175 research outputs found
I-Modified Nucleosides as DNA-Sugar Centered Radical Precursors II-DNA Excess Electron Transfer Studies III-A new Direct DNA Detection Method: DNA Photography
No full textA perspective on enantioselective chromatography by comparing ultra-high performance supercritical fluid chromatography and normal-phase liquid chromatography through the use of a pirkle-type stationary phase
No full textSince their discovery, the Pirkle-type chiral stationary phases, and in particular the Whelk-O1, have been used in a large number of applications and theoretical studies. Although they can be used in many elution modes, their main field of application is in normal phase liquid chromatography and more recently in supercritical fluid chromatography. In this review, we tried to compare the two techniques using the Whelk-O1 stationary phase as a trait d'union. The main milestones obtained in the last decades of research in enantioselective chromatography and possible lights and shadows of the two techniques have been described. There is still a long way to go to achieve the full potential in the field of enantioselective separations, and especially ultra-high supercritical fluid chromatography, given its great potential, is a technique still to be improved
Studio di una nuova metodologia per la misura del livello delle vibrazioni trasmesse dalle macchine agricole monoasse condotte a mano
No full textL’applicazione della Direttiva Macchine alle piccole operatrici agricole monoasse richiede, tra l’altro, la determinazione del livello delle vibrazioni trasmesse al conducente attraverso gli organi di guida, secondo specifiche norme che prevedono la presenza di un operatore alla guida. Purtroppo, come è stato messo in luce da diverse campagne sperimentali, la presenza di un operatore introduce una grande variabilità nelle misure. Gli studi sulle metodologie alternative, basate sostanzialmente sull’impiego di attrezzature meccaniche in grado di simulare il sistema mano-braccio, non si sono ancora concretizzati in una proposta di norma. Di conseguenza l’attenzione degli autori della presente nota si è concentrata sulla ricerca di un metodo in grado di garantire, a costi sostenibili, una più alta riproducibilità delle misure, rispetto ai metodi attualmente in uso. Il metodo proposto si basa sull’impiego di un dispositivo di semplice realizzazione in grado di vincolare la macchina in prova, senza un operatore, in ragionevoli condizioni di sicurezza e permettendo di ottenere valori di accelerazione sulle stegole di guida dello stesso ordine di grandezza di quelle osservabili con procedura standard. La nuova metodologia ha fornito risultati molto incoraggianti, permettendo di osservare una rilevante riduzione nella dispersione delle misure di accelerazione media equivalente. Pur se in una fase iniziale, tale metodologia sembra adeguata ad un successivo sviluppo sul piano normativo
Applicazioni dei metodi di simulazione numerica nell’ingegneria agroalimentare
No full textNell’ambito dell’ingegneria agroalimentare sussistono numerosi problemi di natura fisica legati alla progettazione degli impianti e dei processi. In particolare si tratta di problemi meccanici strutturali, fluidodinamici e termici, spesso di grande complessità.
In tempi recenti, con la crescente disponibilità di risorse di calcolo, è divenuto sempre più agevole il ricorso a tecniche di progettazione attraverso la simulazione dei fenomeni citati. In particolare i metodi numerici di maggior diffusione ed efficacia si sono dimostrati quelli denominati ad elementi finiti (EF) e volumi finiti (VF).
In tale ottica lo scopo del presente lavoro è stato quello richiamare brevemente i fondamenti dei metodi EF/VF, proponendo una discussione circa la loro applicazione nel settore dell’ingegneria agroalimentare, assieme ad una breve rassegna bibliografica. Ad integrazione vengono riportati i risultati ottenuti da una autonoma campagna d’indagine, riguardo a problemi di natura termofluidodinamica
Thermal decomposition of the tert-butyl perester of thymidine-5'-carboxylic acid. Formation and fate of the pseudo-C4'-radical
No full textThermal decomposition of the tert-butyl perester of thymidine-5'-carboxylic acid carried out at 85 °C in different solvents affords the tert-butylacetal, deriving from in cage decomposition, and pseudo C4'-radicals. These latter can be reduced to by hydrogen
atom abstraction from thiol (thiophenol or glutathione) or THF, or can be oxidized to cations by dioxygen or perester itself. Cations are stereoselectively trapped by the nucleophilic solvent (tert-butanol, methanol, water) to give acetals the corresponding acetals
Radical cyclization approach to cyclonucleosides
No full textEfficient methodologies based on consecutive radical ractions for the preparation of cyclonucleosides are reported. The reactions were performed on modified thymidine and 2'-deoxyadenosine substrates using (TMS)3SiH as the reducing agent. The rate constants for the 6-exo-trig radical cyclization have been estimated
Manetto di Jacopo Amannatini, the Fat Woodcarver
No full textThe Story of the Fat Woodcarver, written by Antonio di Tuccio Manetti, probably recalls a popular anecdote about a Florentine artisan who was humiliated by his friend, Filippo di ser Brunellesco. The joke played by the architect has been at the forefront of scholarly interest, while the main protagonist has so far received limited attention. This article aims to reconstruct the life of Manetto di Jacopo Amannatini, that is, the Fat Woodcarver, in the context of his social relationships with the other figures in the story. It argues that Manetti’s account is grounded in concrete historical facts and therefore provides us with a unique picture of the intersections that existed between artisan and merchant networks in and beyond early Renaissance Florence. Manetto’s character may well symbolize those itinerant craftsmen who, by acknowledging their position in their own communities, and thanks to their skills and their courage to migrate to remote places, like the Kingdom of Hungary, managed to improve their social status significantly
Foliar spray deposition in a “tendone” vineyard as affected by airflow rate, volume rate and vegetative development
No full textThe objective of this study was the evaluation of the effect of airflow rate and volume rate on foliar spray deposition in a “tendone” vineyard using an air-assisted sprayer with two counter-rotating fans and anterior intake. Experimental tests were carried out considering two airflow rates (2.43 and 5.71 m3 s−1), two volume rates (335 and 625 L ha−1) and keeping the forward speed constant (1.1 m s−1). To take into account the effect of vegetative development of the vineyard, experiments were replicated in two phenological stages (full flowering and berry touch), characterised by different Leaf Area Indices (2.21 and 5.83). The sprayer was calibrated using a patternator purposely designed for “tendone” vineyards, assuming the vineyard Leaf Area Index (LAI) pattern as a reference. Sprayer calibration was accomplished achieving a close correlation between LAI pattern and the quantity of liquid intercepted by the patternator (coefficients of linear correlation ranged from 0.95 to 0.99, all significant at p < 0.05). Measurements on vines showed that volume rate did not affect foliar spray deposition at either phenological stage, whereas airflow rate had an opposite effect at the two phenological stages. At full flowering, the increase in airflow rate produced a significant decrease in foliar deposit (from 0.986 to 0.693 μL cm−2 on the most exposed vegetation, −30%); on the contrary, at the berry touch growth stage the increase in airflow rate produced a significant increase in foliar deposits (from 0.339 to 0.484 μL cm−2, +43%)
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