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81.
We examine the rhetorical methods of Leonardo of Pisa in his exposition of single false position in Liber Abbaci. For example, Leonardo makes extensive use of formulaic phrases in his solutions. Some of these formulas also seem to indicate whether a particular solution needs further justification. Although he prefers proofs in terms of the pseudo-Euclidean canon of al-Khwārizmī, sometimes such proof eludes Leonardo and he resorts instead to justification by experiment. We also look at the extent to which using symbolic representations might distort our view of Leonardo's thinking. 相似文献
82.
Darcy Fallaise Hannah Balkwill Tweedie Julie Konzuk Carol Cheyne E. Erin Mack James G. Longstaffe 《Magnetic resonance in chemistry : MRC》2019,57(2-3):93-100
Nonaqueous phase liquids (NAPLs) located at the surface of the water table and/or below the water table are often a significant source for groundwater contamination near current or former commercial/industrial facilities. Due to the complex and long history of many industrial sites, these NAPLs often contain a complex mixture of contaminants and as such can be difficult to fully characterize using conventional analytical methods. Remediation and risk assessment activities at sites containing NAPLs may, subsequently, be hindered as the contamination profile may not be fully understood. This paper demonstrates the application of bench-scale 1H nuclear magnetic resonance (NMR) spectroscopy as a practical tool to assist with the characterization of complex NAPLs. Here, a NAPL collected from a contaminated site situated near a former chemical manufacturing facility was analyzed using a combination of one-dimensional (1D) 1H NMR spectroscopy and two-dimensional (2D) 1H J-resolved spectroscopy (JRES). It is shown that 1D NMR experiments are useful in the rapid identification of the classes of compounds present, whereas 2D JRES NMR experiments are useful in identifying specific compounds. The use of benchtop NMR spectroscopy as a simple and cost effective tool to assist in the analysis of contaminated sites may help improve the practical characterization of many heavily contaminated sites and facilitate improved risk assessments and remedial strategies. 相似文献
83.
Moyet Matthew A. Kanan Sofian M. Varney Hannah M. Abu-Farha Nedal Gold Davis B. Lain William J. Pike Robert D. Patterson Howard H. 《Research on Chemical Intermediates》2019,45(12):5919-5933
Research on Chemical Intermediates - Phosphonium iodobismuthates(III) (MePh3P)3[Bi3I12] (1) and (Ph4P)3[Bi3I12] (2) were prepared, and X-ray crystal structures were determined for both complexes.... 相似文献
84.
Garima Ghale Adrienne G. Lanctt Hannah T. Kreissl Maik H. Jacob Helge Weingart Mathias Winterhalter Werner M. Nau 《Angewandte Chemie (International ed. in English)》2014,53(10):2762-2765
The efficacy of drugs and biomolecules relies on their ability to pass through the bilayer. The development of methods to directly and sensitively monitor these membrane transport processes has remained an experimental challenge. A macrocyclic host (p‐sulfonatocalix[4]arene or cucurbit[7]uril) and a fluorescent dye (lucigenin or berberine) are encapsulated as a chemosensing ensemble inside liposomes, which allows for a direct, real‐time fluorescence monitoring of the passage of unlabeled bioorganic analytes. This in vitro assay is transferable to different channel proteins and analytes, has potential for fluorescence‐based screening, e.g., of channel modulators, and yields the absolute kinetics of translocation. Using this new biophysical method, we observed for the first time direct rapid translocation of protamine, an antimicrobial peptide, through the bacterial transmembrane protein OmpF. 相似文献
85.
86.
Marianne E. Burnett Hannah M. Johnston Kayla N. Green 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(12):1074-1079
Nicotinamides are a class of compounds with a wide variety of applications, from use as antimicrobial agents to inhibitors of biological processes. These compounds are also cofactors, which are necessary components of metabolic processes. Structural modification gives rise to the activities observed. Similarly, 1,3,4‐thiadiazoles have been shown to possess antioxidant, antimicrobial, or anti‐inflammatory biological activity. To take advantage of each of the inherent characteristics of the two aforementioned functional groups, 2‐nicotinamido‐1,3,4‐thiadiazole, C8H6N4OS, was synthesized. Since defining chemical connectivity is paramount in understanding biological activity, in this report, the structural characterization of 2‐nicotinamido‐1,3,4‐thiadiazole has been carried out using X‐ray crystallographic methods. The NMR‐derived assignments were made possible by utilizing one‐ (1D) and two‐dimensional (2D) NMR techniques. In addition, UV–Visible and IR spectroscopies, and elemental analysis were used to fully characterize the product synthesized by the one‐step reaction between nicotinoyl chloride hydrochloride and 2‐amino‐1,3,4‐thiadiazole. Computational parameters related to blood–brain barrier permeability are also presented. 相似文献
87.
Marsden DM Nicholson RL Skindersoe ME Galloway WR Sore HF Givskov M Salmond GP Ladlow M Welch M Spring DR 《Organic & biomolecular chemistry》2010,8(23):5313-5323
The screening of large arrays of drug-like small-molecules was traditionally a time consuming and resource intensive task. New methodology developed within our laboratories provides an attractive low cost, 3D microarray-assisted screening platform that could be used to rapidly assay thousands of compounds. As a proof-of-principle the platform was exploited to screen a number of quorum sensing analogs. Quorum sensing is used by bacterium to initiate and spread infection; in this context its modulation may have significant clinical value. 3D microarray slides were probed with fluorescently labeled ligand-binding domains of the LuxR homolog CarR from Erwinia carotovora subsp. carotovora. The 3D microarray platform was used to discover the biologically active chloro-pyridine pharmacophore, which was validated using a fluorometric ligand binding assay and ITC. Analogs containing the chloro-pyridine pharmacophore were found to be potent inhibitors of N-acyl-homoserine-lactone (AHL) mediated quorum sensing phenotypes in Serratia (IC(50) = ~5 μM) and Pseudomonas aeruginosa (IC(50) = 10-20 μM). 相似文献
88.
Hannah Runnqvist Søren Alex BakMartin Hansen Bjarne StyrishaveBent Halling-Sørensen Erland Björklund 《Journal of chromatography. A》2010,1217(16):2447-2470
Pressurised liquid extraction (PLE) is now a well established and extensively applied extraction technique in environmental analysis for pollutants such as persistent organic pollutants (POPs). During the past decade, an emerging group of environmentally interesting analytes are pharmaceuticals that are continuingly released into the environment. This class is comprised with compounds of various properties. As the field of the analysis of these compounds grows, an increasing number of PLE methods for pharmaceuticals of varying quality are developed and published. This review summarises the critical PLE parameters during PLE method development and highlight them with examples from recently published papers utilising pressurised liquid extraction for the determination of pharmaceuticals in environmental and biological matrices. These recent methods are summarised and critically discussed with the aim to provide important reflections to alleviate in future PLE development for pharmaceuticals in environmental matrices. 相似文献
89.
The synthesis of a Tentagel-supported peptide incorporating the reactive triad of serine, histidine and aspartic acid, found within serine protease enzymes, is described. 相似文献
90.
[reaction: see text] The Kishner reduction of 2-furylhydrazone gives 2-methylene-2,3-dihydrofuran as the major abnormal reduction product. 2-Methylene-2,3-dihydrofuran is an excellent ene in the carbonyl-ene reaction, reacting with a variety of aldehydes. Most notable was the asymmetric carbonyl-ene reaction of 2-methylene-2,3-dihydrofuran and decanal using Ti(OCH(CH3)2)4/(S)-BINOL to give the corresponding alcohol in 66% yield and 94% ee. The reaction of 2-methylene-2,3-dihydrofuran with 2 equiv of 1,4-benzoquinone unexpectedly gave a monoalkylated 1,4-hydroquinone/1,4-benzoquinone electron donor-acceptor complex. 相似文献