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81.
Presciutti F Capitani D Sgamellotti A Brunetti BG Costantino F Viel S Segre A 《The journal of physical chemistry. B》2005,109(47):22147-22158
The aim of this study is to clarify the structure of an iron-rich clay and the structural changes involved in the firing process as a preliminary step to get information on ancient ceramic technology. To this purpose, illite-rich clay samples fired at different temperatures were characterized using a multitechnique approach, i.e., by electron paramagnetic resonance, scanning electron microscopy with electron dispersion X-ray spectrometry, X-ray powder diffraction, magic angle spinning and multiple quantum magic angle spinning NMR. During firing, four main reaction processes occur: dehydration, dehydroxylation, structural breakdown, and recrystallization. When the results are combined from all characterization methods, the following conclusions could be obtained. Interlayer H2O is located close to aluminum in octahedral sites and is driven off at temperatures lower than 600 degrees C. Between 600 and 700 degrees C dehydroxylation occurs whereas, between 800 and 900 degrees C, the aluminum in octahedral sites disappears, due to the breakdown of the illite structure, and all iron present is oxidized to Fe3+. In samples fired at 1000 and 1100 degrees C iron clustering was observed as well as large single crystals of iron with the occurrence of ferro- or ferrimagnetic effects. Below 900 degrees C the aluminum in octahedral sites presents a continuous distribution of chemical shift, suggesting the presence of slightly distorted sites. Finally, over the whole temperature range, the presence of at least two tetrahedral aluminum sites was revealed, characterized by different values of the quadrupolar coupling constant. 相似文献
82.
This paper is concerned with the low Mach number limit for the compressible Navier-Stokes equations in an exterior domain.We present here an approach based on Strichartz estimate defined on a non trapp... 相似文献
83.
Advances in Data Analysis and Classification - A CLUstering model for SKew-symmetric data including EXTernal information (CLUSKEXT) is proposed, which relies on the decomposition of a... 相似文献
84.
85.
We study some extended Lagrange interpolation processes based on the zeros of the generalized Laguerre polynomials. We give necessary and sufficient conditions such that the convergence of these processes, in suitable L p weighted spaces on the real semiaxis, is assured for 1<p<+∞. 相似文献
86.
Donatella Bongiorno 《Czechoslovak Mathematical Journal》2004,54(3):717-725
Riemann-type definitions of the Riemann improper integral and of the Lebesgue improper integral are obtained from McShane's definition of the Lebesgue integral by imposing a Kurzweil-Henstock's condition on McShane's partitions. 相似文献
87.
Proietti N Presciutti F Di Tullio V Doherty B Marinelli AM Provinciali B Macchioni N Capitani D Miliani C 《Analytical and bioanalytical chemistry》2011,399(9):3117-3131
A multi-technique approach was employed to study a decorated Egyptian wooden sarcophagus (XXV–XXVI dynasty, Third Intermediate
Period), belonging to the Museo del Vicino Oriente of the Sapienza University of Rome. Portable non-invasive unilateral NMR
was applied to evaluate the conservation state of the sarcophagus. Moreover, using unilateral NMR, a non-invasive analytical
protocol was established to detect the presence of organic substances on the surface and/or embedded in the wooden matrix.
This protocol allowed for an educated sampling campaign aimed at further investigating the state of degradation of the wood
and the presence of organic substances by 13C cross polarization magic angle spinning (CPMAS) NMR spectroscopy. The composition of the painted layer was analysed by optical
microscopy (OM), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), Raman and surface enhanced (resonance)
Raman spectroscopy (SERS/SERRS), infrared and GC–MS techniques, evidencing original components such as clay minerals, Egyptian
green, indigo, natural gums, and also highlighting restoration pigments and alteration compounds. The identification of the
wood, of great value for the reconstruction of the history of the artwork, was achieved by means of optical microscopy. 相似文献
88.
Di Tullio V Proietti N Capitani D Nicolini I Mecchi AM 《Analytical and bioanalytical chemistry》2011,400(9):3151-3164
Hydrophobic treatment is one of the most important interventions usually carried out in the conservation of stone artifacts
and monuments. The analytical study reported in this paper was aimed at answering general questions such as the penetration
depth of a hydrophobic treatment into a porous material, its capability to impair the water absorption, how the presence of
a treatment may change the open porosity available to the water, and how a treatment may affect the diffusion of water inside
a porous structure. Also, inhomogeneities in treated stones due to sharp variations of the amount of the absorbed product
in the porous material were evidenced and scaled. The results of this fully non-invasive analytical study were rationalized
in terms of new parameters obtained by a suitable process of nuclear magnetic resonance data. These analytical parameters
reported here for the first time, namely the hydrophobic efficiency, the penetration depth, and angles describing changes
in slope in depth profiles, gave important information in assessing the performance of a treatment. 相似文献
89.
A new method for the determination of biogenic amines in cheese by LC with evaporative light scattering detector 总被引:1,自引:0,他引:1
Restuccia D Spizzirri UG Puoci F Cirillo G Curcio M Parisi OI Iemma F Picci N 《Talanta》2011,85(1):363-369
This paper presents a new LC method with evaporative light scattering detection (ELSD), for the separation and determination of the biogenic amines (histamine, spermidine, spermine, tyramine, putrescine and β-phenylethylamine) which are commonly present in cheese, as their presence and relative amounts give useful information about freshness, level of maturing, quality of storage and cheese authentication. The LC-ELSD method is validated by comparison of the results with those obtained through LC-UV determination, based on a pre-column dansyl chloride derivatisation step. The obtained data demonstrate that both methods can be interchangeably used for biogenic amines determination in cheese. The new LC-ELSD method shows good precision and permits to achieve, for standard solutions, limit of detection (LOD) values ranging from 1.4 to 3.6 mg L−1 and limit of quantitation (LOQ) values ranging from 3.6 to 9.3 mg L−1. The whole methodology, comprehensive of the homogenization-extraction process and LC-ELSD analysis, has been applied in the analysis of a typical Calabria (Southern Italy) POD cheese, known as Caciocavallo Silano. The most aboundant amine found was histamine, followed, in decreasing order, by tyramine, spermine, putrescine, β-phenylethylamine and spermidine, for a total amount of 127 mg kg−1. This value does not represent a possible risk for consumer health, according to the toxicity levels reported in literature and regarded as acceptable. 相似文献