Bremsstrahlung in alpha-Decay Reexamined

A high-statistics measurement of bremsstrahlung emitted in the alpha decay of 210Po has been performed, which allows to follow the photon spectra up to energies of ~ 500 keV. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasi classical approximation as well as with the exact quantum mechanical calculation. It is shown that due to the small effective electric dipole charge of the radiating system a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the alpha particle and the emitted photon.Comment: 10 pages, 5 figures, v2: fix of small typo

Bathymetry and Sediment Geochemistry of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut)

Arctic lakes can provide a long-term perspective on environmental change, including trends in long-range atmospheric transport and deposition of contaminants, inferred from studies of sediment cores. In this study, we conducted the first detailed bathymetric survey of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut), the world’s largest lake north of 74˚ latitude. With these data we were able to determine optimal locations for sediment coring and to collect and analyze profundal sediment cores. A bathymetric map of Lake Hazen was developed on the basis of 362 spot soundings obtained with GPS-coupled sounding equipment placed directly on the ice combined with additional soundings from a small boat. The deepest point in the lake (81˚49.5ʹ N; 70˚42.8ʹ W) was found to be 267 m deep. The lake volume was estimated to be 5.14 × 1010 m3, about 10% larger than previous estimates. Using estimates of the discharge of Lake Hazen from the Water Survey of Canada, we estimated the water retention time to be 89 years. Sediment cores were dated using 210Pb and 137Cs. Sedimentation rates at the deep point, estimated using the Constant Rate of Supply model for excess 210Pb, were relatively high (1260 g m-2yr-1) in the period 2005 – 1963 and lower (650 ± 100 g m-2yr-1) in horizons dated to 1950 – 1880. The majority of elements measured in sediment (24 of 29 consistently above detection limits), as well as organic carbon, showed less than 20% variation in concentrations in the top 10 cm (compacted depth), which represent deposition over approximately 140 years. Geochemical characteristics of the sediment suggest that erosional inputs from annual glacial melting are the major source of essentially all elements and that anthropogenic inputs from long-range transport of toxic metals such as mercury and lead are very low.Les lacs de l’Arctique peuvent fournir une perspective à long terme en matière de changement environnemental, notamment en ce qui a trait aux tendances relatives au transport atmosphérique et au dépôt de contaminants sur de longues périodes, tendances inférées à partir d’études de carottes de sédiments. Dans le cadre de la présente étude, nous avons effectué le premier levé bathymétrique détaillé du lac Hazen (parc national Quttinirpaaq, île d’Ellesmere, Nunavut), le plus grand lac de la planète situé au nord de 74˚ de latitude. Grâce aux données prélevées, nous avons réussi à déterminer les meilleurs emplacements pour le prélèvement de carottes de sédiments de même que pour la collecte et l’analyse de carottes de sédiments profonds. Une carte bathymétrique du lac Hazen a été dressée en fonction de 362 sondages obtenus au moyen de matériel d’appareils phoniques dotés de GPS placés directement sur la glace et supplémentés par des sondages recueillis à partir d’un petit bateau. Le point le plus profond du lac (81˚49,5ʹ N; 70˚42,8ʹ O) a été trouvé à 267 m de profondeur. Le volume du lac a été évalué à 5,14 × 1010 m3, soit 10 % de plus que les évaluations précédentes. À l’aide d’estimations du déversement du lac Hazen obtenues auprès de la Division des relevés hydrologiques du Canada, nous avons évalué que la durée de rétention de l’eau était de 89 ans. La datation des carottes de sédiments a été faite à l’aide de 210Pb et de 137Cs. Les taux de sédimentation au point profond, estimés en s’appuyant sur le modèle CRS (Constant Rate of Supply) pour l’excédent 210Pb, étaient relativement élevés (1260 g m-2an-1) pour la période allant de 2005 à 1963, et moins élevés (650 ± 100 g m-2an-1) pour la période de 1950 à 1880. La majorité des éléments mesurés dans les sédiments (24 sur 29 étaient uniformément au-dessus des seuils de détection) ainsi que dans le carbone organique ont produit une variation de concentrations de moins de 20 % dans les 10 cm supérieurs (profondeur compactée), ce qui représente des dépôts s’échelonnant sur environ 140 ans. Les caractéristiques géochimiques des sédiments laissent présumer que les matières d’érosion découlant de la fonte glaciaire annuelle constituent la source principale de sensiblement tous les éléments, et que les matières anthropiques provenant du transport à grande distance de métaux toxiques, tels que le mercure et le plomb, sont très faibles

Surface chemistry and stability of metastable corundum-type In2O3

To account for the explanation of an eventual sensing and catalytic behavior of rhombohedral In2O3 (rh-In2O3) and the dependence of the metastability of the latter on gas atmospheres, in situ electrochemical impedance spectroscopic (EIS), Fourier-transform infrared spectroscopic (FT-IR), in situ X-ray diffraction and in situ thermogravimetric analyses in inert (helium) and reactive gases (hydrogen, carbon monoxide and carbon dioxide) have been conducted to link the gas-dependent electrical conductivity features and the surface chemical properties to its metastability towards cubic In2O3. In particular, for highly reducible oxides such as In2O3, for which not only the formation of oxygen vacancies, but deep reduction to the metallic state (i.e. metallic indium) also has to be taken into account, this approach is imperative. Temperature-dependent impedance features are strongly dependent on the respective gas composition and are assigned to distinct changes in either surface adsorbates or free charge carrier absorbance, allowing for differentiating and distinguishing between bulk reduction-related features from those directly arising from surface chemical alterations. For the measurements in an inert gas atmosphere, this analysis specifically also included monitoring the fate of differently bonded, and hence, differently reactive, hydroxyl groups. Reduction of rh-In2O3 proceeds to a large extent indirectly via rh-In2O3 → c-In2O3 → In metal. As deduced from the CO and CO2 adsorption experiments, rhombohedral In2O3 exhibits predominantly Lewis acidic surface sites. The basic character is less pronounced, directly explaining the previously observed high (inverse) water–gas shift activity and the low CO2 selectivity in methanol steam reforming.DFG, SPP 1415, Kristalline Nichtgleichgewichtsphasen - Präparation, Charakterisierung und in situ-Untersuchung der Bildungsmechanisme

Renewable energy projects and species protection. A comparison into the application of the EU species protection regulation with respect to renewable energy projects in the Netherlands, United Kingdom, Belgium, Denmark and Germany

Renewable energy projects, such as offshore and onshore wind and solar farms, including the necessary infrastructure, have an impact on biodiversity. Given the status of biodiversity across Europe, and the ambitions for the maintenance of species, limiting the impact of renewable energy generation units on biodiversity is of fundamental importance. This study offers an insight into the incorporation of species protection aspects in current permit practices, and contributes to the discussion on dealing with species protection issues in the process of upscaling sustainable energy facilities

Structural and Electrochemical Properties of Physisorbed and Chemisorbed Water Layers on the Ceramic Oxides Y2O3, YSZ, and ZrO2

A combination of operando Fourier transform infrared spectroscopy, operando electrochemical-impedance spectroscopy, and moisture-sorption measurements has been exploited to study the adsorption and conduction behavior of H2O and D2O on the technologically important ceramic oxides YSZ (8 mol % Y2O3), ZrO2, and Y2O3. Because the characterization of the chemisorbed and physisorbed water layers is imperative to a full understanding of (electro-)catalytically active doped oxide surfaces and their application in technology, the presented data provide the specific reactivity of these oxides toward water over a pressure-and-temperature parameter range extending up to, e.g., solid-oxide fuel cell (SOFC)-relevant conditions. The characteristic changes of the related infrared bands could directly be linked to the associated conductivity and moisture-sorption data. For YSZ, a sequential dissociative water (“ice-like” layer) and polymeric chained water (“liquid-like”) water-adsorption model for isothermal and isobaric conditions over a pressure range of 10-5 to 24 mbar and a temperature range from room temperature up to 1173 K could be experimentally verified. On pure monoclinic ZrO2, in contrast to highly hydroxylated YSZ and Y2O3, a high surface concentration of OH groups from water chemisorption is absent at any temperature and pressure. Thus, the ice-like and following molecular water layers exhibit no measurable protonic conduction. We show that the water layers, even under these rather extreme experimental conditions, play a key role in understanding the function of these materials. Furthermore, the reported data are supposed to provide an extended basis for the further investigation of close-to-real gas adsorption or catalyzed heterogeneous reactions.(VLID)1371561Accepted versio

Generation of Covalently Closed Circular DNA of Hepatitis B Viruses via Intracellular Recycling Is Regulated in a Virus Specific Manner

Persistence of hepatitis B virus (HBV) infection requires covalently closed circular (ccc)DNA formation and amplification, which can occur via intracellular recycling of the viral polymerase-linked relaxed circular (rc) DNA genomes present in virions. Here we reveal a fundamental difference between HBV and the related duck hepatitis B virus (DHBV) in the recycling mechanism. Direct comparison of HBV and DHBV cccDNA amplification in cross-species transfection experiments showed that, in the same human cell background, DHBV but not HBV rcDNA converts efficiently into cccDNA. By characterizing the distinct forms of HBV and DHBV rcDNA accumulating in the cells we find that nuclear import, complete versus partial release from the capsid and complete versus partial removal of the covalently bound polymerase contribute to limiting HBV cccDNA formation; particularly, we identify genome region-selectively opened nuclear capsids as a putative novel HBV uncoating intermediate. However, the presence in the nucleus of around 40% of completely uncoated rcDNA that lacks most if not all of the covalently bound protein strongly suggests a major block further downstream that operates in the HBV but not DHBV recycling pathway. In summary, our results uncover an unexpected contribution of the virus to cccDNA formation that might help to better understand the persistence of HBV infection. Moreover, efficient DHBV cccDNA formation in human hepatoma cells should greatly facilitate experimental identification, and possibly inhibition, of the human cell factors involved in the process

"Safe" Coulomb Excitation of 30Mg

We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy of 2.25 MeV/u together with a thin nat-Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative de-excitation gamma ray yields the B(E2; 0+ -> 2+) value of 30Mg was determined to be 241(31) e2fm4. Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope 30Mg lies still outside the ``island of inversion''

Lifetime measurements in 80^{80}Br and a new region for observation of chiral electromagnetic selection rules

Level lifetimes for the candidate chiral doublet bands of 80Br were extracted by means of the Doppler-shift attenuation method. The absolute transition probabilities derived from the lifetimes agree well with the M1 and E2 chiral electromagnetic selection rules, and are well reproduced by the triaxial particle rotor model calculations. Such good agreements among the experimental data, selection rules of chiral doublet bands and theoretical calculations are rare and outstanding in researches of nuclear chirality. Besides odd-odd Cs isotopes, odd-odd Br isotopes in the A≈ 80 mass region represent another territory that exhibits the ideal selection rules expected for chiral doublet bands

Epidemiology of Extended-Spectrum beta-Lactamase-Producing E-coli and Vancomycin-Resistant Enterococci in the Northern Dutch-German Cross-Border Region

Objectives: To reveal the prevalence and epidemiology of extended-spectrum β-lactamase (ESBL)- and/or plasmid AmpC (pAmpC)- and carbapenemase (CP) producing Enterobacteriaceae and vancomycin-resistant enterococci (VRE) across the Northern Dutch–German border region.Methods: A point-prevalence study on ESBL/pAmpC/CP producing Enterobacteriaceae and VRE was carried out in hospitalized patients in the Northern Netherlands (n = 445, 2012–2013) and Germany (n = 242, 2012). Healthy individuals from the Dutch community (n = 400, 2010–2012) were also screened. In addition, a genome-wide gene-by-gene approach was applied to study the epidemiology of ESBL-Escherichia coli and VRE.Results: A total of 34 isolates from 27 patients (6.1%) admitted to Dutch hospitals were ESBL/pAmpC positive and 29 ESBL-E. coli, three pAmpC-E. coli, one ESBL-Enterobacter cloacae, and one pAmpC-Proteus mirabilis were found. In the German hospital, 18 isolates (16 E. coli and 2 Klebsiella pneumoniae) from 17 patients (7.7%) were ESBL positive. In isolates from the hospitalized patients CTX-M-15 was the most frequently detected ESBL-gene. In the Dutch community, 11 individuals (2.75%) were ESBL/pAmpC positive: 10 ESBL-E. coli (CTX-M-1 being the most prevalent gene) and one pAmpC E. coli. Six Dutch (1.3%) and four German (3.9%) hospitalized patients were colonized with VRE. Genetic relatedness by core genome multi-locus sequence typing (cgMLST) was found between two ESBL-E. coli isolates from Dutch and German cross-border hospitals and between VRE isolates from different hospitals within the same region.Conclusion: The prevalence of ESBL/pAmpC-Enterobacteriaceae was similar in hospitalized patients across the Dutch–German border region, whereas VRE prevalence was slightly higher on the German side. The overall prevalence of the studied pathogens was lower in the community than in hospitals in the Northern Netherlands. Cross-border transmission of ESBL-E. coli and VRE seems unlikely based on cgMLST analysis, however continuous monitoring is necessary to control their spread and stay informed about their epidemiology