Effect of pulsed hollow electron-lens operation on the proton beam core in LHC

Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the HL-LHC. In order to further increase the diffusion rates for a fast halo removal as e.g. desired before the squeeze, the electron lens (e-lens) can be operated in pulsed mode. In case of profile imperfections in the electron beam the pulsing of the e-lens induces noise on the proton beam which can, depending on the frequency content and strength, lead to emittance growth. In order to study the sensitivity to the pulsing pattern and the amplitude, a beam study (machine development MD) at the LHC has been proposed for August 2016 and we present in this note the preparatory simulations and estimates

Cross-border mergers and acquisitions and the role of trade costs

Cross-border mergers and acquisitions (M&As) have increased dramatically over the last two decades. This paper analyses the role of trade costs in explaining the increase in both the number and the value of cross-border mergers and acquisitions. In particular, we distinguish horizontal and non-horizontal M&As and investigate whether distance and trade policy barriers affect these two types of mergers differently. We analyse this question using industry data for 23 OECD countries for the period 1990-2001. Our findings suggest that while in the aggregate trade costs affect cross-border merger activity negatively its impact differs importantly across horizontal and non-horizontal mergers. The impact of trade costs is less negative for horizontal mergers, which is consistent with the tariff-jumping argument.mergers and acquisitions, international trade, trade costs, gravity, FDI, Hijzen, G�rg, Manchin

Resonant and random excitations on the proton beam in the Large Hadron Collider for active halo control with pulsed hollow electron lenses

We present the results of numerical simulations and experimental studies about the effects of resonant and random excitations on proton losses, emittances, and beam distributions in the Large Hadron Collider (LHC). In addition to shedding light on complex nonlinear effects, these studies are applied to the design of hollow electron lenses (HEL) for active beam halo control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable amount of energy will be stored in the beam tails. To control and clean the beam halo, the installation of two hollow electron lenses, one per beam, is being considered. In standard electron-lens operation, a proton bunch sees the same electron current at every revolution. Pulsed electron beam operation (i.e., different currents for different turns) is also considered, because it can widen the range of achievable halo removal rates. For an axially symmetric electron beam, only protons in the halo are excited. If a residual field is present at the location of the beam core, these particles are exposed to time-dependent transverse kicks and to noise. We discuss the numerical simulations and the experiments conducted in 2016 and 2017 at injection energy in the LHC. The excitation patterns were generated by the transverse feedback and damping system, which acted as a flexible source of dipole kicks. Proton beam losses, emittances, and transverse distributions were recorded as a function of excitation patterns and strengths. The resonant excitations induced rich dynamical effects and nontrivial changes of the beam distributions, which, to our knowledge, have not previously been observed and studied in this detail. We conclude with a discussion of the tolerable and achievable residual fields and proposals for further studies.Comment: 33 pages, 32 figures, 46 references. Revised manuscript submitted to Phys. Rev. Accel. Beam

Fünf evidenzbasierte Heuristiken für den Einsatz von Video in der universitären Lehrerausbildung

This article provides a research synthesis on the use of video in pre-service teacher education. Common ideas and evidences concerning the use of video in pre-service teacher education are reviewed. Based on the state-of-the-art in using video, five research-based heuristics are derived. Research findings of a number of studies are further used to illustrate the specification of heuristics. Specifically, a set of rules of thumb about when, how, and why to use video is presented to clarify the strengths and limitations of video as a medium to support pre-service teacher learning. (DIPF/Orig.)Der Beitrag liefert eine Forschungssynthese zur Nutzung von Video in der universitären Lehrerausbildung. Die Forschung wird dahingehend zusammengefasst, welche Ideen derzeit verfolgt werden und welche Evidenzen zur Nutzung von Video vorliegen. Basierend auf dem Forschungsstand leiten die Autoren fünf forschungsbasierte Heuristiken zum Einsatz von Video ab. Die Forschungsergebnisse einer Reihe ausgewählter Studien werden genutzt, um die Heuristiken weiter zu spezifizieren. Es werden Erfahrungsregeln vorgestellt, wann, wie und warum Video in der universitären Lehrerbildung eingesetzt werden kann. Die Erfahrungsregeln sollen helfen, Stärken und Schwächen von Video als ein Medium zur Unterstützung des Lernens von Lehramtsstudierenden zu klären. (DIPF/Orig.

Analysis and Classification of Shape-Changing Interfaces for Design and Application-based Research

Shape-changing interfaces are physically tangible, interactive devices, surfaces, or spaces that allow for rich, organic, and novel experiences with computational devices. Over the last 15 years, research has produced functional prototypes over many use applications; reviews have identified themes and possible future directions but have not yet looked at possible design or application-based research. Here, we gather this information together to provide a reference for designers and researchers wishing to build upon existing prototyping work, using synthesis and discussion of existing shape-changing interface reviews and comprehensive analysis and classification of 84 shape-changing interfaces. Eight categories of prototype are identified alongside recommendations for the field

How eye movements improve vision and action – comment on Vickers

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Enhancing and redirecting carbon nanotube photoluminescence by an optical antenna

We observe the angular radiation pattern of single carbon nanotubes' photoluminescence in the back focal plane of a microscope objective and show that the emitting nanotube can be described by a single in-plane point dipole. The near-field interaction between a nanotube and an optical antenna modifies the radiation pattern that is now dominated by the antenna characteristics. We quantify the antenna induced excitation and radiation enhancement and show that the radiative rate enhancement is connected to a directional redistribution of the emission

Using Design Fiction to Inform Shape-Changing Interface Design and Use

Shape-changing interfaces are tangible, physically dynamic devices which enable user-experience beyond 2D screens. Within Human Computer Interaction, researchers are developing these from low-resolution, low-fidelity prototypes, toward a vision of a truly malleable world. The main focus is in producing and testing hardware, and basic user interactions, which leaves the question unanswered: what are shape-changing interfaces good for? In response, we propose the use of design fiction to investigate potential applications for this technology: to create and analyse artifacts relating to future use-scenarios for shape-change. Whilst research within shape-change often proposes future use-cases for prototypes during discussion, they are seldom in a form that presents them as everyday artifacts. Here, we present and discuss a printed game-play instruction manual for a truly high resolution shape-changing game entitled First Hand, which aims to draw parallels between current gaming practices and the tangible nature of shape-changing interfaces