644 research outputs found

    Hjarnø Sund – all year, all inclusive: A submerged Late Mesolithic coastal site with organic remains

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    Between 2009 and 2016, a series of investigations were undertaken at a submerged settlement of the island of Hjarnø in Horsens Fjord, Denmark. The work was prompted by the discovery in 2008 that heavy erosion of a gyttja deposit containing archaeological remains had resulted in artefacts of bone, antler and, not least, wood becoming exposed on the seabed. The investigations revealed that occupation of the site, with a few exceptions, dates to the first half of the Ertebølle culture (5400–4700 BC). In addition to numerous well-preserved artefacts made of organic materials, several areas were found to contain intact shell layers from submerged kitchen middens. Deposits of this kind have not previously been demonstrated in Denmark

    Robust half-metallic antiferromagnets LaAAVOsO6_6 and LaAAMoYYO6_6 (AA = Ca, Sr, Ba; YY = Re, Tc) from first-principles calculations

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    We have theoretically designed three families of the half-metallic (HM) antiferromagnets (AFM), namely, LaAAVOsO6_6, LaAAMoTcO6_6 and LaAAMoReO6_6 (AA = Ca, Sr, Ba), based on a systematic {\it ab initio} study of the ordered double perovskites LaABBABB'O6_6 with the possible BB and BB' pairs from all the 3dd, 4dd and 5dd transtion metal elements being considered. Electronic structure calculations based on first-principles density-functional theory with generalized gradient approximation (GGA) for more than sixty double perovskites LaCaBBBB'O6_6 have been performed using the all-electron full-potential linearized augmented-plane-wave method. The found HM-AFM state in these materials survives the full {\it ab initio} lattice constant and atomic position optimizations which were carried out using frozen-core full potential projector augmented wave method. It is found that the HM-AFM properties predicted previously in some of the double perovskites would disappear after the full structural optimizations. The AFM is attributed to both the superexchange mechanism and the generalized double exchange mechanism via the BB (t2gt_{2g}) - O (2pπp_{\pi}) - BB' (t2gt_{2g}) coupling and the latter is also believed to be the origin of the HM. Finally, in our search for the HM-AFMs, we find LaAACrTcO6_6 and LaAACrReO6_6 to be AFM insulators of an unconventional type in the sense that the two antiferromagnetic coupled ions consist of two different elements and that the two spin-resolved densities of states are no longer the same.Comment: To appear in Phys. Rev.

    Interface magnetism of 3d transition metals

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    LDA+DMFT computation of the electronic spectrum of NiO

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    The electronic spectrum, energy gap and local magnetic moment of paramagnetic NiO are computed by using the local density approximation plus dynamical mean-field theory (LDA+DMFT). To this end the noninteracting Hamiltonian obtained within the local density approximation (LDA) is expressed in Wannier functions basis, with only the five anti-bonding bands with mainly Ni 3d character taken into account. Complementing it by local Coulomb interactions one arrives at a material-specific many-body Hamiltonian which is solved by DMFT together with quantum Monte-Carlo (QMC) simulations. The large insulating gap in NiO is found to be a result of the strong electronic correlations in the paramagnetic state. In the vicinity of the gap region, the shape of the electronic spectrum calculated in this way is in good agreement with the experimental x-ray-photoemission and bremsstrahlung-isochromat-spectroscopy results of Sawatzky and Allen. The value of the local magnetic moment computed in the paramagnetic phase (PM) agrees well with that measured in the antiferromagnetic (AFM) phase. Our results for the electronic spectrum and the local magnetic moment in the PM phase are in accordance with the experimental finding that AFM long-range order has no significant influence on the electronic structure of NiO.Comment: 15 pages, 6 figures, 1 table; published versio

    Calculated stacking-fault energies of elemental metals

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    Compositional disorder and its influence on the structural, electronic and magnetic properties of MgC(Ni_{1-x}Co_{x})_{3} alloys using first-principles

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    First-principles, density-functional based electronic structure calculations are carried out for MgC(Ni_{1-x}Co_{x})_{3} alloys over the concentration range 0\leq x\leq1, using Korringa-Kohn-Rostoker coherent-potential approximation (KKR CPA) method in the atomic sphere approximation (ASA). The self-consistent calculations are used to study the changes as a function of x in the equation of state parameters, total and partial densities of states, magnetic moment and the on-site exchange interaction parameter. To study the magnetic properties as well as its volume dependence, fixed-spin moment calculations in conjunction with the phenomenological Landau theory are employed. The salient features that emerge from these calculations are (i) a concentration independent variation in the lattice parameter and bulk modulus at x~0.75 with an anomaly in the variation of the pressure derivative of bulk modulus, (ii) the fixed-spin moment based corrections to the overestimated magnetic ground state for 0.0\leq x\leq0.3 alloys, making the results consistent with the experiments, and (iii) the possibility of multiple magnetic states at x~0.75, which, however, requires further improvements in the calculations

    Does Training and Support of General Practitioners in Intensive Treatment of People with Screen-Detected Diabetes Improve Medication, Morbidity and Mortality in People with Clinically-Diagnosed Diabetes? Investigation of a Spill-Over Effect in a Cluster RCT

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    Introduction\textbf{Introduction} Very few studies have examined the potential spill-over effect of a trial intervention in general practice. We investigated whether training and support of general practitioners in the intensive treatment of people with screen-detected diabetes improved rates of redeemed medication, morbidity and mortality in people with clinically-diagnosed diabetes. Methods\textbf{Methods} This is a secondary, post-hoc, register-based analysis linked to a cluster randomised trial. In the ADDITION-Denmark\textit{ADDITION-Denmark} trial, 175 general practices were cluster randomised (i) to routine care, or (ii) to receive training and support in intensive multifactorial treatment of individuals with screen-detected diabetes (2001 to 2009). Using national registers we identified all individuals who were diagnosed with clinically incident diabetes in the same practices over the same time period. (Patients participating in the ADDITION trial were excluded). We compared rates of redeemed medication, a cardiovascular composite endpoint, and all-cause mortality between the routine care and intensive treatment groups. Results\textbf{Results} In total, 4,107 individuals were diagnosed with clinically incident diabetes in ADDITION-Denmark\textit{ADDITION-Denmark} practices between 2001 and 2009 (2,051 in the routine care group and 2,056 in the intensive treatment group). There were large and significant increases in the proportion of patients redeeming cardio-protective medication in both treatment groups during follow- up. After a median of seven years of follow-up, there was no difference in the incidence of a composite cardiovascular endpoint (HR 1.15, 95% CI 0.95 to 1.38) or all-cause mortality between the two groups (HR 1.08, 95% CI 0.94 to 1.23). Discussion\textbf{Discussion} There was no evidence of a spill-over effect from an intervention promoting intensive treatment of people with screen-detected diabetes to those with clinically-diagnosed diabetes. Overall, the proportion of patients redeeming cardio-protective medication during follow-up was similar in both groups. Trial Registration\textbf{Trial Registration} ClinicalTrials.gov NCT00237549Novo Nordisk Foundation (Grant ID: NNF14OC0008981
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