1,721,041 research outputs found
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
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
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
Trapping ultracold atoms in time-averaged adiabatic potentials
Get PDFThis thesis describes the trapping and manipulation of ultracold atoms in time-averaged adiabatic potentials (TAAP). The time-averaged adiabatic potential, proposed in [Phys. Rev. Lett. 99, 083001 (2007)], uses resonant radio frequency (rf) radiation to couple the different magnetic substates of a hyperfine level manifold. The resultant dressed states are time-averaged and produce smooth and versatile trapping geometries. More specifically, we apply rf-radiation (MHz) to a quadrupole magnetic field, which results in an ellipsoidal trapping potential for rubidium-87 atoms in the F=1 manifold. This geometry is time-averaged with the help of oscillating (kHz) Helmholtz fields.We develop a convenient loading scheme for the TAAP which uses a standard TOP trap and suffers negligible atom losses and heating. Subsequently we characterize the TAAP trap itself and observe low heating rates and sufficient lifetimes (>3s). Furthermore it is possible to use a second, weaker rf-field to evaporatively cool the atoms to quantum degeneracy [Phys. Rev. A. 81, 031402 (2010)]. This opens up a route for further experiments in this potential: we show how atoms can be trapped in a double well potential and a ring trap geometry. Additionally a process to instigate rotation in these potentials by rotating the polarization of the rf-radiation is developed and implemented. This allows us to impart angular momentum onto the atomic cloud and spin it into a ring
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
Towards an imaging lattice for magnetically trapped atoms
Get PDFThe imaging of neutral atoms confined in an optical lattice has been demonstrated by a number of groups, resolving single fluorescing atoms in samples of hundreds of atoms. To obtain a high signal the atoms remain confined in the wells of a deep optical lattice whilst fluorescence excitation light is applied for high resolution imaging. In most cases, the excitation light frequency is chosen so that there is a concomitant laser cooling effect. In existing implementations of an imaging lattice the preceding manipulation stage has used optical trapping and manipulation. In this thesis I describe work towards applying this imaging lattice technique on a magnetic trapping apparatus, in particular for carrying out quantum simulation experiments. An introduction to the specific challenge of performing a quantum simulation of the fractional quantum Hall effect is given, with the link to and nature of the imaging lattice technique explained. The existing quantum-gas machine that has been developed to produce Bose-Einstein condensates of 87Rb in this work is then described, including the new optical lattice subsystem and the associated diode laser system. An auxiliary project to develop a servo-control system for frequencies that are several GHz away from an atomic reference is presented. We implement an optical lattice using laser light with a frequency detuning of -20 GHz below the D1-resonance line. The construction and geometry of the individual dipole trapping beams in combination with our existing apparatus is discussed as well as the alignment methods used. We confirm the presence of three independent 1D lattices through diffraction, and observe the decay of a BEC loaded into a lattice using absorption imaging. We observe good long-term alignment and operational stability of the optical lattice. This system will enable us to ultimately detect single fluorescing atoms in the optical lattice, following the application of excitation light co-propogating with lattice beams, via an imaging system with a moderate numerical aperture of 0:27
Periodically driven atomic systems
Get PDFThis thesis is concerned with a variety of topics grouped together under the general theme of periodically driven atomic systems. Periodic driving is ubiquitous in most techniques used in atomic physics, be it laser cooling, ion trapping or AC magnetic fields. An in-depth understanding of the behaviour of such systems can be provided through Floquet theory which will develop as a central theme in the following chapters. The thesis is divided in two parts: neutral atoms, and ions and biomolecules. In the first part I discuss a new 41K-87Rb mixture experiment, built during the first year of my DPhil. This species combination has some very broad and low-loss interspecies Feshbach resonances that are instrumental for carrying out the experiments discussed in the first chapter. Unfortunately, the mixture experiment had to be put aside and our attention was shifted to Time-Averaged Adiabatic Potentials (TAAPs) and how these can be extended using multiple Radio-Frequency (RF) fields. This technique opens up the way for precise interferometric measurements. Lastly, the peculiar behaviour of Modulation Transfer Spectroscopy (MTS) of 39K is investigated and a linearising transformation for four-wave mixing processes is presented. In the second part we turn our attention to charged ions and biomolecules and the techniques of ion trapping. We propose a novel technique for co-trapping charged particles with vastly different mass-to-charge ratios and thoroughly explore its consequences. The behaviour of the trap and the stability of equations with periodic coefficients in general is studied using Floquet theory. The normal modes and symmetries of the system also need to be considered in relation to the effectiveness of the sympathetic cooling of the ions. Small systems were simulated using a Molecular Dynamics (MD) approach in order to capture the effect of micromotion and other heating processes
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