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191.
Bicchieri M Monti M Piantanida G Pinzari F Iannuccelli S Sotgiu S Tireni L 《Analytical and bioanalytical chemistry》2012,402(4):1517-1528
The Italian dialect poet Cesare Pascarella travelled all around the world, noting down in notebooks his keen and caustic observations,
and drawing sketches that are a visual reportage of his journeys. The sketches were mounted as a random collage over acidic
cardboards that were exposed to direct sunlight in his studio. Their poor state of conservation is related to the use of modern
paper: chemical instability of raw materials caused acidification and strong oxidation of the support, with intense yellowing
of the surfaces and brittleness of the paper. To ensure future preservation of the drawings, chemical stabilisation with simultaneous
alcoholic treatment by deacidification (calcium propionate) and reduction (borane tert-butylamine complex) appeared necessary. To verify its applicability, it was indispensible to characterise the support and
identify the nature of all the graphic media. The use of Raman, Infrared, X-ray fluorescence spectroscopies and scanning electron
microscopy coupled with X-ray microanalysis allowed us to clear the problems related to the different penetration depth of
each analytical technique and the different responses of pigments/dyes to each spectroscopy. The palette, how it varied along
the journeys, the different supports used and preparations were completely identified showing a choice of colours compatible
with the reduction treatment. 相似文献
192.
Flavia Giannetti 《manuscripta mathematica》2011,136(1-2):143-154
We study the lower semicontinuity of functionals of the form $$ \mathcal{F}(u)=\int\limits_{\Omega}f(x, u(x), \mathcal{L}u(x))\,dx $$ with respect to the weak convergence in W k,p (??), where ${{\mathcal L}}$ is a linear differential operator of order k??? 1 and f is quasiconvex with respect to the operator ${{\mathcal L}}$ and satisfies 0??? f(x, s, ??) ?? c (1?+ |??| q ) with q ?? p?>?1. 相似文献
193.
Ivano Marchi Véronique Viette Flavia Badoud Marc Fathi Martial Saugy Serge Rudaz Jean-Luc Veuthey 《Journal of chromatography. A》2010,1217(25):4071-4078
An exhaustive classification of matrix effects occurring when a sample preparation is performed prior to liquid-chromatography coupled to mass spectrometry (LC–MS) analyses was proposed. A total of eight different situations were identified allowing the recognition of the matrix effect typology via the calculation of four recovery values. A set of 198 compounds was used to evaluate matrix effects after solid phase extraction (SPE) from plasma or urine samples prior to LC–ESI-MS analysis. Matrix effect identification was achieved for all compounds and classified through an organization chart. Only 17% of the tested compounds did not present significant matrix effects. 相似文献
194.
Flavia Pop Crina Socaci Anamaria Terec Eric Condamine Richard Attila Varga Ciprian I. Raţ Jean Roncali Ion Grosu 《Tetrahedron》2012,68(41):8581-8588
Hay synthesis of cryptands and bismacrocycles starting from tripodands with cyanuric and isocyanuric cores is reported. The structure of the compounds is revealed by X-ray diffraction, NMR spectrometry and MS investigations. DNMR experiments carried out with bismacrocycles indicated the flipping of the rings and the free-energy barrier for the conformational process could be determined in one case. 相似文献
195.
196.
197.
Naidek KP Bianconi F da Rocha TC Zanchet D Bonacin JA Novak MA Vaz Md Winnischofer H 《Journal of colloid and interface science》2011,358(1):39-46
We synthesized magnetic spinel ferrites from trimetallic single-source precursors. Fe(II), Co(II), and Ni(II) ferrite nanoparticles in the range of 9-25 nm were synthesized by solvothermal decomposition of trimetallic acetate complex precursors in benzyl ether in the presence of oleic acid and oleylamine, using 1,2-dodecanediol as the reducing agent. For comparison, spinel ferrite nanoparticles were synthesized by stoichiometric mixtures of metal acetate or acetylacetonate salts. The nanoparticles (NP) were characterized by TEM, DLS, powder XRD, and Raman spectroscopy; and their magnetic properties were characterized by ZFC-FC and M(H) measurements. The ferrite-NP were more homogeneous and had a narrower size distribution when trimetallic complexes were used as precursors. As a consequence, the magnetic properties of these ferrite-NP are closer to the aimed room temperature superparamagnetic behavior, than are those of other ferrites obtained by a mixture of salts. 相似文献
198.
A field amplified sample injection (FASI) capillary electrophoresis method with UV detection was developed for the separation and detection of carnosine-related peptides carnosine (Car), anserine (Ans) and homocarnosine (Hcar). The imidazole dipeptides were baseline-separated within 10 min by using 50 mmol/L Tris phosphate pH 2.2 as running buffer. The samples were diluted in water and directly injected on the capillary without complex cleanup and/or sample derivatization procedures. Using the electrokinetic injection, a sensitivity improvement of about 500-fold was achieved without any loss of separation efficiency if compared to the conventional sample injection. The detection limits for carnosine, anserine, and homocarnosine were between 0.4 and 0.5 nmol/L, thus improving of 10-100-fold the LOD of previous described methods based on laser induced fluorescence or chemiluminescence detection. This method has been applied to the analysis of homogenized rat tissue (heart, muscle and brain) and human cerebrospinal fluid (CSF). 相似文献
199.
Nastri F Lista L Ringhieri P Vitale R Faiella M Andreozzi C Travascio P Maglio O Lombardi A Pavone V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4444-4453
Mimicking enzymes with alternative molecules represents an important objective in synthetic biology, aimed to obtain new chemical entities for specific applications. This objective is hampered by the large size and complexity of enzymes. The manipulation of their structures often leads to a reduction of enzyme activity. Herein, we describe the spectroscopic and functional characterization of Fe(III)-mimochrome VI, a 3.5 kDa synthetic heme-protein model, which displays a peroxidase-like catalytic activity. By the use of hydrogen peroxide, Fe(III)-mimochrome VI efficiently catalyzes the oxidation of several substrates, with a typical Michaelis-Menten mechanism and with several multiple turnovers. The catalytic efficiency of Fe(III)-mimochrome VI in the oxidation of 2,2'-azino-di(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) and guaiacol (k(cat)/K(m)=4417 and 870 mM(-1) s(-1), respectively) is comparable to that of native horseradish peroxidase (HRP, k(cat)/K(m)=5125 and 500 mM(-1) s(-1), respectively). Fe(III)-mimochrome VI also converts phenol to 4- and 2-nitrophenol in the presence of NO(2) (-) and H(2) O(2) in high yields. These results demonstrate that small synthetic peptides can impart high enzyme activities to metal cofactors, and anticipate the possibility of constructing new biocatalysts tailored to specific functions. 相似文献
200.
This paper reports efficient procedures for the preparation of optically active dibromide, diazide, diamine, and unsaturated diesters derived from a chiral bicyclic diol with C2 symmetry namely (11R,12R)-9,10-dihydro-9,10-ethaneanthracene-11,12-dimethanol 3. Esterification of 3 with saturated and unsaturated carboxylic acids and acids chlorides leads to the corresponding normal-, olefinic- and acetylenic diesters in average yields of 81%. Also more efficient techniques for the preparation of starting diol 3 in higher yields as well as for a very simple separation of DCU (N,N′-dicyclohexylurea) from reactions carried out following the DCC/DMAP method are described. 相似文献