1,721,384 research outputs found
Theoretical and Practical Considerations of Spatially Offset Raman Spectroscopy (SORS) and Micro-SORS
No full textSpatially offset Raman spectroscopy (SORS) is typically used to non-invasively investigate stratified samples that possess features on a millimeter scale, whereas micro-SORS usually deals with micrometer-thick layered samples. However, there are many instances where these boundaries are intertwined, sometimes indicating the possibility of using both techniques as well as circumstances that present mutual exclusion to their applicability. The aim of this study is to establish an application protocol that provides better insight into their suitability for deployment in various scenarios. The differences and similarities between the two approaches are investigated highlighting their strengths and limitations considering both theoretical and practical aspects. Diverse available parameters entail prospects and restrictions of both techniques and give rise to specific instrumental effects, namely, the overlap between the collection and excitation areas, the percentage of collected area for a given spatial offset, and the accuracy in the definition of the spatial offset (spread effect). These aspects are studied and exemplified on mockup samples relevant to the field of cultural heritage. The samples are characterized by high compositional complexity comprising features ranging from micrometer to millimeter scales. The conclusions reached are also relevant to other scientific areas such as biomedical, forensic, or energy harvest
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
Non-destructive analysis of concentration profiles in turbid media using micro-spatially offset Raman spectroscopy: A physical model
No full textWe introduce an analytical physical description of micro-spatially offset
Raman spectroscopy (micro-SORS) experiments in turbid samples with a spe-
cial emphasis on its use for studying the penetration depth of chemical species
(agents) into a matrix. Such samples exhibit varying concentration gradients
with depth and reflect typical situations encountered in Cultural Heritage
framework. The experiments aim at yielding the variations (trends) of the
Raman intensity ratio of the agent and matrix marker bands, H Xð Þ, with
increasing micro-SORS defocusing distance Xð Þ. The physical model shows
that H Xð Þ can be expressed as a function of the concentration profiles of the
analytes. The analysis makes use of Monte Carlo simulation results of the
propagation of photons in turbid media. Despite the introduced approxima-
tions, the obtained formulas provide an insightful tool that allows justifying
the observed trends and facilitates the interpretation of micro-SORS data and
systematic comparison among different samples. Basic comparison with
previously published experimental micro-SORS data indicates good consis-
tency. The obtained relationships could also be useful for a semi-quantitative
estimate of concentration profiles in unknown sample
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
Micro-SORS, diffusion processes and heritage science: a non-destructive and systematic investigation
No full textAbstract: In this paper, a systematic investigation is carried out to test micro-SORS capability to non-destructively characterize a system where an agent diffuses into a turbid matrix with potential applications in heritage science and elsewhere. Defocusing micro-SORS experiments were performed on two specially designed sets of samples with controlled characteristics. Three parameters have been considered, namely penetration depth, concentration of the agent and its profile within the matrix. A relative agent/matrix Raman intensity decay rate is observed when the microscope objective is moved away from the sample surface, and the slope of this ratio trend was found to correlate with the penetration depth of the agent involved in the diffusion process. In situations where the concentration profile is known, different penetration depths of the agent can be discriminated from each other using the slope of the normalized agent/matrix Raman intensity decay rate. This outcome opens prospects for non-destructively monitoring the efficacy of conservation treatments, based on the penetration depth of the products as well as it provides an analytical tool for other applications where the penetration of an agent into a diffusely scattering matrix is involved such as drug perfusion through skin, pharmaceutical tablet dissolution process and numerous others. Graphic abstract: [Figure not available: see fulltext.]
Non-invasive andin situinvestigation of layers sequence in panel paintings by portable micro-spatially offset Raman spectroscopy
No full textNowadays, the research in conservation science is focused on developing advanced portable analytical techniques able to achieve subsurface data in situ and in a non-invasive way. Micro-spatially offset Raman spectroscopy (micro-SORS) is an emerging analytical technique developed to address the need of non-invasively retrieving the molecular composition of the subsurface compounds; however, so far, micro-SORS studies of artworks have been carried out only with benchtop Raman microscopes, precluding the non-invasive analysis of large objects and artworks in situ. Here, for the first time, portable micro-SORS was used for non-invasive and in situ investigation of art objects. The potential of portable micro-SORS is demonstrated through the reconstruction of the layer sequences in selected areas of two 16th century panel paintings, providing unequivocal information about the preparation layer spread over the panels and the pigments used in the painted layers and supplying essential information on the artist's technique
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