Comparisons of elastic and creep deformation linearly dependent upon stress

The theory of linear elasticity provides a complete description of reversible deformation under small stresses for both isotropic and anisotropic solids. At elevated temperatures, creep deformation sometimes occurs at a rate that is linearly dependent upon stress. When this form of creep arises from vacancy movement, there is possibility of anisotropic behaviour through the orientational dependence of average grain dimensions. This indicates that the elasticity theory may be utilised to provide comparable descriptions of such creep deformation, with creep strain built up of equal increments of strain occurring in equal intervals of time. The extent of this analogy is explored with the conclusion that its usefulness is substantial when grains are small in relation to geometrical features of the component but it is no longer applicable when the grains approach the size of these features and where there is a high gradient of stress

The relationship between CK and CV chondrites: a single parent body source?

The relationship between CK and CV3 chondrites is examined. Both groups may represent a single continuum and have been derived from the same parent body

Optical and dc transport properties of a strongly correlated charge density wave system: exact solution in the ordered phase of the spinless Falicov-Kimball model with dynamical mean-field theory

We derive the dynamical mean-field theory equations for transport in an ordered charge-density-wave phase on a bipartite lattice. The formalism is applied to the spinless Falicov-Kimball model on a hypercubic lattice at half filling. We determine the many-body density of states, the dc charge and heat conductivities, and the optical conductivity. Vertex corrections continue to vanish within the ordered phase, but the density of states and the transport coefficients show anomalous behavior due to the rapid development of thermally activated subgap states. We also examine the optical sum rule and sum rules for the first three moments of the Green's functions within the ordered phase and see that the total optical spectral weight in the ordered phase either decreases or increases depending on the strength of the interactions.Comment: 14 pages, 14 figures, submitted to Phys. Rev.

Voting Rights Federalism

It’s well-known that the federal Voting Rights Act is reeling. The Supreme Court nullified one of its two central provisions in 2013. The Court has also repeatedly weakened the bite of the statute’s other key section. Less familiar, though, is the recent rise of state voting rights acts (SVRAs): state-level enactments that provide more protection against racial discrimination in voting than does federal law. Eight states have passed SVRAs so far—five since 2018. Several more states are currently drafting SVRAs. Yet even though these measures are the most promising development in the voting rights field in decades, they have attracted little scholarly attention. They have been the subject of only a handful of political science studies and no sustained legal analysis at all. In this Article, then, we provide the first descriptive, constitutional, and policy assessment of SVRAs. We first taxonomize SVRAs. That is, we catalogue how they diverge from, and build on, federal protections against racial vote denial, racial vote dilution, and retrogression. Second, we show that SVRAs are constitutional in that they don’t violate any branch of equal protection doctrine. They don’t constitute (or compel) racial gerrymandering, nor do they classify individuals on the basis of race, nor are they motivated by invidious racial purposes. Finally, while existing SVRAs are quite potent, we present an array of proposals that would make them even sharper swords against racial discrimination in voting. One suggestion is for SVRAs simply to mandate that localities switch to less discriminatory electoral laws—not to rely on costly, time-consuming, piecemeal litigation. Another idea is for SVRAs to allow each plaintiff to specify the benchmark relative to which racial vote dilution should be measured—not to stay mute on the critical issue of baselines

Development of a Radioimmunoassay for Pig Pancreatic Kallikrein

Peer Reviewe

Northwest Africa 5790. Top Sequence of the Nakhlite Pile

NWA 5790 is a recently discovered nakhlite. Its mineralogy, petrology and geochemistry suggest that it is the topmost sequence of the nakhlite lava pile

Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier

Ice shelves are critical features in the debate about West Antarctic ice sheet change and sea level rise, both because they limit ice discharge and because they are sensitive to change in the surrounding ocean. The Pine Island Glacier ice shelf has been thinning rapidly since at least the early 1990s, which has caused its trunk to accelerate and retreat. Although the ice shelf front has remained stable for the past six decades, past periods of ice shelf collapse have been inferred from relict seabed "corrugations" (corrugated ridges), preserved 340 km from the glacier in Pine Island Trough. Here we present high-resolution bathymetry gathered by an autonomous underwater vehicle operating beneath an Antarctic ice shelf, which provides evidence of long-term change in Pine Island Glacier. Corrugations and ploughmarks on a sub-ice shelf ridge that was a former grounding line closely resemble those observed offshore, interpreted previously as the result of iceberg grounding. The same interpretation here would indicate a significantly reduced ice shelf extent within the last 11 kyr, implying Holocene glacier retreat beyond present limits, or a past tidewater glacier regime different from today. The alternative, that corrugations were not formed in open water, would question ice shelf collapse events interpreted from the geological record, revealing detail of another bed-shaping process occurring at glacier margins. We assess hypotheses for corrugation formation and suggest periodic grounding of ice shelf keels during glacier unpinning as a viable origin. This interpretation requires neither loss of the ice shelf nor glacier retreat and is consistent with a "stable" grounding-line configuration throughout the Holocene

Circuit enhances vertical resolution in raster scanning systems

Circuit enhances vertical resolution in electron beam, raster scanning systems exhibiting aperture distortion in the vertical direction. A sensitized area /image/ produces a video output when the scan beam nears it, which causes vertical elongation in the reconstructed images of all sensitized areas on the surface

Using in situ management to conserve biodiversity under climate change

This is the final version of the article. Available from Wiley via the DOI in this record.The accepted author manuscript version of this article is in ORE at http://hdl.handle.net/10871/18829Successful conservation will increasingly depend on our ability to help species cope with climate change. While there has been much attention on accommodating or assisting range shifts, less has been given to the alternative strategy of helping species survive climate change through in situ management.Here we provide a synthesis of published evidence examining whether habitat management can be used to offset the adverse impacts on biodiversity of changes in temperature, water availability and sea-level rise. Our focus is on practical methods whereby the local environmental conditions experienced by organisms can be made more suitable.Many studies suggest that manipulating vegetation structure can alter the temperature and moisture conditions experienced by organisms, and several demonstrate that these altered conditions benefit species as regional climatic conditions become unsuitable. The effects of topography on local climatic conditions are even better understood, but the alteration of topography as a climate adaptation tool is not ingrained in conservation practice. Trials of topographic alteration in the field should therefore be a priority for future research.Coastal systems have the natural capacity to keep pace with climate change, but require sufficient sediment supplies and space for landward migration to do so. There is an extensive literature on managed realignment. While the underlying rationale is simple, successful implementation requires careful consideration of elevation and past land use. Even with careful management, restored habitats may not attain the physical and biological attributes of natural habitats. Synthesis and applications. The recent literature provides a compelling case that some of the adverse effects of climate change can be offset by appropriate management. However, much of the evidence for this is indirect and too few studies provide empirical tests of the long-term effectiveness of these management interventions. It is clear from the existing evidence that some techniques have a higher risk of failure or unexpected outcomes than others and managers will need to make careful choices about which to implement. We have assessed the strength of evidence of these approaches in order to demonstrate to conservation professionals the risks involved.A.J.S. was funded by a NERC grant, ref: NE/L00268X/1