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排序方式: 共有132条查询结果,搜索用时 328 毫秒
41.
When filtering through a wall with constant averaging radius, in addition to the subfilter scale stresses, a non-closed commutator term arises. We consider a proposal of Das and Moser to close the commutator error term by embedding it in an optimization problem. This report shows that this optimization-based closure, with a small modification, leads to a well-posed problem showing the existence of a minimizer. We also derive the associated first order optimality conditions. 相似文献
42.
A new self-assembled multilayer architecture was constructed by successive deposition of poly(4-vinylpyridine) partially quaternized
with ethylamine (B) and Keggin trilacunary polyoxomolybdate [Aα-PFe3III(H2O)3Mo9O37]6− (PFe3Mo9) on the Au electrode surface, covered with 3-mercapto-1-propanesulfonic acid (MPS). Surface plasmon resonance and cyclic
voltammetry measurements were performed at Au/MPS/B/PFe3Mo9/B interface in order to investigate the structure and the electrochemical behavior of this electrode. Due to the presence
of PFe3Mo9, the Au/MPS/B/PFe3Mo9/B-modified electrode showed electrocatalytic activity towards H2O2 amperometric detection. Additionally, when GOx was deposited as the outermost layer on the abovementioned multilayer structure,
the Au/MPS/B/PFe3Mo9/B/GOx-modified electrode was able to detect glucose. 相似文献
43.
Mixtures of the monohydroxy alcohol n-butanol with n-bromobutane are investigated via dielectric and nuclear magnetic resonance (NMR) techniques. Static- and pulsed-field gradient proton NMR yielded self-diffusion coefficients as a function of concentration and temperature. To monitor reorientational motions, broadband dielectric and (13)C-spin relaxation time measurements were carried out. The latter demonstrate that the structural relaxation stems from the motion of the alkyl chains. By combining data from translational diffusion coefficients with published shear viscosities, hydrodynamic radii were determined that compare favorably with the van der Waals radii of single molecules. The results for the neat alcohol and for the binary mixtures are discussed with respect to a recent transient chain model. The approach of Debye and structural relaxation times at high temperatures, identified as a general feature of monohydroxy alcohols, is also discussed within that framework. 相似文献
44.
Dan Donescu Raluca Somoghi Catalin Ilie Spataru Doina Manaila-Maximean Denis Mihaela Panaitescu Eugeniu Vasile Cristina L. Nistor 《Colloid and polymer science》2013,291(10):2345-2358
The work describes a study for preparing polystyrene (PSt) and polymethyl methacrylate (PMMA) latex, containing magnetite (Fe3O4), covalently bounded to the polymeric chains. The magnetite was functionalized with various alkoxysilanes containing double bonds: vinyltriethoxysilane (VTES), methacryloyl propyl trimethoxysilane (MPTS) and vinyldimethylethoxysilane (VMe2TES). The ferrite-silane composite forms higher average size particles with MPTS than with VTES. Ferrite functionalized with VMe2TES forms stable latexes with both PSt and PMMA polymers. PSt forms also stable latexes with ferrite functionalized with VTES but unstable with ferrite functionalized with MPTS. 相似文献
45.
Catalin Ilie Spataru Violeta Purcar Marius Ghiurea Constantin Radovici Gabriela Stanga Dan Donescu 《Journal of Sol-Gel Science and Technology》2013,65(3):344-352
Modifications to the refractive indices of meso-structured organic–inorganic films caused by variations in the mole fraction of precursors in ethanolic solutions were investigated. The refractive indices were dependent on the mole fraction of C16TMS (hexadecyltrimethoxysilane) and of the C16TMS/TMOS (tetramethoxysilane) (1/1) mixture in ethanol. The dependency was determined to be nonlinear, and the phenomenon was attributed to self-assembly caused by the long alkyl groups (C16) on the C16TMS. Changes in the maximum decreasing rate of dn/dx values [(dn/dx)max—for dn/dx estimation, the curves from Fig. 1 were associated with a polynomial; using a dedicated program, dn/dx was calculated; maximum values of dn/dx were taken into account and were included in Table 1)] were used to distinguish the behavior of alcoholic precursor mixtures. In the case of using pyrene as a fluorescent probe, the ratio between two peaks from the pyrene emission spectra (I1/I3) strongly decreased as hydrophobic micro-surroundings formed due to the self-assembly process. The UV–VIS spectra of a cationic dye solution, R6G, was studied because dilute solutions of the dye in equilibrium form measurable ratios of dimers and monomers. The absorbance was modified as micro-surroundings with different polarities were formed. These three methods demonstrated that nano-structuration was present prior to the occurrence of the sol–gel process. The combination of C16TMS with other alkyltrialkoxysilane precursors having hydrocarbon chain lengths between C1 and C8 provided further evidence for a nonlinear dependence of the refractive indice and fluorescence spectra of pyrene. The properties of the final hybrids obtained by the sol–gel process were significantly affected by the precursor hydrocarbon chain lengths. DSC, XRD and FTIR measurements were used to show the plasticizing phenomena of C16 as other alkyltrialkoxysilanes (i.e., C1–C8) were added. Fig. 1
Variation of the refractive index with the mole fraction of the precursor mixtures 相似文献
46.
Florica Papa Catalin Negrila Akane Miyazaki Ioan Balint 《Journal of nanoparticle research》2011,13(10):5057-5064
Well-dispersed, uniform monometallic Pt and bimetallic Pt–Cu, and Pt–Ag nanoparticles protected with PVP have been synthesized
by a modified-protocol alkaline polyol method. The nanoparticles were characterized by various methods (TEM, XPS, and XRD)
to elucidate the relationship between morphology and preparation variables. The average of monodispersed nanoparticles ranged
between 4.1 and 4.9 nm. Core–shell structure was obtained in the case of bimetallic nanoparticles. The core of bimetallic
nanoparticles was found to be rich in platinum, whereas the shell contained mostly copper or silver. The final structure of
bimetallic nanoparticles was found to be determined by the morphology particles resulted in the first reduction step. Explanations
are advanced on the light of experimental results. 相似文献
47.
Catalin Croitoru Silvia PatachiaNicolae Cretu Attila BoerChristian Friedrich 《Applied Surface Science》2011,257(14):6220-6225
In this paper, the influence of four types of imidazolium-based ionic liquids (ILs) on the surface properties of common aspen (Populus tremula) veneers has been studied by using contact angle, electrical conductivity and Fourier transform infrared spectroscopy analysis. The measurements showed that wood wettabillity is increased by IL treatment. The electrical conductivities of treated wood were in the 0.5-1 mS/cm range, higher than the ones reported in the reference literature. It has been determined that the ILs decrease the crystallinity and improve the flexibility of the cellulose matrix. It has been determined by photographic image analysis that the surface roughness of the IL treated veneers decreases in comparison with the untreated samples. 相似文献
48.
Adrian Eugen Rosca Mara Ioana Iesanu Carmen Denise Mihaela Zahiu Suzana Elena Voiculescu Alexandru Catalin Paslaru Ana-Maria Zagrean 《Molecules (Basel, Switzerland)》2020,25(23)
Capsaicin is a widespread spice known for its analgesic qualities. Although a comprehensive body of evidence suggests pleiotropic benefits of capsaicin, including anti-inflammatory, antioxidant, anti-proliferative, metabolic, or cardioprotective effects, it is frequently avoided due to reported digestive side-effects. As the gut bacterial profile is strongly linked to diet and capsaicin displays modulatory effects on gut microbiota, a new hypothesis has recently emerged about its possible applicability against widespread pathologies, such as metabolic and inflammatory diseases. The present review explores the capsaicin–microbiota crosstalk and capsaicin effect on dysbiosis, and illustrates the intimate mechanisms that underlie its action in preventing the onset or development of pathologies like obesity, diabetes, or inflammatory bowel diseases. A possible antimicrobial property of capsaicin, mediated by the beneficial alteration of microbiota, is also discussed. However, as data are coming mostly from experimental models, caution is needed in translating these findings to humans. 相似文献
49.
We show that a stochastic heat equation with multiplicative noise on a bounded domain can be stabilized by a control acting only on a subdomain if is sufficiently ‘thin’. We consider both linear and semilinear stochastic heat equations. To cite this article: V. Barbu et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 311–316. 相似文献
50.
Zwaneveld NA Pawlak R Abel M Catalin D Gigmes D Bertin D Porte L 《Journal of the American Chemical Society》2008,130(21):6678-6679
The development of nanoscale masking for particle deposition is exceedingly important to push the future of nanoelectronics beyond the current limits of lithography. We present the first example of ordered hexagonal covalent nanoporous structures deposited in extended arrays of near monolayer coverage across a Ag(111) surface. The networks were formed from the deposition of the reagents from a heated molybdenum crucible between 370 and 460 K under ultrahigh vacuum (UHV) onto a cleaned Ag(111) substrate and imaged using a scanning tunneling microscope (STM). Two surface covalent organic frameworks (SCOFs) are presented; the first is formed from the deposition of 1,4-benzenediboronic acid (BDBA) and its dehydration to form the boroxine-linked SCOF-1, the second is formed from the co-deposition of BDBA and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to form a dioxaborole-linked SCOF-2 network. The networks were found to produce nanoporous structures of 15 A for SCOF-1 and 29 A for SCOF-2, which agreed with theoretical pore sizes determined from DFT calculations. Both SCOFs were found to have exceptional thermal stability, maintaining their structure until approximately 750 K, which was found to be the polymer degradation temperature from thermal gravimetric analysis (TGA). 相似文献