747 research outputs found
Chiral Metal Surfaces and Nanoparticles
The surface of metals can exhibit intrinsic chiral structure. Furthermore, chirality can be bestowed onto achiral metal surfaces by adsorption of chiral molecules. Such chiral metal surfaces are promising as heterogeneous enantioselective catalysts and may furthermore be used for the
separation and detection of enantiomers. Similarly, metal nanoparticles can be chiral, which is reflected by their optical activity in metal-based electronic transitions. The transfer of chirality from adsorbate to the metal surface depends on the structure of the former, which is however
difficult to elucidate. It is shown that vibrational circular dichroism can be used to determine the structure of a chiral adsorbed molecule and the way it interacts with the metal
On the suitability of longitudinal profile measurements using Coherent Smith-Purcell radiation for high current proton beams
The use of Smith-Purcell radiation to measure electrons longitudinal profiles
has been demonstrated at several facilities in the picosecond and
sub-picosecond range. There is a strong interest for the development of non
intercepting longitudinal profile diagnostics for high current proton beams. We
present here results of simulations on the expected yield of longitudinal
profile monitors using Smith-Purcell radiation for such proton beams.Comment: Presented at IPAC 2014 - THPME08
Explaining Scientific Collaboration: a General Functional Account
For two centuries, collaborative research has become increasingly widespread. Various explanations of this trend have been proposed. Here, we offer a novel functional explanation of it. It differs from ac- counts like that of Wray (2002) by the precise socio-epistemic mech- anism that grounds the beneficialness of collaboration. Boyer-Kassem and Imbert (2015) show how minor differences in the step-efficiency of collaborative groups can make them much more successful in particular configurations. We investigate this model further, derive robust social patterns concerning the general successfulness of collaborative groups, and argue that these patterns can be used to defend a general functional account
Scientific Collaboration: Do Two Heads Need to Be More than Twice Better than One?
Epistemic accounts of scientific collaboration usually assume that, one way or another, two heads really are more than twice better than one. We show that this hypothesis is unduly strong. We present a deliberately crude model with unfavorable hypotheses. We show that, even then, when the priority rule is applied, large differences in successfulness can emerge from small differences in efficiency, with sometimes increasing marginal returns. We emphasize that success is sensitive to the structure of competing communities. Our results suggest that purely epistemic explanations of the efficiency of collaborations are less plausible but have much more powerful socioepistemic version
Evaluation of process causes and influences of residual stress on gear distortion
In the automotive industry, heat treatment of components is implicitly related to distortion. This phenomenon is particularly obvious in the case of gears because of their typical and precise geometry. Even if distortion can be anticipated to an extent by experience, it remains complex to comprehend. This paper presents an approach to estimate the distortion based on the idea of a distortion potential taking into account not only geometry but also the manufacturing process history. Then the idea is developed through simulation and experiments including annealing to understand the impact of residual stress on gear distortion in an industrial case study
Existence of a critical layer thickness in PS/PMMA nanolayered films
An experimental study was carried out to investigate the existence of a
critical layer thickness in nanolayer coextrusion, under which no continuous
layer is observed. Polymer films containing thousands of layers of alternating
polymers with individual layer thicknesses below 100 nm have been prepared by
coextrusion through a series of layer multiplying elements. Different films
composed of alternating layers of poly(methyl methacrylate) (PMMA) and
polystyrene (PS) were fabricated with the aim to reach individual layer
thicknesses as small as possible, varying the number of layers, the mass
composition of both components and the final total thickness of the film. Films
were characterized by atomic force microscopy (AFM) and a statistical analysis
was used to determine the distribution in layer thicknesses and the continuity
of layers. For the PS/PMMA nanolayered systems, results point out the existence
of a critical layer thickness around 10 nm, below which the layers break up.
This critical layer thickness is reached regardless of the processing route,
suggesting it might be dependent only on material characteristics but not on
process parameters. We propose this breakup phenomenon is due to small
interfacial perturbations that are amplified by (van der Waals) disjoining
forces
Capturing Smart Contract Design with DCR Graphs
Smart contracts manage blockchain assets. While smart contracts embody
business processes, their platforms are not process-aware. Mainstream smart
contract programming languages such as Solidity do not have explicit notions of
roles, action dependencies, and time. Instead, these concepts are implemented
in program code. This makes it very hard to design and analyze smart contracts.
We argue that DCR graphs are a suitable formalization tool for smart contracts
because they explicitly and visually capture these features. We utilize this
expressiveness to show that many common high-level design patterns in
smart-contract applications can be naturally modeled this way. Applying these
patterns shows that DCR graphs facilitate the development and analysis of
correct and reliable smart contracts by providing a clear and
easy-to-understand specification
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