1,217 research outputs found

    Relativistic Calculation of two-Electron one-Photon and Hypersatellite Transition Energies for 12≀Z≀3012\leq Z\leq30 Elements

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    Energies of two-electron one-photon transitions from initial double K-hole states were computed using the Dirac-Fock model. The transition energies of competing processes, the Kα\alpha hypersatellites, were also computed. The results are compared to experiment and to other theoretical calculations.Comment: accepted versio

    Resolution and enhancement in nanoantenna-based fluorescence microscopy

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    Single gold nanoparticles can act as nanoantennas for enhancing the fluorescence of emitters in their near-fields. Here we present experimental and theoretical studies of scanning antenna-based fluorescence microscopy as a function of the diameter of the gold nanoparticle. We examine the interplay between fluorescence enhancement and spatial resolution and discuss the requirements for deciphering single molecules in a dense sample. Resolutions better than 20 nm and fluorescence enhancement up to 30 times are demonstrated experimentally. By accounting for the tip shaft and the sample interface in finite-difference time-domain calculations, we explain why the measured fluorescence enhancements are higher in the presence of an interface than the values predicted for a homogeneous environment.Comment: 10 pages, 3 figures. accepted for publication in Nano Letter

    The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten

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    Several transition metals were examined to evaluate their potential for improving the ductility of tungsten. The dislocation core structure and Peierls stress and barrier of 1/21/2 screw dislocations in binary tungsten-transition metal alloys (W1−x_{1-x}TMx_{x}) were investigated using first principles electronic structure calculations. The periodic quadrupole approach was applied to model the structure of 1/21/2 dislocation. Alloying with transition metals was modeled using the virtual crystal approximation and the applicability of this approach was assessed by calculating the equilibrium lattice parameter and elastic constants of the tungsten alloys. Reasonable agreement was obtained with experimental data and with results obtained from the conventional supercell approach. Increasing the concentration of a transition metal from the VIIIA group, i.e. the elements in columns headed by Fe, Co and Ni, leads to reduction of the Câ€ČC^\prime elastic constant and increase of elastic anisotropy A=C44/Câ€ČC_{44}/C^\prime. Alloying W with a group VIIIA transition metal changes the structure of the dislocation core from symmetric to asymmetric, similar to results obtained for W1−x_{1-x}Rex_{x} alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503 (2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry, the values of the Peierls stress and barrier are reduced. The latter effect could lead to increased ductility in a tungsten-based alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any of the transition metals from the VIIIA group should have similar effect as alloying with Re.Comment: 12 pages, 8 figures, 3 table

    Survival in severe alpha-1-antitrypsin deficiency (PiZZ)

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    <p>Abstract</p> <p>Background</p> <p>Previous studies of the natural history of alpha-1-antitrypsin (AAT) deficiency are mostly based on highly selected patients. The aim of this study was to analyse the mortality of PiZZ individuals.</p> <p>Methods</p> <p>Data from 1339 adult PiZZ individuals from the Swedish National AAT Deficiency Registry, followed from 1991 to 2008, were analysed. Forty-three percent of these individuals were identified by respiratory symptoms (respiratory cases), 32% by liver diseases and other diseases (non-respiratory cases) and 25% by screening (screened cases). Smoking status was divided into two groups: smokers 737 (55%) and 602 (45%) never-smokers.</p> <p>Results</p> <p>During the follow-up 315 individuals (24%) died. The standardised mortality rate (SMR) for respiratory cases was 4.70 (95% Confidence Interval (CI) 4.10-5.40), 3.0 (95%CI 2.35-3.70) for the non-respiratory cases and 2.30 (95% CI 1.46-3.46) for the screened cases. The smokers had a higher mortality risk than never-smokers, with a SMR of 4.80 (95%CI 4.20-5.50) for the smokers and 2.80(95%CI 2.30-3.40) for the never-smokers. The Rate Ratio (RR) was 1.70 (95% CI 1.35-2.20). Also among the screened cases, the mortality risk for the smokers was significantly higher than in the general Swedish population (SMR 3.40 (95% CI 1.98-5.40).</p> <p>Conclusion</p> <p>Smokers with severe AAT deficiency, irrespective of mode of identification, have a significantly higher mortality risk than the general Swedish population.</p

    Ultrahigh Surface Area Three-Dimensional Porous Graphitic Carbon from Conjugated Polymeric Molecular Framework

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    Porous graphitic carbon is essential for many applications such as energy storage devices, catalysts, and sorbents. However, current graphitic carbons are limited by low conductivity, low surface area, and ineffective pore structure. Here we report a scalable synthesis of porous graphitic carbons using a conjugated polymeric molecular framework as precursor. The multivalent cross-linker and rigid conjugated framework help to maintain micro- and mesoporous structures, while promoting graphitization during carbonization and chemical activation. The above unique design results in a class of highly graphitic carbons at temperature as low as 800 ??C with record-high surface area (4073 m2 g-1), large pore volume (2.26 cm-3), and hierarchical pore architecture. Such carbons simultaneously exhibit electrical conductivity &gt;3 times more than activated carbons, very high electrochemical activity at high mass loading, and high stability, as demonstrated by supercapacitors and lithium-sulfur batteries with excellent performance. Moreover, the synthesis can be readily tuned to make a broad range of graphitic carbons with desired structures and compositions for many applications.clos

    Evaluated displacement and gas production cross-sections for materials irradiated with intermediate energy nucleons

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    International Conference on Nuclear Data for Science and Technology (ND) -- SEP 11-16, 2016 -- Bruges, BELGIUMWOS: 000426429500034Atomic displacement and gas production cross-sections were obtained for a number of materials to calculate radiation damage and gas production rate in nuclear-and fusion reactors, and neutron spallation sources. An advanced atomistic modelling approach was applied for calculations of the number of stable displacements in materials.Fusion for Energy [F4E-GRT-168.01, F4E-GRT-168.02]The work leading to this publication has been funded partially by Fusion for Energy under the Specific Grant Agreements F4E-GRT-168.01 and F4E-GRT-168.02. This publication reflects the views only of the authors, and Fusion for Energy cannot be held responsible for any use which may be made of the information contained therein

    The sensuous secrets of shelter: how recollections of food stimulate Irish men's reconstructions of their early formative residential experiences in Leicester, Sheffield and Manchester

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    This paper examines the intersection between food, recollection and Irish migrants’ reconstructions of their housing pathways in the three English cities of Leicester (East Midlands), Sheffield (South Yorkshire) and Manchester (North). Previous studies have acknowledged more implicitly the role of memory in representing the Irish migrant experience in England. Here, we adopt a different stance. We explore the mnemonic power of food to encode, decode and recode Irish men’s reconstructions of their housing pathways in England when constructing and negotiating otherness. In doing so, we apply a ‘Proustian anthropological’ approach in framing the men’s representations of their formative residential experiences in the boarding houses of the three English cities during the 1950s and 1960s are examined. The extent to which food provided in the boarding houses was used as an instrument of discipline and control is examined. The relevance of food related acts of resistance, food insecurity and acts of hedonic meat-centric eating in constructing the men’s sociocultural identity are also explored

    BDSM Disclosure and Stigma Management: Identifying Opportunities for Sex Education

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    While participation in the activities like bondage, domination, submission/sadism, masochism that fall under the umbrella term BDSM is widespread, stigma surrounding BDSM poses risks to practitioners who wish to disclose their interest. We examined risk factors involved with disclosure to posit how sex education might diffuse stigma and warn of risks. Semi-structured interviews asked 20 adults reporting an interest in BDSM about their disclosure experiences. Most respondents reported their BDSM interests starting before age 15, sometimes creating a phase of anxiety and shame in the absence of reassuring information. As adults, respondents often considered BDSM central to their sexuality, thus disclosure was integral to dating. Disclosure decisions in nondating situations were often complex considerations balancing desire for appropriateness with a desire for connection and honesty. Some respondents wondered whether their interests being found out would jeopardize their jobs. Experiences with stigma varied widely
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