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91.
Pedro Silva Sofia M. Fonseca Cláudia T. Arranja Hugh D. Burrows Ana M. Urbano Abilio J. F. N. Sobral 《Photochemistry and photobiology》2010,86(5):1147-1153
A new 5,10,15,20-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin was prepared by an isocyanate condensation reaction and its photophysical properties fully evaluated, both in terms of photostability and singlet oxygen production. It shows considerably enhanced photostability when compared with the parent 5,10,15,20-tetra-(3-hydroxy-phenyl)-porphyrin, with the photodegradation quantum yields for T(NAF)PP and T(OH)PP being 4.65 × 10−4 and 5.19 × 10−3, respectively. Its photodynamic effect in human carcinoma HT-29 cells was evaluated. The new porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC50 value of 6.80 μg mL−1 for a 24 h incubation. In addition to the potential of this compound, the synthetic route used provides possibilities of extension to a wide range of new sensitizers. 相似文献
92.
Manuel J. S. Monte Luís M. N. B. F. Santos José M. S. Fonseca Carlos A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2010,100(2):465-474
The vapour pressures of six para-substituted benzoic acids were measured using the Knudsen effusion method within the pressure range (0.1–1 Pa) in the following
temperature intervals: 4-hydroxybenzoic acid (365.09–387.28) K; 4-cyanobenzoic acid (355.14–373.28) K; 4-(methylamino)benzoic
acid (359.12–381.29) K; 4-(dimethylamino)benzoic acid (369.29–391.01) K; 4-(acetylamino)benzoic acid (423.10–443.12) K; 4-acetoxybenzoic
acid (351.28–373.27) K. From the temperature dependence of the vapour pressure, the standard molar enthalpy, entropy and Gibbs
energy of sublimation, at the temperature 298.15 K, were derived for each of the studied compounds using estimated values
of the heat capacity differences between the gaseous and the crystalline phases. Equations for estimating the vapour pressure
of para substituted benzoic acids at the temperature of 298.15 K are proposed. 相似文献
93.
Célia Fonseca Guerra Tushar van der Wijst Jordi Poater Marcel Swart F. Matthias Bickelhaupt 《Theoretical chemistry accounts》2010,125(3-6):245-252
We have investigated the performance of the dispersion-corrected density functionals (BLYP-D, BP86-D and PBE-D) and the widely used B3LYP functional for describing the hydrogen bonds and the stacking interactions in DNA base dimers. For the gas-phase situation, the bonding energies have been compared to the best ab initio results available in the literature. All dispersion-corrected functionals reproduce well the ab initio results, whereas B3LYP fails completely for the stacked systems. The use of the proper functional leads us to find minima for the adenine quartets, which are energetically and structurally very different from the C4h structures, and might explain why adenine has to be sandwiched between guanine quartets to form planar adenine quartets. 相似文献
94.
The nucleophilic addition of both silyl ketene acetals and lithium enolates derived from methyl acetate to chiral non-racemic N-(benzyloxyethyl)nitrones has been studied both experimentally and theoretically. Aromatic nitrones showed lower reactivity that aliphatic nitrones and the addition of the silyl ketene acetal led to lower selectivities than the addition of the corresponding lithium enolate. Whereas low selectivity was obtained for the addition of the silyl ketene acetal, only one diastereomer could be detected in all cases for the addition of lithium enolate to aliphatic nitrones. The synthetic utility of the two chiral auxiliaries employed lies in the preparation of enantiomeric compounds. DFT theoretical calculations confirmed the stepwise mechanism for the addition of silyl ketene acetals to nitrones and are in good agreement with the observed experimental results. 相似文献
95.
96.
Carlos M. da Fonseca 《Linear and Multilinear Algebra》2019,67(8):1713-1714
97.
C.M. da Fonseca Dan A. Mazilu Irina Mazilu H. Thomas Williams 《Applied Mathematics Letters》2013,26(12):1206-1211
A straightforward model for deposition and evaporation on discrete cells of a finite array of any dimension leads to a matrix equation involving a Sylvester–Kac type matrix. The eigenvalues and eigenvectors of the general matrix are determined for an arbitrary number of cells. A variety of models to which this solution may be applied are discussed. 相似文献
98.
99.
Fernández-Martínez Pedro Segurado Alba Signes Teresa 《Mediterranean Journal of Mathematics》2016,13(5):2959-2979
We study the behavior of compact operators when we interpolate them by real methods defined through slowly varying functions and rearrangement invariant spaces. We apply these results to prove compactness of certain integral operators acting between grand Lebesgue spaces and between small Lebesgue spaces.
相似文献100.
We review several sufficient conditions for the positive definiteness of a tridiagonal matrix and propose a different approach to the problem, recalling and comprising little-known results on chain sequences. 相似文献