2,201 research outputs found

    Electron Counting Rules and Electronic Structure in Tetrameric Transition-Metal (T)-Centered Rare-Earth (R) Cluster Complex Halides (X)

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    Electron partition schemes are a beneficial means to systematize bonding networks and to identify structure-bonding relationships in polar intermetallics. One prolific class of polymetal networks with simple counterions is the broad family of transition-metal (T)-centered rare-earth metal (R) cluster halides (X), which can be isolated or condensed to oligomers and chains. While the electronic structures of R cluster monomers and chains encapsulating T atoms have been studied systematically, the band structures of oligomers, in particular, the most frequent Friauf-type {T4R16} tetramers, have been investigated to a lesser extent. Therefore, the band structures of prototypical compounds with {T4R16}-type tetramers, while maintaining different compositions, were analyzed employing density functional theory based methods. Furthermore, these theoretical examinations provide insight into the origin of the 15 electron rule, which is significant for this class of compounds and correlates with the closed-shell configurations for these structures. Additional research focused on the band structure of monoclinic {Ru4Gd16}Br23, which is composed of rhomboid-shaped {Ru4Gd16} tetramers

    Identifying a Structural Preference in Reduced Rare-Earth Metal Halides by Combining Experimental and Computational Techniques

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    The structures of two new cubic {TnLa3}Br3 (Tn = Ru, Ir; I4132, Z = 8; Tn = Ru: a = 12.1247(16) Å, V = 1782.4(4) Å3; Tn = Ir: a = 12.1738(19) Å, V = 1804.2(5) Å3) compounds belonging to a family of reduced rare-earth metal halides were determined by single-crystal X-ray diffraction. Interestingly, the isoelectronic compound {RuLa3}I3 crystallizes in the monoclinic modification of the {TnR3}X3 family, while {IrLa3}I3 was found to be isomorphous with cubic {PtPr3}I3. Using electronic structure calculations, a pseudogap was identified at the Fermi level of {IrLa3}Br3 in the new cubic structure. Additionally, the structure attempts to optimize (chemical) bonding as determined through the crystal orbital Hamilton populations (COHP) curves. The Fermi level of the isostructural {RuLa3}Br3 falls below the pseudogap, yet the cubic structure is still formed. In this context, a close inspection of the distinct bond frequencies reveals the subtleness of the structure determining factors

    Interseismic and Postseismic Shallow Creep of the North Qaidam Thrust Faults Detected with a Multitemporal InSAR Analysis

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    Understanding the mechanisms by which earthquake cycles produce folding and accommodate shortening is essential to quantify the seismic potential of active faults and integrate aseismic slip within our understanding of the physical mechanisms of the long-term deformation. However, measuring such small deformation signals in mountainous areas is challenging with current space-geodesy techniques, due to the low rates of motion relative to the amplitude of the noise. Here we successfully carry out a multitemporal Interferometric Synthetic Aperture Radar analysis over the North Qaidam fold-thrust system in NE Tibet, where eight Mw> 5.2 earthquakes occurred between 2003 and 2009. We report various cases of aseismic slip uplifting the thickened crust at short wavelengths. We provide a rare example of a steep, shallow, 13-km-long and 6-km-wide afterslip signal that coincides spatially with an anticline and that continues into 2011 in response to a Mw 6.3 event in 2003. We suggest that a buried seismic slip during the 2003 earthquake has triggered both plastic an-elastic folding and aseismic slip on the shallow thrusts. We produce a first-order two-dimensional model of the postseismic surface displacements due to the 2003 earthquake and highlight a segmented slip on three fault patches that steepen approaching the surface. This study emphasizes the fundamental role of shallow aseismic slip in the long-term and permanent deformation of thrusts and folds and the potential of Interferometric Synthetic Aperture Radar for detecting and characterizing the spatiotemporal behavior of aseismic slip over large mountainous regions

    Building a collaborative culture in cardiothoracic operating rooms: Pre and postintervention study protocol for evaluation of the implementation of teamSTEPPS training and the impact on perceived psychological safety

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    IntroductionThe importance of effective communication, a key component of teamwork, is well recognised in the healthcare setting. Establishing a culture that encourages and empowers team members to speak openly in the cardiothoracic (CT) operating room (OR) is necessary to improve patient safety in this high-risk environment.Methods and analysisThis study will take place at Barnes-Jewish Hospital, an academic hospital in affiliation with Washington University School of Medicine located in the USA. All team members participating in cardiac and thoracic OR cases during this 17-month study period will be identified by the primary surgical staff attending on the OR schedule.TeamSTEPPS (Team Strategies and Tools to Enhance Performance and Patient Safety) training course will be taught to all CT OR staff. Before TeamSTEPPS training, staff will respond to a 39-item questionnaire that includes constructs from the Agency for Healthcare Research and Quality Hospital Survey on Patient Safety Culture, Edmondson’s ‘Measure of psychological safety’ questionnaire, and questionnaires on turnover intentions, job satisfaction and ‘burnout’. The questionnaires will be readministered at 6 and 12 months.The primary outcomes to be assessed include the perceived psychological safety of CT OR team members, the overall effect of TeamSTEPPS on burnout and job satisfaction, and observed turnover rate among the OR nurses. As secondary outcomes, we will be assessing self-reported rates of medical error and near misses in the ORs with a questionnaire at the end of each case.Ethics and disseminationEthics approval is not indicated as this project does not meet the federal definitions of research requiring the oversight of the Institutional Review Board (IRB). Patient health information (PHI) will not be generated during the implementation of this project. Results of the trial will be made accessible to the public when published in a peer-reviewed journal following the completion of the study.</jats:sec

    One-Year Prospective Prediction of Violence Perpetration Among High Risk Youth from Personal and Social-Environmental Variables

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    Objective: Measures of drug use, law-abidance beliefs, sensation seeking, fear of victimization, high-risk group identification, self- protection needs and behaviors, and demographics were investigated as longitudinal predictors of violence perpetration among 870 high-risk adolescents. Method: Self-reports from the same youth were obtained 1-year apart. Results: In addition to baseline violence perpetration, marijuana use, relatively youn1 age, male sex, high-risk group self-identification, low perceived efficacy of the police department, and nonavoidance of dangerous places predicted later perpetrated violence. Conclusion: Personal and social factors beyond baseline violent behavior predict risk for future violent behavior

    Cation-Poor Complex Metallic Alloys in Ba(Eu)–Au–Al(Ga) Systems: Identifying the Keys that Control Structural Arrangements and Atom Distributions at the Atomic Level

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    Four complex intermetallic compounds BaAu6±xGa6±y (x = 1, y = 0.9) (I), BaAu6±xAl6±y (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104–112, Fm3̅c), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution (“coloring scheme”). Chemical bonding analyses for two different “EuAu6Tr6” models reveal maximization of the number of heteroatomic Au–Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the “EuAu6Tr6” models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 ÎŒB/f.u. at 2 K. The effective moments of 8.3 ÎŒB/f.u., determined from Curie–Weiss fits, point to divalent oxidation states for europium in both III and IV
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