Signature change from Schutz's canonical quantum cosmology and its classical analogue

We study the signature change in a perfect fluid Friedmann-Robertson-Walker quantum cosmological model. In this work the Schutz's variational formalism is applied to recover the notion of time. This gives rise to a Schrodinger-Wheeler-DeWitt equation with arbitrary ordering for the scale factor. We use the eigenfunctions in order to construct wave packets and evaluate the time-dependent expectation value of the scale factor which coincides with the ontological interpretation. We show that these solutions exhibit signature transitions from a finite Euclidean to a Lorentzian domain. Moreover, such models are equivalent to a classical system where, besides the perfect fluid, a repulsive fluid is present.Comment: 15 pages, 4 figures, to appear in PR

Superconductivity and Field-Induced Magnetism in Pr2−x_{2-x}Cex_xCuO4_4 Single Crystals

We report muon-spin rotation/relaxation (muSR) measurements on single crystals of the electron-doped high-T_c superconductor Pr$_{2-x}$Ce$_x$CuO$_4$. In zero external magnetic field, superconductivity is found to coexist with Cu spins that are static on the muSR time scale. In an applied field, we observe a Knight shift that is primarily due to the magnetic moment induced on the Pr ions. Below the superconducting transition temperature T_c, an additional source of static magnetic order appears throughout the sample. This finding is consistent with antiferromagnetic ordering of the Cu spins in the presence of vortices. We also find that the temperature dependence of the in-plane magnetic penetration depth in the vortex state resembles that of the hole-doped cuprates at temperatures above ~ 0.2 T_c.Comment: 4 pages, 5 figure

Seasonal and diurnal variations of atmospheric mercury across the US determined from AMNet monitoring data

Speciated atmospheric mercury observations collected over the period from 2008 to 2010 at the Environmental Protection Agency and National Atmospheric Deposition Program Atmospheric Mercury Network sites (AMNet) were analyzed for its spatial, seasonal, and diurnal characteristics across the US. Median values of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) at 11 different AMNet sites ranged from 148–226 ppqv (1.32–2.02 ng m<sup>−3</sup>), 0.05–1.4 ppqv (0.47–12.4 pg m<sup>−3</sup>) and 0.18–1.5 ppqv (1.61–13.7 pg m<sup>−3</sup>), respectively. Common characteristics of these sites were the similar median levels of GEM as well as its seasonality, with the highest mixing ratios occurring in winter and spring and the lowest in fall. However, discernible differences in monthly average GEM were as large as 30 ppqv, which may be caused by sporadic influence from local emission sources. The largest diurnal variation amplitude of GEM occurred in the summer. Seven rural sites displayed similar GEM summer diurnal patterns, in that the lowest levels appeared in the early morning, and then the GEM mixing ratio increased after sunrise and reached its maxima at noon or in the early afternoon. Unlike GEM, GOM exhibited higher mixing ratios in spring and summer. The largest diurnal variation amplitude of GOM occurred in spring for most AMNet sites. The GOM diurnal minima appeared before sunrise and maxima appeared in the afternoon. The increased GOM mixing ratio in the afternoon indicated a photochemically driven oxidation of GEM resulting in GOM formation. PBM exhibited diurnal fluctuations in summertime. The summertime PBM diurnal pattern displayed daily maxima in the early afternoon and lower mixing ratios at night, implying photochemical production of PBM in summer

Energy Requirements for Quantum Data Compression and 1-1 Coding

By looking at quantum data compression in the second quantisation, we present a new model for the efficient generation and use of variable length codes. In this picture lossless data compression can be seen as the {\em minimum energy} required to faithfully represent or transmit classical information contained within a quantum state. In order to represent information we create quanta in some predefined modes (i.e. frequencies) prepared in one of two possible internal states (the information carrying degrees of freedom). Data compression is now seen as the selective annihilation of these quanta, the energy of whom is effectively dissipated into the environment. As any increase in the energy of the environment is intricately linked to any information loss and is subject to Landauer's erasure principle, we use this principle to distinguish lossless and lossy schemes and to suggest bounds on the efficiency of our lossless compression protocol. In line with the work of Bostr\"{o}m and Felbinger \cite{bostroem}, we also show that when using variable length codes the classical notions of prefix or uniquely decipherable codes are unnecessarily restrictive given the structure of quantum mechanics and that a 1-1 mapping is sufficient. In the absence of this restraint we translate existing classical results on 1-1 coding to the quantum domain to derive a new upper bound on the compression of quantum information. Finally we present a simple quantum circuit to implement our scheme.Comment: 10 pages, 5 figure

Economic rationalisation of health behaviours: the dangers of attempting policy discussions in a vacuum

When analysing the health behaviours of any group of people, understanding the constraints and possibilities for individual agency as shaped by the broader societal context is critical. In recent decades, our understanding of the ways in which physical and social environments influence health and health behaviours has expanded greatly. The authors of a recent analysis of Australian Aboriginal health data using an economic ‘rational choice model,’ published in this journal, claim to make a useful contribution to policy discussions relating to Aboriginal health, but neglect context. By doing so, they neglect the very factors that determine the success or failure of policy change. Notwithstanding the technical sophistication of the analyses, by ignoring most relevant determinants of health, the conclusions misrepresent the lives of Aboriginal and Torres Strait Islander people and therefore risk perpetuating harm, rather than improving health.Rachel Reilly, Kevin Rowley Joanne Luke Joyce Doyle Rebecca Ritte Rebekah O, Shea Alex Brow

DVT Surveillance Program in the ICU: Analysis of Cost-Effectiveness

Background Venous Thrombo-embolism (VTE – Deep venous thrombosis (DVT) and/or pulmonary embolism (PE) – in traumatized patients causes significant morbidity and mortality. The current study evaluates the effectiveness of DVT surveillance in reducing PE, and performs a cost-effectiveness analysis. Methods All traumatized patients admitted to the adult ICU underwent twice weekly DVT surveillance by bilateral lower extremity venous Duplex examination (48-month surveillance period – SP). The rates of DVT and PE were recorded and compared to the rates observed in the 36-month pre-surveillance period (PSP). All patients in both periods received mechanical and pharmacologic prophylaxis unless contraindicated. Total costs – diagnostic, therapeutic and surveillance – for both periods were recorded and the incremental cost for each Quality Adjusted Life Year (QALY) gained was calculated. Results 4234 patients were eligible (PSP – 1422 and SP – 2812). Rate of DVT in SP (2.8%) was significantly higher than in PSP (1.3%) – p Conclusions Surveillance of traumatized ICU patients increases DVT detection and reduces PE incidence. Costs in terms of QALY gained compares favorably with other interventions accepted by society