1,720,984 research outputs found
15 N Reaction Monitoring at Low and Inhomogeneous Magnetic Fields Enabled by Hyperpolarization With Parahydrogen
No full textAbstract The combination of hyperpolarization methods with low and inhomogeneous fields promises to expand the application of nuclear magnetic resonance (NMR) to fields that nowadays are not standard. Reducing the magnetic field strengths and homogeneity requirements opens the door to a wide variety of magnet designs that can allow for monitoring chemical reactions in the benchtop or even larger reactors. In this work, we propose a method to monitor 15 N chemical reactions at low and inhomogeneous fields based on parahydrogen‐induced polarization. The concept was demonstrated at a magnetic field of 66 mT and 81 ppm inhomogeneity. Specifically, we measured the conversion of 15 N‐boronobenzyl‐2‐styrylpyridinium ( 15 N‐BBSP) to 15 N‐2‐styrylpyridin ( 15 N‐SP). This enables the detection of H 2 O 2 with high sensitivity and selectivity, exhibiting a significant chemical shift difference of 88.4 ppm, when 15 N‐SP is obtained after a base‐assisted 1,6 elimination/rearrangement. The long T 1 of 15 N‐BBSP at low magnetic fields (194 s at 100 mT) exemplifies the potential of hyperpolarized 15 N for low field applications. We envision the implementation of our methods for studying chemical reactions in benchtop devices, drug screening, investigating biological systems in their native environments, preclinical research and contrast development for low‐field and portable magnetic resonance imaging (MRI).H2020 Marie Skłodowska-Curie Actions https://doi.org/10.13039/100010665H2020 European Research Council https://doi.org/10.13039/10001066
O Hyperfine Spectroscopy Reveals Hydration Structure of Nitroxide Radicals in Aqueous Solutions
No full textMax-Planck-Gesellschaft https://doi.org/10.13039/501100004189Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659European Research Council https://doi.org/10.13039/50110000078
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
Real‐Time Metabolic Magnetic Resonance Spectroscopy of Pancreatic and Colon Cancer Tumor‐Xenografts with Parahydrogen Hyperpolarized 1‐13C Pyruvate‐d3
Get PDFParahydrogen‐induced polarization (PHIP) is an emerging technique to enhance the signal of stable isotope metabolic contrast agents for Magnetic Resonance (MR). The objective of this study is to continue establishing 1‐13C‐pyruvate‐d3, signal‐enhanced via PHIP, as a hyperpolarized contrast agent, obtained in seconds, to monitor metabolism in human cancer. Our focus was on human pancreatic and colon tumor xenografts. 1‐13C‐vinylpyruvate‐d6 was hydrogenated using parahydrogen. Thereafter, the polarization of the protons was transferred to 13C. Following a workup procedure, the free hyperpolarized 1‐13C‐pyruvate‐d3 was obtained in clean aqueous solution. After injection into animals bearing either pancreatic or colon cancer xenografts, slice‐selective MR spectra were acquired and analyzed to determine rate constants of metabolic conversion into lactate and alanine. 1‐13C‐pyruvate‐d3 proved to follow the increased metabolic rate to lactate and alanine in the tumor xenografts
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
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