Uranium distribution as a proxy for basin-scale fluid flow in distributive fluvial systems

This work was supported by the Fluvial Systems Research Group sponsors BG Group, BP, Chevron, ConocoPhilips, and Total. We thank reviews from Martin Stokes, an anonymous reviewer and Editor Stuart Jones.Peer reviewedPostprin

Nanoscale Impurity Structures on the Surface of dx2−y2d_{x^2-y^2}-wave Superconductors

We study the effects of nanoscale impurity structures on the local electronic structure of $d_{x^2-y^2}$-wave superconductors. We show that the interplay between the momentum dependence of the superconducting gap, the geometry of the nanostructure and its orientation gives rise to a series of interesting quantum effects. Among these are the emergence of a zero bias conductance peak in the superconductor's density of states and the suppression of impurity states for certain nanostructures. The latter effect can be used to screen impurity resonances in the superconducting state.Comment: 4 pages, 5 figure

Quantification of a distributive fluvial system; the Salt Wash DFS of the Morrison Formation, SW USA

Peer reviewedPostprin

Ab initio study of magnetism at the TiO2/LaAlO3 interface

In this paper we study the possible relation between the electronic and magnetic structure of the TiO2/LaAlO3 interface and the unexpected magnetism found in undoped TiO2 films grown on LaAlO$_3$. We concentrate on the role played by structural relaxation and interfacial oxygen vacancies. LaAlO3 has a layered structure along the (001) direction with alternating LaO and AlO2 planes, with nominal charges of +1 and -1, respectively. As a consequence of that, an oxygen deficient TiO2 film with anatase structure will grow preferently on the AlO2 surface layer. We have therefore performed ab-initio calculations for superlattices with TiO2/AlO2 interfaces with interfacial oxygen vacancies. Our main results are that vacancies lead to a change in the valence state of neighbour Ti atoms but not necessarily to a magnetic solution and that the appearance of magnetism depends also on structural details, such as second neighbor positions. These results are obtained using both the LSDA and LSDA+U approximations.Comment: Accepted for publication in Journal of Materials Scienc

Controls on the apex location of large deltas

Acknowledgements and Funding We would like to acknowledge the sponsors of the Fluvial Systems Research Group consortium BP, BG, Chevron, ConocoPhillips and Total. We would like to thank A. Felicia for image generation and database management.Peer reviewedPublisher PD

Human bony labyrinth is an indicator of population history and dispersal from Africa.

The dispersal of modern humans from Africa is now well documented with genetic data that track population history, as well as gene flow between populations. Phenetic skeletal data, such as cranial and pelvic morphologies, also exhibit a dispersal-from-Africa signal, which, however, tends to be blurred by the effects of local adaptation and in vivo phenotypic plasticity, and that is often deteriorated by postmortem damage to skeletal remains. These complexities raise the question of which skeletal structures most effectively track neutral population history. The cavity system of the inner ear (the so-called bony labyrinth) is a good candidate structure for such analyses. It is already fully formed by birth, which minimizes postnatal phenotypic plasticity, and it is generally well preserved in archaeological samples. Here we use morphometric data of the bony labyrinth to show that it is a surprisingly good marker of the global dispersal of modern humans from Africa. Labyrinthine morphology tracks genetic distances and geography in accordance with an isolation-by-distance model with dispersal from Africa. Our data further indicate that the neutral-like pattern of variation is compatible with stabilizing selection on labyrinth morphology. Given the increasingly important role of the petrous bone for ancient DNA recovery from archaeological specimens, we encourage researchers to acquire 3D morphological data of the inner ear structures before any invasive sampling. Such data will constitute an important archive of phenotypic variation in present and past populations, and will permit individual-based genotype-phenotype comparisons

Vertical trends within the prograding Salt Wash distributive fluvial system, SW USA

This work has been supported by the Fluvial Systems Research Group Consortium Phase 1, supported by BG, Chevron, Conoco Philips and Total. Discussions with John Howell on prograding sequences are greatly appreciated. The authors would also like to thank Anna Kulikova, Guy Prince, Kelsey McNamara and Karen Oud for assistance in the field. We thank reviewer Brian Willis, an anonymous reviewer and Editor Sebastien Castelltort for constructive comments that improved this manuscript.Peer reviewedPostprin

ReducingGroundwater Nitrate in the Judith River Watershed: A Participatory Approach to AchieveEffective Management for Improved Water Quality

Rising levels of nitrate in groundwater threaten human health and downstream ecosystems. In the Judith River Watershed, Montana, groundwater nitrate concentrations frequently exceed 10 mg L-­‐1, and may be increasing due to agricultural practices on thin soils overlying shallow, unconfined aquifers with short groundwater residence :mes. Previous extension and research ac:vi:es in the watershed have provided key data and established working relationships with local stakeholders, but adoption rates of water quality best management practices (BMPs) have been low. With this project, we undertake a participatory approach that engages agricultural producers and stakeholders to

Appearance of room temperature ferromagnetism in Cu-doped TiO2−δ_{2-\delta} films

In recent years there has been an intense search for room temperature ferromagnetism in doped dilute semiconductors, which have many potentially applications in spintronics and optoelectronics. We report here the unexpected observation of significant room temperature ferromagnetism in a semiconductor doped with nonmagnetic impurities, Cu-doped TiO$_2$ thin films grown by Pulsed Laser Deposition. The magnetic moment, calculated from the magnetization curves, resulted surprisingly large, about 1.5 $\mu_B$ per Cu atom. A large magnetic moment was also obtained from ab initio calculations using the supercell method for TiO$_2$ with Cu impurities, but only if an oxygen vacancy in the nearest-neighbour shell of Cu was present. This result suggests that the role of oxygen vacancies is crucial for the appearance of ferromagnetism. The calculations also predict that Cu doping favours the formation of oxygen vacancies.Comment: 4 pages, 3 figures, published in Phys. Rev. B (Rapid Comm.