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141.
Giorgio Barbieri Rois Benassi Paolo Lazzeretti Luisa Schenetti Ferdinando Taddei 《Magnetic resonance in chemistry : MRC》1975,7(9):451-454
1H chemical shifts of quinoline, quinoline N-oxide and the quinolinium ion were obtained by complete analysis of their NMR spectra and interpreted critically in an attempt to quantify the possible different effects acting on the shielding constant of protons in these systems. Semi-empirical SCF calculations of electron charge densities and ring current contributions were also performed. It was found that the same effects that act on the shielding of protons directly bonded to the heterocyclic system also act, in an attenuated form, on the proton chemical shift of methyl groups in monomethyl derivatives. Vicinal coupling constants were rationalised in terms of π-electron bond order and electro-negativity of neighbouring atoms. 相似文献
142.
We study scalar multivariate non-stationary subdivision schemes with a general integer dilation matrix. We characterize the capability of such schemes to reproduce exponential polynomials in terms of simple algebraic conditions on their symbols. These algebraic conditions provide a useful theoretical tool for checking the reproduction properties of existing schemes and for constructing new schemes with desired reproduction capabilities and other enhanced properties. We illustrate our results with several examples. 相似文献
143.
Equations for the Missing Boundary Values in the Hamiltonian Formulation of Optimal Control Problems
Vicente Costanza Pablo S. Rivadeneira Ruben D. Spies 《Journal of Optimization Theory and Applications》2011,149(1):26-46
Partial differential equations for the unknown final state and initial costate arising in the Hamiltonian formulation of regular
optimal control problems with a quadratic final penalty are found. It is shown that the missing boundary conditions for Hamilton’s
canonical ordinary differential equations satisfy a system of first-order quasilinear vector partial differential equations
(PDEs), when the functional dependence of the H-optimal control in phase-space variables is explicitly known. Their solutions are computed in the context of nonlinear systems
with ℝ
n
-valued states. No special restrictions are imposed on the form of the Lagrangian cost term. Having calculated the initial
values of the costates, the optimal control can then be constructed from on-line integration of the corresponding 2n-dimensional Hamilton ordinary differential equations (ODEs). The off-line procedure requires finding two auxiliary n×n matrices that generalize those appearing in the solution of the differential Riccati equation (DRE) associated with the linear-quadratic
regulator (LQR) problem. In all equations, the independent variables are the finite time-horizon duration T and the final-penalty matrix coefficient S, so their solutions give information on a whole two-parameter family of control problems, which can be used for design purposes.
The mathematical treatment takes advantage from the symplectic structure of the Hamiltonian formalism, which allows one to
reformulate Bellman’s conjectures concerning the “invariant-embedding” methodology for two-point boundary-value problems.
Results for LQR problems are tested against solutions of the associated differential Riccati equation, and the attributes
of the two approaches are illustrated and discussed. Also, nonlinear problems are numerically solved and compared against
those obtained by using shooting techniques. 相似文献
144.
Mileo E Casati C Franchi P Mezzina E Lucarini M 《Organic & biomolecular chemistry》2011,9(8):2920-2924
The first example of paramagnetic rotaxane containing cucurbit[6]urils has been reported and characterized both by ESR and NMR spectroscopy. 相似文献
145.
Clementi C Ciocan V Vagnini M Doherty B Tabasso ML Conti C Brunetti BG Miliani C 《Analytical and bioanalytical chemistry》2011,401(6):1815-1826
The paper reports on the exploitation of an educated multi-technique analytical approach based on a wide non invasive step
followed by a focused micro-destructive step, aimed at the minimally invasive identification of the pigments decorating the
ceiling of the Gilded Vault of the Domus Aurea in Rome. The combination of elemental analysis with molecular characterization provided by X-ray fluorescence and UV–vis
spectroscopies, respectively, allowed for the in situ non-invasive identification of a remarkable number of pigments, namely
Egyptian blue, green earth, cinnabar, red ochre and an anthraquinonic lake. The study was completed with the Raman analysis
of two bulk samples, in particular, SERS measurements allowed for the speciation of the anthraquinonic pigment. Elemental
mapping by scanning electron microscopy-energy dispersive spectrometer combined with micro-fluorimetry on cross-section gave
an insight into both the distribution of different blend of pigments and on the nature of the inorganic support of the red
dye. 相似文献
146.
Asger W. Nørgaard Anni Vibenholt Mario Benassi Per Axel Clausen Peder Wolkoff 《Journal of the American Society for Mass Spectrometry》2013,24(7):1090-1096
Limonene and its ozone-initiated reaction products were investigated in situ by low temperature plasma (LTP) ionization quadrupole time-of-flight (QTOF) mass spectrometry. Helium was used as discharge gas and the protruding plasma generated ~850 ppb ozone in front of the glass tube by reaction with the ambient oxygen. Limonene applied to filter paper was placed in front of the LTP afterglow and the MS inlet. Instantly, a wide range of reaction products appeared, ranging from m/z 139 to ca. 1000 in the positive mode and m/z 115 to ca. 600 in the negative mode. Key monomeric oxidation products including levulinic acid, 4-acetyl-1-methylcyclohexene, limonene oxide, 3-isopropenyl-6-oxo-heptanal, and the secondary ozonide of limonene could be identified by collision-induced dissociation. Oligomeric products ranged from the nonoxidized dimer of limonene (C20H30) and up to the hexamer with 10 oxygen atoms (C60H90O10). The use of LTP for in situ ozonolysis and ionization represents a new and versatile approach for the assessment of ozone-initiated terpene chemistry. Figure
? 相似文献
147.
Brenda Doherty Costanza Miliani Ina Vanden Berghe Antonio Sgamellotti Brunetto Giovanni Brunetti 《Journal of Raman spectroscopy : JRS》2008,39(5):638-645
The objective of this study was to evaluate the use of micro‐Raman spectroscopy as a non‐invasive vibrational spectroscopic technique applied to the examination of wool samples, which may be applied to textile materials of cultural heritage interest. In this work, a selection of wool materials were primarily investigated in their unaged states through the utility of a natural wool reference together with selected samples dyed with different natural colorants, namely woad, weld and madder. The identification of the main modes of vibration of the wool fibre keratin was assessed in all the samples, which aided the determination of the changes within the protein structure, in particular, through the cysteine and peptide cross‐linkages brought about by the addition of the dyes that can produce effects similar to degradation. The dye too was assessed importantly to enable its identification through its characteristic scattering or fluorescence emissions on a woollen matrix, as well as to ascertain whether a uniform covering across the surface of the wool was achieved or not. Regarding the artificial degradation of the samples it was possible to observe numerous modifications within the molecular structure of the wool, in particular, within the amide I, C H bending, amide III and S‐S stretchings along with the physical photo‐yellowing of fibres given by the presence of lipids dispersed across the surface of the wool. The effects of ageing on the dyed samples were also investigated, indicating that many of the bands relative to the colorants were still present, yet so too were numerous vibrations from the wool that also indicated a certain level of stress and degradation to the underlying wool. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
148.
G. Bertelli R. Benassi R. Marchini G. Camino L. Costa M. P. Luda 《Macromolecular Symposia》1993,74(1):111-116
The combustion behaviour of polymeric materials either fire retarded or not, burning in the Glow Wire and UL 94 tests, was characterised by means of thermography. It is shown that the distribution of temperatures in the gas and condensed phase of the burning specimen thus recorded, supplies fundamental complementary information for the characterisation of the combustion process. 相似文献
149.
Dr. Costanza Vanni Prof. Francesca Cardona Dr. Francesca Clemente Prof. Amelia Morrone Dr. Martina Raudino Dr. Moira Ambrosi Prof. Pierandrea Lo Nostro Dr. Camilla Matassini 《European journal of organic chemistry》2023,26(11):e202200911
Pharmacological chaperones (PCs) can restore correct enzymatic activity at sub-inhibitory concentrations and are considered an emerging therapy for Gaucher Disease (GD). Amphiphilic PCs show more favourable cross-membrane properties and have a higher activity on cells than hydrophilic PCs. To investigate whether the biological activity of amphiphilic iminosugars is related to their state as monomers or as micellar aggregates, we synthesized some novel N-alkylated iminosugars and performed physico-chemical characterizations in the solid state and in aqueous dispersion of the best compound in terms of biological activity. The results suggest that the C12 N-alkylated iminosugar 10 exerts its biological activity in the monomeric state, and that the low cell viability observed in the presence of a 50 μM concentration of compound 10 is not related to the formation of micellar aggregates in solution. 相似文献