174,106 research outputs found
Measuring the phase of the strong decay amplitudes
No full textIt is shown that the interference between --> J/psi --> e(+)e(-) and --> e(+)e(-) can be measured with good accuracy at Fermilab. Therefore the phase of the strong decay amplitude of the J/psi with respect to the proton magnetic form factor will be obtained. There are hints, from J/psi --> and other J/psi decays, of an unexpected similar to 90 degrees phase. (C) 1997 Published by Elsevier Science B.V
Inert and nitrated cross-linked β-cyclodextrin binders for energetic applications
Get PDFThis PhD project focuses on the synthesis of new inert and nitrated cross-linked cyclodextrin systems as binders for energetic formulations. Three diglycidyl ethers with polyethylene glycol segments differing in length were used to crosslink β-cyclodextrin. The physicochemical properties of the compounds were investigated by proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. The polyethylene glycol chains linked to the rigid β-cyclodextrin conferred low glass transition temperatures (≥ –20 °C) on the inert binders and also on their nitrated derivatives (≥ –14 °C). This is the first time that nitrated βcyclodextrin derivatives have shown viscoelastic behaviour at temperatures below 0 °C. The viscoelasticity of both the inert and nitrated compounds increased with the amount of polyethylene glycol chains in the system. Inert binders with higher polyethylene glycol:β-cyclodextrin units ratios were softer and exhibited self-healing behaviour. The thermo-mechanical characterisation of these binders revealed that the system was exposed to mechanical stress below the glass transition temperature, and the stress was directly related to the proportion of the soft polyethylene glycol segments. The nitrated cross-linked derivatives were characterised by decomposition temperatures of ~200 °C and thermal degradation energies of 1400–2100 J g -1 strictly dependent on the degree of cross-linking and nitration. Self-healing properties were confirmed in nitrated products with a high polyethylene glycol segments content. Nitrated samples with polyethylene glycol segments:β-cyclodextrin units ratios >3.8:1 were safer to handle in the laboratory as determined by small-scale hazard and compatibility tests with various energetic fillers. Additionally, preliminary Energetic Materials Testing Assessment Policy (EMTAP) tests confirmed the samples were not sensitive to electrostatic discharge up to 4.5 J but were sensitive to impact, with a figure of insensitiveness of 29. The nitrated samples were unstable at temperatures >80 °C. The materials developed during this PhD project could facilitate the manufacturing and storage of new binders and may offer a suitable replacement for nitrocellulose and other binders in ii energetic formulations. The stabilisation of the nitrated cross-linked binders should be prioritised in future wor
"Und irgendwie hab ich das Gefühl gehabt, dass ich zu, dass ich zu diesem Platz dazu gehöre". Identità culturale e luoghi di famiglia nella seconda generazione di parlanti tedescofoni in Israele
No full textIl fatto che la narrazione comporti un processo di ricostruzione linguistica e comunicativa e di re-interpretazione del passato emerge chiaramente nelle interviste autobiografico-narrative, in cui i contenuti mnestici riaffiorano nel momento in cui il parlante narra la sua storia. Il racconto autobiografico consente alla persona di rappresentare e costruire attivamente la propria identità narrativa. L’intreccio che si viene così a creare con la configurazione e la riconfigurazione dell’identità di chi parla viene sottolineato, tra gli altri, da Fivush e Buckner: «We each author our own life story; in constructing and recounting our past, we are simultaneously constructing and reconstructing our selves. Who we are is very much created through autobiographical narratives». Nel caso della seconda generazione di parlanti tedescofoni in Israele l’indagine delle diverse costellazioni identitarie che affiorano nella narrazione (cfr. par. 2) è fortemente legata al confronto con la lingua, la cultura e i Paesi di origine dei genitori (cfr. par. 3). Attraverso un’analisi longitudinale di due testimonianze della stessa parlante, intervistata prima nel 2005, poi nel 2019 nella cornice del cosiddetto Israelkorpus (cfr. par. 3), il presente contributo intende mostrare come il lavoro identitario sia fortemente connesso alla (mutata) percezione dell’identità di un luogo, in questo caso Vienna
Stabilizing Effects in Oxazolidin-2-ones-Containing Pseudopeptides
No full textNovel homo-oligomers of the Gly-L-Oxd moiety have been prepared and their preferential conformations have been analyzed by IR, 1H NMR and CD spectroscopy, with the aim of checking whether these molecules are able to fold in ordered structures. We have noticed that in these homo-oligomers two stabilizing effects are active: besides the trans conformation of the imide group, the formation of C=O...H-N hydrogen bonds takes place and is very sensitive to the pseudopeptide size
A new entry to polyfunctionalized 4,5-trans disubstituted oxazolidin-2-ones from L-aspartic acid
No full textA straightforward synthesis of enantiomerically pure (4R,5S)-5-oxazolidinecarboxylic acid, 2-oxo-4-[(t-butyldimethyl-silyloxy)methyl]-, benzyl ester and of (4S,5S)-4-oxazolidinecarboxylic acid, 2-oxo-5-[(t-butyldimethylsilyloxy)methyl]-, benzyl ester was envisaged starting from readily available L-aspartic acid. The key step is the diastereoselective addition of iodine with the introduction of a new stereogenic centre
Rezension zu Mattfeldt, A., Schwegler, C. & Wanning, B. (Hrsg.). (2021). Natur, Umwelt, Nachhaltigkeit: Perspektiven auf Sprache, Diskurse und Kultur. Berlin und Boston: De Gruyter. 374 Seiten. ISBN 978-3-11-074034-9.
Get PDFRezension zum Band "Natur, Umwelt, Nachhaltigkeit: Perspektiven auf Sprache, Diskurse und Kultur", hrsg. v. A. Mattfeldt, C. Schwegler & B. Wanning (De Gruyter, 2021)
Oxazolidin-2-ones-Containing Pseudopeptides that Fold into beta-Bend Ribbon Spirals
No full textThree sets of oligomers containing the 4-carboxy-5-methyl-oxazolidin-2-one (Oxd) moiety have been synthesized with the aim of checking whether these molecules are able to fold in ordered structures: A set [Boc-(L-Ala-L-Oxd)n-OR], B set [Boc-(L-Ala-D-Oxd)n-OR] and C set [Boc-(Aib-L-Oxd)n-OR] preferential conformations have been analyzed with IR absorption, NMR and CD. We have noticed that in these oligomers three stabilizing effects are active: (i) the rigid Oxd –CO-N(C
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