1,721,153 research outputs found
Jahn–Teller coupling to moiré phonons in the continuum model formalism for small-angle twisted bilayer graphene
Get PDFWe show how to include the Jahn–Teller coupling of moiré phonons to the electrons in the continuum model formalism which describes small-angle twisted bilayer graphene. These phonons, which strongly couple to the valley degree of freedom, are able to open gaps at most integer fillings of the four flat bands around the charge neutrality point. Moreover, we derive the full quantum mechanical expression of the electron–phonon Hamiltonian, which may allow accessing phenomena such as the phonon-mediated superconductivity and the dynamical Jahn–Teller effect
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Dismielinizzazione Spinale. Un caso di Spinal Dysmyelination (SDM) in un vitello di razza Bruna Italiana
No full textGli autori presentano un caso di Dismielinizzazione Spinale (Spinal Dysmyelination, SDM) in un vitello di razza Bruna. Il soggetto, femmina, di cinque giorni di età era stato sottoposto a visita per l’incapacità, sin dalla nascita, di assumere la stazione quadrupedale.
Clinicamente il paziente mostrava tetraparesi spastica caratterizzata da decubito laterale, opistotono, iperestensione degli arti posteriori ed esagerata risposta al riflesso flessorio. Lo stato mentale e le grandi funzioni organiche erano fisiologiche.
Gli esami emato-biochimici routinari, lo studio elettromiografico e le indagini radiografiche della colonna vertebrale, in bianco e con contrasto, non evidenziavano alcunché di significativo ai fini diagnostici.
Parimenti negativo l’esame anatomo-patologico.
Il quadro isto-patologico mostrava evidenti alterazioni della sostanza grigia del midollo spinale caratterizzate da ipomielinizzazione e dismielinizzazione bilaterale simmetrica del fascicolo gracile, del tratto solco-marginale e del tratto spino-cerebellare.
Questo quadro, associato alla presenza, nell’albero genealogico del paziente, di soggetti portatori della SDM sia in linea materna che paterna, costituivano gli elementi conclusivi per includere il caso osservato nella casistica relativa alla rara malattia ereditaria della razza Bruna conosciuta con il nome di Spinal Dysmyelination.
Agli autori non risultano precedenti segnalazioni di questa malattia nella popolazione italiana della razza Bruna
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Note sur le dosage des oxydes de fer par diffraction X
No full textRobert Michel, Pomey G., Angeli M. Note sur le dosage des oxydes de fer par diffraction X. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 83, 7-9, 1960. pp. 226-227
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Valley Jahn-Teller Effect in Twisted Bilayer Graphene
Get PDFThe surprising insulating and superconducting states of narrow-band graphene twisted bilayers have been mostly discussed so far in terms of strong electron correlation, with little or no attention to phonons and electron-phonon effects. We found that, among the 33 492 phonons of a fully relaxed θ=1.08° twisted bilayer, there are few special, hard, and nearly dispersionless modes that resemble global vibrations of the moiré supercell, as if it were a single, ultralarge molecule. One of them, doubly degenerate at Γ with symmetry A1+B1, couples very strongly with the valley degrees of freedom, also doubly degenerate, realizing a so-called EâŠ-e Jahn-Teller (JT) coupling. The JT coupling lifts very efficiently all degeneracies which arise from the valley symmetry, and may lead, for an average atomic displacement as small as 0.5 m Å, to an insulating state at charge neutrality. This insulator possesses a nontrivial topology testified by the odd winding of the Wilson loop. In addition, freezing the same phonon at a zone boundary point brings about insulating states at most integer occupancies of the four ultraflat electronic bands. Following that line, we further study the properties of the superconducting state that might be stabilized by these modes. Since the JT coupling modulates the hopping between AB and BA stacked regions, pairing occurs in the spin-singlet Cooper channel at the inter-(AB-BA) scale, which may condense a superconducting order parameter in the extended s-wave and/or d±id-wave symmetry
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