1,724,285 research outputs found
Mechanistic Investigations into the Palladium-Catalyzed Decarboxylative Allylic Alkylation of Ketone Enolates Using the PHOX Ligand Architecture
No full textPalladium-catalyzed asymmetric allylic alkylation has become a large and important field for chemical synthesis. Many methodologies in this field offer mild conditions under which challenging and important molecular features can be reliably synthesized, including chiral all-carbon quaternary stereocenters. As a result, palladium- catalyzed asymmetric allylic alkylation has found significant use in total synthesis, and growing use in industry. While the general process of palladium-catalyzed asymmetric allylic alkylation has been studied for decades, there have been a number of recent modifications and developments, such as asymmetric versions of decarboxylative allylic alkylation procedures that are not yet well understood. The development of future implementations and improvements to palladium-catalyzed asymmetric allylic alkylation and related methodologies is expected to be facilitated by a better understanding of these more recent developments, and thus further mechanistic investigation is warranted.
Reported herein is a set of investigations into the palladium-catalyzed decarboxylative asymmetric allylic alkylation of ketone enolates using the PHOX ligand architecture. By monitoring the reaction via 31P NMR, a series of previously unidentified key intermediates is discovered. Two representatives of these key intermediates are isolated and characterized. The solution behavior of these species under reaction-like conditions is studied along with a few novel and related complexes. The role of these intermediates and their impact on the behavior of the reaction and product formation is discussed. Previously confounding experimentally observed behavior for this methodology is rationalized via the properties elucidated for these discovered intermediates.</p
Draft genome sequence of clostridium sporogenes PA 3679, the common nontoxigenic surrogate for proteolytic clostridium botulinum
No full textClostridium sporogenes PA 3679 is widely used as a nontoxigenic surrogate for proteolytic strains of Clostridium botulinum in the derivation and validation of thermal processes in food. Here we report the draft assembly and annotation of the C. sporogenes PA 3679 genome. Preliminary analysis demonstrates a high degree of relatedness between C. sporogenes PA 3679 and sequenced strains of proteolytic C. botulinum. © 2012, American Society for Microbiology
Smith Family Papers (SC 3679)
No full textFinding aid, scans and typescripts (Click on Additional Files below) for Manuscripts Small Collection 3679. Two items relating to the Smith family of Warren County, Kentucky: a letter, 18 November 1852, from Amanda M. F. Withers, Dripping Spring, Edmonson County, Kentucky, to Sarah Hampton in Warren County; having recently moved, she describes her labors setting up housekeeping, gives regards to her friends and Sarah’s family, advises Sarah to be careful in choosing a husband, and asks to be sent some plant cuttings. Also, a codicil to the will of Sarah’s future father-in-law Daniel C. Smith, 1868
Frequencies (percentages) of adolescent characteristics by bullying perpetration (n = 3679 participants<sup>a</sup>).
No full textFrequencies (percentages) of adolescent characteristics by bullying perpetration (n = 3679 participantsa).</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
Bacteriostatic action of sorbic acid: a hypothesis induction of a stringent-type response in putrefactive anaerobe 3679 by the effects of the protonophoric activity of sorbic acid
No full textThe inhibitory effect of potassium sorbate on bioenergetics, amino acid uptake, protein synthesis, cell regulation, and morphology was examined in Putrefactive Anaerobe (PA) 3679. Undissociated sorbic acid appeared to act as a protonophore, lowering the intracellular pH and dissipating the protonmotive force of the membrane. Sorbate and benzoate inhibited uptake of the amino acid, phenylalanine. Further studies on the effects of sorbate on PA 3679 revealed altered patterns of phosphorylated nucleotide accumulation with increased rates of formation of GTP, ppGpp, and an unidentified compound, possibly pppGpp, and a decreased rate of protein synthesis. The addition of a noninhibitory amount of tetracycline released the sorbate-induced inhibition of growth in PA 3679. Based on these results, it is concluded that inhibition of PA 3679 by sorbate resulted from a stringent-type response to the protonophoric activity of sorbic acid. Similar morphological changes were observed when PA 3679 was treated with sorbate or inorganic acid, HCl. In both cases, the cells became filamentous with bends and bulges and had thickened cell walls. Sorbate-induced filaments had fewer septa than did the acid-treated cells. In contrast nitrite-treated cells also became filamentous with bends, but the cells had many septa, did not have thickened cell walls, and did not bulge. Low concentrations of sucrose and sodium chloride antagonized the inhibitory effects of sorbate on the growth of PA 3679; however, a low concentration of nitrite acted synergistically with sorbate. Nitrite alone increased the intracellular pH and protonmotive force in untreated as well as sorbate-treated cells.Ph.D
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