Double symmetry breaking and 2D quantum phase diagram in spin-boson systems

The quantum ground state properties of two independent chains of spins (two-levels systems) interacting with the same bosonic field are theoretically investigated. Each chain is coupled to a different quadrature of the field, leading to two independent symmetry breakings for increasing values of the two spin-boson interaction constants $\Omega_C$ and $\Omega_I$. A phase diagram is provided in the plane ($\Omega_C$,$\Omega_I$) with 4 different phases that can be characterized by the complex bosonic coherence of the ground states and can be manipulated via non-abelian Berry effects. In particular, when $\Omega_C$ and $\Omega_I$ are both larger than two critical values, the fundamental subspace has a four-fold degeneracy. Possible implementations in superconducting or atomic systems are discussed

A Spectro-photometric Analysis of Cool White Dwarfs in the Gaia and Pan-STARRS Footprint

We present a spectro-photometric analysis of 2880 cool white dwarfs within 100 pc of the Sun and cooler than Teff = 10,000 K, with grizy Pan-STARRS photometry and Gaia trigonometric parallaxes available. We also supplement our data sets with near-infrared JHK photometry, when available, which is shown to be essential for interpreting the coolest white dwarfs in our sample. We perform a detailed analysis of each individual object using state-of-the-art model atmospheres appropriate for each spectral type including DA, DC, DQ, DZ, He-rich DA, and the so-called IR-faint white dwarfs. We discuss the temperature and mass distributions of each subsample, as well as revisit the spectral evolution of cool white dwarfs. We find little evidence in our sample for the transformation of a significant fraction of DA stars into He-atmosphere white dwarfs through the process of convective mixing between Teff = 10,000 K and 6500 K, although the situation changes drastically in the range Teff = 6500 - 5500 K where the fraction of He-atmosphere white dwarfs reaches 45%. However, we also provide strong evidence that at even cooler temperatures (Teff < 5200 K), most DC white dwarfs have H atmospheres. We discuss a possible mechanism to account for this sudden transformation from He- to H-atmosphere white dwarfs involving the onset of crystallization and the occurrence of magnetism. Finally, we also argue that DQ, DZ, and DC white dwarfs may form a more homogeneous population than previously believed.Comment: Accepted for publication in MNRAS (21 pages, 20 figures

A Search for Dense Molecular Gas in High Redshift Infrared-Luminous Galaxies

We present a search for HCN emission from four high redshift far infrared (IR) luminous galaxies. Current data and models suggest that these high $z$ IR luminous galaxies represent a major starburst phase in the formation of spheroidal galaxies, although many of the sources also host luminous active galactic nuclei (AGN), such that a contribution to the dust heating by the AGN cannot be precluded. HCN emission is a star formation indicator, tracing dense molecular hydrogen gas within star-forming molecular clouds (n(H$_2$) $\sim 10^5$ cm$^{-3}$). HCN luminosity is linearly correlated with IR luminosity for low redshift galaxies, unlike CO emission which can also trace gas at much lower density. We report a marginal detection of HCN (1-0) emission from the $z=2.5832$ QSO J1409+5628, with a velocity integrated line luminosity of $L_{\rm HCN}'=6.7\pm2.2 \times10^{9}$ K km s$^{-1}$ pc$^2$, while we obtain 3$\sigma$ upper limits to the HCN luminosity of the $z=3.200$ QSO J0751+2716 of $L_{\rm HCN}'=1.0\times10^{9}$ K km s$^{-1}$ pc$^2$, $L_{\rm HCN}'=1.6\times10^{9}$ K km s$^{-1}$ pc$^2$ for the $z= 2.565$ starburst galaxy J1401+0252, and $L_{\rm HCN}'=1.0\times10^{10}$ K km s$^{-1}$ pc$^2$ for the $z = 6.42$ QSO J1148+5251. We compare the HCN data on these sources, plus three other high-$z$ IR luminous galaxies, to observations of lower redshift star-forming galaxies. The values of the HCN/far-IR luminosity ratios (or limits) for all the high $z$ sources are within the scatter of the relationship between HCN and far-IR emission for low $z$ star-forming galaxies (truncated).Comment: aastex format, 4 figures. to appear in the Astrophysical Journal; Revised lens magnification estimate for 1401+025

Cross-cultural adaptation and validation of the self-reporting questionnaire among HIV+ individuals in a rural ART program in southern Uganda

Background: HIV treatment programs are in need of brief, valid instruments to identify common mental disorders such as depression. Aim: To translate and culturally adapt the Self-Reporting Questionnaire (SRQ-20) for use in Uganda and to investigate its psychometric properties in this setting. Methods: Following an initial translation of the SRQ-20 from English to Luganda, key informant interviews and focus-group discussions were used to produce a culturally adapted version of the instrument. The adapted SRQ-20 was administered to 200 HIV-positive individuals in a rural antiretroviral therapy program in southern Uganda. All study participants were also evaluated by a psychiatric clinical officer with the Mini International Neuropsychiatric Interview (MINI). Receiver-operating-characteristic analysis was used to examine the sensitivity and specificity of the SRQ-20 compared to the clinical diagnosis generated by the MINI. Results: The prevalence estimates of any depressive disorder and current depression were 24% (n = 48) and 12% (n = 24), respectively. The SRQ-20 scores discriminated well between subjects with and without current depression based on the MINI, with an area under the curve of 0.92, as well as between subjects with and without any current or past depressive disorder, with an area under the curve of 0.75. A score of 6 or more had 84% sensitivity and 93% specificity for current depression, and 75% sensitivity and 90% specificity for any depressive disorder. Conclusion: The SRQ-20 appears to be a reliable and valid screening measure for depression among rural HIV-positive individuals in southern Uganda. The use of this screening instrument can potentially improve detection and management of depression in this setting. © 2012 Nakimuli-Mpungu et al, publisher and licensee Dove Medical Press Ltd

The UV filtering potential of drop-casted layers of frustules of three diatom species

Abstract Diatoms are in focus as biological materials for a range of photonic applications. Many of these applications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms frustules (silica walls) have been carried out on single cells. In this study, for the first time, we test the spectral properties of layers of frustules of three diatom species (Coscinodiscus granii, Thalassiosira punctifera and Thalassiosira pseudonana), with special focus on transmission and reflectance in the UV range. The transmittance efficiency in the UV A and B range was: T. pseudonana (56–59%) >C. granii (53–54%) >T. punctifera (18–21%) for the rinsed frustules. To investigate the underlying cause of these differences, we performed X-ray scattering analysis, measurement of layer thickness and microscopic determination of frustule nanostructures. We further tested dried intact cells in the same experimental setup. Based on these data we discuss the relative importance of crystal structure properties, nanostructure and quantity of material on the spectral properties of diatom layers. Characterization of the UV protection performance of layers of diatom frustules is of central relevance for their potential use as innovative bio-based UV filters

Existential witness extraction in classical realizability and via a negative translation

We show how to extract existential witnesses from classical proofs using Krivine's classical realizability---where classical proofs are interpreted as lambda-terms with the call/cc control operator. We first recall the basic framework of classical realizability (in classical second-order arithmetic) and show how to extend it with primitive numerals for faster computations. Then we show how to perform witness extraction in this framework, by discussing several techniques depending on the shape of the existential formula. In particular, we show that in the Sigma01-case, Krivine's witness extraction method reduces to Friedman's through a well-suited negative translation to intuitionistic second-order arithmetic. Finally we discuss the advantages of using call/cc rather than a negative translation, especially from the point of view of an implementation.Comment: 52 pages. Accepted in Logical Methods for Computer Science (LMCS), 201

Appeal No. 0678: Perto Drilling Corp., Inc. v. Division of Mineral Resources Management

Chief\u27s Order 99-15

The XMM-LSS survey. Survey design and first results

We have designed a medium deep large area X-ray survey with XMM - the XMM Large Scale Structure survey, XMM-LSS - with the scope of extending the cosmological tests attempted using ROSAT cluster samples to two redshift bins between 0<z<1 while maintaining the precision of earlier studies. Two main goals have constrained the survey design: the evolutionary study of the cluster-cluster correlation function and of the cluster number density. The results are promising and, so far, in accordance with our predictions as to the survey sensitivity and cluster number density. The feasibility of the programme is demonstrated and further X-ray coverage is awaited in order to proceed with a truly significant statistical analysis. (Abridged)Comment: Published in Journal of Cosmology and Astroparticle Physic