Stationary structure of relativistic superfluid neutron stars

We describe recent progress in the numerical study of the structure of rapidly rotating superfluid neutron star models in full general relativity. The superfluid neutron star is described by a model of two interpenetrating and interacting fluids, one representing the superfluid neutrons and the second consisting of the remaining charged particles (protons, electrons, muons). We consider general stationary configurations where the two fluids can have different rotation rates around a common rotation axis. The previously discovered existence of configurations with one fluid in a prolate shape is confirmed.Comment: 5 pages, 2 figures. Conference proceedings for the 26th Spanish Relativity Meeting (ERE 2002), Menorca, Spain, 22-24 Sept. 200

A Relativistic Mean Field Model for Entrainment in General Relativistic Superfluid Neutron Stars

General relativistic superfluid neutron stars have a significantly more intricate dynamics than their ordinary fluid counterparts. Superfluidity allows different superfluid (and superconducting) species of particles to have independent fluid flows, a consequence of which is that the fluid equations of motion contain as many fluid element velocities as superfluid species. Whenever the particles of one superfluid interact with those of another, the momentum of each superfluid will be a linear combination of both superfluid velocities. This leads to the so-called entrainment effect whereby the motion of one superfluid will induce a momentum in the other superfluid. We have constructed a fully relativistic model for entrainment between superfluid neutrons and superconducting protons using a relativistic $\sigma - \omega$ mean field model for the nucleons and their interactions. In this context there are two notions of ``relativistic'': relativistic motion of the individual nucleons with respect to a local region of the star (i.e. a fluid element containing, say, an Avogadro's number of particles), and the motion of fluid elements with respect to the rest of the star. While it is the case that the fluid elements will typically maintain average speeds at a fraction of that of light, the supranuclear densities in the core of a neutron star can make the nucleons themselves have quite high average speeds within each fluid element. The formalism is applied to the problem of slowly-rotating superfluid neutron star configurations, a distinguishing characteristic being that the neutrons can rotate at a rate different from that of the protons.Comment: 16 pages, 5 figures, submitted to PR

"What do you Mean I Cannot Consent For My Grandmother's Medical Procedure?": Key Issues With State Default Surrogate Decision Making Laws

When a patient is unable to make medical decisions, a health care surrogate must be designated to make decisions on the patient's behalf. Studies show that fewer than 20% of patients have completed health care representative forms to legally designate a surrogate. Without a prior designation, surrogates are determined via state statute. Currently, there is no up-to-date comprehensive evaluation of state surrogate legislation. A survey of state legislative codes was conducted to determine: 1) whether the state has a default surrogate statute; 2) who is included as an acceptable legal surrogate; and 3) whether there is a hierarchy to determine a final decision-maker. Currently, 36 states have enacted some form of surrogate statute. There is little consistency between states regarding who may serve as a surrogate decision- maker. The key challenges with state laws include: 1) a narrow list of persons who qualify as allowable legal surrogates; and 2) a lack of a hierarchy to determine a final decision-maker. The results of this survey show that state surrogate decision making laws have many flaws which could affect patient care. The narrow construction of state laws can leave patients in situations where they either have no qualified surrogate under the law, or where they have multiple surrogates with competing interests who may be unable to reach consensus on the patient's medical care. State laws need to be changed so that they accurately reflect the realities of clinical practice and expanded to allow a broader spectrum of potential surrogates

The Virginia SOL Eighth Grade Writing Test in Relationship to the National Commission on Writing Recommendations, Grade Configuration, Region, and Socioeconomic Status.

The purpose of this quantitative study was to examine Virginia Standards of Learning 8th grade writing assessments to determine if there was any association between school passing rates and the recommendations suggested by the 2003 National Commission on Writing to improve writing proficiency. This study further examined the possible differences in school passing rates that may exist due to the grade configuration of a school, the location of a school, the availability of a comprehensive writing plan, and the student percentage on free and reduced-price lunch. Data collection consisted of a self-administered survey sent to all 364 schools in Virginia that administered SOL writing assessments during the 2006-2007 school year./p\u3e This study showed no significant differences in 8th grade writing passing rates between schools with a comprehensive writing plan and those that do not. However, there was a significant difference in 8th grade teacher support for writing, division-administrative support for writing, and the understanding of writing scoring criteria in those schools with a comprehensive plan. There was little association between SOL writing scores and the implementation level of the 7 dimensions related to the National Commission on Writing recommendations. When controlling for socioeconomic status, there was no significant difference in writing scores. The addition of 4 multiple-choice questions to the SOL test two years ago without a change in the cut score necessary for a student to pass appears to have had a larger impact on the passing rates of schools than the variables included in this study

RAM-Efficient External Memory Sorting

In recent years a large number of problems have been considered in external memory models of computation, where the complexity measure is the number of blocks of data that are moved between slow external memory and fast internal memory (also called I/Os). In practice, however, internal memory time often dominates the total running time once I/O-efficiency has been obtained. In this paper we study algorithms for fundamental problems that are simultaneously I/O-efficient and internal memory efficient in the RAM model of computation.Comment: To appear in Proceedings of ISAAC 2013, getting the Best Paper Awar

Behold thy doom is mine: The evolution of Guinevere in the eorks of Chrétien de Troyes, Sir Thomas Malory, and Alfred, Lord Tennyson

Guinevere has existed in literature for nearly a millennium, evolving to suit societal values and mores. She has metamorphosed from Arthur’s noble queen to Lancelot’s jealous lover, from a motherly sovereign to a vindictive adulteress as each author struggled to apply his own literary and societal conventions to a character that is both inherited and created. In addressing the evolution of Guinevere, this thesis has followed her progression through three works: The Knight of the Cart by Chrétien de Troyes, Le Morte d’Arthur by Sir Thomas Malory, and The Idylls of the King by Alfred, Lord Tennyson. In addition, this thesis has drawn upon literary criticism, including that of Maureen Fries and Norris J. Lacy, in proving how Guinevere’s character marks the societal values and beliefs of each author’s time period, as well as how she exemplifies the struggle to understand female characters in literature

Slowly Rotating General Relativistic Superfluid Neutron Stars with Relativistic Entrainment

Neutron stars that are cold enough should have two or more superfluids/supercondutors in their inner crusts and cores. The implication of superfluidity/superconductivity for equilibrium and dynamical neutron star states is that each individual particle species that forms a condensate must have its own, independent number density current and equation of motion that determines that current. An important consequence of the quasiparticle nature of each condensate is the so-called entrainment effect, i.e. the momentum of a condensate is a linear combination of its own current and those of the other condensates. We present here the first fully relativistic modelling of slowly rotating superfluid neutron stars with entrainment that is accurate to the second-order in the rotation rates. The stars consist of superfluid neutrons, superconducting protons, and a highly degenerate, relativistic gas of electrons. We use a relativistic $\sigma$ - $\omega$ mean field model for the equation of state of the matter and the entrainment. We determine the effect of a relative rotation between the neutrons and protons on a star's total mass, shape, and Kepler, mass-shedding limit.Comment: 30 pages, 10 figures, uses ReVTeX

Subdiffusion in Membrane Permeation of Small Molecules

Citation: Chipot, C. and Comer, J. Subdiffusion in Membrane Permeation of Small Molecules. Sci. Rep. 6, 35913; doi: 10.1038/srep35913 (2016).Within the solubility–diffusion model of passive membrane permeation of small molecules, translocation of the permeant across the biological membrane is traditionally assumed to obey the Smoluchowski diffusion equation, which is germane for classical diffusion on an inhomogeneous free-energy and diffusivity landscape. This equation, however, cannot accommodate subdiffusive regimes, which have long been recognized in lipid bilayer dynamics, notably in the lateral diffusion of individual lipids. Through extensive biased and unbiased molecular dynamics simulations, we show that one-dimensional translocation of methanol across a pure lipid membrane remains subdiffusive on timescales approaching typical permeation times. Analysis of permeant motion within the lipid bilayer reveals that, in the absence of a net force, the mean squared displacement depends on time as t0.7, in stark contrast with the conventional model, which assumes a strictly linear dependence. We further show that an alternate model using a fractional-derivative generalization of the Smoluchowski equation provides a rigorous framework for describing the motion of the permeant molecule on the pico- to nanosecond timescale. The observed subdiffusive behavior appears to emerge from a crossover between small-scale rattling of the permeant around its present position in the membrane and larger-scale displacements precipitated by the formation of transient voids