1,720,981 research outputs found
Chemometrics tools for Advanced Spectroscopic Analyses
Full text linkAny system is described by several variables, often in the form of hidden information, able to describe and explain functional mechanisms for the majority of the processes which can be evaluated analytically only when we consider entire complex datasets. The relationship between those variables is the key to identify and quantify correlations among the parameters describing the data in a strictly model-free manner. In chemometrics one uses mathematical and statistical methods to improve the understanding of chemical information through the correlation of physical parameters or properties to analytical instrument data. This approach is currently used across chemistry, materials science, biology, with a growing impact is the field of spectroscopy. This paper presents the ability of chemometric technique applied to Advanced Spectroscopic Analyses, examples include spectroscopic data collected from both the High- resolution neutron Spectrometer TOSCA, operating at the ISIS pulsed Neutron and Muon Source (UK) and X-ray fluorescence (XRF) spectroscopy. This work demonstrates the high-resolution of the Principal Component Analysis (PCA) to a spectroscopic data-set dealing with the determination of marker bands from Inelastic Neutron Scattering (INS) spectra of a large data- set, the presence of a probably additional transition phase of one globular molecule and evidencing the metallic nature of the black/brownish inscriptions on daily-use textiles used in ancient Egypt. This study will pave the way for the analysis of multi-parametric, high-throughput INS data, now within reach using state-of-the-art chemical neutron spectrometers such as VESPA
Neutron sensing at spallation neutron sources by SERS
No full textNeutron detectors are paramount in many applications from medical science to homeland security and aerospace. A miniaturized solid-state device based on a nanostructured-gold thin film grown by pulsed laser ablation under deposition-controlled conditions and functionalized with a monolayer of 4-mercaptophenyboronic acid (4-MPBA) was fabricated as a neutron dose detector. The device is tested with slow neutron detection in the thermal and epithermal energy range at ISIS spallation neutron source (UK). After the neutron irradiation, 4-MPBA is converted into thiophenol (TP), and the chemical modification is monitored by the intensity of related vibrational bands at 1586 cm−1 (4-MPBA) and 1574 cm−1 (TP). The latter are used as a vibrational signature of the absorbed dose by surface-enhanced Raman spectroscopy (SERS). The conversion of 4-MPBA to TP is due to the loss of the boron-containing group after the absorption of a slow neutron by 10B isotope. The I1574/I1586 ratio is used to estimate the ratio of 10B nuclei absorption reactions due to the thermal and epithermal contributions and it is proposed for the development of neutron dosimetry for nuclear medicine, aerospace, and security applications
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
A non-invasive spectroscopic study to evaluate both technological features and conservation state of two types of ancient Roman coloured bricks
No full textThe study of both original and decaying compounds is relevant in understanding the chemistry behind the deterioration processes, above all in open museum contexts where environmental stressors affect the artefacts. In this sense, a combination of non-invasive spectroscopy techniques (Raman spectroscopy, μ-X-ray fluorescence and X-ray diffraction) was applied on an ancient Roman building (130 CE), the “Casa di Diana” Mithraeum at Ostia Antica archaeological site. The aim is to study the raw materials, manufacturing and decaying products of the two observed types of Roman fired bricks (red and yellow) that compose the building.
The present study estimates an illite raw material of carbonate-bearing marine clay likely referring to the common deposits of central/southern Italy, which contain calcite as accessory phase and a-plastic fraction constituted by quartz, feldspar and opaques. This clay material was added with volcanic temper characterised by abundant clinopyroxene and analcime (from analcimization of leucite) that are typical of the Roman Province volcanism. The firing would be probably the result of oxidizing conditions, as proved by the hematite presence. Thanks to the existence of specific neoformed mineral phases during firing it was possible to assess different temperatures ranges. In detail, the red/orange bricks, for the existence of gehlenite (formed from calcite and its reaction with silicates), were fired at 800–900 °C range; whereas, the yellow ones are characterised by the lack of gehlenite and the disappearance of illite/muscovite, which indicates firing temperature at over 900 °C.
Regarding the decaying products, the gypsum covers most of the surface of most bricks, both red and the yellow ones, but these latter are more susceptible to environmental stressors (sulphates and carbonates).
Therefore, this work points out how by integrated non-invasive approaches it is possible trace back to original firing temperature, technology of manufacture, interpreting ceramic data
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
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
A Python Algorithm to Analyze Inelastic Neutron Scattering Spectra Based on the y-Scale Formalism
Full text linkThis paper presents a Python-based algorithm, named INSCorNorm, to correct the inelastic neutron scattering (INS) spectra for both sample and container self-shielding and to normalize the experimental spectral intensity to an absolute physical scale (barn/energy unit) facilitating the comparison with computer simulations and interpretation. The algorithm is benchmarked against INS measurements of ZrH, performed on the TOSCA spectrometer at the ISIS Facility. We also apply the algorithm to the INS spectra from L-lysine, a system of broad interest in biology and medicine, and we discuss how corrected INS data provide an experimental benchmark for theoretical calculations of nuclear anisotropic displacement parameters in molecular systems. The total neutron sample cross section to use for the self-shielding corrections is discussed, as well as the best approach to derive experimentally the cross section at the VESUVIO spectrometer, together with the experimental value of the hydrogen nuclear mean kinetic energy, (E-k). The algorithm is made available to the neutron user community within the MANTID software
Neutrons for Cultural Heritage—Techniques, Sensors, and Detection
Full text linkAdvances in research in Cultural Heritage see increasing application of a multidisciplinary approach and the combined use of physical and chemical characterization of artefacts that can be used to define their structure and their state of conservation, also providing valuable information in selecting the most suitable microclimatic conditions for the exhibition environment. This approach provides a platform for a synergic collaboration amongst researchers, restorers, conservators, and archaeologists. Existing state-of-the-art technologies for neutron-based methods are currently being applied to the study of objects of historical and cultural interest in several neutron-beam facilities around the world. Such techniques are non-invasive and non-destructive and are, therefore, ideal to provide structural information about artefacts, such as their composition, presence of alterations due to the environmental conditions, inclusions, structure of the bulk, manufacturing techniques, and elemental composition, which provide an overall fingerprint of the object's characteristics, thanks to the nature of the interaction of neutrons with matter. Here, we present an overview of the main neutron methods for the characterization of materials of interest in Cultural Heritage and we provide a brief introduction to the sensors and detectors that are used in this framework. We conclude with some case studies underlining the impact of these applications in different archaeological and historical contexts
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
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