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The use of crystals other than silicon for x-ray optics is becoming more common for many challenging experiments such as resonant inelastic x-ray scattering and nuclear resonant scattering. As more—and more specialized—spectrometers become available at many synchrotron radiation facilities, interest in pushing the limits of experimental energy resolution has increased. The potentially large improvements in resolution and efficiency that nonsilicon optics offer are beginning to be realized. This article covers the background and state of the art for nonsilicon crystal optics with a focus on a resolution of 10 meV or better, concentrating on compounds that form trigonal crystals, including sapphire, quartz, and lithium niobate, rather than the more conventional cubic materials, including silicon, diamond, and germanium.
To evaluate a computer-assisted point-prevalence survey (CAPPS) for hospital-acquired infections (HAIs).
A 754-bed teaching hospital in the Netherlands.
For the internal validation of a CAPPS for HAIs, 2,526 patients were included. All patient records were retrospectively reviewed in depth by 2 infection control practitioners (ICPs) to determine which patients had suffered an HAI. Preventie van Ziekenhuisinfecties door Surveillance (PREZIES) criteria were used. Following this internal validation, 13 consecutive CAPPS were performed in a prospective study from January to March 2013 to determine weekly, monthly, and quarterly HAI point prevalence. Finally, a CAPPS was externally validated by PREZIES (Rijksinstituut voor Volksgezondheid en Milieu [RIVM], Bilthoven, Netherlands). In all evaluations, discrepancies were resolved by consensus.
In our series of CAPPS, 83% of the patients were automatically excluded from detailed review by the ICP. The sensitivity of the method was 91%. The time spent per hospital-wide CAPPS was ~3 hours. External validation showed a negative predictive value of 99.1% for CAPPS.
CAPPS proved to be a sensitive, accurate, and efficient method to determine serial weekly point-prevalence HAI rates in our hospital.
Neubert, Mainert, Kretzschmar, and Greiff (2015) plea to integrate the 21st century skills of complex problem solving (CPS) and collaborative problem solving (ColPS) in the assessment and development suite of industrial and organizational (I-O) psychologists, given the expected increase in nonroutine and interactive tasks in the new workplace. At the same time, they promote new ways of assessing these skills using computer-based microworlds, enabling the systematic variation of problem features in assessment. Neubert and colleagues’ (2015) suggestions are a valuable step in connecting differential psychologists’ models of human differences and functioning with human resources professionals’ interest in understanding and predicting behavior at work. We concur that CPS and ColPS are important transversal skills, useful for I-O psychologists, but these are only two babies of a single family, and the domain of 21st century skills includes other families of a different kind that are also with utility for I-O psychologists. The current contribution is meant to broaden this interesting discussion in two important ways. We clarify that CPS and ColPS need to be considered in the context of a wider set of 21st century skills with an origin in the education domain, and we highlight a number of crucial steps that still need to be taken before “getting started” (Neubert et al., 2015, p. last page of the discussion) with this taxonomic framework. But first, we feel the need to slightly reframe the relevance of considering 21st century skills in I-O psychology by shifting the attention from narrow task-related skills to the broader domain of career management competencies.
In the presence of such a powerhouse lineup of Asianists I think I will tiptoe off to the other end of Lieberman's Eurasia and presume on my unique qualifications in this company as having published over twenty pages for the general reader on the France of Louis XIV and fifteen on the Russia of Peter the Great. Also, I have a bee in my bonnet at the moment about how the world changed between 1770 and 1830, and will have most to say about what Lieberman offers on that period. I owe Jerry Bentley a review article on all this for the Journal of World History, because he got me a review copy of the large work of Jürgen Osterhammel, Die Verwandlung der Welt: Eine Geschichte des 19. Jahrhunderts. I also got hooked by listening in on a fine conference at the Clark Library in Los Angeles in 2008, which led to The Age of Revolutions in Global Context, edited by David Armitage and Sanjay Subrahmanyam. A less recent book which I think is an under-appreciated breakthrough for this effort is Chris Bayly's Imperial Meridian: The British Empire and the World, 1780–1830.
We have used the ab-initio full potential LMTO method to model native defects and chlorine-impurity-related defects in ZnSe and ZnxMg1−xSe. Our results show that there is a strong tendency for formation of a defect complex between a chlorine impurity at the Se site and a vacancy at the neighboring Zn site. The formation energies of this complex and other chlorine related defects decrease in the presence of magnesium. However, the maximum achievable electron concentration in the presence of magnesium is lower because of the increase in the band gap.
We illustrate how emerging methods in artificial intelligence (AI) may be useful in materials science. Historically, these methods were developed in the area of materials process control and, more recently, in the nascent field of materials discovery. However, machine intelligence is of much broader import and our primary objective here is to illustrate how such methods may be used to circumvent some serious roadblocks in the computer simulation of a significant class of computationally hard problems in materials science. This is illustrated by a new approach to solving the dynamics of the N-body problem for large numbers of objects of essentially arbitrarily complex geometry or interaction potential. The approach, based on a particulate artificial neural net dynamics algorithm (PANNDA) is more than two orders of magnitude faster than existing methods when applied to large systems and is only marginally slower (∼10%) than the theoretical lower limiting case of hard spheres. In this method an artificial neural net is trained to predict accurately the time to next collision for binary encounters spanning the Hilbert space of relative positions, orientations and momenta (linear and angular). This approach, which can be extended to soft complex systems, enables construction of exact, albeit numerical, models for the thermodynamic, transport and non-equilibrium properties of very large ensembles of hard or soft objects of arbitrarily complex shape or interaction potential. Our results open up the possibility of immediate application to an usually wide spectrum of contemporary computationally intractable “hard” problems ranging from granular materials with asperities through inclusion of complex many-body terms in the intermolecular interaction in molecular dynamics calculations of complex fluids and polymers.
The electronic structure of Pu materials is examined using photoelectron spectroscopy. For delta-phase Pu metal as well as PuCoGa5 and PuIn3, the 5f electrons appear to be at the threshold between localized and itinerant character. A mixed level model computational scheme is used which results in non-magnetic solutions for the electronic structure and agrees well with the photoemission measurements. Several other computational schemes are assessed against photoemission results for delta Pu. Additional insight is provided by O2 and H2 dosing of the delta Pu samples and consideration of surface effects. The experimental and computational results are consistent with the 5f electrons in Pu materials exhibiting a dual nature with some fraction of the 5f levels localized and not participating in the bonding while the other fraction of 5f character is involved in bonding and hybridization with the conduction electrons.
The 5f electronic states in elemental Pu and Pu compounds exhibit elements of both itinerant and localized behavior. Several first-principles calculations have been presented to describe this balance, differing in the manner in which electron correlation is included in the calculation. This paper describes a calculations performed with the Mixed Level Model (MLM), presenting calculated results for the two Pu compounds, PuRhGa5 and PuCoGa5. The MLM results are compared with other calculations and the differences discussed.
The stability of bcc-based phases in the Ti-Al-Nb alloy system has been studied from first-principles using a combination of ab-initio total energy and cluster variation method (CVM) calculations. Total energies have been computed for 18 binary and ternary bcc superstructures in order to determine low temperature ordering tendencies. From the results of these calculations a set of effective cluster interaction parameters have been derived. These interaction parameters are required input for CVM computations of alloy thermodynamic properties. The CVM has been used to study the effect of composition on finite-temperature ordering tendencies and site preferences for bcc-based phases. Strong ordering tendencies are observed for binary Nb-Al and Ti-Al bcc phases as well as for ternary alloys with compositions near Ti2AlNb. For selected superstructures we have also analyzed structural stabilities with respect to tetragonal distortions which transform the bcc into an fcc lattice. Instabilities with respect to such distortions are found to exist for binary but not ternary bcc compounds.
The single-crystal elastic constants of C15 NbCr2 have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropie elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson's ratio and the direction dependence of Young's modulus.