Adiabatic-connection fluctuation-dissipation DFT for the structural properties of solids-the renormalized ALDA and electron gas kernels

We present calculations of the correlation energies of crystalline solids and isolated systems within the adiabatic-connection fluctuation-dissipation formulation of density-functional theory. We perform a quantitative comparison of a set of model exchange-correlation kernels originally derived for the homogeneous electron gas (HEG), including the recently-introduced renormalized adiabatic local-density approximation (rALDA) and also kernels which (a) satisfy known exact limits of the HEG, (b) carry a frequency dependence or (c) display a 1/$k^2$ divergence for small wavevectors. After generalizing the kernels to inhomogeneous systems through a reciprocal-space averaging procedure, we calculate the lattice constants and bulk moduli of a test set of 10 solids consisting of tetrahedrally-bonded semiconductors (C, Si, SiC), ionic compounds (MgO, LiCl, LiF) and metals (Al, Na, Cu, Pd). We also consider the atomization energy of the H$_2$ molecule. We compare the results calculated with different kernels to those obtained from the random-phase approximation (RPA) and to experimental measurements. We demonstrate that the model kernels correct the RPA's tendency to overestimate the magnitude of the correlation energy whilst maintaining a high-accuracy description of structural properties.Comment: 41 pages, 7 figure

Simple vertex correction improves GW band energies of bulk and two-dimensional crystals

The GW self-energy method has long been recognized as the gold standard for quasiparticle (QP) calculations of solids in spite of the fact that the neglect of vertex corrections and the use of a DFT starting point lacks rigorous justification. In this work we remedy this situation by including a simple vertex correction that is consistent with an LDA starting point. We analyse the effect of the self-energy by splitting it into a short-range and long-range term which are shown to govern respectively the center and size of the band gap. The vertex mainly improves the short-range correlations and therefore has a small effect on the band gap, while it shifts the band gap center up in energy by around 0.5 eV in good agreement with experiments. Our analysis also explains how the relative importance of short- and long-range interactions in structures of different dimensionality is reflected in their QP energies. Inclusion of the vertex comes at practically no extra computational cost and even improves the basis set convergence compared to GW. The method thus provides an efficient and rigorous improvement over the GW approximation and sets a new standard for quasiparticle calculations of solids

Hubbard U-corrected Hamiltonians for non-self-consistent random-phase approximation total energy calculations : a study of ZnS, TiO2, and NiO

In non-self-consistent calculations of the total energy within the random-phase approximation (RPA) for electronic correlation, it is necessary to choose a single-particle Hamiltonian whose solutions are used to construct the electronic density and noninteracting response function. Here we investigate the effect of including a Hubbard-U term in this single-particle Hamiltonian, to better describe the on-site correlation of 3d electrons in the transition metal compounds ZnS, TiO2, and NiO. We find that the RPA lattice constants are essentially independent of U, despite large changes in the underlying electronic structure. We further demonstrate that the non-self-consistent RPA total energies of these materials have minima at nonzero U. Our RPA calculations find the rutile phase of TiO2 to be more stable than anatase independent of U, a result which is consistent with experiments and qualitatively different from that found from calculations employing U-corrected (semi)local functionals. However we also find that the +U term cannot be used to correct the RPA's poor description of the heat of formation of NiO

Living with chronic obstructive pulmonary disease and being followed uip through telemedicine - a phenomenological approach

Chronic obstructive pulmonary disease (COPD) provides substantially reduced health related quality of life (HQoL). Telemonitoring on COPD patients appears to have a positive effect on improving HQoL. This study has a phenomenological approach, and ten informants, who were followed-up between 1 and 3 months in their own homes through telemonitoring of COPD symptoms, narrated their lived experiences of HQoL. The results show that the informants experienced safety and increased knowledge through the digital dialog (telemedicine) with expertise nurses, which indirectly improved their HQoL, and in term lead to increased mastery and control in managing their disease. Several studies show an increased HQoL, but the benefits are still limited and there is a need for further research

Unlocking the limitations: living with chronic obstructive pulmonary disease and receiving care through telemedicine - a phenomenological study

Aims and objectives To describe the lived experiences of quality of life among a group of patients living with chronic obstructive pulmonary disease who were included in a telemedical intervention after hospitalisation for disease exacerbation. Background Patients with chronic obstructive pulmonary disease have high symptom burden, poor control of symptoms and a need for greater requirements in care. Telemedicine can provide benefits for patients with chronic obstructive pulmonary disease by improving self-management. Design Descriptive phenomenological approach. Methods Ten in-depth interviews were conducted with chronic obstructive pulmonary disease patients participating in a telemedical intervention. The collected data were analysed using a descriptive phenomenological research method. Results Living with chronic obstructive pulmonary disease was experienced as creating physical and mental limitations of the diseased body and an increasing identity as a patient, which led to impaired quality of life. Being included in the telemedicine intervention increased accessibility to healthcare services and support from telemedicine nurses. Self-measurement of health data increased participants’ clinical insight and created a mutual clinical language in dialogue with telemedicine nurses, which led to increased quality of life. However, receiving care through telemedicine was also experienced as a dual chore. Conclusions Telemedicine can reduce the perceived limitations imposed by chronic obstructive pulmonary disease through four key elements: (i) improving accessibility to healthcare services, (ii) increasing support from health professionals, (iii) strengthening clinical insight and (iv) developing a mutual clinical language, thus increasing quality of life. The transparency facilitated through telemedicine in this healthcare context encourages open decision-making, where the participants can increase their knowledge and improve acknowledgement of and collaboration with telemedicine nurses. Relevance to clinical practice Telemedicine can be beneficial when rethinking care for chronic obstructive pulmonary disease by providing knowledge on how living with chronic obstructive pulmonary disease can affect the experience of receiving care through telemedicine and further determine for whom telemedicine is useful.måsjekke

Triangulum II: Not Especially Dense After All

Among the Milky Way satellites discovered in the past three years, Triangulum II has presented the most difficulty in revealing its dynamical status. Kirby et al. (2015a) identified it as the most dark matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of 3600 +3500 -2100 M_sun/L_sun. On the other hand, Martin et al. (2016) measured an outer velocity dispersion that is 3.5 +/- 2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in Triangulum II, we constrain the velocity dispersion to be sigma_v < 3.4 km/s (90% C.L.). Our previous measurement of sigma_v, based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that Triangulum II retained supernova ejecta and therefore possesses or once possessed a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metal-rich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that Triangulum II is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.Comment: accepted to ApJ, Table 5 available as a machine-readable table by clicking on "Other formats" on the right. Proof corrections reflected in version

Important challenges for coordination and inter-municipal cooperation in health care services: A Delphi study

Background: Demographical changes have stimulated a coordination reform in the Norwegian health care sector, creating new working practices and extending coordination within and between primary and hospital care, increasing the need for inter-municipal cooperation (IMC). This study aimed to identify challenges to coordination and IMC in the Norwegian health care sector as a basis for further theorizing and managerial advice in this growing area of research and practice. Methods: A Delphi study of consensus development was used. Experts in coordination and IMC in health care services were selected by the healthcare manager or the councillor in their respective municipalities. In the first round, an expert panel received open-ended questions addressing possible challenges, and their answers were categorized and consolidated as the basis for further validation in the second round. The expert panel members were then asked to point out important statements in the third round, before the most important statements ranked by a majority of the members were rated again in the fourth round, including the option to explain the ratings. The same procedure was used in round five, with the exception that the expert panel members could view the consolidated results of their previous rankings as the basis for a new and final rating. The statements reaching consensus in round five were abstracted and themed. Results: Nineteen experts consented to participate. Nine experts (47%) completed all of the five rounds. Eight statements concerning coordination reached consensus, resulting in four themes covering these challenges: different culture, uneven balance of power, lack of the possibility to communicate electronically, and demanding tasks in relation to resources. Three statements regarding challenges to IMC reached consensus, resulting in following themes: coopetition, complex leadership, and resistance to change. Conclusions: This study identified several important challenges for coordination and it supports previous research. IMC in health care services deals with challenges other than coordination, and these must be addressed specifically. Our study contributes to extended knowledge of theoretical and practical implications in the field of coordination and IMC in health care sector

The [Y/Mg] clock works for evolved solar metallicity stars

Previously [Y/Mg] has been proven to be an age indicator for solar twins. Here, we investigate if this relation also holds for helium-core-burning stars of solar metallicity. High resolution and high signal-to-noise ratio (S/N) spectroscopic data of stars in the helium-core-burning phase have been obtained with the FIES spectrograph on the NOT 2.56m telescope and the HIRES spectrograph on the Keck I 10 m telescope. They have been analyzed to determine the chemical abundances of four open clusters with close to solar metallicity; NGC 6811, NGC 6819, M67 and NGC 188. The abundances are derived from equivalent widths of spectral lines using ATLAS9 model atmospheres with parameters determined from the excitation and ionization balance of Fe lines. Results from asteroseismology and binary studies were used as priors on the atmospheric parameters, where especially the $\log g$ is determined to much higher precision than what is possible with spectroscopy. It is confirmed that the four open clusters are close to solar metallicity and they follow the [Y/Mg] vs. age trend previously found for solar twins. The [Y/Mg] vs. age clock also works for giant stars in the helium-core burning phase, which vastly increases the possibilities to estimate the age of stars not only in the solar neighborhood, but in large parts of the Galaxy, due to the brighter nature of evolved stars compared to dwarfs.Comment: 5 pages, 3 figures, accepted for publication as a Letter to A&

Inelastic Scattering in Metal-H2-Metal Junctions

We present first-principles calculations of the dI/dV characteristics of an H2 molecule sandwiched between Au and Pt electrodes in the presence of electron-phonon interactions. The conductance is found to decrease by a few percentage at threshold voltages corresponding to the excitation energy of longitudinal vibrations of the H2 molecule. In the case of Pt electrodes, the transverse vibrations can mediate transport through otherwise non-transmitting Pt $d$-channels leading to an increase in the differential conductance even though the hydrogen junction is characterized predominately by a single almost fully open transport channel. In the case of Au, the transverse modes do not affect the dI/dV because the Au d-states are too far below the Fermi level. A simple explanation of the first-principles results is given using scattering theory. Finally, we compare and discuss our results in relation to experimental data.Comment: Accepted in Phys. Rev.

Potential exposure to endocrine disrupting chemicals and selected adverse pregnancy outcomes:a follow-up study of pregnant women referred for occupational counselling

BACKGROUND: Experimental evidence indicates that fetal exposure to xenobiotics with the potential to interfere with the endogenous steroid hormone regulation of fetal development may reduce birth weight. However, epidemiological studies are limited. The aim of the study was to investigate whether potential occupational exposure to endocrine disrupting chemicals (EDC) of the mother during pregnancy is associated with preterm birth and low birth weight. METHODS: Pregnant women referred to an Occupational Health Clinic (OHC) in two Danish regions (Copenhagen or Aarhus) between 1984 and 2010, suspected of being exposed to occupational reproductive hazards were included in the study. A job exposure matrix enabled estimation of potential occupational exposure to EDC on the basis of job title. Births by women potentially exposed to EDC (n = 582) were compared to births by women referred to an OHC on the suspicion of other exposures than EDC (n = 620), and to a sample of births by all occupationally active women in the same geographical regions (n = 346,544), including 1,077 births of the referred women’s non-referred pregnancies. RESULTS: No indications of reduced birth weight or increased risk of preterm birth were found among women potentially exposed to EDC. Women potentially exposed to EDC had children with a higher birth weight compared to the sample of occupationally active women but not compared to other women referred to an OHC. CONCLUSIONS: Potential maternal exposure to EDC at Danish workplaces is not related to low birth weight or preterm birth among women referred to occupational counselling. Occupational exposures might be too weak on the average to cause these adverse effects or counselling at the OHCs is effective in preventing them