1,720,960 research outputs found
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
Enhanced plasmonic properties of gold-catalysed semiconductor nanowires
No full textA key challenge for the development of plasmonic nanodevices is their integration into active semiconducting structures. Gold-catalysed semiconductor nanowires are promising candidates for their bottom-up growth process that aligns a single gold nanoparticle at each nanowire apex. Unfortunately these show extremely poor plasmonic properties. In this work, we propose a way to enhance their plasmonic resonance up to those of ideal and isolated gold nanoparticles. A suitable purification protocol compatible with GaAs and ZnSe molecular beam epitaxy of nanowires is used to produce plasmonic active nanowires, which were used to enhance the Raman signal of pentacene and graphene oxide. Enhancement factors up to three orders of magnitude are demonstrated
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Design and realization of nanoelectromechanical and plasmonic devices for Raman spectro-microscopy
No full text2012/2013Lo sviluppo di nano-dispositivi per la misura di molecule biologiche e non biologiche è uno
dei campi più importanti e in via di sviluppo della nanotecnologia. La possibilità di studiare
cellule in vivo e di capirne le caratteristiche a livello molevolare ha contribuito enormemente
all'avanzamento degli studi biologici negli ultimi decenni.
Fra le tecniche più utilizzate, le Scanning Probe Microscopies (SPM) hanno una speciale
rilevanza: sono non distruttive, con una bassa perturbazione dei sistemi studiati e permettono
misure in aria e in liquido. Tali tecniche tuttavia non permettono il riconoscimento chimico,
aspetto importante nello spiegare molti meccanismi cellulari.
Una delle spettroscopie più utilizzate a tale scopo è il Raman, che permette il riconoscimento
delle specie chimiche senza danneggiare i campioni ed è stato ampiamente utilizzato in molti
studi biologici.
Una combinazione di una tecnica SPM e della spettroscopia Raman è il Tip Enhanced Raman
Spectroscopy (TERS): la stessa punta è usata per ricostruire le proprietà meccaniche e per
illuminare localmente il campione per estrarne informazioni chimiche. Tale combinazione
rende il TERS uno strumento molto potente per lo studio di strutture nanometriche.
In questo lavoro di tesi abbiamo esplorato la possibilità di realizzare una punta TERS basata
su un nanofilo in materiale semiconduttore cresciuto epitassialmente sulla punta di un
cantilever per AFM. Il dispositivo, compatibile con le strumentazioni AFM disponibili sul
mercato, ha come scopo lo sfruttamento della risonanza plasmonica creata nella particella
metallica presente sulla cima del nanofilo: il segnale Raman può essere potenziato sfruttando
il campo elettrico molto intenso creato in questo modo.
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910 | Abstract
Nel primo capitolo si introduce le basi della tecnica AFM e vengono presentati due studi
compiuti su cellule mesoteliali tramite questa microscopia.
Nel secondo capitolo vengono presentati i nanofili in silicio: sono riportati i risultati ottenuti
nella crescita di tali strutture, quindi vengono analizzate la citotossicità e la proliferazione di
cellule su substrati di nanofili di silicio.
Misure di microscpettroscopia Raman su nanofili di GaAs sono riportate nel capitolo 3: è
stato studiato il cambiamento di struttura cristallina di tali nanofili dovuta a procedimenti di
riscaldamenti controllati.
Il capitolo 4 affronta lo studio delle proprietà SERS di nanofili di materiali e strutture diverse;
sono presentati risultati sperimentali e calcoli ottenuti tramite simulazioni ad elementi finiti
(FEA).
Infine nel capitolo 5 presentiamo un innovativo procedimento per la fabbricazione di punte
TERS a singolo nanofilo. In Appendice sono presentate brevemente le tecniche fabbricative
usate durante il lavoro di tesi.The development of nano-devices for sensing molecules, both biological and non-biological is
one of the most important and thriving fields of nanotechnology. The possibility to investigate
living cells and their characteristics at a molecular level contributed to the great advance of
biological studies in the last decades.
Among the most investigated techniques, Scanning Probe Microscopies (SPM) have a
prominent position: non-destructiveness, low perturbation of the sample, possibility of
measurements in air and in liquid make them perfectly suited to biological studies. These
techniques however lack chemical recognition of the analysed surfaces. Many cell
mechanisms can be explained only understanding the chemistry involved: the integration of a
spectroscopic technique is therefore essential to have insights on the phenomena under study.
One of the most investigated spectroscopy for such an integration is Raman: its interaction
with molecular and crystal structures allows for chemical recognition. It has been widely used
in studies of organic samples an biosensing and it provides non-destructive measurements.
A smart combination of a SPM technique and Raman Spectroscopy is the so-called Tip
Enhanced Raman Spectroscopy (TERS) where the same probe that is used to reconstruct the
sample mechanical properties with nm resolution is also used to illuminate locally the sample
to extract chemical information. The high resolution spectroscopy combined with the
topography of the SPM makes TERS a powerful tool for the investigation of nanometrical
features. At the present, however, no commercially available TERS probe can provide reliable
and reproducible results with high Raman enhancement.8 | Abstract
With this thesis work we explored the realization of a TERS probe based on a semiconductor
NW grown epitaxially on the apex of an AFM cantilever. This design, compatible with the
commercially available equipment, aims at the use of the plasmonic resonance created in the
noble metal nanoparticle present on the top of the nanowire to greatly enhance the Raman
signal. The high aspect ratio of this nanostructure can lead to high-resolution topography and
spectroscopy.
We will first introduce the basics of SPM and give an example of a study of cells by AFM in
Chapter 1: the effect of the uptake of asbestos fibers and carbon nanotubes by mesothelial
cells is reported.
In Chapter 2 we briefly present the growth mechanics for Si nanowires, with a summary of
the results obtained for Si NWs. A study of the citotoxicity of ZnSe and Si nanowires follows:
living cells were seeded on nanowires and their proliferation, behaviour and adhesion was
measured as a mean to verify the compatibility of NWs with the imaging of living cells.
Chapter 3 reports Raman measurements of GaAs NWs and the change in crystal structure of
these upon annealing at high temperatures.
Studies of the SERS effect on semiconductor nanowires are presented in Chapter 4: the
plasmonic resonance on ZnSe, Si and GaAs NWs was modelled by Finite Element Method.
The absorption spectra and the Raman enhancement factor of the same wires were measured
and an understanding of their SERS capability is presented.
Finally we propose in Chapter 5 a novel fabrication process for the localized growth of NWs
on AFM cantilevers as TERS tips. Appendix A reports a brief explenation of the fabrication
processes mention along the thesis presentation.XXVI Ciclo198
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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