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91.
Quantum accelerator modes have been experimentally observed, and theoretically explained, in the dynamics of kicked cold atoms in the presence of gravity, when the kicking period is close to a half-integer multiple of the Talbot time. We generalize the theory to the case when the kicking period is sufficiently close to any rational multiple of the Talbot time, and thus predict new rich families of experimentally observable quantum accelerator modes. 相似文献
92.
93.
Maria Giorgia Cutrufello Elisabetta Rombi Italo Ferino Danilo Loche Anna Corrias Maria Francesca Casula 《Journal of Sol-Gel Science and Technology》2011,60(3):324-332
Porous nanocomposites made out of nickel dispersed on silica or alumina matrices were prepared as prospective catalysts for
the nitroxidation of hydrocarbons in the form of aerogel or xerogel by adopting either a supercritical or a conventional gel
drying procedure. The structural and textural features of the materials were investigated by X-ray diffraction, transmission
electron microscopy and N2 physisorption and combined to the acid/base and reducibility data as deduced by adsorption microcalorimetry and temperature
programmed reduction (TPR) profiles. The alumina-based samples are made out of nanocrystalline nickel aluminate and are mesoporous,
although the aerogel has larger pore volumes and surface area than the xerogel. On the other hand, in the silica-based samples
nickel oxide nanocrystals are dispersed on amorphous silica, the size of the nanocrystals being around 5 nm in the microporous
xerogel and 14 nm in the mainly mesoporous aerogel. TPR data point out that the alumina-based samples have similar reducibility,
whereas significant differences were observed in the silica-supported composites, the NiO–SiO2 aerogel exhibiting improved reducibility at low temperature. The NO-catalyst interaction was monitored by temperature programmed
NO reaction coupled to mass spectrometry and preliminary tests on the use of the NiO–SiO2 xerogel and aerogel nanocomposites for the catalytic nitroxidation of 1-methyl-naphthalene to 1-naphthonitrile were obtained
in a fixed-bed continuous-flow reactor. The data indicate that the aerogel exhibits larger selectivity than the corresponding
xerogel, pointing out the importance of tuning the sol–gel parameters in the design of porous composite materials for catalytic
applications. 相似文献
94.
Camila Fabiano de Freitas Diogo Silva Pellosi Bianca Martins Estevão Italo Rodrigo Calori Tayana Mazin Tsubone Mário José Politi Wilker Caetano Noboru Hioka 《Photochemistry and photobiology》2016,92(6):790-799
It was evaluated the properties of the xanthene dyes Erythrosin B, Eosin Y and theirs Methyl, Butyl and Decyl ester derivatives as possible photosensitizers (PS) for photodynamic treatments. The more hydrophobic dyes self‐aggregate in water/ethanol solutions above 70% water (vol/vol) in the mixture. In buffered water, these PS were encapsulated in Pluronic polymeric surfactants of P‐123 and F‐127 by two methodologies: direct addition and the thin‐film solid dispersion methods. The thin‐film solid method provided formulations with higher stabilities besides effective encapsulation of the PS as monomers. Size measurements demonstrated that Pluronic forms self‐assembled micelles with uniform size, which present slightly negative surface potential and a spherical form detected by TEM microscopy. The ester length modulates xanthene localization in the micelle, which is deeper with the increase in the alkyl chain. Moreover, some PS are distributed into two populations: one on the corona micelle interface shell (PEO layer) and the other into the core (PPO region). Although all PS formulations show high singlet oxygen quantum yield, promising results were obtained for Erythrosin B esters with the hydrophobic P‐123, which ensures their potential as drug for clinical photodynamic applications. 相似文献
95.
Fattori N Maroneze CM da Costa LP Strauss M Sigoli FA Mazali IO Gushikem Y 《Langmuir : the ACS journal of surfaces and colloids》2012,28(27):10281-10288
Imidazolium groups were successfully prepared and grafted on the surface of SBA-15 mesoporous silica. The ion-exchange properties of the functionalized porous solid (SBA-15/R(+)Cl(-)) toward AuCl(4)(-) anions were evaluated through an ion-exchange isotherm. The calculated values of the equilibrium constant (log β = 4.47) and the effective ion-exchange capacity (t(Q) = 0.79 mmol g(-1)) indicate that the AuCl(4)(-) species can be loaded and strongly retained on the functionalized surface as counterions of the imidazolium groups. Subsequently, solids containing different amounts of AuCl(4)(-) ions were submitted to a chemical reduction process with NaBH(4), converting the anionic gold species into supported gold nanoparticles. The plasmon resonance bands, the X-ray diffraction patterns, and transmission electron microscopy images of the supported gold nanoparticles before and after thermal treatment at 973 K indicate that the metal nanostructures are highly dispersed and stabilized by the host environment. 相似文献
96.
Fleming GD Golsio I Aracena A Celis F Vera L Koch R Campos-Vallette M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):1074-1079
The SERS modelling of o-, m-, and p-methoxybenzonitrile has been performed following the same methodology that in Part I. Optimized structure obtained from DFT calculations in a B3LYP-LANL2DZ level of calculation shows different tilted positions for the isomers under study. From correlations obtained by comparison of Raman and SERS spectra concerning geometrical parameters, frequency shifting, change in band intensity, and force constants is possible to give insight about the different effect of the metal surface on these molecules and the structural reasons of this behaviour. Frontier orbital analysis gives further information and reveals a ligand to metal charge transfer mechanism for all isomers, as well as its relative importance. 相似文献
97.
Summary In this paper, we discuss an approach to the obstacle problem for minimal boundaries via penalty techniques. After investigating some classes of penalized problems, a general method is introduced, based on the minimization of a suitable functional containing an extra term related to the mean curvature of the given obstacle. 相似文献
98.
E. Marin F. Boschetto M. Zanocco T. Adachi N. Toyama W. Zhu B.J. McEntire R.M. Bock B.S. Bal G. Pezzotti 《Materials Today Chemistry》2020
Poly-Ether-Ether-Ketone (PEEK) is a structural biopolymer with various biomedical applications, from spinal cages to dental prosthetics. Due its high chemical stability combined with good mechanical strength, PEEK is considered to be one of the most successful bio-inert polymers ever developed. In this work, a mixture of PEEK and β-Si3N4 was used to produce a composite material which combined the mechanical properties of the polymer with the bioactive effects of a reinforcing ceramic, in particular its good osteoconductivity. When tested with KUSA-A1 mesenchymal cells, the composite material resulted in a higher production of bone tissue when compared to standard PEEK or biomedical titanium alloy. On the other hand, the composite showed poor osteogenic differentiation as evaluated by ALP. Tests performed using various spectroscopic techniques showed that the bone tissue formed has a balanced mineral-to-matrix ratio, similar to that of healthy bone tissue. 相似文献
99.
Leandro F. Pinto Diogo Italo Segalen da Silva Fabiano Rosa da Silva Luiz P. Ramos Papa M. Ndiaye Marcos L. Corazza 《The Journal of chemical thermodynamics》2012,44(1):57-65
The main objective of this work was to investigate the high pressure phase behavior of the binary systems {CO2(1) + methanol(2)} and {CO2(1) + soybean methyl esters (biodiesel)(2)} and the ternary system {CO2(1) + biodiesel(2) + methanol(3)} were determined. Biodiesel was produced from soybean oil, purified, characterized and used in this work. The static synthetic method, using a variable-volume view cell, was employed to obtain the experimental data in the temperature range of (303.15 to 343.15) K and pressures up to 21 MPa. The mole fractions of carbon dioxide were varied according to the systems as follows: (0.2383 to 0.8666) for the binary system {CO2(1) + methanol(2)}; (0.4201 to 0.9931) for the binary system {CO2(1) + biodiesel(2)}; (0.4864 to 0.9767) for the ternary system {CO2(1) + biodiesel(2) + methanol(3)} with a biodiesel to methanol molar ratio of (1:3); and (0.3732 to 0.9630) for the system {CO2 + biodiesel + methanol} with a biodiesel to methanol molar ratio of (8:1). For these systems, (vapor + liquid), (liquid + liquid), (vapor + liquid + liquid) transitions were observed. The phase equilibrium data obtained for the systems were modeled using the Peng–Robinson equation of state with the classical van der Waals (PR-vdW2) and Wong-Sandler (PR–WS) mixing rules. Both thermodynamic models were able to satisfactorily correlate the phase behavior of the systems investigated and the PR–WS presented the best performance. 相似文献
100.
Jean Bellissard Italo Guarneri Hermann Schulz-Baldes 《Communications in Mathematical Physics》2002,227(3):515-539
For a class of discrete quasi-periodic Schr?dinger operators defined by covariant representations of the rotation algebra,
a lower bound on phase-averaged transport in terms of the multifractal dimensions of the density of states is proven. This
result is established under a Diophantine condition on the incommensuration parameter. The relevant class of operators is
distinguished by invariance with respect to symmetry automorphisms of the rotation algebra. It includes the critical Harper
(almost-Mathieu) operator. As a by-product, a new solution of the frame problem associated with Weyl–Heisenberg–Gabor lattices
of coherent states is given.
Received: 30 May 2001 / Accepted: 2 January 2002 相似文献