First-principles computational study of defect clustering in solid solutions of ThO2_{2} with trivalent oxides

The energetics of mixing and defect ordering in solid solutions of fluorite-structured ThO$_{2}$ with oxides of trivalent cations (Sc, In, Y, Nd, La) are investigated by electronic density-functional-theory (DFT). Through DFT calculations of structures enumerated by lattice-algebra techniques, we identify the lowest-energy patterns for defect clustering for four separate dopant concentrations. The most stable structures are characterized by a repulsive interaction between nearest-neighbor vacancies on the oxygen sublattice. The enthalpies of formation with respect to constituent oxides are positive for all dopants considered, and show a tendency to decrease in magnitude as the size and electronegativity of the trivalent dopant decrease. Due to the small positive formation enthalpies and low oxygen-vacancy binding energy with La dopants, La$_{2}$O$_{3}$-ThO$_{2}$ solid solutions are predicted to have relatively high ionic conductivities relative to those for the other aliovalent dopants considered. Our results are compared with those for the more widely studied ZrO$_{2}$ and CeO$_{2}$ fluorite-structured solid solutions with trivalent cations.Comment: 9 pages, 8 figure

A New Cross-domain Strategy - Safeguarding the Danish Cultural Heritage

Intervention à la 33e conférence générale annuelle de la Ligue des bibliothèques européennes de recherche (Liber)

ORGANIC AGRICULTURE AND FOOD SECURITY

Modelling the impacts of organic production up-scaled to regional and global levels gives an initial quan-tification of the potential extent of changes that large-scale conversion might induce. Optimistic estimates of change with respect to organic yield potential lead to modest impacts on global commodity prices, production, and trade. Conversion in high-input regions in Europe and North America to certified organic decreases production and increases commodity prices. Hunger in this scenario slightly worsens. Transition of low-input areas in Sub-Saharan Africa to non-certified organic leads to in-creased production and decreased prices. Food secu-rity improves slightly in this scenario. The switch for low-input regions helps decrease trade dependency in some commodities. Achievement of productivity levels in these scenarios is dependent on many factors that introduce a significant amount of uncertainty in the results. The extent of these impacts can be improved if concerted effort in research and development for yield and productivity enhancement is supported

Predicting case numbers during infectious diseaseoutbreaks when some cases are undiagnosed

We describe a method for calculating 95 per cent bounds for the current number of hidden cases and the future number of diagnosed cases during an outbreak of an infectious disease. A Bayesian Markov chain Monte Carlo approach is used to fit a model of infectious disease transmission that takes account of undiagnosed cases. Assessing this method on simulated data, we find that it provides conservative 95 per cent bounds for the number of undiagnosed cases and future case numbers, and that these bounds are robust to modifications in the assumptions generating the simulated data. Moreover, the method provides a good estimate of the initial reproduction number, and the reproduction number in the latter stages of the outbreak. Applying the approach to SARS data from Hong Kong, Singapore, Taiwan and Canada, the bounds on future diagnosed cases are found to be reliable, and the bounds on hidden cases suggests that there were few hidden cases remaining at the end of the outbreaks in each region. We estimate that the initial reproduction numbers lay between 1.5 and 3, and the reproduction numbers in the later stages of the outbreak lay between 0.36 and 0.6

A Computational Study of the Proton-Transfer Chemistry of the Silaformyl Anion

Proton-transfer reactions involving the silaformyl anion, HSiO-, and its conjugate acids, HSiOH and H2SiO, have been investigated with ab initio methods. Calculations through fourth-order perturbation theory suggest possible routes for proton transfer. Accurate estimates for the acidity of H2SiO and HSiOH are presented and discussed in light of earlier experimental estimates

Leakage after surgery for rectum cancer; inconsistency in reporting to the Danish Colorectal Cancer Group?

Purpose. Anastomotic leakage accounts for up to 1/3 of all fatalities after rectal cancer surgery. Evidence suggests that anastomotic leakage has a negative prognostic impact on local cancer recurrence and long-term cancer specific survival. The reported leakage rate in 2011 in Denmark varied from 7 to 45 percent. The objective was to clarify if the reporting of anastomotic leakage to the Danish Colorectal Cancer Group was rigorous and unequivocal. Methods. An Internet-based questionnaire was e-mailed to all Danish surgical departments, who reported to Danish Colorectal Cancer Group (DCCG) in 2011. There were 23 questions. Four core questions were whether pelvic collection, fecal appearance in a pelvic drain, rectovaginal fistula, and “watchfull” waiting patients were reported as anastomotic leakage. Results. Fourteen out of 17 departments, who in 2011 according to DDCG performed rectal cancer surgery, answered the questionnaire. This gave a response rate of 82%. In three of four core questions there was disagreement in what should be reported as anastomotic leakage. Conclusion. The reporting of anastomotic leakage to the Danish Colorectal Cancer Group was not rigorous and unequivocal. The reported anastomotic leakage rate in Danish Colorectal Cancer Group should be interpreted with caution

Strange matter prospects within the string-flip model

In this contribution we extend the recently developed two-flavor quark-matter string-flip model by including strange quarks. We discuss implications for compact stars.Comment: 4 pages, 4 figures, proceedings to SQM201

Spatial variability of snow chemistry in western Dronning Maud Land, Antarctica

During the austral summer of 1993-94 a number of 1-2 m deep snow pits were sampled in connection with firn-coring in western Dronning Maud Land, Antarctica. The traverse went from 800 to about 3000 m a.s.l. upon the high-altitude plateau. Profiles of cations (Na+, K+, Mg2+, Ca2+), anions (Cl−, NO3-, SO4 2- , CH3SO3 −) and stable oxygen isotopes (δ18O) from 11 snow pils are presented here. Close to the coast 2 m of snow accumulates in about 2-3 years, whilst at sites on the high-altitude plateau 2 m of snow accumulates in 10—14 years. The spatial variation in ion concentrations shows that the ions can be divided into two groups, one with sea-salt elements and methane sulfonate and the other with nitrate and sulfate. For the sca-salt elements and methane sulfonate the concentrations decrease with increasing altitude and increasing distance from the coast, as well as with decreasing temperature and decreasing accumulation rate. For nitrate and sulfate the concentrations are constant or increase with respect to these parameters. This pattern suggests that the sources for sca-salt elements and methane sulfonate are local, whereas the sources for nitrate and sulfate are a mixture of local and long-range transport