1,720,998 research outputs found
Toward the synthesis of the deuterated finland trityl radical
Get PDFRecently, there has been considerable interest in developing soluble radical probes for bio-imaging applications, such as the EPR detection of tumors and protein distribution assays. The Finland trityl radical has previously been exploited as such a probe, but the sensitivity for detection of this probe is significantly compromised due to coupling of the radical electron spin with the nuclear spin of the methyl hydrogens of this species. To improve the sensitivity of this probe in biological imaging applications, this work describes our efforts toward the synthesis of a deuterated analogue of the Finland trityl that lacks the possibility of such hyperfine coupling and is anticipated to have a sharpened EPR signal. The synthetic scheme consists of six steps, based on a modified procedure of Reddy et al. Our best efforts have led to a 92% deuterated precursor of the Finland trityl.
Advisor: Dr. Christopher M. HadadNo embarg
Synthetic Approach to Realkyation of Aged Acetylcholinesterase Using Quinone Methide Precursors
Get PDFMathematical and Physical SciencesOrganophosphorus (OP) nerve agents are a class of toxic compounds that inhibit acetylcholinesterase (AChE), an enzyme that catalyzes the conversion of acetylcholine to choline at neurosynaptic junctions. OP inhibits AChE by binding to the active site and this undergoes a subsequent irreversible process called aging, where the OP-AChE adduct is dealkylated. This results in the accumulation of excess acetylcholine in the central nervous system that causes significant nerve damage. Current oxime-based pharmaceutical agents, such as 2-PAM, used to treat inhibited AChE are ineffective on aged AChE. Previous studies have shown that quinone methides (QM) are alkylating agents and these could potentially reverse the aging process through a kinetically favored realkylation mechanism. In the past, we have designed and synthesized a library of QM precursors. Our research focuses on the analysis of these alkylating compounds and investigating their ability to realkylate model phosphonate.National Institute of Health (NIH) Grant 1U01–NS087983Academic Major: Chemistr
Ultrafast Spectroscopy And Computational Study Of The Photochemistry Of Diphenylphosphoryl Azide: Direct Spectroscopic Observation Of A Singlet Phosphorylnitrene
Get PDFMathematical and Physical Sciences: 2nd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)In order to characterize the active site of human paraoxonase 1 (HuPON1), photochemistry of a possible photoaffinity label diphenylphosphoryl azide was studied by femtosecond transient absorption spectroscopy, chemical analysis of light-induced reaction products as well as by RI-CC2/TZVP and TD-B3LYP/TZVP computational methods. Theoretical methods predicted two possible mechanisms for singlet diphenylphosphorylnitrene formation from the photoexcited phosphoryl azide. (i) Energy transfer from the (π, π*) singlet excited state, localized on a phenyl ring, to the azide moiety, thereby leading to the formation of the singlet excited azide, which subsequently loses molecular nitrogen to form the singlet diphenylphosphorylnitrene. (ii) Direct irradiation of the azide moiety to form an excited singlet state of the azide, which in turn loses molecular nitrogen to form the singlet diphenylphosphorylnitrene. Two transient species were observed upon ultrafast photolysis (260 nm) of diphenylphosphoryl azide. The first transient absorption, centered at 475 nm (lifetime (τ) ~ 28 ps), was assigned to a (π, π*) singlet S1 excited state localized on a phenyl ring, and the second transient observed at 525 nm (τ ~ 480 ps) was assigned to singlet diphenylphosphorylnitrene. Experimental and computational results obtained from the study of diphenylphosphoramidate, along with the results obtained with diphenylphosphoryl azide, supported the mechanism of energy transfer from the singlet excited phenyl ring to the azide moiety, followed by nitrogen extrusion to form the singlet phosphorylnitrene. Ultrafast time-resolved studies performed on diphenylphosphoryl azide with the singlet nitrene quencher, tris(trimethylsilyl)silane, confirmed the spectroscopic assignment of singlet diphenylphosphorylnitrene to the 525 nm absorption band.A three-year embargo was granted for this item
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
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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