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91.
Angela Cardelli Lucia Ricci Giacomo Ruggeri Silvia Borsacchi Marco Geppi 《European Polymer Journal》2011,(8):1589-1600
A micrometric silica modified with perylene derivative (SiO2–TES) has been prepared by hydrolysis–condensation reactions between silica and N,N’-bis-(3-triethoxysilylpropyl)-perylene-tetracarboxyldiimide (P-TES) and utilized as filler in LLDPE films together with a compatibilizer. Spectroscopic analyses on SiO2–TES confirmed the grafting of P-TES on silica, while its amount was determined by thermogravimetric analysis. Solid state NMR provided information about the structure of silicon atoms involved in the condensation of SiO2 and P-TES that resulted mainly in silicon atoms grafted with bi-dentate anchorages.UV–Vis and fluorescence analyses carried out on P-TES showed the ability of the dye to generate J-type aggregates in apolar solvents. The same analyses on SiO2–TES revealed the presence of both isolated and aggregated dye molecules grafted on silica surface, while on polymeric dispersions of SiO2–TES, they have shown only the presence of P-TES aggregates grafted to silica.Thanks to the direct correlation between optical properties (obtained both by UV–Vis and by fluorescence analyses) and the chemical environment of composites, the luminescent silica SiO2–TES could be used to estimate the filler dispersion extent in different microcomposite polymer materials. 相似文献
92.
Pedone A Prampolini G Monti S Barone V 《Physical chemistry chemical physics : PCCP》2011,13(37):16689-16697
A multi-scale computational protocol, which combines Quantum Mechanics and Molecular Mechanics (QM/MM) calculations with the polarisable continuum model (PCM), has been used to study the tetramethylrhodamine isothiocyanate (TRITC) fluorophore, embedded in three different environments, namely in water, on an amorphous silica surface and covalently encapsulated in a silica nanoparticle (C dot). Absorption and emission spectra have been simulated by using TD-B3LYP/PCM calculations, performed on the TRITC ground and excited state geometries, optimized at the QM/MM level. The results are in good agreement with experimental data confirming the caging effect played by the silica shell on the mobility of the TRITC molecule when covalently encapsulated in silica nanoparticles. This could result in a decrease of the nonradiative decay rate and thus an increase of the quantum yield of the molecule. 相似文献
93.
Barone V Bloino J Monti S Pedone A Prampolini G 《Physical chemistry chemical physics : PCCP》2011,13(6):2160-2166
Classical all-atom molecular dynamics (MD) simulations and quantum mechanical (QM) time-dependent density functional theory (TD-DFT) calculations are employed to study the conformational and photophysical properties of the first emitter excited state of tetramethyl-rhodamine iso-thiocyanate fluorophore in aqueous solution. For this purpose, a specific and accurate force field has been parameterised from QM data to model the fluorophore's first bright excited state. During the MD simulations, the consequences of the π→π* electronic transition on the structure and microsolvation sphere of the dye has been analysed in some detail and compared to the ground state behaviour. Thereafter, fluorescence has been calculated at the TD-DFT level on configurations sampled from the simulated MD trajectories, allowing us to include time dependent solvent effects in the computed emission spectrum. The latter, when compared with the absorption spectrum, reproduces well the experimental Stokes shift, further validating the proposed multilevel computational procedure. 相似文献
94.
Caruso R Gambino GL Scordino M Sabatino L Traulo P Gagliano G 《Natural product communications》2011,6(12):1939-1943
The influence of the wine distillation process on methanol content has been determined by quantitative analysis using gas chromatographic flame ionization (GC-FID) detection. A comparative study between direct injection of diluted wine and injection of distilled wine was performed. The distillation process does not affect methanol quantification in wines in proportions higher than 10%. While quantification performed on distilled samples gives more reliable results, a screening method for wine injection after a 1:5 water dilution could be employed. The proposed technique was found to be a compromise between the time consuming distillation process and direct wine injection. In the studied calibration range, the stability of the volatile compounds in the reference solution is concentration-dependent. The stability is higher in the less concentrated reference solution. To shorten the operation time, a stronger temperature ramp and carrier flow rate was employed. With these conditions, helium consumption and column thermal stress were increased. However, detection limits, calibration limits, and analytical method performances are not affected substantially by changing from normal to forced GC conditions. Statistical data evaluation were made using both ordinary (OLS) and bivariate least squares (BLS) calibration models. Further confirmation was obtained that limit of detection (LOD) values, calculated according to the 3sigma approach, are lower than the respective Hubaux-Vos (H-V) calculation method. H-V LOD depends upon background noise, calibration parameters and the number of reference standard solutions employed in producing the calibration curve. These remarks are confirmed by both calibration models used. 相似文献
95.
To prevent damage caused by accidental overpressure inside a closed duct (e.g. jet engine) safety valves are introduced. The
present study experimentally investigates the dynamic opening of such valves by employing a door at the end of a shock tube
driven section. The door is hung on an axis and is free to rotate, thereby opening the tube. The evolved flow and wave pattern
due to a collision of an incident shock wave with the door, causing the door opening, is studied by employing a high speed
schlieren system and recording pressures at different places inside the tube as well as on the rotating door. Analyzing this
data sheds light on the air flow evolution and the behavior of the opening door. In the present work, emphasis is given to
understanding the complex, unsteady flow developed behind the transmitted shock wave as it diffracts over the opening door.
It is shown that both the door inertia and the shock wave strength influence the opening dynamic evolution, but not in the
proportions that might be expected. 相似文献
96.
Maria C. Mariani Indranil SenGupta 《Nonlinear Analysis: Real World Applications》2011,12(6):3103-3113
We study an integro-differential parabolic problem modeling a process with jumps arising in financial mathematics. Under suitable conditions, we prove the existence of weak solutions to a more general integro-differential equation by using the Schaefer’s fixed point theorem and generalize the result to unbounded domains. 相似文献
97.
98.
99.
We give conditions onH, a continuous and bounded real function inR
3, to obtain at least two solutions for the problem (Dir) below.H can be far from being constant in the sense of [9]. Our motivation is a better understanding of the Plateau problem for the
prescribed mean curvature equation. 相似文献
100.
G. Bossi B. Dubini P. Mariani M. G. Ponzi Bossi F. Rustichelli R. S. Phadke 《Il Nuovo Cimento D》1990,12(9):1293-1308
Summary We report a thermodynamical and structural investigation on the effect of a dicarboxylic acid, the azelaic acid, on a synthetic
phosophatidylcholine in excess water condition. The results indicate that the drug interacts with the lipid headgroup region,
near to the hydrocarbon chains: in particular, at higher concentrations investigated, an interdigitated ?gel phase?, with
rigid chains, stiff and perpendicular to the lamellar planes, is induced. The experimental electron density profiles, obtained
for samples containing low and high quantity of azelaic acid, support the proposed interaction. Moreover, step electron density
models, used to confirm the selected sign combination of the observed structure factors, show the best agreement with the
experimental data when the chain terminal methyl groups are frozen in fixed position.
Work presented at the second USSR-Italy Bilateral Meeting on Liquid Crystals held in Moscow, September 15–21, 1988. 相似文献