709 research outputs found

    Thermodynamic properties of binary HCP solution phases from special quasirandom structures

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    Three different special quasirandom structures (SQS) of the substitutional hcp A1xBxA_{1-x}B_x binary random solutions (x=0.25x=0.25, 0.5, and 0.75) are presented. These structures are able to mimic the most important pair and multi-site correlation functions corresponding to perfectly random hcp solutions at those compositions. Due to the relatively small size of the generated structures, they can be used to calculate the properties of random hcp alloys via first-principles methods. The structures are relaxed in order to find their lowest energy configurations at each composition. In some cases, it was found that full relaxation resulted in complete loss of their parental symmetry as hcp so geometry optimizations in which no local relaxations are allowed were also performed. In general, the first-principles results for the seven binary systems (Cd-Mg, Mg-Zr, Al-Mg, Mo-Ru, Hf-Ti, Hf-Zr, and Ti-Zr) show good agreement with both formation enthalpy and lattice parameters measurements from experiments. It is concluded that the SQS's presented in this work can be widely used to study the behavior of random hcp solutions.Comment: 15 pages, 8 figure

    In search of phylogenetic congruence between molecular and morphological data in bryozoans with extreme adult skeletal heteromorphy

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    peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=tsab20© Crown Copyright 2015. This document is the author's final accepted/submitted version of the journal article. You are advised to consult the publisher's version if you wish to cite from it

    MYStIX First Results: Spatial Structures of Massive Young Stellar Clusters

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    Astrophysics and Space Science Proceedings series vol. 36Observations of the spatial distributions of young stars in star-forming regions can be linked to the theory of clustered star formation using spatial statistical methods. The MYStIX project provides rich samples of young stars from the nearest high-mass star-forming regions. Maps of stellar surface density reveal diverse structure and subclustering. Young stellar clusters and subclusters are fit with isothermal spheres and ellipsoids using the Bayesian Information Criterion to estimate the number of subclusters. Clustering is also investigated using Cartwright and Whitworth's Q statistic and the inhomogeneous two-point correlation function. Mass segregation is detected in several cases, in both centrally concentrated and fractally structured star clusters, but a few clusters are not mass segregated.Chandra ACIS TeamNSFNAS

    The Danish multicentre randomized study of fibrinolytic therapy vs. primary angioplasty in acute myocardial infarction (the DANAMI-2 trial)::outcome after 3 years follow-up.

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      Udgivelsesdato: 2007-Oct-23Background The DANAMI-2 trial showed that in patients with ST-elevation myocardial infarction (STEMI), a strategy of inter-hospital transfer for primary angioplasty was superior to on-site fibrinolysis at 30 days follow-up. This paper reports on the pre-specified long-term composite endpoint at 3 years follow-up in DANAMI-2. Methods and results We randomized 1572 patients with STEMI to primary angioplasty or intravenous alteplase; 1129 patients were enrolled at 24 referral hospitals and 443 patients at 5 angioplasty centres. Ninety-six percent of inter-hospital transfers for angioplasty were completed within 2 h. No patients were lost to follow-up. The composite endpoint (death, clinical re-infarction, or disabling stroke) was reduced by angioplasty when compared with fibrinolysis at 3 years (19.6 vs. 25.2%, P = 0.006). For patients transferred to angioplasty compared with those receiving on-site fibrinolysis, the composite endpoint occurred in 20.1 vs. 26.7% (P = 0.007), death in 13.6 vs. 16.4% (P = 0.18), clinical re-infarction in 8.9 vs. 12.3% (P = 0.05), and disabling stroke in 3.2 vs. 4.7% (P = 0.23). Conclusion The benefit of transfer for primary angioplasty based on the composite endpoint was sustained after 3 years. For patients with characteristics as those in DANAMI-2, primary angioplasty should be the preferred treatment strategy when inter-hospital transfer can be completed within 2 h

    Quantum jumps of light recording the birth and death of a photon in a cavity

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    A microscopic system under continuous observation exhibits at random times sudden jumps between its states. The detection of this essential quantum feature requires a quantum non-demolition (QND) measurement repeated many times during the system evolution. Quantum jumps of trapped massive particles (electrons, ions or molecules) have been observed, which is not the case of the jumps of light quanta. Usual photodetectors absorb light and are thus unable to detect the same photon twice. They must be replaced by a transparent counter 'seeing' photons without destroying them3. Moreover, the light has to be stored over a duration much longer than the QND detection time. We have fulfilled these challenging conditions and observed photon number quantum jumps. Microwave photons are stored in a superconducting cavity for times in the second range. They are repeatedly probed by a stream of non-absorbing atoms. An atom interferometer measures the atomic dipole phase shift induced by the non-resonant cavity field, so that the final atom state reveals directly the presence of a single photon in the cavity. Sequences of hundreds of atoms highly correlated in the same state, are interrupted by sudden state-switchings. These telegraphic signals record, for the first time, the birth, life and death of individual photons. Applying a similar QND procedure to mesoscopic fields with tens of photons opens new perspectives for the exploration of the quantum to classical boundary

    Structure, computational and biochemical analysis of PcCel45A endoglucanase from <i>Phanerochaete chrysosporium </i>and catalytic mechanisms of GH45 subfamily C members

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    Abstract The glycoside hydrolase family 45 (GH45) of carbohydrate modifying enzymes is mostly comprised of β-1,4-endoglucanases. Significant diversity between the GH45 members has prompted the division of this family into three subfamilies: A, B and C, which may differ in terms of the mechanism, general architecture, substrate binding and cleavage. Here, we use a combination of X-ray crystallography, bioinformatics, enzymatic assays, molecular dynamics simulations and site-directed mutagenesis experiments to characterize the structure, substrate binding and enzymatic specificity of the GH45 subfamily C endoglucanase from Phanerochaete chrysosporium (PcCel45A). We investigated the role played by different residues in the binding of the enzyme to cellulose oligomers of different lengths and examined the structural characteristics and dynamics of PcCel45A that make subfamily C so dissimilar to other members of the GH45 family. Due to the structural similarity shared between PcCel45A and domain I of expansins, comparative analysis of their substrate binding was also carried out. Our bioinformatics sequence analyses revealed that the hydrolysis mechanisms in GH45 subfamily C is not restricted to use of the imidic asparagine as a general base in the “Newton’s cradle” catalytic mechanism recently proposed for this subfamily

    Effects of syntactic cueing therapy on picture naming and connected speech in acquired aphasia

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    Language therapy for word-finding difficulties in aphasia usually involves picture naming of single words with the support of cues. Most studies have addressed nouns in isolation, even though in connected speech nouns are more frequently produced with determiners. We hypothesised that improved word finding in connected speech would be most likely if intervention treated nouns in usual syntactic contexts. Six speakers with aphasia underwent language therapy using a software program developed for the purpose, which provided lexical and syntactic (determiner) cues. Exposure to determiners with nouns would potentially lead to improved picture naming of both treated and untreated nouns, and increased production of determiner plus noun combinations in connected speech. After intervention, picture naming of treated words improved for five of the six speakers, but naming of untreated words was unchanged. The number of determiner plus noun combinations in connected speech increased for four speakers. These findings attest to the close relationship between frequently co-occurring content and function words, and indicate that intervention for word-finding deficits can profitably proceed beyond single word naming, to retrieval in appropriate syntactic contexts. We also examined the relationship between effects of therapy, and amount and intensity of therapy. We found no relationship between immediate effects and amount or intensity of therapy. However, those participants whose naming maintained at follow-up completed the therapy regime in fewer sessions, of relatively longer duration. We explore the relationship between therapy regime and outcomes, and propose future considerations for research
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