1,720,979 research outputs found
Simulation of an experimental database of infrared spectra of complex gaseous mixtures for detecting specific substances. The case of drug precursors
Get PDFThis work is motivated by the need to develop suitable databases in absence of real experimental data, for instance when spectra measured with a newly developed instrumentation on real samples are not available yet. This notwithstanding, in fact, the realization of the physical project should be addressed by a starting database, also invaluable in order to test its effectiveness. In this article we face the issue of simulating gas mixtures spectra for the development of a new sensor for External Cavity-Quantum Cascade Laser Photoacoustic Spectroscopy (EC-QCLPAS) starting from literature FT-IR spectra of pure components: a dataset is realized suitable to realistically represent the ensemble of spectra of the gas mixtures of interest. The informative data deriving from the literature spectra were combined with the stochastic component extracted from a sample spectrum recorded with a prototype instrument, allowing us to build a matrix containing thousands of simulated spectra of gaseous mixtures, accounting for the presence of different components at different concentrations. Signal processing and experimental design techniques were used along the whole path leading to the dataset of simulated spectra. In particular, the goal of the construction of the database lies in the development of a final system to detect drug precursors in the vapour phase. The comparison of some EC-QCLPAS spectra with the corresponding simulated signals confirms the validity of the proposed approach
Beta diversity and similarity of lichen communities as a sign of the times
No full textAbstractCurrently, change in lichen community structure depends on a combination of several pollutants instead of just one. Consequently, alpha lichen diversity no longer represents an effective response variable for assessing trends in atmospheric pollutants over time. Here we investigated the value of the relationship between alpha diversity and different aspects of gamma diversity (similarity, replacement and differences in richness of species) together with that of beta diversity (calculated as the sum of replacement and difference in richness of species), for assessing complex variations in epiphytic lichen communities in response to a changing pollution scenario. We considered an area subjected to extreme variation in atmospheric pollution in recent decades and explored temporal and spatial aspects of lichen community succession over short-, intermediate- and long-term reference periods. We found that variation in lichen communities for long- and intermediate-term reference periods was strongly dependent on the alpha diversity of single trees at the beginning of the observation period. The occurrence of nitrophytic species, which responded to the decrease in SO2 concentrations, contribute to this trend. The effect of land use was observed only over long observation periods, with trees in urban areas showing less variation than those located in rural areas. In particular, the analysis of similarity, species replacement and differences in richness of tree pairs demonstrated that trends and patterns within lichen communities are neither always nor to the same extent associated with alpha diversity. Our results show that a thorough study of gamma diversity, including beta diversity and similarity, is required to detect changes in air quality in long-term biomonitoring surveys.</jats:p
Using metabolomics to monitor kidney transplantation patients by means of clustering to spot anomalous patient behavior
No full textBackground: NMR spectroscopy-based metabolomics is a system approach used to investigate the metabolic profile of biological fluids with multivariate data analysis tools. The aim of this study was to examine the kidney graft recovery process noninvasively through the examinations of urine samples using 1H NMR spectroscopy combined with chemometric tools. Methods: Urine samples were treated as the source of metabolites reflecting the pathological and clinical conditions of patients with transplanted kidneys. We observed 15 subjects (9 males and 6 females) during the graft recovery process and initial days thereafter. The patients provided at least 9 samples each, applying advanced statistical methods of analysis: Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis PLS-DA). Results: The PCA model (for all subjects exp. var. PC1 13.96% and PC2 9.88%) allowed us to clearly designate 3 stages of recovery: initially the kidney is not working; in the second stage, it regains functions, and the third stage includes follow-up during hospitalization. PCA analysis of a single patient follows graft recovery based on biochemical (metabolites) information, assigning the appropriate recuperation stage. Conclusions: NMR spectroscopy together with chemometric analysis allow monitoring of kidney graft recovery to identify patients who are not progressing within the normal range
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
Identification of a panel of cytokines in neonates with hypoxic ischemic encephalopathy treated with hypothermia
No full textPurpose: Inflammation is a crucial but understudied mechanism of neuronal injury after hypoxia-ischemia. The aim was to identify a panel of cytokines involved in brain injury in neonates with hypoxic ischemic encephalopathy (HIE). Methods: Ten newborns with HIE undergoing to therapeutic hypothermia (TH, HIE Group) and 8 healthy newborns (CTRL Group) were enrolled. For the HIE group, 5 samples were collected: between 0 and 6 h of life (time 1), 12 h (time 2), 24 h (time 3), 48 h (time 4) and 96 h of life (time 5). For the CTRL group, one sample was collected. A panel of 48 inflammatory cytokines was determined in all samples. Data were analyzed using multivariate statistical analysis (Principal component analysis, PCA) Results: 17 cytokines, among 48 analyzed, were found to be significantly different, initially, between the CTRL and HIE groups: 12 with reported pro-inflammatory effects and 5 with reported anti-inflammatory effects. In the HIE group cytokines showed a decreasing trend during the TH and at the end of treatment comparable to the CTRL group. IL-18 did demonstrate a slight increase at time 3 during HT but decreased steadily at sampling times, 4 and 5. Conclusions: Our data demonstrates that many pathways of the inflammatory cascade are activated following hypoxic-ischemic injury. This information will increase our understanding of changes in cytokines over time in neonates with HIE undergoing TH
Experimental design-based strategy for the simulation of complex gaseous mixture spectra to detect drug precursorsOptical Materials and Biomaterials in Security and Defence Systems Technology IX
Get PDFIn the frame of the EU project CUSTOM, a new sensor system for the detection of drug precursors in gaseous samples is being developed, which also includes an External Cavity-Quantum Cascade Laser Photo Acoustic Sensor (ECQCLPAS). In order to define the characteristics of the laser source, the optimal wavenumbers within the most effective 200 cm-1 range in the mid-infrared region must be identified, in order to lead to optimal detection of the drug precursor molecules in presence of interfering species and of variable composition of the surrounding atmosphere. To this aim, based on simulations made with FT-IR spectra taken from literature, a complex multivariate analysis strategy has been developed to select the optimal wavenumbers. Firstly, the synergistic use of Experimental Design and of Signal Processing techniques led to a dataset of 5000 simulated spectra of mixtures of 33 different gases (including the 4 target molecules). After a preselection, devoted to disregard noisy regions due to small interfering molecules, the simulated mixtures were then used to select the optimal wavenumber range, by maximizing the classification efficiency, as estimated by Partial Least Squares – Discriminant Analysis. A moving window 200 cm-1 wide was used for this purpose. Finally, the optimal wavenumber values were identified within the selected range, using a feature selection approach based on Genetic Algorithms and on resampling. The work made will be relatively easily turned to the spectra actually recorded with the newly developed EC-QCLPAS instrument. Furthermore, the proposed approach allows progressive adaptation of the spectral dataset to real situations, even accounting for specific, different environments
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
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