research should be conducted in different service settings to assess differences and similarities in clients’ experiences

The laurentian record of neoproterozoic glaciation, tectonism, and eukaryotic evolution in Death Vally, California

Neoproterozoic strata in Death Valley, California contain eukaryotic microfossils and glacial deposits that have been used to assess the severity of putative Snowball Earth events and the biological response to extreme environmental change. These successions also contain evidence for syn-sedimentary faulting that has been related to the rifting of Rodinia, and in turn the tectonic context of the onset of Snowball Earth. These interpretations hinge on local geological relationships and both regional and global stratigraphic correlations. Here we present new geological mapping, measured stratigraphic sections, carbon and strontium isotope chemostratigraphy, and micropaleontology from the Neoproterozoic glacial deposits and bounding strata in Death Valley. These new data enable us to refine regional correlations both across Death Valley and throughout Laurentia, and construct a new age model for glaciogenic strata and microfossil assemblages. Particularly, our remapping of the Kingston Peak Formation in the Saddle Peak Hills and near the type locality shows for the first time that glacial deposits of both the Marinoan and Sturtian glaciations can be distinguished in southeastern Death Valley, and that beds containing vase-shaped microfossils are slump blocks derived from the underlying strata. These slump blocks are associated with multiple overlapping unconformities that developed during syn-sedimentary faulting, which is a common feature of Cyrogenian strata along the margin of Laurentia from California to Alaska. With these data, we conclude that all of the microfossils that have been described to date in Neoproterozoic strata of Death Valley predate the glaciations and do not bear on the severity, extent or duration of Neoproterozoic Snowball Earth events

Itinerant Electron Ferromagnetism in the Quantum Hall Regime

We report on a study of the temperature and Zeeman-coupling-strength dependence of the one-particle Green's function of a two-dimensional (2D) electron gas at Landau level filling factor $\nu =1$ where the ground state is a strong ferromagnet. Our work places emphasis on the role played by the itinerancy of the electrons, which carry the spin magnetization and on analogies between this system and conventional itinerant electron ferromagnets. We discuss the application to this system of the self-consistent Hartree-Fock approximation, which is analogous to the band theory description of metallic ferromagnetism and fails badly at finite temperatures because it does not account for spin-wave excitations. We go beyond this level by evaluating the one-particle Green's function using a self-energy, which accounts for quasiparticle spin-wave interactions. We report results for the temperature dependence of the spin magnetization, the nuclear spin relaxation rate, and 2D-2D tunneling conductances. Our calculations predict a sharp peak in the tunneling conductance at large bias voltages with strength proportional to temperature. We compare with experiment, where available, and with predictions based on numerical exact diagonalization and other theoretical approaches.Comment: 29 pages, 20 figure

Increase in Tau Pathology in P290S Mapt Knock-In Mice Crossed with AppNL-G-F Mice

Alzheimer's Disease (AD) is characterized by the pathological assembly of Aβ peptide, which deposits into extracellular plaques, and tau, which accumulates in intraneuronal inclusions. To investigate the link between Aβ and tau pathologies, experimental models featuring both pathologies are needed. We developed a mouse model featuring both tau and Aβ pathologies by knocking the P290S mutation into murine Mapt and crossing these MaptP290S KI mice with the AppNL-G-F KI line. MaptP290S KI mice developed a small number of tau inclusions, which increased with age. The amount of tau pathology was significantly larger in AppNL-G-FxMaptP290S KI mice from 18-months of age onwards. Tau pathology was higher in limbic areas, including hippocampus, amygdala and piriform/entorhinal cortex. We also observed AT100-and Gallyas-Braak-silver-positive dystrophic neurites containing assembled filamentous tau, as visualized by in situ EM. Using a cell-based tau seeding assay, we showed that sarkosyl-insoluble brain extracts from both 18-month-old MaptP290S KI and AppNL-G-FxMaptP290S KI mice were seed-competent, with brain extracts from double KI mice seeding significantly more than those from the MaptP290S KI mice. Finally, we showed that AppNL-G-FxMaptP290S KI mice had neurodegeneration in the piriform cortex from 18-months of age. We suggest that AppNL-G-F x MaptP290S KI mice provide a good model for studying the interactions of aggregation-prone tau, Aβ, neuritic plaques, neurodegeneration and aging