The Origin of Persistent Shear Stress in Supercooled Liquids

We show that the long time tail of the shear stress autocorrelation, whose growth at large supercooling is responsible for the apparent divergence of the shear viscosity, is a direct result of a residual shear stress in the structures associated with the local potential minima. We argue that the essential mechanical transition experienced by a liquid on cooling occurs at a temperature well above the glass transition temperature and corresponds to the crossover from the high temperature liquid to the viscous liquid, the latter characterised by stress relaxation dominated by the residual stress. Following on from this observation, as the density is decreased, the local potential minima become unable to sustain any persistent stress (and, hence, support a glass transition), in a manner that can be explicitly connected to the interactions between atoms. The reported crossover implies an associated change in the mechanism of dissipation in liquids and, hence, raises the prospect of a coherent microscopic treatment of nonlinear rheology and the relationship between self diffusion and viscosity in supercooled liquids

The Hospital Costs of Firearm Assaults

In the wake of recent high profile incidents of gun violence, there is renewed national attention on the prevalence and cost of firearm assaults in the United States. To make informed policy decisions, lawmakers are calling for current and accurate data on the costs of these assaults. This brief examines the costs of emergency department (ED) visits and hospital admissions for firearm assault victims in the United States in 2010. These costs are further examined according to patient gender, age, median household income, and insurance status

Extending the Coinvariant Theorems of Chevalley, Shephard--Todd, Mitchell and Springer

We extend in several directions invariant theory results of Chevalley, Shephard and Todd, Mitchell and Springer. Their results compare the group algebra for a finite reflection group with its coinvariant algebra, and compare a group representation with its module of relative coinvariants. Our extensions apply to arbitrary finite groups in any characteristic.Comment: The applications and Examples in section 4 have been extende

Rectification of laser-induced electronic transport through molecules

We study the influence of laser radiation on the electron transport through a molecular wire weakly coupled to two leads. In the absence of a generalized parity symmetry, the molecule rectifies the laser induced current, resulting in directed electron transport without any applied voltage. We consider two generic ways of dynamical symmetry breaking: mixing of different harmonics of the laser field and molecules consisting of asymmetric groups. For the evaluation of the nonlinear current, a numerically efficient formalism is derived which is based upon the Floquet solutions of the driven molecule. This permits a treatment in the non-adiabatic regime and beyond linear response.Comment: 12 pages, 10 figures, REVTeX

Self-forces in arbitrary dimensions

Bodies coupled to electromagnetic or other long-range fields are subject to radiation reaction and other effects in which their own fields can influence their motion. Self-force phenomena such as these have been poorly understood for spacetime dimensions not equal to four, despite the relevance of differing dimensionalities for holographic duals, effectively two-dimensional condensed matter and fluid systems, and so on. We remedy this by showing that forces and torques acting on extended electromagnetic charges in all dimensions $d \geq 3$ have the same functional form as the usual test body expressions, except that the electromagnetic field appearing in those expressions is not the physical one; it is an effective surrogate. For arbitrary even $d \geq 4$, our surrogate field locally satisfies the source-free field equations, and is conceptually very similar to what arises in the Detweiler-Whiting prescription previously established when $d=4$. The odd-dimensional case is different, involving effective fields which are not necessarily source-free. Moreover, we find a 1-parameter family of natural effective fields for each odd $d$, where the free parameter--a lengthscale--is degenerate with (finite) renormalizations of a body's stress-energy tensor. While different parameter choices can result in different forces, they do so without affecting physical observables. Having established these general results, explicit point-particle self-forces are derived in odd-dimensional Minkowski spacetimes. Simple examples are discussed for $d=3$ and $d=5$, one of which illustrates that the particularly slow decay of fields in three spacetime dimensions results in particles creating their own "preferred rest frames:" Initially-static charges which are later perturbed have a strong tendency to return to rest. Our results easily extend also to the scalar and gravitational self-force problems.Comment: 6 page

'For a decent order in the Church' : ceremony, culture and conformity in an early Stuart diocese, with particular reference to the See of Westminster

The title of this thesis is taken from the Book of Common Prayer, specifically from the section 'Of Ceremonies: Why some be Abolished and some Retained'. It takes as its premise the theory that arguments over the way in which worship was conducted were more important than doctrinal matters in the religious tensions which arose before the Civil War, focussing attention upon the diocese of Winchester. The thesis is split into three broad sections. The first section deals with the ceremonies of the church, and is split into two chapters. The first of these chapters is based largely around the physical structure of a church, whilst the second is more concerned with the rites and rubrics as laid down in the Book of Common Prayer.The second section, in three chapters, focusses upon the use of the arts in the early Stuart church. The first of these chapters concentrates on the visual arts, and the way in which they were used, particularly with regard to their hierarchical arrangement. The second turns attention to the aural arts, examining the differences, and similarities, in approach taken at the time. The third examines the idea that there was a specific culture which can be associated with Puritanism. The final section focusses upon the defence of hierarchy within the church. The first chapter in this section examines defences of Episcopal government which were produced by clerics who worked in the diocese. The second chapter looks at attempts to induce greater conformity within the diocese, and places this in the context of national events

A Model Connecting Galaxy Masses, Star Formation Rates, and Dust Temperatures Across Cosmic Time

We investigate the evolution of dust content in galaxies from redshifts z=0 to z=9.5. Using empirically motivated prescriptions, we model galactic-scale properties -- including halo mass, stellar mass, star formation rate, gas mass, and metallicity -- to make predictions for the galactic evolution of dust mass and dust temperature in main sequence galaxies. Our simple analytic model, which predicts that galaxies in the early Universe had greater quantities of dust than their low-redshift counterparts, does a good job at reproducing observed trends between galaxy dust and stellar mass out to z~6. We find that for fixed galaxy stellar mass, the dust temperature increases from z=0 to z=6. Our model forecasts a population of low-mass, high-redshift galaxies with interstellar dust as hot as, or hotter than, their more massive counterparts; but this prediction needs to be constrained by observations. Finally, we make predictions for observing 1.1-mm flux density arising from interstellar dust emission with the Atacama Large Millimeter Array.Comment: Accepted for publication in Ap

Resolving Gamma-Ray Burst 000301C with a Gravitational Microlens

The afterglow of the Gamma-Ray Burst (GRB) 000301C exhibited achromatic, short time-scale variability that is difficult to reconcile with the standard relativistic shock model. We interpret the observed light curves as a microlensing event superimposed on power-law flux decays typical of afterglows. In general, a relativistic GRB shock appears on the sky as a thin ring expanding at a superluminal speed. Initially the ring is small relative to its angular separation from the lens and so its flux is magnified by a constant factor. As the ring grows and sweeps across the lens its magnification reaches a maximum. Subsequently, the flux gradually recovers its unlensed value. This behavior involves only three free parameters in its simplest formulation and was predicted theoretically by Loeb & Perna (1998). Fitting the available R-band photometric data of GRB 000301C to a simple model of the microlensing event and a broken power-law for the afterglow, we find reasonable values for all the parameters and a reduced chi^2/DOF parameter of 1.48 compared with 2.99 for the broken power-law fit alone. The peak magnification of ~2 occurred 3.8 days after the burst. The entire optical-IR data imply a width of the GRB ring of order 10% of its radius, similar to theoretical expectations. The angular resolution provided by microlensing is better than a micro-arcsecond. We infer a mass of approximately 0.5 M_Sun for a lens located half way to the source at z_s=2.04. A galaxy 2'' from GRB 000301C might be the host of the stellar lens, but current data provides only an upper-limit on its surface brightness at the GRB position.Comment: to appear in the ApJ Letters, 13 pages, 3 figures (one additional figure included); all data used for the fits available at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB000301C/ and through WWW at http://cfa-www.harvard.edu/cfa/oir/Research/GRB