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91.
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
92.
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
93.
Micaela Hernández-Sandoval María J. Rosales-Hoz Noemi Andrade Gloria Sánchez-Cabrera 《Journal of organometallic chemistry》2011,696(25):4070-4078
The reaction of compound [Ru3(CO)10(μ-Cl)(μ-AuPPh3)] (1) with terminal alkynes HCCR; (R = C6H4-4-CH3, C6H3-2,5-(CH3)2, C6H2-2,4,5-(CH3)3, C(CH3) = CH2, Si(CH3)3), under very mild conditions yielded isostructural compounds [Ru3(CO)9(μ-AuPPh3)(μ3-η2-⊥-CCR)] (R = C6H4-4-CH3 (2), C6H3-2,5-(CH3)2 (3), C6H2-2,4,5-(CH3)3 (4), C(CH3)CH2 (5), Si(CH3)3) (6)) respectively; where the alkynes suffer oxidative additions to the metallic fragment coordinating as acetylide groups in a μ3-η2-perpendicular fashion by breaking the C(sp)-H bond of the alkynes. The AuPPh3 fragment remains without change in all compounds. All of these clusters have been characterized in solution by i.r. and n.m.r. spectroscopy and their structures have been established by single crystal X-ray diffraction studies. 相似文献
94.
Several pyridazin-3(2H)-one derivatives were synthesized starting from alkyl furans using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of the synthetic strategy followed. For all pyridazinones reported, a complete assignment of the (1)H and (13)C NMR spectra using one- and two-dimensional NMR spectroscopic methods, which included NOE, DEPT, COSY, HSQC and HMBC experiments, was accomplished. Correlations between the chemical shifts of the heterocyclic ring atoms and substituents at N-2 and C-6 were analyzed. 相似文献
95.
The objective of this article was to investigate the effect of carbide and polymer burs caries removal methods on the bond strength of different adhesives to dentin. Resin restorations were performed in sound and caries-affected dentin, after using polymer or carbide burs and bonding with four different adhesive (Single bond, SB; Clearfil SE bond, SEB; FL-Bond II, FLB; and Fuji II-LC, FUJI). Microtensile bond strength (MTBS) was measured. Data were analyzed with ANOVA and Student-Newman-Keuls tests. Debonded surfaces were observed by scanning electron microscopy. Bonded interfaces were examined using light microscopy (Masson's trichrome staining). In sound dentin, MTBS was similar for SEB and SB, and higher than that of FLB and FUJI. Bond strength to carbide bur prepared dentin was similar for SB, SEB, and FLB; FUJI presented the lowest. SB applied on polymer bur excavated dentin presented similar values to those of the carbide bur group; MTBS attained by SEB, FLB, and FUJI decreased when bonding to dentin treated with polymer burs; FUJI yielded pretesting failures in all specimens. Polymer burs created a thick smear layer that was not infiltrated by tested self-etching agents. The bonding effectiveness of self-etching and glass-ionomer-like adhesives to dentin decreased when polymer burs were used. 相似文献
96.
Noemi Proietti Valeria Di Tullio Donatella Capitani Roberta Tomassini Marcella Guiso 《Applied Physics A: Materials Science & Processing》2013,113(4):1009-1017
Nuclear Magnetic Resonance (NMR) methodologies were applied to characterize the constitutive materials and the state of degradation of a contemporary painting. The investigation was mandatory to plan a suitable restoration. Noninvasive, portable NMR allowed the detection of degraded regions of the painting based on the measurement of longitudinal relaxation time. A few samples were investigated by high resolution solid state NMR and NMR in solution, which allowed us to identify the polyurethane constituting the artefact, to investigate the microstructure in detail, and to assess that the degradation process mostly affected the ethylene units used to cap the polypropylene oxide polymeric chain. As a matter of fact, a shortening of longitudinal relaxation time was accompanied by a degradation of ethylene units. The degradation of the inorganic loading was investigated by 27Al MAS, which evidenced the absence of penta-coordinated aluminum in degraded samples. 相似文献
97.
98.
π-complemented algebras are defined as those (not necessarily associative or unital) algebras such that each annihilator ideal is complemented by other annihilator ideal. For a given semiprime algebra A, we discuss the π-complementation of the unitisation algebra A 1 of A. Moreover, if in addition the multiplication algebra ?(A) of A is also semiprime, we study the π-complementation in the algebras ?(A) and ??(A) (the multiplication ideal of A). In associative setting, we prove that A is π-complemented if and only if ??(A) is π-complemented, and that A 1 π-complemented if and only if ?(A) is π-complemented. 相似文献
99.
Sergio Cabello 《Discrete and Computational Geometry》2013,49(2):348-358
We show that, if $\mathrm{P}\not=\mathrm{NP}$ , there is a constant c 0>1 such that there is no c 0-approximation algorithm for the crossing number, even when restricted to 3-regular graphs. 相似文献
100.