1,720,987 research outputs found
Waveguide-enhanced scattering from thin biomolecular films
Full text linkAn X-ray diffraction experiment on multilamellar membranes incorporated into an X-ray waveguide structure is reported. In the device, the lipid bilayers are confined to one side by the silicon substrate and to the other side by an evaporated thin metal cap layer. Shining a highly brilliant X-ray beam onto the system, resonantly enhanced, precisely defined and clearly distinguishable standing-wavefield distributions (modes) are excited. The in-plane structure of the acyl chain ordering is then studied by grazing incidence diffraction under simultaneously excited modes. A significant gain in signal-to-noise ratio as well as enhanced spatial resolution can be obtained with such a setup
Two-dimensional x-ray waveguides and point sources
No full textWe show that resonant coupling of synchrotron beams into suitable nanostructures can be used for the generation of coherent x-ray point sources. A two-dimensionally con ning x-ray waveguide structure has been fabricated by e-beam lithography. By shining a parallel undulator beam onto the structure, a discrete set of resonant modes can be excited in the dielectric cavity, depending on the two orthogonal coupling angles between the beam and the waveguide interfaces. The resonant excitation of the modes is evidenced from the characteristic set of coupling angles as well as the observed far-field pattern. The x-ray nanostructure may be used as coherent x-ray point sources with a beam cross section in the nanometer range
Biased information processing in the escalation paradigm: Information search and information evaluation as potential mediators of escalating commitment.
No full textEscalation of commitment denotes decision makers' increased reinvestment of resources in a losing course of action. Despite the relevance of this topic, little is known about how information is processed in escalation situations, that is, whether decision makers who receive negative outcome feedback on their initial decision search for and/or process information biasedly and whether these biases contribute to escalating commitment. Contrary to a widely cited study by E. J. Conlon and J. M. Parks (1987), in 3 experiments, the authors found that biases do not occur on the level of information search. Neither in a direct replication and extension of the original study with largely increased test power (Experiment 1) nor under methodologically improved conditions (Experiments 2 and 3) did decision makers responsible for failure differ from nonresponsible decision makers with regards to information search, and no selective search for information supporting the initial decision or voting for further reinvestment was observed. However, Experiments 3 and 4 show that the evaluation of the previously sought information is biased among participants who were responsible for initiating the course of action. Mediation analyses show that this evaluation bias in favor of reinvestment partially mediated the responsibility effect on escalation of commitment
Listing and Structuring of Discussion Content
No full textGroups often fail to solve so-called "hidden profiles." Common explanations for this failure focus on group processes. However, recent findings show that group members stick to their individual faulty preferences even in the absence of such group processes. The present study examines whether listing and structuring of discussion content improves individual decision quality in hidden profile tasks. We found that the probability of detecting the best and the worst alternative was higher in the experimental conditions where participants listed and structured all information concerning decision alternatives, as compared to a control condition without any listing and structuring. Additional structuring criteria, namely structuring according to valence and novelty of information did not affect solution rates
1D and 2D X-ray waveguides: Optics and applications
No full textX-ray waveguides [1-4] offer a novel approach for nanobeam production, which may become useful in
coherent beam imaging and phase contrast projection microscopy [5]. Internal field enhancement, coherency
properties, and coupling efficiency of these devices have been measured and compared to theoretic predictions. The
fundamentals of x-ray wave guide optics can be derived from a scalar wave equation. Up to now, x-ray waveguide
optics have exclusively been one-dimensional (1D), while many applications demand two-dimensionally (2D) confined
point beams. We have recently demonstrated the first proof of principle that x-ray waveguide effects can be generalized
to 2D devices using e-beam defined lithographic nanostructures [6], delivering of a coherent hard x-ray beam with
nanometer sized cross-section (69 nm 33 nm)
Reflection of waveguided X-rays in two-dimensional nanostructures
Full text linkThe internal reflection of an excited X-ray waveguide mode in a synthetic nanostructure, defined by electron-beam lithography, has been measured. In this device, the X-ray beam is first coupled into a conventional vertical thin-film waveguide structure and then reflected laterally at the quasi-one-dimensional edge of the waveguiding layer. The reflectivity of the quasi-one-dimensional interface has been recorded under simultaneous excitation of the (vertical) waveguide mode. The experiment constitutes an important step towards the production of a coherent nanometre-sized X-ray point source by two-dimensionally defined waveguide structures.</jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
White beam x-ray waveguide optics
No full textWe report a white beam x-ray waveguide (WG) experiment. A resonant beam coupler x-ray waveguide (RBC) is used simultaneously as a broad bandpass (or multibandpass) monochromator and as a beam compressor. We show that, depending on the geometrical properties of the WG, the exiting beam consists of a defined number of wavelengths which can be shifted by changing the angle of incidence of the white x-ray synchrotron beam. The characteristic far-field pattern is recorded as a function of exit angle and energy. This x-ray optical setup may be used to enhance the intensity of coherent x-ray WG beams since the full energetic acceptance of the WG mode is transmitted. (C) 2004 American Institute of Physics
Der Einfluss einer uneindeutigen Informationslage auf eskalierendes Commitment
No full textDie Forschung zu eskalierendem Commitment beschäftigt sich mit der Frage, warum Personen an Handlungen bei fraglichem Handlungserfolg festhalten. Eine wesentliche Moderatorvariable eskalierenden Commitments formulierte Bowen (1987) mit der decision dilemma theory, derzufolge eskalierendes Commitment insbesondere dann stattfindet, wenn Informationen bezüglich des fraglichen Handlungserfolgs uneindeutig sind. Die bisherigen Studien zur decision dilemma theory stehen zum Teil für Alternativerklärungen offen und/oder weisen methodische Mängel auf. Die vorliegende Untersuchung stellt einen direkten Test der Theorie dar. Die Probanden sollten in einer Wirtschaftsfallsimulation eine Entscheidung über Folgeinvestitionen in eine Verluste schreibende Abteilung eines Unternehmens treffen. Zuvor waren die Probanden für eine Förderung dieser Abteilung entweder verantwortlich oder nicht verantwortlich gewesen. Zudem wurde manipuliert, ob sich Expertengutachten, die das Investitionsproblem behandelten, in der Mehrzahl für, gegen oder zu gleichen Anteilen für und gegen eine weitere Investition aussprachen. Wie von der decision dilemma theory vorhergesagt, zeigten die verantwortlichen Probanden insbesondere bei einer ausgeglichenen und somit uneindeutigen Gutachtenlage eskalierendes Commitment. Escalation of commitment is the tendency to hang on to losing courses of action. In his decision dilemma theory, Bowen (1987) specifies a moderator of escalating commitment in that escalation occurs most frequently if feedback concerning the failure of the course of action is equivocal rather than unequivocal. However, previous empirical demonstrations of the decision dilemma theory to some extent are open for alternative explanations or suffer from methodological limitations. The present study provides a direct test of the theory. Participants worked on an economic case study in which they were asked to decide how much to invest further in a division of a company that incurred a loss. In advance, participants had been made responsible or not responsible for the promotion of that division. Furthermore, we manipulated whether expert statements arguing for further investments outnumbered, were equal to, or were outnumbered by expert statements arguing against further investments. As predicted by the decision dilemma theory, responsible participants exhibited escalating commitment particularly when there was an equal number of experts supporting and contradicting further investments, that is, when expert feedback was equivocal.Escalation of commitment is the tendency to hang on to losing courses of action. In his decision dilemma theory, Bowen (1987) specifies a moderator of escalating commitment in that escalation occurs most frequently if feedback concerning the failure of the course of action is equivocal rather than unequivocal. However, previous empirical demonstrations of the decision dilemma theory to some extent are open for alternative explanations or suffer from methodological limitations. The present study provides a direct test of the theory. Participants worked on an economic case study in which they were asked to decide how much to invest further in a division of a company that incurred a loss. In advance, participants had been made responsible or not responsible for the promotion of that division. Furthermore, we manipulated whether expert statements arguing for further investments outnumbered, were equal to, or were outnumbered by expert statements arguing against further investments. As predicted by the decision dilemma theory, responsible participants exhibited escalating commitment particularly when there was an equal number of experts supporting and contradicting further investments, that is, when expert feedback was equivocal
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