Constraints on Neutron Star Crusts From Oscillations in Giant Flares

We show that the fundamental seismic shear mode, observed as a quasi-periodic oscillation in giant flares emitted by highly-magnetized neutron stars, is particularly sensitive to the nuclear physics of the crust. The identification of an oscillation at ~ 30 Hz as the fundamental crustal shear mode requires a nuclear symmetry energy that depends very weakly on density near saturation. If the nuclear symmetry energy varies more strongly with density, then lower frequency oscillations, previously identified as torsional Alfven modes of the fluid core, could instead be associated with the crust. If this is the case, then future observations of giant flares should detect oscillations at around 18 Hz. An accurate measurement of the neutron skin thickness of lead will also constrain the frequencies predicted by the model.Comment: 5 pages, 3 figures; Version to appear in Phys. Rev. Let

The Practical Theology of the General Rules

The “General Rules of the United Societies” were a central component of the early Methodist movement under John Wesley’s leadership. Examinations of the General Rules in contemporary literature tend to focus on their role in personal and organizational discipline for early Methodists and for the movement as a whole. Yet a close examination of the rules shows that they served a greater purpose: as the practical theological articulation of how Methodists could expect to experience sanctification in the context of their lives. This crucial aspect of the General Rules’ use can be seen by exploring Wesley’s understanding of the means of grace and how the rules were intended as a framework for the means of grace in Methodist discipleship

Overview of Constitutional Challenges to NSA Collection Activities and Recent Developments

[Excerpt] Beginning in the summer of 2013, media reports of foreign intelligence activities conducted by the National Security Agency (NSA) have been published and are apparently based on unauthorized disclosures of classified information by Edward Snowden, a former NSA contractor. The reports have focused on two main NSA collection activities conducted under the auspices of the Foreign Intelligence Surveillance Act (FISA) of 1978. The first is the bulk collection of telephony metadata for domestic and international telephone calls. The second involves the interception of Internet-based communications and is targeted at foreigners who are not within the United States, but may also inadvertently acquire the communications of U.S. persons. As the public’s awareness of these programs has grown, Members of Congress and the public have increasingly voiced concerns about the constitutionality of these programs. This report provides a description of these two programs and the various constitutional challenges that have arisen in judicial forums with respect to each. Although a brief overview of the constitutional arguments and issues raised in the assorted cases is included, a detailed analysis or evaluation of those arguments is beyond the scope of this report

Marine ice-sheet profiles and stability under Coulomb basal conditions

The behavior of marine-terminating ice sheets, such as the West Antarctic ice sheet, is of interest due to the possibility of rapid grounding-line retreat and consequent catastrophic loss of ice. Critical to modeling this behavior is a choice of basal rheology, where the most popular approach is to relate the ice-sheet velocity to a power-law function of basal stress. Recent experiments, however, suggest that near-grounding line tills exhibit Coulomb friction behavior. Here we address how Coulomb conditions modify ice-sheet profiles and stability criteria. The basal rheology necessarily transitions to Coulomb friction near the grounding line, due to low effective stresses, leading to changes in ice-sheet properties within a narrow boundary layer. Ice-sheet profiles ‘taper off’ towards a flatter upper surface, compared with the power-law case, and basal stresses vanish at the grounding line, consistent with observations. In the Coulomb case, the grounding-line ice flux also depends more strongly on flotation ice thickness, which implies that ice sheets are more sensitive to climate perturbations. Furthermore, with Coulomb friction, the ice sheet grounds stably in shallower water than with a power-law rheology. This implies that smaller perturbations are required to push the grounding line into regions of negative bed slope, where it would become unstable. These results have important implications for ice-sheet stability in a warming climate

Ion-mediated conformational switches

Molecular switches are ubiquitous in Nature and provide the basis of many forms of transport and signalling. Single synthetic molecules that change conformation, and thus function, reversibly in a stimulus-dependent manner are of great interest not only to chemists but society in general; myriad applications exist in storage, display, sensing and medicine. Here we describe recent developments in the area of ion-mediated switching