11 research outputs found
A B-11 and Li-7 MAS-NMR study of sol-gel lithium triborate glass subjected to thermal densification
No full textSurvival of Spoilage and Pathogenic Microorganisms on Cardboard and Plastic Packaging Materials
No full textThe aim of this work was to study the interaction of corrugated and plastic materials with pathogenic and spoiling microorganisms frequently associated to fresh produce. The effect of the two packaging materials on the survival during the storage of microorganisms belonging to the species Escherichia coli, Listeria monocytogenes, Salmonella enteritidis, Saccharomyces cerevisiae, Lactobacillus plantarum, Pseudomonas fluorescens, and Aspergillus flavus was studied through traditional plate counting and scanning electron microscopy (SEM). The results obtained showed that cardboard materials, if correctly stored, reduced the potential of packaging to cross-contaminate food due to a faster viability loss by spoilage and pathogenic microorganisms compared to the plastic ones. In fact, the cell loads of the pathogenic species considered decreased over time independently on the inoculation level and packaging material used. However, the superficial viability losses were significantly faster in cardboard compared to plastic materials. The same behavior was observed for the spoilage microorganisms considered. The SEM microphotographs indicate that the reduction of superficial contamination on cardboard surfaces was due to the entrapping of the microbial cells within the fibers and the pores of this material. In addition, SEM data showed that the entrapped cells were subjected to more or less rapid lyses, depending on the species, due to the absence of water and nutrients, with the exception of molds. The latter spoilers were able to proliferate inside the cardboard fibers only when the absorption of water was not prevented during the storage. In conclusion, the findings of this work showed the reduction of cross-contamination potential of corrugated compared to plastic packaging materials used in fruit and vegetable sector. However, the findings outlined the importance of hygiene and low humidity during cardboard storage to prevent the mold growth on packaging
Raman and NMR analysis of LiClO4 concentrated solutions in ethylene carbonate propylene carbonate
No full textA comparative Raman and C-13-NMR study has been performed on LiClO4 concentrated solutions in ethylene carbonate (EC)-propylene carbonate (PC), which are of interest for electrochemical devices like secondary lithium batteries. A phase transition has been detected near a ratio N = [Li+]/[EC + PC] congruent to 0.5. Below this threshold, Li+ ions are relatively free to move and are solvated by EC and PC with a coordination number, n, which approaches similar to 2. In more concentrated solutions the cations seem to form a complex by ''sandwiching'' an EC and a PC molecule
Li+ solvation in ethylene carbonate-propylene carbonate concentrated solutions: A comprehensive model
No full textSpectroscopic (Raman, NMR, impedance spectroscopy), and thermal [differential scanning calorimetry (DSC)] techniques have been used to study the solvation mechanism of lithium ions in ethylene carbonate (EC)-propylene carbonate (PC) concentrated solutions. For values of N = [Li+]/[EC + PC]less than or equal to 0.2 all the cations are solvated. by similar to 4 solvent molecules and interaction chiefly takes place between Li+ and the ring oxygens, For N>0.2 a part of Li+ ions begins to farm complexes with two solvent molecules (sandwich configuration). At N congruent to 0.5 nearly all cations are complexed, and a crystalline compound is formed at room temperature. For higher values of N a reassociation of the salt takes place. (C) 1997 American Institute of Physics
13C and 2D WISE NMR studies of the host mobility in two aromatic complexes of p-tert-butyl-calixarene
No full textSolid-state NMR techniques are used to study the effect of the inclusion of toluene and benzene on the mobility of p-tert-butylcalixarene. We attribute the great increase in host mobility upon complexation to the lack of strong directional intermolecular interactions. The differences in the behaviour of the host in the two complexes are explained in terms of the steric effects of the guest methyl group
Nodi urbani
No full textProponiamo una divisione in serie dei materiali donati da Ugo La Pietra relativi al progetto Nodi urbani
Nodi urbani e Tuberie
10B-PIETRA.tif, disegno non datato
1-10B-PIETRA.tif, disegno non datato
24_nodi urbani.jpg disegno firmato e datato1966
25_nodi urbani.tif disegno firmato e datato 1965
26_nodi urbani.tif disegno firmato e datato 1965
27_nodi urbani.tif disegno firmato e datato 1965
28_nodi urbani.tif disegno non datato
29_nodi urbani.tif: disegno firmato e datato 1966
30_nodi urbani.tif: disegno firmato e datato 1965
1-10D-PIETRA.tif disegno conservato anche al Centre Pompidou, Parigi
1-10C-PIETRA.tif disegno non datato
Emergenze urbane:
6.4A_ULP.tif disegno non datato
6.4B_ULP.tif disegno non datato
31_nodi urbani.tif disegno firmato e datato 1964I documenti donati da Ugo La Pietra intitolati Nodi urbani costituiscono, rispetto al progetto per la Casa dello Scultore Cappello, una ulteriore declinazione del 'non realizzato'. Se la casa per uno scultore è esercizio accademico 'teorico' che si innesta anche sulla ricerca pittorica di La Pietra, i disegni intitolati Nodi urbani rappresentano la 'cornice' di una serie di sperimentazioni sviluppate negli anni successivi alla laurea in architettura presso il Politecnico di Milano.
La ricerca di Ugo la Pietra a partire dal 1962 è sottoposta ad una duplice verifica sia nell'ambito della attività didattica (quella che è definita Sinestesia delle arti trova un importante momento di verifica nella esposizione realizzata con Alberto Seassaro La Ricerca morfologica al Politecnico di Milano), sia nella conformazione di spazi scavati come antri o tunnel urbani che divengono la struttura connettiva delle sculture di Kengiro Azuma, Giacomo Benevelli e Giancarlo Marchese nel tessuto (1962/64); sia in occasione di progetti come quello sviluppato in collaborazione con lo stesso Alberto Seassaro e Nanda Vigo del Monumento alla resistenza per la città di Brescia, 1966/67, oppure come nella proposta presentata nell’ambito del seminario internazionale a Vela Luka nel 1968 (Emergenze urbane – Proposte per la Costa dalmata).
Possiamo quindi individuare alcuni sottosistemi all'interno della documentazione archiviata in MoRE: innanzitutto i veri e propri Nodi urbani (1964/67) che sono riconducibili alla teoria di esplorazione e studio dello spazio urbano condotto all'interno del corso di progettazione tra il 1965 e il 1967 con Blasi, Banfi, Seassaro e Stevan (vedi La traducibilità dei nessi intercorrenti all'interno di una struttura urbana in visualizzazioni spaziali, Ares, Milano 1966). Anche in questo caso la serie è documentata sia al Centre Pompidou che nel MoRE dove i 10 disegni (lo schizzo presente anche a Parigi è il 1-10D-PIETRA.tif) costituiscono uno sviluppo dei percorsi sotterranei per le sculture di Kengiro Azuma, Giacomo Benevelli e Giancarlo Marchese e una rielaborazione della serie delle Tuberie che, come detto, trovano un momento di verifica nella proposta per il Monumento di Brescia. Elemento comune di questi disegni è la messa in forma e l’articolazione di emergenze all'interno del territorio urbanizzato difficilmente decifrabile che la fitta trama di segni di La Pietra cerca di tradurre.
I percorsi e le interconnessioni che qualificano il territorio definiscono strutture complesse che sembrano essere una declinazione di uno dei temi centrali del dibattito architettonico della seconda metà degli anni Sessanta, quello delle megastrutture.
Il passaggio definitivo dalle sculture primordiali abitabili a queste declinazioni del tema megastrutturale può essere individuato nelle proposte elaborate in occasione della partecipazione all’Incontro internazionale a Vela Luka nel 1968 nell’isola di Korcula, un seminario promosso da un gruppo di artisti dalmati e coordinato da Peter e Kossa Omckus (6.4A_ULP.tif, 6.48_ULP.tif, 31_nodi urbani.tif) a cui La Pietra partecipa insieme ad altri artisti italiani (Paolo Scheggi, Achille Perilli, Sacripanti) confrontandosi con esponenti della ricerca artistica ed architettonica internazionale; una occasione per “porre in atto l’utopia”, come scriveva Gillo Dorfles sulla rivista “In” (1970).The documents donated by Ugo La Pietra and named Nodi Urbani constitutes, compared to the Progetto per la Casa dello Scultore Cappello, a further variation of the 'unrealised'. If the casa per uno scultore is a ‘theoretical’ academic exercise that engages even the pictorial research of La Pietra, the drawings titled Nodi Urbani represent the 'frame' of a series of lexperiments carried out in the years following his graduating in architecture at the Politecnico di Milano.
The research of Ugo la Pietra since 1962 has been checked through a double test, both the teaching activity (what is called Sinestesia delle arti can find an important test opportunity in the exhibition made with Alberto Seassaro, La Ricerca morfologica at Politecnico di Milano ), an the shape of the spaces excavated like caves or urban tunnels that become the connective structure of the sculptures of Kengiro Azuma, Giacomo Benevelli and Giancarlo Marchese in the tissue (1962/64); otherwise on the occasion of projects like the one developed in collaboration with Alberto Seassaro and Nanda Vigo, Monumento alla resistenza per la città di Brescia, 1966/67, or the proposal presented during the international seminar in Vela Luka in 1968 (Emergenze urbane – Proposte per la Costa dalmata).
We can then identify some different subsystems inside the documents archived in More: first of all the ‘real’ Nodi urbani (1964/67) that can be related to the theory of exploration and study of urban space conducted within the course of design and planning between 1965 and 1967 with Blasi, Banfi, Seassaro e Stevan (see also La traducibilità dei nessi intercorrenti all'interno di una struttura urbana in visualizzazioni spaziali, Ares, Milano 1966). Again the series is documented both at the Centre Pompidou and inside the MoRE museum where the 10 drawings (the sketch also present in the Parisian collection is 1-10D-PIETRA.tif) constitute a development of the underground routes for the sculptures of Kengiro Azuma, Giacomo Benevelli and Giancarlo Marchese and a reworking of the Tuberie series that, as mentioned, find a testing time in the proposal for the Brescia Monument. A common feature of these designs is the shaping and articulation of emergencies inside a difficult to decipher urbanized area , that the dense texture of signs of La Pietra is trying to translate.
The paths and interconnections that qualify the territory define complex structures that appear to be a declination of one of the central themes of the architectural debate of the late sixties, the one about megastructures.
The final transition from primordial habitable sculptures to these variations around the megastructural theme can be identified in the proposals developed on the occasion of the participation at the 1968 international meeting in Vela Luka, on the island of Korcula, a seminar sponsored by a group of Dalmatian artists and coordinated by Peter and Kossa Omckus (6.4A_ULP.tif, 6.48_ULP.tif, 31_nodi urbani.tif) that La Pietra attended together with other Italian artists (Paolo Scheggi, Achille Perilli, Sacripanti), confronting himself with many different members of the international architectural and artistic researches, an opportunity to "implement utopia", as Gillo Dorfles wrote in the journal "In" (1970)
X-ray Diffraction and <sup>13</sup>C Solid-State NMR Studies of the Dimethylformamide Solvate of Tetra(C-undecyl)calix[4]resorcinarene
No full textLipophilic tetra(C-undecyl)calix[4]resorcinarene obtained from resorcinol and lauryl aldehyde forms solvates
with many organic solvents. Particularly good quality crystals are obtained from dimethylformamide. Single-crystal X-ray diffraction (XRD) analysis of the solvate shows that the calix[4]resorcinarene molecules form
centrosymmetric dimers held by van der Waals interactions of the C-undecyl aliphatic chains. The dimers are
associated into layers with hydroxyl groups at the surfaces. Three types of solvent molecules are embedded
in the crystal lattice: disordered isolated molecules located just above the cavities formed by the resorcinol
units, clusters of four DMF molecules located between the calixarene layers, and single DMF molecules
located inside the layers close to the alkyl chains. The solvent molecules join the layers of calix[4]resorcinarenes
by means of various hydrogen bonds. The 13C CP/MAS spectra are in agreement with the XRD results
Performance assessment in fingerprinting and multi component quantitative NMR analyses
No full textAn inter-laboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for
multi component quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. 36 NMR data sets (corresponding to
1260 NMR spectra) were produced by 30 participants using 34 NMR spectrometers. The calibration line method was chosen for the
quantification of a five-component model mixture. Results show that quantitative NMR is a robust quantification tool and that 26
out of 36 data sets resulted in statistically equivalent calibration lines for all considered NMR signals. The performance of each laboratory
was assessed by means of a new performance index (named Qp-score) which is related to the difference between the experimental
and the consensus values of the slope of the calibration lines. Laboratories endowed with Qp-score falling within the suitable
acceptability range are qualified to produce NMR spectra that can be considered statistically equivalent in terms of relative intensities
of the signals. In addition, the specific response of nuclei to the experimental excitation/relaxation conditions was addressed
by means of the parameter named NR. NR is related to the difference between the theoretical and the consensus slopes of
the calibration lines and is specific for each signal produced by a well-defined set of acquisition parameter
A Contribution to the Harmonization of Non-targeted NMR Methods for Data-Driven Food Authenticity Assessment
No full textSpectroscopic non-targeted methods are gaining ever-growing importance in quality control and authenticity assessment of food products because of their strong potential for identification of specific features of the products by data-driven classifiers. One of the factors hampering the diffusion of spectroscopic non-targeted methods and data-driven classifiers is the lack of harmonized guidelines for their development and validation. In particular, to date, neither conditions to directly compare spectra recorded by different spectrometers nor studies demonstrating the statistical equivalence of the spectra are available. Among the spectroscopic analytical techniques suitable for the development of non-targeted methods, nuclear magnetic resonance (NMR) offers the unique opportunity to generate statistically equivalent signals. In this paper, the feasibility of NMR spectroscopy to generate statistically equivalent NMR signals from a number of different spectrometers was demonstrated for complex mixtures (aqueous extracts of wheat and flour) by organizing an inter-laboratory comparison involving 36 NMR spectrometers. Univariate statistics along with multivariate analysis were exploited to establish unbiased criteria for assessing the statistical equivalence of the NMR signals. The aspects affecting the signal equivalence were investigated, and possible solutions to reduce the extent of the human error were proposed and applied with satisfactory results. This study furnishes the scientific community with an appropriate and easy procedure to validate non-targeted NMR methods and provides error values to be used as a reference for future studies
Formation of Double Cubanes [Sn<sub>7</sub>(NR)<sub>8</sub>] in the Reactions of Pyridyl and Pyrimidinyl Amines with Sn(NMe<sub>2</sub>)<sub>2</sub>: A Synthetic and Theoretical Study<sup>†</sup>
No full textIn contrast to the reactions of Sn(NMe2)2 with unfunctionalized primary amines (RNH2), which yield the simple
imido SnII cubanes [SnNR]4, the reactions of 2-pyridyl or 2-pyrimidinyl amines give the mixed-oxidation-state SnII/SnIV double cubanes [Sn7(NR)8]. In addition to [Sn7{2-N(5-Mepy)}8]·2thf (1·2thf) (py = pyridine) and [Sn7{2-N(pm)}8]·0.33thf (2·0.33thf) (pm = pyrimidine), which were communicated previously, the syntheses and structures
of the new complexes [Sn7{2-N(4-Mepm)}8]·2thf (3·2thf), [Sn7{2-N(4,6-Me2pm)}8]·4thf (4·4thf), [Sn7{2-N(4-Me-6-MeO-pm)}8] (5), and [Sn7{2-N(4-MeO-6-MeO-pm)}8] (6) are reported. Model DFT calculations on the reactions
of Sn(NMe2)2 with 2-pmNH2 or PhNH2, producing the cubanes [Sn{2-N(pm)}]4 and [SnNPh]4 (respectively), and
the corresponding double cubanes [Sn7{2-N(pm)}8] and [Sn7(NPh)8], show that the presence of intramolecular
Sn···N bonding which spans the cubane halves of the complexes is crucial to the formation of the double-cubane
structure
