31,808 research outputs found
Optical control of electric-field poling in LiTaO<sub>3</sub>
We present a room temperature technique for optically inducing periodic domain-inverted structures in bulk (0.2mm thick) LiTaO3. By simultaneous application of an electric field and patterned illumination using UV wavelengths (351nm and 364nm) we demonstrate modulation of the resulting domain profile. We discuss the origins of the observed optical effect and describe our results from repeated domain switching, by cycling the electric field
The effects of local demographic characteristics and state-level legislation on foreclosure rates
Problems in the housing sector have prompted research into the causes of default by borrowers. The terms of the loans that were made, the characteristics of borrowers, and local economic conditions, among other factors, all contributed significantly to differences in default rates. State-level legislation may also have played a role by making it more costly for lenders in some states to proceed to foreclose on defaulted mortgages.Housing ; Foreclosure ; Mortgage loans
British surfers and their attitudes and values toward the environment
The purpose of this study was to examine the attitudes of British surfers toward their environment. Eight surfers were interviewed and their views analyzed using an inductive thematic analysis to explore their perceptions of the factors that have influenced their engagement in proenvironmental behaviors. The findings suggest that surfers (in this sample), while motivated to engage in proenvironmental behaviors, are also influenced by a range of factors and appear to be primarily motivated by their identification and a need to maintain their experience of that sport. This reveals an inherent dilemma. Through their sport surfers are able to observe the effects of environmental degradation on the environment (e.g., polluted water), the ecosystem, and on their personal health. However, they are also aware of the trade-offs required in pursuing their sport that may damage the environment (e.g., toxic material involved in sport kit manufacture). When questioned, surfers stated they would be unwilling to give up their sport even at the cost of the environment in which those activities are experienced. This highlights a possibly common problem among environmentally minded outdoor enthusiasts: when do personal benefits outweigh the responsibilities of environmental stewardship? The value of these findings is discussed in relation to the promotion of proenvironmental behaviors and engagement with proenvironmental groups
Charge Distribution Near Oxygen Vacancies in Reduced Ceria
Understanding the electronic charge distribution around oxygen vacancies in
transition metal and rare earth oxides is a scientific challenge of
considerable technological importance. We show how significant information
about the charge distribution around vacancies in cerium oxide can be gained
from a study of high resolution crystal structures of higher order oxides which
exhibit ordering of oxygen vacancies. Specifically, we consider the
implications of a bond valence sum analysis of CeO and
CeO. To illuminate our analysis we show alternative
representations of the crystal structures in terms of orderly arrays of
co-ordination defects and in terms of flourite-type modules. We found that in
CeO, the excess charge resulting from removal of an oxygen atom
delocalizes among all three triclinic Ce sites closest to the O vacancy. In
CeO, the charge localizes on the next nearest neighbour Ce atoms.
Our main result is that the charge prefers to distribute itself so that it is
farthest away from the O vacancies. This contradicts \emph{the standard picture
of charge localisation} which assumes that each of the two excess electrons
localises on one of the cerium ions nearest to the vacancy. This standard
picture is assumed in most calculations based on density functional theory
(DFT). Based on the known crystal structure of PrO, we also
predict that the charge in CeO will be found in the second
coordination shell of the O vacancy. Although this review focuses on bulk
cerium oxides our approach to characterising electronic properties of oxygen
vacancies and the physical insights gained should also be relevant to surface
defects and to other rare earth and transition metal oxides.Comment: 20 pages, 23 figures. The replacement file has a new format for the
figures are the document layout but no change in content. v3 has the
following main changes: 1. The abstract and introduction were extensively
revised. 2. Sec. IV was removed. 3. The Conclusion was rewritte
Application of a panel method to wake-vortex/wing interaction and comparison with experimental data
The ability of the Vortex Separation AEROdynamics (VSAERO) program to calculate aerodynamic loads on wings due to interaction with free vortices was studied. The loads were calculated for various positions of a downstream following wing relative to an upstream vortex-generating wing. Calculated vortex-induced span loads, rolling-moment coefficients, and lift coefficients on the following wing were compared with experimental results of McMillan et al. and El-Ramly et al. Comparisons of calculated and experimental vortex tangential velocities were also made
Short Note: Report of mummified leopard seal carcass in the southern Dry Valleys, McMurdo Sound, Antarctica.
The wide spread occurrence of mummified seal and penguin carcasses tens of kilometres from the open ocean is an interesting phenomenon occurring in the Antarctic Dry Valleys. Mummified seal carcasses were first reported by Scott’s expedition in 1903 (Scott 1969), and live seals and seal carcasses have since been reported many kilometres from the nearest ice-free ocean. Seal carcasses found in the McMurdo Dry Valleys are predominantly crabeater seals (Lobodon carcinophaga (Hombron & Jacquinot)) with a smaller number of Weddell seals, (Leptonychotes weddellii (Lesson)), also reported. Here we present only the second published report of a leopard seal carcass from the McMurdo Dry Valleys
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