1,721,341 research outputs found
UA9 -CERN
No full textThe UA9 collaboration is investigating how tiny bent crystals could improve how beams are collimated in modern hadron colliders such as the LHC.
The planes in crystalline solids can constrain the directions that charged particles take as they pass through. Physicists can use this "channelling" property of crystals to steer particle beams. In a bent crystal, for example, channelled particles follow the bend and can change their direction.
In high-energy hadron colliders, particles surrounding the beam core can be lost, damaging sensitive areas of the accelerator. Multi-stage collimation systems are usually used to absorb this beam halo. These systems are composed of massive collimators and absorbers very close to the beam. Using a tiny bent crystal as a primary collimator could deflect halo particles coherently at large angles and direct them into a secondary collimator-absorber. In this way, the massive collimator-absorber could be placed at an increased distance from the beam, reducing the complexity of the system.
The UA9 collaboration has been testing this idea since 2009, using beams from the Super Proton Synchrotron to do experiments on the collimation efficiency of silicon crystals
PEARL - ERC
No full textThe PEARL project aims at advancing the technologies for manufacturing of high quality Periodically Bent Crystals (PBCr). The PBCr developed in the course of this project will be utilised for the con-struction of novel light sources of high-energy (hν≥102 keV up to GeV range) monochromatic elec-tromagnetic radiation by means of a Crystalline Undulator (CU). The technological and experi-mental part of this project will be accompanied by the complimentary advanced theoretical research utilising modern theoretical, computational and modelling methods accomplished with high perfor-mance computing techniques. A broad interdisciplinary, international collaboration has been created in the frame of FP7 PIRSES-CUTE project, which was focused on initial experimental tests of the CU idea and the related theory, for review see. This project has been successfully completed in March 2015 and left the matter experimentally validated to a degree that is tantalising, requiring further exper-imentation. In particular CUTE elucidated the demand on manufacturing PBCrs of an exceptional lat-tice quality, their experimental characterisation and exposure against the high quality beams of ultra-relativistic electrons and positrons for the observation of the strong coherent effects in the photon emission process. PEARL will focus on solving the whole complex of the important technological, ex-perimental and theoretical problems aiming to achieve the major breakthrough in this important re-search area. The PEARL international collaboration is extended with respect to CUTE and involves the new partners with the essential, necessary, complementary expertise and experimental facilities. The PEARL research programme is highly collaborative and requiring numerous exchange visits between the involved laboratories, joint workshops and conferences. Therefore, RISE type of project is the most suitable for strengthening of this very essential, ongoing, international collaborative research
Sugli stemmi bipartiti. Decimazione, asimmetria e calcolo delle probabilita
No full textL’art. propone una soluzione (avvalendosi della collaborazione del fisico
nucleare Vincenzo Guidi) per il cosiddetto “paradosso di Bédier” (1928),
cioè l’assoluta prevalenza degli stemmi bipartiti. Si tratta di un problema
considerato finora pressoché insolubile che caratterizza il paradigma del
metodo filologico degli errori comuni. In primo luogo si ripercorrono le
tesi di Bédier notando che lo studioso confonde gli stemmi (i diagrammi che
rappresentano i mss. superstiti) con gli alberi reali (l’insieme di tutti i
mss. di una tradizione, compresi quelli perduti. In secondo luogo si nota
che nelle tradizioni a stampa quattro-cinquecentesche (caratterizzate da una
decimazione 300 volte meno intensa; 300 è la tiratura minima di un’edizione
del tempo) gli alberi pluripartiti non sono così rari. Si spiega quindi il
paradosso ragionando sull’asimmetria che caratterizza di regola le
tradizioni manoscritte combinata con gli effetti di una elevata decimazione
(dal 70% al 100%)
AXIAL - INFN
No full textStudio di effetti coerenti orientazionali di particelle ultrarelativistiche in modalità assiale condotta presso il Super Proton Synchrotron del CER
On a diffusion problem arising in nanophased thin films
No full textThe selective-sublimation processing is a technique for deposition
of nanosized thin films aimed at controlling the composition of the film and hence
its properties. The method consists of the deposition of a
solid solution of a mixed-metal oxide with the sublimation
temperature of one of the pure metal oxide being rather low.
Proper thermal treatment allows to selectively sublimate the most
volatile metal oxide.
In this paper we first model the thermal processing undergone by
the films under the assumption that the thickness of the layer is
constant. The problem is formalized as an initial-boundary value
problem for a one-dimensional diffusion equation with fixed
boundary. We construct an explicit solution for the problem
relying on a set of observable physical quantities that can be
profitably used in experiments, i.e., the sublimation rate of the
most volatile oxide and the diffusion coefficient. Conversely, we
discuss the problem of determining such coefficients from an
additional measurement and provide error estimates.
Finally, we propose a more general model taking into account the
thinning of the film due to sublimation. It results in a
free-boundary value problem at the sublimation surface of the
film, which is solved by successive approximations
Ti-W-O sputtered thin films as n or p type gas sensors
No full textWe present some recent trends about research on gas sensors based on semiconducting thin films together with, a discussion on the development of novel nanostructured materials such as TiO, TiO2, and WO3 in single phase or as mixed oxides. The films, deposited by RF reactive sputtering from a composite target of W and Ti at two different abundances, are investigated through scanning and transmission electron microscopy (SEM and TEM) techniques for structural characterisation and by volt-amperometric technique for electrical and gas-sensing properties. All of the layers were capable to sense NO2, no effect of poisoning of the surface was recorded, and recovery of the resistance was complete. A concentration as low as 0.5 ppm was detected with a relative change in the resistance Delta R/R about 1400% and as short a response time as 2 min. A detection limit lower than 100 ppb of NO2 is expected. (C) 2000 Elsevier Science B.V. All rights reserved
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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