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Mechanistic Investigations into the Palladium-Catalyzed Decarboxylative Allylic Alkylation of Ketone Enolates Using the PHOX Ligand Architecture
Get PDFPalladium-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
Austenite-Bainite Transformation Kinetics in Austempered AISI 5160 Steel
Get PDFThis research investigates the process of the formation of bainite in austempered 5160 steel. Steel bar samples were austenitized at 1128 K for 20 minutes followed by holding at various times from 10 seconds to 2 hours and isothermal temperatures from 561K to 728K to obtain a multi-phase matrix. Micro-hardness analysis and metallurgical optical microscopy were used to analyze the experimental results. Hardness results indicated that at the 561K, 589K, and 566K isothermal temperatures for 5160 steel, lower bainite transformation occurred. However, from 644K to 728K, upper bainite transformation was found from the steel. The formation of the bainitic phase in SAE 5160 steel was characterized using thermodynamic and kinetic theories
ITEC 5160 - Introduction to Instructional Design | Textbook
No full textThis OER textbook was designed and made available for ITEC 5160: Introduction to Instructional Design at the University of Wyoming. The textbook is available in four file formats. An HTML version that can be edited, printed, or transformed into an ePub file. Two PDFs, one for printing and one to be read on a device. An XML file which can imported into the Pressbooks platform.
Special thanks to Dr. Oksana Wasilik who adopted the textbook for her ITEC 5160 course and provided valuable input.
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Fragilidade a têmpera em aços SAE 5160
Get PDFO presente trabalho centra-se no fenômeno denominado de Fragilidade à Têmpera. Este fenômeno, observado em aços de alto carbono temperados, leva a uma fratura intergranular e está associado a segregação de fósforo e formação de cementita nos contornos de grão. Durante este estudo dois aços com composição química típica dos aços comerciais SAE 5160, mas com dois diferentes níveis de fósforo, foram utilizados para avaliar a influência da Fragilidade à Têmpera na resistência ao Impacto Charpy a temperatura ambiente. Os diferentes tratamentos térmicos realizados incluíram têmpera e revenidos convencionais e tratamentos térmicos especiais realizados na Gleeble 1500. Com o tratamento térmico convencional microestruturas martensíticas e bainítica foram obtidas. Para os aços martensíticos as temperaturas de austenitização variaram entre 830 e 1100 oC com o revenido variando entre como temperado até 500 oC por uma hora. A Gleeble 1500 foi utilizada para estudar a influência de um curto ciclo de austenitização na Fragilidade à Têmpera. Os resultados indicaram um melhor desempenho do aço de baixo P para todas as condições de tratamento térmico utilizadas. Os ciclos curtos de austenitização indicaram que a fragilidade à têmpera não pode ser evitada por este procedimento. Baseado na análise dos experimentos realizados com o aço SAE 5160 são apresentadas sugestões para minimizar os efeitos da Fragilidade à Têmpera em aços de alto carbono temperados e revenidos.The present work is centered on the quench embrittlement phenomena. This phenomenon, observed in hardened high carbon steels, leads to intergranular fracture and is associated with phosphorus segregation and cementite formation at grain boundaries. During this study, two steels with compositions typical for commercial SAE 5160 steel, but with two different levels of phosphorus, were utilized to evaluate the influence of quench embrittlement on room temperature impact toughness. The heat treatment included conventional quench and temper treatments and special heat treatments processed on the Gleeble 1500. With conventional heat treatment martensitic and bainitic microstructures were obtained. For the martensitic microstructures, austenitizing temperatures ranged from 830 to 1100 oC with tempering temperatures from as quenched to 500 oC. The Gleeble 1500 was used to study the influence of short time heat treatment on the quench embrittlement. The low P steel exhibited better performance than the high P steel under all heat treatment conditions. Results on the short-holding-time treatment indicated that the QE can not be avoided by this procedure and a similar behavior between conventional and shortholding time treatment was observed. Based on an analysis of the experiments realized with the SAE 5160 steel suggestions to minimize the effects of quench embrittlement in high carbon quench and tempered steels were discussed
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Austempering AISI 5160
No full textThis report discusses the result of different austempering holding times and their effect on the material's hardness, ductility and yield strength. AISI 5160 steel samples were heated until they were entirely austenite and then subjected to the austempering process, submerged in a 600°F salt bath for 1, 2, 5, 30, or 90 minutes depending on the sample. Some samples were also heat-treated using water quenching and annealing for comparison. The samples were then cut, ground, and polished using standard sample preparation methods for analysis using optical microscopy, scanning electron microscopy, and x-ray diffraction. Separate samples in the form of tensile testing bars were prepared similarly. Vickers microhardness, Rockwell hardness, and tensile testing was performed
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
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