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91.
Jean-François Babadjian Margarida Baía Pedro M. Santos 《Applied Mathematics and Optimization》2008,57(1):69-97
This work is devoted to the study of two-scale gradient Young measures naturally arising in nonlinear elasticity homogenization problems. Precisely, a characterization of this class of measures is derived and an integral representation formula for homogenized energies, whose integrands satisfy very weak regularity assumptions, is obtained in terms of two-scale gradient Young measures. 相似文献
92.
The diastereo- and enantioselectivity obtained experimentally by Enders et all. (Enders, D.; Niemeier, O.; Straver, S. Synlett 2006, 3399-3402) in the amine-catalyzed intramolecular 5-enolexo aldolization of 1,6-dicarbonyl compounds were fully rationalized using density functional theory methods. A polarizable continuum model was used to describe solvent effects. While 6-enolexo aldolizations are well described by Houk's model on the basis of steric and electrostatic contacts, the main factors conditioning the final selectivity in 5-enolexo processes are calculated to be quite different. Thus, the selectivity results from the summation of several small electrostatic contacts with an unexpected HOMO electronic overlapping plus the ring strain of the five-membered ring, whereas steric effects seem to be unimportant. Our results indicate, in contrast with 6-enolexo processes, that high selectivities are not expected in this type of reaction and that the experimental selectivity shall be very dependent on the reaction conditions, as known experimental results seem to suggest. 7-enolendo products are not expected, as they are predicted to be formed by higher energetic transition states. Variable reaction rates, experimentally observed with different catalysts, are suggested to be mainly a result of different catalyst solubilities. 相似文献
93.
Margarida Moreira dos Santos Margarida João Queiroz Pedro V. Baptista 《Journal of nanoparticle research》2012,14(5):859
A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds
with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy
(Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics
to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of
antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial
cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum
of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles
with a size distribution of 32.5 ± 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a β-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle–antibiotic conjugates
towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics. 相似文献
94.
M.S. Baptista E.J. Ngamga Paulo R.F. Pinto Margarida Brito 《Physics letters. A》2010,374(9):1135-1140
Observing how long a dynamical system takes to return to some state is one of the most simple ways to model and quantify its dynamics from data series. This work proposes two formulas to estimate the KS entropy and a lower bound of it, a sort of Shannon's entropy per unit of time, from the recurrence times of chaotic systems. One formula provides the KS entropy and is more theoretically oriented since one has to measure also the low probable very long returns. The other provides a lower bound for the KS entropy and is more experimentally oriented since one has to measure only the high probable short returns. These formulas are a consequence of the fact that the series of returns do contain the same information of the trajectory that generated it. That suggests that recurrence times might be valuable when making models of complex systems. 相似文献
95.
The first unequivocal thermochemical/calorimetric determination of the enthalpies of combustion, phase change, and formation of a pair of (E)- and (Z)-disubstituted olefins of the type XCH = CHX, where X is an electron withdrawing group, is reported in this paper for the isomeric species dimethyl fumarate and dimethyl maleate (X = COOCH3). The corresponding density functional calculations, corrected for vibrational and thermal effects, confirm that the former isomer is more stable by some 30 kJ mol-1. 相似文献
96.
Vieira Manuel V. C. Carvalho Margarida 《4OR: A Quarterly Journal of Operations Research》2023,21(3):491-512
4OR - Motivated by a real-world application, we present a multi-container loading problem with 3-open dimensions. We formulate it as a biobjective mixed-integer nonlinear program with lexicographic... 相似文献
97.
98.
Antnio P. Gonalves Laura C. J. Pereira Paulo A. S. Silva Margarida Godinho Manuel Almeida Moshe Kuznietz 《Journal of magnetism and magnetic materials》2000,210(1-3)
Polycrystalline (U0.50Dy0.50)Ni2B2C solid solution was prepared and found by X-ray diffraction to crystallize in BCT LuNi2B2C-type structure (space group I4/mmm) of the end compounds UNi2B2C and DyNi2B2C. AC susceptibility and magnetization show paramagnetic behavior down to 6.5 K, with the values θ=−5(5) K and μeff=7.7(1) μB, compatible with those of the end compounds, and indicate possible cooperative phenomena at lower temperatures. The observed paramagnetism, at variance with antiferromagnetic ordering in (Pr0.50Dy0.50)Ni2B2C, is attributed to a directional frustration of the magnetic moments on the (U,Dy) site. 相似文献
99.
100.
Sílvia M. G. Rodrigues Margarida Facão Mário F. S. Ferreira 《Fiber and Integrated Optics》2015,34(1-2):76-89
AbstractKagome hollow-core photonic crystal fibers were found to be ideal for the occurrence of ultrafast non-linear optics. This article reports the optimal conditions for the generation of ultraviolet light using a gas filled kagome hollow-core-photonic crystal fiber. It is shown that by changing the pressure of the gas and the input pulse characteristics, the efficiency of conversion and quality of ultraviolet light can be improved, as well as tuning its central frequency. Results suggest that a highly coherent and tunable ultraviolet light source can be constructed, which can find numerous applications. 相似文献