199,033 research outputs found
Greener synthesis of Tadalafil using dimethylcarbonate and ionic liquids
No full textIntroduction
Tadalafil (commercially named Cialis™), a drug for the treatment of male erectile dysfunction, is commonly prepared from L-tryptophan through four steps in which different solvents and reagents are used. As it often happens in drug preparation the overall mass index of the preparation is quite low, causing a great amount of waste to be produced.
Results
Each step of the published synthesis of Tadalafil was investigated in view of the design of a greener and more afficient process by focussing on solvents and on integrating synthetic steps .
Dimethylcarbonate proved to be a good greener alternative to traditional solvents (i.e. nitromethane or ethanenitrile) for the diastereoselective Pictet-Spengler reaction (i.e. the second step of the synthesis). Both its lower toxicity and the water immiscibility contribute to the greenness of the procedure. In addition the last two steps of the preparation could be carried out stepwise in the same reactor by using [C4dmim][NTf2] (an ionic liquid) as the solvent.
These findings allowed us to propose two alternative processes named A and B. The principal improvements of processes A and B compared to the published synthesis is that they both do without solvents such as CH3CN, toluene, CH2Cl2, DMF and DMSO, and both combine the final two steps of by using an ionic liquid as solvent.
Conclusions
In summary processes A and B are high-yielding methods for the preparation of Tadalafil using only [C4dmim][NTf2] (an ionic liquid) and dimethylcarbonate as reaction media. Both have a better mass index than the published process, particularly if the the ionic liquid is recycled
Availability and use of molecular microbiological and immunological tests for the diagnosis of tuberculosis in Europe - public dataset
No full textThe original data are accessible as .csv file. This dataset supports the publication Tebruegge M, Ritz N, Koetz K, Noguera-Julian A, Seddon JA, et al. (2014) Availability and Use of Molecular Microbiological and Immunological Tests for the Diagnosis of Tuberculosis in Europe. PLOS ONE 9(6): e99129. https://doi.org/10.1371/journal.pone.0099129</span
Investigating Recurrences in Andrew Lewis’s Penmon Point
No full textPrevious conference papers (Seddon 2007; Seddon 2008) have introduced the con- cept of recurrence in acousmatic music, outlining the key issues of this approach to musical investigation and analysis. To briefly summarise, this concept provides a view of structuring processes in acousmatic composition in terms of the constituent sound materials and any perceived connections between them. It also stimulates the consideration of, and engagement with, issues and parameters of cross-referencing between sound materials, providing a view of the music’s structure. Such an investi- gative approach aims to stimulate both analytical and creative strategies; existing works may be appraised in such terms, yet a heightened awareness of the various issues may usefully enrich the compositional process.
This paper will discuss issues of recurrence in Penmon Point by Andrew Lewis (2002-03), using this approach to investigate a single composition. The paper will briefly outline the recurrence concept in terms of sound identity, memory and what might constitute a recurrence. Then, key sound identities within Penmon Point will be introduced, and the musical significance of various recurrences will be discussed. Recurring and varying spatial perspectives and spatial shifts will also be appraised, evaluating their contribution to the sense of structure. Finally, more abstract recur- rences and sound material connections will be explored, providing further avenues for musical contemplation
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Novel ionic media for liquid lasers
No full textIn a search for 3-5 µm lasing materials, crystals Of AlBr6Sb are isolated from a phosphorus tribromide-aluminium tribromide-antimony tribromide (PBr3-AlBr3-SbBr3) solution: this solid contains infinite chains of alternating [SbBr2]+ cations and [AlBr4]+ anions, linked by weak coordinate bonds, and represents the first structure containing the dibromostibinium(III) cation
Basic helicopter aerodynamics. [Third edition]
No full textBasic Helicopter Aerodynamics is widely appreciated as an easily accessible, rounded introduction to the first principles of the aerodynamics of helicopter flight. Simon Newman has brought this third edition completely up to date with a full new set of illustrations and imagery. An accompanying website www.wiley.com/go/seddon contains all the calculation files used in the book, problems, solutions, PPT slides and supporting MATLAB® code. Simon Newman addresses the unique considerations applicable to rotor UAVs and MAVs, and coverage of blade dynamics is expanded to include both flapping, lagging and ground resonance. New material is included on blade tip design, flow characteristics surrounding the rotor in forward flight, tail rotors, brown-out, blade sailing and shipborne operations. Concentrating on the well-known Sikorsky configuration of single main rotor with tail rotor, early chapters deal with the aerodynamics of the rotor in hover, vertical flight, forward flight and climb. Analysis of these motions is developed to the stage of obtaining the principal results for thrust, power and associated quantities. Later chapters turn to the characteristics of the overall helicopter, its performance, stability and control, and the important field of aerodynamic research is discussed, with some reference also to aerodynamic design practice. This introductory level treatment to the aerodynamics of helicopter flight will appeal to aircraft design engineers and undergraduate and graduate students in aircraft design, as well as practising engineers looking for an introduction to or refresher course on the subject.<br/
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
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