1,720,963 research outputs found
Discrimination of honey according to their sources by micro FT-Raman spectroscopy: a comparison with pollen analysis
No full textApplicazione della chemiometria all'analisi quantitativa delle cere d'api mediante GC e micro-FT-Raman
No full textA new method to quantify paraffin in beeswax based on FT-microRaman spectroscopy and multivariate analysis
No full text
Chemometrics for the Direct Analysis of Solid Samples by Spectroscopic and Chromatographic Techniques
No full textThe direct chemical analysis allows investigating samples without altering them, keeping the sample available for further analysis. For the qualitative investigation, analytical procedures like gas-chromatography, Raman microscopy, and Infra Red spectroscopy are available; however, the univariate approach is not exhaustive in the case of very complex matrices. The quantitative approach is still an open issue, due to the strong matrix effect hindering the creation of univariate calibration methods in interpolation mode. The multivariate analysis may be the solution.
Three-way Principal Components Analysis (PCA) allows for comprehension of variables influencing classification. The Partial Least Squares regression (PLS) combined with Discriminant Analysis (DA) allows classifying. Multivariate standard addition calibration based on PLS coupled with Net Analyte Signal (NAS) calculation allows bypassing the matrix effect in quantitative analysis.
This Chapter is focused on the issues mentioned above. Three sections will be presented:
SECTION 1: three-way PCA is applied to the discrimination among bacterial species in samples analyzed as such by pyrolysis gas chromatography-mass spectrometry. Applications to timely analysis of pathogenic microbes are foreseen.
SECTION 2 PLS-DA is applied to Raman spectra to discriminate adulterated beeswaxes from natural ones. This procedure may be implemented to prevent possible adulteration of bees’ products.
SECTION 3 PLS-NAS is applied to ATR spectra to quantify biogenic silica in marine sediments. The new method allows to accurately study the time evolution of primary productivity in the Antarctic basins
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
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
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