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1.
Togashi DM Romão RI Gonçalves da Silva AM Sobral AJ Costa SM 《Physical chemistry chemical physics : PCCP》2005,7(22):3874-3883
Langmuir monolayers (LM) and Langmuir-Blodgett (LB) films of pure lipophilic meso-tetra(4-dodecylaminosulfophenyl)porphyrin (PC12) and mixed with the anionic surfactant sodium hexadecylsulfate (SHS) were studied. The molecular packing and structure of PC12 and PC12-4SHS with variable surface pressure were investigated by surface pressure-area measurements, steady-state absorption, fluorescence emission and anisotropy, as well as by fluorescence lifetime imaging microscopy (FLIM). At low surface pressure, the porphyrin molecules are organized with the rings tilted on the water surface whereas at high surface pressure the porphyrin rings achieve a more perpendicular arrangement. Using the FLIM images a gradual change of aggregates into large "islands" is observed. Different patterns are observed in the pure PC12 multilayer films (n = 3 and 5) with ordered patches superimposed which are not observed in the PC12-4SHS multilayer LB films. 相似文献
2.
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
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Given a graph G = (V, E), the maximum leaf spanning tree problem (MLSTP) is to find a spanning tree of G with as many leaves as possible. The problem is easy to solve when G is complete. However, for the general case, when the graph is sparse, it is proven to be NP-hard. In this paper, two reformulations are proposed for the problem. The first one is a reinforced directed graph version
of a formulation found in the literature. The second recasts the problem as a Steiner arborescence problem over an associated
directed graph. Branch-and-Cut algorithms are implemented for these two reformulations. Additionally, we also implemented
an improved version of a MLSTP Branch-and-Bound algorithm, suggested in the literature. All of these algorithms benefit from
pre-processing tests and a heuristic suggested in this paper. Computational comparisons between the three algorithms indicate
that the one associated with the first reformulation is the overall best. It was shown to be faster than the other two algorithms
and is capable of solving much larger MLSTP instances than previously attempted in the literature. 相似文献
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We propose a hybrid GRASP and ILS based heuristic for the diameter constrained minimum spanning tree problem. The latter typically
models network design applications where, under a given quality requirement, all vertices must be connected at minimum cost.
An adaptation of the one time tree heuristic is used to build feasible diameter constrained spanning trees. Solutions thus
obtained are then attempted to be improved through local search. Four different neighborhoods are investigated, in a scheme
similar to VND. Upper bounds within 2% of optimality were obtained for problems in two test sets from the literature. Additionally,
upper bounds stronger than those previously obtained in the literature are reported for OR-Library instances. 相似文献
8.
Ana T. Marques Joana A. Silva Manuela Ramos Silva Ana Matos Beja Licinia L. G. Justino Abilio J. F. N. Sobral 《Journal of chemical crystallography》2008,38(4):295-299
Abstract 2-Methoxy-5-phenylaniline, a promissor monomer for PANI studies, has been characterized by single-crystal X-ray diffraction
at two temperatures: orthorhombic, space group P212121, Z = 12 with a = 5.9900(2) ?, b = 20.4873(6) ?, c = 26.3727(8) ? and R = 0.0868 for 293(2) K and a = 5.8337(9) ?, b = 20.4428(31) ?, c = 26.0773(40) ? and R = 0.0669 for 120(2) K. There are three independent molecules in the unit cell. One of them is approximately planar, the other
two have the phenyl rings rotated. At room temperature the two latter molecules are joined in dimers through H-bonds and at
low temperature the same molecules are joined in columns that run along the a-axis.
Index Abstract
X-ray Diffraction and DFT Studies of 2-Methoxy-5-phenylaniline
Ana T. Marques, Joana A. Silva, Manuela Ramos Silva, Ana Matos Beja, Licinia L. G. Justino, Abilio J. F. N. Sobral
2-Methoxy-5-phenylaniline, a promissor monomer for PANI studies, has been characterized by single-crystal X-ray diffraction
at 293(2) K and 120(2) K. The three independent molecules in the unit cell show different conformations and establish distinct
intermolecular H-bonds.
相似文献
9.
Abilio J.F.N. Sobral Susana M. Melo Raquel Teixeira Silvia M.B. Costa 《Tetrahedron letters》2007,48(18):3145-3149
Monofunctionalisation of meso-tetrakis-porphyrins through introduction of a carboxylic group in the meso position of the phenyl group confers the necessary characteristics to anchor them through stable amide bonds to functionalised supports or to molecules. In this Letter we describe the synthesis, characterisation and photophysical evaluation of such a functionalised flexible dimeric porphyrin, bis-(meso-tetrakis-5,10,15-triphenyl-20-(p-carboxyphenyl)-porphyrinyl)-1,6-hexanediamide. 相似文献
10.
Regalado EL Rodríguez M Menéndez R Fernandez X Hernández I Morales RA Fernández MD Thomas OP Pino JA Concepción AR Laguna A 《Photochemistry and photobiology》2011,87(5):1058-1066
The apolar fraction F1 of Thalassia testudinum was chemically characterized by gas chromatography-mass spectrometry, which led to the identification of 43 metabolites, all of them reported for the first time in the genus Thalassia. More than 80% of the F1 composition was constituted by aromatic metabolites including the major components 1,1-bis(p-tolyl)ethane (6.0%), 4,4'-diisopropylbiphenyl (4.8%) and a 1,1-bis(p-tolyl)ethane isomer (4.7%). This lipophilic fraction was assayed for its antioxidant effects and skin protective action. In vitro assays showed that F1 strongly scavenged DPPH* (IC(50) 312.0 ± 8.0 μg mL(-1)), hydroxyl (IC(50) 23.8 ± 0.5 μg mL(-1)) and peroxyl radical (IC(50) 6.6 ± 0.3 μg mL(-1) ), as well as superoxide anion (IC(50) 50.0 ± 0.7 μg mL(-1)). Also, F1 markedly inhibited the spontaneous lipid peroxidation (LPO) in brain homogenates (IC(50) 93.0 ± 6.0 μg mL(-1)) and the LPS-stimulated nitrite generation on RAW624.7 macrophages (58.6 ± 3.2%, 400 μg mL(-1)). In agreement with these findings, its topical application at 250 and 500 μg cm(-2) strikingly reduced skin damage on mice exposed to acute UVB radiation by 45% and 70%, respectively and significantly attenuated the LPO developed following the first 48 h after acute exposure to UVB irradiation, as manifested by the decreased malondialdehide level and by the increased of reduced gluthatione content. Our results suggest that F1 may contribute to skin repair by attenuating oxidative stress due to its antioxidant activity. 相似文献